Stall and Recovery Process of a Transonic Fan with and without Inlet Distortion

The aim of this research is to study the stall and recovery behavior of a transonic fan stage with and without inlet distortion. For this purpose, simulations of the stall and recovery process of NASA stage 67 are performed with clean and distorted inflow conditions. The rotor is pushed into stall by closing the exit nozzle. It is shown that in both cases, stall is initiated via spike but the subsequent development of the stall differs. In the stable rotating stall, both cases contain one stall cell traveling at 63% shaft speed. During the recovery process, when the exit nozzle is gradually opened, the size of this stall cell reduces as the corrected mass flow increases. Although the fan stalls at a larger mass flow with inlet distortion, it recovers to a similar corrected mass flow as the case with clean inflow, which indicates that inlet distortion has minor effects on the recovery process for this blade. In spite of the lack of data, detailed analysis based on past experience and physical reasoning is used to demonstrate the validity on numerical simulations. The author appreciates that a validated computational fluid dynamics (CFD) study can provide instructive results to other researchers.