Detailed Chemical Kinetic Model Research Articles

An improved detailed chemical kinetic model for C3-C4 linear and iso-alcohols and their blends with gasoline at engine-relevant conditions

Propanol and butanol isomers have received significant research attention as promising fuel additives or neat biofuels. Robust chemical kinetic models are needed that can provide accurate and efficient predictions of combustion performance across a wide range of engine relevant conditions. This study seeks to improve the understanding of ignition and combustion behavior of pure C3-C4 linear and iso-alcohols, and their blends with gasoline at engine-relevant conditions. In this work, a kinetic model with improved thermochemistry and reaction kinetics was developed based on recent theoretical calculations of H-atom abstraction and peroxy radical reaction rates. Kinetic model validations are reported, and the current model reproduces the ignition delay times of the C3 and C4 alcohols well. Variations in reactivity over a wide range of temperatures and other operating conditions are also well predicted by the current model. Recent ignition delay time measurements from a rapid compression machine of neat iso-propanol and iso-butanol [Cheng et al., Proc. Combust Inst. (2020)] and blends with a research grade gasoline [Goldsborough et al., Proc. Combust Inst. (2020)] at elevated pressure (20–40 bar) and intermediate temperatures (780–950 K) were used to demonstrate the accuracy of the current kinetic model at conditions relevant to boosted spark-ignition engines. The effects of alcohol blending with gasoline on the autoignition behavior are discussed. The current model captures the suppression of reactivity in the low-temperature and negative-temperature-coefficient (NTC) region when either isopropanol and isobutanol are added to a research grade gasoline. Sensitivity and reaction flux analysis were performed to provide insights into the relevant fuel chemistry of the C3-C4 alcohols.

Development of a Detailed Kinetic Model for Hydrogen Oxidation in Supercritical H2O/CO2 Mixtures

The application of hydrogen as a fuel or auxiliary fuel has extended beyond gas-phase conditions. This paper reports the development of a detailed chemical kinetic model for hydrogen oxidation in s...

Oxidation of methylamine

AbstractA detailed chemical kinetic model for oxidation of methylamine has been developed, based on theoretical work and a critical evaluation of data from the literature. The rate coefficients for the reactions of CHNH + O CHNH / CHNH + HO, CHNH + H CH + NH, CHNH CHNH, and CHNH + O CHNH + HO were calculated from ab initio theory. The mechanism was validated against experimental results from batch reactors, flow reactors, shock tubes, and premixed flames. The model predicts satisfactorily explosion limits for CHNH and its oxidation in a flow reactor. However, oxidation in the presence of nitric oxide, which strongly promotes reaction at lower temperatures, is only described qualitatively. Furthermore, calculated flame speeds are higher than reported experimental values; the model does not capture the inhibiting effect of the NH group in CHNH compared to CH. More work is desirable to confirm the products of the CHNH + NO reaction and to look into possible pathways to NH in methylamine oxidation.

Review on Mechanisms and Kinetics for Supercritical Water Oxidation Processes

Supercritical water oxidation (SCWO) is a promising wastewater treatment technology owing to its various advantages such as rapid reactions and non-polluting products. However, problems like corrosion and salt decomposition set obstacles to its commercialization. To address these problems, researchers have been developing the optimal reactor design and strengthening measures based on sufficient understandings of the degradation kinetics. The essence of the SCWO process and the roles of oxygen and hydrogen peroxide are summarized in this work. Then, the research status and progress of empirical models, semi-empirical models, and detailed chemical kinetic models (DCKMs) are systematically reviewed. Additionally, this paper is the first to summarize the research progress of quantum chemistry and molecular dynamics simulation. The challenge and further development of kinetics models for the optimization of reactors and the directional transformation of pollutants are pointed out.

Contributions of Experimental Data Obtained in Concentrated Mixtures to Kinetic Studies: Application to Monomethylhydrazine Pyrolysis.

