Active Control of Rotating Stall by use of Swirl Breaker

无叶扩压器或有叶扩压器中的旋转失速不仅使泵、风扇和压缩机的稳定工作范围非常狭窄，而且会对轴承造成严重损害，因此迄今为止已经进行了许多研究，并且长期以来一直在寻求抑制这种不稳定现象的方法。然而，迄今为止提出的大多数方法需要复杂的机构，从而降低了机器人的整体效率。为了被动地控制和抑制无叶扩压器和有叶扩压器中的旋转失速，本文提出了一种新的径向浅槽装置，并对其效果进行了实验和理论研究。结果表明，在无叶扩压器和有叶扩压器中，3mm深的径向槽在几乎所有流量范围内都能完全抑制旋转失速。两侧壁上仅1 mm深的径向槽也能抑制旋转失速，理论分析表明，径向槽的这些巨大作用是由两种机制引起的：一是由于主流与槽流的混合而使切向速度显著降低，二是由于槽内的反向流动而使径向速度显著增加。

Rotating stall in a vaneless or a vaned diffuser not only makes the stably operating range of pumps, fans and compressors very narrow, but also gives severe damages to bearings, and thus many studies have been performed so far and the method has long been pursued to suppress this unstable phenomena. However, most of the methods so far proposed need complicated mechanisms, and thus reduce overall efficiency of a turbomachine. It is still strongly required to find a simple method of suppressing a rotating stall.In order to passively control and suppress a rotating stall in a vaneless diffuser and in a vaned diffuser, a new device by use of radial shallow grooves is proposed and its effect is studied experimentally and theoretically. The results show that the radial grooves of 3 mm depth suppress a rotating stall completely in a vaneless and a vaned diffusers over almost all flow range. The radial grooves of only 1 mm depth on both sidewalls can also suppress a rotating stall.Theoretical considerations have revealed that these tremendous effects of radial grooves are caused by two mechanisms ; one is a remarkable decrease of tangential velocity due to the mixing between the main flow and the groove flow, and the other is a remarkable increase of radial velocity due to the reverse flow in the grooves.