1. School 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
Abstract:Experiments on suction and hydraulic characteristics were performed at different installation heights in a fluid flow testing system built to investigate self-priming mechanisms in jet centrifugal self-priming pumps in term of the type JET750G1jet centrifugal pump. Also, a series of numerical simulations of cavitating flows in the pump were carried out based on the K-ω turbulence model and Zwart-Gerber-Belamri cavitation model at zero installation height. The experimental results show that the head, shaft-power and efficiency curves drop sharply when the flow rate reaches a certain value; as the installation height increases, however, the flow rate at the point for performance to start to drop steeply gets lowed. The numerical results exhibit that the predicted head, shaft-power and efficiency are basically consistent with experimental values, and the estimated flow rate for performance to start to drop steeply is 0.5 m3/h larger than the experimental value. Because of a smaller area ratio in the jet nozzle, the primed fluid shear layer is rapidly dragged to the wall of the throat, and the lowest pressure appears just after the throat outlet where cavitation inception occurs. As the flow rate increases, the cavities extend rapidly to the eye of impeller. The flow rate at the point for performance to start to drop steeply is exactly the flow rate for cavitation inception in the pump. Thus, the suction performance of a jet centrifugal pump depends on that of the ejector. An ejector can improve the head and self-priming performance of a centrifugal pump, but the high velocity reverse flow and strong shear flow in the ejector will lead to a significant drop in pump efficiency and suction performance.
[1]刘建瑞, 周贵平. 射流式自吸喷灌泵的研究进展与展望[J]. 农业机械学报, 2007, 38(8): 177-180. LIU Jianrui, ZHOU Guiping. Reserch and prospects for the self-priming irrigation pumps[J]. Transactions of the CSAM, 2007, 38(8): 177-180.(in Chinese)[2]王海艳,刘纪新,于晓,等.新型孔式环形射流泵的结构设计及仿真分析[J].煤炭技术,2019,38(1):160-163. WANG Haiyan, LIU Jixin, YU Xiao,et al. Structure design and simulation analysis of new-type perforated annular jet pump[J]. Coal technology,2019,38(1):160-163.(in Chinese)[3]FAN J, EVES J, THOMPSON H M, et al. Computa-tional fluid dynamic analysis and design optimization of jet pums[J]. Computers & fluids, 2011(46): 212-217.[4]李贵东, 王洋, 杨学明, 等. 基于大涡模拟的射流式离心泵射流器内部的流动特性[J]. 排灌机械工程学报, 2017, 35(5): 369-374. LI Guidong, WANG Yang, YANG Xueming, et al. Features of internal flow in jet nozzle of self-priming centrifugal pump based on large eddy simulation [J]. Journal of drainage and irrigation machinery engineering, 2017, 35(5): 369-374.(in Chinese)[5]李贵东, 王洋, 曹璞钰, 等. 射流式离心泵非设计工况下内部流动研究[J]. 农业机械学报, 2015, 46(8): 48-53. LI Guidong, WANG Yang, CAO Puyu, et al. Internal flow of flow-ejection centrifugal pump under off-design conditions[J]. Transactions of the CSAM, 2015, 46(8): 48-53.(in Chinese)[6]王洋, 韩亚文, 朱新新, 等. 基于CFD的射流自吸泵性能优化与试验[J]. 农业工程学报, 2016, 32(S2): 16-21. WANG Yang, HAN Yawen, ZHU Xinxin, et al. Optimization and experiment on performance of flow-ejecting self-priming pump based on CFD[J]. Transactions of the CSAE, 2016, 32(S2): 16-21.(in Chinese)[7]刘建瑞, 文海罡, 高振军, 等. 射流喷嘴几何参数对喷灌泵自吸性能的影响[J]. 农业工程学报, 2012, 28(24): 47-54. LIU Jianrui, WEN Haigang, GAO Zhenjun, et al. Effects of geometric parameters for jet nozzle on self-priming performance of spray pump[J]. Transactions of the CSAE, 2012, 28(24): 47-54.(in Chinese)[8]周英环, 袁寿其, 刘建瑞, 等. 新型射流式喷灌自吸泵的水力设计与对比试验研究[J]. 中国农村水利水电, 2009(4):62-68. ZHOU Yinghuan,YUAN Shouqi,LIU Jianrui, et al. Hydraulic design and experimental reserch on the new self-priming sprinkler irrigation jet pump[J]. China pural water and hydropower, 2009(4):62-68.(in Chinese)[9]李红, 徐德怀, 涂琴, 等. 自吸泵启动过程气液两相流动的数值模拟[J]. 农业工程学报, 2013, 29(3): 77-83. LI Hong, XU Dehuai, TU Qin, et al. Numerical simulation on gas-liquid two-phase of self-priming pump during starting period[J]. Transactions of the CSAE, 2013, 29(3): 77-83.(in Chinese)[10]李晓俊. 离心泵叶片前缘空化非定常流动机理及及动力学特性研究[D]. 镇江:江苏大学, 2013. [11]ABDULAZIZ A M. Performance and image analysis of a cavitating process in a small type Venturi[J]. Experimental thermal and fluid science, 2014(53): 40-48.