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 inflator. Augmented inflators dilute hot gaseous products of propellant combustion with ambient temperature, high-pressure stored gas before discharging the mixture into the airbag. The solid propellant selected for this study is a non-azide propellant composed of a mixture of azodicarbonirnide, potassium perchlorate, and cupric oxide, Predicted performance of the inflator is presented in terms of pressure, temperature and mass flow rate profiles in the inflator and discharge tank which is used to simulate an airbag. This work also predicts first-order estimates of gas-phase species exit concentrations and characteristic residence times in the inflator. Carbon monoxide. produced as a product of combustion from the high flame temperature propellant, is partially converted to COz as it flows from an internal combustionchamber to the pressurized plenum before being discharged into the airbag, Specifically. the production/destruction of CO is tracked using three different gas-phase reaction models: I) chemically frozen. 2) local (shifting) equilibrium. and 3) finite-rate elementary kinetics. Results presented in this paper demonstrate the necessity of an airbag combustion program that includes finite-rate, gas-phase kinetics. Results from the finite-rate CO chemistry model are qualitatively consistent with experimental results reported by others for the same propellant formulation in a similar operating environment.