Influence of Secondary Sealing Flow on Performance of Turbine Axial Rim Seals

Purge flow is of great importance in cooling turbine disks and sealing rotor-stator disc cavity to reduce hot gas ingestion in gas turbines. The amount of cooling air extracted from the compressor is crucial to engine efficiency. Excessive sealing air will cause not only a reduction in work transfer but also an increase in aerodynamic losses caused by the mixing of main and sealing flow. In order to simplify rim seal structure while ensuring high sealing efficiency, the current paper optimizes the flow path of the secondary air system and presents a new rim seal structure with auxiliary sealing holes transporting a certain amount of secondary sealing flow. The new structure was compared with the conventional counterpart using validated CFD methods, showing that the additional secondary sealing flow is possible to improve sealing efficiency in disk cavity. The current paper investigates the secondary sealing flow with and without swirl (the angle of auxiliary sealing hole inclination is 0° and 45° respectively), while maintaining the total amount of the sealing flow, flowrate ratio of sealing air (main sealing flow rate versus secondary sealing flow rate=1:1, 2:1, 3:1, 4:1), found that both two parameters have essential impacts on sealing efficiency. The relationship between these two parameters and sealing efficiency was obtained, and it provides a new philosophy for the design of rim seal in gas turbines.