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[Sponsors] |
August 13, 2012, 21:48 |
Questions about cfx
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#1 |
Member
Stefan
Join Date: May 2012
Posts: 49
Rep Power: 14 |
Hi.
There is a question with the gear pump. When the inlet was set as 0MPa, and massFlow at outlet(pressure was set 0MPa) was 2.4kg/s. However, when the pressure at outlet was set 5Mpa,the massFlow at outlet was nearly 1.2kg/s. So this is consistant with the real situation,or something is wrong with my setup. I did this simulation with the method of Immersed Solid in CFX. thanks! |
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August 14, 2012, 08:00 |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,716
Rep Power: 143 |
I do not know what you are modelling in detail so cannot say for sure, but your results could be possible. You get 2.4 kg/s flow with no pressure gradient, and when the pump is pushing against a 5MPa pressure the flow rate slows to 1.2kg/s. With a positive displacement pump like this the loss in flow is presumably due to fluid leaking around the impeller.
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August 14, 2012, 10:12 |
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#3 |
Member
Stefan
Join Date: May 2012
Posts: 49
Rep Power: 14 |
It is my model.
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August 14, 2012, 10:20 |
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#4 |
Member
Stefan
Join Date: May 2012
Posts: 49
Rep Power: 14 |
At the very beginning, I thought it is the problem of leakage.But the radial gap, axial clearance and gear backlash were all set zero.When I set outlet 20MPa,the massflow at outlet was 0kg/s,also the pressure at inlet was 8MPa, while the toal pressure at inlet I set before was 0MPa.
So I can't figure out the problem . my model? mesh size? |
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August 14, 2012, 19:17 |
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#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,716
Rep Power: 143 |
Don't forget immersed solids work by using a scaling factor on a momentum source term. Flow will slowly filter through the solid region if that factor is not set high enough. Have you done a sensitivity analysis of the factor?
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