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Статті в журналах з теми "Alternate gas flows":
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Tyagi, Asha, Vineeta Venkateswaran, Ajai Kumar Jain, and Uttam Chandra Verma. "Cost Analysis of Three Techniques of Administering Sevoflurane." Anesthesiology Research and Practice 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/459432.
Анотація:
Background. This study aimed to evaluate and compare total cost of sevoflurane and propofol for 1.0 MAC-hour of anaesthesia, employing three anaesthetic techniques.Methods. Adult patients scheduled for surgical procedures under general anaesthesia anticipated to last approximately an hour were randomized into three groups (n=15each), to receive anaesthesia using one of the following techniques: low flow technique involving induction with propofol, followed by sevoflurane delivered using initial fresh gas flows of 6 L/min till MAC reached 1.0 and then reduced to 0.5 L/min; alternate method of low flow entailing only a difference in fresh gas flow rates being maintained at 1 L/min throughout; the third technique involving use of sevoflurane for both induction and maintenance of anaesthesia.Results. Cost of sevoflurane to maintain 1 MAC-hour of anaesthesia was clinically least with low flow anaesthesia, though statistically similar amongst the three techniques. Once the cost of propofol used for induction in two of the three groups was added to that of sevoflurane, cost incurred was least with the technique using sevoflurane both for induction and maintenance of anaesthesia, as compared to low flow and alternative low flow techniques, a 26% and 32% cost saving, respectively (P<0.05).
2
Dhanasekaran, C., and G. Mohankumar. "Hydrogen Gas in Diesel Engine Using DEE as Ignition Source." Applied Mechanics and Materials 591 (July 2014): 150–54. http://dx.doi.org/10.4028/www.scientific.net/amm.591.150.
Анотація:
Over the past two decades considerable effort has been taken to develop and introduce new alternate source of energy for the conventional gasoline and diesel. Environmental pollution and uncertainty in cost of petroleum products are the principal driving forces for this movement. The major pollutants from an Diesel engine system are NOx, Smoke, particulate matter, Soot. Several alternative fuels were tried but all of them are carbon based fuels, therefore net carbon based pollutants cannot be reduced. One alternative to carbon-based fuels is hydrogen. Hydrogen a non-carbon fuel only can meet zero emission vehicles standards in future. Hydrogen can be commercially used as a fuel even though it is having a number of technical and economical barriers. Numerous techniques are available for use in C.I. engine such as dual fuel made, by using spark plug, glow plug, DEE as an ignition enhancer. Hydrogen was used in a diesel engine in the dual fuel mode-using diesel as an ignition source in neat form using DEE. In neat form the DEE was introduced in the manifold. In order to have a precise control of hydrogen flow and to avoid the backfire and pre – ignition problems hydrogen was injection in to intake manifold; DEE injection follows the hydrogen injection. DEE mixed with air and flows into the combustion chamber as DEE auto ignites first followed by hydrogen combustion. A single cylinder-four stroke water-cooled naturally aspirated constant speed D.I. diesel engine with a rated output of 3.7 kW at 1500 rpm was used for the experimental purpose. Measurements were taken with respect to the performance, combustion and emission studies.
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LOMBARDINI, M., D. J. HILL, D. I. PULLIN, and D. I. MEIRON. "Atwood ratio dependence of Richtmyer–Meshkov flows under reshock conditions using large-eddy simulations." Journal of Fluid Mechanics 670 (February 1, 2011): 439–80. http://dx.doi.org/10.1017/s0022112010005367.
Анотація:
We study the shock-driven turbulent mixing that occurs when a perturbed planar density interface is impacted by a planar shock wave of moderate strength and subsequently reshocked. The present work is a systematic study of the influence of the relative molecular weights of the gases in the form of the initial Atwood ratio A. We investigate the cases A = ± 0.21, ±0.67 and ±0.87 that correspond to the realistic gas combinations air–CO2, air–SF6 and H2–air. A canonical, three-dimensional numerical experiment, using the large-eddy simulation technique with an explicit subgrid model, reproduces the interaction within a shock tube with an endwall where the incident shock Mach number is ~1.5 and the initial interface perturbation has a fixed dominant wavelength and a fixed amplitude-to-wavelength ratio ~0.1. For positive Atwood configurations, the reshock is followed by secondary waves in the form of alternate expansion and compression waves travelling between the endwall and the mixing zone. These reverberations are shown to intensify turbulent kinetic energy and dissipation across the mixing zone. In contrast, negative Atwood number configurations produce multiple secondary reshocks following the primary reshock, and their effect on the mixing region is less pronounced. As the magnitude of A is increased, the mixing zone tends to evolve less symmetrically. The mixing zone growth rate following the primary reshock approaches a linear evolution prior to the secondary wave interactions. When considering the full range of examined Atwood numbers, measurements of this growth rate do not agree well with predictions of existing analytic reshock models such as the model by Mikaelian (Physica D, vol. 36, 1989, p. 343). Accordingly, we propose an empirical formula and also a semi-analytical, impulsive model based on a diffuse-interface approach to describe the A-dependence of the post-reshock growth rate.
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Adkins, Bruce D., Zach Mills, James Parks II, M. Brennan Pecha, Peter N. Ciesielski, Kristiina Iisa, Calvin Mukarakate, et al. "Predicting thermal excursions during in situ oxidative regeneration of packed bed catalytic fast pyrolysis catalyst." Reaction Chemistry & Engineering 6, no. 5 (2021): 888–904. http://dx.doi.org/10.1039/d1re00007a.
Анотація:
Modelling quantifies thermal excursions when a conventional packed bed of coked catalyst is oxidatively decarbonized. The model can indicate when alternate designs, such as radial beds with high gas recycle or moving beds, should be considered.
5
Daya, Rohil, Christopher J. Keturakis, Dylan Trandal, Ashok Kumar, Saurabh Y. Joshi, and Aleksey Yezerets. "Alternate pathway for standard SCR on Cu-zeolites with gas-phase ammonia." Reaction Chemistry & Engineering 6, no. 6 (2021): 1042–52. http://dx.doi.org/10.1039/d1re00041a.
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Lim, Min Yee, Xinyue Zhang, Jian Huang, Liang Liu, Yutang Liu, Baixiao Zhao, Hui Hu, Furong He, Junjie Xie, and Dongsheng Qiu. "Study of Thermal Behavior of Moxa Floss Using Thermogravimetric and Pyrolysis-GC/MS Analyses." Evidence-Based Complementary and Alternative Medicine 2021 (February 16, 2021): 1–7. http://dx.doi.org/10.1155/2021/6298565.
Анотація:
Moxa floss is a type of biomass used as the main combustion material in moxibustion, a therapy that applies heat from moxa floss combustion to points or body areas for treatment. Safety concerns regarding moxa smoke have been raised in recent years. Since moxa floss is the source material in moxibustion, its thermal behavior and pyrolysis products would be related to the products formed in moxa smoke. This work aims to understand the thermal behavior of moxa floss and investigate the pyrolysis products generated from moxa floss combustion. Six commercial moxa floss samples of 3 storage years and 10 storage years, and of low, medium, and high ratios, were selected. The kinetic data from moxa floss combustion was carried out by a thermogravimetric analyzer. Pyrolysis-gas chromatography and mass spectroscopy using a gas chromatograph and mass spectrometer equipped with a pyroprobe were used to examine the pyrolysis products. Thermogravimetric profiles for all the samples were overall similar and showed a monotonic weight decrease. The range of intensive reaction temperature occurred between 150°C and 450°C, which was characterized by a major weight loss and accompanied by an exothermal degradation of the main components. The average ignition temperature for the samples of 3 and 10 storage years was 218.3°C and 222.6°C, respectively, which was lower than most herbaceous plants. The identified pyrolysis products include monocyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons, ketones, acids, and alkanes. All were of relatively low intensities of below 5% in relative abundance. No volatiles were detected in the samples of 10 storage years. The relatively low values of ignition temperature suggested that moxa floss is more combustible and can be ignited more easily than other herbaceous plants. This may explain why moxa floss has remained as the preferred material used for moxibustion over the years.
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Aquino, Andrea, Davide Picchi, and Pietro Poesio. "Modeling the motion of a Taylor bubble in a microchannel through a shear-thinning fluid." E3S Web of Conferences 312 (2021): 05006. http://dx.doi.org/10.1051/e3sconf/202131205006.
