Less-Is-More Airbag Exploits Bernoulli Effect

Swedish supplier Autoliv has developed a new airbag that leverages fundamental fluid dynamics to inflate larger airbags using a small single-stage inflator. The company is the world’s largest provider of airbag systems, modules, and components.

The Bernoulli Airbag meets FMVSS208 low-risk deployment requirements while filling a large 155-liter airbag from a compact single-stage inflator. It can do this because rather than generating all the gas needed to fill the bag, the Bernoulli Airbag draws in surrounding air in addition to the gas it generates.

Autoliv says this smaller inflator lets automakers shorten development time and reduce cost when deploying it in their vehicles.

“We have developed a way to inflate very large airbags, like the ones needed in newer electric vehicles with roomier cockpits and comfort seating, with a smaller single-stage inflator,” said Autoliv chief technical officer Jordi Lombarte. “Additionally, the Bernoulli Airbag generates less heat, is lighter, and can reduce customer development testing in the United States by more than 30 percent.”

You’ll recall that Swiss mathematician and physicist Daniel Bernoulli described fundamental principles of fluid dynamics that explain many phenomena such as how airplanes fly. Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure.

Autoliv applies this theory to add outside air to the inflation gases generated by the Bernoulli Airbag’s inflator. It works like a carburetor, but rather than using airflow to draw in fuel, it pulls in more air.

The module fires inflation gases at supersonic speed through multiple inlet tubes to the airbag. As the gas flows through the tubes, it draws surrounding ambient air into the chamber with the gases, creating aspiration, and will inflate a much larger airbag with an even smaller inflator than required today.

Autoliv says the company will have the Bernoulli Airbag in production during the third quarter of 2023.