Reduced chemical kinetics and test for ethylene combustion
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A reduced chemical kinetics including 20 species and 16 global reactions was obtained by reducing the detailed kinetics for ethylene combustion with the method of quasi-steady state approximation(QSSA).Experimental measurements of a laminar premixed ethylene/O2/Ar flame were carried out on the combustion station at National Synchrotron Radiation Laboratory(NSRL) to validate the kinetics.One-dimensional numerical method was implemented to simulate the test.Comparison with each other shows that the reduced kinetics has the ability to represent efficiently the reaction mechanisms of detailed element reaction model.Some difference between the experimental data and calculated results with detailed kinetics indicates the modifications of the detailed kinetics is needed.Cite
A reduced chemical kinetic model was obtained by reducing the detailed chemical kinetic model GRI-Mech 1.2 for the combustion of methane based on quasi-stationary state approximation(QSSA).This reduced model is composed of 18 species with 14 global reactions.The comparisons between the reduced model and the typical experimental results were made.Computational results of the reduced model were also compared with that of the detailed model by adopting the uniform experimental design technique.The little difference between these results showed that the reduced model using QSSA has the ability to represent efficiently the reaction mechanisms of detailed element reaction model.Therefore,the reduced model is of high precision and the can be used reliably and efficiently.
Chemical reaction kinetics
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New experimental results were obtained for the oxidation of 1,2-dimethylbenzene in a jet-stirred reactor (JSR) at atmospheric pressure in dilute conditions over the temperature range 900–1400 K, and variable equivalence ratio (0.5 ≤ ϕ ≤ 1.5). The data consisted of concentration profiles vs. temperature for the reactants, stable intermediates and final products, measured by sonic probe sampling followed by on-line GC-MS analyses and off-line GC-TCD-FID and GC-MS analyses. The ignition of 1,2-dimethylbenzene-oxygen-argon mixtures was measured behind reflected shock waves over the temperature range 1400–1830 K, at 1 atm, and variable equivalence ratio (0.5 ≤ ϕ ≤ 2.0), using a shock tube (ST). The oxidation and ignition of 1,2-dimethylbenzene under respectively JSR and ST conditions were modeled using a detailed chemical kinetic reaction mechanism (219 species and 1545 reactions, most of them reversible) deriving from a previous scheme proposed for the ignition, oxidation, and combustion of simple aromatics (benzene, toluene, styrene, n-propyl-benzene, 1,3-dimethylbenzene, and 1,4-dimethylbenzene). Sensitivity analyses and reaction path analyses, based on rates of reaction, were used to interpret the results. This study showed the reactivity of 1,2-dimethylbenzene is higher than that of 1,3-dimethylbenzene and 1,4-dimethylbenzene under the above conditions.
Atmospheric temperature range
Reactivity
Autoignition temperature
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A new set of reduced global mechanism with NOx formation has been developed for methane oxidation from the detailed mechanism GRI211 using a computer algorithm for automatic generation of reduced chemistry, after selecting the nonsteadystate species The global mechanism, consisting of 18 species and 14 lumped reaction steps, is based on the sensitivity analysis and the quasisteadystate approximation The 14step reduced mechanism is then used in perfectly stirred reactor and laminar premixed flame, the results show that it exhibits good to excellent performance in predicting a wide range of combustion phenomena and the formation of NO under extensive thermodynamic parametric variations, compared with the results of the detailed mechanism GRI211
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Abstract A method for deriving global ignition kinetics from a detailed chemical mechanism is described, with the lime-temperature range of applicability assessed. The computed ordering of simple hydrocarbons by ignition temperature is consistent with published data. Values of the global rate parameters were found to be only weakly dependent on gas mixing intensity, as determined by a comparison of results from a perfectly-stirred reactor model and plug flow reactor model. Major reaction pathways prior to and at ignition are presented for methane, ethane, ethylene and acetylene in stoichiometric air. Radical chain mechanism analysis of reduced reaction sets demonstrates that values of effective ignition activation energies are dependent almost entirely on one or two chain-branching reactions. These results suggest that the global chemistry representing the weakly reacting regime up to ignition may be determined independent of reactor fluid mechanics and utilized in the prediction of hydrocarbon auto-ignition.
