Tesi sul tema "Aeronautic emissions"

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 132-159).
Millions of deaths worldwide are attributed annually to exposure degraded surface air quality and UV-induced skin cancer. However, the focus has been on surface emissions, and the contribution of high altitude emissions to these issues is rarely examined. In this thesis, potential links are investigated between high altitude emissions and damages or benefits to human health via photochemical effects. Changes in population exposure to fine particulate matter, ozone and UV-B radiation resulting from current and future high altitude emissions are calculated, applying epidemiologically-derived impact functions to estimate resultant mortality and morbidity. A stratospheric extension is developed for the widely-used tropospheric model GEOS-Chem, which has been shown to accurately model tropospheric conditions and used in simulations of remote and urban pollution. This extended model, the GEOS-Chem UCX, can propagate a stratospheric perturbation through to a tropospheric impact, including shortwave UV fluxes, long-lived species, stratospheric water chemistry and high altitude aerosols. This model is employed to estimate the impacts of reversing 1 K of global warming using stratospheric sulfate aerosol injection. In total, it is projected that 85,000 additional premature mortalities would occur in 2040 due to particulate matter exposure, but that reduced ozone loading would prevent 64,000 mortalities worldwide. Aerosol injection also results in a 5.7% reduction in the global ozone column and a 3.0% increase in surface UV-B, which could cause 3,700 additional melanoma mortalities per year. By comparison, surface air quality and UV-B impacts due to aviation emissions are found to have resulted in 16,000 premature mortalities globally in 2006, of which 450 occurred in North America. Ozone exposure contributes 43% of this total. The increase in tropospheric ozone due to aviation emissions is found to have prevented 390 skin cancer mortalities in 2006. This thesis quantifies the photochemical mechanisms connecting future and proposed high altitude emissions schemes to human health impacts and provides an estimate of mortality and morbidity attributable to aviation and sulfate aerosol injection.
by Sebastian D. Eastham.
Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 47-50).
Aviation NO[subscript x] emissions have an impact on air quality and climate change, where the latter is magnified due to the higher sensitivity of the upper troposphere and lower stratosphere. In the aviation industry, efforts to increase the efficiency of propulsion systems are giving rise to higher overall pressure ratios which results in higher NO[subscript x] emissions due to increased combustion temperatures. This thesis identifies that the trend towards smaller engine cores (gas generators) that are power dense and contribute little to the thrust output presents new opportunities for emissions control that were previously unthinkable when the core exhaust stream contributed significant thrust. This thesis proposes and assesses selective catalytic reduction (SCR), which is a post-combustion emissions control method used in ground-based sources such as power generation and heavy-duty diesel engines, for use in aero-gas turbines.
The SCR system increases aircraft weight and introduces a pressure drop in the core stream. The effects of these are evaluated using representative engine cycle models provided by a major aero-gas turbine manufacturer. This thesis finds that employing an ammonia-based SCR can achieve close to 95% reduction in NO[subscript x] emissions for ~0.4% increase in block fuel burn. The large size of the catalyst needs to be housed in the body of the aircraft and hence would be suitable for future designs where the engine core is also within the fuselage, such as would be possible with turbo-electric or hybrid-electric designs. The performance of the post-combustion emissions control is shown to improve for smaller core engines in new aircraft in the NASA N+3 time-line (2030-2035), suggesting the potential to further decrease the cost of the ~95% NO[subscript x] reduction to below ~0.4% fuel burn.
Using a global chemistry and transport model (GEOS-Chem) this thesis estimates that using ultra-low sulfur (<15 ppm fuel sulfur content) in tandem with post-combustion emissions control results in a ~92% reduction in annual average population exposure to PM₂.₅ and a ~95% reduction in population exposure to ozone. This averts approximately 93% of the air pollution impact of aviation.
by Prakash Prashanth.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.
Includes bibliographical references (p. 103-105).
In this thesis, a physics-based model of an aircraft gas turbine combustor is developed for predicting NO. and CO emissions. The objective of the model is to predict the emissions of current and potential future gas turbine engines within quantified uncertainty bounds for the purpose of assessing design tradeoffs and interdependencies in a policy-making setting. The approach taken is to capture the physical relationships among operating conditions, combustor design parameters, and pollutant emissions. The model is developed using only high-level combustor design parameters and ideal reactors. The predictive capability of the model is assessed by comparing model estimates of NO, and CO emissions from five different industry combustors to certification data. The model developed in this work correctly captures the physical relationships between engine operating conditions, combustor design parameters, and NO. and CO emissions. The NO. estimates are as good as, or better than, the NO. estimates from an established empirical model; and the CO estimates are within the uncertainty in the certification data at most of the important low power operating conditions.
by Douglas L. Allaire.
S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 109-115).
Combustion engines emit precursors of ne particulate matter (PM) into the atmosphere. Numerous gaseous species, soot particles, and liquid aerosols in the aircraft exhaust are involved in PM formation, and these very ne, nanometer-size particles potentially have signicant impacts on climate, human health, and air quality. In particular, the organic content of the particles is important to determine physical and chemical properties of PM and consequently their potential impacts on the environment. The main objective of this thesis is to understand the role of organic compounds in PM evolution by developing a microphysical model that incorporates organic compounds into the formation mechanism of binary aqueous aerosols. While binary aerosol models with sulfuric acid and water have been widely studied, the understanding of the effect of organics on the formation and growth of aerosols is still insufficient. This work demonstrates important interactions and competitions in the formation of multi-component aerosols with organic compounds, sulfuric acid, and water in aircraft emissions. Hydrocarbon-containing aerosols have been identied as a major component of ground-level aircraft emission, especially at low power operations. This thesis describes selected surrogates of organic species and introduces estimation techniques for their thermophysical properties. The surrogates of organic species include water-insoluble hydrocarbons and water-soluble oxygenated hydrocarbons. Simulation results suggest that certain hydrocarbon compounds play an important role in the formation of aviation aerosol with interactions with both homogeneous sulfuric acidwater aerosols and soot particles in the organic-rich aircraft plume. Hydrocarbons contribute to the growth of existing homogeneous liquid particles, whereas their contribution to aerosol number density is negligible compared to that of sulfuric acid and water, which largely determine the formation of homogeneous aerosols. Also, low volatility hydrocarbons (e.g., benzopyrene, coronene) are observed to be partitioned into soot particles and induce competition with the uptake of water-soluble species, while light water-soluble oxygenated hydrocarbons enhance the uptake of water and sulfuric acid on soot particles.
by Mina Jun.
Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 99-103).
With commercial aviation continuing to grow and environmental policymaking activity intensifying, it is becoming increasingly necessary to assess the environmental impact of measures that result in changes in aviation fuel bum levels. For estimating air quality and climate impacts, it is important to employ a multi-gas approach that accounts for the effects of all emitted species, not just carbon dioxide (CO₂). The main objective of this thesis is to develop a simplified framework for monetizing the CO₂ and non-CO₂ co-benefits of aviation fuel and emissions reductions. The approach is based on two main pieces, both of which are derived using the Aviation environmental Portfolio Management Tool (APMT). First, the air quality marginal damage cost of a unit of fuel is estimated using an air quality response surface model. Second, a simplified probabilistic impulse response function model for climate is employed to derive a non-CO₂/CO₂ impact ratio that can be multiplied by a social cost of carbon to estimate the additional benefits of fuel bum reductions from aviation beyond those associated with CO2 alone. The sensitivity of the non-CO₂/CO₂ climate ratio to metric choice, scientific assumptions, background scenarios, and other policymaker choices is explored. Notably, it is found that given the large uncertainties in short-lived effects, the choice of metric is not particularly influential on the overall ratio value (that is, similar results-within the range of uncertainty-are found for the different metrics considered). This thesis also validates the use of the climate ratios and air quality marginal damages through two sample applications. The first study explores the impact of various aviation growth scenarios and demonstrates the applicability of this framework to a multi-year analysis. The second study concerns the introduction of an advanced aircraft concept into the present-day aviation fleet and demonstrates the ability of the climate ratios to capture scientific and valuation-based uncertainties. In both cases, the derived ratios and air quality damage costs are found to be a good surrogate for a full impact analysis in APMT, relative to the overall uncertainty in estimating impacts.
by Christopher S. Dorbian.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000.
Includes bibliographical references (p. 141-144).
Air travel is continuing to experience the fastest growth among all modes of transport. Increasing total fuel consumption and the potential impacts of aircraft engine emissions on the global atmosphere have motivated the industry, scientific community, and international governments to seek various emissions reduction options. Despite the efforts to understand and mitigate the impacts of aviation emissions, it still remains uncertain whether proposed emissions reduction options are technologically and financially feasible. This thesis is the first of its kind to analyze the relationship between aircraft performance and cost, and assess aviation emissions reduction potential based on analytical and statistical models founded on a database of historical data. Technological and operational influences on aircraft fuel efficiency were first quantified utilizing the Breguet range equation. An aviation system efficiency parameter was defined, which accounts for fuel efficiency and load factor. This parameter was then correlated with direct operating cost through multivariable statistical analysis. Finally, the influence of direct operating cost on aircraft price was statistically determined. By comparing extrapolations of historical trends in aircraft technology and operations with future projections in the open literature, the fuel burn reduction potential for future aircraft systems was estimated. The economic characteristics of future aircraft systems were then determined by utilizing the technology-cost relationship developed in the thesis. Although overall system efficiency is expected to improve at a rate of 1.7% per year, it is not sufficient to counter the projected annual 4 to 6% growth in demand for air transport. Therefore, the impacts of aviation emissions on the global atmosphere are expected to continue to grow. Various policy options for aviation emissions reduction and their potential effectiveness are also discussed.
by Joosung Loseph Lee.
S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005.
Includes bibliographical references (p. 131-134).
(cont.) fuel burn results below 3000 ft. For emissions, the emissions indices were the most influential uncertainties for the variance in model outputs. By employing the model, this thesis examined three policy options for mitigating aviation emissions. More stringent engine certification standards, continuous descent approach procedures, and derated take-off procedures were analyzed. Uncertainties of the model were carefully accounted for in the fuel burn and emissions scenarios of the policy options. The considered policy options achieved roughly 10-30% reductions in NOx emissions. However, HC and CO emissions rather increased due to higher emissions production rate for the CDA and derated take-off. In addition, the NOx emissions reductions in some cases were not statistically significant given the uncertainty in the modeling tool.
Air travel continues to experience fast growth. Although the energy intensity of the air transport system continues to improve, aviation fuel use and emissions of many pollutants have risen. This thesis focuses on developing, assessing and applying a system model to evaluate global aircraft fuel consumption and emissions, and to examine technological and operational measures to mitigate these emissions. The model is capable of computing how much emissions are produced on a flight-by-flight, fleet and global basis and where in the atmosphere the emissions are deposited. These are important questions for aviation environmental policy-making. Model development was followed by a comprehensive uncertainty analysis. It involved comparisons of reported versus modeled results at both the modular and system levels. On average, the aggregate-level composite fuel burn results showed about -6% difference from reported fuel burn data. A statistical analysis showed that this mean shift was a combined contribution of the key uncertainties in aircraft performance and operations. A parametric study followed to rank-order the effects that the key modeling uncertainties had on estimates of fuel burn and emissions. Statistical methods were developed to analyze both the random and systematic errors of the modeling tools. The analyses showed that the uncertainties in engine and aerodynamic performance had the largest impact on system errors, accounting for around 60-70% of the total variance in full-mission fuel burn results. The uncertainties in winds aloft and take-off weight explained another 20-25%. LTO procedures, which consist of engine throttle setting, rate of climb/descent and flight speed, were the most influential uncertainties that drove the variance in
by Joosung Joseph Lee.
Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 127-149).
Combustion emissions impact the environment through chemical and transport processes that span varying temporal and spatial scales. Numerical simulation of the effects of combustion emissions and potential corresponding mitigation approaches is computationally expensive. Atmospheric adjoint modeling enables the calculation of receptor-oriented sensitivities of environmental metrics of interest to emissions, overcoming the numerical cost of conventional modeling. This thesis applies and further develops an existing adjoint of a chemistry-transport model to perform three evaluations, where the high number of inputs (due to the nature of the problem or the associated uncertainty) prevented comprehensive assessment in the past. First, this thesis quantifies the pollution exchange between the US states for seven major anthropogenic combustion emissions sectors: electric power generation, industry, commercial/residential, aviation, as well as road, marine, and rail transportation. This thesis presents the state-level fine particulate matter (PM₂.₅) early death impacts of combustion emissions in the US for 2005, 2011 and 2018 (forecast), and how these are driven by sector, chemical species, and location of emission. Results indicate major shifts in the chemical species and sectors that cause most early deaths, and opportunities for further improving air quality in the US. Second, this thesis quantifies how changes in emissions impact the marginal atmospheric PM₂.₅ response to emissions perturbations. State-level annual adjoint sensitivities of PM₂.₅ population exposure to precursor emissions are compared for the years of 2006 and 2011, and correlated with the magnitude of emissions reduction and the background ammonia mixing ratio. Third, this thesis presents the development and evaluation of the discrete adjoint of the GEOS-Chem unified tropospheric-stratospheric chemistry extension (UCX), which enables the calculation of stratospheric sensitivities and the examination of the entire design space of high altitude emissions impacts. To illustrate its potential, sensitivities of stratospheric ozone to precursor species are calculated. This development expands the span of atmospheric chemistry-transport questions (including inversions) that this open-source model can be used to answer. The assessments performed in this thesis span spatial scales from the regional to the global and demonstrate the ability of this approach to provide information on both bottom-up and top-down mitigation approaches.
by Irene Constantina Dedoussi.
Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-60).
Aviation biofuels derived from biomass and wastes have been identified as a means to reduce carbon dioxide (CO₂) emissions from US aviation, but the magnitude of the possible reduction has not been quantified. This scenario-based analysis quantifies the life cycle greenhouse gas (GHG) mitigation potential of aviation biofuels in 2050 within the US. Projected arable land availability, growth in agricultural yields, and the availability of wastes and residues are estimated as a function of future economic and climate patterns, and variability is accounted for. Under a baseline set of assumptions, the use of aviation biofuels results in a maximum reduction of 163 Tg of CO₂ equivalent (CO₂e) in 2050, a 42% reduction in life cycle GHG emissions compared to petroleum-derived jet fuel. Across all scenarios assessed, the reduction in life cycle GHGs ranges from 47.0 to 207 Tg CO₂e (12-53%), requiring the use of fuels derived from wastes, agriculture and forestry residues, and cultivated energy crops. Using only fuels derived from residues and wastes, up to 35% of US jet fuel demand could be met, corresponding to a 28% reduction of CO₂e. The results are most sensitive to assumptions on the distribution of fuel products, and agricultural residue availability.
by Timothy R. Galligan.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

