Active Stabilization of Compressor Instability and Surge in a Working Engine

Abstract

We have applied feedback control to the compressor of a 45kW auxiliary power unit. Using this, the engine is able to deliver more than 10% extra shaft power before surge occurs. We achieve control by suppressing a non-axisymmetric flow phenomenon in the diffuser of the centrifugal compressor. Control is effected by modulating a small extra air flow into the impeller. We present results of modelling and analysis which suggest that linear feedback control will be sufficient to stabilize a compression system, even when both axisymmetric surge and rotating stall are present as possible instabilities.