Air Bag Inflation Rate: Calculating Time & Stress

[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...

 

[dipstik]

turn mass flow into volume flow, i would think. if its a cylindar, then you need to consider the walls of the inflated material as the weakest point (or the seams, or the intake). there should be some mechanics of materials equations for a pressureized cylinlar, then superpose a force on the cylindar from the car load at a sidewall position (say r=R or x=r,y=0.z=0.5h or something). then you need to do all the principle stuff with the design

 

[sir-pinski]

To calculate the inflation rate of an air bag, you will need to use the ideal gas law equation, which relates the pressure, volume, and temperature of a gas. This equation can be written as PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. In this case, the gas is the exhaust gases from the vehicle's exhaust pipe. You will also need to consider the size and shape of the air bag and the pressure at which it needs to be inflated.

To calculate the time it will take for the air bag to inflate, you can use the Bernoulli's equation, which relates the velocity, pressure, and density of a fluid. This equation can be written as P1 + (1/2)ρv1^2 = P2 + (1/2)ρv2^2, where P is the pressure, ρ is the density, and v is the velocity. By solving for time, you can determine how long it will take for the air bag to reach the desired pressure.

In order to calculate the stresses that the air bag will have to withstand, you will need to use the equations for stress and strain in a fluid. These equations take into account the pressure and volume changes in the fluid and the material properties of the air bag. You will also need to consider the weight of the vehicle and the distribution of this weight on the air bag.

It is important to note that these equations are simplified and may not take into account all the factors that can affect the inflation rate and stresses on the air bag. It is recommended that you consult with a professional engineer or conduct further research to ensure the accuracy of your calculations.