Journal articles: 'Chemical autoignition delay'

1

Bradley, Derek, and R. A. Head. "Engine autoignition: The relationship between octane numbers and autoignition delay times." Combustion and Flame 147, no. 3 (November 2006): 171–84. http://dx.doi.org/10.1016/j.combustflame.2006.09.001.

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Krisman, Alex, Evatt R. Hawkes, and Jacqueline H. Chen. "Two-stage autoignition and edge flames in a high pressure turbulent jet." Journal of Fluid Mechanics 824 (July 4, 2017): 5–41. http://dx.doi.org/10.1017/jfm.2017.282.

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A three-dimensional direct numerical simulation is conducted for a temporally evolving planar jet of n-heptane at a pressure of 40 atmospheres and in a coflow of air at 1100 K. At these conditions, n-heptane exhibits a two-stage ignition due to low- and high-temperature chemistry, which is reproduced by the global chemical model used in this study. The results show that ignition occurs in several overlapping stages and multiple modes of combustion are present. Low-temperature chemistry precedes the formation of multiple spatially localised high-temperature chemistry autoignition events, referred to as ‘kernels’. These kernels form within the shear layer and core of the jet at compositions with short homogeneous ignition delay times and in locations experiencing low scalar dissipation rates. An analysis of the kernel histories shows that the ignition delay time is correlated with the mixing rate history and that the ignition kernels tend to form in vortically dominated regions of the domain, as corroborated by an analysis of the topology of the velocity gradient tensor. Once ignited, the kernels grow rapidly and establish edge flames where they envelop the stoichiometric isosurface. A combination of kernel formation (autoignition) and the growth of existing burning surface (via edge-flame propagation) contributes to the overall ignition process. An analysis of propagation speeds evaluated on the burning surface suggests that although the edge-flame speed is promoted by the autoignitive conditions due to an increase in the local laminar flame speed, edge-flame propagation of existing burning surfaces (triggered initially by isolated autoignition kernels) is the dominant ignition mode in the present configuration.

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Yepes-Tumay, Hernando Alexander, and Arley Cardona-Vargas. "Influence of high ethane content on natural gas ignition." Revista Ingenio 16, no. 1 (January 1, 2019): 36–42. http://dx.doi.org/10.22463/2011642x.2384.

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The effect of ethane on combustion and natural gas autoignition was studied in the present paper. Two fuel mixture of natural gas with high ethane content were considered, 75% CH4 – 25% C2H6 (mixture 1), and 50% CH4 – 50% C2H6 (mixture 2). Natural gas combustion incidence was analyzed through the calculation of energy properties and the ignition delay time numerical calculations along with an ignition mode analysis. Specifically, the strong ignition limit was calculated to determine the effect of ethane on natural gas autoignition. According to the results, ignition delay time decreases for both mixtures in comparison with pure methane. The strong ignition limit shifts to lower temperatures when ethane is present in natural gas chemical composition.

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Saitoh, Hironori, Koji Uchida, and Norihiko Watanabe. "Numerical Study on the Required Surrounding Gas Conditions for Stable Autoignition of an Ethanol Spray." Journal of Combustion 2019 (October 17, 2019): 1–12. http://dx.doi.org/10.1155/2019/1329389.

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This study deals with the development of controlled-ignition technology for high-performance compression ignition alcohol engines. Among the alcohol fuels, we focus on ethanol as it is a promising candidate of alternative fuels replacing petroleum. The objective of this study is to reveal the physical and chemical phenomena in the mixture formation process up to autoignition of an ethanol spray. In our previous numerical study, we showed the mixture formation process for gas oil and ethanol sprays in the form of spatial excess air ratio and temperature distributions inside a spray and their temporal histories from fuel injection. The results showed a good agreement with those of theoretical analysis based on the momentum theory of spray penetration. Calculation was also confirmed as reasonable by comparing to the experimental results. Through the series of our experimental and numerical studies, the reason for poor autoignition quality of an ethanol spray was revealed, that is, difficulty in simultaneous attainments of autoignition-suitable concentration and temperature in the spray mixture formation due to its fuel and thermal properties of smaller stoichiometric air-fuel ratio and much greater heat of evaporation compared to conventional diesel fuels. However, autoignition of an ethanol spray has not been obtained yet in either experiments or numerical analysis. As the next step, we numerically examined several surrounding gas pressure and temperature conditions to make clear the surrounding gas conditions enough to obtain stable autoignition. One of the commercial CFD codes CONVERGE was used in the computational calculation with the considerations of turbulence, atomization, evaporation, and detailed chemical reaction. Required surrounding gas pressure and temperature for stable autoignition with acceptable ignition delay of an ethanol spray and feasibility of the development of high-performance compression ignition alcohol engines are discussed in this paper.

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Arutyunov, Vladimir, Andrey Belyaev, Artem Arutyunov, Kirill Troshin, and Aleksey Nikitin. "Autoignition of Methane–Hydrogen Mixtures below 1000 K." Processes 10, no. 11 (October 24, 2022): 2177. http://dx.doi.org/10.3390/pr10112177.

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In the range of 800–1200 K, both experiments and kinetic modeling demonstrate a significant difference in the dependence of the ignition delay time of methane and hydrogen on pressure and temperature, with the complex influence of these parameters on the autoignition delay time of methane–hydrogen–air mixtures. In connection with the prospects for the widespread use of methane–hydrogen mixtures in energy production and transport, a detailed analysis of their ignition at temperatures below 1000 K, the most important region from the point of view of their practical application, is carried out. It is shown that such a complex behavior is associated with the transition in this temperature range from low-temperature mechanisms of oxidation of both methane and hydrogen, in which peroxide radicals and molecules play a decisive role, to high-temperature mechanisms of their oxidation, in which simpler radicals dominate. A kinetic interpretation of the processes occurring in this case is proposed.

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Yao, Shengzhuo, Yuewei Zhang, Yongfeng Liu, Guijun Bi, Lu Zhang, Ping Wei, Jinou Song, and Hua Sun. "Effects of High-Concentration CO2 on Ignition Delay Time of 70% n-Heptane/30% Toluene Mixtures." Journal of Sensors 2022 (April 29, 2022): 1–17. http://dx.doi.org/10.1155/2022/4334317.

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In order to research the high-concentration CO2 effects on ignition delay time (IDT) of diesel surrogate fuel (70% n-heptane/30% toluene), a carbon dioxide effect (CDE) model is established, which considers fuel and ambient gas concentration, density, and temperature influence on autoignition under CO2/O2 atmosphere. Firstly, a chemical model of n-heptane/toluene is established, and the coupling, reduction, and simulation processes are carried out in chemical kinetic software with the IDT as the target parameter. Secondly, a constant volume combustion chamber (CVCC) visualization platform is built by incorporating a high-speed camera system and different working conditions are set in the CO2 volume fraction range (40%-70%) at 3.0 MPa and 850 K for an autoignition experiment. Thirdly, experiment and simulation results are discussed in air, 60% CO2/40% O2, 50% CO2/50% O2, and 40% CO2/60% O2 atmospheres, including the IDT, CO2 effects, temperature sensitivity, and OH radical rate of production (ROP). The results show that the CDE model well predicts the 70% n-heptane/30% toluene IDT under the CO2/O2 atmosphere and the average error in 60% CO2/40% O2 atmosphere is 5.29%. Besides, when the CO2 volume fraction increases from 40% to 60%, the CO2 thermal effect plays a leading role in the IDT prolongation and the OH radical ROP peak of R4 (O+H2O⟶2OH) decreases by 180%.

