Experimental study and modeling of shock tube ignition delay times for hydrogen–oxygen–argon mixtures at low temperatures

Abstract

Recent literature has indicated that experimental shock tube ignition delay times for hydrogen combustion at low-temperature conditions may deviate significantly from those predicted by current detailed kinetic models. The source of this difference is uncertain. In the current study, the effects of shock tube facility-dependent gasdynamics and localized pre-ignition energy release are explored by measuring and simulating hydrogen–oxygen ignition delay times. Shock tube hydrogen–oxygen ignition delay time data were taken behind reflected shock waves at temperatures between 908 to 1118K and pressures between 3.0 and 3.7atm for two test mixtures: 4% H2, 2% O2, balance Ar, and 15% H2, 18% O2, balance Ar. The experimental ignition delay times at temperatures below 980K are found to be shorter than those predicted by current mechanisms when the normal idealized constant volume (V) and internal energy (E) assumptions are employed. However, if non-ideal effects associated with facility performance and energy release are included in the modeling (using CHEMSHOCK, a new model which couples the experimental pressure trace with the constant V, E assumptions), the predicted ignition times more closely follow the experimental data. Applying the new CHEMSHOCK model to current experimental data allows refinement of the reaction rate for H+O2+Ar↔HO2+Ar, a key reaction in determining the hydrogen–oxygen ignition delay time in the low-temperature region.