# Boundary Conditions for an impeller

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 July 8, 2019, 20:11 Boundary Conditions for an impeller #1 New Member   Join Date: Jul 2019 Posts: 9 Rep Power: 6 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.

 August 2, 2019, 08:44 #2 New Member   Eyyup DUMAN Join Date: Dec 2013 Posts: 1 Rep Power: 0 hi , Did you try inlet BC :0 pa outlet BC : ...kg /s Mass flow?

 August 3, 2019, 02:04 #3 Senior Member   Hamid Zoka Join Date: Nov 2009 Posts: 282 Rep Power: 18 Hi; - 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. Regards

 Tags cfd, fan, impeller, mrf.