Experimental, numerical, and theoretical studies are performed to understand the explosive thermal decomposition of monomethylhydrazine/argon mixtures. Ignition delays of concentrated MMH/Ar mixtures (20-30%) have been measured behind a reflected shock wave around 1000 K and 1 atm. Although several detailed chemical kinetic models have predictive abilities for diluted and highly diluted mixtures, none of them showed predictive for concentrated mixtures. A new kinetic model is proposed, in which numerous rate constants and thermochemical data are reassessed based on theoretical calculations, with the purpose to determine whether, or to what extent, trends derived from diluted or highly diluted MMH/Ar mixtures can explain observations in concentrated MMH mixtures. The present kinetic model is found to predict speciation experimental profiles in diluted MMH/Ar mixtures and is a significant improvement in predicting the induction delays of concentrated MMH/Ar mixtures.

A methodology to formulate multicomponent fuel surrogates to model flame propagation and ignition delay

Nowadays, the leading driver for the development of internal combustion engines is the search for increased fuel efficiency and reduced emissions. To develop and optimize new combustion systems, a high degree of accuracy is needed in 3D-CFD simulations. In particular, detailed chemical kinetics models and fuel surrogates able to represent the main physical and chemical properties of the real commercial fuels are needed. A series of fuel surrogate formulation methodologies were presented in the recent past with the aim of matching fuel properties and combustion-related characteristics using a set of well-known compounds. While most of the gasoline-targeted available studies mainly focused on the possibility to simultaneously match the gross fuel properties, the evaporating characteristics and the auto-ignition behaviour of the fuel, none of them explicitly targeted the flame propagation characteristics. In this work, a novel methodology is introduced to formulate gasoline fuel surrogates able to match the main chemical and physical properties, the auto-ignition and the flame propagation characteristics of a commercial gasoline. Due to the increasing presence of oxygenated fuels in the market share, an average gasoline fuel named ULG95, representative of a European oxygenated gasoline with Research Octane Number RON = 95, is targeted to validate the presented methodology. Three fuel surrogates of increasing complexity are formulated and validated against laminar flame speed, shock-tube and rapid compression machine experiments available in literature for oxygenated gasolines. The results suggest that a unique gasoline fuel surrogate can be used, together with validated chemical kinetics mechanisms, to model auto-ignition and flame propagation characteristics.

Ozone-Enhanced Flame Propagation of Methane/Ethylene/Air Mixtures at Subatmospheric Pressures

The combustion enhancement by ozone has been studied for single-component fuels in many different settings; however, the impact of ozone addition on a multicomponent fuel has been experimentally underexplored. This paper investigates the ozone-assisted flame propagation of a mixture of alkenes and alkanes in a low-pressure Hencken burner over a range of equivalence ratios, ozone concentrations, and pressures. One-dimensional numerical simulations of the flame speed using a detailed chemical kinetic model are also conducted for comparison to the experimental measurements. Both the experimental measurements and numerical simulations indicate that higher ozone concentrations result in increased flame speeds of methane/ethylene/air mixtures and that the relative flame speed enhancement by ozone is larger for off-stoichiometric conditions. Although quantitative agreement is achieved for the cases without ozone addition, the ozone-assisted flame speeds are generally overpredicted by the kinetic model. Finally, a computational analysis of the detailed flame structure is performed, and the coupling between fuel chemistry and the ozone H-abstraction reaction, , is found to be crucial in determining the relative degree of flame speed enhancement of methane/ethylene/air mixtures by ozone.

