Numerical Investigation Of Inner Flow In Drawing Water Constrction For Hydraulic Turbine With Semi Spiral Case

In the condition of the lower head, the Francis Turbine uses semi concrete spiral case to add the flow rate, but the inhomogeneity of inflow condition, flow separation and transition in boundary layer that is leaded by the flow around stay vane could has the certain influence on the efficiency and stability, so numerical investigation of inner flow in drawing water constraction for Hydraulic turbine with semi concrete spiral case has important engineering significance.In this paper firstly large eddy simulation(LES) was used on the flow around body with blunt-tail to pursue calculation accuracy of simulation of vortex in the different turbulence model, the result was that accurate large eddy simulation could simulate the process of formation, shedding, evolution of Karman Vortex Street, finally disappearance because of wake blended with flow in the core region successfully;then, the detached eddy simulation (DES) has the larger advantage to capture the flow separation,at the same time,mesh number was saved compared to LES, so the flow calculation in single flow channel of stay vane was conducted with DES, the result was that mutual interference of vortex structures' turbulent wake behind stay vane and mutual effect of vortex could all cause the more energy dissipation and also was a reason of instability and efficiency decreases.Similarly to save quantity of mesh, the whole flow passage of Hydraulic Turbine was numerically calculated in k-εturbulence model, k-εturbulence model could reflect the quantitative characteristics of flow,the result was that there existed incidence angle on the head of stay vane, after the setting angle of stay vane was adjusted intermittently according to the flow angle of spiral case, the flow characteristics around stay vane was ameliorated obviously, hydraulic loss was decreased.The six kinds of tail shape of stay vane were compared and then investigated about the influence to the flow in the leading water construction. The result indicated that when the tailing shape was acute angle, the outlet angle of stay vane came out mutation from the least value to the most value behind the position of the tail, the flow angle behind the blade channel moderately changed, so that the tail shape is asymmetric circular-arc shape is better in variable condition.In the end, that the different radius of distribution circle existing influence on the flow in the runner was investigated, after the flow angle was analyzed, radius of distribution circle was moderately regulted to be able to change the circulation distribution on the section of blade to enhance efficiency.