Анотація:
Applications of multiphase flows in microchannels as chemical and biological reactors and cooling systems for microelectronic devices typically present liquid slugs alternated with bubbles of elongated shape, the Taylor bubbles. These occupy almost entirely the cross-section of the channel and present a hemispherical front and a liquid layer, the lubrication film, which separates the gas from the tube wall. The Taylor bubble perturbs the surrounding fluids activating many transport mechanisms in the proximity of the gas-liquid interface; therefore, the bubble motion significantly influences the heat and mass transfer rates. Although many works deeply investigate the bubble hydrodynamics in Newtonian fluids, the knowledge about the relation between bubble hydrodynamics and rheological properties is insufficient, and studies where the continuous phase exhibits a shear-thinning behavior are missing. Our numerical analysis tries to fill this gap by investigating the motion of a Taylor bubble in a non-Newtonian shear-thinning fluid, modeled by the Carreau viscosity model. First, we validate the results against the Newtonian case and a recent theory for shear-thinning fluids (Picchi et al., Journal of Fluid Mechanics, 2021, 918). Then, we investigate the bubble hydrodynamics far from the validity range of the current models. Finally, we study the scaling of the bubble velocity and lubrication film thickness, extending the current theory to shear-thinning fluids.
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Dinesh Kumar Venkatesan, Vinayak Bhimsen Hemadri, Chinnapandian Marimuthu, and Khathanahalli Mathada Mrityunjayaswamy. "Esterified Papaya Oil and Flamboyant Oil as a Fuel on Single Cylinder Diesel Engine." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 99, no. 1 (October 17, 2022): 90–103. http://dx.doi.org/10.37934/arfmts.99.1.90103.
Анотація:
The future demand, increase in the price and environmental issues of fossil fuels necessitated the search of renewable alternate called biodiesel which reduces the dependence of fossil fuel import from other countries. The present research investigation outlines a detailed vision on the performance parameters and the exhaust characteristics of the methyl esters of papaya oil (POME) and flamboyant oil (FOME) and its blends on water cooled diesel engine comprising single cylinder running at 1500 rpm. The collected seeds are processed and found to contain oil percentage of 37% and 35% and they are esterified in a reactor to enhance its properties. From the result it is concluded that at maximum load, the blend B25 of papaya biodiesel accounted in better brake thermal efficiency than that of diesel with relatively less exhaust emission, such that the specific fuel consumption, brake thermal efficiency, exhaust gas temperature, smoke density, carbon monoxide emission, hydrocarbon emission and nitrous oxide emission are 0.27 kg/kW-hr, 31.46 %, 318°C, 49.02 Hsu, 0.095 %, 55 ppm and 988 ppm respectively.
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Trapeznikova, M. A., A. A. Chechina, and N. G. Churbanova. "Simulation of Vehicular Traffic using Macro- and Microscopic Models." Computational Mathematics and Information Technologies 7, no. 2 (July 13, 2023): 60–72. http://dx.doi.org/10.23947/2587-8999-2023-7-2-60-72.
Анотація:
To effectively regulate traffic on highways and networks of modern megacities, it is necessary to introduce Intelligent Transport Systems, which include many innovative solutions, in particular, mathematical models for describing the dynamics of traffic flows.The article is devoted to a brief description of the current state in this area in its development — from the simplest macroscopic and microscopic models that have become classic to modern developments.Special attention is paid to the original multilane models developed by the authors of the article within both approaches.The macroscopic model is based on the quasigasdynamic approach, while the microscopic one uses the ideology of cellular automata and constitutes a generalization of the Nagel-Schreckenberg model for the multilane case.The difference in the representation method and the mathematical apparatus for the mac-roscopic and microscopic description of traffic flows is briefly described, followed by the review of the main models at different stages of their development, presented by foreign and Russian authors.Special attention is paid to the three-phase theory of Boris Kerner and models built in the framework of this theory.Examples of modern software for traffic modeling are given.The original quasigasdynamic model of traffic flows, which uses the continuum approximation and is constructed by analogy with the well-known model of gas dynamics, is briefly described. Due to the introduction of the lateral speed, the model is generalized to the multilane case.An original microscopic model based on the cellular automata theory and representing a generalization of Nagel- Schreckenberg model for the multilane case is described. The model has been further developed by taking into account various driving strategies and behavioral aspects.The article presents a brief overview of the state of the art in the field of mathematical modeling of traffic flows, as well as original macroscopic and microscopic models developed by the authors for the case of multilane traffic.
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Prashantha, B. G., D. R. Swamy, Bhimasen Soragaon, and T. S. Nanjundeswaraswamy. "Design Optimization and Analysis of Thermoacoustic Refrigerators." International Journal of Air-Conditioning and Refrigeration 28, no. 03 (July 22, 2020): 2050020. http://dx.doi.org/10.1142/s2010132520500200.
Анотація:
Thermoacoustic refrigeration, a novel technology, uses eco-friendly gases like helium, air or the mixture of noble gases as working substances in the absence of moving parts. The design, optimization and analysis of thermoacoustic refrigerators using helium and air as oscillating gases are discussed. Pure helium is chosen since it is proven as the best and economical working gas compared to the alternate pure or the mixture of noble gases. Air is chosen since it is abundant in nature and the least cost of the pressurized dry air cylinders. The design optimization strategies discussed in this paper serve as a guide for aspiring researchers in the design and development of thermoacoustic coolers. Cooling power as a function of stack diameter is discussed. Theoretical results of the optimized coolers are compared with DeltaEC simulation results for validation and are in agreement with each other.
Дисертації з теми "Alternate gas flows":
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Kovchar, Jean. "Design, modeling, fabrication and characterization of a micro-device for the study of alternating flow - Application to energy harvesting and conversion." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCD009.
Анотація:
Cette thèse porte sur l'étude d'écoulements alternés au sein de canaux de dimensions milli- et sub-millimétriques. Ces travaux visent à contribuer à l'optimisation d'une machine miniature (dimensions sub-millimétriques) de récupération et de conversion d'énergie basse température (T < 200 °C) basée sur le principe du cycle de Stirling. Ceci s'inscrit dans le contexte de valorisation de la chaleur fatale encore non exploitée dans de nombreux milieux industriels. Dans les machines de type Stirling, les écoulements du fluide de travail sont alternés. Bien que ces écoulements soient assez bien connus à l’échelle macroscopique, ils le sont très peu à échelle milli et sub-millimétrique. Or une bonne compréhension de ce type d’écoulement à ces échelles est primordiale lors des phases de dimensionnement et design des machines. Afin de contribuer à la caractérisation des écoulement alternés à ces petites échelles, des canaux dont les dimensions sont proches de celles de la machine miniature ont été réalisés par des moyens technologiques de microfabrication au sein de la centrale technologique MIMENTO de l'Institut FEMTO-ST. Les canaux réalisés ont un diamètre hydraulique variant entre 200 µm et 1 mm, un rapport d'aspect compris entre 0.1 et 1 et deux longueurs de canal différentes (25 mm et 50 mm). Des canaux avec des coudes ont également été réalisés afin d'étudier leur influence sur les caractéristiques de l'écoulement. Ces canaux ont ensuite été implémentés sur le banc expérimental. Dans un premier temps, l'étude a porté sur la caractérisation des écoulements permanents, dans la gamme de Reynolds de 15 à 510, dont les résultats, en accord avec ceux issus de la littérature, ont servi de référence pour l'étude d'écoulements alternés, menée par la suite dans une gamme de nombres de Womersley allant de 0.02 à 0.67.La caractérisation des écoulements alternés a permis de déterminer que le rapport d'aspect et le diamètre hydraulique des canaux affectent significativement l'écoulement. En revanche, les travaux issus de cette thèse ont montré que l'influence de la longueur du canal ainsi que la présence de singularités (coudes) sur les caractéristiques de l'écoulement ne semblent pas être aussi déterminantes qu'attendu.Parmi les paramètres testés au cours de cette thèse, il a été montré que le rapport d'aspect et le diamètre hydraulique des canaux sont des paramètres importants à prendre en compte dans le design de micro machines de Stirling, notamment afin de ne pas impacter considérablement son efficacitéThis thesis focuses on the study of alternating flows within milli- and sub-millimeter-sized channels. The aim is to contribute to the optimization of a miniature (sub-millimeter dimensions) low-temperature (T < 200 °C) energy recovery and conversion machine based on the Stirling cycle principle. This is in line with the recovery of waste heat which is still not exploited in many industrial environments. In Stirling-type engines, the working fluid flows in alternating directions. Although these flows are fairly well understood on a macroscopic scale, very little is known about them on milli and sub-millimeter scales. However, a good understanding of this type of flow at these scales is essential for engine dimensioning and design. In order to contribute to the characterization of alternating flows at these small scales, channels with dimensions close to those of the miniature machine were produced using microfabrication technology. The channels produced have a hydraulic diameter ranging from 200 µm to 1 mm, an aspect ratio between 0.1 and 1, and two different channel lengths (25 mm and 50 mm). Channels with bends were also built to study their influence on flow characteristics. These channels were then implemented on the experimental bench. Initially, the study focused on the characterization of permanent flows, in the Reynolds range from 15 to 510, whose results, in agreement with those from the literature, served as a reference for the study of alternating flows, carried out in a second step with a Womersley number ranging from 0.02 to 0.67. The characterization of alternating flows has shown that the aspect ratio and the hydraulic diameter of the channels affect the flow significantly. On the other hand, this thesis has shown that the influence of channel length and the presence of singularities (bends) on the flow characteristics do not appear to be as decisive as expected. Consequently, among the parameters tested in this thesis, the aspect ratio and hydraulic diameter of the channels are important parameters to take into account for the design of the micro Stirling machine, especially to avoid impacting considerably its efficiency
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Gadiraju, Siddhartha. "Study of Lean Blowout Limits and Effects of Near Blowout Oscillations on Flow Field and Heat Transfer on Gas Turbine Combustor." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82480.
