气液两相条件下离心泵叶轮受力分析
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摘要
为了研究气液两相混输条件下离心泵叶轮做功原理及能量转换机理,基于欧拉双流体模型,以水和空气为工作介质,在不同初始含气率工况下,利用数值模拟软件CFX对离心泵内流场进行数值计算。结果表明:叶轮流道内气相主要分布在叶片背面及出口边附近;随着初始含气率的增加,气相将在叶片背面形成较为稳定的气泡团,出现严重的相态分离,造成叶轮内出现严重的漩涡、二次流和气塞现象,使离心泵水力损失增加,扬程急剧下降;叶片受到的动反力也逐渐降低,引起叶轮轴向力的加大;同时,含气率的升高加剧了叶轮周向上的不均匀流动,破坏了叶轮径向力的周期性变化。
In order to study the principle of work and the mechanism of the energy conversion of the impeller under gas-liquid two phase mixed transport condition,the numerical simulation software CFX is used to calculate the flow field in the centrifugal pump. The method is based on the Euler two-fluid model,with water and air as the working medium,under different inlet gas volume fraction conditions. The results show that the gas phase in the impeller flow channel is mainly distributed near the blade suction surface and the outlet section. With the increase of the inlet gas volume fraction,the gas phase will form a more stable bubble group on the back of the blade,and the phase separation will occur,resulting in vortex,secondary flow and gas plug in the impeller,which will increase the hydraulic loss of the centrifugal pump and decrease the head dramatically. At the same time,the increase of the inlet gas volume fraction causes the negative reaction force of the blade to be reduced and the axial force of the impeller increased. In addition,the increase in gas volume fraction exacerbates the uneven of gas-liquid two-phase in the impeller cycle,which destroys the periodic variation of the radial force of the impeller.
In order to study the principle of work and the mechanism of the energy conversion of the impeller under gas-liquid two phase mixed transport condition,the numerical simulation software CFX is used to calculate the flow field in the centrifugal pump. The method is based on the Euler two-fluid model,with water and air as the working medium,under different inlet gas volume fraction conditions. The results show that the gas phase in the impeller flow channel is mainly distributed near the blade suction surface and the outlet section. With the increase of the inlet gas volume fraction,the gas phase will form a more stable bubble group on the back of the blade,and the phase separation will occur,resulting in vortex,secondary flow and gas plug in the impeller,which will increase the hydraulic loss of the centrifugal pump and decrease the head dramatically. At the same time,the increase of the inlet gas volume fraction causes the negative reaction force of the blade to be reduced and the axial force of the impeller increased. In addition,the increase in gas volume fraction exacerbates the uneven of gas-liquid two-phase in the impeller cycle,which destroys the periodic variation of the radial force of the impeller.
引文
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[2]李红,徐德怀,涂琴.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 De-huai,TU Qin.Numerical simulation on gas-liquid two-phase flow of self-priming pump during starting period[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2013,29(3):77-83.
[3]李红,徐德怀,李磊.自吸泵自吸过程瞬态流动的数值模拟[J/OL].排灌机械工程学报,2013,31(7):565-569.LI Hong,XU De-huai,LI Lei.Numerical simulation of transient flow in self-priming centrifugal pump during self-priming period[J].Journal of Drainage and Irrigation Machinery Engineering,2013,31(7):565-569.
[4]卢金铃,席光,祁大同.离心泵叶轮内气液两相二维流动数值研究[J].工程热物理学报,2003,24(2):237-240.LU Jin-ling,XI Guang,QI Da-tong.Numerical study on the gasliquid two-phase 3-D flow in the impeller of a centrifugal pump[J].Journal of engineering thermophysics,2003,24(2):237-240.
[5]卢金铃,席光,祁大同.气液两相流泵的研究进展[J].流体机械,2001,29(12):1245.LU Jin-ling,XI Guang,QI Da-tong.Review of Research on gasliquid two-phase flow pumps[J].Fluid Machinery,2001,29(12):1245.
[6]袁建平,张克玉.基于非均相流模型的离心泵气液两相流动数值研究[J].农业机械学报,2017,48(1):89-95.YUAN Jian-ping,ZHANG Ke-yu.Numerical investigation of gasliquid two-phase flow in centrifugal pumps based on inhomogeneous model[J].Transactions of the Chinese Society for Agricultural Machinery,2017,48(1):89-95.
[7]余志毅,曹树良,王国玉.叶片泵气液两相流的三维流动数值模型[J].北京理工大学学报,2007,27(12):1057-1060-1064.YU Zhi-yi,CAO Shu-liang,WANG Guo-yu.A numerical model for 3-D gas-liquid two-phase flow in vane pumps[J].Trans Beijing Inst Technol,2007,27(12):1057-1060-1064.
[8]张金亚,朱宏武,徐丙贵.高含气率下增强叶轮内气液均匀混合的方法[J].排灌机械工程学报,2012,30(6):641-645.ZHANG Jin-ya,ZHU Hong-wu,XU Bing-gui.Methods for improving gas and liquid phases mixing in impeller with high gas void fraction[J].Journal of Drainage and Irrigation Machinery Engineering,2012,30(6):641-645.
[9]杨军虎,张玉鹤.气液两相介质时液力透平径向力分析[J].西华大学学报:自然科学版,2014,33(4):104-108.YANG Jun-hu,ZHANG Yu-he.Numerical simulation of hydraulic turbines working in the medium of gas liquid two-phase and analysis of the force performance[J].Journal of Xihua University:Natural Science,2014,33(4):104-108.
[10]施卫东,徐磊,王川.蜗壳式离心泵内部非定常数值计算与分析[J].农业机械学报,2014,45(3):49-53.SHI Wei-dong,XU Lei,WANG Chuan.Numerical calculation and analysis of inner unsteady flow for volute centrifugal pump[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(3):49-53.