Air Bag Inflation Rate

1. Feb 22, 2009

faiz513

I am designing an exhaust powered vehicle car jack air bag. I have calculated the mass flow rate and velocity of the exhaust gases leaving the vehicles exhaust pipe. I need to calculate the amount of time it will take to inflate an air bag of a particular size. What equations do I need to be using in order to calcualte the rate of inflation? Also I need to calcuate the stresses the air bag will have to withstand in order to lift the vehicle. I have taken fluid mechanics but I am having trouble figuring out which equations to use.

Thanks for the help......

2. Feb 22, 2009

mgb_phys

PV = nRT

3. Feb 22, 2009

faiz513

how would I get (n) for the above equation?

4. Feb 22, 2009

mgb_phys

n is the number of moles.
Mostly coming out of the exhaust is unburnt N2 (80%) of air, CO2 an H2O
You said you know the mass flow of exhaust, you can probably lookup the chemical composition of exhaust (it's probably in the clean air act etc) otherwise just assume air.
The tricky part is probably water, it will come out as a gas but condense in the bag.