Measurement of the performance of a single stage, high mach number, subsonic axial-flow compressor

Abstract

A subsonic compressor designea to operate at high Mach numbers was tested, the measured pressure ratio being 1.38 at 22 lb/sec/sq ft flow and about 89 per cent efficiency. This efficiency was maintained at 5 per cent overspeed, but at still higher speeds the efficiency fell noticeably. The measured performance differed from the design figures because of secondary flows which caused large radial gradients in temperature rise and pressure ratio. The presence of both radial temperature and pressure gradients together with secondary floWS made the accurate determination of the Compressor efficiency difficult--the method normally used giving an efficiency about 3 per cent lower than a more accurate method using results takenduring traversing after the stator. Whilst the low aspect ratio and non-uniform work addition of the present compressor accentuate these difficulties, they mtast exist to some extent in all single stage tests. To overcome this snag, it would seem desirable to install additional instrumentation for overall efficiency measurement some waydownstream from the compressor stator row, where the flow is more uniform.