Alternative Airbag Evaluation Methodology through Cold Gas Inflation System 2008-01-0352
Currently, airbag module development methodology and prototyping heavily relies on the application of single-use pyro-technic, hybrid, or stored gas inflators. A new development test methodology using a Cold Gas System (CGS) is proposed, in which the inflator is replaced by a re-chargeable, high-pressurized, gas compartment that can be rapidly opened using an electronic valve. This new methodology overcomes the problem of variability in inflator output. In a first approach, the methodology is researched by using a single gas in the compartment, i.e. 100% Helium.
At first, an inflator baseline tank test pressure-time curve is established. This can be obtained from any “off the shelf” inflator that is on the market. Once the baseline is determined, the tank test pressure curve is reproduced by the CGS in two steps: (1) the volume and the high-pressure level of the CGS gas compartment is adapted to enable similar molar output to the baseline, so that the final asymptote of the total pressure can be reached; (2) the orifice size of the compartment exit is adjusted to create a pressure rise rate that comes as close as possible to the baseline curve. Through a limited iterative process, a total pressure level and rise rate similar to the baseline can be achieved, i.e. typically in no more than five trials.
The next step in the methodology is to apply this inflator-emulating CGS in the physical airbag. Airbag inflation comparisons will be made between CGS and usual inflator, by looking at pressure versus time curves.
From the preliminary work it is concluded that the CGS can very well and consistently emulate traditional inflators in tank tests, whereas actual application of the CGS in physical airbags still needs further optimization by facilitating the mixing of cold gases.