Abstract: Based on an SST turbulence model coupled with a Langtry-Menter transition model, three-dimensional viscous unsteady Reynolds-averaged Navier-Stokes equations are solved, and the effect of pulsed vortex generator jets (pulsed VGJs) on the flow separation on the suction side of a Pak-B low-pressure turbine (LPT) blade is investigated numerically. The flow control mechanism of pulsed VGJs is revealed. The inherent relevance between the pulse frequency and duty cycle is demonstrated from the flow simulations of a low-pressure turbine blade with pulsed VGJs. The numerical results indicate that pulsed VGJs can effectively suppress or even eliminate flow separation on the blade suction side under low Re conditions. The total pressure loss coefficient and wake width are also reduced evidently. For pulsed VGJs, there is a reasonable pulse frequency (f) and duty cycle (DC) to achieve the optimal flow control effectiveness. Compared to the case without pulsed VGJs, the total pressure loss coefficient is reduced by 58% when pulsed VGJs with f=10 Hz and DC=0.5 is used.

Key words: flow separation, flow control, vortex generator jet, low-pressure turbine blade, numerical simulation