Autoignition of CRC diesel surrogates at low temperature combustion conditions: Rapid compression machine experiments and modeling

As federal programs require increasingly stringent engine emissions and fuel economy standards, these ambitions can only be met if next-generation combustion technology is developed focusing on high-efficiency and low-emissions engines. Recent research has indicated the need to operate engines at higher compression ratios and with low temperature combustion (LTC) to achieve the needed gains in engine efficiency and reductions in emissions. Because there is a lack of understanding of the chemistry of diesel fuel components and their mixtures at these LTC conditions, this limits the ability to develop predictive chemical kinetic models that can be used to optimize engine combustion. The current study aims to fill in gaps in fundamental combustion data on surrogate fuel mixtures relevant to diesel fuels. Specifically, four multicomponent diesel surrogates formulated by the Coordinating Research Council (CRC) to emulate an ultra-low-sulfur research-grade #2 certification diesel fuel (CFA), namely V0a (4 components), V0b (5 components), V1 (8 components), and V2 (9 components), have been investigated in a rapid compression machine (RCM) through determination of total and first-stage ignition delay times. Autoignition characteristics of lean to rich fuel/O2/N2 mixtures, for the four CRC surrogates and CFA, have been measured using an RCM at LTC relevant pressures and temperatures, in the ranges of 10–20 bar and 650–1000 K, respectively. The equivalence ratios have been varied by independently changing the oxygen mole fraction and the fuel mole fraction in the test mixtures, thereby illustrating the individual effects of oxygen concentration and fuel loading on diesel autoignition. Autoignition results of these four CRC surrogates are compared among them and with those of CFA. Some degree of agreement in autoignition response between each CRC surrogate and CFA is observed, while discrepancies are also identified and discussed. In addition, a detailed chemical kinetic model for diesel surrogates has been developed and validated against these newly-acquired RCM data. This model shows reasonable agreement with the overall ignition delay time results of the current RCM experiments. Chemical kinetic analyses of the developed model were further conducted to help identify the reactions controlling the autoignition processes and the consumption of fuel components in CRC surrogates.

A detailed chemical kinetic model for the supercritical water oxidation of methylamine: The importance of imine formation

AbstractA detailed chemical kinetic model has been developed for supercritical water oxidation (SCWO) of methylamine, CH3NH2, providing insight into the intermediates and final products formed in this process as well as the dominant reaction pathways. The model was adapted from previous mechanisms, with a revision of the peroxyl radical chemistry to include imine formation, which has recently been identified as the dominant gas‐phase pathway in amine oxidation. The developed model can reproduce previous experimental data on methylamine consumption and major product formation to reasonable accuracy, although with deficiencies in describing the induction time. Our simulations indicate that oxidation of the •CH2NH2 radical to methanimine, CH2NH, is the major channel in methylamine SCWO, with subsequent hydrolysis of CH2NH providing the experimentally observed reaction products ammonia and formaldehyde. Integral‐averaged reaction rates were used to identify major reaction pathways, and a first‐order sensitivity analysis indicated that the concentration of CH3NH2 is most sensitive to OH radical kinetics. Overall, this work clarifies the importance of imine chemistry in the oxidation of nitrogen‐containing compounds and indicates that they are necessary to model these compounds in SCWO processes.

OH-Initiated Reactions of para-Coumaryl Alcohol Relevant to the Lignin Pyrolysis. Part III. Kinetics of H-Abstraction by H, OH, and CH3 Radicals

