C型及S型叶片的贯流式水轮机流场特性

为了研究不同叶片进出口边形状及位置对贯流式水轮机内部的流动特性及机组能量特性所产生的影响，并为贯流式水轮机叶片的水力设计提供参考，该文基于某4叶片灯泡贯流式水轮机模型机，利用ANSYS-Bladegen对转轮叶片进行优化设计，并通过数值研究的方法对优化前（C 型叶片）和优化后（S 型叶片）的贯流式水轮机进行流场分析和性能评估，以揭示2种形式的叶片几何参数差异所引起的水轮机内流动特性及水轮机能量特性的差异。研究结果表明：S型叶片因其进出口边位置低于C型叶片，因此流道内速度矩的消耗位置较低，转轮出口环量分布规律也呈S型分布；C型叶片具有较大的叶栅稠密度及包角，叶片表面低压区较小，相反S型叶片叶栅稠密度及叶片包角较小，叶片正背面压差较大，因此转轮能量转换能力优于C型叶片，同时S型的出水边有效的减小了转轮出口的低压区，有助于改善尾水管内的流动特性；叶片进出水边对转轮内的水流具有导流作用，且流量越小，这种趋势越明显，S 型叶片进水边形状有将水流导向轮缘的趋势，水流在流道内的流量分配也呈近似 S型分配；S型叶片叶栅排挤作用减小，转轮内的水力损失、转轮出口环量损失及尾水管水力损失也明显小于C型叶片，因此其整体能量特性优于C型叶片。

Flow field performance of bulb turbine with C-type or S-type blades

We studied the influence of different shapes and positions of the leading edge and trailing edge and geometric parameters of blades on the internal flow characteristics and energy characteristics of a bulb turbine, and provided a reference for the hydraulic design of bulb turbine blades and other, similar turbines. In this paper, the optimization of the blade was carried out by the use of ANSYS-Bladegen for a model bulb turbine with four blades. The flow field analysis and performance evaluation for a bulb turbine with the initial blade (C-type blade) and the optimized blade (S-type blade) were conducted numerically to reveal the influence that the two blade configurations with different geometric parameters have on the turbine flow characteristics and hydraulic energy performance, especially to analyze the hydraulic losses in each part of flow passage caused by the difference in blade geometry. The results show that for the S-type blade, due to the leading edge and trailing edge of blade are below the C-type's, the consumption location of the velocity moment of the blade in the meridional flow passage is also lower than its [need a noun here], and the velocity moment distribution after the runner is also S-shaped. The flow from the guide vanes could be fully developed before entering the runner, which will help reduce the hydraulic losses in the runner. The larger cascade density and blade wrap angle of the C-type blade made the cavitation performance better than the S-type blade, and the area of low pressure on the blade is small, because of the small cascade density and blade wrap angle for the S-type blade, the pressure difference between the pressure side and suction side of the blade is large, so the energy conversion capability is better than the C-type's. The low-pressure region at the outlet of the runner is reduced effectively, which helps to improve the flow characteristics in the draft tube. The leading edge and trailing edge of the blade could play a guidance role to the flow in the flow passage, and this effect is more obvious at low mass flow rate operation conditions. The S-type leading edge shape of the blade could direct the flow to the chamber of the runner, the discharge distribution in the runner shows a similar S-type; S-type runner has small cascade crowding role relative to the C-type, this type of blade could reduce the hydraulic losses in runner, the circulation loss at the outlet of the runner and efficiency loss of the draft tube effectively, and the energy characteristics are superior to the C-type blade.