Rotordynamic characterization of rotating labyrinth gas turbine seals with radial growth: Combined centrifugal and thermal effects

Abstract

In this article, a generic framework, which takes into account of both the centrifugal and thermal effects, is introduced towards rotordynamic characterization of rotating labyrinth gas turbine seals. A well-established labyrinth seal clearance-leakage model, based on a combined three-dimensional computational fluid dynamics and finite element methodology, along with a second-order rotordynamics model is engaged. The influence of combined centrifugal and thermal radial growth on the rotordynamic characteristics of a generic rotating labyrinth gas turbine seal is explored. For a given rotational speed, the computed rotordynamic seal forces and coefficients, including the stability parameters are compared with the one without considering thermal growth (ambient condition), as a function of pressure ratio and temperature. The results show a significant variation of the crucial seal coefficients with the inclusion of thermal growth and the influence largely varies with both temperature and pressure ratio. Of particular interest is the onset of instability detected at an elevated temperature, regardless of pressure ratio, which necessitates the inclusion of thermal growth so as to avoid early rotor/seal failures. The inherent flow field investigation corroborates well with the rotordynamic characteristics of the seal and its combined centrifugal and thermal effects.