Effect of Bending and Mushrooming Damages on Heat Transfer Characteristic in Labyrinth Seals

Using conjugate heat transfer calculations, the heat transfer in straight-through labyrinth seals with and without rub damages (bending and mushrooming damages) were numerically investigated. Firstly, the numerical methods were carefully validated on the basis of obtained experimental data. At two different sealing clearances and a range of Reynolds numbers, Nu distributions on the seal rotor and stator surfaces for the original design cases were numerically computed and compared to the experimental data. The temperature fields in the fluid and inside the solid domains were obtained to account for the heat transfers between fluid and adjacent solids. Then, a range of bending angles, wear-off ratios, and mushrooming radiuses were selected to investigate the influence of rub damages on heat transfer characteristic in the labyrinth seals, and the numerical results were also compared to that of the original design cases. The results show that the calculated Nu distributions are in good agreement with the experimental data at a range of Re numbers and different sealing clearances. The turbulence model has a pronounced effect on the heat transfer computations for the labyrinth seal. Among the selected eddy viscosity turbulence models, the low-Re k-ω and SST turbulence models show superior accuracy to the standard k-ε and renormalization group (RNG) k-ε turbulence models, which overpredict Nu by about 70%. Bending damage reduces Nu on the labyrinth fin whereas it enhances heat transfer on the opposite smooth stator. The effect of bending angle on Nu distribution on the seal stator surface is larger than on the rotor surface. The mushrooming damage has a pronounced effect on Nu distributions on both rotor and stator surfaces for the labyrinth seal. It shows that Nu distributions on the rotor and stator surfaces decreases with the increase of the mushrooming radius, but increases with the increase of wear-off ratio and Re.