The following research thesis focuses on methods of controlling nitrogen oxides (NO_x) and particulate matter (PM) emissions emitted from a low temperature diesel exhaust. This involves studying the influence of hydrogen (H₂) on various aftertreatment devices such as hydrocarbon selective catalytic reduction (HC-SCR) over silver-alumina (Ag-Al₂O₃) catalysts for lean NO_x reduction, platinum diesel oxidation catalysts (DOC) for nitrogen dioxide (NO₂) production and passive regeneration methods for the diesel particulate filter (DPF). H₂ was implemented on-board either through diesel exhaust gas fuel reforming or via the simulation of ammonia (NH₃) dissociation. Both methods showed to be very effective in enhancing the activity of a silver HC-SCR catalyst for the reduction of NO_x with conversions reaching 90% with the aid of an upstream DPF. A combined DOC and catalysed DPF (cDPF) configuration proved promising for passive regeneration in the presence of reformed exhaust gas recirculation (REGR). The addition of H₂ over the DOC led to an improved catalyst light-off temperature and increased rate of oxidation for NO₂ production. Implementing filtered EGR (FEGR) removes the hydrocarbon (HC) and soot recirculation penalty, thus minimising particulate growth which results in a significantly reduced engine-out soot emission during exhaust gas recirculation (EGR) and hence, an improved NO_x/soot ratio. Introducing fuel components which enhance the cetane number and oxygenate the diesel fuel allow better control of the NO_x/soot trade-off with improved soot oxidation properties.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 104-112).
The rapid growth of aviation is critical to the world and US economy, and it faces several important challenges among which lie the environmental impacts of aviation on noise, climate and air quality. The first objective of this thesis addresses the requirements of section 753 of the US Energy Policy Act, and entails the quantification of present and future-year regional air quality impacts of US Landing and Take-Off (LTO) aviation emissions. In addition, this thesis characterizes the sensitivity of these impacts to variations in the projection of non-aviation anthropogenic emissions (referred to as background emissions). Finally, the implication of a future-year background emissions scenario on the current policy analysis tool, the response surface model (RSMv2), is discussed. Aviation emissions for 2006 are generated using the Aviation Environmental Design Tool (AEDT), while future-year aviation emissions are developed for 2020 and 2030 using the Federal Aviation Administration (FAA) Terminal Area Forecast (TAF) and the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP/8) NOx Stringency scenario #6. Background emissions for the year 2005 and 2025 are generated from the US Environmental Protection Agency (EPA) National Emissions Inventory (NEI), and two additional sensitivity scenarios are derived from the emissions forecasts. Uncertainties in present and forecast aviation and background emissions are also characterized. The Community Multiscale Air Quality (CMAQ) model is evaluated to quantify its performance in predicting ambient PM2.5 and ozone concentrations, and it is used to estimate aviation air quality impacts of aviation. Future-year aviation particulate matter (PM2.5) concentrations are found to increase by a factor of 2 and 2.4 by 2020 and 2030, and are dominated by nitrate and ammonium PM. Aviation 8-hour daily maximum ozone is seen to grow by a factor of 1.9 and 2.2 by 2020 and 2030, with non-homogeneous spatial impacts. Aviation PM2.5 varies by +/-25% with a +/-50% variation of the forecast change in background emissions, while changes in ozone impacts are less symmetric at +34%/-21%. The RSMv2 is shown to under-predict future-year aviation nitrate and ammonium PM2.5. Finally, the implications of these results on the aviation industry and on aviation policy are discussed.
by Akshay Ashok.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005.
Includes bibliographical references (p. 121-123).
Decisions that guide technology investment and policy-making for the future of air transportation will be based in part on the tradeoffs between environmental performance and economics. The Environmental Design Space (EDS) project explores the tradeoffs between noise, emissions, and economics for conceptual design of future aircraft. A key component to EDS is modeling the emissions of aircraft in operation. Traditional design tools need more detailed mission analysis to calculate operational emissions in the landing and takeoff cycle (LTO), and in cruise. This thesis presents a methodology for modeling an aircraft flight profile and the corresponding aircraft and engine states required to calculate emissions over that mission. The methodology was implemented as an operations model in EDS. The development of the methodology and demonstrations of the model are presented in this thesis. The model takes user-input flight procedures, including mission range, and uses aerodynamic models and engine models from EDS to calculate flight profiles. The operations model can be used for analyzing the relationships between flight procedures, and emissions and fuel burn for a fixed design. Alternatively, multidisciplinary design optimization (MDO) with EDS and the operations model can be used to optimize the aircraft design for minimized emissions in the flight profile.
(cont.) MDO with the new model enables exploration of a design space that includes operations along with design in evaluating tradeoffs between emissions, noise, and economics. In addition to the development and demonstration of the operations model, a detailed study of the effects of derated-thrust takeoffs on emissions and fuel burn for Boeing 777 flights is presented in this thesis. The emissions of airline flights are calculated from flight data and compared to International Civil Aviation Organization (ICAO) assumptions for the engines used. The results show that NOx emissions are significantly less than the ICAO assumed values for takeoff and climb-out. A second analysis compares the emissions of derated thrust; takeoffs to the emissions that would have resulted if the same aircraft had flown with full-power on the same day. The results show a relationship between percent derate and a change in the emissions produced in takeoff, and a tradeoff of increased fuel burn for a decrease in NOx production.
by Daniel J. King.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 121-122).
In this thesis, we analyze how electromagnetic waves propagate in ionosphere around the earth which is magnetized plasma. We calculate the electromagnetic wave field made by a dipole antenna at an arbitrary observation point far from the antenna using the Stationary Phase Method. With this wave field, wave energy flux is calculated, and by integrating this wave energy flux on the sphere around the antenna, the radiation resistance of this antenna is computed. We compare the results with some past analytical and experimental works. We also analyze the wave propagation characteristics. The wave propagation ways are different for different wave frequencies. We precisely analyze this different wave propagation ways by analyzing the group velocity and k surface of the wave. There are intense radiation directions. We discuss the nature of these intense radiation directions and compare the characteristics with the past works. There are spatial oscillations of wave fields and wave energy flux. We also discuss the reason of this oscillation and compare with the past works.
by Yu Takiguchi.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.
This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from department-submitted PDF version of thesis.
Includes bibliographical references (p. 44-47).
Aircraft emissions impact the environment by changing the radiative balance of the atmosphere and impact human health by adversely affecting air quality. Many tools used to quantify aircraft emissions are not open source and in most cases are computationally expensive. This limits their usefulness for studies that require rapid simulation, such as uncertainty quantification and assessment of many policy options. We describe the methods used to develop the open source Aviation Emissions Inventory Code (AEIC) and produce a global emissions inventory for the year 2005 from scheduled civil aviation, with quantified uncertainty. This is the most up-to-date openly available inventory for use in atmospheric modeling studies. We estimate that in 2005, scheduled civil aviation was responsible for 180.6 Tg (90% CI: 136.1-232.9 Tg) of fuel burn, equating to 155.5 Tg of CO2 as C (90% CI: 117.3-200.7 Tg) and 0.108 Tg of SOx as S (90% CI: 0.080-0.142 Tg) emissions. 2.689 Tg of NOx as NO2 (90% CI: 1.761-3.804 Tg), 0.749 Tg of CO (90% CI: 0.422-1.145 Tg), and 0.201 Tg of HC as CH4 (90% CI: 0.072-0.362 Tg) were also emitted. 92% of fuel burn took place in the northern hemisphere. Landing and takeoff operations were responsible for 9.1% of total global fuel burn, while 70.6% of fuel burn occurred above 8 km. Our total fuel burn estimate agrees within 4% of other published emissions inventories for the years 2004 and 2006, which is within the uncertainty range of the analysis.
by Nicholas W. Simone.
S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.
In title on title page, double underscored "x" appears as subscript. Cataloged from PDF version of thesis.
Includes bibliographical references (pages 47-49).
Aviation NOx emissions are byproducts of combustion in the presence of molecular nitrogen. In the upper troposphere, NOx emissions result in the formation of O₃ but also reduce the lifetime of CH4 , causing an indirect reduction in the formation of O₃. Meta studies by Lee et al. and Prather et al. concluded that the short-lived O₃ radiative forcing (RF) was greater than the combined long-lived CH₄ and O₃ RFs, leading to a net positive RF (4.5 to 14.3 mW/m² per Tg of NOx emissions). However, few simulations assess the surface air temperature (SAT) response, or conduct a large ensemble simulation with climate feedback in the cases where SAT is predicted. We aim to quantify the climate forcing and temperature response of aviation NOx emissions. Eight 400-member ensemble simulations are conducted with an earth system model of intermediate complexity. Inter-scenario comparisons between emissions starting in 1991, 2016 and 2036 with mid-range and high anthropogenic emissions are performed. We then determine the existence of long-term temporal heterogeneity of climate forcing and impact. The global net RF of an aviation NO, emissions inventory is positive from 1991 to 2100 while leading to a global average SAT responses of -0.068 K in 2100. Despite the positive zonal RF in the Northern Hemisphere of up to 413.9 mW/m² at 45°N, all latitudes experience cooling after 2075. In another scenario, constant aviation NOx emissions at 4.1 Tg/year cause a global net RF of near zero while leading to a SAT response of -0.020 K in 2100. The unexpected temperature behavior in both scenarios is attributed to the forcing from CH₄ destruction being 64% more effective in generating a SAT response than the O₃ forcing. Despite the positive net RF, the probability of aviation NOx emissions being cooling is 67% because of the relative difference in O₃ and CH₄ efficacies.
by Lawrence Man Kit Wong.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008.
Includes bibliographical references.
Assessing candidate policies designed to address the impact of aviation on the environment requires a simplified method to estimate pollutant emissions for current and future aircraft gas turbine engines under different design and operating assumptions. A method for NOx and CO emissions was developed in a previous research effort. This thesis focuses on the addition of a soot mechanism to the existing model. The goal is to estimate soot emissions of existing gas turbine engines within soot measurement uncertainties, and then to use the method to estimate the performance of potential future engines. Soot is non-volatile primary particulate matter. In gas turbine engines the size rarely exceeds l [mu]m. The soot is composed almost exclusively of black carbon, is an aggregate of nearly spherical carbon primary particles, and exhibits fractal behavior. Results of other studies regarding soot nucleation, growth, oxidation, and coagulation rates are integrated within a network of perfectly-stirred reactors and shown to capture the typical evolution of soot inside a gas turbine combustor, with soot formed in the early parts of the combustor and then oxidized. The soot model shows promising results as its emissions estimates are within the measurement uncertainties. Nevertheless, model uncertainties are high. They are the consequence of the large sensitivity to input variables. Therefore, the validity of the model is limited to cases with available engine data. More engine data are needed to develop and assess the soot model.
by Bastien Martini.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.
Includes bibliographical references (leaves 121-124).
Typical electric propulsion devices rely on the acceleration of highly ionized plasmas to produce thrust at specific impulses unattainable with state-of-the-art chemical systems. This thesis examines the use of a miniaturized Helicon plasma source for an open-ended, electrode-less, cathode-less thruster through emission spectroscopy. The use of non-invasive diagnostics allows the measurement of important plasma parameters near the ionization region, where the plasma densities and temperatures are prohibitively high for typical electrostatic probes, while avoiding the inherent perturbations caused by invasive techniques. A spectral study of the Helicon antenna region, yielding axially resolved information on the electron temperature and degree of ionization, is discussed. A similar study in the near-field plume is presented, along with Doppler shift measurements, which clearly demonstrate continued acceleration upstream of the thruster exit. The Doppler shift measurements are validated by extending the study to a Hall effect thruster plasma, well characterized in the literature. Ion flux estimates from the downstream portion of the spectroscopic survey are compared with Faraday probe measurements. Possible mechanisms for thrust are presented along with their implications on Helicon thruster design.
by Taylor Scott Matlock.
S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 231-239).
Electric thrusters are being developed for in-space propulsion needs of spacecraft as their higher specific impulse enables a significant reduction in the required propellant mass and allows longer duration missions. Over the last few decades many different electric propulsion concepts have been proposed and studied. In studying the electric thrusters, in order to improve the thruster performance as well as to understand the underlying physics of thruster's operation, various diagnostics methods were employed. As one unique method, emission spectroscopy provides a non-invasive, fast and economical diagnostic allowing also the ability to access hard to reach locations. In this study, emission spectroscopy is employed as a means to determine the trends in thruster operations as well as diagnosing the plasma parameters. This study presents the spectral measurement results of three different electric thrusters and plasma sources. First, the BHT-200 Hall thruster emission spectra measurements are presented for varying discharge voltage and for various regions of observation.
(cont.) Second, spectral measurements of a TAL type laboratory mini-Hall thruster, MHT-9, were presented. Third, radiation emission measurements of an experimental Helicon plasma source being studied to assess the possibility of using Helicon discharge as a propulsive system are presented and the trends are discussed. Two collisional-radiative (C-R) models are developed for Argon and Xenon plasmas to analyze the experimental spectra. In the C-R models, electron induced excitation, deexcitation and ionization collisions, and spontaneous radiative de-excitation transitions are simulated for neutral and singly charged ion species. The models are validated against measured spectra obtained using different experimental setups. The BHT-200 Hall thruster has insulator ceramic annular walls made of Boron-Nitride (BN). Erosion of ceramic walls is one of the major life limiting factors for Hall thrusters. Emission spectroscopy is used as a means to determine the trends in the thruster wall erosion rate by measuring the radiation emission of the Boron neutral 249.68nm and 249.77nm lines. Discussion about the spectral measurements and relevant analysis are presented.
by Murat Çelik.
Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics; and, (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2008.
Includes bibliographical references (p. 121-129).
An exploration of the health implications of aviation emissions regulations is made by assessing the results of a study of aviation's effects on United States air quality mandated by the Energy Policy Act of 2005. The Energy Policy Act study results estimated that aviation is responsible for 160 yearly incidences (with a 90% confidence interval of 64 to 270 incidences) of premature mortality of adults age 30 and over ($882 million in year 2001 dollars, with a 91% CI of $196 to $1830 million) due to exposure to particulate matter below 2.5 /im in size (PM2.5) in the continental U.S. as reported by the Environmental Benefits Mapping and Analysis Program (BenMAP). Strong regional differences were noted; for instance, 18% of the total health incidences and costs occurred in Los Angeles County. Aviation was estimated to decrease ozone concentrations, causing small premature mortality disbenefits (health effects avoided due to the presence of aviation) of approximately 2 yearly premature mortality incidences ($9 million). Primary particulate matter values in the Energy Policy Act study's emissions inventory had been generated using a conservatively biased version of the First Order Approximation method version 3.0 (FOA3), known as FOA3a, and the emissions of sulfur oxides (SOx) had been incorrectly computed (underestimated by approximately 15%). To quantify the effects of these differences on health impacts, a comparison was made with a second inventory generated by CSSI, Inc. using FOA3. Based on the comparison, it is estimated that aviation was responsible for 140 to 160 yearly incidences of premature mortality from exposure to PM. 46% to 69% of the incidences were estimated to be due to changes in concentrations of ammonium sulfate secondary PM from SOx, while ammonium nitrate secondary PM was estimated to be responsible for 18% to 20%.
(cont.) Concentrations of volatile primary PM from organic compounds and nonvolatile primary PM were responsible for 6% - 18% and 5% - 14% of the impact, respectively, while volatile primary PM from sulfates was responsible for 0% to 4%. Confidence intervals were not computed, and only the effects of changes in PM concentrations were assessed. Based on the results, it is determined that changing regulations governing nitrogen oxide (NOx) emissions and fuel sulfur content may be effective strategies to mitigate incidences of premature mortality due to aviation. An assessment was made of the effects of changing fuel sulfur concentration from 600 parts per million (ppm), as is typical of current jet fuel, to 15 ppm across the continental U.S. It is estimated that this change would reduce yearly premature mortality incidences due to aviation-related ambient PM exposure by 38%. Confidence intervals were not computed. The cumulative additional costs to refineries to produce 15-ppm fuel could be approximately $260 million, suggesting that the benefits may be comparable to the costs. However, such a strategy could have climate warming impacts since aviation sulfur emissions have a cooling influence on climate. It is also estimated that an immediate deployment of ultra-low sulfur fuel only for takeoffs from Los Angeles County could reduce aviation-related nationwide yearly incidences of mortality by 10%, with Los Angeles County health impacts bring reduced by a factor of 2. The additional costs to refineries may be approximately $12 million, suggesting that such a policy may be cost-beneficial. Finally, a brief exploration is done of a NOx stringency assessment by the International Civil Aviation Organization's Forecasting and Economic Analysis Support Group (FESG), which predicted that an industry-wide investment of $30,000 - $40,000 would be required for every tonne of NOx eliminated if the ICAO NOx standard were to be increased by 10% in the year 2008.
(cont.) FESG found this to be the most cost-effective NO, reduction strategy. A direct comparison with the Energy Policy Act and RSM results is difficult, yet an assessment finds that NO, has health costs of only $2,000 per tonne in both sets of results.
by Christopher J. Sequeira.
S.M.

