尾水管深度对轴流定桨式水轮机性能的影响
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摘要
尾水管深度对水轮机的效率及稳定性都有重要影响。为解决某电站水轮机效率及出力不足的问题,采用数值模拟的方法,分析了尾水管深度变化对水轮机性能的影响。通过几个不同尾水管加深方案的比较分析,得出尾水管深度在一定范围内增加能有效提高尾水管回能系数,降低扩散损失。但由于沿程摩擦损失会随深度增加而增大,因而综合考虑损失、效率及经济性因素,最终选定尾水管深度为3.0D1的尾水管深度方案。同时,为保证水轮机的运行稳定性,也比较了该方案对流场稳定性的影响,分析了湍动能及脉动的变化。结果表明尾水管与转轮内流场存在相互作用,直锥段加高后不但会降低直锥段出口的湍动能,也会减轻转轮出口的湍动能。即尾水管内流动的改善也会降低转轮出口附近流场的紊乱程度,显著降低了转轮所受到的径向力及压力脉动峰峰值,提升了转轮内流场的稳定性。此外尾水管深度改变方案对转轮空化性能的影响不大,转轮叶片背面的最低压力范围基本没有变化。
The performance of draft tube plays an important role in the efficiency and stability of hydraulic turbine. To improve the hydraulic performance of an axial flow fixed-blade hydro-turbine,the depth of draft tube was studied by changing the draft tube cone height using numerical simulation. Three different modified cases of draft tube depth were conducted and analyzed. The results showed that the recovery coefficients and the diffusion losses of draft tube were increased with its depth increasing within limits. However,the fraction losses were decreased with it. Thus,the draft tube depth of 3. 0D1 was chosen as the initial scheme by comprehensive consideration of the efficiency and economic factors.Besides,the turbulence kinetic energy,pressure fluctuations and force components acting on the runner were compared to judge the effect of draft tube depth on stability. The results showed that the increase of depth was favorable for the flow field stability at rated conditions. The turbulence kinetic energy at both the inlet and outlet of the cone was reduced with the heightening of draft tube cone,which also proved the flow field interaction between the draft tube and runner. The flow improvement in draft tube would in turn reduce the disturbance to runner outlet,which also explained the decreases of the peak to peak value andforce components in runner. The areas lower than the critical cavitation pressure on the suction side of blades was almost unchanged compared with the original draft tube.
The performance of draft tube plays an important role in the efficiency and stability of hydraulic turbine. To improve the hydraulic performance of an axial flow fixed-blade hydro-turbine,the depth of draft tube was studied by changing the draft tube cone height using numerical simulation. Three different modified cases of draft tube depth were conducted and analyzed. The results showed that the recovery coefficients and the diffusion losses of draft tube were increased with its depth increasing within limits. However,the fraction losses were decreased with it. Thus,the draft tube depth of 3. 0D1 was chosen as the initial scheme by comprehensive consideration of the efficiency and economic factors.Besides,the turbulence kinetic energy,pressure fluctuations and force components acting on the runner were compared to judge the effect of draft tube depth on stability. The results showed that the increase of depth was favorable for the flow field stability at rated conditions. The turbulence kinetic energy at both the inlet and outlet of the cone was reduced with the heightening of draft tube cone,which also proved the flow field interaction between the draft tube and runner. The flow improvement in draft tube would in turn reduce the disturbance to runner outlet,which also explained the decreases of the peak to peak value andforce components in runner. The areas lower than the critical cavitation pressure on the suction side of blades was almost unchanged compared with the original draft tube.
引文
1 Mc Nabb J,Devals C,Kyriacou S A,et al.CFD based draft tube hydraulic design optimization[C]∥Proceedings of the 27th IAHR Symposium on Hydraulic Machinery and Systems,2014.
2 Galván S,Reggio M,Guibault F.Numerical optimization of the inlet velocity profile ingested by the conical draft tube of a hydraulic turbine[J].Journal of Fluids Engineering,2015,137(7):071102.
3 Susan-Resiga R,Muntean S,Ciocan T,et al.Surrogate runner model for draft tube losses computation within a wide range of operating points[C]∥Proceedings of the 27th IAHR Symposium on Hydraulic Machinery and Systems,2014.
4 Avellan F.Flow investigation in a Francis draft tube:the FLINDT project[C]∥Proceedings of the 20th IAHR Symposium on Hydraulic Machinery and Systems,2000.
