Abstract：The Pelton turbine is widely used in hydro-plants in mountainous areas with a normally 500 m higher water head, which results in a higher than 100 m/s velocity at the nozzle outlet. The fine sand particles contained in the high speed jet not only can wear the bucket surfaces but also damage the injection mechanism. The injection mechanism is mainly used to obtain a high quality cylinder jet and to increase the energy conversion efficiency in the runner. The needle erosion caused by sand particles can affect the jet velocity and profile and result in an extra efficiency loss. In this paper, a 3D unsteady multiphase flow in the injection mechanism is simulated. The fine sand particles are simplified into spherical solid particles. The discrete particle model is adopted to predict the flow and needle erosion characteristics. It is shown that the trajectories of particles with different diameters vary a lot, causing different erosion patterns in the injection mechanism. The small particles can follow the streamlines and cause abrasive wear on the needle tip, while the large particles had a greater inertia and impact the upstream area of the needle orifice easily.
[1]Xiao Yexiang, Wang Zhengwei, Zhang Jin, et al. Numerical and experimental analysis of the hydraulic performance of a prototype Pelton turbine[J]. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2014:228(1): 46-55.[2]Xiao Yexiang, Zeng Chongji, Zhang Jin, et al. Numerical analysis of the bucket surface roughness effects in Pelton turbine[C]//IOP Conference Series: Materials Science and Engineering. [S.l.]:IOP Publishing, 2013, 52(5):052032.[3]Padhy M K, Saini R P. Study of silt erosion mechanism in pelton turbine buckets[J]. Energy, 2012,39(1):286-293.[4]Thapa B. Sand erosion in hydraulic machinery[D]. Trondheim, Norway: Dept of Energy and Process Engineering, NTNU, 2004.[5]Bajracharya T R, Acharya B, Joshi C B, et al. Sand erosion of pelton turbine nozzles and buckets: A case study of chilime hydropower plant[J]. Wear, 2008, 264(3/4):177-184.[6]Peng Guangjie, Wang Zhengwei, Xiao Yexiang, et al. Abrasion predictions for Francis turbines based on liquid-solid two-phase fluid simulations[J]. Engineering Failure Analysis, 2013, 33: 327-335.[7]张涛, 陈次昌, 陈丰. 空蚀、磨损及其联合作用研究进展[J]. 排灌机械, 2006,24(4):47-53. Zhang Tao, Chen Cichang, Chen Feng. Research progress of cavitation, silt abrasion and their synergism[J]. Drainage and Irrigation Machinery, 2006,24(4):47-53.(in Chinese)[8]ANSYS Fluent Theory Guide[M/CD]. Release 15.0. Canonsburg: ANSYS Inc., 2013: 424-425.[9]Finnie I. Some observations on the erosion of ductile metals[J]. Wear, 1972,19(1):81-90.[10]韩凤琴,周晶林,吴迪,等. 三维自由射流缩流及扩散的数值研究[J]. 工程热物理学报, 2008,29(8):1323-1326. Han Fengqin, Zhou Jinglin, Wu Di, et al. Numerical research on contraction and expansion of 3-D free water jet[J]. Journal of Engineering Thermophysics, 2008,29(8):1323-1326.(in Chinese)[11]Xiao Yexiang, Cui Tao, Wang Zhengwei, et al. Numerical simulation of unsteady free surface flow and dynamic performance for a Pelton turbine[C]//IOP Conference Series: Earth and Environmental Science. [S.l.]:IOP Publishing, 2012,15(5):052033.[12]Xiao Yexiang, Han Fenqin, Zhou Jinglin, et al. Numerical prediction of dynamic performance of Pelton turbine[J]. Journal of Hydrodynamics, 2007,19(3):356-364.[13]Xiao Yexiang, Fang Bo, Zeng Chongji, et al. Erosion predictions of stock pump impellers based on liquid-solid two-phase fluid simulations[C]//IOP Conference Series: Materials Science and Engineering. [S.l.]:IOP Publishing, 2013, 52(6): 062005.[14]杨凌波,肖业祥,唐兵,等. 基于固液两相流的纸浆泵磨损预测[J]. 排灌机械工程学报, 2015,33(2):98-103,127. Yang Lingbo, Xiao Yexiang, Tang Bing, et al. Prediction of pulp pump erosion characteristic based on solid-liquid two-phase turbulent flow[J]. Journal of Drainage and Irrigation Machinery Engineering, 2015,33(2):98-103,127.(in Chinese)[15]Zeng Chongji, Xiao Yexiang, Zhu Wei, et al. Pelton turbine Needle erosion prediction based on 3D three-phase flow simulation[C]//IOP Conference Series: Earth and Environmental Science. [S.l.]:IOP Publishing, 2014,22(5): 052019.
