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Eric L Petersen - One of the best experts on this subject based on the ideXlab platform.
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ignition delay times Laminar Flame speeds and species time histories in the h2s ch4 system at atmospheric pressure
Proceedings of the Combustion Institute, 2019Co-Authors: Clayton R Mulvihill, Olivier Mathieu, Charles L Keesee, Travis Sikes, Rodolfo S Teixeira, Eric L PetersenAbstract:Abstract Hydrogen sulfide (H 2 S) composes up to 30% of certain natural-gas resources (“sour gas”) and can considerably alter combustion properties of methane (CH 4 ), but few data on H 2 S/CH 4 are available in the literature. In this work, new shock-tube and Laminar Flame speed data were obtained to facilitate future model validation. For the shock-tube experiments, a fuel-lean (φ = 0.5) 30/70 H 2 S/CH 4 blend in 99% argon by volume was shock-heated to temperatures between 1538 and 2144 K and pressures near 1 atm. Laser absorption diagnostics at 4.5 and 1.4 µm were employed to measure CO and H 2 O time-histories, respectively. OH* chemiluminescence profiles were measured using an emission diagnostic at 307 nm. For the Laminar Flame speed experiments, measurements were carried out in a constant-volume vessel at 295 K and 1 atm for CH 4 /argon and H 2 S/CH 4 /argon (8.25% H 2 S) mixtures from φ = 0.7 to φ = 1.4. The predictions of several recent chemical kinetics mechanisms were compared to the data, leading to the conclusion that species containing both carbon and sulfur are unimportant for shock-tube conditions but can be quite influential for Laminar Flames. By combining the modeling efforts of two recent works, a tentative new model is proposed that shows marked improvement over the older models in terms of shock-tube ignition delay times. Flame speed predictions show a discrepancy with the new model but follow general experimental trends. To the best of the authors’ knowledge, this study provides the first shock-tube data and Laminar Flame speeds measured in the H 2 S/CH 4 system.
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an experimental study Laminar Flame speed sensitivity from spherical Flames in stoichiometric ch4 air mixtures
Combustion Science and Technology, 2018Co-Authors: Travis Sikes, Sam M Mannan, Eric L PetersenAbstract:ABSTRACTFurther improvements in modern chemical kinetics mechanisms using Laminar Flame speeds require an understanding of the uncertainty and precision of the measurement and hence its limitations. From an inspection of the literature, it was found that Laminar Flame speed values of a basic methane–air mixture could depend on what measuring technique is employed. One way to reconcile these differences and understand the limitations of the various techniques is to quantify both their uncertainties and sensitivities to various parameters such as vessel size, detailed data reduction method, and igniter influences. To this end, a detailed experimental sensitivity analysis of a spherically expanding Flame experiment and its contributing factors was performed. A simple mixture involving stoichiometric CH4–air was emphasized since there is still unreasonable uncertainty in its Laminar Flame speed and those measured values from spherical Flames are consistently lower than those observed through the years with ot...
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experimental and chemical kinetics study of the effects of halon 1211 cf2brcl on the Laminar Flame speed and ignition of light hydrocarbons
Journal of Physical Chemistry A, 2015Co-Authors: Olivier Mathieu, Charles L Keesee, Claire Gregoire, Eric L PetersenAbstract:In this study, the effect of Halon 1211 (CF2BrCl) on the ignition delay time and Laminar Flame speed of CH4, C2H4, and C3H8 were investigated experimentally for the first time. The results showed that the effects of Halon 1211 on the ignition delay time are strongly dependent on the hydrocarbon: the ignition delay time of CH4 is significantly decreased by Halon 1211 addition, while a significant increase in the ignition delay time was observed with C2H4 for the lowest temperatures investigated. Ignition delay times for C3H8 were slightly increased, mostly on the low-temperature side and for the fuel-rich case. A significant reduction in the Laminar Flame speed was observed for all of the fuels. A tentative chemical kinetics model was assembled from existing models and completed with reactions that have been determined in the literature or estimated when necessary. The experimental results were reproduced satisfactorily by the model, and a chemical analysis showed that most of the effects of Halon 1211 on ...
