高比速混流式水轮机固液两相数值模拟

发布时间：2018-06-15 23:24

本文选题：混流式水轮机 + 数值模拟　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：我国水力资源丰富，但近年来森林的砍伐与植被的破坏导致河流含沙量增大，，对水轮机过流部件造成严重磨损。虽然水电站已采取一定的补救措施，但水轮机的性能仍受到一定影响，水轮机效率严重下降，电站运行成本增加，经济效益下降。导致水轮机磨损的因素有多种，但设计阶段未能充分考虑泥沙颗粒的影响是造成在运行电站磨损的一个主要原因，因此，对于泥沙磨损的研究具有明确的理论意义和实际意义。本文基于N-S方程分别以清水和含沙水为介质对高比转速混流式水轮机进行全流道数值模拟，分析内部流动特性，掌握泥沙颗粒对过流部件的磨蚀规律。在清水工况下水轮机内部的流动特性较好，而含沙工况下水轮机效率下降明显。为研究泥沙颗粒对水轮机性能影响，采取单一变量法。在流量和泥沙颗粒直径不变时，随着泥沙体积分数的增大过流部件的磨损加剧且不成线性变化，泥沙体积分数增大一定数值之后，磨损量剧增。在流量与泥沙体积分数不变的情况下，泥沙颗粒直径的改变对过流部件磨损不能简单定量分析，模拟结果发现泥沙颗粒直径越小其与水的相对速度越小，即此时泥沙颗粒以更高的速度冲击材料表面，另外，随着泥沙粒径的减小，颗粒的惯性作用降低，对过流部件上部位置的冲击更加剧烈，加剧了该区域的磨损程度，而且磨损更呈现出对称性，而大直径颗粒对转轮、导叶等靠下位置的局部磨损更严重。当泥沙特性不变时，流量自小到大改变对应于河流自枯水期向丰水期过渡，对于同一台水轮机，流量增大则过机流速增加，水轮机磨损会加剧。计算结果表明：不论是何种工况下，水轮机的磨损位置主要是蜗壳底部、蜗壳鼻端、座环、固定导叶和活动导叶头部、转轮进出水边及叶片下侧三角区。将数值模拟结果与电站运行一个汛期的过流部件磨损情况对比，计算结果符合实际磨损情况，说明ANSYS CFX软件可以很好的模拟水轮机内部流动。通过模拟结果可以为水轮机的叶型的优化及电站寻求更好的抗磨措施提供有效的帮助。
[Abstract]:China is rich in hydraulic resources, but in recent years, deforestation and vegetation destruction have led to the increase of sediment content in rivers, which has caused serious wear and tear to the hydraulic turbine overflow parts. Although some remedial measures have been taken for hydropower stations, the performance of hydraulic turbines is still affected to a certain extent, the efficiency of turbines is seriously reduced, the operating costs of power stations are increased, and the economic benefits are decreased. There are many factors leading to turbine wear, but the influence of sediment particles is one of the main causes in the design stage. Therefore, the research on sediment wear has clear theoretical and practical significance. Based on the N-S equation, the full-channel numerical simulation of Francis turbine with high specific speed is carried out using water and sand water as the medium, the internal flow characteristics are analyzed, and the erosion law of the passing parts of sediment particles is grasped. The flow characteristics of the turbine are better under the condition of clear water, but the efficiency of the turbine decreases obviously under the condition of sand content. In order to study the effect of sediment particles on turbine performance, a single variable method was adopted. When the flow rate and sediment particle diameter are constant, the wear of the flow parts increases with the increase of sediment volume fraction and does not change linearly. When the sediment volume fraction increases by a certain value, the wear rate increases sharply. Under the condition of constant flow rate and sediment volume fraction, the change of sediment particle diameter can not simply quantitatively analyze the wear of the flow passing parts. The simulation results show that the smaller the sediment particle diameter is, the smaller the relative velocity between sediment particle diameter and water is. In addition, with the decrease of sediment particle size, the inertial action of the particle decreases, and the impact on the upper position of the overflowing component becomes more intense, which intensifies the wear degree of the area. Moreover, the wear is more symmetrical, and the local wear of large diameter particles is more serious on the lower position of runner and guide vane. When the sediment characteristics are not changed, the flow rate changes from small to large corresponding to the transition from low to high water period. For the same turbine, the flow rate increases and the turbine wear will increase. The results show that the main wear position of the turbine is the bottom of the volute, the nose end of the volute, the seat ring, the head of the fixed guide vane and the active guide vane, the runner entering and leaving the water edge and the triangle area of the lower side of the blade. The numerical simulation results are compared with the wear of the overcurrent parts in a flood season of the power station. The calculated results are in line with the actual wear situation, which shows that the ANSYS CFX software can simulate the internal flow of the turbine well. The simulation results can provide effective help for the optimization of turbine blade shape and the seeking of better anti-wear measures for the power station.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TK733.1

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