Experimental and modeling study on the pyrolysis and oxidation of n-decane and n-dodecane

High pressure n-decane and n-dodecane shock tube experiments were conducted to assist in the development of a Jet A surrogate kinetic model. Jet A is a kerosene based jet fuel composed of hundreds of hydrocarbons consisting of paraffins, olefins, aromatics and naphthenes. In the formulation of the surrogate mixture, n-decane or n-dodecane represent the normal paraffin class of hydrocarbons present in aviation fuels like Jet A. The experimental work on both n-alkanes was performed in a heated high pressure single pulse shock tube. The mole fractions of the stable species were determined using gas chromatography and mass spectroscopy. Experimental data on both n-decane and n-dodecane oxidation and pyrolysis were obtained for temperatures from 867 to 1739 K, pressures from 19 to 74 atm, reaction times from 1.15 to 3.47 ms, and equivalence ratios from 0.46 to 2.05, and ∞. Both n-decane and n-dodecane oxidation showed that the fuel decays through thermally driven oxygen free decomposition at the conditions studied. This observation prompted an experimental and modeling study of n-decane and n-dodecane pyrolysis using a recently submitted revised n-decane/iso-octane/toluene surrogate model. The surrogate model was extended to n-dodecane in order to facilitate the study of the species and the 1-olefin species quantified during the pyrolysis of n-dodecane and n-decane were revised with additional reactions and reaction rate constants modified with rate constants taken from literature. When compared against a recently published generalized n-alkane model and the original and revised surrogate models, the revised (based on our experimental work) and extended surrogate model showed improvements in predicting 1-olefin species profiles from pyrolytic and oxidative n-decane and n-dodecane experiments. The revised and extended model when compared to the published generalized n-alkane and surrogate models also showed improvements in predicting species profiles from flow reactor n-decane oxidation experiments, but similarly predicted n-decane and n-dodecane ignition delay times.     

Experimental study of the ignition of <Emphasis Type="Italic">n</Emphasis>-hexane- and <Emphasis Type="Italic">n</Emphasis>-decane-based surrogate fuels

Surrogate fuels on the basis of mixtures of n-hexane, n-decane, and benzene are fuels alternative to petroleum motor fuels, similar to the former in thermodynamic and kinetic properties. The fact the surrogate fuels are composed of a limited number of components makes it possible to develop both detailed and global kinetic mechanisms of their ignition in mixtures with oxidizers. In turn, the possibility of the kinetic modeling of the ignition of such fuels over wide temperature and pressure ranges is of critical importance for the numerical modeling of combustion-to-detonation transition phenomena. An experimental method for measuring ignition delay times of mixtures of air with liquid fuels with low vapor pressure under normal conditions is developed and tested. In the present work, the ignition of stoichiometric mixtures of air with n-hexane, n-decane, and surrogate fuels composed of 20% n-hexane and 80% n-decane, 20% benzene and 80% n-decane, and 9.1% n-hexane, 18.2% benzene, and 72.7% n-decane is experimentally investigated in a static reactor. The ignition delay time is determined by recording pressure oscillograms at temperatures of 530–1030 K and pressures of 1–9 atm.     

Experiments and modeling of ignition delay times, flame structure and intermediate species of EHN-doped stoichiometric n-heptane/air combustion

The combustion of stoichiometric Ethyl-hexyl-nitrate (EHN)-doped n-heptane/oxygen/argon and (EHN)-doped n-heptane/air mixtures, respectively, was investigated in a low-pressure burner with a molecular-beam mass spectrometer and ignition delay-time (τ_ign) measurements were performed in a high-pressure shock tube. The experiments with the low-pressure flame were used for the determination of the flame structure including concentration profiles of reactants, products and important intermediates in the flame. The shock tube experiments provided τ_ign for a temperature range of 690 K ? T ? 1275 K at a pressure of 40 ± 2 bar for stoichiometric and lean mixtures under engine relevant conditions. A chemical mechanism for n-heptane/EHN mixtures was developed from an automatically generated mechanism for n-heptane by manually adding reactions to describe the influence of EHN. This mechanism was validated against the shock-tube data for various temperatures, levels of EHN-doping and equivalence ratios by homogeneous reactor calculations.The ignition delay times predicted by the model agree well with the shock tube results for a large range of temperatures, equivalence ratios and EHN concentrations. The influence of EHN onto ignition delay was largest in the low-temperature regime (770-1000 K).Numerical analysis suggests that the prevalent reason for the ignition-enhancing effect of EHN is the formation of highly reactive heptyl radicals by thermal decomposition of EHN. Due to this comparatively simple and generic mechanism, EHN is expected to have a similar ignition-enhancing effect also for other hydrocarbon fuels.     

