Abstract:
In this study, an axial flow turbine of Pak Mun hydro turbine was analyzed using CFD. The code is a commercial software package, CFX-5.7. The numerical simulation was conducted in order to visualize the flow patterns throughout the turbine and the turbine's performance was computed. The computational domain was divided into two parts. The first part consists of the inlet tube and the wicket gate. The second part consists of the runner and the draft tube. A tetrahedral mesh type is used for each domain. The dissimilar meshes of each domain are connected by domain interfaces.The model scale turbine runner of 340 mm diameter with 4 blades was performed in order to compare to the Voest-Alpine M.C.E.'s experiment result. The calculation was done of constant blade angle of 32.90?, a unit speed of 176.16, and a net head of 10 m. The performance curve for each wicket gate opening (65.07' - 68.03') was carried out to find the best-efficiency point (BEP) of the turbine. The cavitation analysis is then determined at that angle by varying the suction head. The results reveal that the BEP of the turbine for case of the study is at the wicket gate opening of 67.05'. The flow patterns throughout the turbine also showed with the least secondary flow. In the case of cavitation analysis, the values of efficiency, unit discharge, unit power were fallen sharply when the suction head was reduced to 4.006 m. The cavitation was formed on suction surface at the trailing edge of hub and tip. This causes the flow separation. Computational results on such a wide variety of flow situations are validated and show good agreement with the experimental measurements. The visualized on the turbine blade at the Pak Mun hydro plant also validated formation of cavitation region.