A detailed chemical kinetic mechanism has been developed to describe the oxidation of small hydrocarbon and oxygenated hydrocarbon species. The reactivity of these small fuels and intermediates is of critical importance in understanding and accurately describing the combustion characteristics, such as ignition delay time, flame speed, and emissions of practical fuels. The chosen rate expressions have been assembled through critical evaluation of the literature, with minimum optimization performed. The mechanism has been validated over a wide range of initial conditions and experimental devices, including flow reactor, shock tube, jet-stirred reactor, and flame studies. The current mechanism contains accurate kinetic descriptions for saturated and unsaturated hydrocarbons, namely methane, ethane, ethylene, and acetylene, and oxygenated species; formaldehyde, methanol, acetaldehyde, and ethanol.

A Hierarchical and Comparative Kinetic Modeling Study of C1 − C2 Hydrocarbon and Oxygenated Fuels

Hierarchical and comparative kinetic modeling of laminar flame speeds of hydrocarbon and oxygenated fuels

https://hal.archives-ouvertes.fr/hal-00848875/document

A comprehensive detailed chemical kinetic reaction mechanism for combustion of n-alkane hydrocarbons from n-octane to n-hexadecane

An updated H2/O2 kinetic model based on that of Li et al. (Int J Chem Kinet 36, 2004, 566–575) is presented and tested against a wide range of combustion targets. The primary motivations of the model revision are to incorporate recent improvements in rate constant treatment and resolve discrepancies between experimental data and predictions using recently published kinetic models in dilute, high-pressure flames.

Attempts are made to identify major remaining sources of uncertainties, in both the reaction rate parameters and the assumptions of the kinetic model, affecting predictions of relevant combustion behavior. With regard to model parameters, present uncertainties in the temperature and pressure dependence of rate constants for HO2 formation and consumption reactions are demonstrated to substantially affect predictive capabilities at high-pressure, low-temperature conditions. With regard to model assumptions, calculations are performed to investigate several reactions/processes that have not received much attention previously. Results from ab initio calculations and modeling studies imply that inclusion of H + HO2 = H2O + O in the kinetic model might be warranted, though further studies are necessary to ascertain its role in combustion modeling. In addition, it appears that characterization of nonlinear bath-gas mixture rule behavior for H + O2(+ M) = HO2(+ M) in multicomponent bath gases might be necessary to predict high-pressure flame speeds within ∼15%.

The updated model is tested against all of the previous validation targets considered by Li et al. as well as new targets from a number of recent studies. Special attention is devoted to establishing a context for evaluating model performance against experimental data by careful consideration of uncertainties in measurements, initial conditions, and physical model assumptions. For example, ignition delay times in shock tubes are shown to be sensitive to potential impurity effects, which have been suggested to accelerate early radical pool growth in shock tube speciation studies. In addition, speciation predictions in burner-stabilized flames are found to be more sensitive to uncertainties in experimental boundary conditions than to uncertainties in kinetics and transport. Predictions using the present model adequately reproduce previous validation targets and show substantially improved agreement against recent high-pressure flame speed and shock tube speciation measurements. Comparisons of predictions of several other kinetic models with the experimental data for nearly the entire validation set used here are also provided in the Supporting Information. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 44: 444–474, 2012

Comprehensive H2/O2 kinetic model for high-pressure combustion

New experimental profiles of stable species concentrations are reported for formaldehyde oxidation in a variable pressure flow reactor at initial temperatures of 850–950 K and at constant pressures ranging from 1.5 to 6.0 atm. These data, along with other data published in the literature and a previous comprehensive chemical kinetic model for methanol oxidation, are used to hierarchically develop an updated mechanism for CO/H2O/H2/O2, CH2O, and CH3OH oxidation. Important modifications include recent revisions for the hydrogen–oxygen submechanism (Li et al., Int J Chem Kinet 2004, 36, 565), an updated submechanism for methanol reactions, and kinetic and thermochemical parameter modifications based upon recently published information. New rate constant correlations are recommended for CO + OH = CO2 + H (R23) and HCO + M = H + CO + M (R24), motivated by a new identification of the temperatures over which these rate constants most affect laminar flame speed predictions (Zhao et al., Int J Chem Kinet 2005, 37, 282). The new weighted least-squares fit of literature experimental data for (R23) yields k23 = 2.23 × 105T1.89exp(583/T) cm3/mol/s and reflects significantly lower rate constant values at low and intermediate temperatures in comparison to another recently recommended correlation and theoretical predictions. The weighted least-squares fit of literature results for (R24) yields k24 = 4.75 × 1011T0.66exp(−7485/T) cm3/mol/s, which predicts values within uncertainties of both prior and new (Friedrichs et al., Phys Chem Chem Phys 2002, 4, 5778; DeSain et al., Chem Phys Lett 2001, 347, 79) measurements. Use of either of the data correlations reported in Friedrichs et al. (2002) and DeSain et al. (2001) for this reaction significantly degrades laminar flame speed predictions for oxygenated fuels as well as for other hydrocarbons. The present C1/O2 mechanism compares favorably against a wide range of experimental conditions for laminar premixed flame speed, shock tube ignition delay, and flow reactor species time history data at each level of hierarchical development. Very good agreement of the model predictions with all of the experimental measurements is demonstrated. © 2007 Wiley Periodicals, Inc. 39: 109–136, 2007

