带诱导轮的离心泵空化条件下的效率下降规律

为定量研究空化对离心泵能量转换过程的影响,从流道内空泡分布和叶片载荷分布两方面探讨了离心泵效率下降的规律.基于RNG k-ε湍流方程和Rayleigh-Plesset空化模型对带诱导轮的离心泵的空化流动进行了数值模拟,获得了空化条件下影响离心泵效率下降的主要因素,包括扬程、功率及装置净正吸头等,并重点讨论了功率的变化对效率的影响.通过绘制叶片静压分布曲线分析离心泵效率及功率的变化趋势.结果表明：空化对叶片进口和叶片吸力面的压力影响很大;空化发展的过程中,功率的变化可分为3个过程,即功率下降段、功率上升段及迅速下降段;由于功率的下降没有扬程下降剧烈,泵总效率呈下降趋势;根据静压分布曲线及空泡分布图可以发现,叶片靠近后盖板的区域比靠近前盖板区域的空化严重,这也是叶片上不同位置处载荷差异的原因.

Efficiency degrade law under cavitation conditions of centrifugal pump with inducer

The main factors that cause pump efficiency degradation under cavitation conditions were discussed,which could be mainly associated with a decrease of the head,power and NPSHA.The change of power was discussed in detail that the calculated power could be divided into three parts with the reduction of inlet total pressure.When NPSHA becomes small,a cavity develops along the blade suction side,which reduces the suction ability near the blade leading edge but does not significantly change the pressure distribution along the pressure surface,and therefore reduces the blade loading.The cavities appear to attach to blade and induce a better blade loading at smaller NPSHA,and consequently the power of the pump increases.At severe cavitation conditions,the computed power degrades,which is contributed to the development of cavitating structures and a lower blade loading.The vapor volume distribution on the impeller indicates that the vapor first appears at the suction side of blade and then extends to the outlet of impeller with the reduction of NPSHA,the cavitation phenomenon is more severe at the suction side of blade along the hub than that near the front shroud,which may be the reason of the difference of blade loading at different locations.