Numerical investigation on influence of real gas properties on nonlinear behavior of labyrinth seal-rotor system

A nonlinear model of fluid-structure interaction between high-pressure methane leakage through interlocking seal and the whirling rotor was proposed. The real gas properties of the methane at the pressure 102 bar were considered in the mathematical reduction. Three cases of different pressure ratio 1.7, 2.5 and 3.3 at the constant inlet pressure 250 bar were chosen in the present study. Two models, e.g., ideal gas model and real gas model, were employed to investigate the influence of real gas properties of methane leakage on the rotor dynamics. Distribution of thermal parameters in the seal cavities and seal clearance were determined, e.g., density, temperature, compressibility factor and specific heat capacity. The rotor-seal system was modeled as a Jeffcot rotor subject to shear stress and pressure force associated with the methane gas leakage. Spatio-temporal variation of the methane gas forcing on the rotor surface in the coverage of the seal clearance and the cavity volume was calculated by using the Muzynska model and the perturbation analysis, respectively. The governing equation of rotor dynamics which includes the main contribution from the methane leakage forcing was solved by using the fourth-order Runge–Kutta method, resulting in the orbit of the whirling rotor.