Dynamic Total Head Loss Characteristic for an Axial Compressor Rotor

Abstract

Detailed flow field and pressure measurements during rotating stall operation have been carried out at inlet to and exit from an axial compressor rotor using hot wire anemometers and probes incorporating fast response pressure transducers. An on-line data-acquisition system which employs a phase-lock sampling and averaging technique has been used to obtain ‘phase-lock averaged’ values of flow quantities and pressures. The dynamic total head loss/incidence characteristic for the rotor section at mean diameter has been computed from the above data. The dynamic characteristic exhibits a loop in the stalled region. A simple numerical procedure has been used to obtain the steady-state loss characteristic and the time-lag of this loss. It has been found that the loss time-lag of boundary layer time delay corresponds to a value equal to 1.8 times the time delay due to inertia of fluid in a blade passage. A simple theory for the prediction of this loss time-lag is also presented which shows reasonable agreement with the value determined from measurements.