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ignition delay times Laminar Flame speeds and mechanism validation for natural gas hydrogen blends at elevated pressures
Combustion and Flame, 2014Co-Authors: Nicola Donohoe, Henry J Curran, Eric L Petersen, Wayne K Metcalfe, Olivier Mathieu, Alexander Heufer, Marissa L Davis, Drew Plichta, Anibal Morones, Felix GutheAbstract:New experimental ignition delay time data measured in both a shock tube and in a rapid compression machine were taken to determine the increase in reactivity due to the addition of hydrogen to mixtures of methane and natural gas. Test conditions were determined using a statistical design of experiments approach which allows the experimenter to probe a wide range of variable factors with a comparatively low number of experimental trials. Experiments were performed at 1, 10, and 30 atm in the temperature range 850–1800 K, at equivalence ratios of 0.3, 0.5, and 1.0 and with dilutions ranging from 72% to 90% by volume. Pure methane- and hydrogen-fueled mixtures were prepared in addition to two synthetic ‘natural gas’-fueled mixtures comprising methane, ethane, propane, n-butane and n-pentane, one comprising 81.25/10/5/2.5/1.25% while the other consisted of 62.5/20/10/5/2.5% C1=C2=C3=C4=C5 components to encompass a wide range of possible natural gas compositions. A heated, constant-volume combustion vessel was also utilized to experimentally determine Laminar Flame speed for the same baseline range of fuels. In this test, a parametric sweep of equivalence ratio, 0.7–1.3, was conducted at each condition, and the hydrogen content was varied from 50% to 90% by volume. The initial temperature and pressure varied from 300 to 450 K and 1 to 5 atm, respectively. Flame speed experiments conducted above atmospheric pressure utilized a 1:6 oxygen-to-helium ratio to curb the hydrodynamic and thermal instabilities that arise when conducting Laminar Flame speed experiments. All experiments were simulated using a detailed chemical kinetic model. Overall good agreement is observed between the simulations and the experimental results. A discussion of the important reactions promoting and inhibiting reactivity is included.
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numerical study on the effect of real syngas compositions on ignition delay times and Laminar Flame speeds at gas turbine conditions
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2013Co-Authors: Olivier Mathieu, Henry J Curran, Eric L Petersen, Wayne K Metcalfe, Felix Guthe, Alexander Heufer, Nicola Donohoe, Gilles BourqueAbstract:Depending on the feedstock and the production method, the composition of syngas can include (in addition to H2 and CO) small hydrocarbons, diluents (CO2, water, and N2), and impurities (H2S, NH3, NOx, etc.). Despite this fact, most of the studies on syngas combustion do not include hydrocarbons or impurities and in some cases not even diluents in the fuel mixture composition. Hence, studies with realistic syngas composition are necessary to help in designing gas turbines. The aim of this work was to investigate numerically the effect of the variation in the syngas composition on some fundamental combustion properties of premixed systems such as Laminar Flame speed and ignition delay time at realistic engine operating conditions. Several pressures, temperatures, and equivalence ratios were investigated for the ignition delay times, namely 1, 10, and 35 atm, 900–1400 K, and ϕ = 0.5 and 1.0. For Laminar Flame speed, temperatures of 300 and 500 K were studied at pressures of 1 atm and 15 atm. Results showed that the addition of hydrocarbons generally reduces the reactivity of the mixture (longer ignition delay time, slower Flame speed) due to chemical kinetic effects. The amplitude of this effect is, however, dependent on the nature and concentration of the hydrocarbon as well as the initial condition (pressure, temperature, and equivalence ratio).
Zheng Chen - One of the best experts on this subject based on the ideXlab platform.
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Laminar Flame speeds of methane air mixtures at engine conditions performance of different kinetic models and power law correlations
Combustion and Flame, 2020Co-Authors: Yiqing Wang, Fokion N. Egolfopoulos, Ashkan Movaghar, Ziyu Wang, Zefang Liu, Wenting Sun, Zheng ChenAbstract:Abstract The Laminar Flame speed is an important input in turbulent premixed combustion modelling of spark ignition engines. At engine-relevant temperatures and pressures, its measurement is challenging or not possible and thereby it is usually obtained from simulations based on chemical models or power-law correlations. This work aims to investigate the performance of different models and power-law correlations in terms of predicting Laminar Flame speeds of methane/air at engine conditions. The propagation of spherically expanding Laminar Flames in a closed chamber was simulated and Laminar Flame speeds were computed over a broad range of pressures (1-120 atm) and temperatures (300-1100 K) for methane/air mixtures based on seven kinetic models. It was found that at engine conditions, there are notable discrepancies among the predictions. GRI Mech. 3.0 and USC Mech. II respectively predict the largest and smallest values at high pressure conditions. This was explained by the difference in CH3 oxidation and recombination according to reaction pathway analysis. Additionally, Laminar Flame speeds of methane Flames were experimentally determined under engine-relevant conditions. It was shown that the recently developed Foundational Fuel Chemistry Model Version 1.0 model predicts closely the data at high pressures and temperatures. Therefore, it was chosen as the reference model for the comparisons. Thirteen published power-law correlations for Laminar Flame speeds of CH4/air were implemented, and their performance in predicting the Laminar Flame speeds at engine conditions was investigated. Most of these correlations have been derived for a narrow range of temperatures and pressures, which are lower than those encountered in engines. A new power-law correlation was derived based on predictions by the Foundational Fuel Chemistry Model Version 1.0. This new correlation is expected to provide reliable predictions at engine conditions for a stoichiometric methane/air mixture and thereby it is recommended to be used in modeling turbulent premixed combustion in spark-ignition engine simulations.