Lignin is the most complex component of biomass, and development of a detailed chemical kinetic model for biomass pyrolysis mainly relies on the understanding of the lignin decomposition kinetics. para-Coumaryl alcohol (p-CMA, HOPh-CH═CH-CH2OH), the focus of our analysis, is the simplest of the lignin monomers (monolignols) containing a typical side-chain double bond and both alkyl- and phenolic-type OH-groups. In parts I and II of our work (Asatryan, R. J. Phys. Chem. A 2019, 123, 2570-2585; Hudzik, J. M. J. Phys. Chem. A 2020, current issue), we created a detailed potential energy surface (PES) and performed a kinetic analysis of chemically activated, unimolecular, and bimolecular reactions pathways for p-CMA + OH. Reaction pathways analyzed include dissociation, intramolecular abstraction, group transfer, and elimination processes. The α- and β-carbon addition reactions generate 1,3- (RA1) and 1,2-diol (RB1) adduct radicals, respectively. Well depths are approximately 29 and 41 kcal/mol below the p-CMA + OH entrance level. Kinetic analysis aides in determining the major pathways for our conventional and fractional pyrolysis experiments. The current paper focuses on the H-abstraction reactions via H, OH, and CH3 light ("pool") radicals from p-CMA. The thermochemical properties of all stable, radical, and transition-state species were determined using the ωB97XD density functional theory (DFT) and higher-level CBS-QB3 composite methods. Barrier heights from the prereaction complexes, for OH-radical abstractions, to the transition states for the propanoid side chain are compared to the model H-abstraction reactions of allyl alcohol (AA) with OH and p-CMA with H and CH3 radicals. The lowest-energy, most stable, p-CMA radical formed is at the C9 allylic position (p-CMA-C9j) with exothermicity of 26.63, 41.32, and 27.34 kcal/mol for H, OH, and CH3, respectively. For OH-radical abstraction at this position, our findings are consistent with corresponding data on AA + OH at 37.44 kcal/mol and similar to that of RB1. A similar stable radical with an exothermicity of 34.95 kcal/mol occurs for the phenol hydroxyl group, generating the p-CMA-O4j radical. H-abstraction pathways are considered in relation to other major pathways previously considered for p-CMA + OH reactions including H-atom shifts, dehydration, and β-scission reactions. Derived rate coefficients for substituted phenols can be utilized in detailed kinetic models for lignin/biomass pyrolysis.

OH-Initiated Reactions of para-Coumaryl Alcohol Relevant to the Lignin Pyrolysis. Part II. Kinetic Analysis.

Monolignols are precursor units and primary products of lignin pyrolysis. The currently available global (lumped) and semidetailed kinetic models, however, are lacking the comprehensive decomposition kinetics of these key intermediates in order to advance toward the fundamentally based detailed chemical-kinetic models of biomass pyrolysis. para-Coumaryl alcohol (HOPh-CH═CH-CH2OH, p-CMA) is the simplest of the three basic monolignols containing a typical side-chain double bond and both alkyl and phenolic type OH groups. The two other monomers additionally contain one and two methoxy groups, respectively, attached to the benzene ring. Previously, we developed a detailed fundamentally based mechanism for unimolecular decomposition of p-CMA (as well as its truncated allyl and cinnamyl alcohol models) and explored its reactivity toward H radicals generated during pyrolysis. The reactions of p-CMA with pyrolytic OH radicals is another set of key reactions particularly important for understanding the formation mechanisms of a wide variety of oxygenates in oxygen-deficit (anaerobic) conditions and the role of the lignin side groups in pyrolysis pathways. In Part I of the current study (J. Phys. Chem. A, 2019, 123, 2570-2585), we reported a detailed potential energy (enthalpy) surface analysis of the reaction OH + p-CMA with suggestions for a variety of chemically activated, unimolecular, and bimolecular reaction pathways. In Part II of our work, we provide a detailed kinetic analysis of the major reaction channels to evaluate their significance and possible impacts on product distributions. Temperature- and pressure-dependent rate constants are calculated using the quantum Rice-Ramsperger-Kassel method and the master equation analysis for falloff and stabilization. Enthalpies of formation, entropies, and heat capacities are calculated using density functional theory and higher-level composite methods for stable molecules, radicals, and transition-state species. A significant difference between well depths for the chemically activated adduct radicals, [p-CMA-OH]*, is found for the α- and β-carbon addition reactions to generate the 1,3- and 1,2-diol radicals, respectively. This is due to the synergistic effect from conjugation of the proximal radical center with the aromatic ring and the strong H-bonding interaction between vicinal OH groups in the β-adduct (1,2-diol radical). Both adducts undergo isomerization and low-energy transformations, however, with different kinetic efficiencies because of the difference in stabilization energies. Reaction pathways include dissociation, intramolecular abstraction, atom and group transfers, and elimination. Of particular interest is a roaming-like low-energy dehydration reaction to form O-centered intermediate radicals. The kinetic analysis demonstrated the feasible formation of various products detected in pyrolysis experiments, suggesting that the gas-phase reactions of OH radicals can be a key process to form major products and complex oxygenates during lignin pyrolysis. Our preliminary experiments involving pyrolysis of the vaporized monomers support this basic statement. A novel mechanism for the formation of benzofuran, identified in experimentation, is also provided based on the potential conversions of hydroxyphenylacetaldehyde and corresponding isomers, which are kinetically favored products.

