Cavitation characteristics of multiphase pump at low flow rate
LIU Xiaobing1,2, HU Quanyou1, SHI Guangtai1,2, ZHAO Qin1,2
1.School of Energy and Power Engineering, Xihua University, Chengdu, Sichuan 610039, China; 2.Key Laboratory of Fluid and Power Machinery, Ministry of Education, Xihua University, Chengdu, Sichuan 610039, China
Abstract:The hydraulic performance of multiphase pump is poor at low flow rate. To improve its performance, the cavitating flow field in a multiphase pump was simulated numerically under low flow rate conditions by using the homogenous multiphase flow model, Rayleigh-Plesset equation and standard k-ε two-equation turbulence model. The transport properties of the pump were analyzed under several typical cavitation conditions and the distribution features of cavitation bubbles in the impeller were clarified. The head and efficiency curves of the pump were predicated and compared with the experimental results, validating the reliability of simulation results to some extent. The results showed that the flow around the blade leading edge and the rotor-stator interaction had a great influence on flow separation in the impeller at a low flow rate, and the low pressure zone formed with vortices could aggravate inlet cavitation and reduce the performance of the pump. Cavitation was generated at the blade leading edge near the blade mid-span at first. Then the cavitation got worse on the blade suction side near the leading edge, the closer to the hub, the worse the cavitation. The cavity on the blade suction side could even block the impeller flow passages and intensify the phase separation of flow in the impeller. These results provide a theoretical basis for design optimization, performance improvement and further experimental study on multiphase pumps.
[1]NABHANI N.Potential application of multiphase pumps in oil and gas exploration and production[J].International proceedings of chemical biological & environment,2012,32:84-88.[2]HUA G,FALCONE G,TEODORIU C,et al.Comparisonof multiphase pumping technologies for subsea and downhole applications[J].Oil & gas facilities,2011,1(1):36-46.[3]ZHANG J,CAI S,LI Y,et al.Visualization study of gas-liquid two-phase flow patterns inside a three-stage rotodynamic multiphase pump[J]. Experimental thermal & fluid science,2016,70:125-138.[4]卢家兴,袁寿其,任旭东,等.离心泵小流量工况不稳定空化特性研究[J]. 农业机械学报,2015,46(8):54-58. LU Jiaxing,YUAN Shouqi,REN Xudong,et al.Investigation of instabilities of cavitation at low flow rate of centrifugal pump[J].Transactions of CSAM,2015,46(8):54-58.(in Chinese)[5]CHEAH K W,LEE T S,WINOTO S H,et al.Numerical flow simulation in a centrifugal pump at design and off-design conditions[J].International journal of rotating machinery,2007:83641.[6]TAN L,ZHU B S,CAO S L,et al.Cavitationflow simulation for a centrifugal pump at a low flow rate[J].Chinese science bulletin,2013,58(8):949-952.[7]苗长山,李增亮,李继杰.混输泵扬程与流量特性曲线的理论分析[J].石油学报,2007,28(3):145-148. MIAO Changshan,LI Zengliang,LI Jijie.Theoretical analysis on head-flow rate curves of multiphase pump[J].Acta petrolei sinica,2007,28(3):145-148.(in Chinese)[8]李清平,薛敦松,朱宏武,等.螺旋轴流式多相泵的设计与实验研究[J].工程热物理学报,2005,26(1):84-87. LI Qingping,XUE Dunsong,ZHU Hongwu,et al. Research on hydraulic design concept of an helicon-axial multiphase pump and its experimental studies on performances [J].Journal of engineering thermophysics,2005,26(1):84-87.(in Chinese)[9]李雪琴,王君,赵鹏,等.多相混输泵内气液两相分布的随机分形模型[J].广西大学学报(自然科学版),2010,35(5):756-761. LI Xueqin,WANG Jun,ZHAO Peng,et al.A random fractal model of gas-liquid distribution in multiphase pump[J].Journal of Guangxi University(natural science edition),2010,35(5):756-761.(in Chinese)[10]ZHANG Jinya,CAI Shujie,ZHU Hongwu,et al.Experimental investigation of the flow at the entrance of a rotodynamic multiphase pump by visualization[J].Journal of petroleum science and engineering,2015,126:254-261.[11]YU Z Y,ZHANG Q Z,HUANG R,et al.Numerical analysis of gas-liquid mixed transport process in a multiphase rotodynamic pump[C]//Proceedings of the 26th IAHR Symposium on Hydraulic Machinery and Systems, 2012.[12]余志毅,刘影.叶片式混输泵气液两相非定常流动特性分析[J].农业机械学报,2013,44(5):66-69. YU Zhiyi,LIU Ying.Characteristic analysis of unsteady gas-liquid two-phase flow in a multiphase rotodynamic pump[J].Transactions of the CSAM,2013,44(5):66-69.(in Chinese)[13]唐辰,周新,刘广兵,等.水温对离心泵汽蚀影响的试验验证及测试系统的改进[J]. 流体机械, 2016, 44(1):11-13,70. TANG Chen,ZHOU Xin,LIU Guangbing,et al. Experimental verification of theinfluence of water temperature on the cavitation of centrifugal pump and the improvement of cavitation test[J]. Fluid machinery, 2016, 44(1):11-13,70.(in Chinese)[14]何志霞, 张鑫, 陈驭航,等. 单孔孔板水力空化特性的可视化与数值模拟[J]. 江苏大学学报(自然科学版), 2017, 38(4):416-422. HE Zhixia,ZHANG Xin,CHEN Yuhang,et al.Visualization and numerical simulation of hydrodynamic cavitation in single hole orifice plate[J]. Journal of Jiangsu University(nature science edition), 2017, 38(4):416-422.(in Chinese)[15]马希金,王宏亮,赵学.轴流式油气混熟泵压缩机流场CFD模拟分析[J].农业机械学报,2006,37(2):41-44. MA Xijin,WANG Hongliang,ZHAO Xue.CFD numerical simulation of flow in the stage of axial gas-oil multiphase pump[J].Transactions of the CSAM,2006,37(2):41-44.(in Chinese)