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effects of pressure rise rate on Laminar Flame speed under normal and engine relevant conditions
Combustion Theory and Modelling, 2020Co-Authors: Yiqing Wang, Jagannath Jayachandran, Zheng ChenAbstract:Laminar Flame speed (LFS) is one of the most important physicochemical properties of a combustible mixture. At normal and elevated temperatures and pressures, LFS can be measured using propagating ...
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two stage heat release in nitromethane air Flame and its impact on Laminar Flame speed measurement
Combustion and Flame, 2017Co-Authors: Mahdi Faghih, Zheng ChenAbstract:Abstract In premixed Flames of most hydrocarbon fuels, there is only one stage heat release. However, two-stage heat release occurs in premixed nitromethane/air Flames under certain conditions. In this study, numerical simulations were conducted for one-dimensional planar and spherical nitromethane/air Flames at different initial temperatures (423∼800 K), pressures (0.5∼10 atm) and equivalence ratios (0.5∼1.3). Using the planar Flame, we investigated the characteristics of the two-stage heat release and identified elementary reactions involved in these two stages. It was found that the occurrence of two-stage heat release strongly depends on the equivalence ratio and that single-stage heat release occurs for very fuel-lean mixture. To demonstrate the key reactions involved in the second stage heat release, we modified the original chemical mechanism and compared the results predicted by different mechanisms. The second stage heat release was found to be mainly caused by the reaction NO+H→N+OH. Using the propagating spherical Flame, we assessed the impact of two-stage heat release on the determination of Laminar Flame speed. The positive burned gas speed induced by the second stage heat release was shown to affect the accuracy of Laminar Flame speed determined by traditional method neglecting burned gas speed and using the density ratio at equilibrium condition. Alternative methods were proposed and used to correct the experimental data reported in the literature.
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effects of radiation absorption on spherical Flame propagation and radiation induced uncertainty in Laminar Flame speed measurement
Proceedings of the Combustion Institute, 2017Co-Authors: Zheng ChenAbstract:Abstract Outwardly propagating spherical Flames are popularly used to measure the Laminar Flame speed, especially for high pressure conditions. Since radiation always exists in spherical Flame experiments, the accuracy of Laminar Flame speed measurement is inherently affected by radiation. In this study, the radiation-induced uncertainty in Laminar Flame speed measurement was investigated numerically. We focused on CO 2 diluted mixtures in which the radiation absorption effects are important. The outwardly propagating spherical Flames of different CO 2 diluted mixtures at a broad range of pressure up to 25 atm were simulated. Different fuels (hydrogen, methane, dimethyl ether and iso-octane) with different amounts of CO 2 dilution were considered and detailed chemistry was included in simulation. Two radiation models were used: one is the optically thin model considering only radiation emission and the other is the statistical narrow band model considering both radiation emission and absorption. The effects of radiation absorption on spherical Flame propagation and radiation-induced uncertainty in Laminar Flame speed measurement were quantified through comparison among results predicted by these two radiation models. It was found that for CO 2 diluted mixtures, radiation absorption has great impact on spherical Flame propagation: it greatly reduces the radiation-induced thermal and flow effects. The influence of radiation absorption was show to be stronger at higher pressure. When only radiation emission is considered and radiation absorption is neglected, the radiation-induced uncertainty in Laminar Flame speed measurement is substantially over-predicted for CO 2 diluted mixtures. When radiation absorption is included, the radiation-induced uncertainty in Laminar Flame speed measurement is nearly negligible (within 2.5%) for all the CO 2 diluted mixtures considered in this study.
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The constant-volume propagating spherical Flame method for Laminar Flame speed measurement
Science Bulletin, 2016Co-Authors: Faghih, Zheng ChenAbstract:Laminar Flame speed is one of the most important intrinsic properties of a combustible mixture. Due to its importance, different methods have been developed to measure the Laminar Flame speed. This paper reviews the constant-volume propagating spherical Flame method for Laminar Flame speed measurement. This method can be used to measure Laminar Flame speed at high pressures and temperatures which are close to engine-relevant conditions. First, the propagating spherical Flame method is introduced and the constant-volume method (CVM) and constant-pressure method (CPM) are compared. Then, main groups using the constant-volume propagating spherical Flame method are introduced and large discrepancies in Laminar Flame speeds measured by different groups for the same mixture are identified. The sources of discrepancies in Laminar Flame speed measured by CVM are discussed and special attention is devoted to the error encountered in data processing. Different correlations among burned mass fraction, pressure, temperature and Flame speed, which are used by different researchers to obtain Laminar Flame speed, are summarized. The performance of these correlations are examined, based on which recommendations are given. Finally, recommendations for future studies on the constant-volume propagating spherical Flame method for Laminar Flame speed measurement are presented.
