No abstract

No abstract

A three-dimensional compressible Navier-Stokes code has been used to model the steady and unsteady ow eld within a low-speed centrifugal compressor con guration tested at NASA Lewis Research Center. Near-design conditions, the performance map, pressure eld, and the velocity eld were in good agreement with measured data. At off-design conditions, the calculations show that ow reversal rst occurs near the blade leading edge. If left unchecked, the reversed-ow region grows spatially and temporally. Injection of air upstream of the compressor face was found to modify the local ow near the blade leading edge and to suppress rotating stall and surge. Even a moderate amount of air, typically around 5% of the total mass ow rate, was suf cient to extend the useful operating range of the compressor. Nomenclature A= area F = inviscid ux vector Çm = mass ow rate n = unit normal vector P 0 = stagnation pressure p = static pressure q = state vector R = viscous ux vector R Inlet = leading-edge tip radius S = surface t = time t ¤ = time at instance of part-span stall U t = leading-edge tip velocity V = velocity vector V G = vector of grid velocities a , b = injection angles q = density Subscripts in = in ow property n = normal property out = out ow property 1 = far-eld property

No abstract

No abstract

No abstract

No abstract

No abstract