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Ban, Marko, and Neven Duic. "Adaptation of n-heptane autoignition tabulation for complex chemistry mechanisms." Thermal Science 15, no. 1 (2011): 135–44. http://dx.doi.org/10.2298/tsci100514077b.

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The adaptation of auto-ignition tabulation for effective use of complex chemical mechanisms will be presented in this paper. Taking cool flame ignition phenomenon into account could improve numerical simulations of combustion in compression ignition engines. Current approaches of successful simulation of this phenomenon are based on the extraction of ignition delay times, heat releases and also reaction rates from tabulated data dependant on four parameters: temperature, pressure, equivalence ratio and exhaust gasses mass fraction. The methods described here were used to create lookup tables including cool flame using a comprehensive chemical mechanism without including reaction rates data (as used by other authors). The method proved to be stable for creating tables and these results will be shown, as well as initial implementation results using the tables in computational fluid dynamics software.

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Khalil, Ahmed T., Dimitris M. Manias, Efstathios-Al Tingas, Dimitrios C. Kyritsis, and Dimitris A. Goussis. "Algorithmic Analysis of Chemical Dynamics of the Autoignition of NH3–H2O2/Air Mixtures." Energies 12, no. 23 (November 21, 2019): 4422. http://dx.doi.org/10.3390/en12234422.

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The dynamics of a homogeneous adiabatic autoignition of an ammonia/air mixture at constant volume was studied, using the algorithmic tools of Computational Singular Perturbation. Since ammonia combustion is characterized by both unrealistically long ignition delays and elevated NO x emissions, the time frame of action of the modes that are responsible for ignition was analyzed by calculating the developing time scales throughout the process and by studying their possible relation to NO x emissions. The reactions that support or oppose the explosive time scale were identified, along with the variables that are related the most to the dynamics that drive the system to an explosion. It is shown that reaction H 2 O 2 (+M) → OH + OH (+M) is the one contributing the most to the time scale that characterizes ignition and that its reactant H 2 O 2 is the species related the most to this time scale. These findings suggested that addition of H 2 O 2 in the initial mixture will influence strongly the evolution of the process. It was shown that ignition of pure ammonia advanced as a slow thermal explosion with very limited chemical runaway. The ignition delay could be reduced by more than two orders of magnitude through H 2 O 2 addition, which causes only a minor increase in NO x emissions.

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Khalil, Ahmed T., Dimitris M. Manias, Dimitrios C. Kyritsis, and Dimitris A. Goussis. "NO Formation and Autoignition Dynamics during Combustion of H2O-Diluted NH3/H2O2 Mixtures with Air." Energies 14, no. 1 (December 25, 2020): 84. http://dx.doi.org/10.3390/en14010084.

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NO formation, which is one of the main disadvantages of ammonia combustion, was studied during the isochoric, adiabatic autoignition of ammonia/air mixtures using the algorithm of Computational Singular Perturbation (CSP). The chemical reactions supporting the action of the mode relating the most to NO were shown to be essentially the ones of the extended Zeldovich mechanism, thus indicating that NO formation is mainly thermal and not due to fuel-bound nitrogen. Because of this, addition of water vapor reduced NO formation, because of its action as a thermal buffer, but increased ignition delay, thus exacerbating the second important caveat of ammonia combustion, which is unrealistically long ignition delay. However, it was also shown that further addition of just 2% molar of H2O2 does not only reduce the ignition delay by a factor of 30, but also reverses the way water vapor affects ignition delay. Specifically, in the ternary mixture NH3/H2O/H2O2, addition of water vapor does not prolong but rather shortens ignition delay because it increases OH radicals. At the same time, the presence of H2O2 does not affect the influence of H2O in suppressing NO generation. In this manner, we were able to show that NH3/H2O/H2O2 mixtures offer a way to use ammonia as carbon-less fuel with acceptable NOx emissions and realistic ignition delay.

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Mažeika, Marius, Gvidonas Labeckas, Oleg Klyus, and Irena Kanapkienė. "THE EFFECT OF THE BIOFUEL PROPERTIES ON THE AUTOIGNITION DELAY IN A DIESE ENGINE." Agricultural Engineering 46, no. 1 (September 10, 2014): 51–65. http://dx.doi.org/10.15544/ageng.2014.005.

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The article presents the test results of a four-stroke, four-cylinder, naturally aspirated, DI 60 kW diesel engine operating on diesel fuel (DF) and its 5 vol% (E5), 10 vol% (E10), and 15 vol% (E15) blends with anhydrous (99.8%) ethanol (E). An additional ethanol–diesel–biodiesel blend E15B was prepared by adding the 15 vol% of ethanol and 5 vol% of biodiesel (B) to diesel fuel (80 vol%). The purpose of the research was to examine the influence of the ethanol and RME addition to diesel fuel on the start of injection and autoignition delay. The widely differing physical and chemical properties of the biofuel blends along with engine load and speed modes were taken into account to provide sound analysis of the experimental test results. Studies showed that the density of biofuel blends E5, E10, E15 and E15B was 0.33%, 0.65%, 0.95% and 0.56% lower at the temperature of 40 °C than the corresponding value (0.828 kg/m3) of diesel fuel. Kinematic viscosity of biofuel blends E5, E10, E15 and E15B also decreased by 7.8%, 11.0%, 13.0% and 10.8% at the temperature of 40 °C and the cetane number was 3%, 9%, 14% and 12% lower, respectively, compared to commercial diesel fuel. The use of biofuel blends E15 and E15B the autoignition delay increased by 4.4% and 9.5% compared to normal diesel operation at full pe = 0.67 MPa (100%) load and 1400 rpm speed at which maximum torque occurs.

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11

Bradley, D. "Combustion and the design of future engine fuels." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, no. 12 (June 25, 2009): 2751–65. http://dx.doi.org/10.1243/09544062jmes1519.

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The fast diminution of readily extractable sources of fossil fuels, particularly oil, and concerns about global warming are leading to the creation of many new potential fuels. Their practicability must be assessed in terms of a wide range of physico-chemical properties, in relation to the operational aerodynamics in different engines. This article concentrates on those properties related to combustion and these are discussed in detail for some fuels with contrasting properties. Intrinsic fuel properties include volumetric energy, vapour pressure, heat of reaction, latent enthalpy of vaporization, and the relative volumes of energy that engines can breathe. Important combustion properties include the minimum ignition energy, laminar burning velocity, Markstein numbers for strain and curvature, flame extinction stretch rates for positive and negative stretch, stretch factor for flame instability, turbulent flame burning and quenching, autoignition delay time, excitation time for autoignition heat release, research and motor octane numbers and cetane number (CN). Such properties are manifest in a variety of aerodynamic contexts: for example, the nature of autoignition depends on spatial reactivity gradients and the acoustic speed. Particular problems can arise in characterizing engine knock when operational regimes are outside those in which the octane and CNs are determined. The approach adopted in this article does not assume any unique alignment between fuels, mode of combustion, and power unit, and different possibilities are discussed.

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Chen, K., G. A. Karim, and H. C. Watson. "Experimental and Analytical Examination of the Development of Inhomogeneities and Autoignition During Rapid Compression of Hydrogen-Oxygen-Argon Mixtures." Journal of Engineering for Gas Turbines and Power 125, no. 2 (April 1, 2003): 458–65. http://dx.doi.org/10.1115/1.1560710.