The level of ownership and use of motorcycling has increased rapidly in Edinburgh and the UK in the last ten years. In this study, motorcycle driving cycles (rural and urban) were developed for Edinburgh (Edinburgh Motorcycle Driving cycle-EMDC). The analysis of EMDC demonstrates that motorcycles‘ driving behaviour differs between urban and rural areas. EMDC shows a typical transient nature of speed, acceleration and deceleration, which is also different from regulatory driving cycles (Economic Commission for Europe-ECE and World Motorcycle Test Cycle-WMTC) and examples from Asia (Taiwan, Bangkok and China). This research underlines the need for detailed investigations of driving cycles in any local condition. It is not generally feasible for a driving cycle developed in one area to be applicable in another area, even with some similar characteristics. Emission factors were also estimated using onboard, laboratory and micro simulation measurements along the test corridor (Air Quality Management Area-AQMA). Laboratory measurements were carried out by applying a number of standard driving cycles (ECE and WMTC) and the derived EMDCs. Results show that the emission factors (EFs) calculated in the laboratory for carbon monoxide (CO) and Hydrocarbons (HC) are higher for the urban EMDC cycle compared to the standard regulatory factors than they are for the rural (except Nitrogen Oxide-NOx). Laboratory emission factors for CO and HC for the urban EMDC were found to be higher than the micro-simulation and onboard methods. EFs obtained from micro-simulation and onboard emissions using the National Atmospheric Emission Inventory (NAEI) emission coefficients were not very different with the exception of NOx, which were relatively higher than those of EMDC. Micro simulation models were mainly developed for private cars and therefore special care should be taken when using them for modelling other conditions (e.g. motorcycles driving characteristics). This study illustrates the extent to which micro-simulation may be utilised to accurately model emissions and discusses the refinements required to model motorcycle motion (hence emission) accurately in micro simulation. The study provides a platform for a large number of potential future applications for the evaluation of emissions and for developing various policy scenarios of pollution reduction and reducing health impacts at local levels.

