Large-eddy simulation on boundary separation of high-lift low-pressure turbine blade with synthetic jet control

In order to understand the effect and mechanism of controlling blade boundary flow separation using synthetic jets for a high-lift low-pressure turbine(LPT) cascade, the large-eddy simulation(LES) method was adopted to investigate the unsteady separation flow characteristics of the LPT Pak-B cascade with and without flow control using synthetic jets. The results indicate that the separation location in the controlled case changes slightly but the reattachment location moves upstream significantly on the suction surface of the Pak-B blade. The adverse pressure gradient, total pressure loss coefficient and the size of separation bubble near the cascade trailing edge all decrease remarkably. On the suction surface of the blade, the most part of the shear layer attaches to the wall and the large-scale two-dimensional vortex does not exist. The spectrums of static pressure in the trailing edge of the Pak-B cascade clearly show the conversion of characteristic frequency to high frequency, the decrease of low frequency domain and variation of the large-scale vortex structure. In addition, in the blowing stage, the fluid with high energy out of the boundary layer are entrained into the boundary layer and the energy of the fluid inside the boundary layer increases to inhibit the flow separation; in the suction stage, the boundary layer in the upstream domain of the jet hole becomes thinner and the flow rate rises, inhibiting the flow separation downstream.