Rate Of Production Analysis Research Articles

Pyrolysis of butane-2,3‑dione from low to high pressures: Implications for methyl-related growth chemistry

In order to investigate the pressure-dependent effects of carbon chain growth from methyl radical, pyrolysis experiments of butane-2,3‑dione (also known as diacetyl) were conducted both in a flow reactor over 780–1520 K at low and atmospheric pressures and in a jet-stirred reactor (JSR) over 650–1130 K at 10 bar. Identification and quantification of the intermediates were achieved by synchrotron vacuum ultraviolet photoionization mass spectrometry in a flow reactor and Fourier transform infrared spectrometry and gas chromatography in a JSR. A pyrolysis model of butane-2,3‑dione, incorporating the sub-mechanisms of butane-2,3‑dione, ketene, C1–C4 hydrocarbons and the formation of benzene, was developed from our recently reported C1 model in this work. It was validated against the present pyrolysis data of butane-2,3‑dione and the pyrolysis data of C2–C4 hydrocarbon fuels and ketene in the literature. Generally, the present model could reasonably predict all the experimental targets. Based on the rate of production analysis, the unimolecular decomposition reaction (CH3COCOCH3 (+ M) = 2CH3CO (+ M)) is the dominant pathway to consume the fuel at low pressure. However, at atmospheric and high pressures, both the unimolecular decomposition reaction and the H abstraction reaction of butane-2,3‑dione by methyl radical are important. Ketene, acetone and acetaldehyde were measured in this work and their formation is also pressure dependent. For the methyl-related growth chemistry, addition-elimination reactions play an important role at low pressure. Their contribution becomes less at atmospheric pressure and can be neglected at high pressure. In contrast, the combination reactions are responsible for methyl-related growth at high pressure. For the formation of benzene, the recombination of propargyl radical is the most important pathway at low pressure, while the H-assisted isomerization reaction of fulvene becomes dominant at atmospheric and high pressures.

Experimental study on laminar flame speeds and chemical kinetic model of 2,4,4-trimethyl-1-pentene

The laminar flame speeds for 2,4,4-trimethyl-1-pentene/air mixtures have been measured in a constant volume combustion bomb, at initial temperatures of 400 and 450 K, initial pressures of 0.1 and 0.3 MPa, and equivalence ratios from 0.6 to 1.5. Both the linear and nonlinear models are used for extrapolation of unstretched flame speed. It is observed that there is a small discrepancy in laminar flame speed using linear and nonlinear models at ϕ⩽1.1, while this discrepancy becomes larger at higher equivalence ratio. Moreover, a chemical kinetic model for 2,4,4-trimethyl-1-pentene including 50 species and 361 elementary reactions is developed. Full validations show that the present model can well predict both ignition delay times and laminar flame speeds, at a wider range of initial temperatures, initial pressures and equivalence ratios. Using the present model, the rate of production analysis is performed to investigate the main reaction pathways of 2,4,4-trimethyl-1-pentene combustion. The analysis indicates that the differences of reaction pathways at high and low temperatures, are mainly embodied in the three aspects of primary reactions of 2,4,4-trimethyl-1-pentene, reactions of TC4H9, and reactions of isobutenyl.

Skeletal and reduced chemical mechanism for hydrogen fluoride chemical laser

The chemical kinetics of supersonic hydrogen fluoride (HF) chemical lasers determines combustion characteristics and output power. However, the inherent complexity of chemical reactions and complex structure still challenge the numerical simulations involving a comprehensive chemical mechanism. Therefore, a high fidelity and low computational consuming model is important for design purpose. This paper presents a strategy to generate a reduced mechanism for HF chemical lasers. Based on a detailed HF chemical mechanism consisting of 16 species and 153 elementary reactions, a specific skeletal mechanism including 11 species and 58 elementary reactions is generated. Finally, we obtain a further reduction mechanism including 11 species and 39 elementary reactions by combining sensitivity analysis and rate of production analysis. The computational cost for simulation of supersonic HF chemical lasers with the reduced mechanism is less than that with the detailed model. The principal contribution of the work is to provide a low computational consuming model.

