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Boundary Conditions for an impeller

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Old   July 8, 2019, 20:11
Default Boundary Conditions for an impeller
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Hello Everyone

I am carrying out a simulation of a steady simulation of a centrifugal fan.

The experimental values I have are :
Total Pressure 918.07 N/m2
Static pressure 86.36 N/m2
Velocity Pressure 94.141 N/m2
Flow rate 3.426 kg/s
And Shaft power 3.62 kW

My boundary conditions are the following
Two stator bodies (inlet bellmouth and stationary outlet ) and a rotatory body (impeller)
Turbulence model: SST
Wall distance Y+ <10
Convergence criteria: 10-5
Number of nodes: 1.3 million
Rotor RPM: 1760

My simulation converges properly and velocity and pressure residuals reach below 10^-5 after 400 steps.

I tried two inlet and outlet conditions :
Operating pressure: 1 atm

Condition 1 : Intel condition: Flow rate : 3.426 kg/s and Outlet pressure : 0 atm

Condition 2 : Inlet condition : Inlet pressure : 918.07 N/m2 and outlet pressure : 0 atm

When I calculate the shaft power from the simulation results the values show more than 50 % error. Calculate shaft power for condition 1 was 1.9 kW and for condition 2 was 0.8 kW.

I am not sure why I am getting such low values. My suspect is the boundary condition.

Please let me know how to solve it.

Thank you

Last edited by rj26; July 9, 2019 at 01:01.
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Old   August 2, 2019, 08:44
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hi ,

Did you try inlet BC :0 pa
outlet BC : /s Mass flow?

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Old   August 3, 2019, 02:04
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- Try total pressure @ inlet and massflow @ outlet.
- Check the physics of flow through the impeller.
- Compare the calculated velocity levels with those available from experimental values.
- Recheck the torque calculation equations.

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cfd, fan, impeller, mrf.

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