Research On Tip Leakage Flow And Tip Desensitization Of A Transonic High Turbine

Tip clearance leakage flow leads to remarkable losses near the tip clearance, whichresults in the decrease of the aerodynamic and thermal performance of the high pressureturbine. In order to reduce the tip leakage loss and increase the efficiency of the turbinestage, a transonic high pressure turbine was researched. Based on the mechanismstudies of the tip leakage flow, tip desensitization was studied, and the influence onengine performance of tip desensitization was also investigated.Firstly, numerical simulations of the structure of the tip clearance and the genesisof tip leakage loss were emphasized by resolving three dimensional Navier-Stokesequations, and the influences of the height of the tip clearance was considered as well asthe rotation speed. The unsteady characteristic of the tip leakage flow and their genesiswere also studied by three dimensional unsteady simulations.Then, tip desensitization was researched. The influence of tip winglets on the tipclearance leakage flow was firstly investigated. Results show that the suction-sidewinglets divide the tip leakage flow and the leakage vortex, which weakens the leakagevortex as well as the underflow on the suction side of the rotor blade. As a result, thelosses decrease markedly and the efficiency of the turbine increases. Based on thestudies, a new winglet was designed. The new winglet further lessens the tip leakageloss, and the turbine efficiency improves by0.42%.The influence of squealer rims was studied too. The study indicates that theinfluence of the double side squealer rims is better than single squealer rim. Thevortexes in the basin block the tip leakage flow passes through the tip clearance, and thetip leakage flow mass reduces markedly as a result. The basin also transports the tipleakage flow from the leading edge to the trailing edge of the tip clearance, resulting inthe decrease of tip leakage flow mass in30%to60%chord length. The strength of theleakage vortex weakens and the tip leakage loss reduces. A well-designed tip basin waspresented in this paper, which leads to the turbine efficiency improves by0.36%.Finally, a tip-clearance-height-considered propulsion simulation model wasestablished. The model can calculate the clearance height, and send the change of the tipclearance height back to the tip desensitization, which makes the turbine efficiency changes, and then the influence of tip desensitization be achieved. The influence onengine performances of tip desensitization such as tip winglets and tip cavities werestudied, and the result shows that tip desensitization leads to the decrease of specificfuel consumption, the economical efficiency of engines is improved. In most ways thetip cavities improve engine performances better than tip winglets.