Theoretical and Experimental Investigation of Variable Stiffness Finger Seal

Abstract

A finger seal is a flexible and dynamic contact seal, and many researches and experiments have proved its application potential in aviation engines, gas turbines, and other equipment. However, the contradiction between hysteresis leakage and wear life in the design and initial installation condition of finger seals seriously affects the integrated performance design effect. A variable stiffness finger seal is investigated in the present study to resolve the aforementioned problems, and the influence of initial installation condition is considered. First, a theoretical model of the finger seal is established to calculate the hysteresis characteristic and contact pressure between finger feet and rotor. The performances of the variable stiffness finger seal and traditional involute curved finger seal are compared to confirm the advantages of the variable stiffness finger seal. The results show that the initial conditions such as rotor structure and support bearing clearance have an important influence on the accuracy of finger sealing performance calculation. In addition, the variable stiffness structure improves the hysteresis characteristic of the finger seal with virtually no loss of wear life under low pressure differential and reduces the hysteresis rate by more than 50%. Under high pressure differential, the variable stiffness structure reduces the average contact pressure by more than 25%. Therefore, the leakage and wear performance of the finger seal are simultaneously improved by the variable stiffness structure. This characteristic does not change with an increase in rotor excitation. This indicates that the variable stiffness finger seal provides good synthetic performance and high dynamic adaptability to random operating conditions.

Keywords:

• Variable stiffness
• finger seal
• hysteresis leakage
• initial installation condition
• durability

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 51305343), Natural Science Foundation of Shaanxi Province (No. 2017JQ5101), and Science and Technology Achievements Transfer and Promotion of Shaanxi Province in China (2018XNCG-G-11).