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 arunraj August 9, 2011 18:37

Regarding STALL POINT

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hiii,

i am doing simulation on a geometry similar to rotor 37... i m attached the domain for my simulation,...the design speed for the fan is 2400 rpm and mass flow rate = 3.5 kg...but i have to do simulation at off design value of 1800 rpm at various mass flow rate like (2, 2.5,1.5,1) ... i have done all these things...but now i want to find the stall point for the each case of my geometry and also i have to plot graph between pressure ratio vs mass flow rate..i don't get an idea how to capture stall for my geometry and also how to find the pressure ratios for each case..

Hi Arun,
I guess you should start reducing your mass flow rate at a particular RPM by extreme percentages like one sim at x kg/s and another at 0.3x and check if press rise is higher or lower at 0.3x; if lower it is in stalled region. now you can start approaching towards stallpoint.

If your point is near stall or in stalled region, your convergence becomes difficult and you need to take steps like mesh refinement and running with upwind and BF schemes. So you can get an idea at the time of running the simulation as to where is the solution headed.

Other way is to do a literature search and see at what mass flows do similar blades stall at , and try simulating that operating point and approach towards atll point. Arriving at stall point takes some effort and computational time. I think second method would be helpful in reducing your iterations.

-Dinesh

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