NUMERICAL INVESTIGATION ON THE ROBUSTNESS ASSESSMENT AND ENHANCEMENT OF LABYRINTH SEAL WITH AXIAL DISPLACEMENT AND CLEARANCE DEVIATION

The labyrinth is widely used in aero-engine, which experiences axial displacement and radial deformation due to the interaction of mechanical, aerodynamic, and thermal loads. The axial displacement and radial clearance variation of the labyrinth have a direct effect on its operating condition and then on the functions of the secondary air system. In order to evaluate the effect of axial displacement and radial clearance deviations on the mass flow rate of the labyrinth and the functions of the secondary air system, based on the fluid network method and the modular modeling method, this paper developed a low-dimensional simulation method of rotor axial displacement. In order to improve the robustness of the stepped labyrinth to axial displacement and radial clearance deviations, a new stepped labyrinth with negative feedback is proposed. Then, the effect of the structural parameters on the flow characteristics is studied, and the sealing performance of the new stepped labyrinth and the conventional stepped labyrinth is compared under different axial displacements and clearances. Finally, the robustness evaluation is performed in terms of the labyrinth sealing performance in the isolated boundaries and the environment of the secondary air system fluid network, respectively. The results show that the mass flow of the new stepped labyrinth is more sensitive to the axial displacement deviation than that of the conventional stepped labyrinth in the isolated boundaries. While in the fluid network environment, the mass flow rate and the axial bearing load variation range of the secondary air system with the new negative feedback stepped labyrinth are significantly smaller than that with the conventional stepped labyrinth. This shows that the new negative feedback stepped labyrinth has better robustness compared to the conventional stepped labyrinth when faced with axial displacement in a fluid network environment.