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The reliable prediction of the processes leading to autoignition during the rapid compression of an initially homogeneous mixture of fuel and air requires the coupled modeling of multidimensional fluid dynamics and heat transfer together with a sufficiently detailed description of the chemical kinetics of the oxidation reactions. To satisfy fully such requirements tends at present to be unmanageable. The paper describes an improvised approach that combines multidimensional fluid dynamics modeling (CFD KIVA-3) with derived variable effective global chemical kinetic data. These were generated through a fitting procedure of the corresponding results obtained while using a detailed chemical kinetic scheme; albeit with uniform properties, at constant volume and an initial state similar to that existing during the ignition delay. It is shown while using such an approach that spatially nonuniform properties develop rapidly within the initially homogeneous charge due to piston motion, heat transfer and any preignition energy release activity. This leads autoignition to take place first within the hottest region and a reaction front progresses at a finite rate to consume the rest of the mixture. The present contribution examines the compression ignition of hydrogen-oxygen mixtures in the presence of argon as a diluent. Validation of the predicted results is made using a range of corresponding experimental values obtained in a single-shot pneumatically driven rapid compression apparatus. It is to be shown that the simulation which indicates the build up of temperature gradients during the compression stroke, predicts earlier autoignition than that obtained with a single-zone simulation. Good agreement between predicted and experimental results is achieved, especially for lean and stoichiometric mixtures under high compression ratio conditions. The CFD-based simulation results are found to be closer to the corresponding experimental results than those obtained with an assumed reactive system of uniform properties and using detailed reaction kinetics.

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Hernandez, Juan J., Clara Serrano, and Javier Perez. "Prediction of the Autoignition Delay Time of Producer Gas from Biomass Gasification." Energy & Fuels 20, no. 2 (March 2006): 532–39. http://dx.doi.org/10.1021/ef058025c.

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Sabia, Pino, Mariarosaria de Joannon, Marco Lubrano Lavadera, Paola Giudicianni, and Raffaele Ragucci. "Autoignition delay times of propane mixtures under MILD conditions at atmospheric pressure." Combustion and Flame 161, no. 12 (December 2014): 3022–30. http://dx.doi.org/10.1016/j.combustflame.2014.06.006.

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Gokulakrishnan, P., G. Gaines, J. Currano, M. S. Klassen, and R. J. Roby. "Experimental and Kinetic Modeling of Kerosene-Type Fuels at Gas Turbine Operating Conditions." Journal of Engineering for Gas Turbines and Power 129, no. 3 (May 31, 2006): 655–63. http://dx.doi.org/10.1115/1.2436575.

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Experimental and kinetic modeling of kerosene-type fuels is reported in the present work with special emphasis on the low-temperature oxidation phenomenon relevant to gas turbine premixing conditions. Experiments were performed in an atmospheric pressure, tubular flow reactor to measure ignition delay time of kerosene (fuel–oil No. 1) in order to study the premature autoignition of liquid fuels at gas turbine premixing conditions. The experimental results indicate that the ignition delay time decreases exponentially with the equivalence ratio at fuel-lean conditions. However, for very high equivalence ratios (>2), the ignition delay time approaches an asymptotic value. Equivalence ratio fluctuations in the premixer can create conditions conducive for autoignition of fuel in the premixer, as the gas turbines generally operate under lean conditions during premixed prevaporized combustion. Ignition delay time measurements of stoichiometric fuel–oil No. 1∕air mixture at 1 atm were comparable with that of kerosene type Jet-A fuel available in the literature. A detailed kerosene mechanism with approximately 1400 reactions of 550 species is developed using a surrogate mixture of n-decane, n-propylcyclohexane, n-propylbenzene, and decene to represent the major chemical constituents of kerosene, namely n-alkanes, cyclo-alkanes, aromatics, and olefins, respectively. As the major portion of kerosene-type fuels consists of alkanes, which are relatively more reactive at low temperatures, a detailed kinetic mechanism is developed for n-decane oxidation including low temperature reaction kinetics. With the objective of achieving a more comprehensive kinetic model for n-decane, the mechanism is validated against target data for a wide range of experimental conditions available in the literature. The data include shock tube ignition delay time measurements, jet-stirred reactor reactivity profiles, and plug-flow reactor species time–history profiles. The kerosene model predictions agree fairly well with the ignition delay time measurements obtained in the present work as well as the data available in the literature for Jet A. The kerosene model was able to reproduce the low-temperature preignition reactivity profile of JP-8 obtained in a flow reactor at 12 atm. Also, the kerosene mechanism predicts the species reactivity profiles of Jet A-1 obtained in a jet-stirred reactor fairly well.

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Taşkiran, Özgür Oğuz, and Metin Ergeneman. "Experimental Study on Diesel Spray Characteristics and Autoignition Process." Journal of Combustion 2011 (2011): 1–20. http://dx.doi.org/10.1155/2011/528126.

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The main goal of this study is to get the temporal and spatial spray evolution under diesel-like conditions and to investigate autoignition process of sprays which are injected from different nozzle geometries. A constant volume combustion chamber was manufactured and heated internally up to 825 K at 3.5 MPa for experiments. Macroscopic properties of diesel spray were recorded via a high-speed CCD camera by using shadowgraphy technique, and the images were analyzed by using a digital image processing program. To investigate the influence of nozzle geometry, 4 different types of divergent, straight, straight-rounded, convergent-rounded nozzles, were manufactured and used in both spray evolution and autoignition experiments. The internal geometry of the injector nozzles were obtained by using silicone mold method. The macroscopic properties of the nozzles are presented in the study. Ignition behaviour of different nozzle types was observed in terms of ignition delay time and ignition location. A commercial Diesel fuel,n-heptane, and a mixture of hexadecane-heptamethylnonane (CN65—cetane number 65) were used as fuels at ignition experiments. The similar macroscopic properties of different nozzles were searched for observing ignition time and ignition location differences. Though spray and ignition characteristics revealed very similar results, the dissimilarities are presented in the study.

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Jurić, Filip, Marko Ban, Peter Priesching, Carsten Schmalhorst, Neven Duić, and Milan Vujanović. "Numerical modeling of laminar flame speed and autoignition delay using general fuel-independent function." Fuel 323 (September 2022): 124432. http://dx.doi.org/10.1016/j.fuel.2022.124432.

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Xiao, Hua, Aiguo Chen, Yanze Guo, Lifu Zhang, Minghui Zhang, Xi Deng, Jun Li, and Wenxuan Ying. "Auto-Ignition Delay Characteristics of Ammonia Substitution on Methane." Processes 10, no. 11 (October 27, 2022): 2214. http://dx.doi.org/10.3390/pr10112214.

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Ammonia is a promising alternative fuel, which is considered to have the potential to substitute conventional fossil fuels. In the present work, auto-ignition characteristics of ammonia substitution on methane are investigated both experimentally and numerically. The auto-ignition procedure of ammonia-substituted methane/air mixtures are measured behind the reflected shock wave in a shock tube experiment system over temperatures from 1355 to 1877 K, pressure up to 5 atm and an equivalence ratio from 0.5 to 2. Numerical simulation studies using a detailed kinetics mechanism are also performed to gain a deep insight into the auto-ignition procedure of ammonia-substituted methane fuel mixtures. The established numerical model is verified with the measured auto-ignition delay time data by experiments. Then, the auto-ignition delay times are predicted under a wider range of conditions such as equivalence ratio, pressure, temperature, etc. In this way, combustion characteristics of such mixtures are investigated. It is found that adding ammonia fuel to methane will not change the autoignition delay time of methane a lot, while it can effectively benefit the reduction of carbon emissions. Finally, sensitivity analyses are performed to provide essential information for the elementary reaction sensitive to the ignition characteristics. The results present in this work can provide fundamental information for combustion application of ammonia-based fuels.