Zuohua Huang - One of the best experts on this subject based on the ideXlab platform.
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comparative study on the Laminar Flame speeds of methylcyclohexane methanol and toluene methanol blends at elevated temperatures
Fuel, 2019Co-Authors: Yemiao Zhang, Hu Liu, Zhiyu Yan, Zuohua HuangAbstract:Abstract Laminar Flame speeds of methylcyclohexane (MCH)-methanol and toluene-methanol blends were experimentally determined with spherically expanding Flame method in a constant volume bomb at atmospheric pressure, initial temperatures of 393 and 433 K, covering wide equivalence ratio range. The blending ratio of methanol in liquid volume varies as 0%, 20%, 40%, 60%, 80%, 100%. Nonlinear methodology was employed to remove the stretch effect in the data processing. Experimental results show that MCH-air Flame propagates faster than toluene at the same condition. The addition of methanol into MCH and toluene results in acceleration of Laminar Flame speed especially at the rich mixtures. Since the published model suffers difficulty in reproducing experimental data, model refinements were carried out and the refined model yields better performance. Comprehensive analyses were developed regarding thermal and chemical kinetic properties. For MCH has lower adiabatic Flame temperature than toluene and methanol addition into the two cyclic fuels decreases the adiabatic Flame temperature, the thermal effect on Laminar Flame speed difference is negligible. Therefore, the effect of chemical kinetics was specifically discussed. MCH and toluene have different ring structures. The disintegration of aromatic ring plays as the limiting step in the high-temperature oxidation of toluene, resulting in low concentration of active radical pool and overall reactivity. However, the ring opening reaction of MCH occurs easily after the initial H-abstraction reaction, which favors the production of active intermediates and the enhancement of Flame propagation. For the blending fuels, the analyses show that the Laminar Flame speed variation of the blends are primarily caused by the methanol substitution and the disturbance of reaction pathway through affecting the generation of important intermediates.
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Laminar Flame characteristics and kinetic modeling study of methanol isooctane blends at elevated temperatures
Fuel, 2016Co-Authors: Weijie Zhang, Yongliang Xie, Wu Jin, Zuohua HuangAbstract:Abstract Laminar Flame speeds of methanol-isooctane blends were experimentally determined using the spherically propagating Flame in a constant volume chamber at two initial temperatures (363 and 393 K), different blending ratios of methanol in liquid volume (0%, 20%, 40%, 80%, 100%), and over equivalence ratios of 0.7–1.6. Nonlinear methodology was employed to remove the stretch effect in the data processing. Results indicate that Laminar Flame speeds of methanol Flame reach the peak at equivalence ratio around 1.2 and that of isooctane at equivalence ratio around 1.1. For the mixtures with less than 40% methanol, Laminar Flame speeds show moderate increase at all equivalence ratios. However, further increasing methanol addition will greatly accelerate Laminar Flame speeds at rich mixture sides but give slight change at lean mixture sides. Markstein length shows an increase tendency with the methanol addition at the equivalence ratios larger than a critical value while Markstein length gives a decrease tendency at the equivalence ratios smaller than the critical value. The critical equivalence ratio is between 1.2 and 1.3. Among the thermal effect, diffusive effect and kinetic effect, the kinetic effect was found to be the major factor bringing the variation of Laminar Flame speed with the variation of blending ratio. A kinetic model (IM model) was developed on the basis of the isooctane model of Chaos et al. (2007). The IM model shows good prediction on measured Laminar Flame speeds under all conditions. Reaction pathway reveals that the HCO and H productions are promoted while the productions of stable species are inhibited in the case of methanol addition into the isooctane at rich mixture sides, resulting in the Laminar Flame speed enhancement. These behaviors are verified from the sensitivity analysis and the concentrations of the reactive radicals.
