Enhancement of Centrifugal Compressor Operating Range by Use of Inlet Fins

摘要

The operational points of a turbocharger compressor have a strong tendency to approach its surge conditions (stability limit) during an engine's acceleration period, particularly under low engine-speed conditions.Hence there are expectations for a method for shifting the stability limit on a compressor low-speed line toward a lower flow rate.Inlet recirculation is often observed in a centrifugal compressor with a vaneless diffuser near a surge and under low compressor-speed conditions.The reverse flow caused by the inlet recirculation grows in a compressor-inlet pipe in the upstream direction. Firstly, this paper discusses the effect of inlet recirculation on compressor characteristics by considering a 1-D model and the potential that the growth of inlet recirculation has shown for destabilizing compressor operations.Secondly, the flow in a compressor-inlet pipe of a turbocharger was shown using visualization techniques,namely,oil flow and PIV (Particle Image Velocimetry),confirming the existence of inlet recirculation in the tested compressor.Furthermore,the effect of small fins mounted in a compressor-inlet pipe on inlet recirculation and compressor characteristics under low-speed conditions was investigated.Small fins are called inlet fins in this paper.According to test results,inlet fins showed great promise in shifting the compressor stability limit toward a low flow rate during inlet recirculation.