Simulation Study for Hole Diaphragm Labyrinth Seal at Synchronous Whirl Frequency

Labyrinth seals are widely used in fluid mechanics due to their simple structure. However, better leakage performance and good rotordynamic stability cannot be obtained at the same time in traditional labyrinth seals (TLS). A new type of hole diaphragm labyrinth seal (HDLS) was proposed by our previous research that combined the advantages of the TLS and the damping seal. Further flow analyses of working gas in HDLS at synchronous whirl frequency under different preswirl rates were studied in this paper. The computational fluid dynamics method was used to obtain the flow details of the HDLS. The local pressure and circumferential velocity at the central panel of the first cavity were compared. The results show that the effective stiffness decreases with increasing preswirl rate, while the opposite is true for effective damping. The maximum pressure gradient in the circumferential cavity is observed at a positive 1 preswirl rate. A stronger low-pressure vortex core appears under negative preswirl conditions, which causes at most a 0.8% reduction in leakage. Reduction of circumferential velocity in the holes also decreases the circumferential flow of working gas and enhances the damping effect of HDLS. Current studies on hole diaphragm labyrinth seals show better performance under slightly negative preswirl conditions.