Interior Flow Analysis And Capacity-increasing Transformation For HL638-WJ-84 Turbine

Having expected performance and capacity-increasing, it is the preferred solution by changing the new runner to capacity-increase.When no new runner alternative,large units can entrust R & D department to develop new hydraulic model, while small and medium units can only choose to give up as high costs.In recent years, CFD technology has been widely used in hydraulic turbine design, providing a good numerical simulation platform to predict turbine performance.A large number of water is abandoned in summer at Qinghai weiwa hydropower station, the turbine rated output is far smaller than the generator rated output when 1# Francis Turbine at design head, the conditions of water resources and unit provide the necessity and feasibility of capacity-increasing. This paper use HL638-WJ-84 turbine as research object,bringing up a method that makes capacity-increase and output improvement by reducing the number of blade and cutting blade outlet at the same time,try using CFD numerical simulation analysis to estimate the effect of modification in order to achieve purposes that CFD technology can more accurately guide capacity-increasing work.According to the results, the runner’s efficiency is reduced by 1%, the output increases 139kW in optimal conditions after the transformation; When the runner runs in limiting conditions, the output increases 362kW after the transformation, it indicate that the runner’s output after transformation increases 16.35% than before the transformation, reaching capacity effect. Accordingly runner transformation program, unit capacity increase of 23% actually.Due to many factors, the maximum turbine output CFD calculations is smaller than the actual result of the transformation nearly 7%,But it has been shown CFD simulation results can be semi-directed guide for small and medium turbines capacity-increasing work, of course, it shows that further research is needed to improve the simulation precision.Although it is impossible to give a full hydraulic turbine characteristic test curve, but in terms of hydropower station which running only unit speed,it has been able to meet the actual needs of capacity-increasing.In this paper, the turbine is selected four typical operating point (small flow conditions, the optimum condition, limiting conditions and high flow conditions), using standard k-εturbulence model and SIMPLEC algorithms. The results are as follows:it appears both partial high-pressure in the back of the blade inlet near the ring and band in the back of the blade near the trailing edge when turbine in low flow conditions and limit conditions before the transformation, but local high-pressure disappears and low-pressure area reduces after the transformation, indicating that the cavitation in the back of the blade weaken, improving cavitation performance; But the flow don’t improve at high flow conditions. In optimal conditions, local low appears at the working face of the blade outlet, but disappears after the transformation; After transformation, runner outlet rotation is greater than before in the same condition, the turbine optimal efficiency area after the transformation is offset to a large flow condition,the turbine flow capacity increase after transformation.