axial fan convergence problem
 

Hello all,
i am simulating an axial fan with 1 passage (30 degree). The setting and method are as follows:

FLUENT14.5, sliding mesh, transient, pressure-based, compressible, SST-K-Omega, y+ ca. 2, fan 1000rpm, time step 2.5e-05, CFL=1.0. Inlet: mass flow rate 0.6kg/s, Outlet: pressure-outlet

my problem is, after calculation of 6 revolutions, the mass flow rate at outlet oscillates between 0.5-0.7kg/s. Can anyone give me suggestions to improve it?

Hi,
Does anyone have the fan simulation experiences to improve the mass flow unbalance? Thank you!