水泵水轮机制动工况内流特性分析
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摘要
为研究水泵水轮机在制动工况运行时内部流动特性,在确定的等开度线上选取具有代表性的制动工况点,对其进行了全流道数值计算.选用SST k-ω湍流模型,采用SIMPLEC耦合算法,对选定工况点的机组整体流动域内的三维复杂流态进行了分析.结果表明:机组进入制动工况后流态总体上呈现出不稳定状态,多伴有大尺度漩涡的产生.其中蜗壳及固定导叶内流动较为平稳,自活动导叶进口处出现小尺度漩涡,在转轮中流态不稳定达到极致,叶道间出现大尺度漩涡;转轮进出口流动虽以水轮机工况流动方向为主,但受转轮内大尺度旋涡及离心力影响,回流严重流动紊乱,流态转入反水泵工况的趋势明显;尾水管内流动呈现显著的螺旋态,从进口开始流动回旋紧贴壁面,直锥段出现大幅回流反向进入转轮区域.此工况机组整体流域的复杂流动势必加剧机组的振动,对其稳定运行造成极大的影响.
In order to study the characteristics of internal flow in pump-turbine on braking operation, a set of representative braking regime points was selected on a certain equal opening line to carry out numerical calculation of full flow passage of pump-turbine. By means of SST k-ω turbulent mode and SIMPLEC algorithm, the three-dimensional complex flow condition in integrate flow domain at those selected regime points was analyzed. The result showed that the flow condition of the unit on braking regime would exhibit as a whole an unstable state accompanied with occurrence of large-scale vortices. Among others, the flow in volute and stationary guide vanes would be more stable, but the small-scale vortices would appear at the inlet of movable guide vanes and go forth to make the flow condition instable to the utmost extent in the runner with large vortices in flow passage of blades. Although the main flow direction at runner inlet and outlet would be consistent with that on turbine regime, the backflow in there would be serious and the flow in there would be chaotic because of the impact of large-scale vortices and centrifugal force in the runner, so that the flow condition would tend to turn obviously into reverse pump regime. The flow in draft tube would exhibit a remarkable helical state, attaching closely to the wall of the draft tube from its inlet, and there in its conical segment would be a large-scale backflow returning back into the runner. The complex flow in the whole flow passage would necessarily exacerbate the vibration of the unit on this regime and have great impact on its stable operation.
In order to study the characteristics of internal flow in pump-turbine on braking operation, a set of representative braking regime points was selected on a certain equal opening line to carry out numerical calculation of full flow passage of pump-turbine. By means of SST k-ω turbulent mode and SIMPLEC algorithm, the three-dimensional complex flow condition in integrate flow domain at those selected regime points was analyzed. The result showed that the flow condition of the unit on braking regime would exhibit as a whole an unstable state accompanied with occurrence of large-scale vortices. Among others, the flow in volute and stationary guide vanes would be more stable, but the small-scale vortices would appear at the inlet of movable guide vanes and go forth to make the flow condition instable to the utmost extent in the runner with large vortices in flow passage of blades. Although the main flow direction at runner inlet and outlet would be consistent with that on turbine regime, the backflow in there would be serious and the flow in there would be chaotic because of the impact of large-scale vortices and centrifugal force in the runner, so that the flow condition would tend to turn obviously into reverse pump regime. The flow in draft tube would exhibit a remarkable helical state, attaching closely to the wall of the draft tube from its inlet, and there in its conical segment would be a large-scale backflow returning back into the runner. The complex flow in the whole flow passage would necessarily exacerbate the vibration of the unit on this regime and have great impact on its stable operation.
引文
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[16] 李琪飞,蒋雷,李仁年,等.水泵水轮机反水泵工况区压力脉动特性分析 [J].水利学报,2015,46(3):350-356.
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[2] NAKAMURA T,NISHIZAWA H,YASUDA M,et al.Study on high speed and high head reversible pump turbines [C]//18th International Association for Hydro-Environment Engineering and Research Symposium.Berlin:Springer,1996:210-219.
[3] ZUO Z,FAN H,LIU S,et al.S-shaped characteristics on the performance curves of pump-turbines in turbine mode [J].Renewable & Sustainable Energy Reviews,2016,60:836-851.
[4] HASMATUCHI V,FARHAT M,ROTH S,et al.Experimental evidence of rotating stall in a pump-turbine at off-design conditions in generating mode [J].Journal of Fluids Engineering,2011,133(5):623-635.
[5] 陈德新,谢辉.低比速水泵水轮机“S”特性区的内部流动 [J].水利学报,2001,32(2):76-78.
[6] 王玲花,高传昌,陈德新,等.水泵水轮机流动可视化图像解析系统的设计 [J].中国农村水利水电,2006(1):96-98.
[7] 尹俊连.水泵水轮机“S”区内流机理及优化设计研究 [D].杭州:浙江大学,2012.
[8] 王福军.流体机械旋转湍流计算模型研究进展 [J].农业机械学报,2016,47(2):1-14.
[9] 张兰金,王正伟,常近时.混流式水泵水轮机全特性曲线S形区流动特性 [J].农业机械学报,2011,42(1):39-43,73.
[10] 李琪飞,李仁年,韩伟,等.混流式水轮机引水、导水部件内部固液两相流动的数值分析 [J].兰州理工大学学报,2008,34(6):47-50.
[11] 阮辉,罗兴锜,廖伟丽,等.叶片低压边厚度对水泵水轮机空化性能与强度的影响 [J].农业工程学报,2015,31(15):32-39.
[12] 周佩剑,王福军,姚志峰.离心泵叶轮在旋转失速条件下压力脉动特性研究 [J].农业机械学报,2015,46(10):56-61.
[13] 唐狄毅,郭捷,李立君,等.旋转失速和喘振的统一模型 [J].工程热物理学报,1992,13(3):273-275.
[14] 张立翔,王文全,姚激.混流式水轮机转轮叶片流激振动分析 [J].工程力学,2007,24(8):143-150.
[15] 李琪飞,张毅鹏,敏政,等.变工况下贯流式水轮机叶片形变分析 [J].兰州理工大学学报,2015,41(2):61-64.
[16] 李琪飞,蒋雷,李仁年,等.水泵水轮机反水泵工况区压力脉动特性分析 [J].水利学报,2015,46(3):350-356.
[17] 郑源,汪宝罗,屈波.混流式水轮机压力脉动研究综述 [J].水力发电,2007,33(2):66-69.