Transient simulation and influence analysis of the labyrinth seal clearance change in the secondary air system of aero-engines

The dynamic change regularities of labyrinth seal clearance directly affect the aerodynamic efficiency of the engine, the stability of rotor dynamics, and the safety margin of hot-end components. Existing dynamic labyrinth seal clearance simulations predominantly employ full three-dimensional or mixed-dimensional methods. Due to the substantial computational costs, the aforementioned research could only analyze a single subsystem of the engine under assumed boundary conditions, resulting in limited analytical accuracy and unclear dynamic change regularity of labyrinth seal clearance in an actual aero-engine environment. Thus, this paper proposes a one-dimensional transient secondary air system (SAS) thermal-fluid-structural coupling dynamic labyrinth clearance prediction model based on the transient thermal-fluid coupling network model and deformation calculation module. Experimental validation demonstrates that the proposed prediction model exhibits good prediction accuracy during transient processes (with a maximum relative error of 5.85%). On this basis, a primary and SAS coupled model for a typical civil twin-spool turbofan engine was established to investigate the clearance change regularities under typical flight cycles. The analysis results demonstrate that neglecting the dynamic changes in the labyrinth clearance can cause the bleed of the last stage of the high-pressure compressor flow path to deviate from the design value by as much as 72.8%. Meanwhile, the resulting high-pressure axial force and turbine inlet temperature deviations from design values by approximately 1209.7 daN (38.9%) and 6.7 K, respectively.