Comparison of leakage performance and fluid-induced force of turbine tip labyrinth seal and a new kind of radial annular seal

• A radial annular rim seal was presented to replace conventional labyrinth seal.
• A complete three-dimensional CFD model was employed to analyze the fluid flow.
• The seal forces increased linearly with the increasing speed.
• An improvement for RARS in flow angle and efficiency was made at the blade exit.
• Nonuniform clearance made a great difference of the yaw angle distribution.

To minimize fluid leakage loss and fluid-induced force of traditional turbine tip seals, a new kind of radial annular rim seal (RARS) is proposed in this paper. Comparing with the conventional labyrinth rim seal (LRS), the fluid leakage direction is modified from the axial to the radial direction. The flow resistance increases, and the flow-induced force is greatly reduced. A complete three-dimensional CFD model including both the rim seal and the rotor blade row was employed to analyze the inherent characteristics of the fluid flow in the whole passage. The calculated results show that the leakage flux of the RARS is about 0.03% lower than that of the LRS. The calculated results also show that the tangential force acting on the blade wheel is much smaller than that acting on the shroud in the present conditions. The rotating speed has a significant influence on the tangential force and a relatively smaller influence on the radial force. Both forces increase linearly with the increasing speed. The radial force acting on the rotating part with the LRS is about 7–11 times larger than that with the RARS, and the tangential force with the RARS is approximately 0.9 times smaller than that with the LRS. Finally, the effect of the rim seal leakage on the main flow was studied. An improvement in flow angle and efficiency at the exit of rotor blade row is calculated by reducing the leakage jet velocity and the aerodynamic mixing losses in the shroud exit cavity. Furthermore, an eccentric blade wheel tends to make a great difference of the yaw angle distribution in the circumferential direction due to the nonuniform clearance.