Research on leakage characteristics of labyrinth seal of air turbine used for small mobile reactor

Brayton cycle has the characteristics of safety, high efficiency and compactness, which is the primary option for the energy conversion system of small mobile reactors. The performance of the turbine and the thermoelectric conversion efficiency of the system are directly affected by the labyrinth seal. In this study, a computational fluid dynamics (CFD) model of a labyrinth seal was established based on the shaft seal geometry of an air turbine. The effects of different structural parameters such as tooth width, seal clearance, cavity depth, and inclination angle on the labyrinth seal leakage were studied by numerical simulation. The results show that the leakage rate of labyrinth seal increases with the increase of seal clearance. The effect of seal clearance on the leakage is the main factor. With the increase of seal cavity depth, the leakage first decreases and then increases. When the cavity depth increases to a certain value, the leakage tends to remain unchanged. The optimal seal cavity depth-to-width ratio is approximately 0.3. The leakage increases with the increase of seal tooth width. The leakage rate decreases first and then increases with the increase of front inclination angle. The optimal front inclination angle is 90°. The results can provide a reference for the design of labyrinth seal in air turbine.