Leakage,heat transfer and thermal deformation analysis method for contacting finger seals based on coupled porous media and real structure models

Abstract

Finger seal is a type of compliant seal configuration that has superior sealing performance compared with conventional labyrinth seals and brush seals. However, complex working conditions lead to leakage, thermal gradient and deformation, which can be more serious for a contacting finger seal due to frictional heating. In this paper, a leakage and thermal performance analysis method coupled with porous media and a real structure model was developed to numerically simulate the leakage, heat transfer and thermal deformation characteristics of a contacting finger seal. The method innovatively established a porous media fluid dynamics and heat transfer model and modified the frictional heating model by introducing the concept of a friction work conversion ratio. Then, the thermal deformation of the fingers was calculated on the basis of pressure and temperature results by using the thermal-stress module of ANSYS Workbench. The results show that the leakage analysis porous media model has good calculation accuracy and most of the fluid leaks through the finger foot, while the pressure drops mainly in this field. The highest finger temperature occurs at the downstream side of the contact surface between the finger foot and the rotor. The largest thermal deformation of each laminate occurs at the finger foot toe and increases slightly along the flow direction. Additionally, the largest relative circumferential thermal deformation can reduce the gap between the fingers by approximately 5%, which is beneficial for reducing leakage. It is suggested to increase the seal inner diameter at the finger foot toe but decrease it at the finger foot heel during the design process to decrease wear and leakage.