Autoignition of surrogate fuels at elevated temperatures and pressures

Autoignition of Jet-A and mixtures of benzene, hexane, and decane in air has been studied using a heated shock tube at mean post-shock pressures of 8.5 ± 1 atm within the temperature range of 1000–1700 K with the objective of identifying surrogate fuels for aviation kerosene. The influence of each component on ignition delay time and on critical conditions required for strong ignition of the mixture has been deduced from experimental observations. Correlation equation for Jet-A ignition times has been derived from the measurements. It is found that within the scatter of experimental data dilution of n-decane with benzene and n-hexane leads to slight increase in ignition times at low temperatures and does not change critical temperatures required for direct initiation of detonations in comparison with pure n-decane/air mixtures. Ignition times in 20% hexane/80% decane (HD), 20% benzene/80% decane (BD) and 18.2% benzene/9.1% hexane/72.7% decane (BHD) mixtures at temperature range of T  1450–1750 K correlate well with induction time of Jet-A fuel suggesting that these mixtures could serve as surrogates for aviation kerosene. At the same time, HD, BD and BHD surrogate fuels demonstrate a stronger autoignition and peak velocities of reflected shock front in comparison with Jet-A and n-decane/air mixtures.     

Autoignition of gasoline surrogate mixtures at intermediate temperatures and high pressures: Experimental and numerical approaches

Ignition-delay times were measured in shock-heated gases for a surrogate gasoline fuel comprised of ethanol/iso-octane/n-heptane/toluene at a composition of 40%/37.8%/10.2%/12% by liquid volume with a calculated octane number of 98.8. The experiments were carried out in stoichiometric mixtures in air behind reflected shock waves in a heated high-pressure shock tube. Initial reflected shock conditions were as follows: Temperatures of 690-1200 K, and pressures of 10, 30 and 50 bar, respectively. Ignition delay times were determined from CH^∗ chemiluminescence at 431.5 nm measured at a sidewall location. The experimental results are compared to simulated ignition delay times based on detailed chemical kinetic mechanisms. The main mechanism is based on the primary reference fuels (PRF) model, and sub-mechanisms were incorporated to account for the effect of ethanol and/or toluene. The simulations are also compared to experimental ignition-delay data from the literature for ethanol/iso-octane/n-heptane (20%/62%/18% by liquid volume) and iso-octane/n-heptane/toluene (69%/17%/14% by liquid volume) surrogate fuels. The relative behavior of the ignition delay times of the different surrogates was well predicted, but the simulations overestimate the ignition delay, mostly at low temperatures.     

On the chemical characteristics and dynamics of n-alkane low-temperature multistage diffusion flames

We demonstrate experimentally, perhaps for the first time, the existence of low-temperature multistage diffusion flames of n-alkanes. Multistage diffusion flames of n-heptane, n-decane, and n-dodecane are established in an atmospheric counterflow burner. Planar laser-induced fluorescence, chemiluminescence, and thermometry are used to probe the structures of such flames. In the first flame zone, the majority of the fuel is partially oxidized via low-temperature peroxy chemistry. In the second flame zone, the intermediate species produced are further oxidized via intermediate-temperature chemistry. The two stages of the flame are coupled such that significant fuel and oxidizer leakage occur, respectively, from the first and second reaction zones. The fuel is then further consumed, in the second stage, after the radical pool is replenished by the oxidation of the intermediates. The structure of the n-alkane multistage flame is found to be consistent with that previously observed for acyclic ethers. Owing to the different classes of temperature-dependent chemistries dominating the first and second stages, the reaction zone structure of multistage diffusion flames is dramatically influenced by the reactant concentrations and flame temperatures. The first stage is relatively favored at lower temperatures whereas the second stage is favored at elevated temperatures. Moreover, near extinction where the flame temperature is low, the multistage flame dynamics are controlled by the first oxidation stage, governed by peroxy chemistry, whereas the second oxidation stage, governed by intermediate chemistry, is dominant near high-temperature ignition conditions. Finally, by doping the oxidizer with ozone, we demonstrate the role of ozone doping on the multistage flame structure and the existence of a separate low-temperature ozone-assisted burning mode.     

