进气回流机匣处理离心压气机的扩稳机理

Numerical Analysis of Stall Improving Mechanism of a Centrifugal Compressor with Inlet Recirculation Casing Treatment

车用增压器的离心压气机在高转速下,往往暴露出流量过窄的问题.通过数值分析,对实壁机匣离心压气机模型高转速下的失速机理进行了研究,结果发现,转速下叶顶区域的流动变为跨音速流动,小流量下槽道激波前移至分流叶片之前,由于采用了长短叶片导致该处叶片稠度较小,间隙泄漏气流跨过激波后扰动迅速扩大,并诱发大量低能流体的堆积,促使压气机过早失稳.同时,对具有扩稳能力的进气回流机匣处理模型也进行了数值模拟,并与试验数据进行了对比验证,结果表明,布置在激波过后的回流槽能有效带走堆积在导风轮尾部附近的低能流体,减少了泄漏二次流对主流的扰动程度,使得气流以较小的攻角流过短叶片前缘,大大改善了叶轮内部流场.

Narrow flow range occurs in centrifugal compressor of turbocharger at high speed. In this study, the stall mechanism of a centrifugal compressor with smooth untreated casing was investigated numerically. Results show that the flow in the blade tip region is the transonic flow and channel shock wave moves ahead of the splitter blade. As low solidity of blades with splitter, once it flows past the shock wave, disturbance of tip clearance leakage will rapidly expand, inducing the substantial accumula- tion of low energy fluid and leads to unstable working condition. Meanwhile, numerical study of inlet recirculation casing treatment compressor was carried out and comparison and validation was made using the experimental data. Results show that reflux groove disposed after the shock can effectively bring away low energy fluid accumulation in the tail of air guide, reducing the disturbance extent of tip clearance leakage, leading the airflow to pass the leading edge of the splitter blade with a small incidence and greatlv imoroves internal flow structure of the imneller.