Анотація:
Modern gas turbine combustors implement lean premixed (LPM) combustion system to reduce the formation of NOx pollutants. LPM technology has advanced to have the ability to produce extremely low level of NOx emissions. The current focus of research on LPM is focused on reducing the NOx emission to much smaller scales, which is mandated because of the stricter regulations and environmental concerns. However, LPM combustors are susceptible to lean blowout (LBO), and other corresponding instabilities as the combustor is operated lean. Therefore, it is essential to understand the LBO limits and dynamics of flow in lean operating conditions. One of the other primary parameters for the improved combustion chamber designs is an accurate characterization of the heat loads on the liner walls in the wide range of operating conditions. Currently, there are very limited studies on the flame side heat transfer in reacting conditions. Current gas turbine combustion technology primarily focuses on burning natural gas as the gas fuel option for industrial systems. However, interest in utilizing additional options due to environmental regulations as well as concerns about energy security have motivated interest in using fuel gases that have blends of Methane, Propane, H2, CO, CO2, and N2. For example, fuel blends of 35%/60% to 55%/35% of CH4/CO2 are typically seen in Landfill gases. Syngas fuels are typically composed primarily of H2, CO, and N2. Gases from anaerobic digestion of sewage, used commonly in wastewater treatment plants, usually have 65–75% CH4 with the balance being N2.
The objective of this study is to understand the LBO limits and the effects of the instabilities that arise (called near blowout oscillations) as the combustor is operated lean. Near blowout oscillations arise as the equivalence ratio is reduced. These oscillations are characterized by continuous blowout and re-ignition events happening at low frequencies. The low-frequency oscillations have very high-pressure amplitude and can potentially damage the liner wall. The impact of the near blowout oscillations on the flow field and heat transfer on the liner walls are studied. To accomplish this, the experiments were conducted at Advanced Propulsion and Power laboratory located at Virginia Tech. A lean premixed, swirl stabilized fuel nozzle designed with central pilot hub was used for the study. Additionally, this work also studies the lean blowout limits with fuel blends of CH4-C3H8, CH4-CO2, and CH4-N2 and also their effect on the stability limits as the pilot fuel percentage was changed.
Flow field during near blowout oscillations was studied using planar particle image velocimetry (PIV) and flame shapes and locations during these oscillations was studied by using high-speed imaging of the flame. A statistical tool called proper orthogonal decomposition (POD) was utilized to post-process the PIV data and high-speed imaging data. Heat transfer on the liner walls was studied using a transient IR thermography methodology. The heat transfer on the liner wall during the near blowout instabilities was resolved. LBO limits and near blowout oscillations were characterized by studying the pressure measurements in the primary combustor region.
Fluctuating heat loads on the liner walls with the same frequency as that of near blowout instabilities was observed. The magnitude of fluctuation was found to be very high. Phase sorted POD reconstructed flame images demonstrated the location of the flame during near blowout oscillations. Thus, blowout and re-ignition events are resolved from the high-speed flame images. POD reconstructed flow field from the PIV data demonstrated the statistically significant flow structures during near blowout oscillations. A hypothesis for the mechanism of near blowout oscillations was explained based on the measurements and observations made.
Lean Blowout limits (LBO) changed when the percentage of pilot and air flow rates was changed. As the pilot percentage increased, LBO limits improved. Results on the study of fuel mixtures demonstrate that the addition of propane, nitrogen and carbon dioxide has minimal effect on when the flame becomes unstable in lean operating conditions. However, on the other hand, the addition of diluent gas showed a potential blowout at higher operating conditions. It was also observed that Wobbe index might not be a good representation for fuels to study the fuel interchangeability in lean operating conditions.Ph. D.
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Lotfollahi, Sohi Mohammad. "Development of a four-phase flow simulator to model hybrid gas/chemical EOR processes." Thesis, 2015. http://hdl.handle.net/2152/30530.
Анотація:
Hybrid gas/chemical Enhanced Oil Recovery (EOR) methods are such novel techniques to increase oil production and oil recovery efficiency. Gas flooding using carbon dioxide, nitrogen, flue gas, and enriched natural gas produce more oil from the reservoirs by channeling gas into previously by-passed areas. Surfactant flooding can recover trapped oil by reducing the interfacial tension between oil and water phases. Hybrid gas/chemical EOR methods benefit from using both chemical and gas flooding. In hybrid gas/chemical EOR processes, surfactant solution is injected with gas during low-tension-gas or foam flooding. Polymer solution can also be injected alternatively with gas to improve the gas volumetric sweep efficiency.
Most fundamentally, wide applications of hybrid gas/chemical processes are limited due to uncertainties in reservoir characterization and heterogeneity, due to the lack of understanding of the process and consequently lack of a predictive reservoir simulator to mechanistically model the process. Without a reliable simulator, built on mechanisms determined in the laboratory, promising field candidates cannot be identified in advance nor can process performance be optimized.
In this research, UTCHEM was modified to model four-phase water, oil, microemulsion, and gas phases to simulate and interpret chemical EOR processes including free and/or solution gas. We coupled the black-oil model for water/oil/gas equilibrium with microemulsion phase behavior model through a new approach. Four-phase fluid properties, relative permeability, and capillary pressure were developed and implemented. The mass conservation equation was solved for total volumetric concentration of each component at standard conditions and pressure equation was derived for both saturated and undersaturated PVT conditions.
To model foam flow in porous media, comprehensive research was performed comparing capabilities and limitations of implicit texture (IT) and population-balance (PB) foam models. Dimensionless foam bubble density was defined in IT models to derive explicitly the foam-coalescence-rate function in these models. Results showed that each of the IT models examined was equivalent to the LE formulation of a population-balance model with a lamella-destruction function that increased abruptly in the vicinity of the limiting capillary pressure, as in current population-balance models. Foam models were incorporated in UTCHEM to model low-tension-gas and foam flow processes in laboratory and field scales.
The modified UTCEM reservoir simulator was used to history match published low-tension-gas and foam coreflood experiments. The simulations were also extended to model and evaluate hybrid gas/chemical EOR methods in field scales. Simulation results indicated a well-designed low-tension-gas flooding has the potential to recover the trapped oil where foam provides mobility control during surfactant and surfactant-alkaline flooding in reservoirs with very low permeability.text
Книги з теми "Alternate gas flows":
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White, Nick. Evaluation of alternative dispenser meters: Final report. [Toronto, ON: Gas Technology Canada, 1999.
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Center, Langley Research, ed. An alternative to unstructured grids for computing gas dynamic flows around arbitrarily complex two-dimensional bodies. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1992.
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National Aeronautics and Space Administration (NASA) Staff. Alternative to Unstructured Grids for Computing Gas Dynamic Flows Around Arbitrarily Complex Two-Dimensional Bodies. Independently Published, 2018.
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Lee, Jan Hau, and Ira M. Cheifetz. Respiratory Failure and Mechanical Ventilation. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199918027.003.0006.