Ignition limit and shock-to-detonation transition mode of n-heptane/air mixture in high-speed wedge flows

In this work, oblique detonation of n-heptane/air mixture in high-speed wedge flows is simulated by solving the reactive Euler equations with a two-dimensional (2D) configuration. This is a first attempt to model complicated hydrocarbon fuel oblique detonation waves (ODWs) with a detailed chemistry (44 species and 112 reactions). Effects of freestream equivalence ratios and velocities are considered, and the abrupt and smooth transition from oblique shock to detonation are predicted. Ignition limit, ODW characteristics, and predictability of the transition mode are discussed. Firstly, homogeneous constant-volume ignition calculations are performed for both fuel-lean and stoichiometric mixtures. The results show that the ignition delay generally increases with the wedge angle. However, a negative wedge angle dependence is observed, due to the negative temperature coefficient effects. The wedge angle range for successful ignition of n-heptane/air mixtures decreases when the wedge length is reduced. From two-dimensional simulations of stationary ODWs, the initiation length generally decreases with the freestream equivalence ratio, but the transition length exhibits weakly non-monotonic dependence. Smooth ODW typically occurs for lean conditions (equivalence ratio < 0.4). The interactions between shock/compression waves and chemical reaction inside the induction zone are also studied with the chemical explosive mode analysis. Moreover, the predictability of the shock-to-detonation transition mode is explored through quantifying the relation between ignition delay and chemical excitation time. It is demonstrated that the ignition delay (the elapsed time of the heat release rate, HRR, reaches the maximum) increases, but the excitation time (the time duration from the instant of 5% maximum HRR to that of the maximum) decreases with the freestream equivalence ratio for the three studied oncoming flow velocities. Smaller excitation time corresponds to stronger pressure waves from the ignition location behind the oblique shock. When the ratio of excitation time to ignition delay is high (e.g., > 0.5 for n-C₇H₁₆, > 0.3 for C₂H₂ and > 0.2 for H₂, based on the existing data compilation in this work), smooth transition is more likely to occur.     

Skeletal mechanism generation with CSP and validation for premixed n-heptane flames

An automated procedure has been previously developed to generate simplified skeletal reaction mechanisms for the combustion of n-heptane/air mixtures at equivalence ratios between 0.5 and 2.0 and different pressures. The algorithm is based on a Computational Singular Perturbation (CSP)-generated database of importance indices computed from homogeneous n-heptane/air ignition solutions. In this paper, we examine the accuracy of these simplified mechanisms when they are used for modeling laminar n-heptane/air premixed flames. The objective is to evaluate the accuracy of the simplified models when transport processes lead to local mixture compositions that are not necessarily part of the comprehensive homogeneous ignition databases. The detailed mechanism was developed by Curran et al. and involves 560 species and 2538 reactions. The smallest skeletal mechanism considered consists of 66 species and 326 reactions. We show that these skeletal mechanisms yield good agreement with the detailed model for premixed n-heptane flames, over a wide range of equivalence ratios and pressures, for global flame properties. They also exhibit good accuracy in predicting certain elements of internal flame structure, especially the profiles of temperature and major chemical species. On the other hand, we find larger errors in the concentrations of many minor/radical species, particularly in the region where low-temperature chemistry plays a significant role. We also observe that the low-temperature chemistry of n-heptane can play an important role at very lean or very rich mixtures, reaching these limits first at high pressure. This has implications to numerical simulations of non-premixed flames where these lean and rich regions occur naturally.     

