Investigations of the conjugate heat transfer and windage effect in stepped labyrinth seals

In the current paper, conjugate heat transfer and windage heating in the stepped labyrinth seals with smooth and honeycomb lands are numerically investigated by using the commercial software ANSYS CFX11.0. Firstly, the utilized numerical approaches, such as the turbulence model and grid independence analysis, are determined to ensure a suitable numerical method for the present study. Based on the obtained measurement data, the computed heat transfer coefficients on the rotor and stator surfaces are carefully validated. To reveal the influence of the solid domain on the heat transfer computations, the comparisons between the results with and without solid domain are performed. It shows that the predicted heat transfer coefficient distributions with the presented conjugate heat transfer methods (with solid domain) agree well with the experimental data. Difference between the numerical results with and without solid domain only exists in the high temperature gradient region. Compared to the smooth labyrinth seal, the presence of honeycomb cells increases the temperature gradient in the labyrinth fin (solid domain) and significantly decreases the temperature gradient in the stator (solid domain). Secondly, in order to assess the influence of the rotating effect on the windage heating for the stepped labyrinth seal, total temperature difference between the seal inlet and outlet are computed under different effective pressure ratios for both the smooth and honeycomb configurations. Based on the energy conservation law, the windage loss for the high speed rotating seal is also obtained by taking the heat transfer between the fluid and solid into consideration. Finally, the influences of the effective pressure ratio and inlet preswirl ratio on the heat transfer coefficient distributions of rotor and stator for both the smooth and honeycomb configurations are discussed in detail.