不同吸水室对离心泵空化性能的影响分析

Influence of different suction chambers on the cavitation performance of centrifugal pumps

由于吸水室的几何形状决定了叶轮进口的速度分布,对泵空化性能具有重要的影响。针对一单级单吸离心泵配套的直锥形、半螺旋形、环形3种不同结构的吸水室,采用数值方法研究分析3种不同结构的吸水室内部流动变化对离心泵空化性能的影响。结果表明:直锥形吸水室相比于其他2种吸水室,对叶轮空化性能影响最小,初生空化发生在与蜗壳隔舌对应流道的下一个流道的叶轮叶片进口背面。半螺旋形吸水室出口速度增加且不均,液体以较高速度流入叶轮,使得对应径向位置的叶片进口背面首先发生初生空化。环形吸水室左右两侧内均产生漩涡与回流等现象,吸水室出口处靠近入口侧速度较大,使得叶轮叶片进口背面压力减小易于发生空化。在临界空化工况下,半螺旋吸水室与环形吸水室叶轮进口处产生的空泡在流道进口之间发生蔓延,其环形吸水室叶轮进口最为明显,对泵空化性能影响最大。该研究结果对泵叶轮进口流动设计和吸水室结构设计具有一定的理论价值。

Because the geometry of a suction chamber determines the velocity distribution of the impeller inlet, it has an important influence on the cavitation performance of pumps. Aiming at the straight-cone, semi-spiral, and circular suction chambers of a single-stage single-suction centrifugal pump, a numerical method is used to analyze the influence of flow changes in suction chambers with three different structures on the cavitation performance of a centrifugal pump. The results show that compared with the other two kinds of suction chambers, the straight-cone suction chamber has the least influence on the cavitation performance of the impeller, and incipient cavitation occurs at the back of the impeller blade inlet of the next channel corresponding to the volute tongue. The outlet velocity of the semi-spiral suction chamber increases and is uneven, and the liquid flows into the impeller at a higher speed, which makes the incipient cavitation first occur at the back of the blade inlet at the corresponding radial position. A vortex and backflow occur in both sides of the circular suction chamber, and the velocity near the inlet side of the suction chamber is high, which makes the pressure at the back of the impeller blade inlet decrease and the incipient cavitation easily occur. Under the critical cavitation condition, the cavitation generated at the impeller inlet of the semi-spiral suction chamber and the circular suction chamber spreads between the inlet of the flow passage and the impeller inlet of the circular suction chamber is the most obvious, which has the greatest impact on the cavitation performance of the pump. The research results have a certain theoretical value for the inlet flow design of pump impellers and the structural design of suction chambers.