Promotion of the self-ignition of fuel–air mixtures with mechanoactivated Al (Mg)–MoO<Subscript>3</Subscript> particles

The ignition delay times of heptane–air and diesel oil–air mixtures with and without additives of mechanoactivated Mg–MoO³, Al–MoO³, and Mg–fluoroplastic nanopowders are measured using a rapid-mixture-injection setup. At temperatures below a certain threshold value, the metal–MoO³ additives produce practically no effect on the ignition delay time, whereas at higher temperatures, these additives sharply reduce the ignition delay time, down to the resolution time of the experimental method. The promoting efficiency of the small heterogeneous additives tested is many times superior to that of the known homogeneous promoters. Magnesium–fluoroplastic additives are demonstrated to produce no promoting effect on the ignition of the fuel–air mixtures studied. The mechanism of the action of the heterogeneous additives on the gasphase self-ignition of fuels is discussed.     

n-Dodecane oxidation at high-pressures: Measurements of ignition delay times and OH concentration time-histories

Ignition delay times and OH concentration time-histories were measured during n-dodecane oxidation behind reflected shocks waves using a heated, high-pressure shock tube. Measurements were made over temperatures of 727-1422 K, pressures of 15-34 atm, and equivalence ratios of 0.5 and 1.0. Ignition delay times were measured using side-wall pressure and OH^∗ emission diagnostics, and OH concentration time-histories were measured using narrow-linewidth ring-dye laser absorption near the R-branchhead of the OH A-X (0, 0) system at 306.47 nm. Shock tube measurements were compared to model predictions of four current n-dodecane oxidation detailed mechanisms, and the differences, particularly in the low-temperature negative-temperature-coefficient (NTC) region where the influence of non-ideal facility effects can be significant, are discussed. To our knowledge, the current measurements provide the first gas-phase shock tube ignition delay times (at pressures above 13 atm) and quantitative OH concentration time-histories for n-dodecane oxidation under practical engine conditions, and hence provide benchmark validation targets for refinement of jet fuel detailed kinetic modeling, since n-dodecane is widely used as the principal representative for n-alkanes in jet fuel surrogates.     

High-speed imaging of n-heptane ignition in a high-pressure shock tube

Homogeneous and inhomogeneous ignition modes of n-heptane were studied using high-speed imaging in a high-pressure shock tube (HPST). n-Heptane, a fuel with strong negative temperature coefficient (NTC) behavior, was mixed with 4%-21% oxygen in argon or nitrogen and ignited over a wide temperature range (700–1250 K) and at elevated pressures (> 10 atm). Ultraviolet (UV) images of OH* emission were captured through a sapphire shock-tube end wall using a high-speed camera and a UV intensifier. The current study demonstrates the capability to study auto-ignition modes using high-speed imaging in a high-pressure shock tube. Both homogeneous and inhomogeneous auto-ignition events were observed with the latter generally confined to intermediate temperatures and reactive n-heptane mixtures. We also observed that conventional sidewall diagnostic signals are, in many cases, sufficient to identify inhomogeneous ignitions that are not accurately modeled under the assumption of spatially uniform chemistry.     

Speeds of sound and isothermal compressibility of ternary liquid systems: Application of Flory’s statistical theory and hard sphere models

Speeds of sound and densities of three ternary liquid systems namely, toluene + n-heptane + n-hexane (I), cyclohexane + n-heptane + n-hexane (II) and n-hexane + n-heptane + n-decane (III) have been measured as a function of the composition at 298.15 K at atmospheric pressure. The experimental isothermal compressibility has been evaluated from measured values of speeds of sound and density. The isothermal compressibility of these mixtures has also been computed theoretically using different models for hard sphere equations of state and Flory’s statistical theory. Computed values of isothermal compressibility have been compared with experimental findings. A satisfactory agreement has been observed. The superiority of Flory’s statistical theory has been established quite reasonably over hard sphere models.      

An experimental and modeling study of the shock tube ignition of a mixture of n-heptane and n-propylbenzene as a surrogate for a large alkyl benzene

Alkyl aromatics are an important chemical class in gasoline, jet and diesel fuels. In the present work, an n-propylbenzene and n-heptane mixture is studied as a possible surrogate for large alkyl benzenes contained in diesel fuels. To evaluate it as a surrogate, ignition delay times have been measured in a heated high pressure shock tube (HPST) for a mixture of 57% n-propylbenzene/43% n-heptane in air (≈21% O₂, ≈79% N₂) at equivalence ratios of 0.29, 0.49, 0.98 and 1.95 and compressed pressures of 1, 10 and 30 atm over a temperature range of 1000–1600 K. The effects of reflected-shock pressure and equivalence ratio on ignition delay time were determined and common trends highlighted. A combined n-propylbenzene and n-heptane reaction mechanism was assembled and simulations of the shock tube experiments were carried out. The simulation results showed very good agreement with the experimental data for ignition delay times. Sensitivity and reaction pathway analyses have been performed to reveal the important reactions responsible for fuel oxidation under the shock tube conditions studied. It was found that at 1000 K, the main consumption pathways for n-propylbenzene are abstraction reactions on the alkyl chain, with particular selectivity to the allylic site. In comparison at 1500 K, the unimolecular decomposition of the fuel is the main consumption pathway.     

