Blowing–Suction Control in S-Shaped Inlet and Its Impact on Fan-Stage Performance

This paper presents a numerical investigation of flow control with blowing and suction in the whole structure consisting of an aggressive S-shaped air intake accompanied by a downstream fan stage. The results show that the effect of blowing–suction flow control is neither the simple summation of the effects of a single blowing control and a suction control nor the simple differences between them. It is the best one among three flow control techniques studied in this paper. The approach to selecting the optimum flow control scheme via simulating the single air intake, and afterward performing the numerical simulation of whole passage, has a certain rationality. With the blowing–suction flow control, the maximum isentropic efficiency and maximum total pressure ratio of the fan stage increase by 2.70 and 3.13%, respectively. Moreover, the rotor of the fan stage has a significant effect in reducing circumferential distortions. Due to the influence of the rotating fan rotor, the low-energy region at the lower side of the cross sections decreases gradually when approaching the fan-stage inlet. The low-energy fluid always exists in several blade passages after it enters the fan stage. Using the blowing–suction flow control, the relative total pressure of fluid in these low-energy passages increases to an extent. Streamlines in the fan stator flow passages and on stator blades show that the blowing–suction flow control in the air intake can improve the fan stator flow pattern, reducing the flow separation in general.