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Laminar Flame characteristics of c1 c5 primary alcohol isooctane blends at elevated temperature
Energies, 2016Co-Authors: Wu Jin, Zuohua HuangAbstract:The Laminar combustion characteristics of blends of isooctane and C1–C5 primary alcohols (i.e., methanol, ethanol, n-propanol, n-butanol and n-pentanol) were investigated using the spherical expanding Flame methodology in a constant volume chamber at various equivalence ratios and volume fractions of alcohol. The stretch effect was removed using the nonlinear methodology. The results indicate that the Laminar Flame speeds of alcohol-isooctane blends increase monotonously with the increasing volume fraction of alcohol. Among the five alcohols, the addition of methanol is identified to be the most effective in enhancing Laminar Flame speed. The addition of ethanol results in an approximately equivalent Laminar Flame speed enhancement rate as those of n-propanol, n-butanol and n-pentanol at ratios of 0.8 and 1.5, and a higher rate at 1.0 and 1.2. An empirical correlation is provided to describe the Laminar Flame speed variation with the volume fraction of alcohol. Meanwhile, the Laminar Flame speed increases with the mass content of oxygen in the fuel blends. At the equivalence ratio of 0.8 and fixed oxygen content, similar Laminar Flame speeds are observed with different alcohols blended into isooctane. Nevertheless, with the increase of equivalence ratio, heavier alcohol-isooctane blends tend to exhibit higher values. Markstein lengths of alcohol-isooctane blends decrease with the addition of alcohol into isooctane at 0.8, 1.0 and 1.2, however they increase at 1.5. This is consistent with the behavior deduced from the Schlieren images.
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Laminar Flame speeds and ignition delay times of methane air mixtures at elevated temperatures and pressures
Fuel, 2015Co-Authors: Erjiang Hu, Yu Cheng, Xiaotian Li, Xin Meng, Yizhen Chen, Zuohua HuangAbstract:Abstract Measurements on Laminar Flame speeds and ignition delay times of methane/air mixtures at elevated pressures and temperatures were carried out in a constant volume bomb and shock tube. The performances of GRI Mech 3.0, USC Mech II, and Aramco Mech 1.3 mechanisms were also evaluated from the data obtained. Results showed that the measured Laminar Flame speeds from the constant volume bomb by the linear method are slightly higher than those from the counter flow Flame at rich mixtures and lower at lean mixtures. At rich mixtures, the Laminar Flame speeds with linear method are higher than that with non-linear method. The available mechanisms give slight overprediction to the constant volume bomb data at lean mixtures, and large underprediction at rich mixtures at elevated temperatures and pressures. Overall reaction order decreases and then increases with the rising of pressure from 0.1 to 10.0 MPa because of the chain reaction mechanism. For the ignition delay times, the three mechanisms are in good accordance with the experimental data of lean and stoichiometric mixtures at atmospheric pressure, while the discrepancy between calculation and measurement is increased at elevated pressures. These mechanisms seem to lack good sensitivity to the rich mixtures, especially at elevated pressures. Correlations for Laminar burning velocities and ignition delay time of methane–air mixtures are provided.
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effects of hydrogen addition on the Laminar Flame speed and markstein length of premixed dimethyl ether air Flames
Energy & Fuels, 2015Co-Authors: Yu Cheng, Xinyi Zhang, Ke Yang, Zuohua HuangAbstract:Laminar Flame speeds of premixed dimethyl ether/hydrogen/air Flames were measured in a constant volume bomb at different temperatures, equivalence ratios, and hydrogen blending ratios. Results reveal that Laminar Flame speeds increase with an increased hydrogen blending ratio and initial temperature. The Wang model and Zhao model both perform well in predicting Laminar Flame speeds of the blends. Furthermore, three different models for an effective Lewis number are validated, and the volume-fraction-weighted model performs well in predicting the Markstein length. The effects of hydrogen addition on the Flame speed and Markstein length of fuel blends are systematically studied. The chemical kinetic effect induced by hydrogen addition plays a dominant role in increasing the Laminar Flame speed in comparison to thermal and diffusive effects. In addition, there exists a critical equivalence ratio in the trend of the Markstein length. At the equivalence ratio less than the critical equivalence ratio, the Marks...
Chung King Law - One of the best experts on this subject based on the ideXlab platform.
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Laminar Flame propagation in supercritical hydrogen air and methane air mixtures
Proceedings of the Combustion Institute, 2019Co-Authors: Wenkai Liang, Chung King LawAbstract:Abstract The propagation of Laminar hydrogen/air and methane/air Flames in supercritical conditions was computationally simulated for the planar Flame configurations, incorporating descriptions of supercritical thermodynamics and transport as well as high-pressure chemical kinetics. The inaccuracies associated with the use of ideal gas assumptions for various components of the supercritical description were systematically assessed with progressively more complete formulation. Results show that, for hydrogen/air Flames, the Laminar Flame speeds at high pressures increase due to the non-ideal equation of state (EoS), and is mainly due to the density modification of the initial mixture. Including the thermodynamic properties of heat capacity reduces the Flame speed because of the correspondingly reduced adiabatic Flame temperature. Transport properties were found to have small effect because of the inherent insensitivity of the Laminar burning rate to variations in the transport properties. For methane/air Flames, the use of recently reported high-pressure chemical kinetics considerably affects the Laminar Flame speed, even for the same Flame temperature.
