Theoretical simulation of combustion processes of airbag inflators

Combustion and inflation processes of pyrotechnic airbag inflators are simu lated by a theoretical model and numerical code developed in this study. Th e theoretical model considers the ignition and combustion of gas generation propellants of an inflator located in a constant-volume discharge tank. Th e model is based on the transient conservation equations of mass, species a nd energy for the combustion chamber of the inflator and the discharge tank . In addition, the model also includes the propellant burning rate law, the ignition model of gas generation propellants, real gas equation of state, effect of mass and energy fluxes from the igniter to the combustion chamber , heat transfer correlations and filter clogging processes. The theoretical model is solved by a numerical code. The calculated results agree well wit h experimental data. Simulation results indicate that the gas properties in the combustion chamber and the discharge tank change in different fashions owing to the large difference in the volumes of the two regions. In genera l, the gas properties in the discharge tank vary slowly, continuously and a lmost monotonically. It is found that the increase in the pressure exponent of the burning rate law and the inertia coefficient of the filter will inc rease the peak pressures in both regions. The major effect of an increasing mass flowrate from the igniter is the introduction of a local pressure pea k in the combustion chamber at the very beginning of the combustion process es.