Influence of annular groove position on cavitation performance of high-speed inducer
CHENG Xiaorui1,2*, YANG Dengfeng1, LIU Mingjian1
1. College of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China; 2. Key Laboratory of Fluid Machinery and Systems, Gansu Province, Lanzhou, Gansu 730050, China
摘要 为抑制由高速诱导轮叶顶间隙泄漏涡引起的空化,在高速诱导轮上游和下游设立能吸纳泄漏涡的结构(即环形槽),并设计了5种环形槽方案,通过试验及数值计算相结合的方法研究不同环形槽方案对空化的抑制机理.研究发现:空泡最先出现在诱导轮吸力面进口边与轮缘相交的位置,随着管道进口压力的不断降低,空泡会不断向诱导轮流道内发展,进而漫延至离心叶轮叶片背面;环形槽能有效抑制间隙泄漏涡空化、不对称涡空化和旋转涡空化现象的发生,并在几乎不影响离心泵扬程及效率的情况下,提高离心叶轮的入口压力和离心泵扬程,有效地改善其空化性能;但同时发现,当环形槽位于诱导轮下游即轴向距离L3=-10.0 mm和L4=-12.5 mm时,会干涉诱导轮流道内流体的流动状态,影响诱导轮做功和能量交换,即环形槽在与诱导轮匹配时,两者有最佳轴向位置,此时环形槽与诱导轮的轴向距离L1=2.5 mm.
Abstract:In order to suppress the cavitation instability caused by tip clearance leakage vortex of the high-speed inducer, a structure(that is, an annular groove)that can absorb the leakage vortex on the upstream and downstream of the high-speed inducer was set up, and 5 kinds of annular groove schemes were designed, the inhibition mechanism of cavitation by different annular groove schemes was studied by means of experiment and numerical calculation. The study finds that the cavitation first appears at the position where the leading edge of the suction surface of the inducer intersects the shroud, as the pressure at the inlet of the pipeline continues to decrease, the cavitation will continue to develop into the inducer passage and then spreads to the back of the centrifugal impeller blade, the annular groove can effectively inhibit the occurrence of clearance leakage vortex cavitation, asymmetric vortex cavita-tion and rotating vortex cavitation. The inlet pressure and the head of the centrifugal impeller are improved almost without affecting the efficiency and the head, the cavitation performance of the centrifu-gal pump is improved effectively. But at the same time, it is found that when the axial distance between the annular groove and the inducer is L3=-10.0 mm and L4=-12.5 mm, it will interfere with the flow state of the fluid in the inducer, affecting the work and energy exchange of the inducer, that is, when the annular groove is matched with the inducer, there is the best axial position between the two. At this time, the axial distance between the annular groove and the inducer is L1=2.5 mm.