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problems with compressible flow in turbine

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Old   June 12, 2003, 15:02
Default problems with compressible flow in turbine
  #1
Birute
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Hello everybody, I am modelling two-stage steam turbine. I am using pressure boundaries for inlet and outlet, k-e high Reynolds number turbulence model, implicit multiple rotating reference frame and static enthalpy (for temperature calculations). Inlet conditions: static pressure 4.66E+4 Pa(relative) and temperature 323K, outlet conditions: -1900 Pa (relative) and temperature 292.8K. Flow is compressible (Ideal-f(T,P)), for molecular viscosity: Sutherland correlation. I am using MARS differencing scheme with blending factor 0.5 The main problems is with temperature, velocities and turbulent kinetic energy in the last frame (2-nd stage rotor part). The temperature drops down and value at the outlet is about 274K, which not correspond with boundary value at all. The velocities are much higher. The turbulent kinetic energy values are also very high at this part. The pressure values are very OK. I could be very thankful for any suggestion, why it happens like this. What I am doing wrong? Please, help me!!! Best regards, Birute
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Old   June 12, 2003, 23:43
Default Re: problems with compressible flow in turbine
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CJ Tune
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I think you should use 'total enthalpy' conservation for compressible flow temperature calculation.
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Old   June 13, 2003, 08:22
Default Re: problems with compressible flow in turbine
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Birute
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Thanks for suggestion, but I already tried to use total enthalphy option, but it doesn't work. The total enthalphy in whole domain is the same. Regards! Birute
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Old   June 13, 2003, 09:10
Default Re: problems with compressible flow in turbine
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Joern Beilke
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It is a bug in version 315 with the pressure work term.

You have to set "rcon 146 1"
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Old   June 14, 2003, 09:59
Default Re: problems with compressible flow in turbine
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CJ Tune
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Does this apply to all cases or just for compressible flow?
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Old   June 14, 2003, 15:34
Default Re: problems with compressible flow in turbine
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Joern Beilke
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It seems to apply for rotating frames calculations only. Sliding mesh works without the rcon.

Since the temperature is not a function of the pressure for incompressible flows I would guess that it can not be very important there. So you can either try it or ask the support.
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Old   June 20, 2003, 04:32
Default Re: problems with compressible flow in turbine
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Jing
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I have done the similar calculation and have the similar problem. For me it is caused by the Enthalphy definition. So, please have a look if you really define the Total Enthalphy as a constant in your calculation. An other possibility is if you define the rotating velocity in a right direction, and, for the rotor and stator seperately.

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