Carbon emissions from road transport make up 20% of the total greenhouse gas emissions in the UK. Therefore, reducing carbon emissions from road transport is significant in reaching carbon reduction targets. In urban areas where signal controlled intersections are common, carbon emissions from vehicular traffic can be aggravated by aggressive driving and interruptions induced by traffic control. Considerable variations in speed and acceleration profiles could be observed between high carbon and low carbon driving. In view of the immediate effects that changing driving behaviour could have on carbon emissions without extra cost, this study had investigated the variations in carbon emissions at signalised intersection, which includes the scale of impacts of changing driving behaviour and flow interruption on carbon emissions. Characteristics which lead to high CO2 emissions could then be modified by addressing the behavioural change and control strategies. High frequency real world driving data was collected using the TRG highly instrumented vehicle. The vehicle was equipped with a number of on-board systems, i.e., on-board emission measurement system, velocity box, on-board diagnostic unit, Dashdyno and video recorder. Aggressive and economical driving styles observed for two drivers during initial tests showed distinct differences in terms of speed profiles and fuel consumption. These initial tests were used to examine the nature and scale of potential impacts on fuel consumption and to design main field tests. Natural driving observed from twenty nine drivers from the main field tests also showed significantly different levels of carbon emissions at signalised intersections, which were caused by variations in both driving behaviour and traffic control. In terms of driving behaviour, changing the worst driving to the best driving during interrupted driving was found to reduce CO2 emissions significantly. The carbon reductions were collectively contributed by 1) applying soft acceleration and keeping acceleration below 0.6m/s2 during the acceleration mode and 2) reducing leaving speed at intersections, 3) practising smooth deceleration and stable speed during the deceleration mode and 4) applying the idle-stop system. Carbon emission rates of different vehicles may vary from one to another. However, it was found that the amount of carbon savings demonstrated in this study could be possibly achieved by other internal combustion vehicles of the same class, and by hybrid electric vehicles to a lesser extent. In this study, changing driving behaviour is recommended as a cost effective way to achieve carbon reduction.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 135-144).
The long-term viability and success of a transportation fuel depends on both economic and environmental sustainability. This thesis focuses specifically on assessing the life cycle greenhouse gas (GHG) emissions and non-CO 2 combustion effects from conventional jet fuel and synthetic paraffinic kerosene (SPK). The research expands upon the work of Wong (2008) by examining Fischer-Tropsch jet fuel from coal and biomass, and hydroprocessed renewable jet (HRJ) fuel from rapeseed, jatropha, algae and salicornia. Each fuel option is a "drop-in" alternative in that they are compatible with existing aviation infrastructure. Using a modified version of the APMT climate impacts module, the additional climate forcing from non-CO 2 combustion effects is combined with the fuel life cycle GHG inventories. Life cycle GHG emissions are only one of many aspects that must be considered when evaluating the feasibility and sustainability of an alternative fuel option. While cost and fresh water availability are important constraints, fuel yield and land requirements for select biomass-based fuel pathways are quantified. This is most important for feedstocks requiring cropland for cultivation. For example, current global production of soy, palm and rapeseed oil translate to only 34%, 43% and 18% of US jet fuel demand, respectively; hence, even small fractions of the petroleum industry translate to massive production scales in absolute terms. By comparison, HRJ from algal oil can yield more than an order of magnitude higher fuel production per hectare of land. Few biofuels were identified with zero life cycle GHG emissions. This contradicts previous studies and likely results from avoiding the displacement method to allocate emissions. Considerable inter and intra fuel option variability was found in life cycle GHG emissions; land use change contributed much to the variability of many pathways. The range in life cycle GHG emissions of all fuel options examined ranged from 0 to 9.1 times those of conventional jet fuel. The uncertainty in treating non-CO 2 combustion effects was found to have a larger influence on the life cycle emissions of each fuel option than the variability of the life cycle GHG inventories; however, including non-CO 2 combustion effects reduced the overall range in emissions of all fuel options considered to only 0 to 4.7 times those of conventional jet fuel. Hence, the inclusion of non-CO 2 effects in the fuel life cycle increases the absolute uncertainty of each fuel option but reduces the overall variability in the life cycle emissions of alternative fuels relative to conventional jet fuel.
by Russell William Stratton.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.
Includes bibliographical references (leaves 142-148).
World-wide demand for air transportation is rising steadily. The air transportation network may be limited by aviation's growing environmental impacts. These impacts take the form of climate impacts, noise impacts, and health impacts, the latter of which are addressed in this thesis. Aircraft emissions released into the atmosphere have an impact on human health. In the context of assessing the environmental impacts of aviation-related policies, costs and benefits on human health must be considered. Two different models were developed as tools to assess the impacts of aircraft emissions on human health. The first model estimates the changes in skin cancer incidences and mortalities due to changes in ozone column caused by aircraft NO, emissions. The second model estimates changes in health endpoits related to changes in ambient concentrations of particulate matter (PM25) by estimating changes in elemental carbon, primary and secondary organic PM, secondary sulfates, and secondary nitrates. The air quality model discussed herein is the second iteration in the development of a response surface model (RSM) based on a set of 25 simulations done with the Community Multiscale Air Quality model (CMAQ), a more complex atmospheric chemistry model. The increase in adult premature mortalities in the U.S. caused by air quality impacts of aviation emissions in year 2005 is estimated at 210 deaths per year (90% confidence interval: 130 - 340). This considers only those emissions that occur below 3000 feet above ground level as is consistent with current regulatory practice for aviation.
(cont.) The monetized value of the mortality and morbidity effects using RSM v2 outputs is estimated at $1.4 billion in year 2000 US dollars (90% confidence interval: $550 million - $2.8 billion). Of these total impacts, 4 % are found to stem from emissions of volatile organic compounds and volatile particulate matter from organics, another 12 % from emissions of sulfur dioxide and volatile particulate matter from sulfur, 70 % from nitrogen oxide emissions, and 14% from non-volatile particulate matter emissions The net benefit from subsonic aircraft NOx in year 2002 on nonmelanoma skin cancer incidence and associated mortality in the U.S. is estimated at $130 M (90 % confidence interval : $68 - $220 M) in 2000 dollars. This corresponds to the prevention of approximately 6,200 new basal cell carcinoma cases (BCC) (90 % confidence interval: 3,800 - 9,100), 2,900 new squamous cell carcinoma cases (SCC) (90 % confidence interval: 1,700 - 4,200), and 20 nonmelanoma skin cancer (NMSC) premature mortalities (90 % CI : 13 - 28). The monetary benefits due to the prevention of 20 cases of premature mortality represent 96 % of total skin cancer benefits.
by Elza Brunelle-Yeung.
S.M.

Aviation is at a turning point. Considerable improvements in aircraft emissions efficiencies are expected through technological improvements, air traffic management, and managerial strategies. But global demand for air travel is increasing at an even faster rate. Mostly for political reasons, aviation has been left behind in international efforts to tackle climate change. However, increasing pressure is on the industry for immediate action, thus making further delays impossible.
This thesis is an attempt to determine the best possible course of action for the industry. To this end, it begins by assessing contemporary understanding of aviation's impact on the environment, and provides an overview of efforts being made toward reducing aircraft emissions. It then examines various policymaking tools available to best address the issue, concluding with an emissions trading system. Finally, design characteristics of such a system are suggested, and used to provide an analysis of the European attempt to include aviation into its own emissions trading system.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 96-97).
Lighting strikes are a problem for aircraft flying in large external electric fields. In most cases, the strike is triggered by the aircraft; as it flies through an electric field, it becomes polarized, and on areas with small radius of curvature, the electric field is magnified. This can result in bidirectional leaders which extend from opposite polarity aircraft extremities. These can connect to oppositely charged regions in a cloud or the ground, resulting in a lightning strike. Current methods to avoid lightning are limited to avoiding thunderstorm regions, as recommended by weather radar or conversations between pilots and the ground. Methods to treat the symptom of a strike have been relatively successful; a mesh placed under the skin of the aircraft can distribute the current and heat of the localized strike. However, there are currently no active measures to prevent the strike from happening.
The Boeing Lightning Strike team at MIT has recently proposed an active system that exploits the physics of how a lightning arc is triggered from an aircraft in flight based on net charge control of the vehicle. The objective of this thesis is to prove the feasibility of controlling the net charge of an aircraft in flight by using ion emission from its surface. Different strategies to control the net charge of a flying isolated body were explored and analyzed. The first strategy tested was based on using charge emission from an electrospray source. A passive flow and forced flow configuration were tested, however it was shown that there were numerous difficulties associated with running the electrosprays in atmospheric pressure. To overcome the limitations of the electrospray source, a second strategy was tested based on a controlled corona discharge, which is known to have increasing current emission with increasing wind speed.
The first experiment was setup in the Wright Brothers Wind Tunnel; sharp tips were used to generate a corona discharge and a metallic sphere was used to simulate the aircraft. Significant electrical potential saturation was observed on the sphere, and it is likely this was due to the filamentary streamer corona regime which produces both positive and negative ions. Thus a new experiment was designed; a thin wire was used to generate a glow corona, which produces predominantly positive ions, and this was attached using GlO (a fiberglass composite material) to a metallically coated airfoil. Charging of much higher magnitudes was observed, indicating the glow corona regime is critically important in optimizing the potential of the airfoil. Charge control of an airfoil (Chord 0.2 m, Span 1 m) at 40 m/s was demonstrated to a level of -42 kV.
For an object of a given characteristic size, a certain amount of charge is required to satisfy the optimal charge condition, where negative and positive leader strikes are both equally likely or unlikely. The achieved potential of -42 kV is the order of magnitude required for this size airfoil based on the theoretical estimates, and these tests also showed a trend of linear potential variation with wind speed.
"Boeing Company for financially supporting my Research Assistantship"
by Theodore Mouratidis.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

The chemical and physical limits of cycle-to-cycle combustion variability and engine out emissions of a gasoline port fuelled spark ignition engine have been investigated. The experimental investigations were carried out on a V8 engine with port fuel injection and variable intake valve timing. The chemical limits of stable combustion have been shown to be a function of burned gas, fuel and air mixture. The widest limit, gas fuel ratio of <24, burned gas fraction <0.27 and AFR >9 was found at maximum brake torque spark timing. Retarding the spark timing by 10oCA caused a small reduction in the stable area, 20oCA retard reduced the stable combustion area significantly, whereby stable combustion occurred within an area of gas fuel ratio of <19, burned gas fraction <0.2 and AFR >10. Burn rate analysis indicated increased variability in both the flame development and rapid burn period. The increase in variability in the rapid burn period is greater than that associated with the flame development. The variability is magnified from flame development through the rapid burn phase. This finding was consistent for unstable combustion caused by exceeding chemical and physical limits. Engine out emissions were investigated and characterised using engine global state parameters, for example AFR, burned gas fraction, for both stable and unstable combustion conditions. Carbon monoxide and oxides of nitrogen emissions correlations were unaffected by the presence of unstable combustion events whereas hydrocarbon emissions showed a significant increase. The incorporation of these findings were implemented into an engine simulation (Nu-SIM V8) investigating the impact for the New European Drive Cycle condition.

