PERFORMANCE AND CO PRODUCTION OF A NON-AZIDE AIRBAG PROPELLANT IN A PRE-PRESSURIZED GAS GENERATOR

This paper presents a numerical study of the transient operation of a pre-pressurized (augmented) airbag inflater. Augmented inflaters dilut e hot gaseous products of propellant combustion with ambient temperatu re, high-pressure stored gas before discharging the mixture into the a irbag. The solid propellant selected for this study is a non-azide pro pellant composed of a mixture of azodicarbonimide, potassium perchlora te, and cupric oxide. Predicted performance of the inflater is present ed in terms of pressure, temperature and mass flow rate profiles in th e inflater and discharge tank which is used to simulate an airbag. Thi s work also predicts first-order estimates of gas-phase species exit c oncentrations and characteristic residence times in the inflator. Carb on monoxide, produced as a product of combustion from the high flame t emperature propellant, is partially converted to CO2 as it flows from an internal combustion chamber to the pressurized plenum before being discharged into the airbag. Specifically, the production/destruction o f CO is tracked using three different gas-phase reaction models: 1) ch emically frozen, 2) local (shifting) equilibrium, and 3) finite-rate e lementary kinetics. Results presented in this paper demonstrate the ne cessity of an airbag combustion program that includes finite-rate, gas -phase kinetics. Results from the finite-rate CO chemistry model are q ualitatively consistent with experimental results reported by others f or the same propellant formulation in a similar operating environment.