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WILLIAM DIETER May 1, 2002 13:59

I am having trouble figuring out the final velocity of air applied to a six foot tube with a .5" diameter from an unlimted 3000psi source... can anyone help?

Respectfully, William Dieter

John Dreese May 2, 2002 02:34

With that pressure ratio (3000psi to Ambient), you'll have choked flow through the pipe. The maximum speed will be Mach 1. Assuming isentropic flow from standard temperature to Mach 1, your static temp will drop to about 433 degrees Rankine. That makes the exit speed of sound 1020 feet/second or 696 mph. So, that's about the speed of your exiting flow. Increasing your inlet pressure will just increase the mass flow (density). Increasing inlet temperature will increase your speed. My calcs are a little rusty but I think that's right.

That calculation doesn't take into account pressure losses through the pipe or what happens as the jet expands into an open space.

John Dreese

Maker of DesignFOIL

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