Study On Tip Clearance Leakage Control Of Turbine Stage

With the development of economy, gas turbines are widely used in many fields of national economy, Gas turbine application in the field of aviation has an absolute advantage in the early 1950s on the basis to replace the piston engine as the aircraft propulsion power, so that the performance of the aircraft has been greatly improved. The turbine is one part of the three major components, generally in the high temperature and high pressure gas dynamic environment, and gas turbine internal pressure gradient, temperature gradient and turbine rotor with high speed make the flow inside the turbine very complicated, there are various forms of secondary flow in the passage, including:blade tip clearance leakage flow and passage vortex, and between these flow structures very strong interactions exist. On top leakage control has a far-reaching impact on improving the turbine efficiency, so the study of this problem has great significance.The blade tip clearance leakage of "LISA" 1.5 stage is studied, the CFD method is used to study the structure of the flow field and the loss mechanism is analyzed. The leakage vortex starts from leading edge and leakage flow has great effect on the leakage loss of 50% axial chord later. The vortex structure in the rotor channel has a great influence on the flow field of the downstream cascade.In order to control the tip clearance leakage, on the basis of the original flat type the shroud and winglet are installed. Winglet compared to the shroud and flat blade tip, which may influence the clearance leakage loss and cascade passage flow loss is analyzed. The study shows that the total pressure loss in the outlet of cascade can be reduced by 0.8%.After that, the method of jet on the blade tip is adopted to control clearance leakage flow. Study on the leakage flow and loss mechanism of tip leakage at different jet volume. The tip of the vertical jet tip leakage has a certain inhibitory effect, the greater the amount of jet, the better.With the blade rotating, the relative movement between the blade and casing, which will have a great impact on the development of clearance leakage flow and flow field. So in the end of this paper the effect of rotation of the turbine flow structure is focused. Through the calculation and analysis of cascade with flat top and cascade with winglet under blade rotating and the relative motion between the rotor and the casing, flow field structures are studied. Research shows that the rotation of the blades can promote the development of passage vortex, the leakage vortex is less affected. The relative motion between the casing and the rotor can suppress the generation and development of the leakage vortex, and make the radial distribution of the passage vortex more uniform.