Experimental and numerical tip leakage flow visualization in the LP turbine labyrinth seal

Abstract

The subject of this publication is the identification of basic flow parameters and flow structures in the seal experimentally and compare them with CFD results. A straight-through seal with two leaning fins and smooth or honeycomb land was analysed. The sealing concept is characteristic for the tip seal of the last stage of an aircraft low-pressure turbine. Due to the limitations of the test rig the analyses presented here were conducted on a highly simplified, stationary model of the seal itself, with an axial inflow and no curvature in the circumferential direction. The characteristics of the discharge coefficient as a function of the pressure ratio for different clearances and the pressure distribution along the seal, for different pressure ratios are presented. In addition, an attempt was made to visualize the flow using the schlieren technique. The main idea of application schlieren photography was to observe the vortex and separation structures occurring during the flow through the labyrinth seal, which is the major source of pressure losses. CFD calculations were carried out using the Ansys CFX commercial code.