A comparative study on the sooting tendencies of various 1-alkene fuels in counterflow diffusion flames

Alkenes are important components in transportation fuels, and are known to have increased sooting tendencies compared to analogous saturated hydrocarbons with the same carbon number. This work aims to understand the sooting tendencies of various 1-alkenes through experiments and numerical simulations for counterflow diffusion flames. Soot and PAH formation tendencies of 1-alkene fuels, including ethylene (C2H4), propene (C3H6), 1-butene (1-C4H8), 1-pentene (1-C5H10), 1-hexene (1-C6H12) and 1-octene (1-C8H16), were experimentally studied using laser induced-incandescence (LII) and laser-induced fluorescence (LIF) techniques, respectively. From the LII results, 1-C4H8 was found to be the most sooting fuel, followed by C3H6 > 1-C5H10 > 1-C6H12 > 1-C8H16 > C2H4. The LIF data with a detection wavelength of 500 nm indicated the PAH formation tendencies followed the order of 1-C4H8 > 1-C5H10 ∼1-C6H12 > C3H6 > 1-C8H16 > C2H4, which were different from the order of sooting tendencies. Numerical simulations with a comprehensive chemical kinetic model including PAH growth chemistry for the tested 1-alkene fuels were conducted to elucidate the aromatic formation pathways and rationalize the experimentally observed trends. The numerical results highlighted the importance of intermediate species with odd carbon numbers in aromatic species formation, such as propargyl, allyl, cyclopentadienyl and indenyl radicals. Their concentration differences, which could be traced back to the parent fuel molecules through rate of production analysis, rationalize the experimentally observed differences in soot and PAH formation tendencies.

Experimental and kinetic modeling investigation on pyrolysis and combustion of n-butane and i-butane at various pressures

Butane is the smallest alkane with normal and branched isomers. To obtain insight into the effects of fuel structure and pressure on its intermediate-to-high temperature combustion chemistry, flow reactor pyrolysis and laminar burning velocities of the butane isomers were investigated at various pressures. In the pyrolysis experiments, species profiles were measured as function of the heating temperature at 0.04, 0.2 and 1 atm using synchrotron vacuum ultraviolet photoionization mass spectrometry. Laminar burning velocities of both n-butane/air and i-butane/air mixtures were measured at 298 K and 1–10 atm using spherically expanding flames. It was observed that both the pyrolysis and combustion behaviors of the butane isomers were influenced by the fuel structures. A detailed kinetic model of butane isomers was developed and validated against the new experimental data. Both rate of production analysis and sensitivity analysis were performed to give insight into the chemistry of butane pyrolysis and combustion. In the flow reactor pyrolysis, the weaker primary-tertiary CC bond than the primary-secondary and secondary-secondary CC bonds leads to lower initial decomposition temperatures of i-butane than n-butane. Under both pyrolysis and combustion conditions, the reaction pathways towards C2 and C3 species pool are emphasized for the decomposition of n-butane and i-butane, respectively. The more abundant production of C3 precursors explains the higher concentrations of benzene in the i-butane pyrolysis, while the higher laminar burning velocities of n-butane/air mixtures at all investigated pressures are mainly attributed to the easy production of H atom from n-butane decomposition and the dominance of the reactive C2 chemistry. Moreover, the i-butane/air flames exhibit stronger pressure dependence than the n-butane/air flames. The model was further validated against a wide range of experimental data in the literature, including ignition delay times and species profiles in flow reactor pyrolysis and oxidation, shock tube pyrolysis and oxidation, jet-stirred reactor oxidation and laminar premixed flames.

