A detailed kinetic mechanism has been developed to simulate the combustion of H2/O2 mixtures, over a wide range of temperatures, pressures, and equivalence ratios. Over the series of experiments numerically investigated, the temperature ranged from 298 to 2700 K, the pressure from 0.05 to 87 atm, and the equivalence ratios from 0.2 to 6.

Ignition delay times, flame speeds, and species composition data provide for a stringent test of the chemical kinetic mechanism, all of which are simulated in the current study with varying success. A sensitivity analysis was carried out to determine which reactions were dominating the H2/O2 system at particular conditions of pressure, temperature, and fuel/oxygen/diluent ratios. Overall, good agreement was observed between the model and the wide range of experiments simulated. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 603–622, 2004

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A comprehensive modeling study of hydrogen oxidation

Detailed chemical kinetic models for the combustion of hydrocarbon fuels

Remaining uncertainties in the kinetic mechanism of hydrogen combustion

Shock tube experiments and chemical kinetic modeling were performed to further understand the ignition and oxidation kinetics of various methane–propane fuel blends at gas turbine pressures. Ignition delay times were obtained behind reflected shock waves for fuel mixtures consisting of CH4/C3H8 in ratios ranging from 90/10% to 60/40%. Equivalence ratios varied from lean (ϕ = 0.5), through stoichiometric to rich (ϕ = 3.0) at test pressures from 5.3 to 31.4 atm. These pressures and mixtures, in conjunction with test temperatures as low as 1042 K, cover a critical range of conditions relevant to practical turbines where few, if any, CH4/C3H8 prior data existed. A methane/propane oxidation mechanism was prepared to simulate the experimental results. It was found that the reactions involving CH3O˙, CH3O˙2, and ĊH3 + O2/HO˙2 chemistry were very important in reproducing the correct kinetic behavior.

Methane/propane oxidation at high pressures: Experimental and detailed chemical kinetic modeling

Chemiluminescence from the OH(A X) transition near 307 nm is a commonly used diagnostic in combustion applications such as flame chemistry, shock-tube experiments, and reacting-flow visualization. Although absolute measurements of OH(X) concentrations are well defined, there is no elementary relation between emission from the electronically excited state (OH*) and its absolute concentration. Thus, to enable quantitative emission measurements, a kinetics model has been assembled and optimized to predict OH* formation and quenching at combustion conditions. Shock-tube experiments were conducted in mixtures of H2/O2/Ar, CH4/O2/Ar, and CH4/H2/O2/Ar with high levels of argon dilution (>98%). Elementary reactions to model OH*, along with initial estimates of their rate coefficients, were taken from the literature. The important formation steps follow: 


(R0)




(R1)



Sensitivity analyses were performed to identify experimental conditions under which the shape of the measured OH* profiles and the magnitude of the OH* emission would be sensitive to the formation reactions. A fitting routine was developed to express the formation rate parameters as a function of a single rate, k1 at the reference temperature (1490 K). With all rates so expressed, H2/CH4 mixtures were designed to uniquely determine the value of k1 at the reference temperature, from which the remaining rate parameters were calculated. Quenching rates were fixed at their literature values. The new model predicts the experimental data over the range of conditions studied and can be used to calibrate the emission diagnostic for other applications, such as measurements in real combustion environments, containing higher order hydrocarbon fuels and lower levels of dilution in air. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 714–724, 2006

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An optimized kinetics model for OH chemiluminescence at high temperatures and atmospheric pressures

The hydrogen-oxygen reaction was investigated using OH absorption and emission measurements of induction times over the temperature range of 1400°–2500°K. The dependence of induction time on composition was studied to measure the relative influence of hydrogen and oxygen concentrations in determining the induction times. Comparison of experimental measurements with computed values obtained from an analytic solution to the rate equations, which is presented in detail, showed that the results could be understood in terms of rate-coefficient parameters which are in agreement with previous studies. The effect of slow vibrational relaxation of O 2 was investigated under conditions where the vibrational relaxation times were comparable to the induction times. The results indicated that in normal studies of hydrogen-oxygen ignition kinetics no effect of slow vibrational relaxation will be observed.

R.F. Stubbeman

Papers

Shock-tube study of the hydrogen-oxygen reaction