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Tao, Mingyuan, Peng Zhao, James P. Szybist, Patrick Lynch, and Haiwen Ge. "Insights into engine autoignition: Combining engine thermodynamic trajectory and fuel ignition delay iso-contour." Combustion and Flame 200 (February 2019): 207–18. http://dx.doi.org/10.1016/j.combustflame.2018.11.025.

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Frisque, A., J. Schnakenberg, J. Huang, and W. K. Bushe. "Stochastic simulation of variations in the autoignition delay time of premixed methane and air." Combustion Theory and Modelling 10, no. 2 (April 2006): 241–56. http://dx.doi.org/10.1080/13647830500399995.

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Fang, Ruozhou, and Chih-Jen Sung. "A Rapid Compression Machine Study of 2-Phenylethanol Autoignition at Low-To-Intermediate Temperatures." Energies 14, no. 22 (November 17, 2021): 7708. http://dx.doi.org/10.3390/en14227708.

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To meet the increasing anti-knocking quality demand of boosted spark-ignition engines, fuel additives are considered an effective approach to tailor fuel properties for satisfying the performance requirements. Thus, screening/developing bio-derived fuel additives that are best-suited for advanced spark-ignition engines has become a significant task. 2-Phenylethanol (2-PE) is an attractive candidate that features high research octane number, high octane sensitivity, low vapor pressure, and high energy density. Recognizing that the low temperature autoignition chemistry of 2-PE is not well understood and the need for fundamental experimental data at engine-relevant conditions, rapid compression machine (RCM) experiments are therefore conducted herein to measure ignition delay times (IDTs) of 2-PE in air over a wide range of conditions to fill this fundamental void. These newly acquired IDT data at low-to-intermediated temperatures, equivalence ratios of 0.35–1.5, and compressed pressures of 10–40 bar are then used to validate the 2-PE model developed by Shankar et al. (2017). It is found that this literature model greatly overpredicts the current RCM data. The comparison of experimental and simulated results also provides insights into 2-PE autoignition behaviors at varying conditions. Further chemical kinetic analyses demonstrate that the absence of the O2-addition pathway of β-R. radical in the 2-PE model of Shankar et al. (2017) could account for the model discrepancies observed at low-to-intermediated temperatures.

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Distaso, E., G. Calò, R. Amirante, P. De Palma, M. Mehl, M. Pelucchi, A. Stagni, and P. Tamburrano. "Highlighting the Role of Lubricant Oil in the Development of Hydrogen Internal Combustion Engines by means of a Kinetic Reaction Model." Journal of Physics: Conference Series 2385, no. 1 (December 1, 2022): 012078. http://dx.doi.org/10.1088/1742-6596/2385/1/012078.

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Abstract The urgent need to reduce the dependence on fossil fuels has re-ignited the interest toward Hydrogen Internal Combustion Engines (HICEs). Nevertheless, there are still criticalities that need to be assessed for accelerating the development of this technology. The undesired but unavoidable participation of lubricant oil to the combustion process can be the cause of many of these. Due to an extremely low autoignition resistance at low temperatures, lubricant oil is considered the main responsible for the onset of abnormal combustion modes, which need to be understood for delivering reliable and ready to market HICEs. By employing a kinetic reaction mode, this work analyses the autoignition tendency of hydrogen contaminated with n-C16H34 (n-hexadecane), the latter being selected as a surrogate species representative of lubricant oil chemical characteristics. Starting from the detailed CRECK model (Version 2003), a reduced mechanism with very small size (169 species and 2796 reactions) was developed, which makes it suitable for the use in practical CFD engine simulations. Zero-dimensional numerical simulations were performed employing the reduced mechanism to quantify the variation of hydrogen ignition delay time due to the presence of different amounts of lubricant oil. Operating conditions typical of engine chambers were considered in the analysis. The results show that lubricant oil can have a significant impact on the charge reactivity, especially in the low-temperature range, with consequences that can potentially hamper the development of HICEs.

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Kojima, Shinji, and Tetsunori Suzuoki. "Autoignition-delay measurement over lean to rich mixtures of n-butane/air under swirl conditions." Combustion and Flame 92, no. 3 (February 1993): 254–65. http://dx.doi.org/10.1016/0010-2180(93)90037-4.

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Chin, Gregory T., J. Y. Chen, Vi H. Rapp, and R. W. Dibble. "Development and Validation of a Reduced DME Mechanism Applicable to Various Combustion Modes in Internal Combustion Engines." Journal of Combustion 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/630580.

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A 28-species reduced chemistry mechanism for Dimethyl Ether (DME) combustion is developed on the basis of a recent detailed mechanism by Zhao et al. (2008). The construction of reduced chemistry was carried out with automatic algorithms incorporating newly developed strategies. The performance of the reduced mechanism is assessed over a wide range of combustion conditions anticipated to occur in future advanced piston internal combustion engines, such as HCCI, SAHCCI, and PCCI. Overall, the reduced chemistry gives results in good agreement with those from the detailed mechanism for all the combustion modes tested. While the detailed mechanism by Zhao et al. (2008) shows reasonable agreement with the shock tube autoignition delay data, the detailed mechanism requires further improvement in order to better predict HCCI combustion under engine conditions.

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Bates, Luke, Derek Bradley, Inna Gorbatenko, and Alison S. Tomlin. "Computation of methane/air ignition delay and excitation times, using comprehensive and reduced chemical mechanisms and their relevance in engine autoignition." Combustion and Flame 185 (November 2017): 105–16. http://dx.doi.org/10.1016/j.combustflame.2017.07.002.

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Liang, Wenkai, and Chung K. Law. "On Radical-Induced Ignition in Combustion Systems." Annual Review of Chemical and Biomolecular Engineering 10, no. 1 (June 7, 2019): 199–217. http://dx.doi.org/10.1146/annurev-chembioeng-060718-030141.

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This article reviews recent theoretical developments on incipient ignition induced by radical runaway in systems described by detailed chemistry. Employing eigenvalue analysis, we first analyze the canonical explosion limits of mixtures of hydrogen and oxygen, yielding explicit criteria that well reproduce their characteristic Z-shaped response in the pressure–temperature plot. Subsequently, we evaluate the role of hydrogen addition to the explosion limits of mixtures of oxygen with either carbon monoxide or methane, demonstrating and quantifying its strong catalytic effect, especially for the carbon monoxide cases. We then discuss the role of low-temperature chemistry in the autoignition of large hydrocarbon fuels, with emphasis on the first-stage ignition delay and the associated negative-temperature coefficient phenomena. Finally, we extend the analysis to problems of nonhomogeneous ignition in the presence of convective–diffusive transport, using counterflow as an example, demonstrating the canonical similarity between homogeneous and nonhomogeneous systems. We conclude with suggestions for potential directions for future research.