Анотація:
This chapter on respiratory failure and mechanical ventilation provides essential information about how to support children with severe respiratory disorders. The authors discuss multiple modes of respiratory support, including high-flow nasal cannula oxygen, noninvasive ventilation with continuous positive airway pressure and bilevel positive airway pressure, as well as conventional, high-frequency, and alternative modes of invasive ventilation. The section on invasive mechanical ventilation includes key information regarding gas exchange goals, modes of ventilation, patient–ventilator interactions, ventilator parameters (including tidal volume, end-expiratory pressure, and peak plateau pressure), extubation readiness testing, and troubleshooting. The authors also provide the new consensus definition of pediatric acute respiratory distress syndrome. Also included are multiple figures and indispensable information on adjunctive therapies (inhaled nitric oxide, surfactant, prone positioning, and corticosteroids) and respiratory monitoring (including capnography and airway graphics analysis).
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Schmeink, Lars. Individuality, Choice, and Genetic Manipulation. Liverpool University Press, 2017. http://dx.doi.org/10.5949/liverpool/9781781383766.003.0005.
Анотація:
Chapter 5 deals with the personal consequences of a posthuman subjectivity and the task of identity creation. In liquid modernity, risks and threats are becoming ever more global but remain systemic, while at the same time the solutions to these issues is relegated to the individual. The existence of a noticeable gap between society's insistence on individuality, autonomy, and self-assertion and the systemic risks to this claim, caused by a globalized flow of information, technology and politics, is thus the argument of the analysis of the video game BioShock. Science fiction as a genre here allows for the extrapolation and exaggeration of this gap by employing the posthuman as an extreme possibility of human identity creation. The dystopian imagination provides a bleak emphasis of the science-fictional dimension of consequence in terms of this development, by providing an alternative history in which rampant individualism meets an extreme form of consumer society. The human body has become the battleground of liquid modern desires to form and consume identities. Further, the medium uniquely provides the specific ideological commentary on the systemic nature of the illusion of autonomy, especially in liquid modern consumer society.
Частини книг з теми "Alternate gas flows":
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Pope, Kevin, and Greg F. Naterer. "Power Curves and Turbulent Flow Characteristics of Vertical Axis Wind Turbines." In Alternative Energy and Shale Gas Encyclopedia, 104–15. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119066354.ch9.
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Hurmekoski, Elias, Jyri Seppälä, Antti Kilpeläinen, and Janni Kunttu. "Contribution of Wood-Based Products to Climate Change Mitigation." In Forest Bioeconomy and Climate Change, 129–49. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99206-4_7.
Анотація:
AbstractForest-based products––often referred to as harvested-wood products (HWPs)––can influence the climate through two separate mechanisms. Firstly, when wood is harvested from forests, the carbon contained in the wood is stored in the HWP for months to decades. If the amount of wood entering the market exceeds the amount of wood being discarded annually, this can lead to a HWP sink impact. Secondly, HWPs typically have a lower fossil carbon footprint than alternative products, so, for example, using wood in construction can lower fossil emissions by reducing the production of cement and steel, resulting in a substitution impact. The international greenhouse gas (GHG) reporting conventions and the related Intergovernmental Panel on Climate Change guidance covers the HWP sink impact, but not the substitution impacts. The HWP sink impact is restricted to tracing biogenic carbon flows, whereas the substitution impact typically covers fossil carbon flows exclusively. Importantly, the substitution and HWP sink impacts do not represent the climate- change mitigation impact of wood use, as such. Instead, they are important pieces of the broader puzzle of GHG flows related to the forest sector. This chapter presents the state-of-the-art approaches for determining the HWP sink and substitution impacts, and concludes with the policy and research implications.
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Faleh, Salha, and Tahar Khir. "SOFC-Gas Turbine Hybrid Power Plant: Exergetic Study." In Rotating Machines [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103002.
Анотація:
The combined solid oxide fuel cells and gas turbine hybrid system is known to be a promise alternative for power generation with high efficiency. This paper presents the third part of the parametric study of a Solid Oxide Fuel Cell/Gas Turbine (SOFC/GT) hybrid system generating 120 MW Net power. The studied parameters are Pressure P, pre-reformed fraction Xr, extraction fraction fs, H2 flow, and air flow. Their effects on the performances of SOFC-GT hybrid system are investigated. The Engineering Equations Solver (EES) simulation is established to analyze the SOFC-GT exergetic and energetic system performances. The results show that increasing the air and fuel flows enhance system exergy. In contrary, the pressure at the SOFC and the extraction fraction negatively affects the exergy performance of the hybrid plant. It is also found that the combustion chamber, pre-reformer, and SOFC represent the greatest exergy destroyers.
4
Bird, G. A. "General Issues Related To Direct Simulations." In Molecular Gas Dynamics And The Direct Simulation Of Gas Flows, 208–17. Oxford University PressOxford, 1994. http://dx.doi.org/10.1093/oso/9780198561958.003.0010.
Анотація:
Abstract The remaining chapters of this book are concerned with the detailed procedures of the DSMC method, the implementation of these procedures through demonstration programs, and the verification and illustration of the method through the results from these programs. The recommended DSMC procedures have evolved over a considerable period of time and this developmental process will continue. Alternative procedures are available for most aspects of the simulation, and there may be some argument over the best choice for particular applications. The issues that relate directly to the procedures will be dealt with as they arise in the chapters that follow. However, there are a number of general issues that are relevant to all direct simulation methods, and these are best discussed prior to the presentation and implementation of the DSMC algorithms.
5
Quirk, James J. "A cartesian grid scheme for gas dynamic flows that involve complex geometries." In Numerical Methods for Fluid Dynamics, 385–92. Oxford University PressOxford, 1994. http://dx.doi.org/10.1093/oso/9780198536963.003.0031.
Анотація:
Abstract The desire to simulate flows around geometrically complex bodies has led many members of the shock capturing community to abandon schemes which employ body-fitted grids in favour of schemes which employ unstructured meshes. Now such is the success of unstructured grids, there is a danger that they will become de rigueur. Given the ever increasing reliance placed on computational results, such a state of affairs would give cause for some concern. If nothing else, the exercise of using several computer codes to cross check numerical results becomes ill-founded if all codes follow the same methodology. In this paper we outline an alternative approach for dealing with complex two-dimensional geometries, the so-called cartesian boundary method; solid bodies blank out areas of a background cartesian mesh and the cut cells which arise along solid boundaries are singled out for special treatment during the integration of the discretized flow solution.
6
Lighton, John R. B. "Flow-through Respirometry: Incurrent Flow Measurement." In Measuring Metabolic Rates, 101–15. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198830399.003.0010.
Анотація:
This chapter describes the setup, plumbing, and equations required for applying a respirometry system wherein the flow rate of the air entering the animal chamber is known. Such systems are usually referred to as push systems, because the air is usually pushed into a sealed respirometer chamber at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal push mode respirometry systems and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are also discussed.
7
Ghasem, Nayef Mohamed, Nihmiya Abdul Rahim, and Mohamed Al-Marzouqi. "Carbon Capture From Natural Gas via Polymeric Membranes." In Advances in Environmental Engineering and Green Technologies, 117–31. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-7359-3.ch009.
Анотація:
Polymeric membrane is a promising energy and an active alternative for conventional CO2 absorption column. The type of absorption liquid and operating parameters plays an efficient role in the ultimate absorption/stripping performance using gas-liquid membrane contactor. The gas flow rate has a significant effect on CO2 absorption performance; by contrast, it has no effect on stripping performance. Further, the CO2 absorption performance in membrane contactor could be enhanced by high liquid flow rates. The gas-liquid contact time was a key factor in enhancing the stripping flux at low temperature while liquid phase boundary layer thickness and associated mass transfer resistance is important at elevated temperature. By controlling the liquid phase velocity and the length of module at low temperature, better stripping performance can be achieved. The effect of liquid temperature on absorption performance in gas-liquid is not straightforward, since the liquid temperature cooperatively influences several factors.
8
Lighton, John R. B. "Flow-through Respirometry: Excurrent Flow Measurement." In Measuring Metabolic Rates, 116–23. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198830399.003.0011.
Анотація:
This chapter describes the setup, plumbing, and equations for implementing a respirometry system wherein the flow rate of the air leaving the animal chamber is known. Such systems are usually referred to as pull systems, because the air is usually pulled from a chamber or mask at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Such systems are often the only practical way of measuring the metabolic rates of large animals. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal pull mode respirometry systems, for compensating flow rate, and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are discussed.
9
Ghasem, Nayef Mohamed, Nihmiya Abdul Rahim, and Mohamed Al-Marzouqi. "Carbon Capture From Natural Gas via Polymeric Membranes." In Encyclopedia of Information Science and Technology, Fourth Edition, 3043–55. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-2255-3.ch266.