Thesis (M.S. in Aeronautical Engineering and Aeronautics and Astronautics Engineer's Degree)--Naval Postgraduate School, December 1990.
Thesis Advisor: Gorman, Michael R. Second Reader: Dutta, Indranath. "December 1990." Description based on title screen as viewed on April 2, 2010. DTIC Identifier(s): Aluminum, fatigue (mechanics), cracking (fracturing), acoustic emissions, wings, fixed wing aircraft, reconnaissance aircraft, flight simulation, 7075 aluminum, theses, naval aircraft, stress waves, crack propagation, acoustic detection, fatigue life, E-2c aircraft, safety factor, mechanical properties. Author(s) subject terms: Includes bibliographical references (p. 69-71). Also available in print.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics; and, (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 139-141).
Taxiing aircraft contribute significantly to the fuel burn and emissions at airports. This thesis investigates the possibility of reducing fuel burn and emissions from surface operations through a reduction of the taxi times of departing aircraft. Data analysis of the departing traffic in four major US airports provides a comprehensive assessment of the impact of surface congestion on taxi times, fuel burn and emissions. For this analysis two metrics are introduced: one that compares the taxi times to the unimpeded ones and another that evaluates them in terms of their contribution to the airport's throughput. A novel approach is proposed that models the aircraft departure process as a queuing system. The departure taxi (taxi-out) time of an aircraft is represented as a sum of three components: the unimpeded taxi-out time, the time spent in the departure queue, and the congestion delay due to ramp and taxiway interactions. The dependence of the taxi-out time on these factors is analyzed and modeled. The performance of the model is validated through a comparison of its predictions with observed data at Boston's Logan International Airport (BOS). A reduction in taxi times may be achieved through the queue management strategy known as N-Control, which controls the push back process so as to keep the number of departing aircraft on the surface of the airport below a specified threshold. The developed model is used to quantify the impact of N-Control on taxi times, delays, fuel burn and emissions at BOS. Finally, the benefits and implications of N-Control are compared to the ones theoretically achievable from a scheme that controls the takeoff queue of each departing aircraft.
by Ioannis Simaiakis.
S.M.in Technology and Policy
S.M.

The particulate matter is probably one of the most critical issues of the diesel engine emissions. After years of research, people begin to understand it further, with respect to its impact on the environment and human health, its formation mechanism inside and outside the diesel engine, and most importantly, the methods to control its formation. This study has focused on the particulate matter emission control in diesel engines. It started with the application of two closely coupled Diesel Particle Filters (DPFs), consisting of an assistant DPF and a main standard honeycomb DPF, to replace the standard Diesel Oxidation Catalyst (DOC) + DPF system, commonly applied on diesel engines these days. This new after-treatment system showed a great potential to be adopted in the future, not only for the tighter emission regulations but also for the great cost reduction of the total after-treatment system by the reduction of the main DPF’s size and weight and more options of other cheaper materials. The back pressure problem revealed in the experiment was then studied through a one dimensional model simulation and its influence to the engine performance was discussed. Fuel injection parameters which are related with the engine performance and emissions were also investigated in the study. After careful calibrations, a single injection induced Partially Charge Compression Ignition (PCCI) combustion was achieved, in which mode, NOx and smoke emissions were reduced by more than 80% compared with using the normal multiple injections. Following that, the non-volatile particulate emissions under the pilot injection’s impacts were studied and the key parameters of the pilot control such as fuel quantity and injection timing were examined. The particulate number concentrations and size distributions were investigated under different engine operation conditions and the results illustrated how a pilot injection alongside a main injection could influence particulates and what these effects were closely related to. The research continued with the investigation of bio-fuels on the particle emission reduction, when 10% alternative diesel fuel blends (Rapeseed Methyl Ester (RME) and Gas-to-Liquid (GTL)) were used. They indicated that without any modification to the engine, adding selected alternative fuels, even at a low percentage, could result in a noticeable reduction of the particle numbers, both in the total and the non-volatile parts; however, the number of nucleation mode particles could increase in certain cases. It was also revealed that the engine suffered very high numbers of the nucleation mode particulates during warming up.

This master thesis is the result of a collaborative work between EMBRAER and the Escola Politécnica da USP for the study of structural health monitoring (SHM) techniques using sensors applied to aircraft structures. The goal was to develop classification techniques to discriminate between different events arising in the aircraft structure during tests; in the short term, improving the current SHM system used by EMBRAER, based on acoustic emission and, in the long term, fostering the development of a fully distributed system. As a result of studying classification methods for immediate use, we developed two techniques: the Spectral Similarity and a Support Vector Machines (SVM) classifier. Both are unsupervised solutions, due to the unlabeled nature of the data provided. The two solutions were delivered as a final product to EMBRAER for prompt use in the existing SHM system. By studying distributed solutions for future implementations, we developed a detection algorithm based on adaptive techniques. The main result was a special initialization for a maximum likelihood (ML) detector that yields an exponential decay rate in the error probability to a nonzero steady state, using adaptive diffusion estimation in a distributed sensor network. The nodes that compose the network must decide, locally, between two concurrent hypotheses concerning the environment state where they are inserted, using local measurements and shared estimates coming from their neighbors. The exponential performance does not depend on the adaptation step size value, provided it is sufficiently small. The results concerning this distributed detector were published in the journal IEEE Signal Processing Letters.
Esta dissertação de mestrado é o resultado de um trabalho colaborativo entre a EMBRAER e a Escola Politécnica da USP no estudo de técnicas de monitoramento do estado de saúde de estruturas (Structural Health Monitoring - SHM) utilizando sensores em estruturas aeronáuticas. O objetivo foi desenvolver técnicas de classificação para discriminar entre diferentes eventos que surgem em estruturas aeronáuticas durante testes; para o curto prazo, aperfeiçoando o atual sistema de SHM utilizado pela EMBRAER, baseado em emissão acústica e, no longo prazo, fomentando o desenvolvimento de um sistema completamente distribuído. Como resultado do estudo de métodos de classificação para uso imediato, desenvolvemos duas técnicas: a Similaridade Espectral e um classificador que utiliza Support Vector Machines (SMV). Ambas as técnicas são soluções não-supervisionadas, devido a natureza não rotulada dos dados fornecidos. As duas soluções foram entregues como um produto final para a EMBRAER para pronta utilização em seu atual sistema de SHM. Ao estudar soluções completamente distribuídas para futuras implementações, desenvolvemos um algoritmo de detecção baseado em técnicas adaptativas. O principal resultado foi uma inicialização especial para um detector de máxima verossimilhança (maximum likelihood - ML) que possui uma taxa de decaimento exponencial na probabilidade de erro até um valor não nulo em regime estacionário, utilizando estimação adaptativa em uma rede distribuída. Os nós que compõem a rede devem decidir, localmente, entre duas hipóteses concorrentes com relação ao estado do ambiente onde eles estão inseridos, utilizando medidas locais e estimativas compartilhadas vindas de nós vizinhos. O desempenho exponencial não depende do valor do passo de adaptação, se este for suficientemente pequeno. Os resultas referentes a este detector distribuído foram publicados na revista internacional IEEE Signal Processing Letters.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 35-37).
Combustion emissions constitute the largest source of anthropogenic emissions in the US. They lead to the degradation of air quality and human health, by contributing to the formation of fine particulate matter (PM2 .5 ), which is harmful to human health. Previous work computed the population PM2 .5 exposure and number of early deaths caused by emissions from six major sectors: electric power generation, industry, commercial and residential activities, road transportation, marine transportation and rail transportation. In the present work we go beyond aggregate sectors and now attribute exposure and early deaths to sectors, emissions species, time of emission, and location of emission. This enables determination of the emissions reductions that would have the greatest benefit by sectors, species, time and location. We apply a long-term adjoint sensitivity analysis with population exposure to PM2 .5 in the contiguous US as the objective function, and calculate the four dimensional sensitivities (time and space) of PM2 .5 exposure with respect to each emissions species. Epidemiological evidence is used to relate increased population exposure to premature mortalities. This is the first regional application of the adjoint sensitivity analysis method to characterize long-term air pollution exposure. (A global scale application has been undertaken related to intercontinental pollution.) We find that for the electric power generation sector 75% of the attributable PM2 .5 exposure is due to SO2 emissions, and 80% of the annual impacts are attributed to emissions from April to September. This suggests that burning of low sulfur coal has greatest benefit in the summer. In the road transportation sector, 29% of PM2 .5 exposure is due to NO, emissions and 33% from ammonia (NH3), which is a result of emissions after-treatment technologies. We estimate that the benefit of reducing NH3 emissions from road transportation is ~20 times that of NOx per unit mass. 75% of the road transportation ammonia impacts occur during the months October to March. We rank the states based on their contribution to the overall combustion emissions-attributable PM2 .5 exposure in the US, and calculate that California contributes 12%, Pennsylvania 7% and Ohio 5.8%. We publicly release the sensitivity matrices computed, noting their potential use as a rapid air quality policy assessment tool.
by Irene Constantina Dedoussi.
S.M.

