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Need Help With Pressure Downstream of Solenoid.

  1. Oct 23, 2007 #1
    I have an air cannon, which launches a ping pong ball. The setup for this includes the reservoir, solenoid and barrel. I have to find a function for the range of the launcher. I am currently stuck at working out the downstream pressure for the solenoid. At the moment I have the mass flow rate through the solenoid and the gauge pressure for the reservoir. I was wondering if there was a way of using these values to calculate the downstream pressure acting on the ball?

    Any help would be greatly appreciated.
  2. jcsd
  3. Oct 24, 2007 #2


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    I would look at it more from the standpoint of what force does the mass flow impart on the ball, not what the pressure is. To start with a very rough calculation, calculate the force produced by your mass flow if it were to impinge on a flat plate. That will be your maximum possible propulsive force. You know that you'll never get better than that.
  4. Oct 24, 2007 #3
    Thanks for your help Fred. I used the equation: F = mass_flowrate * gas_velocity to work out the force on the ball. This seems to give reasonable answers.
  5. Oct 24, 2007 #4


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    Don't forget to add a small fudge factor in there as well because there will be some leakage past the ball.

    Also, don't forget that if you have an appreciable delta P across the valve, chances are the flow will be choked.
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