5 Tridon S,Barre S,Ciocan G D,et al.Discharge imbalance mitigation in Francis turbine draft tube bays[J].Journal of Fluids Engineering,2012,134(4):041102.
6 郭鹏程,朱国俊,李昀哲,等.水轮机尾水管肘管的多工况优化设计[J].水动力学研究与进展,2013,28(6):761-767.Guo Pengcheng,Zhu Guojun,Li Yunzhe,et al.Multi-point optimization design of draft tube elbow[J].Chinese Journal of Hydrodynamics,2013,28(6):761-767.(in Chinese)
7 魏先导,冯军,陈华泉.混流式水轮机窄高型尾水管的应用研究[J].武汉水利电力大学学报,1993,26(1):1-8.Wei Xiandao,Feng Jun,Chen Huaquan.Research on the application of narrow draft tubes of Francis turbines[J].Engineering Journal of Wuhan University,1993,26(1):1-8.(in Chinese)
8 郭涛,张立翔.混流式水轮机尾水管近壁湍流特性和流场结构研究[J].农业机械学报,2014,45(9):112-118.Guo Tao,Zhang Lixiang.Numerical study of swirling flow fields in Francis turbine under small opening condition[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(9):112-118.(in Chinese)
9 周凌九,王正伟,黄源芳.尾水管水力稳定性受直锥段高度影响的性能预测[J].大电机技术,2004(4):47-51.Zhou Lingjiu,Wang Zhengwei,Huang Yuanfang.The performance predicting of influence of draft tube height on its hydraulic stability[J].Large Electric Machine and Hydraulic Turbine,2004(4):47-51.(in Chinese)
10 Laurent B,Hélène G,Etienne P.Analysis of runner-draft tube numerical coupling on Kaplan and pump turbine cases[C]∥Proceedings of the 20th IAHR Symposium on Hydraulic Machinery and Systems,2000.
11 胡西萍.三甲水电站机型选择及尾水管高度对机组效率的影响[J].甘肃水利水电技术,1994(2):25-27.Hu Xiping.Effect of turbine type and draft tube height on the unit efficiency[J].Gansu Water Conservancy and Hydropower Technology,1994(2):25-27.(in Chinese)
12 李仲全,王军.尾水管高度和宽度对水轮机水力性能的影响[J].东方电气评论,2006,20(1):20-25.Li Zhongquan,Wang Jun.The influence of height and width of draft tube on it's hydraulic performance[J].Dongfang Electric Review,2006,20(1):20-25.(in Chinese)
13 Bornard L,Debeissat F,Labrecque Y,et al.Turbine hydraulic assessment and optimization in rehabilitation projects[C]∥Proceedings of the 27th IAHR Symposium on Hydraulic Machinery and Systems,2014.
14 Motycak L,Skotak A,Obrovsky J.Analysis of the Kaplan turbine draft tube effect[C]∥Proceedings of the 25th IAHR Symposium on Hydraulic Machinery and Systems,2010.
15 De Henau V,Payette F A,Sabourin M,et al.Computational study of a low head draft tube and validation with experimental data[C]∥Proceedings of the 25th IAHR Symposium on Hydraulic Machinery and Systems,2010.
16 章登成.弯肘形尾水管的改形设计对其回能系数影响的研究[D].赣州:江西理工大学,2011.Zhang Dengcheng.The effect of the elbow draft tube shape on the recovery coefficient[D].Ganzhou:Jiangxi University of Science and Technology,2011.(in Chinese)
17 王正伟,陈柳,肖若富,等.低水头混流式水轮机蜗壳和尾水管结构变化对流动损失的影响研究[J].水力发电学报,2008,27(5):147-152.Wang Zhengwei,Chen Liu,Xiao Ruofu,et al.Study on influence of the construction change of the spiral casing and draft tube on the flow loss in low head Francis turbine[J].Journal of Hydroelectric Engineering,2008,27(5):147-152.(in Chinese)
18 Müller A.Physical mechanisms governing self-excited pressure oscillations in Francis turbine[D].Lausanne:cole Polyechnique Fédérale de Lausanne,2014.
2 Galván S,Reggio M,Guibault F.Numerical optimization of the inlet velocity profile ingested by the conical draft tube of a hydraulic turbine[J].Journal of Fluids Engineering,2015,137(7):071102.
