13th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Measurements of the discharge coefficient of labyrinth seals reveal a strong sensitivity of the cavity flow to even small changes in geometrical parameters. It is shown that accurate measurements of the seal clearance are required to model the flow with a degree of certainty, which permits further conclusions. Based on accurate representations of the geometry in CFD models, it can be demonstrated that RANS flow solvers have substantial deficits in correctly predicting labyrinth seal flow. A novel test rig has been designed and put into operation for studying the labyrinth seal leakage flow in detail using temperature and pressure as well as optical flow velocity measurement methods. The rig uses a rotating disc with a labyrinth seal on its outer perimeter, and an annular flow channel to represent the shroud cavity. Homogeneity of the inlet and outlet boundary conditions is verified by means of circumferentially and radially distributed measurements of the total temperature and pressure. The rig mirrors the geometrical and aerodynamic parameters of the cavities in an axial turbine, which will subsequently be used for further investigations.