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hierarchical and comparative kinetic modeling of Laminar Flame speeds of hydrocarbon and oxygenated fuels
Progress in Energy and Combustion Science, 2012Co-Authors: E. Ranzi, Andrew P Kelley, Chung King Law, A. Frassoldati, R. Grana, A. Cuoci, T. FaravelliAbstract:The primary objective of the present endeavor is to collect, consolidate, and review the vast amount of experimental data on the Laminar Flame speeds of hydrocarbon and oxygenated fuels that have been reported in recent years, analyze them by using a detailed kinetic mechanism for the pyrolysis and combustion of a large variety of fuels at high temperature conditions, and thereby identify aspects of the mechanism that require further revision. The review and assessment was hierarchically conducted, in the sequence of the foundational C0–C4 species; the reference fuels of alkanes (n-heptane, iso-octane, n-decane, n-dodecane), cyclo-alkanes (cyclohexane and methyl-cyclo-hexane) and the aromatics (benzene, toluene, xylene and ethylbenzene); and the oxygenated fuels of alcohols, C3H6O isomers, ethers (dimethyl ether and ethyl tertiary butyl ether), and methyl esters up to methyl decanoate. Mixtures of some of these fuels, including those with hydrogen, were also considered. The comprehensive nature of the present mechanism and effort is emphasized.
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non premixed ignition Laminar Flame propagation and mechanism reduction of n butanol iso butanol and methyl butanoate
Proceedings of the Combustion Institute, 2011Co-Authors: Wei Liu, Andrew P Kelley, Chung King LawAbstract:The non-premixed ignition temperature of n-butanol (CH3CH2CH2CH2OH), iso-butanol ((CH3)2CHCH2OH) and methyl butanoate (CH3CH2CH2COOCH3) was measured in a liquid pool assembly by heated oxidizer in a stagnation flow for system pressures of 1 and 3 atm. In addition, the stretch-corrected Laminar Flame speeds of mixtures of air–n-butanol/iso-butanol/methyl butanoate were determined from the outwardly propagating spherical Flame at initial pressures of up to 2 atm, for an extensive range of equivalence ratio. The ignition temperature and Laminar Flame speeds of n-butanol and methyl butanoate were computationally simulated with three recently developed kinetic mechanisms in the literature. Dominant reaction pathways to ignition and Flame propagation were identified and discussed through a chemical explosive mode analysis (CEMA) and sensitivity analysis. The detailed models were further reduced through a series of systematic strategies. The reduced mechanisms provided excellent agreement in both homogeneous and diffusive combustion environments and greatly improved the computation efficiency.
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Laminar Flame speeds non premixed stagnation ignition and reduced mechanisms in the oxidation of iso octane
Proceedings of the Combustion Institute, 2011Co-Authors: Andrew P Kelley, Wei Liu, Andrew Smallbone, Chung King LawAbstract:Abstract Experimental data on the Laminar Flame speeds of iso-octane/air mixtures at atmospheric and elevated pressures were acquired using the counterflow Flame and the outwardly expanding Flame, while the non-premixed ignition temperatures were determined for an iso-octane pool in the stagnation flow of a heated air jet at atmospheric and slightly reduced/elevated pressures. These experimental measurements were compared with calculations based on the mechanisms of Curran et al. and Chaos et al., with the former mechanism systematically and substantially reduced, using directed relation graph and computational singular perturbation, to facilitate the calculation. It was found that the Curran mechanism yielded substantially higher Laminar Flames speeds as compared to the present experimental results while results from the Chaos mechanism agree well with the present measurements. These trends are in agreement with previous results on the Laminar Flame speeds for n-heptane. Both mechanisms yield acceptable comparison with the observed non-premixed stagnation ignition temperature.
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Laminar Flame speeds of c5 to c8 n alkanes at elevated pressures experimental determination fuel similarity and stretch sensitivity
Proceedings of the Combustion Institute, 2011Co-Authors: Andrew P Kelley, Andrew Smallbone, Delin Zhu, Chung King LawAbstract:Abstract Experimental data of high fidelity on the Laminar Flame speeds and Markstein lengths of C5–C8 n-alkane mixtures with air at elevated pressures were determined from the propagation velocities of spark-ignited, expanding Flames in a newly-designed heated, high- and constant-pressure chamber, using nonlinear extrapolation. Results show that the Laminar Flame speeds of these fuels are basically similar, hence extending previous observations of the fuel similarity to the high-pressure range of 10–20 atm. A companion analysis of the computed Flame structure reveals comparable similarity for the thermal properties as well as the key intermediates and reactions, thereby supporting the observed global Flame speed similarity. The study further shows that the influence of stretch diminishes with increasing pressure because of the concomitant reduction of the Flame thickness, implying not only reduced error in the determination of Laminar Flame speeds from stretched Flames at elevated pressures, but also substantial simplification in the modeling of turbulent Flames because of the diminished importance of stretch.
