Considering labyrinth type seals in dynamic response of heavy-duty gas turbine by full length equivalent model: Influence of different seals

Investigating the nonlinear dynamic behaviors of heavy-duty gas turbines is crucial for ensuring operational stability, yet challenging due to the complex coupling of structural irregularities and fluid-induced forces. This paper establishes a full-length equivalent model (FLEM) of a heavy-duty gas turbine shaft system, integrating a nonlinear short bearing model and a versatile interpolation database method (IDM) for sealing forces. Validated against experimental data, the model utilizing the equivalent mass method effectively captures excitation frequency of nonlinear oil film than previous method. A comparative study is conducted on the system’s nonlinear responses under four sealing conditions: without seal, labyrinth Seal (LS), diaphragm labyrinth seal (DLS), and hole diaphragm labyrinth seal (HDLS). The results demonstrate the comprehensive superiority of HDLS, which reduces the vibration amplitude at the first critical speed by 28.07% compared to traditional LS, and suppresses the maximum response by 11.08% across the broad operating range. Furthermore, complex nonlinear phenomena, including bifurcation, quasi-periodic motions, and chaos induced by oil-film instability, are revealed. Notably, distinct mode-locking behaviors (e.g., period-8 and period-15 motions) embedded within quasi-periodic regions are identified as characteristic Arnold tongues, resulting from the interaction between operational and inherent system frequencies.