Bare with me, I'm very new to this. I am trying to build a 'flow bench'. I need to be able to flow from 0-3000cfm of air through a 4" tube and be able to measure this airflow. Pressure will range from 0-40psi. I have tried to come up with several different ways to design this. I thought about buying a race supercharger that could produce the airflow, and spin it with an electric motor. But I'm sure the electric motor would be very expensive as it would have to be 100hp. and spin to 8000rpms. So now, my idea is to get a very large tank to hold compressed air. Like a giant version of what I have in my shop. Then we can just open a valve to vent this compressed air into the tube/pipe running to the flow bench. So, what I'm trying to figure out is how to determine: 1.) The volume of tank needed. 2.) What kind of pressure do I need to compress the air in this tank to, so the air supply will last long enough for us to take our measurements. 3.) How long will said supply flow air at 3000cfm through a 4" tube? We will be measuring airflow at 37 different points from 0-3000cfm, not sure what kind of time it will take to run this range and measure the airflow through that scale. This is because I don't know how we are going to adjust the airflow yet. 4.) I would also like some suggestions on what to use for some type of a valve that we can adjust the airflow precisely from 0-3000cfm. Anyway, any suggestions would be appreciated. I'm trying to learn and at the same time, build this as economically as possible as I don't have deep pockets. I was hoping to possibly buy a used propane tank, but I need to know what size. And if you can help me determine how long the air will last vs what size tank, I can make an educated decision on size.