摘要
基于熵产理论,研究原型水泵水轮机在泵模式不同流量工况下的水力损失空间分布及不稳定流动诱导的主要水力损失存在的位置和变化。结果表明:随着流量增加,总熵产与压差法水力损失变化一致,先显著减小后逐渐增大。间接熵产、直接熵产和壁面熵产与总熵产的变化趋势一致,且间接熵产和直接熵产占主导地位。间接熵产和直接熵产的分布与湍动能的分布基本一致,但直接熵产更靠近主涡区,而间接熵产在流场中具有更宽的分布范围。水泵水轮机流动区域内的水力损失位置强烈依赖于流动条件。小流量工况下高水力损失主要源于无叶区的高速环流、活动导叶区的旋涡以及尾水管弯肘段和直锥段的壁面分离,而蜗壳的水力损失较小。最优工况下的水力损失较小,主要源于叶片尾迹和少数固定导叶流道的旋涡。大流量工况下高水力损失主要源于水流对活动导叶的冲击和不稳定流动在固定导叶区的扩散,以及蜗壳进口处周向间隔分布的旋涡和高速流动,而尾水管的水力损失极小。
Energy is irrevocably lost within the pump-turbine due to the activities of viscous forces near the wall.The conventional pressure drop method can not get exact details of the hydraulic loss within the machine's flow passageways.On the other hand,the entropy production method has obvious advantages in hydraulic loss assessment and it can accurately identify precise information on the position of irreversible losses.The composition and distribution of hydraulic loss under different flow rate operating points was explored for a prototype pump-turbine in pump mode using the entropy production theory.The entropy production method was verified to be reasonable and credible within a certain error range by comparison with the pressure drop method.The total entropy production and total hydraulic loss obtained by the method of differential pressure were consistent with the variation.With an increase in flow rate,the total entropy production decreased dramatically initially and then gradually increases.The entropy production rate caused by turbulence dissipation,direct dissipation,and wall shear stress exhibited the same variation pattern as the total entropy production.The major flow region's entropy production was predominantly induced by flow separation,backflow,and vortex creation.Entropy production was prominent in the main flow zone,with the entropy production rate caused by turbulence dissipation contributing the most to the total entropy production(50%-61%)and the entropy production rate caused by direct dissipation coming in second(37%-48%).The entropy production in the near-wall region primarily originated from the significant velocity gradient triggered by the wall shear stress,which could be roughly equivalent to friction loss and made a negligible 1%-2%contribution to total entropy production.Under various flow rate conditions,the hydraulic loss in the runner,guide vanes and stay vanes were dominant(67%-86%).Under low flow rate conditions,hydraulic loss in the draft tube was greater.However,under high flow rate conditions,hydraulic loss in spiral casing was greater.The distributions of the entropy production rate caused by turbulence dissipation and the entropy production rate caused by direct dissipation were highly consistent with the distribution of turbulent kinetic energy.But the entropy production rate caused by direct dissipation was mainly caused by strain rate,so it was closer to the main vortex regions,whereas the entropy production rate caused by turbulence dissipation was affected by turbulence intensity and had a wider distribution range in the flow field.High hydraulic loss under low flow conditions mainly came from the high-speed circulation in the vaneless region,vortices in the guide vane flow channels,and the flow separation within the elbow and the conical part of the draft tube.But the spiral casing’s hydraulic loss was much lesser.Hydraulic loss under the best efficiency operating point was small and mainly due to vortices in some stay vane flow channels and the blade wake.High hydraulic loss under high flow conditions mainly came from flow impact on the guide vanes,diffusion of unstable flow in stay vane flow channels,and the circumferentially spaced vortices and high-speed flows at the spiral casing inlet;Whereas the draft tube’s hydraulic loss was rarely small.The total entropy production and total hydraulic loss decreased significantly and then slowly increased with an increase in flow rate.The entropy production rate caused by turbulence dissipation contributed the most to total entropy production(50%-61%),with direct dissipation coming in second(37%-48%),and wall shear stress coming in last(1%-2%).Under various flow rate conditions,the hydraulic loss in the runner,guide vanes and stay vanes were dominant(67%-86%).Hydraulic loss in the draft tube was larger at low flow rate conditions.While the hydraulic loss in spiral casing was greater under high flow rate conditions.The entropy production distributions were highly consistent with the distribution of turbulent kinetic energy.The entropy production rate caused by direct dissipation was closer to the main vortex regions,whereas turbulence dissipation had a wider distribution range in the flow field.The detailed location of hydraulic loss within the pump-turbine’s flow domain strongly depended on flow conditions.Under low flow conditions,hydraulic loss mainly came from the high-speed circulation in the vaneless region,vortices in the guide vane flow channels,and the flow separation within the elbow and the conical part of the draft tube.Under the best efficiency operating point,the hydraulic loss was small and mainly due to vortices in some stay vane flow channels and the blade wake.Under high flow conditions,hydraulic loss mainly came from flow impact on the guide vanes,diffusion of unstable flow in stay vane flow channels,and the circumferentially spaced vortices and high-speed flows at the spiral casing inlet.
作者
李东阔
桂中华
闫晓彤
郑源
阚阚
LI Dongkuo;GUI Zhonghua;YAN Xiaotong;ZHENG Yuan;KAN Kan(Pumped Storage Technological&Economic Research Institute of State Grid Xinyuan Company Ltd.,Beijing 100761,China;College of Energy and Electrical Engineering,Hohai University,Nanjing 211100,China)
出处
《南水北调与水利科技（中英文）》
CAS
CSCD
北大核心
2023年第2期390-398,共9页
South-to-North Water Transfers and Water Science & Technology
基金
国家自然科学基金项目(52009033)
国网新源控股有限公司科技项目(SGXYKJ-2022-044)
江苏省自然科学基金项目(BK20200509)
中国博士后科学基金项目(2022T150185,2022M711021)。
关键词
水泵水轮机
泵模式
熵产
工况
水力损失
pump-turbine
pump mode
entropy production
operating condition
hydraulic loss
作者简介
李东阔(1992-),男,河北石家庄人,工程师,主要从事抽蓄机组运行与稳定性研究。E-mail:919099225@qq.com;通信作者:郑源(1964-),男,山东日照人,教授,博士生导师,主要从事流体机械及工程研究。E-mail:zhengyuan@hhu.edu.cn。