Felix Guthe - One of the best experts on this subject based on the ideXlab platform.
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ignition delay times Laminar Flame speeds and mechanism validation for natural gas hydrogen blends at elevated pressures
Combustion and Flame, 2014Co-Authors: Nicola Donohoe, Wayne K Metcalfe, Eric L Peterse, Alexande Heufe, Henry J Curra, Marissa L Davis, Olivie Mathieu, Drew Plichta, Anibal Morones, Felix GutheAbstract:New experimental ignition delay time data measured in both a shock tube and in a rapid compression machine were taken to determine the increase in reactivity due to the addition of hydrogen to mixtures of methane and natural gas. Test conditions were determined using a statistical design of experiments approach which allows the experimenter to probe a wide range of variable factors with a comparatively low number of experimental trials. Experiments were performed at 1, 10, and 30 atm in the temperature range 850–1800 K, at equivalence ratios of 0.3, 0.5, and 1.0 and with dilutions ranging from 72% to 90% by volume. Pure methane- and hydrogen-fueled mixtures were prepared in addition to two synthetic ‘natural gas’-fueled mixtures comprising methane, ethane, propane, n-butane and n-pentane, one comprising 81.25/10/5/2.5/1.25% while the other consisted of 62.5/20/10/5/2.5% C1=C2=C3=C4=C5 components to encompass a wide range of possible natural gas compositions. A heated, constant-volume combustion vessel was also utilized to experimentally determine Laminar Flame speed for the same baseline range of fuels. In this test, a parametric sweep of equivalence ratio, 0.7–1.3, was conducted at each condition, and the hydrogen content was varied from 50% to 90% by volume. The initial temperature and pressure varied from 300 to 450 K and 1 to 5 atm, respectively. Flame speed experiments conducted above atmospheric pressure utilized a 1:6 oxygen-to-helium ratio to curb the hydrodynamic and thermal instabilities that arise when conducting Laminar Flame speed experiments. All experiments were simulated using a detailed chemical kinetic model. Overall good agreement is observed between the simulations and the experimental results. A discussion of the important reactions promoting and inhibiting reactivity is included.
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ignition delay times Laminar Flame speeds and mechanism validation for natural gas hydrogen blends at elevated pressures
Combustion and Flame, 2014Co-Authors: Nicola Donohoe, Henry J Curran, Eric L Petersen, Wayne K Metcalfe, Olivier Mathieu, Alexander Heufer, Marissa L Davis, Drew Plichta, Anibal Morones, Felix GutheAbstract:New experimental ignition delay time data measured in both a shock tube and in a rapid compression machine were taken to determine the increase in reactivity due to the addition of hydrogen to mixtures of methane and natural gas. Test conditions were determined using a statistical design of experiments approach which allows the experimenter to probe a wide range of variable factors with a comparatively low number of experimental trials. Experiments were performed at 1, 10, and 30 atm in the temperature range 850–1800 K, at equivalence ratios of 0.3, 0.5, and 1.0 and with dilutions ranging from 72% to 90% by volume. Pure methane- and hydrogen-fueled mixtures were prepared in addition to two synthetic ‘natural gas’-fueled mixtures comprising methane, ethane, propane, n-butane and n-pentane, one comprising 81.25/10/5/2.5/1.25% while the other consisted of 62.5/20/10/5/2.5% C1=C2=C3=C4=C5 components to encompass a wide range of possible natural gas compositions. A heated, constant-volume combustion vessel was also utilized to experimentally determine Laminar Flame speed for the same baseline range of fuels. In this test, a parametric sweep of equivalence ratio, 0.7–1.3, was conducted at each condition, and the hydrogen content was varied from 50% to 90% by volume. The initial temperature and pressure varied from 300 to 450 K and 1 to 5 atm, respectively. Flame speed experiments conducted above atmospheric pressure utilized a 1:6 oxygen-to-helium ratio to curb the hydrodynamic and thermal instabilities that arise when conducting Laminar Flame speed experiments. All experiments were simulated using a detailed chemical kinetic model. Overall good agreement is observed between the simulations and the experimental results. A discussion of the important reactions promoting and inhibiting reactivity is included.
