Demands for high efficient and environmental friendly aircrafts drive civil engines towards higher bypass ratios and smaller axial length. Both of these lead to great increase in the mean rise angle of inter-turbine ducts (ITDs), which determines the high curvature and high diffusion rate of its internal flow fields. In order to reduce the flow loss of aggressive ITDs, it is necessary to study the complex flow mechanism in ITDs, explore the factors influencing the flow and performance in ITDs, and provide technical supports to develop advanced turbine design technologies for highbypass turbofan engines. In this paper, numerical simulations of a typical aggressive ITD with struts between high and low pressure turbines of a large civil engine are carried out, and a method for comprehensively evaluating the aerodynamic performance of ITDs considering compressibility, area ratio, outlet flow angle is proposed. With this method, the influence of geometric parameters on ITDs flow structure and performance is discussed. The study shows that the area ratio has important influence on the flow field inside the ITDs, and the optimization of area distribution can improve the aerodynamic performance of ITDs. Finally, the influence of inlet aerodynamic conditions such as inlet Mach number and turbulence intensity on flow structure and performance of ITDs is analysed.
In this paper, to investigate the effects of inclined squealer rims on tip leakage flow and loss, numerical simulations have been performed on a transonic high-pressure turbine. Based on the geometry of prototype with conventional cavity tip, six modifications with different inclined rims are constructed. The effects of inclined suction side squealer rim (SSSR) on tip leakage flow (TLF) is analyzed emphatically. The results show that it is advantageous to control the TLF and loss if the internal and external surface of SSSR are inclined in a proper direction. When the internal surface of SSSR is inclined toward the cavity, the scraping vortex and its pneumatic labyrinth sealing effect are enhanced, which is beneficial to blocking the TLF and reducing the mixing loss. As the external surface of SSSR is inclined toward the passage, the pressure gradient near the tip changes and the intensity of adverse pressure gradient decreases, which is conducive to suppressing the breakdown of tip leakage vortex (TLV). In addition, the inclined external surface could make the TLV away from the blade and reduce the viscous dissipation. Regarding the aerodynamic performance of the turbine, the inclined pressure side squealer rim (PSSR) could improve the stage efficiency of the turbine by 0.08% relative to the prototype, while the proper inclined SSSR could further improve that by 0.18%.
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