Numerical investigation of leakage and power loss for different seal types in turbine stage environment

In this study, a turbine stage together with diaphragm seals and shroud seals were chosen for numerical investigation. As the baseline design, labyrinth seals' leakage and blade stage efficiency were analyzed firstly. The results illustrates that as a custom seal, although simplicity, reliableness, and easy replacement make labyrinth seals widely used in steam and gas turbine, but additional power loss caused by excessive leakage flow affects the efficiency of turbine. In order to enhance the efficiency of the turbine stage by leakage reduction, the labyrinth seals at diaphragm and shroud were replaced by brush seals and honeycomb seals respectively. Porous medium method was used to simulate the flow in bristle pack of brush seals, and the pressure drop in bristle was explored by Darcy law. Pressure distribution and flow field details of honeycomb seals were also researched by CFD method. Radial clearance has a direct influence on leakage, so the clearance effect was analyzed in this paper. Lastly, for the stage together with brush seals and honeycomb seals researched, results show that comparing to custom labyrinth seals, the reduction leakage was approximate 30% and the improvement of stage efficiency was 0.6%.