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numerical study on the effect of real syngas compositions on ignition delay times and Laminar Flame speeds at gas turbine conditions
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2013Co-Authors: Olivier Mathieu, Henry J Curran, Eric L Petersen, Wayne K Metcalfe, Felix Guthe, Alexander Heufer, Nicola Donohoe, Gilles BourqueAbstract:Depending on the feedstock and the production method, the composition of syngas can include (in addition to H2 and CO) small hydrocarbons, diluents (CO2, water, and N2), and impurities (H2S, NH3, NOx, etc.). Despite this fact, most of the studies on syngas combustion do not include hydrocarbons or impurities and in some cases not even diluents in the fuel mixture composition. Hence, studies with realistic syngas composition are necessary to help in designing gas turbines. The aim of this work was to investigate numerically the effect of the variation in the syngas composition on some fundamental combustion properties of premixed systems such as Laminar Flame speed and ignition delay time at realistic engine operating conditions. Several pressures, temperatures, and equivalence ratios were investigated for the ignition delay times, namely 1, 10, and 35 atm, 900–1400 K, and ϕ = 0.5 and 1.0. For Laminar Flame speed, temperatures of 300 and 500 K were studied at pressures of 1 atm and 15 atm. Results showed that the addition of hydrocarbons generally reduces the reactivity of the mixture (longer ignition delay time, slower Flame speed) due to chemical kinetic effects. The amplitude of this effect is, however, dependent on the nature and concentration of the hydrocarbon as well as the initial condition (pressure, temperature, and equivalence ratio).
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ignition delay time and Laminar Flame speed calculations for natural gas hydrogen blends at elevated pressures
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2013Co-Authors: Marissa L Brower, Henry J Curran, Eric L Petersen, Wayne K Metcalfe, Gilles Bourque, Marc Furi, Naresh Aluri, Felix GutheAbstract:Applications of natural gas and hydrogen co-firing have received increased attention in the gas turbine market, which aims at higher flexibility due to concerns over the availability of fuels. While much work has been done in the development of a fuels database and corresponding chemical kinetics mechanism for natural gas mixtures, there are nonetheless few if any data for mixtures with high levels of hydrogen at conditions of interest to gas turbines. The focus of the present paper is on gas turbine engines with primary and secondary reaction zones as represented in the Alstom and Rolls Royce product portfolio. The present effort includes a parametric study, a gas turbine model study, and turbulent Flame speed predictions. Using a highly optimized chemical kinetics mechanism, ignition delay times and Laminar burning velocities were calculated for fuels from pure methane to pure hydrogen and with natural gas/hydrogen mixtures. A wide range of engine-relevant conditions were studied: pressures from 1 to 30 atm, Flame temperatures from 1600 to 2200 K, primary combustor inlet temperature from 300 to 900 K, and secondary combustor inlet temperatures from 900 to 1400 K. Hydrogen addition was found to increase the reactivity of hydrocarbon fuels at all conditions by increasing the Laminar Flame speed and decreasing the ignition delay time. Predictions of turbulent Flame speeds from the Laminar Flame speeds show that hydrogen addition affects the reactivity more when turbulence is considered. This combined effort of industrial and university partners brings together the know-how of applied, as well as experimental and theoretical disciplines.
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ignition delay time and Laminar Flame speed calculations for natural gas hydrogen blends at elevated pressures
ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, 2012Co-Authors: Marissa L Brower, Henry J Curran, Eric L Petersen, Wayne K Metcalfe, Gilles Bourque, Marc Furi, Naresh Aluri, Felix GutheAbstract:Applications of natural gas and hydrogen co-firing have received increased attention in the gas turbine market, which aims at higher flexibility due to concerns over the availability of fuels. While much work has been done in the development of a fuels database and corresponding chemical kinetics mechanism for natural gas mixtures, there are nonetheless few if any data for mixtures with high levels of hydrogen at conditions of interest to gas turbines. The focus of the present paper is on gas turbine engines with primary and secondary reaction zones as represented in the Alstom and Rolls Royce product portfolio.The present effort includes a parametric study, a gas turbine model study, and turbulent Flame speed predictions. Using a highly optimized chemical kinetics mechanism, ignition delay times and Laminar burning velocities were calculated for fuels from pure methane to pure hydrogen and with natural gas/hydrogen mixtures. A wide range of engine-relevant conditions were studied: pressures from 1 to 30 atm, Flame temperatures from 1600 to 2200 K, primary combustor inlet temperature from 300 to 900 K, and secondary combustor inlet temperatures from 900 to 1400 K. Hydrogen addition was found to increase the reactivity of hydrocarbon fuels at all conditions by increasing the Laminar Flame speed and decreasing the ignition delay time. Predictions of turbulent Flame speeds from the Laminar Flame speeds show that hydrogen addition affects the reactivity more when turbulence is considered. This combined effort of industrial and university partners brings together the know-how of applied, as well as experimental and theoretical disciplines.Copyright © 2012 by ASME and Alstom Technologies Ltd.