Анотація:
Polymeric membrane is a promising energy effective and an active alternative for conventional CO2 absorption column. The type of absorption liquid and operating parameters plays an efficient role in the ultimate absorption/stripping performance using gas-liquid membrane contactor. The gas flow rate has a significant effect on CO2 absorption performance, by contrast, it has no effect on stripping performance. Further the CO2 absorption performance in membrane contactor could be enhanced by high liquid flow rates. Because the gas–liquid contact time was a key factor to enhance the stripping flux at low temperature while liquid phase boundary layer thickness and associated mass transfer resistance is important at elevated temperature. So by controlling the liquid phase velocity and the length of module at low temperature better stripping performance can be achieved. The effect of liquid temperature on absorption performance in gas-liquid is not straightforward, since the liquid temperature cooperatively influence several factors.
10
Buttrick, P., M. R. T. Ellicott, A. P. Grant, D. R. Maule, and N. S. Pyne. "On-line measurement of dissolved nitrogen, oxygen in beer." In European Brewery Convention, 597–605. Oxford University PressOxford, 1993. http://dx.doi.org/10.1093/oso/9780199634668.003.0067.
Анотація:
Abstract In the UK nitrogen is increasingly being added to filtered draught beer, to improve head performance. To facilitate control of the process of addition, an on-line gas chromatographic system, incorporating a novel sampling system, has been developed which has proved reliable in production use in measuring dissolved nitrogen (with an accuracy of± 1 mg/1) and oxygen. Two alternative systems were also evaluated. Both were based on gas separation foll_owed by thermal conductivity measurements. One was off-line and gave variable results, possibly due to the complication of the sampling system. The other was in-line and shows considerable promise once problems of flow variation are overcome.
Тези доповідей конференцій з теми "Alternate gas flows":
1
Bachalo, W. D., A. Brẽna De La Rosa, and R. C. Rudoff. "Diagnostics Development for Spray Characterization in Complex Turbulent Flows." In ASME 1988 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1988. http://dx.doi.org/10.1115/88-gt-241.
Анотація:
The present work reports a detailed investigation of air-liquid interaction in sprays along with particle number density and mass flux measurements in complex turbulent flows such as those present in gas turbines and rocket combustors. Data have been obtained for the characterization of sprays in complex flows which include detailed drop size and drop velocity distributions, size-velocity correlations, mass flux, and particle number density. Key factors affecting the measurement of the sample volume size are discussed in detail since an accurate estimation of it is essential to the particle number density and volume flux determined by the instrument. The discrimination of refraction and reflective scattering components and their influence on the measurements is also discussed. Data comparing the phase Doppler results to alternate methods of measuring number density and volume flux are also presented. These results showed agreement to within 15% in most cases for realistic flow configurations.
2
Croquer, Sergio, Joaquin Vieiro, Carlos Chacon, and Miguel Asuaje. "CFD Multi-Phase Flow Analysis Across Diverging Manifolds: Application in the Oil-Gas Industry." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-36681.
Анотація:
This investigation assessed detailed characteristics of flow in diverging manifolds, for water and water-oil cases. A 3D Computational Fluid Dynamics (CFD) model of a distributing manifold was carried out. Numerical results showed good agreement with experimental values. Predicted pressure and velocity contours agree with theory, detailed 3D insight on present secondary flows and localized hydraulic losses was obtained, as well as effect on distribution of phases. Moreover, a 3D, multi-phase (oil-water) CFD model of a diverging manifold design, similar to those installed in separation units was conducted. The main pipe had 0.762 m (30 in) in diameter and 24 m in length, with 8 perforated pipes branching out. Branches had 0.305 m (12 in) in diameter and 12 m in length, with 312 holes per branch. Non-uniform outflow distributions were detected, as well as secondary flows. An alternate design was proposed. Numerical results show the new manifold design achieves uniform static pressure distribution across the entire main pipe, reducing secondary flows and hydraulic losses. Outflow distribution is also uniform, thus improving the performance of the separation unit.
3
Hwang, Jenn-Jiang. "Heat Transfer-Friction Characteristic Comparison in Rectangular Channel Arrays of Attached, Detached, and Alternate Attached-Detached Ribs on Two Opposite Walls." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-488.
Анотація:
Experiments are conducted to study the effect of three types of rib-arrays, namely composite, fully-attached, and fully-detached ribs, on friction factors and center-line heat transfer coefficients in rectangular channels. Two opposite walls are roughened by alternate attached and detached in-line rib-arrays for the composite ribs. The Reynolds number (Re) based on channel hydraulic diameter ranges from 12,000 to 70,000; whereas the rib pitch-to-height ratio varies from 10 to 30. The rib-to-channel height ratio (or rib height-to-channel hydraulic diameter ratio), and the ratio of the rib clearance to height are fixed at h/2B = 0.2 (h/De = 0.125), and c/h = 0.5, respectively, with a channel aspect ratio (W/B) of 4.0. It takes a longer distance from the channel inlet to set the local heat transfer coefficient into a periodic constant-value distribution for the composite-ribbed wall due to the more complex turbulent transportation. In the fully developed flows, the composite rib-roughened wall yields the highest heat transfer augmentation, and gives moderate pressure-drop penalty among the three types of ribbed walls. Performance evaluation under the constant pumping-power constraint reveals that the composite-ribbed channel performs best of the three ribbed arrangements. Semi-empirical correlations for friction and heat transfer in composite-ribbed channels are developed to account for rib spacing and Reynolds number for the design of gas turbine blade cooling passages.
4
Schlüter, Jörg, Thilo Schönfeld, Thierry Poinsot, Werner Krebs, and Stefan Hoffmann. "Characterization of Confined Swirl Flows Using Large Eddy Simulations." In ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0060.
Анотація:
Since the flame of high intense low NOx gas turbine combustion systems is stabilized by swirl, the analysis of the swirl flow is very crucial to the design and optimization of such combustion systems. Although a huge amount of publications have been provided on this field just a few have used Large Eddy Simulation due to limits in computer resources. Using Large Eddy Simulation the large vortical structure of the flow is resolved leading to a much better insight of the flow features. Hence, in this paper the Large Eddy Simulation has been applied to investigate the non reacting confined swirling flow downstream of a gas turbine burner. A high accuracy of the prediction of the full three dimensional simulation could be pointed out by comparison of the computational results to measurements. Further the large vortical structure and the dynamic behavior of the flow has been analyzed. The formation of a precessing vortex core is visualized. Due to the precessing motion of the central recirculation zone an alternate vortex shedding at the edges of the burner nozzle is induced. From LES Strouhal numbers for the vortex shedding process are calculated which are confirmed by hot wire measurements.
5
Menon, Rajan K. "Three Component Velocity Measurements in the Interblade Region of a Fan." In ASME 1987 International Gas Turbine Conference and Exhibition. American Society of Mechanical Engineers, 1987. http://dx.doi.org/10.1115/87-gt-207.
Анотація:
Optimizing aerodynamics and improving blade designs to make efficient power-generating machinery requires a good understanding of the rotor flow field. Swirl, flow instabilities, and high turbulence highlight the need for understanding the three-dimensional nature of the flow. Dynamic interaction between fluid and structural aspects in fluid machinery, impact of unsteady flows or loads, and enhancement of property transport can be studied through simultaneous measurement of three components of velocity. A three color, three component Laser Velocimeter System is used to simultaneously measure the three orthogonal components of velocity in the interblade region of a fan. The non-invasive nature of the technique combined with the very small measuring volume of the system provides detailed mapping of the flow field in the interblade region. The data acquisition package collects all the data available while the machine is running and sorts the raw data into bins corresponding to the various circumferential positions. Each velocity measurement — all three components — along with the circumferential position information is collected by a DEC PDP 11/23 Computer. The analysis package allows the user to examine a portion of the interblade region, look at alternate interblade gaps, omit data during blade passage, etc. Statistical properties such as mean, turbulence, skewness, flatness, Reynolds stress values, and projections in cross sectional planes are obtained and displayed as a function of circumferential position. Thus, the detailed properties of the three dimensional flow field are obtained from the three component LDV measurements.
6
Sabla, P. E., and G. G. Kutzko. "Combustion Characteristics of the GE LM2500 Combustor With Hydrogen-Carbon Monoxide-Based Low Btu Fuels." In ASME 1985 International Gas Turbine Conference and Exhibit. American Society of Mechanical Engineers, 1985. http://dx.doi.org/10.1115/85-gt-179.