Experience shows that the noise and sound quality in vehicles are often a recurring criticism. The bodies of modern vehicles consist predominantly of thin sheets of metal. It is hard to prevent the excitation of bending vibrations and the subsequent emission of disturbing noise while driving. The noise spectrum in a car that can be heard by the driver is from ”latent roar” to ”chattering” noise of the body and engine. In automotive vehicles damped materials, especially plastics or materials made from sheet metal and surface damping treatments, are used. Those have high internal energy losses and damp sound oscillatory systems found in the body or interior of cars. A further advantage of such treated components is that they are applied to existing components working over wide temperature and frequency ranges. Many companies provide such ”sound-absorbing compounds”. The requirements for these damping materials are high temperature-resistance, water repellence, fuel and oil-resistance and good adhesion to the base material [17]. The acoustic properties, especially the damping of the plate vibrations through rubber are of interest. the question arises how can the damping coeficient of coated metal sheets can be measured and secondly, by how much the road noise is reduced when built-in sheets are coated with a known damped material. With the Oberst Bar Test Method (named after Dr. H. Oberst) the properties are determined of the internal damping materials that can be used to simulate mechanical constructions to determine damping of larger surfaces. This method describes a laboratory test procedure for measuring the mechanical properties of damped materials. A block diagram of the test system consisting of a damped material bonded to a vibrating cantilever steel bar is shown in figure 2.1. This method is useful for testing materials such as metals, enamels, ceramics, rubbers, plastics, reinforced epoxy matrices and wood. In addition to damping measurement, the test allows for the determination of the Young’s modulus E of the material. E is calculated from the resonance frequency of a given mode and from the physical constants of the bar. By associating the damping factor with the Young’s modulus, a complex quantity is defined which is called the Complex Modulus of Elasticity. Measurements of dynamic mechanical properties are also useful in the research on the molecular structure of materials.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 83-85).
Auroral phenomena are dynamic in nature: observed events have rich structures that are both spatially and temporally complex, with scientifically interesting features. While optical auroral observations using CCDs or all-sky cameras are common, the aurora also have interesting emission properties at radio frequencies (RF), specifically in low-frequency and high-frequency bands. The Auroral Emission Radio Observer (AERO) is a 6U CubeSat, equipped with a novel electromagnetic Vector Sensor (VS) antenna. The VS will target auroral emission in a measurement band from 100 kHz - 15 MHz, which enables the study of interesting emission types such as Auroral Kilometric Radiation (20 kHz -750 kHz), Medium Frequency Bursts (1.6 MHz - 4.4 MHz) and cyclotron emission (2.8 MHz - 3.0 MHz).
The VS antenna measures 4-meters tip-to-tip once deployed from the CubeSat frame, and expands to form electric dipoles and magnetic loop antennas that are sensitive enough to probe this diverse set of science targets. Having a spacebased platform, such as AERO's vector sensor antenna, positions the detector above the ionospheric plasma frequency which would otherwise limit observations of radio emissions. Novel measurements from AERO's VS antenna require a set of contextual data to validate the fidelity of resulting data products. AERO includes a secondary payload referred to as an Auxiliary Sensor Package (ASP) that will augment VS measurements with contextual optical and magnetic data. The objective of AERO's contextual optical measurement is to detect the presence of auroral emission in multiple spectral bands, namely green-line emission at 557 nm and red-line emission at 630 nm. An AMS AG AS7262 6-channel visual band spectral photometer is selected as the optical sensor.
We present a radiometric model that evaluates the AS7262 sensor's ability to measure target auroral events. We consider a number of different test scenarios, including varying parameters such as auroral source radiance in units of Rayleigh, spacecraft altitude, and others, to fully assess the sensor's ability to detect optical auroral signatures. The mission requirements include a minimum detection of 5 kR for the sensor to satisfy the optical measurement requirement. In our initial assessment, we find that the selected sensor in its current configuration may not be able to meet this requirement. In its current configuration, the sensor may be capable of detecting the presence of auroral events at high levels of intensity, in the over 100 kR range. The model developed in this work indicates that further analysis and possible modification to the front end optic or the sensor itself are needed.
Though the radiometric model presented is tailored for the AS7262 sensor, it is easily adaptable to assess the performance of other auroral imagers. The contextual measurements provided by the ASP will contribute to the success of the AERO CubeSat mission in demonstrating that remote sensing techniques on CubeSat platforms can address unanswered questions about the aurora.
by Cadence Payne.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.
Includes bibliographical references (p. 49-50).
Given the current level of concern over anthropogenic climate change and the role of commercial aviation in this process, the ability to adequately model and quantify fuel burn and emissions on a system wide scale is of high importance. In particular, the ability to adequately assess the ability of operational alternatives within the commercial aviation system to improve system efficiency and reduce environmental impact is essential. Much work has already been done with this end in mind; however, given the high degree of complexity associated with a large system such as this, there is opportunity for improvements in modeling capability. The work presented in this thesis was conducted with this aim, to build additional functionality and fidelity into an established modeling method. The FAA System for assessing Aviation's Global Emissions (SAGE)'is a well established model for the creation of global inventories of aviation fuel use and emissions. There are, however, two aspects of the model which could benefit from improvements in modeling methodology. The first is the way in which the specific fuel consumption (SFC) is calculated. Previous to this study, SFC was calculated through the methods put forward in EUROCONTROL's Base of Aircraft Data (BADA).
(cont.) These methods are based on aircraft type specific coefficients and perform well in the context of global inventories; however, they lack the necessary functional dependence on ambient and operational variables to adequately assess the effects of the small changes often associated with various operational alternatives. An effort was made to assess the functional dependence of SFC on these variables through statistical analysis of a large body of Computerized Flight Recorder Data (CFDR) and to use this as a basis for improving the modeling of SFC in SAGE. The result of this effort was the introduction of a statistically-derived SFC model into SAGE which contained the desired functional dependence on temperature, pressure, Mach number, and thrust, and thereby improved the fidelity with which fuel bum is modeled. This SFC model, as implemented in SAGE, reduced the average absolute error by 21% as compared to the original BADA model. Additional improvement was made with the introduction of weather information into the SAGE model. Previously, the model assumed standard atmospheric conditions and zero wind. An algorithm was devised which processed and incorporated global assimilated weather data from NASA Goddard into the performance calculations within SAGE.
(cont.) It was found the introduction of dynamic weather contributed greatly to the accuracy of SAGE given that the system wide average true airspeed error is 10% when the assumption of zero winds is used. Finally this improved model was used to quantify the benefits of implementing Reduced Vertical Separation Minimums (RVSM) in US airspace in January of 2005. This was accomplished through a comparison of system wide efficiency during representative time periods prior to and following RVSM implementation. The results of this analysis provide insight into not only the benefits of RVSM, but also the effects of these model improvements and the efficacy of the different efficiency metrics used. It was found that RVSM resulted in an increase in fuel efficiency (nm/kg) of 1.81% (± 0.55%) and an increase in NOx efficiency (nm/kg) of 3.14% (± 1.25%). An additional control comparison was made, during these same time periods, of system efficiency over the North Atlantic and Western Europe where RVSM had been implemented several years prior. Using an efficiency metric which normalized for the difference in winds between the two periods it was found that there was indeed no benefit seen in this control study providing support for the US Domestic RVSM results.
by Tim Yoder.
S.M.

L'une des préoccupations actuelles de l'industrie aéronautique est la diminution de la consommation de carburant et de l'empreinte environnementale. En effet, les émissions aéronautiques ont un impact sur la qualité de l'air et notamment au niveau des zones aéroportuaires. Comme d'autres secteurs du transport, le trafic aérien génère des gaz à effet de serre (2 % du total dans le monde), des traînées de condensation ainsi que des particules volatiles et non volatiles (vPM et nvPM).Pour réduire ces émissions, différentes approches ont été pensées avec en particulier l'usage de carburants aéronautiques durables (SAF - Sustainable Aviation Fuels). L'objectif des SAF est de réduire les émissions nettes de CO2 et de nvPM. Cependant, la combustion de ces carburants peut entraîner la formation de nouveaux polluants qui réagissent avec l'atmosphère en formant des aérosols secondaires (SA). Dans le cadre du projet UNREAL (Unveiling Nucleation mechanism in aiRcraft Engine exhAust and its Link with fuel composition), l'objectif de ce travail était d'étudier les différents mécanismes au niveau moléculaire à l'origine de la formation de nouvelles particules à partir des rejets moteurs alimentés par des carburants de compositions différentes, allant du Jet A-1 standard à du carburant 100 % SAF.La caractérisation physico-chimique des émissions en conditions réelles en sortie moteur est un défi à la fois d'un point de vue technique et économique. Pour pallier à cela un brûleur mini-CAST, adapté à la combustion de carburants liquides aéronautiques, a été utilisé comme alternative pour obtenir des émissions comparables, dans une certaine mesure, à celles des moteurs aéronautiques. Une diminution des émissions de nvPM (concentration en nombre, concentration en masse et distribution de tailles) peut être observée en corrélation avec la quantité de composés aromatiques présents dans le carburant. De plus, l'analyse par spectrométrie de masse a révélé une diminution de l'intensité relative des HAP lors de l'emploi de carburants alternatifs. Les émissions du brûleur ont été injectées, avec ou sans filtration des suies, dans une chambre atmosphérique de vieillissement (chambre CESAM reproduisant les conditions atmosphériques au niveau du sol - LISA). Pour tous les carburants testés, la formation de vPM par nucléation homogène a été observée dans la chambre atmosphérique en l'absence de nvPM. Ce phénomène est particulièrement prononcé pour les carburants comprenant de grandes quantités de soufre dans leur composition. Cependant, dans les cas réels (présence de suies), la formation de vPM n'est observée que pour les carburants contenant de fortes quantités de soufre. La concentration de précurseurs gazeux formés pour les autres carburants n'est pas suffisante pour produire des vPM, notamment avec l'adsorption des gaz à la surface des particules de suies (nucléation hétérogène). Les techniques de caractérisation en ligne ont été complétées par des prélèvements sur filtre et une analyse par spectrométrie de masse, mettant en évidence la présence de HAP, d'hydrocarbures oxygénés, de composés soufrés et azotés. En utilisant des méthodes semi-quantitatives, il a été possible de mettre en relation la composition chimique (intensité relative de soufre et de HAP) avec la formation de vPM et leur répartition dans les phases particulaires et gazeuses des émissions
One of the actual concerns of the aviation industry is to reduce fuel consumption and environmental footprint. Indeed, aviation emissions impact air quality in and around airports. As other transport sectors, aviation effluents need to be addressed to reduce greenhouse gases contribution (2% of these emissions are related to air transport worldwide), volatile and non-volatile Particulate Matter (vPM and nvPM) and indirect impact as condensation trails.To reduce these emissions, different approaches have been investigated, in particular the use of Sustainable Aviation Fuels (SAF). Aims of SAF are to decrease the net CO2 emissions and nvPM. However, combustion of these fuels may lead to new pollutants that can react with atmosphere by formation of secondary aerosols. As part of the UNREAL project (Unveiling Nucleation mechanism in aiRcraft Engine exhAust and its Link with fuel composition), the objective of this work was to study the different molecular mechanisms of new particle formation from the exhausts of aircraft engines fed by fuels with different composition, from the standard Jet A-1 to 100 % SAF fuel.The physicochemical characterisation of the particulate emissions from aircraft engines in real conditions is challenging both from the technical and economical point of view. Thus, a mini-CAST burner, suitable for the combustion of aeronautic liquid fuels, has been used as an alternative to obtain emissions comparable to some extent to those from aircraft engines. A decrease in nvPM emissions (number concentration, mass concentration and size distribution) can be observed in correlation with the quantity of aromatic compounds in the fuel. Moreover, the analysis by mass spectrometry revealed a decrease in the relative intensity of PAHs when alternative fuels were employed . Emissions from the burner have been injected, with and without soot filtration, into an atmospheric chamber for ageing (CESAM chamber reproducing atmospheric conditions at ground level - LISA). For all fuels tested formation of vPM by homogeneous nucleation has been observed in the atmospheric chamber in absence of nvPM. This phenomenon is particularly highlighted for fuels with high amounts of sulphur in their compositions. However, in real cases (presence of soot), the formation of vPM is only observed for the fuels containing high amounts of sulphur. The concentration of gaseous precursors formed for other fuels was not enough to produce vPM after being adsorbed on soot surface (heterogeneous nucleation). On-line characterisation techniques were completed by filter sampling and off-line mass spectrometry analysis, highlighting the presence of PAHs, oxygenated hydrocarbons, sulphur and nitrogen compounds. By employing semi-quantitative methods, it was possible to link the relative chemical composition (sulphur and PAH relative intensity) with vPM formation and their repartitions in particulate and gaseous phases

