Numerical investigation of boundary layer separation control on the low-pressure turbine blade by oscillatory blowing

Abstract

A detailed numerical investigation was conducted to explore various flow-control strategies for restraining the serious laminar separation which commonly occurs on the LPT blades when operating under low Reynolds number conditions. The simulations were carried out at a Reynolds number of 25,000 with a free-stream turbulence intensity of 0.01. A novel approach of oscillatory blowing using fluidic oscillators (FOs) was developed to manage the separation. Steady and pulsed bowing were also investigated. The results show remarkable reductions in losses, with decreases of 45.7%, 36.1% and 50.7% achieved through oscillatory blowing, steady blowing and pulsed blowing, respectively. Particularly, the laminar separation was suppressed more significantly when emolying oscillatory and pulsed blowing under conditions of low blowing ratios. This is mainly attributed to the pronounced unsteadiness induced by the unsteady blowing method. A comprehensive analysis of flow control efficiency demonstrated that unsteady blowing delivered an energy gain exceeding 20 times the power cost of flow control, whereas only 72 percent of injection costs were recovered at the test plane with steady blowing. As the blowing ratio increases, the control advantages offered by unsteady control diminish, and the effects of steady and unsteady blowing tend to be consistent. Notably, the fluidic oscillator-based actuator has the ability to induce pulsations in the boundary layer without any moving parts, thus eliminating reliability concerns and making it an attractive choice for adoption in practical turbomachinery manufacturing. This research holds significant importance in the development of more advanced and reliable active blowing techniques.