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November 22, 2016, 08:06 |
3 Stage axial compressor CFX Setup
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#1 |
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Hi guys,
I would like to set-up a 3 stage compressor flow with ANSYS CFX. The rotor speed is 3800 rev/min. My task is to calculate the compressor performance. I am struggeling with the setup of the interfaces and domains and I hope you could help me with this. I have set the parameters as follows. Inlet: P-Total= 101325 Pa Outlet: P-static=170000 Pa k-e Turb model My questions are:
Thank you for your help Last edited by knixxor; November 22, 2016 at 13:57. |
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November 22, 2016, 16:39 |
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#2 | ||||||
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Glenn Horrocks
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I am not a turbomachinery expert but I will answer what I can:
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November 22, 2016, 17:11 |
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#3 | |
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turbo4life
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My answers to your questions are in red below:
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November 22, 2016, 17:13 |
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#4 |
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turbo4life
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If you are interested in getting better at CFX, I would recommend signing up for my course at Solid Professor. https://app.solidprofessor.com/lmsap...20/lessons/501
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November 23, 2016, 13:29 |
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#5 |
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Thank you guys,
I will take your tips into account for the setup. However, maybe you can help me with another issue regarding a similiar setup. In addition, I have to simulate the flow through the fan + compressor and bypass as well. Of course, the fan blades, the splitter (bypass flow) geometry are larger than the compressor blades. And now I am struggeling with the meshing of all components. I have meshed all blades with TurboGrid and in TG they look fine for me. But when I put all blades + splitter together in CFX they are great differences in the mesh sizes. The fan blade is round about 10 times larger than the compressor blades, which means the mesh cells of the fan and the compressor blades have a 10:1 ratio and I think this will definitely lead to numerical issues. The splitters is meshed with ICEM and in the global view it has nearly the same size as the fan blade domain. What is the common way to connect large and small geometries? Should I refine the fan blade mesh and the splitter in order to get the same cell-size in global? If yes, I would have a extremely fine mesh for the fan and a medium mesh for the compressor. Or it is ok for CFX to have great differences of the mesh density in one simulation? Can you follow my question? I would be rather happy, if you can help with this. |
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November 23, 2016, 13:35 |
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#6 |
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turbo4life
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This is a very good question, and the answer is "it depends". Since you are already using a stage interface, the rotor/stator interaction is captured, but depending on the spacing between the blade rows, the relative mesh densities can have anywhere from a minimal to a significant impact. Since you will have vortex shedding after each blade row likely bleeding into the interface, my recommendation would be to build a small stationary volume (between the large and small rows) that you can mesh independently using ANSYS meshing or ICEM. That way you can control the density in and out to match what you have from turbogrid without sacrificing too much in terms of computational cost. Does that make sense?
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November 23, 2016, 13:59 |
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#7 | |
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November 23, 2016, 14:06 |
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#8 | |
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turbo4life
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November 23, 2016, 14:20 |
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#9 |
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Okay, perfect. Thank you for your help .
Before I start meshing: In my opinion, creating an unstructured mesh would be a better option to take the gradient in mesh density into account. Am I correct? |
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November 29, 2016, 13:38 |
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#10 |
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The single CFD shot of your turbofan compressor domains will require a lot of computing resources because of required mesh quality. One bottom line is to keep the similar mesh density near all of the endwalls including the fan and bypass passage for an acceptable yplus, and also at every interface of different domains. One tip is to allow quite larger cells away from walls in the inlet, fan and bypass to save resources. You need to get a smooth transition from fine to coarse grids, of course.
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