A Study of Sirocco Fan with Eccentric Inlet Nozzle

本文介绍了一种偏心进气喷嘴的热风风机的性能。实验研究了进口喷嘴偏心位置对风机压力系数和内部流量的影响。研究发现，当偏心位置位于涡旋出口较上游时，压力系数明显高于无偏心位置时。在这种偏心风机中，形成了从叶轮出口到进口通过叶冠间隙的循环流动。由于循环流动阻塞了进入叶轮入口的吸力流，使得叶栅的有效流动区域变窄。因此，通过叶栅的流速增大，所做功增大，因此风机的总压力增大。当涡旋中的一些流体通过防护罩间隙循环时，流入出口管道的剩余流体突然膨胀。因此，在涡旋中获得了较大的静压恢复。

This report describes the performance of a scirocco fan with eccentric inlet nozzle. The effects of the eccentric position of the inlet nozzle on the pressure coefficient and internal flow of the fan are experimentally investigated for many kinds of impellers and casings. It is found that, in case that the eccentric position is located far upstream of scroll exit, the pressure coefficient is considerably higher than that without eccentricirty. In this eccentric fan a circulating flow through shroud clearance from the impeller outlet to inlet is formed. As the circulating flow blocks the suction flow entering into impeller inlet, the effective flow region of the cascade is narrowed. Therefore the flow velocity through the cascades increases and the work done by it increases, so the total pressure of the fan increases. As some fluid in the scroll circulates through shroud clearance, the remaining fluid, which flows into an exit duct, suddenly expands. Therefore a large static pressure recovery is obtained in the scroll.