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Let's say I have a centrifugal compressor as shown in the figure and I know the following parameters----1

  1. Thrust
  2. Inlet and outlet pressure
  3. Power required to operate the compressor
  4. Inlet and outlet velocity
  5. Static pressure and pressure
  6. The blade angle

Now I want to know how do I calculate the force exerted by the exhaust coming out?

  • $\begingroup$ The outlet force will be dependant on what happens inside the compressor.... $\endgroup$
    – Solar Mike
    Feb 4, 2019 at 5:19
  • $\begingroup$ ok so how do I get the outward force? $\endgroup$
    – sai teja
    Feb 4, 2019 at 5:25
  • $\begingroup$ By your comments below, you are changing the question, which is also answerable by the use of a textbook. $\endgroup$
    – Solar Mike
    Feb 4, 2019 at 7:06
  • $\begingroup$ I did not change my question, I just mentioned the inlet parameters that I have. $\endgroup$
    – sai teja
    Feb 4, 2019 at 7:16
  • $\begingroup$ You HAVE changed the question, by adding pressure and velocity... If you had those parameters at the beginning you should have specified them. Check out Engineering Thermodynamics Work and Heat Transfer by Rogers and Mayhew, 3rd edition starting at page 456. $\endgroup$
    – Solar Mike
    Feb 4, 2019 at 7:17

1 Answer 1


measure the pressure inside the discharge diffuser with a miniature pitot tube, and the ambient air pressure. the difference will be (delta p). Now measure the area of the discharge diffuser outlet.

the reaction force generated when the blower is running will be approximately

(delta p) x (outlet area).

You could also simply instrument the blower with a force gauge that measures the reaction from the exhaust flow. This has several advantages, as follows:

First, it gives you the actual answer you seek. Second, if you modeled the thrust-generation process mathematically and used that model to predict the behavior of the system, due diligence would require you to verify the correctness of that model by measuring the thrust reaction force in real life. This means you'll be doing this experiment in the future, regardless of the form your model takes.

  • $\begingroup$ But then I have mentioned that I only know my inlet and outlet velocities...now how do I relate the pressure and my velocity? $\endgroup$
    – sai teja
    Feb 4, 2019 at 6:53
  • $\begingroup$ you wanted an answer, I provided one. I will edit and furnish another. $\endgroup$ Feb 4, 2019 at 6:57

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