Autoignition behavior of gasoline/ethanol blends at engine-relevant conditions

Ethanol is an attractive oxygenate increasingly used for blending with petroleum-derived gasoline yielding beneficial combustion and emissions behavior for a range of internal combustion engine schemes, including stoichiometric spark-ignition and low temperature combustion (LTC). As such, it is important to fundamentally understand the autoignition behavior of gasoline/ethanol blends. This work utilizes a rapid compression machine (RCM) and a homogeneous charge compression ignition (HCCI) engine to experimentally quantify changes in fuel reactivity, through ignition delay times and preliminary heat release, for blends of 0 to 30% vol./vol. into a full boiling range research gasoline (FACE-F). Diluted/stoichiometric and undiluted/fuel-lean conditions are explored covering a wide range of compressed temperatures and pressures relevant to conventional and advanced, gasoline combustion engines. Detailed chemical kinetic modeling is undertaken using a recently updated gasoline surrogate model in conjunction with a five-component surrogate to model the RCM experiments and provide chemical insight into the perturbative effects of ethanol on the autoignition process.The diluted/stoichiometric RCM measurements reveal that within the low-temperature regime ethanol retards first-stage and main ignition delay times, and suppresses both the rates and extents of low-temperature heat release (LTHR), while within the intermediate-temperature regime ethanol only causes slight changes. Good agreement of ignition delay time and preliminary heat release prediction is found between model and experimental results. Sensitivity and flux analyses further show that ethanol blending effects are dominated by the competition between the H-atom abstraction from ethanol and other fuel components by OH radical at low temperatures, and by HO2 radical at intermediate temperatures. These findings are consistent across both fuel loading conditions explored in this study. In addition, when HCCI engine experiments are mapped onto undiluted/lean RCM measurements under a constant combustion phasing scenario, good correspondence between the two apparatuses is observed for LTHR and start of high-temperature heat release. The current study highlights the importance of characterizing LTHR in predicting fuel behaviors in high-boost/low-temperature engines, and demonstrates that RCM experiments can provide an alternative, and more-efficient avenue for such characterization.

Dynamics of hydrogen–oxygen–argon cellular detonations with a constant mean lateral strain rate

The present work revisits the problem of modeling the real gaseous detonation dynamics at the macro-scale by simple steady one-dimensional (1D) models. Experiments of detonations propagating in channels with exponentially expanding cross-sections were conducted in the H2/O2/Ar reactive system. Steady detonation waves were obtained at the macro-scale, with cellular structures characterized by reactive transverse waves. For all the mixtures studied, the dependence of the mean detonation speed was found to be in excellent agreement with first principles predictions of quasi-1D detonation dynamics with lateral strain rate predicted from detailed chemical kinetic models. This excellent agreement departs from the earlier experiments of Radulescu and Borzou (2018) in more unstable detonations. The excellent agreement is likely due to the much longer reaction zone lengths of argon diluted hydrogen oxygen detonations at low pressures, as compared with the characteristic induction zone lengths. While the cellular instability modifies the detonation induction zone, the detonation dynamics at the macro-scale are arguably controlled by its hydrodynamic thickness. Near the limit, minor discrepancy is observed, with the experimental detonations typically continuing to propagate to slightly higher lateral strain rates and higher velocity deficits.

Comprehensive Comparison of the Combustion Behavior for Low-Temperature Combustion of n-Nonane.

