Conditions of self-ignition upon pulsed high-pressure injection of combustible gases into a bounded space

The temperature of a fuel-air mixture in the vicinity of a contact discontinuity formed in the process of exhaustion of a combustible gas (hydrogen, methane, and propane) into air after the shock-tube membrane breakdown is quantitatively evaluated. It is shown that conditions necessary for self-ignition of such a mixture are reached only when the shock wave reflected from the tube bottom passes through the mixture. An increase in the initial pressure of air in the tube exerts a dramatic adverse effect on the probability of self-ignition of the mixture. In addition, the calculation shows that favorable conditions for self-ignition of a methane- and propane-air mixtures, even after the secondary compression of the mixture behind the reflected-wave front, are observed only for a comparatively high pressure of the combustible gas prior to its exhaustion into the tube and simultaneously for a low initial pressure of air in the tube. The calculation results are in good agreement with available experimental data for a hydrogen-air mixture.