Semi-Analytical Dynamic Analysis of Noncontacting Finger Seals

Abstract

Noncontacting finger seals represent a new noncontacting and compliant seal in gas turbine sealing technology. The compliance and noncontacting nature make this kind of seals fully adaptive to rotor excursions in the radial direction without damaging the seal performance. A new semi-analytical method is developed for characterizing the linearized dynamic performance of noncontacting finger seals. The linearized dynamic characteristics of the gas film are numerically computed using the step jump method and then approximated analytically in the equations of motion using a Prony series. By combining the gas film analytical dynamic characterization with the constitutive model for the dynamic properties of noncontacting finger seals, the dynamic equation of motion for the system is derived in analytical form. The results are presented of the gas film properties, natural transient response to initial conditions, steady-state response to rotor excursion, transmissibility ratios and dynamic stability analysis using the analytical model. It is demonstrated that the steady-state responses from the closed-form solutions agree well with those by the numerical simulation, and the analytical solutions can be used as the benchmark for calibrating the results from numerical analysis.