To meet the increasing need for clean combustion, improve the combustion efficiency of fuels, and reduce the pollutants produced in the combustion process, it is necessary to systematically study the combustion of hydrocarbon fuels. An accurate and detailed chemical kinetic model is an important prerequisite for understanding the combustion performance of hydrocarbon fuels and studying complex chemical reaction networks. Therefore, based on ReaxGen, new detailed mechanisms for the low-temperature combustion of n-nonane are proposed and verified in detail in this study. Meanwhile, some international mainstream combustion models such as the LLNL model and the JetSurf 2.0 model are compared with ours, showing that the proposed new mechanisms can better predict the ignition delay combustion characteristics of n-nonane, and they also hold in a wide range of conditions. In addition, the numerical simulation results of the concentration curve calculated for the new mechanisms, especially Model v2, are in good agreement with the experimental data, and the mechanisms can reproduce the performance of the negative-temperature-coefficient behavior toward n-nonane ignition. The numerical simulation results of the laminar flame propagation velocity varying with the equivalence ratio are also in good agreement with the available experimental data. Finally, the ignition delay sensitivity of n-nonane is analyzed by the sensitivity analysis method; the key reactions affecting the ignition mechanism are investigated; and the reaction path analysis is conducted to better understand the models’ predicted performance. In a word, the new mechanisms are helpful to understand the ignition properties of large hydrocarbon fuels for high-speed aircrafts.

An experimental, theoretical and kinetic modelling study on the reactivity of a lignin model compound anisole under engine-relevant conditions

In this study, fundamental ignition delay time (IDT) experiments of anisole covering several compressed pressures (pc=1,2,4MPa) for stoichiometric (ϕ=1.0), lean (ϕ=0.5),and rich (ϕ=2.0) compositions at undiluted, fuel-in-air conditions to reflect application-relevant conditions, were investigated for the first time in the RCM. In addition, to increase the examinable range of temperatures and of IDTs, fundamental experiments in the shock tube (ST) covering the same compressed pressures and stoichiometric and lean conditions were conducted. Overall IDTs were measured in ranging from 0.07 to 274 ms. For all conditions an Arrhenius behavior was observed. Anisole showed lower reactivity than ethanol which is in accordance to the RON of both species. H-atom abstraction reactions on the methyl sidechain were calculated with a CBS-QB3 method. These rates were used in the model developed of this study. The calculated rates are generally lower compared to previously used rates in anisole models, especially for the H-atom abstraction by ȮH. The newly measured experimental data were used to validate a detailed chemical kinetic model. Further, literature available data (jet stirred reactor and flow reactor) were used to tighten the validation framework increasing the confidence in the mechanism. The newly developed model is capable of predicting the reactivity of anisole over the whole investigated RCM regime, the majority of the investigated ST regime and at the same time predicting JSR speciation measurements of available literature data. The analyses of model reveal the crucial role of the phenol sub-chemistry in the oxidation of anisole.

A skeletal n-butane mechanism with integrated simplification method

A new skeletal mechanism of n-butane is developed for describing its ignition and combustion characteristics applicable over a wide range of conditions: initial temperature 690–1430 K, pressure 1–30 atm, and equivalence ratio 0.5–2.0. Starting with a detailed chemical reaction kinetic model of 230 species and 1328 reactions (Healy et al., Combust. Flame, 2010), the directed relation graph method is applied as the first step to derive a semi-detailed mechanism with 134 species. Then, the reaction path analysis in conjunction with temperature sensitivity analysis is used to remove the redundant species and reaction paths simultaneously under the condition of low-temperature and moderate-to-high temperatures, respectively. Finally, a skeletal n-butane mechanism consisting of 86 species and 373 reactions can be obtained. Mechanism validation indicates that the new developed skeletal mechanism is in good agreement with the detailed mechanism in predicting the global ignition and combustion characteristics. The new skeletal mechanism is further validated using extensive available literature data including rapid pressure machine ignition delay time, shock-tube ignition delay time, laminar flame speed, and jet-stirred reaction oxidation, covering a large range of temperatures, pressures, and equivalence ratios. The comparison results demonstrate that a satisfactory agreement between predictions and experimental measurements is achieved.

