Abstract: The finger seal is a revolutionary new technology in turbine engines. Present research indicates that dynamic hysteresis and contact wear are two key problems in finger seal design. For these reasons, a dynamic analysis model of a finger seal system is presented to study the above two problems. By means of this model, the displacement response for a finger seal and the contact pressure distribution between the finger seal and rotor are obtained. According to the displacement response result, the dynamic leakage clearance for the finger seal is obtained and the leakage is subsequently calculated. The results show preliminarily that: (1) Appropriately designed interference not only reduces the response amplitude of a finger seal but also decreases the phasedelay between the finger seal response and displacement excitation. In other words, it enables the response of finger seal to follow the motion of the rotor more closely and therefore reduces the leakage. (2) The contact pressure between the finger seal and the rotor changes periodically with the rotor in motion. (3) The maximum rotor displacement excitation amplitude is approximately equal to the windage after the rotor exceeds a specific speed. This is mainly due to the fact that the rotor displacement excitation amplitude is constrained by the windage of the rotor backup bearing. The above results are validated by a comparison with the test data in references. Therefore, this study may lead to better design of finger seals.

Key words: finger seal, hysteresis, dynamic leakage, dynamic analysis, displacement response