[merouaneaero]

Hello everyone I hope you are all doing well,
I am doing CFD simulations on a centrifugal compressor and my goal for the moment is to recreate the compressor performance maps obtained experimentally.
My problem is when convergence is obtained the pressure ratio is different from what is expected.
And even the mass flow in the results is different than what is defined as a boundary condition.
I am using the P-total inlet Mass Flow Outlet boundary conditions ans also the Mass Flow Inlet P-static outlet boundary condition and the problem occurs in both of them.
The ambiant pressure at the experimentation time is 1 atm.
To use the last boundary condition properly "Mass Flow inlet P-static outlet " what is the value of the P-static outlet that I should input, should it be the reference pressure value multiplied by the pressure ration, if so what value you put if you choose the reference pressure to be 0.
I think I am missing something or making a beginners mistake so I am sorry if I am asking an obvious question and thank you for your response.

[Opaque]

Start by knowing your absolute pressures (either total or static)

Choose the reference pressure you would feel comfortable with

Subtract the chosen value from the your absolute pressures

Set the Domain/Reference Pressure to the chose value, and the inlet/outlet boundary to the values obtained after subtracting the reference pressure..

You should be set now.


When comparing mass flow, be careful with your performance curve experimental data. Is it plotted normalized? That is, is it using corrected mass flow or true/physical mass flow?

[merouaneaero]

I understand you Opaque thank you so much, you have resolved my pressure problem.
For the mass flow though I don't understand what do you mean by normalized, I have the exact numerical data in a .dat file for the mass flow and pressure ratio.
The mass flow values are the corrected mass flow , the operating conditions were 0.6 bar and 296 k for the inlet but the values in the files I have are corrected to 1.013 bar and 288.15 k.
Does cfx use the corrected mass flow or the actual mass flow, in this case how would I know the corrected mass flow at the outlet since I don't have the total temperature of the fluid and what values should I use the corrected ones or the actual ones since I don't know how cfx works in this regard it is really confusing to me also what total temperature should I use 288.15 or 296 (it should be 288.15 if I choose the corrected inlet mass flow), I really appreciate your help thanks allot.

EDIT : THE COMPRESSOR IS STATIONARY SO THERE IS NO LINEAR VELOCITY JUST THE ROTATION OF THE COMPRESSOR.

[Opaque]

Ansys CFX reports actual mass flows.

You should know (the background of) how the experimental data was reduced/normalized and its error bars; otherwise, the data is useless. Similarly, the Ansys CFX results w/o knowing if they are mesh independent are just a trend, and likely of no value.