Comprehensive Chemical Kinetic Model of 2,6,10-Trimethyl Dodecane

As a novel alternative fuel and surrogate component, 2,6,10-trimethyl dodecane has received extensive attention. In order to provide the promise of designing and optimizing the internal combustion engines and propulsion systems by CFD, and provide more choice for branched surrogate component to develop more accurate surrogate model, a comprehensive detailed chemical kinetic model for 2,6,10-trimethyl dodecane has been developed based on 35 reaction classes to numerically describe its experimental observations. The proposed detailed mechanism for 2,6,10-trimethyl dodecane has been validated against with a wide range of experimental data which including ignition delay time, flow reactor and laminar flame speeds. The good agreement between the numerical and the experimental data is observed. Using the kinetic model reduction scheme, a high-temperature and a low-temperature chemical mechanisms were eventually obtained and validated against the detailed mechanism. The successful implementation of kinetic mecha...

Computational investigation on the reaction of dimethyl ether with nitric dioxide. II. Detailed chemical kinetic modeling

Hydrogen abstraction from dimethyl ether (DME) by nitric dioxide (NO2) has been considered to be very sensitive to the DME ignition behavior. Thermal rate coefficients for the reaction of DME with NO2 are computed by employing the multi-structural canonical variational transition-state theory with multidimensional tunneling (MS-CVT/MT) at temperatures from 200 to 3000 K. The B2PLYP/TZVP theoretical level has been verified in the first part of this study against experiment for geometries of stationary points and against accurate CCSD(T)/CBS and CCSD(T)/6-311+G(2df,2p) computations for the energetics related to the title reaction, and then the compound CCSD(T)/6-311+G(2df,2p)//B2PLYP/TZVP computations are performed here to obtain the properties of all stationary points and the geometries, energies, gradients, and Hessians of non-stationary points along each reaction minimum-energy pathway. It has been proposed that the internal rotations in the transition structures are anharmonic and strongly coupled to each other to produce multiple conformations whose contributions are included in their partition function approximations. The previous evaluations for these rate coefficients based on transition-state theory with one-dimensional tunneling corrections and one-dimensional hindered rotor treatments of torsions are essentially distinct from our MS-CVT/SCT results where the critical effects of corner cutting due to small reaction-path curvature are seriously treated via multidimensional small-curvature tunneling (SCT) treatment and torsions are explicitly considered by multistructural treatments, and thus the MS-CVT/SCT rate coefficients are proposed particularly to refine the current kinetic model for DME combustion.

Pore scale numerical simulation of heat transfer in propagating thermal wave during filtration combustion of rich and lean methane-air mixtures

The porous media combustion phenomenon was numerically studied with focus on the heat transfer effect in propagating combustion wave for lean and ultra-rich mixture compositions using the approach when the three-dimensional porous structure and interstitial flow are simulated directly at pore scale with explicit consideration of the thermal interaction between fluid and solid phases including the detailed chemical kinetics model and solid-to-solid radiation. The results demonstrate that irregularity of the porous structure leads to a large spatial variation of the process parameters and the flow inhomogeneity. The most intensive heat sources placed within the cavities where the flow is developed. During the process, the interface heat transfer and radiation contribute to heat recuperation mechanism that leads to thermal non-equilibrium in the combustion wave. The heat is transferred through the bed via radiation layer-by-layer due to restricted visibility of the particles. The numerical data about a local variation of the process parameters were presented. The data of this type can be used for modification of the volume-averaged models within the context of spatial variation consideration. It was shown that there is a correlation between the heat release rate, the interface heat flux, the radiative heat flux, and its root mean square values.

2-5 詳細反応化学速度モデルを用いた噴流床石炭ガス化炉における芳香族炭化水素の改質およびスス生成シミュレーション

2-5 詳細反応化学速度モデルを用いた噴流床石炭ガス化炉における芳香族炭化水素の改質およびスス生成シミュレーション