As a part of the Automated Driving Systems (ADS) strategy, the developed aspirated inflation system is applicable for conventional and autonomous motor vehicles where larger airbags are required and the location of vehicle occupants is less precise. It is built to provide for the air entrainment into an airbag from the car passenger compartment. The objective is set to inflate a 50 L airbag within 30 ms with an aspiration ratio, A ≥ 4. Advantageous features of the offered system are a much smaller (less than 1/3) gas generator and stopped airbag deployment on contact with an occupant that eliminates out-of-position occupant injuries.
Regarding engineering, the aspirated inflator is a supersonic pulse ejector designed on the basis of PrandtlMeyer effect realization. The modeling includes numerical flow simulation combined with subsequent engineering design, fabrication, and experimental testing of models. The results are presented for the “cold-gas” inflator testing where the gas generator operation is imitated by a jet generation from a compressed-air tank using a specially designed high-speed valve. Such an approach enables the verification of the numerical procedure and calculation results obtained for “cold” and “hot-gas” cases. The experimentally found “cold-gas” aspiration ratio is in a good agreement with the numerical prediction varying within A=3.1 – 2.1 depending on a particular design and the operational motive pressure. For the gas generator case, the aspiration ratio values are calculated to be ≥4.
Several different designs of the supersonic pulse aspirator are modeled, designed, manufactured, and tested including outer and inner circumferential slit nozzle and multi-nozzle systems. To meet the engineering requirements, multi-stage multivariate studies of measured pressure fields and airbag inflation process are performed.