Fluidic Sealing Fundamental Physics and Development for Turbomachinery Implementation

With ever growing demand on turbine manufacturers to over higher efficiency and lower operational costs, new modern seals must be able to withstand higher temperatures, pressures and shaft speeds but at the same time efficiently restrict flow at peak and transient load conditions and withstand abrasion, erosion, oxidation and depositions. This work investigates an alternative seal design, the fluidic seal, which could satisfy the demands of new seal designs. Fluid seals use a jet inclined upstream in direction of the leakage flow relying on the momentum exchange to block or reduce the leakage flow. Theoretically, fluidic seals could be implemented on any location where other seal designs are considered or installed. This work concentrates on fluidic seal design implemented between rotor shroud and housing of the steam and gas turbines. Numerical, analytical and experimental investigations were carried out to explore the fundamental principles of fluidic sealing, showing a possible leakage reduction of up to 40% compared to base configuration. Subsequently these principles were used to develop a fluidic seal on a small scale turbo expander unit.