低比转速离心泵叶轮瞬态空化特性分析  

Transient characteristics of cavitation in low specific speed centrifugal pumps

作　　者：吴登昊[1,2] 吴振兴[1] 周佩剑[1] 牟介刚[1] 谷云庆[1] 陈莹[1] WU Denghao;WU Zhenxing;ZHOU Peijian;MOU Jiegang;GU Yunqing;CHEN Ying(College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014;Zhijiang College, Zhejiang University of Technology, Hangzhou 310024)

机构地区：[1]浙江工业大学机械工程学院,杭州310014 [2]浙江工业大学之江学院,杭州310024

出　　处：《水力发电学报》2018年第3期96-105,共10页Journal of Hydroelectric Engineering

基　　金：国家自然科学基金(51609212;51709234)

摘　　要：低比转速离心泵叶轮流道宽度较小且较为狭长,流道进口容易被空化状态下的空泡堵塞,诱发严重的振动和噪声,不利于机组安全稳定运行。针对比转速为45的离心泵,采用RNG k-ε湍流模型与Zwart-Gerber-Belamri空化模型,对不同工况下的非定常空化流场进行模拟计算,准确预测了不同工况下的空化余量-扬程曲线,并得到空化初生位置与空泡的时空演变和径向力变化。计算结果表明,不同工况下由空化产生空泡的非定常特性也有所不同。在小流量(0.8Qd)工况下发现,NPSH=4.75 m时在一个叶轮旋转周期内各个流道的空泡区变化规律明显,空泡区变化表现为收缩、稳定、再生长;NPSH=3.61 m时空区泡的变化规律为5个叶轮旋转周期,叶片上的空泡区经历稳定—分离—生长—局部脱落周而复始的过程。在设计工况(1.0Qd)下,叶轮中的空泡分布相对均匀,而大流量(1.2Qd)工况下空泡的分布并不对称,出现了交替堵塞的现象。未发生空化时,叶轮径向力分布呈规则的五角星状,随空化发展,叶轮内非对称分布的空泡区致使径向力分布紊乱。Cavitation bubbles are easy to block the long, narrow inlet passage of a low specific speed centrifugal pump and always induce severe noise and vibration, thus imposing significant influence on its operational safety and stability. In this study, unsteady cavitating flows in a centrifugal pump at a specific speed of 45 are simulated using a RNG k-ε turbulence model and a Zwart-Gerber-Belamri cavitation model. We have well predicted the NPSH-head curves of the pump in various working conditions with a good agreement with the experimental results and obtained the full flow fields and the characteristics of unsteady cavitation bubbles in the pump. Results show that these bubbles behavior differently in different pump working conditions. At a low flow rate （0.8Qd）, cavitation bubbles in each impellor passage show an obviously periodic cycle, which is characterized by three stages of shrink, stabilization and expansion at NPSH = 4.75 m, while by four stages of stabilization, split, growth and shrink at NPSH = 3.61 m. At the rated flow （1.0Qd） cavitation bubbles in the impellor passages are relatively periodic and uniformly distributed, while at a larger flow rate （1.2Qd） they are nonuniform showing an alternative passage blocking phenomenon. As the flow rate is increasing, the radial force on the impeller is distributed in a regular five-pointed star shape until cavitation is started, and along with the development of cavitation it develops into disordered patterns owing to the asymmetrical distribution of cavitation spots over the impeller.

关 键 词：离心泵 低比转速 径向力 空化 非定常数值计算 

分 类 号：TH311[机械工程—机械制造及自动化]