Abstract: Three-dimensional leakage flow characteristics of the stepped labyrinth seal installed in the diagram for steam turbines are investigated using the Navier-Stokes solver. The finite volume method is used to discretize the Navier-Stokes equation. The standard two equations turbulence model is used to close the solving equations. The second order upwind scheme and the first order upwind scheme are applied to solve convection and diffusion terms respectively. The leakage flow fields in the stepped labyrinth seal with different pressure ratios at three different sealing knife numbers and the same axial distance are studied. In addition, the discharge coefficient of each case is calculated. The numerical simulated results show the leakage flow rate increases with decrease of the sealing knife numbers at the same pressure ratio. The discharge coefficient increases with increment of the pressure ratio at the same sealing knife numbers. The characteristics of three-dime- nsional complex flow fields in the stepped labyrinth seal are also illustrated. The study supplies the theoretical foundation and technical support for the optimization design of the stepped labyrinth seal.

Key words: Leakage flow, Numerical simulation, Steam turbine, Stepped labyrinth seal, effect of structural damping., energy dissipation, interface circuit, vibration energy harvesting, Ultrasonic motor