In this work, we describe all the possible radiative processes occuring in a low temperature hydrogen plasma. Some of the fundamental concepts involving ionized gases and collision phenomena are presented, and a rigourous approach is used to show that classical mechanics is quite appropriate to our study.

As an application to a laser engine, we investigate the effects of the maximum temperature, the temperature gradient, the stretching of the plasma shape, the engine pressure, and the equivalent sphere radius, on the total emitted power, including absorbing mechanisms through the equation of radiative transfer.

Graphs related to spectral radiative exitances are included, and a complete set of graphs of the total power, permitting interpolations with respect to the above relevant paramaters, are also provided.

Master of Science

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.
Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, Technology and Policy Program, 2017.
Cataloged from PDF version of thesis. In title on title page and in the Abstract, double-underscored "x̳" in "NOx̳" appears as subscript.
Includes bibliographical references (pages 57-65).
In September 2015, the Volkswagen Group (VW) admitted the use of "defeat devices" designed to lower emissions measured during VW vehicle testing for regulatory purposes. Globally, 11 million cars sold between 2008 and 2015 are affected, including about 2.6 million in Germany. On-road emissions tests have yielded mean on-road NOx̳, emissions for these cars of 0.85 g.km-¹, over four times the applicable European limit of 0.18 g.km-1 . This thesis estimates the human health impacts and costs associated with excess emissions from VW cars driven in Germany. A distribution of on-road emissions factors is derived from existing measurements and combined with sales data and a vehicle fleet model to estimate total excess NOx̳ emissions. These emissions are distributed on a 25 by 28 km grid covering Europe, using the German Environmental Protection Agency's (UBA) estimate of the spatial distribution of NOx emissions from passenger cars in Germany. I use the GEOS-Chem chemistry-transport model to predict the corresponding increase in population exposure to fine particulate matter and ozone in the European Union, Switzerland, and Norway, and a set of concentration-response functions to estimate mortality outcomes in terms of early deaths and of life-years lost. Integrated over the sales period (2008 - 2015), I estimate median premature mortality impacts from VW excess emissions in Germany to be 1,200 premature deaths in Europe, corresponding to 13,000 life-years lost and 1.9 billion EUR in costs associated with life-years lost. Approximately 60 % of mortality costs occur outside Germany. For the current fleet, I estimate that if on-road emissions for all affected VW vehicles in Germany are reduced to the applicable European emission standard by the end of 2017, this would avert 29,000 life-years lost and 4.1 billion 2015 EUR in health costs (median estimates) relative to a counterfactual case with no recall.
by Guillaume P. Chossière.
S.M.
S.M. in Technology and Policy

Thesis (MScIng)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: It was shown in an earlier study that it is possible to predict the spectral radiance of rocket combustion plumes directly from the propellant composition and motor parameters. Little is published in the open literature on this subject, but the current trend is to use determinative methods like computational fluid dynamics and statistical techniques to simulate wide band radiance based on blackbody temperature assumptions. A limitation of these methods is the fact that they are computationally expensive and rather complex to implement. An alternative modeling approach was used which did not rely on solving all the nonlinearities and complex relationships applicable to a fundamental model. A multilayer perceptron based Neural Network was used to develop a parametric functional mapping between the propellant chemical composition and the motor design and the resulting spectral irradiance measured in a section of the plume. This functional mapping effectively models the relationship between the rocket design and the plume spectral radiance. Two datasets were available for use in this study: Emission spectra from solid propellant rockets and flare emission spectra. In the case of the solid rocket propellants, the input to the network consisted of the chemical composition of the fuels and four motor parameters, with the output of the network consisting of 146 scaled emission spectra points in the waveband from 2-5 microns. The four motor parameters were derived from equations describing the mass flow characteristics of rocket motors. The mass flow through the rocket motor does have an effect on the shape of the plume of combustion gases, which in turn has an effect on the infrared signature of the plume. The characteristics of the mass flow through the nozzle of the rocket motor determine the thermodynamic properties of the combustion process. This then influences the kind of chemical species found in the plume and also at what temperature these species are radiating energy.The resultant function describing the plume signature is: Plume signature f {p T A fuel composition} t , , , , 1 1 = ε It was demonstrated that this approach yielded very useful results. Using only 18 basic variables, the spectra were predicted properly for variations in all these parameters. The model also predicted spectra that agree with the underlying physical situation when changing the composition as a whole. By decreasing the Potassium content for example, the model demonstrated the effect of a flame suppressant on the radiance in this wavelength band by increasing the predicted output. Lowering the temperature, which drives the process of molecular vibration and translation, resulted in the expected lower output across the spectral band. In general, it was shown that only a small section of the large space of 2 propellant classes had to be measured in order to successfully generate a model that could predict emission spectra for other designs in those classes. The same principal was then applied to predicting the infrared spectral emission of a burning flare. The brick type flare considered in this study will ignite and the solid fuel will burn on all surfaces. Since there are no physical parameters influencing the plume as in the case of the rocket nozzles it was required to search for parameters that could influence the flare plume. It was possible to calculate thermodynamic properties for the flare combustion process. These parameters were then reduced to 4 parameters, namely: the oxidant-fuel ratio, equilibrium temperature, the molar mass and the maximum combustion temperature. The input variables for the flares thus consisted of the chemical composition and 4 thermodynamic parameters described above. The network proposed previously was improved and optimised for a minimum number of variables in the system. The optimised network marginally improved on the pevious results (with the same data), but the training time involved was cut substantially. The same approach to the optimization of the network was again followed to determine the optimal network structure for predicting the flare emission spectra. The optimisation involved starting out with the simplest possible network construction and continuouslyincreasing the variables in the system until the solution predicted by the network was satisfactory. Once the structure of the network was determined it was possible to optimise the training algorithms to further improve the solution. In the case of the solid rocket propellant emission data it was felt that it would be important to be able to predict the chemical composition of the fuel and the motor parameters using the infrared emission spectra as input. This was done by simply reversing the optimised network and exchanging the inputs with the outputs. The results obtained from the reversed network accurately predicted the chemical composition and motor parameters on two different test sets. The predicted spectra of some of the solid propellant rocket test sets and flare test sets did not compare well with the expected values. This was due to the fact that these test sets were in a sparsely populated area of the variable space. These outliers are normally removed from training data, but in this case there wasn’t enough data to remove outliers. To obtain an indication of the strength of the correlation between the predicted and measured line spectra two parameters were used to test the correlation between two line spectra. The first parameter is the Pearson product moment of coefficient of correlation and gives an indication of how good the predicted line spectra followed the trend of the measured spectral lines. The second parameter measures the relative distance between a target and predicted spectral point. For both the solid propellants and the flares the correlation values was very close to 1, indicating a very good solution. Values for the two correlation parameters of a test set of the flares were 0.998 and 0.992. In order to verify the model it was necessary to prove that the solution yielded by the model is better than the average of the variable space. Three statistical tests were done consisting of the mean-squared-error test, T-test and Wilcoxon ranksum test. In all three cases the average of the variable space (static model) and the predicted values (Neural Network model) were compared to the measured values. For both the T-test and the Wilcoxon ranksum test the null hypothesis is rejected when t < -tα = 1.645 and then thealternative hypothesis is accepted, which states that the error of the NN model will be smaller than that of the static model. The mean squared error for the static model was 0.102 compared to the 0.0167 of the neural net, for a solid propellant rocket test set. A ttest was done on the same test set, yielding a value of –2.71, which is smaller than – 1.645, indicating that the NN model outperforms the static model. The Z value for this test set is Z = -11.9886, which is a much smaller than –1.645. The results from these statistical tests confirm that neural network is a valid conceptual model and the solutions yielded are unique.
AFRIKAANSE OPSOMMING: In ‘n vroeër studie is bewys hoe dit moontlik is om die spektrale irradiansie van ‘n vuurpyl se verbrandingspluim te voorspel vanaf slegs die dryfmiddelsamestelling en vuurpylmotoreienskappe. In die literatuur is daar min gepubliseer oor hierdie onderwerp. Dit wil voorkom asof meer deterministiese metodes gebruik word om die probleem op te los. Metodes soos CFD simulasies en statistiese analises word tans verkies om wyeband radiansie te voorspel gebaseer op perfekte swart ligaam teorie. ‘n Groot beperking van hierdie metodes is die feit dat die berekeninge kompleks is en baie lank neem om te voltooi. ‘n Alternatiewe benadering is gebruik, wat nie poog om al die nie-liniêre en komplekse verbande uit eerste beginsels op te los nie. ‘n Neurale netwerk is gebruik om ‘n funksionele verband te skep tussen die chemiese samestelling van die dryfmiddel, vuurpylmotor ontwerp en die spektrale irradiansie van die vuurpyl se pluim. Die funksionele verband kan nou effektief die afhanklikheid van die dryfmiddelsamestelling, vuurpylmotor ontwerp en die spektrale uitset modelleer. Twee datastelle was beskikbaar vir analise: Emissie spektra van vaste dryfmiddel vuurpyle en ook van vaste dryfmiddel fakkels. Die invoer tot die neurale netwerk van die vuurpyle het bestaan uit die chemiese samestelling van die dryfmiddel en 4 vuurpylmotor eienskappe. Die uitvoer van die netwerk het weer bestaan uit 146 spektrale irradiansie waardes in die golflengte band van 2-5μm. Die 4 vuurpylmotor eienskappe is afgelei uit massavloei teorie vir vuurpyl motors, aangesien die uitvloei van die produkgasse ‘n invloed op die pluim van die motor sal hê. Die massavloei het weer ‘n effek op die spektrale handtekening van die pluim. Die eienskappe van die massavloei deur die mondstuk van die vuurpylmotor bepaal die termodinamiese eienskappe van die verbrandingsproses. Die invloed op die verbrandingsproses bepaal weer watter tipe produkte gevorm word en by watter temperatuur hulle energie uitstraal. Die gevolg is dat ‘n funksie gedefinieer kan word wat die pluim beskryf.Pluim handtekening = f{, temperatuur, mondstuk keël grootte, vernouings verhouding van mondstuk, dryfmiddelsamestelling} Deur net 18 invoer nodes te gebruik kon die netwerk die irradiansie suksesvol voorspel met ‘n variansie in al die invoer waardes. Deur byvoorbeeld die Kalium inhoud van die dryfmiddel samestelling te verminder het die model die vermindering van ‘n vlam onderdrukker suksesvol nageboots deurdat die irradiansie ‘n hoër uitset gehad het. Die sensitiwiteit van die model is verder getoets deur die temperatuur in die verbrandingskamer te verlaag, met ‘n korrekte laer irradiansie uitset, as gevolg van die feit dat die temperatuur die molekulêre vibrasie en translasie beweging beheer. Dieselfde benadering is gebruik om die model te bou vir die voorspelling van die fakkels se infrarooi irradiansie. Anders as die vuurpylmotors vind die verbranding in die geval van die fakkels in die atmosfeer plaas. Dit was dus ook nodig om na die termodinamiese eienskappe van die fakkel verbranding te kyk. Verskeie parameters is bereken, maar 4 parameters, naamlik die brandstof-suurstof verhouding, temperatuur, molêre massa en die maksimum verbrandingstemperatuur, tesame met die dryfmiddel samestelling kon die irradiansie van die fakkels suskesvol voorspel. Die bestaande netwerk struktuur vir die vuurpylmotors is verbeter en geoptimiseer vir ‘n minimum hoeveelheid veranderlikes in die stelsel. Die geoptimiseerde netwerk het ‘n klein verbetering in die voorspellings getoon, maar die oplei het drasties afgeneem. Dieselfde benadering is gebruik om die optimale netwerk vir die fakkels te bepaal. Optimisering van die netwerk struktuur is bereik deur met die eenvoudigste struktuur te begin en die hoeveelheid veranderlikes te vermeerder totdat ‘n bevredigende oplossing gevind is. Na die struktuur van die netwerk bevestig is, kon die oordragfunksies op die nodes verder geoptimiseer word om die model verder te verbeter. Dit het verder geblyk dat dit moonlik is om die netwerk vir die vuurpylmotors om te draai sodat die irradiansie gebruik word om die dryfmiddel samestelling en motor eienskappe te voorspel. Die netwerk is eenvoudig omgedraai en die insette het die uitsette geword.Die resultate van die omgekeerde netwerk het bevestig dat dit wel moontlik is om die dryfmiddel samestelling en motor eienskappe te voorspel vanaf die irradiansie. Die voorspelde spektra van beide die vuurpylmotors en die fakkels het nie altyd goed gekorreleer met die gemete data nie. Van die spektra kom voor in ‘n lae digtheidsdeel van die veranderlike ruimte. Dit het tot gevolg gehad dat daar nie genoeg data vir opleiding van die netwerk in die omgewing van die toetsdata was nie. Hierdie data is eintlik uitlopers en moet verwyder word van die opleidingsdata, maar daar is alreeds nie genoeg data beskikbaar om die uitlopers te verwyder nie. Dit is nodig om te bepaal hoe goed die voorspelde data vergelyk met die gemete data. Twee parameters is gebruik om te bepaal hoe goed die data korreleer. Die eerste is die “Pearson product moment of coefficient of correlation”, wat ‘n goeie aanduiding gee van hoe goed die voorspelde waardes die gemete waardes se profiel volg. Die tweede parameter meet die relatiewe afstand tussen die teiken en die voorspelde waardes. Vir beide die vuurpylmotors en die fakkels het die toetsstelle ‘n korrelasiewaarde van baie na aan 1 gegee, wat ‘n goeie korrelasie is. Die waardes van die twee parameters vir een van die fakkel toetstelle was onderskeidelik 0.998 en 0.992. Die model is geverifieer deur te bepaal of die model ‘n beter oplossing bied as die gemiddeld van die veranderlike ruimte. Drie statistiese toetse is gedoen: “Mean-squarederror” toets, T-toets en ‘n “Wilcoxon ranksum” toets. In al drie gevalle word die gemiddelde van die veranderlike ruimte (statiese model) en die voorspelde waardes (Neurale netwerk model) teen die gemete waardes getoets. Vir beide die T-toets en die “Wilcoxon ranksum” toets word die nul hipotese verwerp indien t < ta = 1.645 en dan word die alternatiewe hipotese aanvaar, wat bepaal dat die fout van die neurale netwerk model kleiner is as die van die statiese model. Die “mean-squared-error” van die statiese model was 0.102, in vergelyking met 0.0167 van die neurale netwerk model vir ‘n vuurpylmotor toetsstel. ‘n T-toets is gedoen vir dieselfde toetsstel, met ‘n resultaat van-2.71, wat kleiner is as –1.645 en aandui dat die neurale netwerk model weereens beter presteer as die statiese model. Die Z waarde uit die “Wilcoxon ranksum” toets is Z=- 11.9886, wat baie kleiner is as –1.645. Die resultate van die statitiese toetse toon dat die neurale netwerk ‘n geldige model is en die oplossings van die model ook uniek is.