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Wolff, M. Cano, J. Meisl, R. Koch, and S. Wittig. "The influence of evaporation on the autoignition-delay of n-heptane air mixtures under gas turbine conditions." Symposium (International) on Combustion 27, no. 2 (January 1998): 2025–31. http://dx.doi.org/10.1016/s0082-0784(98)80048-9.

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Sahetchian, K. A., N. Blin, R. Rigny, A. Seydi, and M. Murat. "The oxidation of n-butane and n-heptane in a CFR engine. Isomerization reactions and delay of autoignition." Combustion and Flame 79, no. 3-4 (March 1990): 242–49. http://dx.doi.org/10.1016/0010-2180(90)90136-f.

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Starikovskii, A. Yu, N. B. Anikin, I. N. Kosarev, E. I. Mintoussov, S. M. Starikovskaia, and V. P. Zhukov. "Plasma-assisted combustion." Pure and Applied Chemistry 78, no. 6 (January 1, 2006): 1265–98. http://dx.doi.org/10.1351/pac200678061265.

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This paper presents an overview of experimental and numerical investigations of the nonequilibrium cold plasma generated under high overvoltage and further usage of this plasma for plasma-assisted combustion.Here, two different types of the discharge are considered: a streamer under high pressure and the so-called fast ionization wave (FIW) at low pressure.The comprehensive experimental investigation of the processes of alkane slow oxidation in mixtures with oxygen and air under nanosecond uniform discharge has been performed. The kinetics of alkane oxidation has been measured from methane to decane in stoichiometric and lean mixtures with oxygen and air at room temperature under the action of high-voltage nanosecond uniform discharge.The efficiency of nanosecond discharges as active particles generator for plasma-assisted combustion and ignition has been investigated. The study of nanosecond barrier discharge influence on a flame propagation and flame blow-off velocity has been carried out. With energy input negligible in comparison with the burner's chemical power, a double flame blow-off velocity increase has been obtained. A signicant shift of the ignition delay time in comparison with the autoignition has been registered for all mixtures.Detonation initiating by high-voltage gas discharge has been demonstrated. The energy deposition in the discharge ranged from 70 mJ to 12 J. The ignition delay time, the velocity of the flame front propagation, and the electrical characteristics of the discharge have been measured during the experiments. Under the conditions of the experiment, three modes of the flame front propagation have been observed, i.e., deflagration, transient detonation, and Chapman-Jouguet detonation. The efficiency of the pulsed nanosecond discharge to deflagration-to-detonation transition (DDT) control has been shown to be very high.

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30

Tennison, P. J., and R. Reitz. "An Experimental Investigation of the Effects of Common-Rail Injection System Parameters on Emissions and Performance in a High-Speed Direct-Injection Diesel Engine." Journal of Engineering for Gas Turbines and Power 123, no. 1 (June 6, 1999): 167–74. http://dx.doi.org/10.1115/1.1340638.

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An investigation of the effect of injection parameters on emissions and performance in an automotive diesel engine was conducted. A high-pressure common-rail injection system was used with a dual-guided valve covered orifice nozzle tip. The engine was a four-valve single cylinder high-speed direct-injection diesel engine with a displacement of approximately 12 liter and simulated turbocharging. The engine experiments were conducted at full load and 1004 and 1757 rev/min, and the effects of injection pressure, multiple injections (single vs pilot with main), and pilot injection timing on emissions and performance were studied. Increasing the injection pressure from 600 to 800 bar reduced the smoke emissions by over 50 percent at retarded injection timings with no penalty in oxides of nitrogen NOx or brake specific fuel consumption (BSFC). Pilot injection cases exhibited slightly higher smoke levels than single injection cases but had similar NOx levels, while the single injection cases exhibited slightly better BSFC. The start-of-injection (SOI) of the pilot was varied while holding the main SOI constant and the effect on emissions was found to be small compared to changes resulting from varying the main injection timing. Interestingly, the point of autoignition of the pilot was found to occur at a nearly constant crank angle regardless of pilot injection timing (for early injection timings) indicating that the ignition delay of the pilot is a chemical delay and not a physical (mixing) one. As the pilot timing was advanced the mixture became overmixed, and an increase of over 50 percent in the unburned hydrocarbon emissions was observed at the most advanced pilot injection timing.

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31

Kong, S. C., and R. D. Reitz. "Multidimensional Modeling of Diesel Ignition and Combustion Using a Multistep Kinetics Model." Journal of Engineering for Gas Turbines and Power 115, no. 4 (October 1, 1993): 781–89. http://dx.doi.org/10.1115/1.2906775.

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Ignition and combustion mechanisms in diesel engines were studied using the KIVA code, with modifications to the combustion, heat transfer, crevice flow, and spray models. A laminar-and-turbulent characteristic-time combustion model that has been used successfully for spark-ignited engine studies was extended to allow predictions of ignition and combustion in diesel engines. A more accurate prediction of ignition delay was achieved by using a multistep chemical kinetics model. The Shell knock model was implemented for this purpose and was found to be capable of predicting successfully the autoignition of homogeneous mixtures in a rapid compression machine and diesel spray ignition under engine conditions. The physical significance of the model parameters is discussed and the sensitivity of results to the model constants is assessed. The ignition kinetics model was also applied to simulate the ignition process in a Cummins diesel engine. The post-ignition combustion was simulated using both a single-step Arrhenius kinetics model and also the characteristic-time model to account for the energy release during the mixing-controlled combustion phase. The present model differs from that used in earlier multidimensional computations of diesel ignition in that it also includes state-of-the-art turbulence and spray atomization models. In addition, in this study the model predictions are compared to engine data. It is found that good levels of agreement with the experimental data are obtained using the multistep chemical kinetics model for diesel ignition modeling. However, further study is needed of the effects of turbulent mixing on post-ignition combustion.

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Nadiri, Solmaz, Paul Zimmermann, Laxmi Sane, Ravi Fernandes, Friedrich Dinkelacker, and Bo Shu. "Kinetic Modeling Study on the Combustion Characterization of Synthetic C3 and C4 Alcohols for Lean Premixed Prevaporized Combustion." Energies 14, no. 17 (September 2, 2021): 5473. http://dx.doi.org/10.3390/en14175473.

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To reach sustainable aviation, one approach is to use electro-fuels (e-fuels) within the gas turbine engines. E-fuels are CO2-neutral synthetic fuels which are produced employing electrical energy generated from renewable resources, where the carbon is taken out of the atmosphere or from biomass. Our approach is, to find e-fuels, which can be utilized in the lean premixed prevaporized (LPP) combustion, where most of the non-CO2 emissions are prevented. One of the suitable e-fuel classes is alcohols with a low number of carbons. In this work, the autoignition properties of propanol isomers and butanol isomers as e-fuels were investigated in a high-pressure shock tube (HPST) at temperatures from 1200 to 1500 K, the pressure of 10 bar, and lean fuel-air conditions. Additional investigations on the low-temperature oxidation and flame speed of C3 and C4 alcohols from the literature were employed to develop a comprehensive mechanism for the prediction of ignition delay time (IDT) and laminar burning velocity (LBV) of the above-mentioned fuels. A numerical model based on newly developed chemical kinetics was applied to further study the IDT and LBV of fuels in comparison to the Jet-A surrogate at the engine-related conditions along with the emissions prediction of the model at lean fuel-air conditions.

