Аннотация:The effect of a relatively small addition of unsaturated gaseous hydrocarbon (propylene)on the detonation wave dynamics in a stoichiometric hydrogen–air mixture was studied by numerical simulation. The effect of the propylene concentration on the development of detonation in themixture initiated directly by energy supply from outside in a small volume within a short time wasstudied at different initial temperatures of the mixture. A detailed hydrogen combustion mechanism and the key propylene hydrogenation reaction were used. Propylene is readily hydrogenatedwith the removal of atomic hydrogen from the reaction chain. This leads to an increase in theself-ignition delay of the mixture behind the leading shock wave, and at a sufficient concentrationof the added inhibitor, to the breakdown of the cellular detonation structure and detonation degeneration.