Investigating the Influence of the Inlet Bypass Recirculation System on the Compressor Performance

In the present study, an experimental method is proposed to study the influence of different slot widths, positions and structures of the compressor recirculation systems on the compressor performance. Obtained results indicate that the compressor flow range increases with the width of the recirculation slot at the expense of a narrower high-efficiency operating region. It is found that when the slot width is set to 3 mm, the surge and choke margins are about 12% higher than that of the 2 mm slot. Moreover, it is found that when the position of the recirculation slot falls in the middle area of the guide wheel and far from the splitter blades, a larger surge margin can be achieved then it near the splitter blade. Adopting the recirculation structure without intake retaining ring structure can effectively broaden the compressor flow range. Compared with a straight slot intake structure, the compressor with an inclined slot intake structure has a greater surge margin in the high-speed region; however, the high-efficiency range of the latter scheme is smaller. Furthermore, the efficiency circle moves towards higher mass flow conditions. The present parametric study is expected to provide a guideline to design recirculation devices.