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Inlet to Outlet Chart with Streamline Location Problem

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Old   June 11, 2018, 23:53
Default Inlet to Outlet Chart with Streamline Location Problem
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limlibin
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Hi everyone,

I had a problem about the Inlet to Outlet chart.
My Total Pressure graph had a "jump" between the Rotor to Stator.
Pressure graph plot not nice with it.
Did anyone know what happen? What is the ideally graph should i had to?
Thank you.
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Old   June 12, 2018, 01:40
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You are plotting parameters across an interface. On one side of the interface the velocities are referenced to a stationary frame of reference and on the other side of the interface the velocities are referenced to a rotating frame of reference. This means that parameters which are a function of velocity (such as total pressure) will be discontinuous across the interface. If you want to see a continuous line try variables like total pressure in stationary frame.
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Old   June 12, 2018, 02:46
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Hi,

Thanks for you reply.
I had set up
INLET : Total pressure 1atm and Total temperature 300K
OUTLET : Static pressure 2.5atm
Do I need to exchange my inlet conditions ?
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Old   June 12, 2018, 02:59
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No. It has nothing to do with the setup of your calculation.
In Post you have to plot "Total Pressure in Stationary Frame". That's all.
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Old   June 12, 2018, 08:51
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Sorry, I dont know what do you mean about "Total Pressure in Stationary Frame" ?
Is it the frame type from CFX Setup ? I had set the frame type of rotor and stator with stationary.
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Old   June 12, 2018, 09:16
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You have a rotating domain and a stationary domain.
Therefore, you have a Rotating Frame of reference and a Stationary Frame of reference.
So you can plot the velocity relative to the Rotating Frame and relative to the stationary Frame. The same holds for Total Pressure.
If you plot relative to stationary Frame of reference you will obtain continous graphs.

Last edited by Gert-Jan; June 14, 2018 at 05:12.
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Old   June 14, 2018, 04:49
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Hi,

Thanks for you reply.
I had another question.
I had found that when total pressure in rotor is decreasing. Is it seem like abnormal?
Is it about the setting or the blade problem?

Thank you
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Old   June 14, 2018, 05:13
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I don't understand your question. Please rephrase.....

Last edited by Gert-Jan; June 18, 2018 at 01:40.
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Old   June 14, 2018, 06:38
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I am doing the centrifugal compressor.
In theoretical the total pressure should be increase when the fluid flow from inlet to outlet.
But I found from the graph (streamline location vs total pressure) , it had shown me the total pressure decrease.

https://drive.google.com/file/d/12lZ...TAc0RNtmD/view

Last edited by deii; June 14, 2018 at 08:29.
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Old   June 14, 2018, 08:10
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I am totally confused here. You write centrifugal compressor, but the images in your first post look very much like an axial machine?


And, what kind of total pressure are you looking at? Total Pressure in Stn or Relative Frame?
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Old   June 14, 2018, 08:28
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I am looking for Total Pressure in Stn. However I am not sure the graph correct or not?
I had put Total Pressure in Stationary Frame.

Last edited by deii; June 15, 2018 at 05:28.
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Old   June 15, 2018, 05:14
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Can you just attach the images directly like you did with your first post? I dont want to log into my google account from some forum links.
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Old   June 15, 2018, 05:27
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Old   June 15, 2018, 08:39
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Ok, obviously centrifugal compressor ... change of perspective is never a bad thing.



Honestly, I don't know how the total pressure in stn frame behaves in the rotating domain of a centrifugal compressor. However, I'd recommend grabbing a piece of paper and working out velocity triangles for your geometry (look it up in a book if you don't know how to do that). Then you know how the velocity components behave at in- and outlet, and it should be easier to understand how the pressure variables behave.
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Old   July 31, 2018, 03:55
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Hi,

I had changed the total pressure to stationary frame. Is it problem occurs at interface between stator to rotor?

Setting:
1) Stage (Mixing-Plane)
2) Specified Pitch Angles 360 degrees (if set with 1 degree will appear error message)
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