Dear Sir I am facing problem when i am analysing the casing with complete impeller passage the results we are getting is within the range. But the same problem when analysed using the same casing with single blade passage the results are not matching. Can anybody please tell why this difference is there and suggest some solution. Regards

Pankaj Bid

hi

Is the casing a volute type casing?

henry

hi! i am also doing a similar project, but mine's got outlet guide vanes. did you check the flowrate? but the way, did you use turbogrid to generate your grid.

Hi Henry The Casing is volute type Regards Pankaj N Bid

Yes I have used Turbogrid to generate the grid

Regards

Pankaj N Bid

hi

What is happening in any case is that when you do a complete analysis on the compressor model the flow is well predicted and result is restricted by the grid and the solver,but when you use a single blade placed within periodic boundaries you are assuming that the flow is periodic but even common sense tells us it is not so.but then it is still a good approximation in CFD, So what you need to model is both the the impellor and the diffuser.

And above all, postprocessing is very important,where are you doing the postprocessing ,I mean where at the exit,do you have an extended exit? or it it too close to the exit of the blade

So you can first do a post processing test at different spacings from the blade tip to the exit and calculate the efficiency and then take the one with the highest efficiency,and this is usually just outside the blade Trailing edge wake area.

hope this helps.

Henry