Fluidic Jet Barriers for Sealing Applications

The turbine industry is continually looking for new developments to improve thermodynamic performance and sealing has received significant attention over the years. Fluidic seals employ aerodynamic flow features to create blockage/loss and reduce leakage, rather than relying on physical barriers to flow such as brush seal bristle packs etc. They are also potentially cheaper to implement than contacting seal technologies such as brush seals. The fundamental mechanism by which fluid jets inclined in an upstream direction produce blockage and reduce the flow along leakage channels are examined in the paper. Computational Fluid Dynamics is used to quantify the net gain in leakage performance that can be achieved in simple channel flow for various operating conditions and jet configurations. These results are used to guide further CFD calculations in which the potential for leakage reduction from adapting conventional labyrinth turbomachinery seal designs to include fluidic jets is investigated. Calculations are carried out for operating conditions that are typical of gas and steam turbine applications, in order to demonstrate the potential of new seal designs of this generic type. The device considered in the paper is essentially a conventional labyrinth seal design which is modified to include internal flow channels within the structure supporting the labyrinth fins, to supply the fluidic jets. The new technology is therefore a modification to an existing component with potential for application in existing turbine designs, requiring no/minimal changes outside of the seal design space to implement.