# doubt: turbine side analysis logic

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 March 17, 2009, 09:39 doubt: turbine side analysis logic #1 Member   jaikrishna Join Date: Mar 2009 Location: chennai Posts: 56 Rep Power: 10 in cfx i'm assign that(turbine domain- i'm analysing automotive turbocharger),it is a rotating domain with angular velocity of some rpm (ex: at 90000 rpm). my question is generally we donot know the turbine speed but we know the gas velocity or pressure and temperature at inlet. whether it is wrong or myself following the wrong method of assigning..

 March 17, 2009, 17:24 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,985 Rep Power: 107 Hi, The simple approach here is to guess a turbine speed, simulate it and check whether the output torque is correct. You then adjust the turbine speed until you get the correct output torque and that's you operating point. It is an iterative approach. A more complex approach is to link the output torque of the turbine to the speed so a single simulation "homes" into the correct output torque. This approach is cleaner and potentially more accurate but the implementation can be tricky - you will probably have to under-relaxation the turbine velocity changes or use some other form of numerical stability method to obtain convergence. I would recommend the first approach (the iterative approach) unless you are very confident in CFX and numerical methods. Glenn Horrocks

 March 18, 2009, 09:38 Re: turbine logic #3 Member   jaikrishna Join Date: Mar 2009 Location: chennai Posts: 56 Rep Power: 10 sir i'm not asking how to determine the correct speed of the turbine. if it's compressor means it is run by some kind of prime mover so we can able to guess the speed. but in turbine we donot know the speed. here we extract or convert the kinetic energy to mechanical energy. whether in CFX possible to assign the domain as rotating domain with out rotational speed. because it spin depends up on the inlet fluid's temperature and velocity..etc.

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