[MaoZM]

Hi to All

I'm doing the steady state analysis of an Centrifugal compressor with vaneless diffuser. I've done the simulation with solving the entire domain in rotating reference frame and set the shroud and hub of diffuser as counter rotating wall.

Here my problem is, the results indicated that the Total Temperature and enthalpy decrease form the impeller TE Cut to the diffuser outlet, the Tt difference is above 5K. And since the Tt decrease, the polytropic efficiency of impeller &diffuser is even higher than the impeller alone. So the results is definitely inaccurate.

The turbulence model is SST and wall yplus is around 3. Inlet boundary is Pt and Tt, Outlet boundary is average static pressure(results of mass flow rate outlet still have the problem).Alternate Rotating Model is on. I have change the grid and turbulence model, but the phenomenon still exist. I'm stuck here several weeks, wish somebody can help me. Any suggestion? Thank you~