Branching (polymer chemistry)
Acetylene
Autoignition temperature
Stoichiometry
Chain reaction
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Laminar flame speed
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A study was performed to elucidate the chemical-kinetic mechanism of combustion of toluene. A detailed chemical-kinetic mechanism for toluene was improved by adding a more accurate description of the phenyl + O{sub 2} reaction channels, toluene decomposition reactions and the benzyl + 0 reaction. Results of the chemical kinetic mechanism are compared with experimental data obtained from premixed and nonpremixed systems. Under premixed conditions, predicted ignition delay times are compared with new experimental data obtained in shock tube. Also, calculated species concentration histories are compared to experimental flow reactor data from the literature. Under nonpremixed conditions, critical conditions of extinction and autoignition were measured in strained laminar flows in the counterflow configuration. Numerical calculations are performed using the chemical-kinetic mechanism at conditions corresponding to those in the experiments. Critical conditions of extinction and autoignition are predicted and compared with the experimental data. Comparisons between the model predictions and experimental results of ignition delay times in shock tube, and extinction and autoignition in nonpremixed systems show that the chemical-kinetic mechanism predicts that toluene/air is overall less reactive than observed in the experiments. For both premixed and nonpremixed systems, sensitivity analysis was used to identify the reaction rate constants that control the overall rate of oxidation in each of the systems considered. Under shock tube conditions, the reactions that influence ignition delay time are H + O{sub 2} chain branching, the toluene decomposition reaction to give an H atom, and the toluene + H abstraction reaction. The reactions that influence autoignition in nonpremixed systems involve the benzyl + HO{sub 2} reaction and the phenyl + O{sub 2} reaction.
Autoignition temperature
Elementary reaction
Reaction rate
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Experimental and modelling studies on the ignition characteristics of benzene are presented for a wide range of initial conditions. An empirical correlation is proposed for the induction times which show good agreement with the values reported in literature. A comprehensive chemical kinetic reaction mechanism consisting of 70 reactions among 30 species is adopted for computing species concentrations and this is found to be adequate to describe the delay data reported in this paper. The predicted species profiles are found to match qualitatively a few experimental profiles published in literature. The relative contribution of each reaction for the formation/consumption of each species, for a specific reaction time, is determined by a detailed sensitivity analysis.
Atmospheric temperature range
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Abstract : Using CARM (Computer Aided Reduction Method), a computer program that automates the mechanism reduction process, six different reduced chemical kinetic mechanisms for JP-8 combustion have been generated. The reduced mechanisms have been compared to detailed chemistry calculations in simple homogeneous reactor calculations. Reduced mechanisms containing 15 and 20 species were found to give good agreement for both temperature and species concentrations (including NO) in adiabatic perfectly stirred reactor calculations for inlet temperatures from 300-1300 K, pressures from 10-40 atm, stoichiometric ratios from 0.5-2.0 and reactor residence times from 0.1 sec. to near blowout. Reduced mechanisms have also been created that compare well to available ignition delay measurements for JP-8.
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2-Propanol is a renewable alcohol usable as an alternative to petrol-derived gasoline, for which new experimental data for its oxidation and combustion were obtained to better characterize and understand its combustion. Concentration profiles of stable species (reactants, intermediates, and final products) were measured in a pressurized jet-stirred reactor (JSR) over the temperature range of 770−1190 K and for equivalence ratios in the range of 0.35−4. Flame speeds of 2-propanol/air mixtures were measured at 1−10 bar and 423 K, over a range of equivalence ratios (0.7−1.5). The effect of the total pressure on the flame speed was determined for stoichiometric 2-propanol/air flames. The oxidation of 2-propanol in these experimental conditions was modeled using a detailed chemical kinetic reaction mechanism recently proposed for 2-propanol ignition. The kinetic mechanism showed reasonably good agreement with the present experimental data. Reaction path analyses and sensitivity analyses were performed to interpret the results.
Propanol
Jet fuel
Stoichiometry
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