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Birute June 12, 2003 15:02

problems with compressible flow in turbine
 
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

CJ Tune June 12, 2003 23:43

Re: problems with compressible flow in turbine
 
I think you should use 'total enthalpy' conservation for compressible flow temperature calculation.

Birute June 13, 2003 08:22

Re: problems with compressible flow in turbine
 
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

Joern Beilke June 13, 2003 09:10

Re: problems with compressible flow in turbine
 
It is a bug in version 315 with the pressure work term.

You have to set "rcon 146 1"

CJ Tune June 14, 2003 09:59

Re: problems with compressible flow in turbine
 
Does this apply to all cases or just for compressible flow?

Joern Beilke June 14, 2003 15:34

Re: problems with compressible flow in turbine
 
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.

Jing June 20, 2003 04:32

Re: problems with compressible flow in turbine
 
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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