Анотація:
An experimental test program was conducted with the objective of evaluating the combustion performance of fuel gases comprised of mixtures of carbon monoxide, hydrogen, and nitrogen. These gases were intended to be representative of alternate fuels that might be produced by air blown coal or biomass gasifiers. The purpose of this test program was to identify if the LM2500 combustion system would burn fuels at heating values (150 Btu/SCF – 250 Btu/SCF) typical of those produced by gasifier processes. Two combustor configurations were tested and two representative gas compositions were evaluated. The objectives of this test were to determine the flammability or burning limits for the two combustor designs and the impact of the low heating value gas on combustor exit temperature performance. Both designs exhibited burning limits substantially below the target caloric level. The exit temperature measurement showed the exit temperature distribution quality was adversely affected due to the high volumetric gas flows. However, this exit temperature distribution degradation is not severe enough to make the burning of a low heating value fuel prohibitive in the LM2500 engine.
7
Sondermann, Carina N., Rodrigo A. C. Patrício, Aline B. Figueiredo, Renan M. Baptista, Felipe B. F. Rachid, and Gustavo C. R. Bodstein. "Hyperbolicity Analysis of a One-Dimensional Two-Fluid Two-Phase Flow Model for Stratified-Flow Pattern." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51587.
Анотація:
Two-phase flows in pipelines occur in a variety of processes in the nuclear, petroleum and gas industries. Because of the practical importance of accurately predicting steady and unsteady flows along the line, one-dimensional two-fluid flow models have been extensively employed in numerical simulations. These models are usually written as a system of non-linear hyperbolic partial-differential equations, but some of the available formulations are physically inconsistent due to a loss of the hyperbolicity property. In these cases, the associated eigenvalues become complex numbers and the model loses physical meaning locally. This paper presents a numerical study of a one-dimensional single-pressure four-equation two-fluid model for an isothermal stratified flow that occurs in a horizontal pipeline. The diameter, pressure and volume fraction are kept constant, whereas the liquid and gas velocities are varied to cover the entire range of superficial velocities in the stratified region. For each point, the eigenvalues are numerically computed to verify whether they are real numbers and to assess their signs. The results show that hyperbolicity is lost near the boundaries of the stratified pattern and in a vast area of the region itself. Moreover, the eigenvalue signs alternate, which has implications on the prescription of numerical boundary conditions.
8
Fisher, Mark D., and George A. Davies. "Flow Analysis Helps Correct Underperformance of Combined Cycle Emissions Equipment." In ASME 2006 Power Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/power2006-88209.
Анотація:
Computational fluid dynamics analysis of the exhaust gas flow distribution in the inlet ductwork of a combined cycle power plant has helped improve both emissions performance as well as lowering plant operating costs. The Turlock Irrigation District Almond Power plant had recently installed an upgraded gas turbine (GT), and replaced both CO oxidation and selective catalytic control (SCR) NOx control catalysts in order to withstand the higher exhaust temperatures of the new gas turbine. After the retrofits, both NOx and CO emissions were within Permitted limits, but were above expected values, and operators found that overspray of ammonia was required to meet required NOx values of 3.0 ppmv at 15% O2. The need to overspray also resulted in unacceptably high levels of ammonia slip at the stack. Following investigations which included physical flow modeling of the ductwork, TID opted to have the exhaust gas flow numerically modeled to confirm the origin of the emissions problem and identify and implement a long-term resolution. Computational fluid dynamics (CFD) analyses confirmed that the cause of the poor emissions performance was highly biased gas flow distributions at the entrance to the CO catalyst modules and the ammonia injection grid (AIG). Using multiple models to evaluate alternate configurations of flow control devices, a single distribution grid located upstream of the CO catalyst modules was designed to provide improved flow distributions at both the CO catalyst, AIG, and SCR catalysts. Field tests of the plant with the installed distribution grid confirmed that the retrofit significantly improved emissions performance while reducing both required ammonia injection flows and ammonia slip values eight-fold. This not only allowed the plant to meet and exceed required emissions levels, but also reduced ammonia injection flow rates by a minimum of 40%. Additionally, the facility has seen an improvement in the plant’s effective operating range. This is the range at which the plant can operate and still maintain emissions compliance. Prior to the installation of the distribution grid the plant had an effective operating range of 30–50 MW. The plant now has an effective operating range of 20–50 MW. This is beneficial at times when the plant is operated in “load following” mode.
9
Pucher, G., and W. D. Allan. "Turbine Fuel Ignition and Combustion Facility for Extremely Low Temperature Conditions." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53620.
Анотація:
As the temperature of combustion air and fuels are reduced, the ability to achieve ignition within gas turbine engines becomes increasingly difficult. Several factors share responsibility, related largely to the physical characteristics of fuel emerging from nozzles, whereby an increasing fuel viscosity with temperature reduction results in larger average fuel droplets. The ensuing reduced surface area hinders fuel evaporation within an environment where evaporation is already impeded by low partial pressures due to low ambient temperature conditions and/or depending on the mode of operation, due to a high altitude environment. To study the effects of extremely low air and fuel temperatures on gas turbine fuel ignition performance, a dual mode (namely for cold start and altitude relight) test rig has been designed and commissioned. Its main components include a turbo-jet combustion chamber section, fuel system, ignition system, fuel/air cooling systems, and data acquisition/instrumentation. For airflow within the combustion chamber, two alternate sources are used, depending on the mode of operation. As such, this rig allows key parameters related to gas turbine ignition, such as fuel flow, fuel viscosity, ignition characteristics, airflow, and pressure conditions to be monitored and recorded. Highlights of this test rig include a General Electric J-85 combustion chamber section with quartz windows, fuel and air cooling via cryogenic liquids (LN2 for the fuel, LN2 and LOx for air), fuel and air closed loop temperature control, high speed data acquisition, a gas turbine exciter or, as selected, a custom programmable ignition system. Airflow is provided either by twin 11 HP blowers providing up to 0.5 kg/s of airflow to simulate sea level start conditions, or through the entrainment of high velocity air to simulate relight conditions at up to 21000 feet altitude. This rig is capable of achieving minimum inlet air temperatures and fuel temperatures lower than −45°C. A series of commissioning tests was undertaken with the rig in both ground start and altitude (low pressure) configurations. In order to study viscosity effects on ignition performance, two common gas turbine fuels were utilized, namely JP-4 (F-40) and JP-8 (F-34). Ignition fuel flows as well as lean blowout flows for a stock injector design are presented for these fuels across a matrix of fuel and air temperatures. Conclusions are drawn and future developments are described.
10
Poulsen, Christian V., Mikael Svalgaard, and Ove Poulsen. "Photosensitivity in germania-doped silica films." In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cmm5.
Анотація:
Integrated optics is believed to be the key technology for future integrated optical systems. One standard method for processing planar waveguides is a combination of plasma enhanced chemical vapor deposition (PECVD) for growing glass layers and photolithography/reactive ion etch (RIE) for creating the waveguides2 (Fig. la). We present an investigation of the photosensitivity of germania-doped silica films. The results may lead to an alternate method for creating the guiding structure in planar waveguides that requires much fewer process steps. Instead of using a combination of photolithography and RIE for defining the guiding core, the index change due to photosensitivity of germanium-doped silica may be utilized (Fig. 1b). To investigate the photosensitivity, germanium-doped silica films were grown on a 4" silicon wafer in a PECVD chamber. These films were fabricated at a temperature of 300°C, a base pressure of 700 mTorr, and gas flows of 17 seem silane, 1600 sccm nitrousdioxide and up to 8 sccm germane followed by annealing at 800°C in a nitrogen atmosphere for two hours.
Звіти організацій з теми "Alternate gas flows":
1
Wallis. L51614 Slug Frequency in Horizontal Gas-Liquid Flow. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), February 1990. http://dx.doi.org/10.55274/r0011058.
Анотація:
This report responds to A.G.A.s objective of initiating and planning means to create a reliable, mechanistic method of slug frequency prediction. Specific objectives were to: Update the prior review of existing knowledge Identify one or more alternative modelling approaches Recommend additional work if required Examination of empirical correlations for slug frequency shows that they have uncertainties which are large compared with experimental data. A mechanistic approach is sought. Previous mechanistic models have been either incomplete or numerically unstable. Several improvements were made to the Taitel-Dukler model for this process and a new calculation procedure developed using the method of characteristics. It is demonstrated here that this approach alone cannot lead to cyclic slug formation. The processes of wave growth continually wash out downstream without causing new slugs to form upstream. This has led to concentration on the mechanism of slug formation near the inlet to a pipe segment.
