T-Type Labyrinth Seals Dynamic Response Evaluation Using Computational Analysis

Abstract

Abstract. Effective sealing in rotating machinery is fundamental to maintaining efficiency and ensuring stable operation. Secondary leakage between high- and low-pressure regions not only reduces performance but can also introduce destabilizing aerodynamic forces. Among annular gas seal technologies such as brush, hole pattern, and honeycomb designs, labyrinth seals remain the most widely used because they are mechanically simple, reliable, and cost-effective. Recently, a modified T-type labyrinth seal has been introduced, demonstrating improved flow control and reduced flow-induced excitations compared to conventional straight-through configurations. The distinguishing feature of the T-type design is its T-shaped tooth geometry, which modifies the internal flow structure and enhances the inward radial forces associated with the Lomakin effect. This change in flow physics directly influences both leakage characteristics and rotordynamic behavior. Seal tip clearance plays a pivotal role. A smaller clearance generally reduces leakage but can alter aerodynamic stiffness and damping, thereby affecting rotor stability. Determining an appropriate clearance, therefore, requires more than a simple comparison at fixed geometry; it demands a structured parametric evaluation that captures the coupled aerodynamic and rotordynamic effects. Previous investigations have demonstrated leakage reductions of 23.6–25.3% for T-type labyrinth seals relative to straight-through designs, with axial length and tip clearance held constant. These findings point to clear performance advantages but leave open the question of optimal geometric tuning. Building on this, the present study conducts a sensitivity analysis using a design of experiment (DOE) framework coupled with steady-state computational fluid dynamics (CFD). The DOE approach enables systematic exploration of the clearance parameter space and quantifies the influence of the clearance parameter on leakage performance. In parallel, equivalent rotordynamic force coefficients are extracted from the CFD solutions to evaluate seal-induced stiffness and damping and to assess stability trends. To further establish practical relevance, the seal performance is examined across a range of pressure ratios and rotational speeds representative of aero-engine operating conditions. The results provide a coherent picture of how tip clearance governs both leakage and rotordynamic response in T-type labyrinth seals. Beyond confirming their leakage advantage, the study offers quantitative guidance for clearance selection and contributes to the broader effort to integrate aerodynamic performance and stability considerations into advanced seal design.