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33

Frederick, D., and J. Y. Chen. "Effects of Differential Diffusion on Predicted Autoignition Delay Times Inspired by H2/N2 Jet Flames in a Vitiated Coflow Using the Linear Eddy Model." Flow, Turbulence and Combustion 93, no. 2 (June 13, 2014): 283–304. http://dx.doi.org/10.1007/s10494-014-9547-3.

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34

SAHETCHIAN, K., R. RIGNY, and N. BLIN. "Evaluation of Hydroperoxide Concentrations During the Delay of Autoignition in an Experimental Four Stroke Engine: Comparison with Cool Flame Studies in a Flow System." Combustion Science and Technology 60, no. 1-3 (July 1988): 117–24. http://dx.doi.org/10.1080/00102208808923979.

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35

Cicci, Francesco, and Giuseppe Cantore. "Preliminary study on the influence of Octane Sensitivity on knock statistics in a GDI engine." E3S Web of Conferences 312 (2021): 07020. http://dx.doi.org/10.1051/e3sconf/202131207020.

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In the 3D-CFD practice, actual gasoline fuels are usually replaced by surrogate blends composed of Iso-Octane, n-Heptane and Toluene (Toluene Reference Fuels, TRFs). In this work, the impact of surrogate formulation on the probability of end-gas auto-ignition is investigated in a single cylinder engine. CFD simulations are run on equal charge stratification to discern the effect of fuel reactivity from that of evaporation and mixing. Blends are formulated using an internal methodology, coupled with a proprietary method to predict knock statistical occurrence within a RANS framework. Chemical kinetics calculations of Ignition delay times are performed in a 0D constant pressure reactor using a mechanism for gasoline surrogates, proposed by the Clean Combustion Research Center of King Abdullah University of Science and Technology (KAUST), consisting of 2406 species and 9633 reactions. Surrogates mimic a commercial European gasoline (ULG95). Five different formulations are presented. Three are characterised by equal RON (95) with progressively decreasing Octane Sensitivity S. The fourth and the fifth have a sensitivity of 10 but with lower RON (92.5 and 90). The combinations allow the reader to separate the effects of octane sensitivity from those of RON quality of the tested fuels. Applying the different surrogates, changes in each of autoignition phasing, magnitude and statistical probability are investigated. Results confirm the dependency of knock occurrence on the Octane Sensitivity, as well as the need to include engine-specific and operation-specific characteristics in the analysis of knock. The Octane Index (OI) formulation developed by Kalghatgi is discussed.

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36

Sosse, A. Alaoui, J. P. Vantelon, C. Breillat, and F. Gaboriaud. "Some aspects of autoignition limits and delays of Timahdit oil shale." Energy & Fuels 3, no. 5 (September 1989): 616–20. http://dx.doi.org/10.1021/ef00017a015.

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37

Karimi, Miad, Bradley Ochs, Zefang Liu, Devesh Ranjan, and Wenting Sun. "Measurement of methane autoignition delays in carbon dioxide and argon diluents at high pressure conditions." Combustion and Flame 204 (June 2019): 304–19. http://dx.doi.org/10.1016/j.combustflame.2019.03.020.

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38

Valco, Daniel, Gerald Gentz, Casey Allen, Meredith Colket, Tim Edwards, Sandeep Gowdagiri, Matthew A. Oehlschlaeger, Elisa Toulson, and Tonghun Lee. "Autoignition behavior of synthetic alternative jet fuels: An examination of chemical composition effects on ignition delays at low to intermediate temperatures." Proceedings of the Combustion Institute 35, no. 3 (2015): 2983–91. http://dx.doi.org/10.1016/j.proci.2014.05.145.

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39

Jella, Sandeep, Gilles Bourque, Pierre Gauthier, Philippe Versailles, Jeffrey M. Bergthorson, Ji-Woong Park, Tianfeng Lu, Snehashish Panigrahy, and Henry Curran. "Analysis of Autoignition Chemistry in Aeroderivative Premixers At Engine Conditions." Journal of Engineering for Gas Turbines and Power, June 11, 2021. http://dx.doi.org/10.1115/1.4051460.

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Abstract The minimization of autoignition risk is critical to premixer design. Safety factors based on ignition delays of homogeneous mixtures, are generally used to guide the choice of a residence time for a given premixer. However, autoignition chemistry at aeroderivative conditions is fast (0.5-2 milliseconds) and can be initiated within typical premixer residence times. The analysis of what takes place in this short period involves the study of low-temperature precursor chemistry. By coupling the evolution of the Chemical Explosive Modes to turbulence, it is possible to obtain a measure of spatial autoignition risk where both chemical (e.g. ignition delay) and aerodynamic (e.g. local residence time) influences are unified. In this article, we describe a method that couples Large Eddy Simulation to newly developed, reduced autoignition chemical kinetics to study autoignition precursors in an example premixer representative of real life geometric complexity. A blend of pure methane and dimethyl ether (DME), a common fuel used for experimental autoignition studies, was transported using the reduced mechanism (38 species / 238 reactions) at engine conditions at increasing levels of DME concentration until exothermic autoignition kernels were formed. The Chemical Explosive Mode analysis closely follows the large thermochemical changes in the premixer as a function of DME concentration and identifies where the premixer is sensitive and flame anchoring is likely to occur.

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40

Zheng, Ziliang, Tamer Badawy, Naeim Henein, Eric Sattler, and Nicholas Johnson. "Effect of Cetane Improver on Autoignition Characteristics of Low Cetane Sasol IPK Using Ignition Quality Tester1." Journal of Engineering for Gas Turbines and Power 136, no. 8 (March 13, 2014). http://dx.doi.org/10.1115/1.4026812.

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This paper investigates the effect of a cetane improver on the autoignition characteristics of Sasol IPK in the combustion chamber of the ignition quality tester (IQT). The fuel tested was Sasol IPK with a derived cetane number (DCN) of 31, treated with different percentages of Lubrizol 8090 cetane improver ranging from 0.1 to 0.4%. Tests were conducted under steady state conditions at a constant charging pressure of 21 bar. The charge air temperature before fuel injection varied from 778 to 848 K. Accordingly, all the tests were conducted under a constant charge density. The rate of heat release was calculated and analyzed in detail, particularly during the autoignition period. In addition, the physical and chemical delay periods were determined by comparing the results of two tests. The first was conducted with fuel injection into air according to ASTM standards where combustion occurred. In the second test, the fuel was injected into the chamber charged with nitrogen. The physical delay is defined as the period of time from start of injection (SOI) to point of inflection (POI), and the chemical delay is defined as the period of time from POI to start of combustion (SOC). Both the physical and chemical delay periods were determined under different charge temperatures. The cetane improver was found to have an effect only on the chemical ID period. In addition, the effect of the cetane improver on the apparent activation energy of the global combustion reactions was determined. The results showed a linear drop in the apparent activation energy with the increase in the percentage of the cetane improver. Moreover, the low temperature (LT) regimes were investigated and found to be presented in base fuel, as well as cetane improver treated fuels.

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Zhong, Lijia, Lei Zhou, Peilin Liu, Xiaojun Zhang, Kuangdi Li, Rui Chen, and Haiqiao Wei. "Experimental observation on the end-gas autoignition and detonation affected by chemical reactivity in confined space." Physics of Fluids, July 24, 2022. http://dx.doi.org/10.1063/5.0097382.