2
Bruce. L52282 State-of-the-Art Assessment of Alternative Casing Repair Methods. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 2007. http://dx.doi.org/10.55274/r0010195.
Анотація:
Many natural gas storage wells suffer damage during normal storage operations. Storage operators spend upwards of $100 million per year recovering lost deliverability. Damage to casings in gas storage wells is largely the result of localized loss of metal from corrosion; however, other types of damage do occur. Individual corrosion pits can be found either on the inside or outside of the casing wall. Repair methods that are currently used for natural gas storage well casings include patches, plugs, liners, etc. While currently-used repair methods can be a cost-effective means of repairing damaged casings as compared to the cost of running an entirely new casing, there is a need to identify and develop alternative casing repair methods that are more economical and/or do not have inherent operational disadvantages. Many of the current repair methods are proprietary, and as a result, are relatively costly to perform. In addition, many of these repair methods (e.g., tube and packer system repairs) result in a decreased cross-sectional area, which creates operational limitations due to flow restrictions and reduces the ability to perform well logging operations. The objective of this project was to review current state-of-the-art casing repair technologies to identify more cost effective alternatives. The most prominent form of underground U.S. gas storage is depleted reservoirs. American Petroleum Institute specification 5CT contains the industry standard design guidance for new casings; however, there are no industry standard repair procedures and each state has their own. The most common state required repair integrity test is pressure testing. Casings must withstand tensile, burst, and collapse loads. Most state repair procedures do not specify a target mechanical property that defines repair success. It is therefore easy to assume that a repair should return a casing back to its original integrity level; however, it may not be necessary. The major types of damage mechanisms are corrosion, threaded connection separation, sealant leaks, split casings, and drill bit damage. While a literature search indicated that the most commonly used types of cost effective repair processes are squeezes, liners, and plating, industry feedback indicated that liner repair is the most commonly used repair process. Adhesively bonded, helically-wound, steel strip repair and magnetic pulse welding are the most promising alternative repair technologies identified, mainly because both are applicable for a broad range of damage types and as an alternative to both traditional casing liner and expandable tubular repair technologies.
3
Choquette, Gary. PR-000-14216-R02 An Alternative to PID Control for Critical Control Functions. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2015. http://dx.doi.org/10.55274/r0010405.
Анотація:
Previous work identified cases where relatively minor changes in air manifold pressure led to engine detonation. This occurred under lean combustion conditions where detonation is believed to be unlikely. This indicates that it is as equally important to have stable engine control functions as it is to have the proper air/fuel setpoint. The objective of this work is to identify alternatives to conventional control techniques that can be employed on reciprocating engines used in the natural gas transpiration industry to enhance air/fuel control stability which in turn should improve combustion stability. The report identifies an alternate control method that adds symmetric/asymmetric dynamic integral control to the standard PID control method. While the example here is applied to reciprocating engine air/fuel control specifically, the control method can apply to many other complicated control methods such as surge control, flow control, temperature control, and pressure control. The report includes an example implementation for Allen-Bradley controlers using IEC 61131-3 Function Blocks.
4
Malinowski, Owen, Scott Riccardella, and Jason Van Velsor. PR-335-203810-R03 CT Fundamentals with Calibration and Reference Standards for Pipeline Anomaly Detection. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), March 2022. http://dx.doi.org/10.55274/r0012216.
Анотація:
X-ray Computed Tomography (XRCT) was initially developed and utilized in the medical industry to image the internal structure of the human body. X-ray imaging was conceived and realized at the turn of the 20th century and subsequently, XRCT, was conceived in the middle of the 20th century and its development continues today. Near the end of the 20th century industrial cone beam XRCT for applications such as dimensional metrology branched off, including its use for identifying and dimensioning flaws. XRCT has been utilized successfully for three-dimensional imaging of flaws in the small panel cut-outs from steel oil and gas transmission pipelines. However, the performance of XRCT on full-circumference pipe samples has not been assessed to determine if the technology can be used to obtain flaw dimensional information with the same accuracy that has been observed on panel cut-outs. This would enable the industry to generate full-circumference reference samples with well-characterize flaw dimensions, which would be much more practical and useful for qualification, certification, and validation of inline inspection and nondestructive examination tools, personnel, and procedures. This tasks for this project were to evaluate the state-of-the-art in XRCT technology, establish guidelines for XRCT scanning of pipeline samples, compare XRCT performance on artificial and natural flaws, and compare performance of lab-based and in-the-ditch XRCT technologies on artificial and natural flaws through scanning multiple samples utilizing multiple XRCT vendors and subsequently destructive testing the samples. The overall objective of the project was to determine if XRCT is a viable alternative to destructive testing for collecting "truth" data from flaw reference samples. Related webinar
5
Regan, Jack, Julie Bryant, and Craig Weinschenk. Analysis of the Coordination of Suppression and Ventilation in Single-Family Homes. UL Firefighter Safety Research Institute, March 2020. http://dx.doi.org/10.54206/102376/slzh7498.
Анотація:
Prior full-scale research with the fire service was primarily designed to isolate specific tactics, most often either ventilation or suppression, which allowed researchers to develop science-based recommendations related to the specific components of fireground operations studied in relatively controlled conditions. The current project went beyond earlier research by conducting twenty experiments in eight acquired, single-family residential structures and that combined fireground tactics to quantify the impact of coordination between ventilation and suppression actions. This experimental series included second-story bedroom fires (14 experiments) and first-floor kitchen fires (6 experiments). The main control variables studied included the position of initial application of water, the ventilation method, and the timing of ventilation relative to water application. The ventilation tactics examined in these experiments included horizontal, vertical, positive pressure, and hydraulic ventilation, while the suppression tactics included both interior water application and initial exterior water application followed by interior water application. While some elements of the experiments (e.g. structure floor plan and weather) resulted in increased variability, the lessons learned highlighted the importance of having a systematic approach to the implementation of tactics. Most importantly, there was no meaningful increase in temperature outside of fire rooms when ventilation tactics were executed in coordination with (shortly after or shortly before) the onset of suppression. The effectiveness of suppression actions in extinguishing the fire were dependent on the ability of those actions to 1) cool surfaces in the fire room and 2) wet unburned fuel. Exterior suppression actions on second-floor bedroom fires resulted in a decrease in temperatures throughout the second floor, followed by regrowth prior to final suppression through interior streams. When exterior suppression was performed on first-floor kitchen fires, where more complete fuel wetting was possible, regrowth was not observed prior to interior suppression. When surface cooling or fuel wetting are not possible due to the elevation of the fire room, missing ceiling, or obstacles, firefighters should consider alternative means of water distribution to improve the effectiveness of suppression actions from outside the fire room. Suppression actions, whether interior or exterior, generally resulted in a decrease in temperatures and gas concentrations at locations where occupants may potentially be located. Conditions improved most quickly at locations closest in proximity to the inlet of the flow path established between the front door and the fire room. For this reason, opening an exterior door to gain access should be thought of as an important ventilation action, both in terms of its potential to cause fire growth and its potential to improve conditions for potentially trapped occupants. After effective suppression, structure ventilation operations should similarly be cognizant of gas flows, with the aim of establishing flow throughout all areas where occupants may be located.
6
Moreda, Fekadu, Benjamin Lord, Mauro Nalesso, Pedro Coli Valdes Daussa, and Juliana Corrales. Hydro-BID: New Functionalities (Reservoir, Sediment and Groundwater Simulation Modules). Inter-American Development Bank, November 2016. http://dx.doi.org/10.18235/0009312.