Methyl concentration time-histories during iso-octane and n-heptane oxidation and pyrolysis

Methyl radical concentration time-histories were measured during the oxidation and pyrolysis of iso-octane and n-heptane behind reflected shock waves. Initial reflected shock conditions covered temperatures of 1100-1560 K, pressures of 1.6-2.0 atm and initial fuel concentrations of 100-500 ppm. Methyl radicals were detected using cw UV laser absorption near 216 nm; three wavelengths were used to compensate for time- and wavelength-dependent interference absorption. Methyl time-histories were compared to the predictions of several current oxidation models. While some agreement was found between modeling and measurement in the early rise, peak and plateau values of methyl, and in the ignition time, none of the current mechanisms accurately recover all of these features. Sensitivity analysis of the ignition times for both iso-octane and n-heptane showed a strong dependence on the reaction C₃H₅ + H = C₃H₄ + H₂, and a recommended rate was found for this reaction. Sensitivity analysis of the initial rate of CH₃ production during pyrolysis indicated that for both iso-octane and n-heptane, reaction rates for the initial decomposition channels are well isolated, and overall values for these rates were obtained. The present concentration time-history data provide strong constraints on the reaction mechanisms of both iso-octane and n-heptane oxidation, and in conjunction with OH concentration time-histories and ignition delay times, recently measured in our laboratory, should provide a self-consistent set of kinetic targets for the validation and refinement of iso-octane and n-heptane reaction mechanisms.     

On the influence of hydrogen on the low-temperature reactivity of n-pentane, 1-pentene and 3-pentanone: an experimental and modeling study

Hydrogen can be blended with other surrogate fuels to avoid its hazard as a highly flammable and explosive gas. The effect of hydrogen addition on the ignition delay times of n-pentane, 3-pentanone, and 1-pentene was investigated by measuring the ignition delay times in a rapid compression machine. The experiments were performed at pressures of 10, 15, and 20 bar, equivalence ratios 0.5 and 1 and for temperatures ranging from 650 to 970 K. The molar ratios of hydrogen in the fuel mixtures were 0, 25 and 50%. The experimental data were simulated using recent models from literature, yielding good agreement. The overall observations conclude to a minor effect of hydrogen addition in the case of n-pentane and 3-pentanone, resulting in a decrease of the reactivity when the mole fraction of hydrogen increases. Hydrogen does however not impact the ignition delay times of 1-pentene significantly. Kinetic analysis is performed to shed light into the processes responsible for this phenomenon.     

Skeletal mechanism generation and analysis for n-heptane with CSP

We use a procedure based on the decomposition into fast and slow dynamical components offered by the Computational Singular Perturbation (CSP) method to generate automatically skeletal kinetic mechanisms for the simplification of the kinetics of n-heptane oxidation. The detailed mechanism of the n-heptane oxidation here considered has been proposed by Curran et al. and involves 561 species and 2538 reactions. After carrying out a critical assessment of important aspects of this procedure, we show that the comprehensive skeletal kinetic mechanisms so generated are able to reproduce the main features of n-heptane ignition at various initial pressures and temperatures and equivalence ratios. A by-product of the algorithm that generates the skeletal mechanisms is the identification of the network of important species and reactions at a given state of the kinetic system. The analysis of this network is carried out by resorting to a visual representation of the pathways at selected time instants of the ignition process. Visual inspection of the pathways enables the identification and comparison of the relevant kinetic processes as obtained at different ignition regimes. The graphs are generated by interfacing the model reduction procedure with the open-source package graphviz.     

Isothermal compressibility and sound velocity of binary liquid systems: Application of hard sphere models

Sound velocity and density were measured in six binary liquid mixtures namely,n-heptane+toluene (I);n-heptane+n-hexane (II); toluene+n-hexane (III); cyclohexane+n-heptane (IV); cyclohexane+n-hexane (V), andn-decane+n-hexane (VI) at 298.15 K. The experimental isothermal compressibility has been evaluated from measured values of density and sound velocity. The isothermal compressibility of these mixtures has been calculated theoretically using different models for the hard sphere equation of state and also using Flory’s statistical theory. The computed values of isothermal compressibility were also compared with the experimentally evaluated values. A satisfactory agreement has been observed.     

