Investigating the Effects of Film Cooling On the Performance Characteristics of an Axial Turbine

In this paper, a numerical study of the overall performance and flow structure in an axial turbine and the effect of a film cooling on it are discussed. For this purpose, two-stage axial turbine is simulated and numerically analyzed using the ANSYS-CFX commercial software. Various analyzes have shown that the rate of blowing ratio (B.R) equaled 0.82 and the velocity ratio (V.R) equal to 0.4 with a 30 degree jet angle is suitable for cooling holes. Of course, because of the high importance of leading edge and coolant inject to the stagnation region, as well as increasing the temperature at the pressure side relative to the suction side, there is a higher flow rate for cooling in these areas. The study of the turbine performance curve shows a slight reduction in the pressure ratio and efficiency due to the application of cooling, which can be compensated by the possibility of increasing the inlet temperature. The streamlines around the blade provide a layer of flow with low temperatures, which is an obstacle between the hot flow and the blade surface. The application of cooling reduces the temperature of the pressure and suction surfaces of the blade at about 300 ° C and the temperature of the front surface of the blade is about 200 °. Investigating the radial and axial variations of the thermodynamic parameters indicates that, by applying the cooling, the mach number and total temperature of the flow at inlet and outlet are reduced and the pressure drop increases.