Studies Of Airfoil Flow-Separation Control Technology Based On Piezoelectric Actuators

Flow separation is a complex and general phenomenon in fluid mechanics, existing extensively in aviation, aerospace, fluid machinery and other engineering fields. Lift lowering, resistance increase and stalling will occur during flight because of flow separation, which seriously affects the safety of aircraft and operational performance. Many methods have been presented to suppress the flow separation, among which the active control method based on piezoelectric actuators enjoy the broadest application prospect due to its simple structure, easy installation and low energy consumption, etc.. Aiming at the problems of airfoil flow separation control, an active control method with piezoelectric actuators is proposed in this paper for.(1) First, proceeding with the current situation of the application of flow control, a research of widely used flow control methods are conducted. An airfoil flow separation control technology using a group of piezoelectric actuators is introduced after taking the essence of these methods. The piezoelectric actuators are designed which are a significant part of the control technology. The piezoelectric effect and performance parameters of piezoelectric ceramic materials are brief introduced, and a piezoelectric actuator quasi-static displacements and natural frequency response of theoretical formula are obtained with the basic theory of piezoelectric equations, etc..The structure of the piezoelectric actuators are optimized, and the quasi-static response simulation analysis and strength check of the piezoelectric actuators are analyzed.(2) Second, in the ground experiment study for the piezoelectric actuators, their basic performance are obtained, which are close to the theoretical calculations and static simulation results. And the accuracy of the theoretical model has been verified. It can be found the harmonic performance of the four piezoelectric actuators is similar through the amplitude-frequency characteristic experiment. Obviously, the piezoelectric actuators can be used in wind tunnel tests to control the flow separation. A Powerful database for the wind tunnel test is obtained from voltage-displacement characteristics experiment. And suggestions for improvement of the piezoelectric actuator manufacture are proposed after analyzing causes of errors between measurements and theoretical calculations. (3) Finally, flow separation control tests by the piezoelectric actuators are considered for a NACA 0015 airfoil in a wind tunnel. Based on advanced PIV technology of flow field testing, a lot of experiments for flow field testing are completed. The experimental results show that separation flow can be effectively suppressed by the piezoelectric actuators and it can be found that the static-stall angle of attack can be extended by 7° the free-stream velocity of 15m/s,within the scope of 18°to24°; while the suppressing effect of the piezoelectric actuators flow separation will produce changes with different operating frequencies, and the amplitude of the piezoelectric actuators can also interfere in control effect of flow separation. In summary, the experiments verify that the piezoelectric actuators can effectively suppress the separated flow.