An aerothermal analysis of the effects of tip gap height and cavity depth of a gas turbine blade

To investigate the effects of tip gap height and the squealer cavity depth on aerothermal performance of a gas turbine rotor, two tip gap height and eight squealer cavity depth are investigated under stage environment. For the aerodynamic performance of blade tips, when the tip gap height is increased from 1.0% span to 1.5% span, the tip leakage flow rate is increased by about 1.0% total mass flow and the total pressure loss coefficient is increased by about 0.03. With the increase of cavity depth, the tip leakage flow rate is reduced but the vortexes loss in the cavity and passage vortex is enlarged, so the total pressure loss coefficient is reduced at first and then is increased. For the film cooling effectiveness of blade tips, the average film cooling effectiveness of tip is improved at a large tip gap height and a small cavity depth. With the increase of cavity depth, the area needed cooling protection is increased; the relative location between the film hole and the separation line is changed, resulting in the change of film area of the squealer tip. Thus, the film cooling effectiveness of the squealer tip is reduced with fluctuation when the cavity depth is increased. In all, the influence of the tip gap height and cavity depth on tip leakage flow rate, total pressure loss coefficient and film cooling effectiveness is conflicting. Determining an optimal cavity depth in which more film holes located on the separation line for a fixed tip gap height is important to obtain better aerodynamic performance and film cooling performance.