NUMERICAL STUDY OF VORTICES AND THEIR INTERACTIONS IN THE PASSAGE OF ROTOR BLADE WITH TIP GAP ocr jk1

A detailed three-dimensional steady-state numerical investigation using ANSYS CFX-I8.2 on a high-pressure turbine blade with linear cascade is done for tip leakage flow of an axial gas turbine. Stationary casing with a fixed blade having tip gap is considered for the present study. There is leakage flow from the pressure side to the suction side of the blade which consecutively rolls up in the passage and forms the tip leakage vortex. The formation of vortices and their interaction with each other inside the passage is complex which makes experimental investigation difficult. The effect of tip gap size, off-design incidence angles, outlet Mach number, pitch size and flow path (stagger angle) are several parameters considered during the present study. The strength of tip leakage vortex and the vortex formed inside the gap is maximum. The losses are compared in terms of total pressure loss coefficient. The deviation of the flow direction is measured in terms of yaw angle distribution. Among various turbulence model available in CFX 18.2 the BSL k-omega turbulence model shows the most reliable results with experimental data. The results are compared with the base model without the tip gap. This investigation incites a better design of the blade tip with a precise reduction in losses.