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September 23, 2009, 06:12 |
Problem with centrifugal pump calculation
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#1 |
Member
Michiel
Join Date: Jul 2009
Location: The Netherlands
Posts: 42
Rep Power: 17 |
The idea is to create a predicted pump curve which gives information about the maximum pressure at a fixed flow and a fixed inlet pressure. Based on this information I like to calculate the pump power (mechanic and hydraulic), and the efficiency.
I use Floworks to perform the analysis. The medium is water (pre defined in floworks). First I like to set up a basic calculation method, and then I can analyze some pumps and compare results tot actual test data. For calculating the maximum outlet pressure at fixed flow and inlet pressure I set the following boundary conditions: -At inlet a total pressure of 1 bar -At oulet a outlet volume flow of 2 m3/sec -The impeller walls which are in contact with the fluid are defined as ideal wall -The pump casing and the inlet pipe are defined as real wall I have set the following goals: -Bulk av static pressure at inlet and outlet -Equation goal to calculate the pressure drop (used for convergence) -Inlet volume flow (used for convergence) -Outlet volume flow (used for convergence) When I run the calculation I can’t get a good result. The most strange is that the inlet flow is not the same as the outlet flow. During the calculation the inlet flow varies from -8 m3/sec up to 12 m3/sec. After 400+ iterations the inlet flow keeps bouncing up and down. This indicates there is something wrong. The inlet and outlet flow should be exactly the same. When I use the same model to solve the volume flow at fixed inlet and outlet pressure, there is no problem. Also when I solve the inlet pressure at fixed outlet pressure and fixed inlet volume flow, there is no problem. Does anyone has an idea what is going wrong over here? |
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September 23, 2009, 06:22 |
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#2 |
Member
Michiel
Join Date: Jul 2009
Location: The Netherlands
Posts: 42
Rep Power: 17 |
Ow sorry.... I see I forgot to mention some more information.
I use the local rotating region for the impeller. Angular velocity will be around 325 rpm. The numbers i use are normal for this type of pumps, so i am not analyzing something far away from the actual duty point. |
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June 17, 2012, 22:32 |
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#3 |
New Member
Wang Yuchuan
Join Date: May 2012
Posts: 1
Rep Power: 0 |
I have met the such problem, when i generate the finer grids, the convegence shows good.
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