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The deflagration to detonation transition (DDT) remains one of the most interesting and mysterious physical phenomena in the combustion of energetic materials, which contains substantial complicated and nonlinear characteristics. In the present work, the effect of the chemical reactivity of different fuels and diluent gases on the end-gas autoignition and detonation development in a confined space was investigated. Five fuels (hydrogen, methane, iso-octane, n-heptane, and PRF50) and three diluent gases (argon, nitrogen, and carbon dioxide) were used to change the chemical reactivity. The results showed that both the chemical reactivity and shock wave had a significant influence on the end-gas autoignition and detonation development. For mixtures with different diluent gases, it was observed that the transition thresholds (denoted by critical oxygen fraction) increased in the order of argon, nitrogen, and carbon dioxide. Different detonation modes with varying shock compressions were observed under different diluents for n-heptane. Although the flame propagation of different fuels differs at 21% oxygen fraction, end-gas autoignition and detonation development processes can still be observed in all kinds of fuels when the oxygen fraction was elevated to a certain value. The transition thresholds increased in the order of hydrogen, n-heptane, PRF50, iso-octane, and methane. Further analysis revealed that the fuel with a shorter ignition delay usually required a lower flame tip velocity, accomplished with a delayed occurrence of detonation. In addition, the transition threshold was determined by the chemical reactivity and flame speed.

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McClure, Jonathan, Mirko Bothien, and Thomas Sattelmayer. "Autoignition delay modulation by high-frequency thermoacoustic oscillations in reheat flames." Proceedings of the Combustion Institute, October 2022. http://dx.doi.org/10.1016/j.proci.2022.08.047.

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Allen, James C., William J. Pitz, and Brian T. Fisher. "Experimental and Computational Study of n-Heptane Autoignition in a Direct-Injection Constant-Volume Combustion Chamber." Journal of Engineering for Gas Turbines and Power 136, no. 9 (April 18, 2014). http://dx.doi.org/10.1115/1.4027194.

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The purpose of this study was to characterize experimental n-heptane combustion behavior in a direct-injection constant-volume combustion chamber (DI-CVCC), using chamber pressure to infer ignition delay and heat-release rate. Measurements generally displayed expected trends and indicated entirely premixed combustion with no mixing-controlled phase. A significant finding was the observation of negative temperature coefficient (NTC) behavior. Comparing results with CHEMKIN-PRO simulations, it was found that a homogeneous combustion model was reasonably accurate for ignition delays longer than 5 ms. The combination of NTC behavior and homogeneous fuel-air mixtures suggests that this DI-CVCC can be useful for validation of chemical-kinetic mechanisms.

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Yang, Junfeng, Valeri I. Golovithcev, Chitralkumar V. Naik, and Ellen Meeks. "Comparative Study of Diesel Oil and Biodiesel Spray Combustion Based on Detailed Chemical Mechanisms." Journal of Engineering for Gas Turbines and Power 136, no. 3 (November 21, 2013). http://dx.doi.org/10.1115/1.4025724.

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In the present work, a semidetailed combustion mechanism for biodiesel fuel was validated against the measured autoignition delay times and subsequently implemented in the fortÉ cfd engine simulation package (Reaction Design Inc., 2010, “fortÉ, FOR-UG-40102-1009-UG-1b,” Reaction Design Inc., San Diego, CA) to investigate the spray characteristics (e.g., the liquid penetration and flame lift-off distances of rapeseed oil methyl ester (RME) fuel in a constant-volume combustion chamber). The modeling results were compared with the experimental data. Engine simulations were performed for a Volvo D12C heavy-duty diesel engine fueled by RME on a 72 deg sector mesh. Predictions were validated against measured in-cylinder parameters and exhaust emission concentrations. The semidetailed mechanism was shown to be an efficient and accurate representation of actual biodiesel combustion phases. Meanwhile, as a comparative study, the simulations based on a detailed diesel oil surrogate mechanism were performed for diesel oil under the same conditions.

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Baker, Jessica, Ramees K. Rahman, Michael Pierro, Jacklyn Higgs, Justin Urso, Cory Kinney, and Subith Vasu. "Experimental Ignition Delay Time Measurements and Chemical Kinetics Modeling Of Hydrogen/Ammonia/Natural Gas Fuels." Journal of Engineering for Gas Turbines and Power, September 22, 2022. http://dx.doi.org/10.1115/1.4055721.

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Abstract Hydrogen-carrying compounds have accrued interest as an alternative to traditional fossil fuels due to their function as zero-emission fuels. As such, there is interest in investigating hydrogen-carrying compounds to improve understanding of the fuels' characteristics for use in high-pressure systems. In the current study, the oxidation of ammonia/natural gas/hydrogen mixtures was carried out to study CO formation as well as ignition delay times behind reflected shock waves in order to refine chemical kinetic models. Experiments were carried out in a shock tube facility by utilizing chemiluminescence to obtain OH* emission and laser absorption spectroscopy to obtain CO profiles over a temperature range between 1200 K to 1800 K with an average pressure of 2.2 atm. Experimental mixtures included neat and combination natural gas/hydrogen with ammonia addition, with all mixtures except one having an equivalence ratio of 1. Results were compared with the GRI 3.0 mechanism and the newly developed UCF 2022 mechanism utilizing CHEMKIN-Pro software. In general, models were able to capture the trend in autoignition delay times and CO time histories for natural gas and ammonia mixtures. For ammonia-hydrogen mixtures, GRI 3.0 failed to predict ignition delay times, whereas the UCF 2022 mechanism was able to capture the IDTs within uncertainty limits. A sensitivity analysis was conducted to understand the important reactions at the experimental conditions. Finally, a reaction pathway analysis was carried out to understand ammonia decomposition pathways in the presence of hydrogen and natural gas.

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Jayakumar, Chandrasekharan, Jagdish Nargunde, Anubhav Sinha, Walter Bryzik, Naeim A. Henein, and Eric Sattler. "Effect of Biodiesel, Jet Propellant (JP-8) and Ultra Low Sulfur Diesel Fuel on Auto-Ignition, Combustion, Performance and Emissions in a Single Cylinder Diesel Engine." Journal of Engineering for Gas Turbines and Power 134, no. 2 (December 8, 2011). http://dx.doi.org/10.1115/1.4003971.

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Concern about the depletion of petroleum reserves, rising prices of conventional fuels, security of supply and global warming have driven research toward the development of renewable fuels for use in diesel engines. These fuels have different physical and chemical properties that affect the diesel combustion process. This paper compares between the autoignition, combustion, performance and emissions of soy-bean derived biodiesel, Jet propellant (JP-8) and ultra low sulfur diesel (ULSD) in a high speed single-cylinder research diesel engine equipped with a common rail injection system. Tests were conducted at steady state conditions at different injection pressures ranging from 600 bar to 1200 bar. The ‘rate of heat release’ traces are analyzed to determine the effect of fuel properties on the ignition delay, premixed combustion fraction and mixing and diffusion controlled combustion fractions. Biodiesel produced the largest diffusion controlled combustion fraction at all injection pressures compared to ULSD and JP-8. At 600 bar injection pressure, the diffusion controlled combustion fraction for biodiesel was 53% whereas both JP-8 and ULSD produced 39%. In addition, the effect of fuel properties on engine performance, fuel economy, and engine-out emissions is determined. On an average JP-8 produced 3% higher thermal efficiency than ULSD. Special attention is given to the oxides of nitrogen (NOx) emissions and particulate matter characteristics. On an average biodiesel produced 37% less NOx emissions compared to ULSD and JP-8.

