Study On Seal Leakage And Rotordynamic Characteristics And Structural Optimization Design

Labyrinth seal and honeycomb seal are common non-contact rotating seals in turbinemachinery.The leakage and dynamic characteristic directly affect the working efficiency and stability of the rotor system.The problem of leakage and rotor instability caused by seal are becoming increasingly prominent with the development of turbinemachinery in the direction of high speed and high pressure ratio.It directly affects the working efficiency and safe operation of turbinemachinery.In-depth study of the leakage and dynamic characteristic of the seal is helpful to provide theoretical basis for the design of the seal structure.In this paper,the leakage and dynamic characteristic of labyrinth seal and honeycomb seal were studied by combining theory,numerical value and experiment.The foundation of seal computational fluid mechanics,leakage formula and theoretical solution model of seal dynamic characteristics were analyzed theoretically.The formulas for calculating the labyrinth seal leakage which considering the real gas parameter and the inclination angle of the seal tooth were derived respectively.The leakage and dynamic characteristic solving model of labyrinth seal and honeycomb seal which considering the multi-frequency rotor elliptic vortex was established.A labyrinth seal leakage test rig of considering the seal tilt angle was built,and the numerical model was verified by experiment.The results show that,as the vortex frequency increases,the influence of molar mass on the damping coefficient is gradually transferred from the inertial effect to the frictional effect,therefore,as the molar mass of gas increases,the effective damping coefficient increases at low frequency and decreases at high frequency.The countercurrent beam caused by the rake angle of seal teeth will cause a part of momentum loss,the leakage first decreases and then increases with the increase of teeth inclined angle.The leakage remains unchanged in the range of 30° to 35°,it is the optimal selection range of the teeth inclined angle.With the increase of honeycomb-hole depth,the leakage of honeycomb seal increases first and then decreases,and the effective damping decreases.With the increase of honeycomb-hole subtense distance,the leakage of honeycomb seal increases,and the effective damping decreases at low frequency and increases at high frequency.Considering the stability and sealing performance comprehensively,it is possible to choose the structure with smaller of subtense distance and hole depth while achieving the standard for sealing performance.