The active control effects for the rotating stall in centrifugal diffuser and the elucidation of the relation between flow structure and rotating stall

在对旋转失速约束进行主动控制时，如果可以指定旋转失速(预失速)发生的条件、场所和结构，则可以延迟对场所进行处理。在一种情况下，涡旋安装在下游扩散器中，另一种情况下没有安装涡旋。当安装涡旋时，通过预测舌部附近的流动成为旋转失速启动的触发器，进行了舌部附近的壁面静压测量(半导体压力传感器)。然而，关于旋转失速开始的知识并没有得到明确的了解。利用壁面静压测量、测速(热线风速仪)和粒子图像测速仪(PIV)对无涡旋情况下旋转失速的产生原因、结构和演化过程等进行了研究。结果显示了扩散器出口的逆流发展过程。从速度信号和压力信号的频率分析以及各信号标准差的变化可以看出，PIV观测到的逆流流量与产生旋转失速的流量基本一致。

When doing an active control for the rotating stall restraint, if the condition of the occurrence of the rotating stall (prestall), the place and the structure can be specified, it can be delayed in doing disposal to the place. The experiment was carried out in one case in which the scroll was installed in the diffuser downstream and in another case it was not installed.When the scroll was installed, the wall surface static pressure measurement ( the semiconductor pressure transducer ) near the tongue division was carried out from the prediction that the flow near the tongue division became a trigger in the rotating stall start. However, a knowledge concerning with the start of the rotating stall was not clearly obtained. The case in which there was no scroll was examined on cause of generation, structure and evolution process of rotating stall, etc. using wall surface static pressure measurement, velocity measurement ( hot-wire anemometer ) and PIV(Particle Image Velocimetry). As the result, the reverse flow developing from the diffuser exit was visualized. The flow rate of which the reverse flow was observed by PIV agreed almost with the flow rate in which it seemed to generate the rotating stall from the frequency analysis of the velocity and pressure signals and the change of standard deviation of each signal.