Influence of Sealing Air Mass Flow on the Velocity Distribution In and Inside the Rim Seal of the Upstream Cavity of a 1.5-Stage Turbine

The phenomenon of hot gas ingestion at the rim seal section of turbines has been investigated for the front cavity and inside the sealing gap of an 1.5-stage turbine. This paper presents velocity distributions in and inside the rim seal. The experiments were performed using an unsteady 2D Laser Doppler Velocimetry system with a high local and time-based resolution. The hot gas ingestion has been examined for different parameters such as the non-dimensional seal flow rate and includes measurements at 17 circumferential positions with each 5 axial positions at dimensionless radii of 0.985 and 0.952. It is shown that the flow field inside the gap is influenced by the rotor blades as well as by secondary phenomena originating from the guide vanes. The location of hot gas ingestion is moving with the rotor blades and its strength is depending on the amount of seal flow rate. Unsteady interactions between rotor and stator blades have been investigated.