A Detailed Study of the Effects of Biodiesel Addition and Exhaust Gas Recirculation on Diesel Engine PCCI Combustion, Performance and Emission Characteristics by KIVA–CHEMKIN Coupling

In this study, a numerical study is performed by KIVA–CHEMKIN code to investigate the effects of biodiesel addition and exhaust gas recirculation (EGR) on diesel engine premixed charge compression ignition (PCCI) combustion, performance, and emission characteristics. The studies are performed for neat diesel fuel and mixture of 10–40% biodiesel addition at 67%, 50%, and 40% EGR. For this purpose, a multichemistry surrogate mechanism using methyl decanoate (MD) and methyl-9-decenoate (MD9D) is used. The main innovation of this work is analyzing the chemical, thermodynamic, and dilution effects of biodiesel addition as well as different EGR ratios on PCCI combustion behavior. The results show that the main effect of EGR on PCCI combustion of biodiesel blend is related to the high temperature heat release (HTHR), and its effect on low temperature heat release (LTHR) is low. With increasing biodiesel addition, the role of the chemical effect is increased compared to the thermodynamic and dilution effects. Rate of production analysis (ROPA) indicate that for the different biodiesel ratios, the effect of reaction nC7H16 + HO2 = C7H15-2 + H2O2 is more effective on the start of combustion (SOC) compared to the other reactions. For a defined biodiesel addition, with decreasing EGR, total (unburned) hydrocarbon (THC) and CO are decreased, while NOx and indicated specific fuel consumption (ISFC) are increased.

Toward the Accurate Prediction of Liquid Phase Oxidation of Aromatics: A Detailed Kinetic Mechanism for Toluene Autoxidation

Toluene is an important compound in the chemical industry as well as an often chosen simple surrogate compound for aromatic components in transport fuels. As a result, an improved understanding of the liquid phase oxidation of toluene is of interest to both the chemical industry and the transportation sector. In this work, a detailed autoxidation mechanism for the liquid phase oxidation of toluene is developed using an automated mechanism generation tool. The resultant mechanism is significantly improved using quantum chemistry calculations to update the thermodynamic parameters of key species in solution. Comparisons are made between the predicted and experimentally measured induction period and the obtained mechanism. The agreement between both is found to be within 1 order of magnitude. Rate of production analysis and sensitivity analysis are carried out to explain and understand the reactions paths present in the mechanism. The behavior of the mechanism is commented upon qualitatively; however, no qua...

Effects of oxygen-enrichment and fuel unsaturation on soot and NOx emissions in ethylene, propane, and propene flames

We have performed a computational study on the effects of oxygen enrichment11In this paper, the term oxygen enrichment (or oxygenation) is used to indicate simultaneous O2 enhancement of the oxidizer stream and N2 dilution of the fuel stream. and fuel unsaturation on the flame structure, PAHs, soot, and NOx emissions. Counterflow flames burning ethylene, propane, and propene are simulated with CHEMKIN-Pro, using a validated mechanism with 197 species and around 5000 reactions. The stoichiometric mixture fraction (ζst) is varied by simultaneously using O2-enriched airstream and N2-diluted fuel stream such that the adiabatic flame temperature is nearly constant. Dominant reaction paths are analyzed to examine the relative roles of hydrodynamics and changes in flame structure on PAHs and soot emissions. As ζst is increased, results indicate a significant reduction in acetylene and PAHs formation, and with additional soot oxidation in the post flame region, it leads to a nearly non-sooting flame. The drastic reduction in PAHs and soot formation can be attributed to both the hydrodynamic and the flame structure effects. At moderate oxygenation levels, changes in flame structure seems to play a more prominent role, while at higher oxygenation levels, the hydrodynamic effect seems to be more important. With the increase in ζst, the O, OH, and H radical pool is enhanced, and, consequently, the intermediate species (propargyl, allene, and propyne) are reduced to smaller hydrocarbons, decreasing the formation of PAHs and soot. With further increase in ζst, the flame location shifts from oxidizer to fuel side, and, consequently, PAH species and soot get oxidized in the oxygen rich region, leading to nearly soot free flames. However, as ζst is increased, NO emissions increase monotonically. At low ζst values, the prompt route contributes more to NO formation, while at high ζst values, the thermal route contributes more. The rate of production analysis indicates that the presence of double bond promotes reactions which produce higher amounts of allyl and propargyl species, and thus higher amounts of soot precursors; benzene and pyrene. Consequently, propene and ethylene flames produce significantly higher amount of soot compared to propane flames.