The stringent emission laws, the depletion of petroleum reserves and the relation of fuels with politics have forced the world to find alternatives to fossil fuels. Biodiesel is one of the biofuels which is renewable and environmentally friendly and can be used in diesel engines with little or no modifications. For the last two decades, many researchers have reported extensive work on the performance and emission characteristics of engines running with biodiesel during steady state operation. However, there are numbers of knowledge gaps that have been identified which include limited information on biodiesel physio-chemical properties and their effects on combustion behaviour and performance and emission characteristics of the engine. In this study after an exhaustive literature review, the following four research areas have been identified and investigated extensively using available numerical and experimental means. The initial focus was to investigate the most important properties of biodiesel such as density, viscosity and lower heating value using experimental and numerical techniques. The effects of biodiesel blend content on the physical properties were analysed. For each property, prediction models were developed and compared with current models available in literature. New density and viscosity prediction models were developed by considering the combined effect of biodiesel content and temperature. All the empirical models have showed a fair degree of accuracy in estimating the physical properties of biodiesel in comparison to the experimental results. Finally, the effects of density and viscosity on the fuel supply system were investigated. This system includes the fuel filter, fuel pump and the engine combustion chamber in which air-fuel mixing behaviour was studied numerically. These models can be used to understand the effects of changes in the physical properties of the fuel on the fuel supply system. In addition, the fuel supply system analysis can be carried out during the design stage of fuel pump, fuel filter and injection system. The second research objective was the investigation into a CI engine’s combustion characteristics as well as performance and emissions characteristics under both the steady and transient conditions when fuelled with biodiesel blends. The effects of biodiesel content on the CI engine’s in-cylinder pressure, brake specific fuel consumption, thermal efficiency and emissions (CO2, NOx, CO, THC) were evaluated based on experimental results. It has been seen that the CI engine running with the biodiesel resulted in acceptable engine performance as well as reduction in main emissions (except NOx). Following this study, a detailed analysis on the transient performance and emission output of the CI engine has been carried out. During this analysis, the emission changing rate is investigated during speed transient and torque transition stages. Further to this, a transient emission prediction model has been developed using associated steady and transient emission data. The model has been shown to predict the transient emission reasonably accurately. The third research objective was to develop a method for on-line measurement of NOx emission. For this purpose the in-cylinder pressure generated within a CI engine has been measured experimentally along with mass air flow and these parameters have been used in the development of a NOx prediction model. This model has been validated using experimental data obtained from a NOx emission analyzer. The predicted data obtained from NOx prediction model has been compared with measured data and has shown that the deviation is within acceptable range. The final research objective was to develop a simple, reliable and low-cost novel method to reduce the NOx emission of the CI engine when using biodiesel blends. A potential solution to this problem has been found to be in the form of direct water injection which has shown to be capable to reduce NOx emission. Using a water injection technique, the performance and emission(NOx and CO) characteristics of a CI engine fuelled with biodiesel has been investigated at varying water injection flow rates. Intake manifold water injection reduces NOx emission by up to 40% over the entire operating range without compromising the performance characteristics of the CI engine

In recent years, extensive studies on alternative fuels have been conducted to find environmentally friendly, economically feasible fuels due to finite petroleum sources, environmental and economical reasons. In this thesis, effects of alternative fuels on engine performance and exhaust emission are studied experimentally. Cold and reacting tests have been performed. Volumetric flow rate, discharge pressure are measured according to different pump speed. Droplet diameters, droplet distribution, spray cone angle and two dimensional velocity distribution from combustor fuel nozzle are determined by IPI and PIV technique. The comparative performance of alternative fuels and JET A-1 are investigated by atmospheric combustion tests and experimental turbojet tests in terms of exhaust gas temperatures, emissions, combustion chamber efficiency. Emissions, combustion chamber exit temperature profile, power turbine inlet and exhaust gas temperatures, effects of fuels on engine performance are observed and measured in detail at RR Allison 250 C-18 turbo-shaft engine.

It is of nearly universal acceptance that one of the pillars of American economic success over the course of the 20th century was the rapid development of infrastructure. Transportation infrastructure has been of particular importance in the rise of the United States and attributed to the spread of an increasingly mobile culture. Americans undoubtedly enjoy traveling, and the ability to do so with relative ease is of immense value to many. In Texas, the majority of economic activity takes place within what is colloquially known as the “Texas Triangle”, an area bounded by the large metropolitan areas of Houston, Dallas-Ft. Worth, and San Antonio. Intensive population growth in Texas, anchored by the triangle, has led to increasing road congestion on many routes, especially along Interstates 35 and 10. This congestion, and the wasted time and money that comes with it, are of increasing concern to the future economic vitality of the state. The Texas Triangle is also served by extensive aviation links via major airports in the major metropolitan areas, as well as smaller airports in other parts of the region. These flights, operated by American Airlines, Continental Airlines, and Southwest Airlines are frequent, but emit large amounts of greenhouse gases that contribute to ground level pollution and possibly climate change. High-speed rail has been considered by many to be a superior environmental option for intercity routes with lengths inherent to the Texas Triangle. However, given the fact that Texas is the top emitter of carbon dioxide in the U.S. and relies on an energy mix that is primarily fossil fuel powered; would a potential high-speed rail in Texas outperform the current air system environmentally, given similar passenger miles traveled? This report examines the environmental emissions of high-speed rail and compares it to the environmental emissions of our current aviation system, taking into account a life-cycle perspective.
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