Ignition behavior of pure and blended methyl octanoate,n-nonane,and methylcyclohexane

Excited-state species profiles and ignition delay times were obtained under dilute conditions (99% Ar) using a heated shock tube for methyl octanoate (C₉H₁₈O₂), n-nonane (n-C₉H₂₀), and methylcyclohexane (MCH) over a broad range of temperature and equivalence ratio (? = 0.5, 1.0, 2.0) at pressures near 1 and 10 atm. Measurements were then extended to include two ternary blends of the fuels using 5% and 20% (vol.) of the methyl ester under stoichiometric conditions. Using three independently validated chemical kinetics mechanisms, a model was compiled to assess the influence of methyl ester concentration on ignition delay times of the ternary blends. Under near-atmospheric pressure, ignition delay times were of the following order for the pure fuels: methyl octanoate < n-nonane < methylcyclohexane. Experimental results indicate that the ignition behavior of the higher-order methyl ester approaches that of the higher-order linear alkane with increased pressure regardless of equivalence ratio. Methyl octanoate also displayed significantly lower pressure dependence relative to the linear alkane and the cycloalkane species. Both of these results are supported by model calculations. Blending of methyl octanoate with n-nonane and methylcyclohexane impacted ignition delay time results more strongly at 1.5 atm, yet had only a small effect near 10 atm for temperatures above 1400 K. The study provides the first shock-tube data for a ternary blend of a linear alkane, a cycloalkane, and a methyl ester. Ignition delay time measurements for the C₉:0 methyl ester were also measured for the first time.     

Experimental and kinetic modeling study of combustion of JP-8, its surrogates and components in laminar premixed flows

Experimental and kinetic modeling studies are carried out to characterize premixed combustion of jet fuels, their surrogates, and reference components in laminar nonuniform flows. In previous studies, it was established that the Aachen surrogate made up of 80 % n-decane and 20 % trimethylbenzene by weight, and surrogate C made up of 57 % n-dodecane, 21 % methylcyclohexane and 22 % o-xylene by weight, reproduce key aspects of combustion of jet fuels in laminar nonpremixed flows. Here, these surrogates and a jet fuel are tested in premixed, nonuniform flows. The counterflow configuration is employed, and critical conditions of extinction are measured. In addition, the reference components tested are n-heptane, n-decane, n-dodecane, methylcyclohexane, trimethylbenzene, and o-xylene. Measured critical conditions of extinction of the Aachen surrogate and surrogate C are compared with those for the jet fuel. In general the alkanes n-heptane, n-decane, and n-dodecane, and methylcyclohexane are found to be more reactive than the aromatics o-xylene and trimethylbenzene. Flame structure and critical conditions of extinction are predicted for the reference components and the surrogates using a semi-detailed kinetic model. The predicted values are compared with experimental data. Sensitivity analysis shows that the lower reactivity of the aromatic species arises from the formation of resonantly stabilized radicals. These radicals are found to have a scavenging effect. The present study on premixed flows together with previous studies on nonpremixed flows show that the Aachen surrogate and surrogate C reproduce many aspects of premixed and nonpremixed combustion of jet fuels.     

Detailed and simplified kinetic models of n-dodecane oxidation: The role of fuel cracking in aliphatic hydrocarbon combustion

A detailed kinetic model is proposed for the combustion of normal alkanes up to n-dodecane above 850 K. The model was validated against experimental data, including fuel pyrolysis in plug flow and jet-stirred reactors, laminar flame speeds, and ignition delay times behind reflected shock waves, with n-dodecane being the emphasis. Analysis of the computational results reveal that for a wide range of combustion conditions, the kinetics of fuel cracking to form smaller molecular fragments is fast and may be decoupled from the oxidation kinetics of the fragments. Subsequently, a simplified model containing a minimal set of 4 species and 20 reaction steps was developed to predict the fuel pyrolysis rate and product distribution. Combined with the base C₁-C₄ model, the simplified model predicts fuel pyrolysis rate and product distribution, laminar flame speeds, and ignition delays as close as the detailed reaction model.