基于平衡孔偏移的离心泵空化性能改善研究

为了改善离心泵的空化性能,提出将平衡孔位置移至靠近叶片背面的方法。采用RNG k-ε湍流模型和Zwart-Gerber-Belamri空化模型,对不同空化数下平衡孔偏移前后的模型空化流场进行了数值计算与分析,结果表明:与原模型泵试验值相比,平衡孔偏移后,扬程、效率均有所下降,扬程降低幅度在4%之内,效率降低幅度在5%以内;在1.2Qe、Qe及0.8Qe流量下,平衡孔偏移后临界空化数均有所降低。平衡孔偏移改变了叶片背面静压低压区的分布,降低了叶片背面低压区流速,同时降低了流道内湍动能,提高了离心泵的空化性能;平衡孔偏移可以有效减小流道内空泡体积分数,改善叶轮流道内的流动条件,减弱空泡对流道的堵塞程度;平衡孔偏移后在一定程度上减小了轴向力,改善了离心泵受力状态。

Improvement of Cavitation Characteristics of Centrifugal Pump by Balanced Hole Offset

Cavitation is a physical phenomenon of centrifugal pump internal flow,during the operation of centrifugal pump,cavitation will directly lead to deterioration of hydraulic performance,and it seriously affects the safety and stability of the pump system.Therefore,it is of great significance to seek ways to improve the cavitation performance of centrifugal pump for safe and stable operation of centrifugal pump system.In order to further improve the cavitation characteristics of centrifugal pump,a method to suppress cavitation by moving the balance hole to the back of blade was proposed.According to the characteristics of centrifugal pump cavitation flow field,based on RNG k-εturbulence model and ZwartGerberBelamri cavitation model,the cavitation flow field with different cavitation numbers in the model before and after balance hole offset was calculated and analyzed.The results showed that compared with the experimental values of the original model,the head was decreased within 4%and the efficiency was decreased within 5%after balance hole offset.The critical cavitation number was decreased after the balance hole offset at flow rates of 1.2Qe,Qe and 0.8Qe.After the offset of balance hole,the distribution of static pressure zone on the back of the blade was changed.And the velocity in the low-pressure area on the back of the blade was reduced,at the same time,the turbulent kinetic energy in the flow passage can be effectively improved and it can inhibit the cavitation at all stages.Balanced hole offset can effectively reduce the volume fraction of the flow passage,improve the flow condition in impeller runner and reduce the blockage of flow passage by cavitation.The bubble volume in impeller was decreasesd obviously after balance hole offset and the fluctuation amplitude was decreased in a rotation period.The axial force was reduced and the mechanical condition of centrifugal pump was improved.