A comprehensive experimental and kinetic modeling study of n-propylbenzene combustion

This work presents a comprehensive experimental and kinetic modeling study on the combustion of n-propylbenzene. Flow reactor pyrolysis of n-propylbenzene at 0.04, 0.2 and 1 atm and laminar premixed flames of n-propylbenzene at 0.04 atm with equivalence ratios of 0.75 and 1.00 were investigated with synchrotron vacuum ultraviolet photoionization mass spectrometry. Jet stirred reactor (JSR) oxidation of n-propylbenzene at 10 atm with equivalence ratios of 0.5, 1.0, 1.5 and 2.0 was investigated with gas chromatography. A detailed kinetic model for n-propylbenzene combustion with 340 species and 2069 reactions was developed and validated against the data measured in this work. Model analyses such as rate of production analysis and sensitivity analysis were also performed to reveal the key pathways in the consumption of fuel and formation of polycyclic aromatic hydrocarbons (PAHs). The analysis results demonstrate that the benzylic CC bond dissociation reaction is crucial for the decomposition of n-propylbenzene in the pyrolysis and rich flame. Low temperature oxidation reactions play important roles in the high pressure JSR oxidation of n-propylbenzene. In addition, the formation pathways of PAHs are strongly related to the fuel structure, especially for the formation of bicyclic PAHs such as indene and naphthalene. Furthermore, the present model was also validated against previous experimental data of n-propylbenzene combustion under a wide range of conditions, including ignition delay times, laminar flame speeds, extinction strain rates, speciation profiles in atmospheric pressure JSR oxidation, flow reactor oxidation and high pressure shock tube pyrolysis and oxidation.

Investigation of a Simplified Mechanism Model for Prediction of Gallium Nitride Thin Film Growth through Numerical Analysis

A numerical procedure was performed to simplify the complicated mechanism of an epitaxial thin-film growth process. In this study, three numerical mechanism models are presented for verifying the growth rate of the gallium nitride (GaN) mechanism. The mechanism models were developed through rate of production analysis. All of the results can be compared in one schematic diagram, and the differences among these three mechanisms are pronounced at high temperatures. The simplified reaction mechanisms were then used as input for a two-dimensional computational fluid dynamics code FLUENT, enabling the accurate prediction of growth rates. Validation studies are presented for two types of laboratory-scale reactors (vertical and horizontal). A computational study including thermal and flow field was also performed to investigate the fluid dynamic in those reactors. For each study, the predictions agree acceptably well with the experimental data, indicating the reasonable accuracy of the reaction mechanisms.

Experimental and Kinetic Modeling Study of CH3OCH3 Ignition Sensitized by NO2

We investigate the role of NO2 in dimethyl ether (DME) ignition with a combustion shock tube. Ignition delay times are measured at 987–1517 K and 4 and 10 atm. Different equivalence ratios (0.5, 1.0, and 2.0) and NO2 and DME concentrations are explored. NO2 promotes DME ignition, and the promoting effect becomes more pronounced at high NO2 concentrations or low temperatures. NO2 addition also augments the influence of the equivalence ratio on ignition delay times. Four detailed reaction mechanisms from the literature are examined against the measurements, and an updated kinetic model is proposed and validated in comparison to experiments. On the basis of the updated model, sensitivity analysis, reaction flux analysis, and rate of production analysis are conducted to provide details on the kinetic effect of NO2 on DME ignition.