Анотація:
The Inter-American Development Bank (IDB) provides financial and technicalsupport for infrastructure projects in water and sanitation, irrigation, flood control, transport, and energy, and for development projects in agriculture, urban systems, and natural resources. Many of these projects depend upon water resources and may be affected negatively by climate change and other developments that alter water availability, such as population growth and shifts in land use associated with urbanization, industrial growth, and agricultural practices. Assessing the potential for future changes in water availability is an important step toward ensuring that infrastructure and other development projects meet their operational, financial, and economic goals. It is also important to examine the implications of such projects for the future allocation of available water among competing users and uses to mitigate potential conflict and to ensure such projects are consistent with long-term regional development plans and preservation of essential ecosystem services. As part of its commitment to help member countries adapt to climate change, the IDB is sponsoring work to develop and apply the Regional Water Resources Simulation Model for Latin America and the Caribbean, an integrated suite of watershed modeling tools known as Hydro-BID. Hydro-BID is a highly scalable modeling system that includes hydrology and climate analysis modules to estimate the availability of surface water (stream flows) at the regional, basin, and sub-basin scales. The system includes modules for incorporating the effects of groundwater and reservoirs on surface water flows and for estimating sediment loading. Data produced by Hydro-BID are useful for water balance analysis, water allocation decisions, and economic analysis and decision support tools to help decision-makers make informed choices among alternative designs for infrastructure projects and alternative policies for water resources management. IDB sponsored the development of Hydro-BID and provides the software and basic training free of charge to authorized users; see hydrobidlac.org. The system was developed by RTI International as an adaptation of RTI's proprietary WaterFALL® modeling software, based on over 30 years of experience developing and using the U.S. National Hydrography Dataset (NHDPlus) in support to the U.S. Geological Survey and the U.S. Environmental Protection Agency. In Phase I of this effort, RTI prepared a working version of Hydro-BID that includes: (1) the Analytical Hydrography Dataset for Latin America and the Caribbean (LAC AHD), a digital representation of 229,300 catchments in Central America, South America, and the Caribbean with their corresponding topography, river, and stream segments; (2) a geographic information system (GIS)-based navigation tool to browse AHD catchments and streams with the capability of navigating upstream and downstream; (3) a user interface for specifying the area and period to be modeled and the period and location for which water availability will be simulated; (4) a climate data interface to obtain rainfall and temperature inputs for the area and period of interest; (5) a rainfall-runoff model based on the Generalized Watershed Loading Factor (GWLF) formulation; and (6) a routing scheme for quantifying time of travel and cumulative flow estimates across downstream catchments. Hydro-BID generates output in the form of daily time series of flow estimates for the selected location and period. The output can be summarized as a monthly time series at the user's discretion. In Phase II of this effort, RTI has prepared an updated version of Hydro-BID that includes (1) improvements to the user interface; (2) a module to simulate the effect of reservoirs on downstream flows; (3) a module to link Hydro-BID and groundwater models developed with MODFLOW and incorporate water exchanges between groundwater and surface water compartments into the simulation of sur
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Finch, Graeme, and Stuart Harmon. PR-670-183826-R02 Extended Evaluation of LSM - Magnetic Measurements of Corrosion Flaws. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), November 2021. http://dx.doi.org/10.55274/r0012189.
Анотація:
Integrity assessment of pipelines is vital to ensure that oil and gas pipes have adequate strength to prevent leaks and ruptures. Regular inspections are conducted to confirm safe operation conditions of pipelines. The industry's principle method for assessing pipelines is in-line inspection (ILI), involving the passing of a device along the inside of a pipe to assess the condition of the pipeline. ILI devices can be fitted with a number of sensors allowing various measurement parameters to be obtained simultaneously. Not all pipelines are suited to ILI for reasons such as small diameter, obstructions within the pipe, or insufficient access to deploy or retrieve the ILI tools. These pipelines are sometimes referred to as 'difficult to inspect'. Alternative methods for examining pipeline condition are required with a range of technologies collectively known as Large Standoff Magnetometry (LSM) offering a promising solution for detection of pipe defects from a distance, reducing the need for excavation. LSM utilises coupling between defects and changes in the magnetic properties of the pipeline material as a method for evaluation of pipe walls to identify the location of areas that require repair or further monitoring. Trials of existing commercial instruments by the pipeline industry have shown sufficient promise to investigate these technologies further. However, the vendors have supplied limited information on the underpinning physics of both the materials being tested and the instrument technology, meaning that further study is required in order to build confidence in the technique. The purpose of the project is to establish the ability of LSM to detect corrosion in API 5L pipe grades B to X70. The aim of Work Package 04 is to measure the magnetic fields of a range of pipe samples containing manufactured corrosion flaws taking into account variables such as standoff distance, pressure, nearby ferromagnetic objects, position of the corrosion flaw around the pipe, track alignment, and orientation with respect to Earth's magnetic field. The results of these measurements will be used to validate computational models, which can be used to predict the magnetic response of a wider range of pipe geometries.
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Michel, Bob, and Tatiana Falcão. Taxing Profits from International Maritime Shipping in Africa: Past, Present and Future of UN Model Article 8 (Alternative B). Institute of Development Studies (IDS), November 2021. http://dx.doi.org/10.19088/ictd.2021.023.
Анотація:
International maritime shipping is an essential part of global business. Since the establishment of the current international tax regime in the 1920s, there has been a consensus that profits generated by this business are taxable only in the residence state –the state where the shipowners are located. Source states – the port states where business physically takes place – are generally expected to exempt income from international shipping. This standard is currently reflected in Article 8 of the OECD Model and Article 8 (Alternative A) of the UN Model, and is incorporated in the vast majority of bilateral tax treaties currently in force. Exclusive residence state taxation of shipping profits is problematic when the size of mercantile fleets and shipping flows between two states are of unequal size. This is often the case in relations between a developed and developing country. The latter often lack a substantial domestic mercantile fleet, but serve as an important revenue-generating port state for the fleet of the developed country. To come to a more balanced allocation of taxing rights in such a case, a source taxation alternative has been inserted in UN Model Article 8 (Alternative B). From its inception, Article 8B has been labelled impractical due to the lack of guidance on core issues, like sourcing rules and profit allocation. This gap is said to explain the low adoption rate of Article 8B in global tax treaty practice. In reality, tax treaty practice regarding Article 8B is heavily concentrated and flourishing in a handful of countries in South/South-East Asia – Bangladesh, India, Indonesia, Myanmar, Pakistan, the Philippines, Sri Lanka and Thailand. All these countries subject non-resident shipping income to tax in their domestic income tax laws. Except for India, all countries are able to exercise these domestic tax law rules in relation to shipping enterprises located in the biggest shipowner states, either because they have a treaty in place that provides for source taxation or because there is no treaty at all and thus no restriction of domestic law. None of the relevant tax treaties contain a provision that incorporates the exact wording of Article 8B of the UN Model. If other countries, like coastal countries in sub-Saharan Africa, are looking to implement source taxation of maritime shipping income in the future, they are advised to draw on the South/South-East Asian experience. Best practice can be distilled regarding sourcing rule, source tax limitation, profit attribution and method of taxation (on gross or net basis). In addition to technical guidance on tax, the South/South-East Asian experience also provides important general policy considerations countries should take into account when determining whether source taxation of maritime shipping profits is an appropriate target for their future tax treaty negotiations.
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Videa, Aldo, and Yiyi Wang. Inference of Transit Passenger Counts and Waiting Time Using Wi-Fi Signals. Western Transportation Institute, August 2021. http://dx.doi.org/10.15788/1715288737.
Анотація:
Passenger data such as real-time origin-destination (OD) flows and waiting times are central to planning public transportation services and improving visitor experience. This project explored the use of Internet of Things (IoT) Technology to infer transit ridership and waiting time at bus stops. Specifically, this study explored the use of Raspberry Pi computers, which are small and inexpensive sets of hardware, to scan the Wi-Fi networks of passengers’ smartphones. The process was used to infer passenger counts and obtain information on passenger trajectories based on Global Positioning System (GPS) data. The research was conducted as a case study of the Streamline Bus System in Bozeman, Montana. To evaluate the reliability of the data collected with the Raspberry Pi computers, the study conducted technology-based estimation of ridership, OD flows, wait time, and travel time for a comparison with ground truth data (passenger surveys, manual data counts, and bus travel times). This study introduced the use of a wireless Wi-Fi scanning device for transit data collection, called a Smart Station. It combines an innovative set of hardware and software to create a non-intrusive and passive data collection mechanism. Through the field testing and comparison evaluation with ground truth data, the Smart Station produced accurate estimates of ridership, origin-destination characteristics, wait times, and travel times. Ridership data has traditionally been collected through a combination of manual surveys and Automatic Passenger Counter (APC) systems, which can be time-consuming and expensive, with limited capabilities to produce real-time data. The Smart Station shows promise as an accurate and cost-effective alternative. The advantages of using Smart Station over traditional data collection methods include the following: (1) Wireless, automated data collection and retrieval, (2) Real-time observation of passenger behavior, (3) Negligible maintenance after programming and installing the hardware, (4) Low costs of hardware, software, and installation, and (5) Simple and short programming and installation time. If further validated through additional research and development, the device could help transit systems facilitate data collection for route optimization, trip planning tools, and traveler information systems.