3 Susan-Resiga R,Muntean S,Ciocan T,et al.Surrogate runner model for draft tube losses computation within a wide range of operating points[C]∥Proceedings of the 27th IAHR Symposium on Hydraulic Machinery and Systems,2014.
4 Avellan F.Flow investigation in a Francis draft tube:the FLINDT project[C]∥Proceedings of the 20th IAHR Symposium on Hydraulic Machinery and Systems,2000.
5 Tridon S,Barre S,Ciocan G D,et al.Discharge imbalance mitigation in Francis turbine draft tube bays[J].Journal of Fluids Engineering,2012,134(4):041102.
6 郭鹏程,朱国俊,李昀哲,等.水轮机尾水管肘管的多工况优化设计[J].水动力学研究与进展,2013,28(6):761-767.Guo Pengcheng,Zhu Guojun,Li Yunzhe,et al.Multi-point optimization design of draft tube elbow[J].Chinese Journal of Hydrodynamics,2013,28(6):761-767.(in Chinese)
7 魏先导,冯军,陈华泉.混流式水轮机窄高型尾水管的应用研究[J].武汉水利电力大学学报,1993,26(1):1-8.Wei Xiandao,Feng Jun,Chen Huaquan.Research on the application of narrow draft tubes of Francis turbines[J].Engineering Journal of Wuhan University,1993,26(1):1-8.(in Chinese)
8 郭涛,张立翔.混流式水轮机尾水管近壁湍流特性和流场结构研究[J].农业机械学报,2014,45(9):112-118.Guo Tao,Zhang Lixiang.Numerical study of swirling flow fields in Francis turbine under small opening condition[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(9):112-118.(in Chinese)
9 周凌九,王正伟,黄源芳.尾水管水力稳定性受直锥段高度影响的性能预测[J].大电机技术,2004(4):47-51.Zhou Lingjiu,Wang Zhengwei,Huang Yuanfang.The performance predicting of influence of draft tube height on its hydraulic stability[J].Large Electric Machine and Hydraulic Turbine,2004(4):47-51.(in Chinese)
10 Laurent B,Hélène G,Etienne P.Analysis of runner-draft tube numerical coupling on Kaplan and pump turbine cases[C]∥Proceedings of the 20th IAHR Symposium on Hydraulic Machinery and Systems,2000.
11 胡西萍.三甲水电站机型选择及尾水管高度对机组效率的影响[J].甘肃水利水电技术,1994(2):25-27.Hu Xiping.Effect of turbine type and draft tube height on the unit efficiency[J].Gansu Water Conservancy and Hydropower Technology,1994(2):25-27.(in Chinese)
12 李仲全,王军.尾水管高度和宽度对水轮机水力性能的影响[J].东方电气评论,2006,20(1):20-25.Li Zhongquan,Wang Jun.The influence of height and width of draft tube on it's hydraulic performance[J].Dongfang Electric Review,2006,20(1):20-25.(in Chinese)
13 Bornard L,Debeissat F,Labrecque Y,et al.Turbine hydraulic assessment and optimization in rehabilitation projects[C]∥Proceedings of the 27th IAHR Symposium on Hydraulic Machinery and Systems,2014.
14 Motycak L,Skotak A,Obrovsky J.Analysis of the Kaplan turbine draft tube effect[C]∥Proceedings of the 25th IAHR Symposium on Hydraulic Machinery and Systems,2010.
15 De Henau V,Payette F A,Sabourin M,et al.Computational study of a low head draft tube and validation with experimental data[C]∥Proceedings of the 25th IAHR Symposium on Hydraulic Machinery and Systems,2010.
16 章登成.弯肘形尾水管的改形设计对其回能系数影响的研究[D].赣州:江西理工大学,2011.Zhang Dengcheng.The effect of the elbow draft tube shape on the recovery coefficient[D].Ganzhou:Jiangxi University of Science and Technology,2011.(in Chinese)
17 王正伟,陈柳,肖若富,等.低水头混流式水轮机蜗壳和尾水管结构变化对流动损失的影响研究[J].水力发电学报,2008,27(5):147-152.Wang Zhengwei,Chen Liu,Xiao Ruofu,et al.Study on influence of the construction change of the spiral casing and draft tube on the flow loss in low head Francis turbine[J].Journal of Hydroelectric Engineering,2008,27(5):147-152.(in Chinese)
18 Müller A.Physical mechanisms governing self-excited pressure oscillations in Francis turbine[D].Lausanne:cole Polyechnique Fédérale de Lausanne,2014.