A new predictive multi-zone model for HCCI engine combustion

This work introduces a new predictive multi-zone model for the description of combustion in Homogeneous Charge Compression Ignition (HCCI) engines. The model exploits the existing OpenSMOKE++ computational suite to handle detailed kinetic mechanisms, providing reliable predictions of the in-cylinder auto-ignition processes. All the elements with a significant impact on the combustion performances and emissions, like turbulence, heat and mass exchanges, crevices, residual burned gases, thermal and feed stratification are taken into account. Compared to other computational approaches, this model improves the description of mixture stratification phenomena by coupling a wall heat transfer model derived from CFD application with a proper turbulence model. Furthermore, the calibration of this multi-zone model requires only three parameters, which can be derived from a non-reactive CFD simulation: these adaptive variables depend only on the engine geometry and remain fixed across a wide range of operating conditions, allowing the prediction of auto-ignition, pressure traces and pollutants. This computational framework enables the use of detail kinetic mechanisms, as well as Rate of Production Analysis (RoPA) and Sensitivity Analysis (SA) to investigate the complex chemistry involved in the auto-ignition and the pollutants formation processes. In the final sections of the paper, these capabilities are demonstrated through the comparison with experimental data.

Experimental and kinetic modeling study of laminar premixed decalin flames

Laminar premixed flames of decalin with equivalence ratios of 0.75, 1.0 and 1.8 were studied using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Dozens of flame species were identified and their mole fraction profiles were evaluated, including a series of free radicals. A detailed kinetic model of decalin combustion consisting of 538 species and 3218 reactions was developed and validated on the new flame data. The rate of production analysis at different equivalence ratios were performed to help understand the kinetics in the decompostion of decalin and the formation of some key intermediates. The H-atom abstraction reactions play an overwhelming role in the primary decomposition of decalin at flame conditions. Monocyclic aromatic hydrocarbons (MAHs) are mainly produced from the decomposition of decalin, while polycyclic aromatic hydrocarbons (PAHs) originate from mass growth process of PAH precursors. In addition, some oxygenated intermediates have important contributions to the formation of key MAHs and PAHs such as benzene (A1) and indene (C9H8). The direct production of PAH precursors in fuel decomposition process explains the higher sooting tendency of decalin than n-alkanes and benzene. Furthermore, the model was used to simulate literature data of decalin combustion, such as species profiles in jet stirred reactor oxidation of decalin and ignition delay times of decalin.

Experimental and kinetic modeling investigation on decalin pyrolysis at low to atmospheric pressures

The pyrolysis of decalin was studied in a flow reactor using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) at the pressures of 4, 20, and 101kPa and the temperatures from 920 to 1500K. Dozens of pyrolysis species were identified and their mole fraction profiles were measured as a function of temperature, particularly several free radicals and aromatic species. Besides, a detailed kinetic model consisting of 484 species and 1774 reactions was proposed and used to simulate the present experimental data. The rate of production analysis and sensitivity analysis was performed in order to provide deep insight into the pyrolysis kinetics of decalin. The decomposition of decalin is initiated by the C–C bond dissociation reactions of both decalin and its C10H18 isomers, while the H-atom abstraction reactions consume most of decalin. Monocyclic aromatic hydrocarbons (MAHs) are mainly produced in the fuel decomposition process instead of the mass growth process from small molecules, indicating that the two fused six-membered ring structure offers a solid infrastructure to form MAHs. Polycyclic aromatic hydrocarbons (PAHs) are mainly produced in the mass growth process from PAH precursors such as benzyl radical (A1CH2), phenyl radical (A1-), and 1,3-cyclopentadienyl radical (CYC5H5). The relatively high degree of saturation of decalin facilitates ring-opening pathways in its decomposition. This enhances the formation of MAHs but limits the formation of PAHs, leading to the lower sooting tendency of decalin than tetralin. Furthermore, the model was also validated on the shock tube pyrolysis data of decalin in the literature.