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47

Ge, Haiwen, and Peng Zhao. "Effects of stratification and charge cooling on combustion in a gasoline direct-injection compression ignition (GDCI) engine." International Journal of Engine Research, February 9, 2022, 146808742210773. http://dx.doi.org/10.1177/14680874221077333.

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With the development of low temperature engine combustion strategies, performance of gasoline-type fuels under compression ignition conditions has attracted extensive research interest. Meanwhile, for the sake of co-optimization of engines and fuels for future ground transportation, identification and evaluation of general fuel properties should be a core research priority instead of endless testing of specific fuels. In this study, the roles of fuel octane sensitivity in characterizing the ignition performance of gasoline surrogates have been systematically investigated under typical gasoline direct ignition compression ignition (GDCI) engine conditions using 3D combustion CFD simulation, especially considering the subsequent in-cylinder charge stratification and charge cooling. Two different operating conditions, high boost pressure low boost temperature (beyond-RON) case and low boost pressure high boost temperature (beyond-MON) case, were considered. By comparing with our previous zero-dimensional chemical kinetic study of gasoline surrogates in advanced compression ignition (ACI) engines, the effects of stratification and charge cooling on the combustion processes are investigated. It is found that different fuel octane sensitivities lead to slight difference in equivalence ratio stratification and charge cooling due to differences in volatility. However, fuel reactivity is still the more dominant factor than the stratification and charge cooling effects in determining combustion phasing. The present results help to justify the P-T domain framework for engine autoignition analysis of overlapping pressure-temperature trajectory with ignition delay iso-contour. The results also provide useful guidance to the understanding of GCI combustion process, and to the evaluation of controlling fuel properties and the selection of alternative fuels in GCI engines

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Naik, Chitralkumar V., Karthik V. Puduppakkam, and Ellen Meeks. "An Improved Core Reaction Mechanism for Saturated C0-C4 Fuels." Journal of Engineering for Gas Turbines and Power 134, no. 2 (December 20, 2011). http://dx.doi.org/10.1115/1.4004388.

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Accurate chemistry models are required to predict the combustion behavior of different fuels, such as synthetic gaseous fuels and liquid jet fuels. A detailed reaction mechanism contains chemistry for all the molecular components in the fuel or its surrogates. Validation studies that compare model predictions with the data from fundamental combustion experiments under well-defined conditions are least affected by the effect of transport on chemistry. Therefore they are the most reliable means for determining a reaction mechanism’s predictive capabilities. Following extensive validation studies and analysis of detailed reaction mechanisms for a wide range of hydrocarbon components reported in our previously published work (Puduppakkam et al., 2010, “Validation Studies of a Master Kinetic Mechanism for Diesel and Gasoline Surrogate Fuels,” SAE Technical Paper No. 2010-01-0545; Naik et al., 2010, “Validated F-T Fuel Surrogate Model for Simulation of Jet-Engine Combustion,” Proc. ASME Turbo Expo, Paper No. GT2010-23709; Naik et al., 2010, “Applying Detailed Kinetics to Realistic Engine Simulation: The Surrogate Blend Optimizer and Mechanism Reduction Strategies,” SAE J. Engines 3(1), pp. 241–259; Naik et al., 2010, “Modeling the Detailed Chemical Kinetics of Mutual Sensitization in the Oxidation of a Model Fuel for Gasoline and Nitric Oxide,” SAE J. Fuels Lubr. 3(1), pp. 556–566; and Puduppakkam et al., 2009, “Combustion and Emissions Modeling of an HCCI Engine Using Model Fuels,” SAE Technical Paper No. 2009-01-0669), we identified some common issues in the predictive nature of the mechanisms that are associated with inadequacies of the core (C0-C4) mechanism, such as inaccurate predictions of laminar flame speeds and autoignition delay times for several fuels. This core mechanism is shared by all of the mechanisms for the larger hydrocarbon components. Unlike the reaction paths for larger hydrocarbon fuels; however, reaction paths for the core chemistry do not follow prescribed reaction rate-rules. In this work, we revisit our core reaction mechanism for saturated fuels, with the goal of improving predictions for the widest range of fundamental experiments. To evaluate and validate the mechanism improvements, we performed a broad set of simulations of fundamental experiments. These experiments include measurements of ignition delay, flame speed and extinction strain rate, as well as species composition in stirred reactors, flames and flow reactors. The range of conditions covers low to high temperatures, very lean to very rich fuel-air ratios, and low to high pressures. Our core reaction mechanism contains thermochemical parameters derived from a wide variety of sources, including experimental measurements, ab initio calculations, estimation methods and systematic optimization studies. Each technique has its uncertainties and potential inaccuracies. Using a systematic approach that includes sensitivity analysis, reaction-path analysis, consideration of recent literature studies, and an attention to data consistency, we have identified key updates required for the core mechanism. These updates resulted in accurate predictions for various saturated fuels when compared to the data over a broad range of conditions. All reaction rate constants and species thermodynamics and transport parameters remain within known uncertainties and within physically reasonable bounds. Unlike most mechanisms in the literature, the mechanism developed in this work is self-consistent and contains chemistry of all saturated fuels.

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Qin, Qiushi, Zhijun Wu, and Alessandro Ferrari. "Study on Lifted Flame Stabilization Under Different Background Pressures." Journal of Thermal Science and Engineering Applications 14, no. 2 (June 18, 2021). http://dx.doi.org/10.1115/1.4051275.

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Abstract A numerical experimental investigation is presented for a steady methane lifted flame and a nonreaction jet flow in a co-flow of hot combustion products from lean premixed air-hydrogen combustion. The main objective has been to analyze the dependence of methane jet flame stability on the background pressure: a pressurized vitiated co-flow burner (PVCB) has been used to study the methane lifted flame and nonreaction jet flow under different background pressures (1–1.5 bars). The lifted flame is characterized by a liftoff height, which has been measured with a high-speed camera, and a central jet flow defined by the jet velocity, which has been measured by means of a high-sensitivity Schlieren imaging system. The experimental results show that the liftoff height decreases for an increment in the background pressure (from 1 to 1.5 bar at 1073 K) and in the co-flow temperature (from 1058 K to 1118 K at 1 bar). The standard deviation of the liftoff height also reduces for an increase in either the background pressure or the co-flow temperature, which indicates that the liftoff height is more stable at higher background pressures and co-flow temperatures. As far as the experimental tests on the nonreaction jet flow is concerned, the jet velocity becomes extinct faster as the background pressure rises, which is consistent with the decrease in the liftoff height as the background pressure grows. The evolution of the jet velocity has been proved to be another important factor that affects the liftoff height under different background pressures (physical factor), in addition to the fuel autoignition delay (chemical factor). The simulation data led with a Reynolds-averaged Navier–Stokes (RANS)/probability density function (PDF) model show that an increment in the background pressure makes the temperatures increase and induces a brighter yellow part of lifted flame, which leads to more soot production. This proves that the flame is not completely premixed. On the other hand, the Schlieren images of the non-reaction jet flow highlight that the flame is partially premixed, since the edge of the jet is not well defined, as the jet penetration increases with time. The liftoff height values of the flame in the numerical simulations were found to be generally higher than those measured in the corresponding experiments. This discrepancy was caused by an appreciable radiation heat loss at the thermocouple. A correlation was therefore developed for the thermocouple temperature measurement in order to correct the inaccuracy.

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Journal articles on the topic 'Chemical autoignition delay'

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