A comprehensive kinetic mechanism for CO, CH2O, and CH3OH combustion

A comprehensively tested H2/O2 chemical kinetic mechanism based on the work of Mueller et al. 1 and recently published kinetic and thermodynamic information is presented. The revised mechanism is validated against a wide range of experimental conditions, including those found in shock tubes, flow reactors, and laminar premixed flame. Excellent agreement of the model predictions with the experimental observations demonstrates that the mechanism is comprehensive and has good predictive capabilities for different experimental systems, including new results published subsequent to the work of Mueller et al. 1, particularly high-pressure laminar flame speed and shock tube ignition results. The reaction H + OH + M is found to be primarily significant only to laminar flame speed propagation predictions at high pressure. All experimental hydrogen flame speed observations can be adequately fit using any of the several transport coefficient estimates presently available in the literature for the hydrogen/oxygen system simply by adjusting the rate parameters for this reaction within their present uncertainties. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 566–575, 2004

https://www.princeton.edu/~combust/research/publications/H2_O2%20Mech%20(Li%20et%20al%20Int%20J%20Chem%20Kin%2036%20566%20575,%202004).pdf

An updated comprehensive kinetic model of hydrogen combustion

Ethanol pyrolysis experiments at 1.7−3.0 atm and 1045−1080 K were performed in the presence of radical trappers using a variable pressure flow reactor. Stable species time histories were determined using continuous sampling, on-line Fourier transform infrared spectrometry, and off-line gas chromatography. The rate constant k1 of the molecular decomposition reaction, C2H5OH → C2H4 + H2O (R1), was determined experimentally. The obtained result agrees very well with extrapolation of the recent shock-tube data of Herzler et al.1 The multichannel unimolecular decomposition of ethanol was also investigated theoretically on the basis of RRKM/master equation calculations. The effects of the hindered rotations in C2H5OH and quantum tunneling on the molecular decomposition reaction were taken into account. The reaction R1 was found to be strongly dependent on temperature and the dominant channel over the range of temperatures 300−2500 K at 1 atm. The calculated k1 is in excellent agreement with the recent theoretic...

http://www.princeton.edu/~combust/research/publications/Ethanol%20Decomposition%20(Li%20et%20al%20J%20Phys%20Chem%20A,In%20Press%202004).pdf

Experimental and Numerical Studies of Ethanol Decomposition Reactions

Experimental profiles of stable species concentrations are reported for pyrolysis of ethanol in a variable-pressure flow reactor at initial temperatures near 950 K and at constant pressures ranging from 3 to 12 atm. We present a new technique for comparison of model predictions with experimental observations in order to overcome the problem that time shifting of zero-dimensional modeling results cannot accommodate the memory effects resulting from phenomena that occur in the mixing–diffuser region in the experiments. Using this new technique, comparison of the experiments with the recent ethanol kinetic model of Marinov shows that the model underestimates the fuel consumption rate and the yields of H2O and C2H4, the main products of ethanol decomposition, as well as CH3HCO and CH4, species related to abstraction channels. Both decomposition and abstraction reactions require significant modifications to improve detailed modeling of ethanol pyrolysis at the conditions of the reported experiments. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 859–867, 2001

Ethanol pyrolysis experiments in a variable pressure flow reactor

Laminar flame speeds of n-decane/air mixtures were determined experimentally over an extensive range of equivalence ratios at 500 K and at atmospheric pressure. The effect of N2 dilution on the laminar flame speed was also studied at these same conditions. The experiments employed the stagnation jet–wall flame configuration with the flow velocity field determined by particle image velocimetry. Reference laminar flame speeds were obtained using linear extrapolation from low to zero stretch rate. The determined flame speeds are significantly different from those predicted using existing published kinetic models, including a model validated previously against high-temperature data from flow reactor, jet-stirred reactor, shock tube ignition delay, and burner-stabilized flame experiments. A significant update of this model is described that continues to predict the earlier validation experiments as well as the newly acquired laminar flame speed data and other recently published shock-tube ignition del...

http://www.princeton.edu/~combust/research/publications/n-Decane%20Flames%20and%20Kinetics%20(Zhao%20et%20al%20Combust%20Sci%20Tech,%20In%20Press%202004).pdf

Juan Li

Papers

An updated comprehensive kinetic model of hydrogen combustion

A comprehensive kinetic mechanism for CO, CH2O, and CH3OH combustion

Experimental and Numerical Studies of Ethanol Decomposition Reactions

Ethanol pyrolysis experiments in a variable pressure flow reactor

BURNING VELOCITIES AND A HIGH-TEMPERATURE SKELETAL KINETIC MODEL FOR n-DECANE