스팀 터빈용 조합형 엇갈린 래버린스 실의 누설량 및 동특성 해석

Abstract

Governing equations and numerical solution methods are derived for the analysis of a combination- type-staggered-labyrinth seal used in high performance steam turbines. A bulk flow is assumed for each combination-type-staggered-labyrinth cavity. Axial flow through a throttling labyrinth strip is determined by Neumann's leakage equation and circumferential flow is assumed to be completely turbulent in the labyrinth cavity. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion near the centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the combination-type- staggered-labyrinth seal. Theoretical results of leakage and rotordynamic characteristics for the IP4-stage seal of USC(ultra super critical) steam turbine are shown with the effect of sump pressure, the number of throttling labyrinth strip, and rotor speed.