Kinetic modeling of polycyclic aromatic hydrocarbons formation process for gasoline surrogate fuels

It is very necessary to develop a comprehensive gasoline surrogate fuel chemical kinetic model that could accurately predict soot emissions and polycyclic aromatic hydrocarbons (PAHs) formation in internal combustion engines. Based on the consideration, this paper presents a toluene reference fuel (TRF) chemical mechanism to predict the PAHs formation process. This mechanism has been validated for ignition delays over a range of initial conditions covering the pressures from 15 to 60bar, equivalence ratios from 0.5 to 2.0 and temperatures from 750 to 1280K, especially for gasoline/air and two TRFs/air mixtures under engines conditions. Laminar flame speeds were also validated at low and high pressures. Furthermore, in order to guarantee the prediction accuracy of PAHs, premixed and opposed flow flames were simulated to validate the formation of PAHs and good agreements were obtained. Sensitivity analysis was performed to analyze the contribution of reactions to ignition delays and laminar flame speeds. Rate of production analysis was also carried out to identify the formation and consumption reaction pathways of A1 under different temperatures. The results indicated that the TRF–PAHs chemical mechanism could meet the demand of the PAHs simulation in engines. The proposed mechanism, which includes 219 species and 1229 reactions, is available as supporting Information for this article.

OH-LIF measurement of H2/O2/N2 flames in a micro flow reactor with a controlled temperature profile

This paper presents combustion and ignition characteristic of H2/O2/N2 flames in a micro flow reactor with a controlled temperature profile. OH-LIF measurement was conducted to capture flame images. Flame responses were investigated for variable inlet flow velocity, U, and equivalence ratio, ϕ. Three kinds of flame responses were experimentally observed for the inlet flow velocities: stable flat flames (normal flames) in the high inlet flow velocity regime; unstable flames called Flames with Repetitive Extinction and Ignition (FREI) in the intermediate flow velocity regime; and stable weak flames in the low flow velocity regime, at ϕ = 0.6, 1.0 and 1.2. On the other hand, weak flame was not observed at ϕ = 3.0 by OH-LIF measurement. Computational OH mole fractions showed lower level at the rich conditions than those at stoichiometric and lean conditions. To examine this response of OH signal to equivalence ratio, rate of production analysis was conducted and four kinds of major contributed reaction for OH production: R3(O + H2 <=> H + OH); R38(H + O2 <=> O + OH); R46(H + HO2 <=> 2OH); and R86(2OH <=> O + H2O), were found. Three reactions among them, R3, R38 and R46, did not showed significant difference in rate of OH production for different equivalence ratios. On the other hand, rate of OH production from R86 at ϕ = 3.0 was extremely lower than those at ϕ = 0.6 and 1.0. Therefore, R86 was considered to be a key reaction for the reduction of the OH production at ϕ = 3.0.

Investigation on the pyrolysis and oxidation of toluene over a wide range conditions. I. Flow reactor pyrolysis and jet stirred reactor oxidation

The pyrolysis of toluene was studied in a flow reactor at pressures from 5 to 760Torr and temperatures from 1100 to 1730K using synchrotron vacuum ultraviolet photoionization mass spectrometry. The pyrolysis species and intermediates, including some radicals, isomers and large PAHs, were identified and their mole fraction profiles were evaluated as the function of heating temperature. The oxidation of toluene was investigated in a jet stirred reactor (JSR) at the pressure of 10atm, residence time of 0.6s, equivalence ratios of 0.5, 1.0 and 1.5, and temperatures from 950 to 1200K using gas chromatography combined with flame ionization detector, thermal conductivity detector and mass spectrometry. The concentration profiles of oxidation products as the function of heating temperature were measured. Based on recent theoretical progresses, a detailed kinetic model of toluene combustion with 272 species and 1698 reactions was developed to reproduce the decomposition of toluene and growth of aromatics in both the flow reactor pyrolysis and JSR oxidation. The rate of production analysis and the sensitivity analysis reveal that benzyl and fulvenallenyl radicals play crucial roles in the decomposition of toluene and formation of polycyclic aromatic hydrocarbons (PAHs).

