[Cafard]

Hi everybody

I want to simulate a compressor performance
I know the input pressure and the compressor rotating speed
but i don't know the output pressure or speed

how should I set the output area condition?

[evcelica]

Well, the pump should have a curve, so the flow will be dependent on the delta P. Whatever you model will give you one point on that curve.

[Martin_Sz]

You can define opening on the outlet

[Blanco]

If you are referring to something already tested then you should have a characteristic curve of that compressor, as evcelica said.
If this is a new design component and you want to know how good it is, than you can proceed like this:
- fix a mass flow rate at your outlet (maybe the design mass flow rate to start)
- proceed with your sim with your actual working conditions (speed, inlet pressure), again in design condition to start
- when you get the results you have to measure the pressure difference between outlet and inlet of your model. This way you have a "point" on the characteristic compressor working diagram (pressure ratio, mass flow, speed).
- Change the mass flow and repeat everything as long as you want (this point can be inverted with the next one)
- change the speed and repeat everything as long as you want

...as you can see, obtaining a compressor map from CFD simulations is a looooooong process