The effect of temperature on the adiabatic burning velocities of diluted hydrogen flames: A kinetic study using an updated mechanism

Abstract

The effect of temperature on the adiabatic burning velocities of diluted hydrogen flames has been analyzed using an updated version of the Konnov detailed reaction mechanism for hydrogen. The contemporary choice of the reaction rate constants is provided with the emphasis on their uncertainties, and the analysis of the performance of the updated mechanism is presented and compared to the previous version for a wide range of validation cases: jet stirred and flow reactors; oxidation, decomposition and ignition in shock waves; ignition in rapid compression machines; laminar burning velocity and flame structure. An overall improvement of the mechanism performance was observed, particularly for the shock tube and flow reactor studies. Temperature dependence of the burning velocity, SL, is commonly interpreted using the correlation SL=SL0 (T/T0)α. The updated mechanism was applied to study the behavior of the power exponent α for H2+O2+N2 flames in a wide range of stoichiometry and dilution ratios. The simulations were compared to the available experimental results, either taken from the literature or evaluated in the present study from the existing burning velocity data. The equivalence ratio and N2 content in the mixture were found to have significant influence on the temperature power exponent. The dependence of the temperature exponent on the fitting temperature range was observed and discussed. This effect was found to cause significant discrepancies in the burning velocities at high temperatures, if obtained with empirical correlation.