Characteristics of n-butane weak flames at elevated pressures in a micro flow reactor with a controlled temperature profile

The very first successful experiments at elevated pressures up to 1.2MPa by an “in-pressure-chamber”-type micro flow reactor with a controlled temperature profile are demonstrated. n-Butane was applied to the micro flow reactor and the ignition characteristics at pressures of 0.1–1.2MPa were investigated by observing weak flames. Among three kinds of separated weak flames which can be observed by the present reactor, the blue flame was only observed at pressures higher than 0.2MPa and the cool flame was only observed at pressures higher than 0.3MPa. This interprets the multi-stage oxidation for n-butane was confirmed experimentally and computationally. The positions of the blue and cool flames shifted towards the lower temperature side along with the increase of pressure in the experiment. Computation results reproduced the experimental tendency of the blue and cool flames. The wall temperature value at the cool flame position in the experiment agreed with that in the computation at all pressures studied, and that at 1.0MPa agreed with the compressed temperature at which the cool flame was observed in the rapid compression machine at a compression pressure of 10bar. The computational weak flame structure at 0.1MPa was compared with that of 1.0MPa. High-temperature oxidation is important at 0.1MPa while low temperature oxidation is important at high pressures. At 1.0MPa, most of the fuel is consumed at the cool flame. Separated cool flames were found at 1.2MPa and four-stage oxidation was produced in the computation. Rate of production analysis indicated that the first cool flame was formed by fuel oxidation through low-temperature oxidation while the second one was formed by reaction of peroxyl radicals with H2O2.

Experimental and kinetic modeling investigation on laminar premixed benzene flames with various equivalence ratios

Chemical structures of six laminar premixed benzene/oxygen/argon flames with equivalence ratios from 0.75 to 2.0 were investigated at 30Torr. Dozens of flame species, especially radicals and large aromatics, were qualitatively identified and quantitatively measured using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). A kinetic model was developed from our previous models of aromatic fuels to simulate the decomposition of benzene and formation of large aromatics, and was validated against the measured mole fraction profiles of flame species. Based on the rate of production analysis in the leanest and richest flames, the decomposition processes of benzene and the fate of C6 and smaller products were discussed in detail. Benzene, phenyl radical and cyclopentadienyl radical are concluded as key precursors of large aromatics, and the low formation of PAHs in rich benzene flames compared with rich alkylbenzene flames mainly derives from the low production of benzyl radical, which is consistent with the observed trends of the sooting tendencies of benzene and alkylbenzenes in previous studies.

Experimental and kinetic modeling study of pyrolysis and oxidation of n-decane

The pyrolysis of n-decane was investigated in a flow reactor at 5, 30, 150 and 760Torr, and the oxidation of n-decane at equivalence ratios of 0.7, 1.0 and 1.8 was studied in laminar premixed flames at 30Torr. In both experiments, synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was used to identify combustion species and measure their mole fraction profiles. A new detailed kinetic model of n-decane with 234 species and 1452 reactions was developed for applications in intermediate and high temperature regions, and was validated against the experimental results in the present work. The model was also validated against previous experimental data on n-decane combustion, including species profiles in pyrolysis and oxidation in high pressure shock tube and atmospheric pressure flow reactor, jet stirred reactor oxidation, atmospheric pressure laminar premixed flame, counterflow diffusion flame and global combustion parameters such as laminar flame speeds and ignition delay times. In general, the performance of the present model in reproducing these experimental data is reasonably good. Sensitivity analysis and rate of production analysis were conducted to understand the decomposition processes of n-decane.