Study On Plasma Flow Control For Rotor Flow Separation

At present,many countries are developing high performance helicopters,the dynamic stall of rotor greatly restricts the improvement of helicopter flight performance.The fundamental reason of dynamic stall is rotor flow separation,how to control the rotor flow separation efficiently becomes the key of research.As a new active flow control technology,plasma flow control technology can effectively control flow separation,it has the advantages of no moving parts,short response time and wide excitation frequency bandwidth,this technology has great potential to be applied to helicopter rotor flow separation control.The modification of the rotor is small and the cost of modification is also low,plasma flow control technology has important engineering application value for improving the flight performance of helicopter.In order to explore the application of plasma flow control technology on the rotor,this paper studied the plasma flow separation control of rotor and airfoil.The startup vortex and induced vortex evolution process of different types of plasma actuator were analyzed.The plasma flow separation control of rotor airfoil with Mach number Ma=0.5 was realized by using low energy AC power supply.An experimental device for plasma flow control and measurement of rotor rotation has been developed,and the effective control of rotor rotating flow separation was realized.An equivalent device for controlling flow separation was designed,which proved that the control effect of plasma excitation on flow separation in excitation zone is better than the downstream of excitation zone.The research contents of this paper included the following aspects:1.The high-speed schlieren method was used to study the evolution process of the "steady excitation" start vortex and the "unsteady excitation" induced vortex of different types of plasma actuator,the variation of air motion induced by plasma actuator with time was revealed.The influence of duty cycle and pulse frequency of power supply on induced vortex was explored,which was helpful to understand and study the mechanism of plasma flow control.2.The high-speed wind tunnel experimental study on the flow separation characteristics of different rotor airfoils was carried out.The aerodynamic performance and separation characteristics of the OA309 airfoil and NACA0012 airfoil at different Ma numbers were obtained,which laid a foundation for high-speed plasma flow control.Both worldwide and nationwide,low energy consumption AC power supply was first used to realize the flow separation control of OA309 rotor airfoil at Mach number Ma=0.5,the experimental techniques of steel airfoil insulation,wind tunnel sealing and electromagnetic shielding had been developed,these provided a technical means for AC power supply to control the high-speed flow by plasma flow control technology.3.An experimental device for plasma flow control and measurement of rotor rotation was developed to solve the problems of synchronous collection of rotor flow data by PIV and the loading of high voltage electricity for plasma actuator.The real-time acquisition of the rotating image of the rotor in high-speed rotation under the strong electromagnetic environment of the plasma was realized,and the experimental technology of rotor plasma flow control was developed,which provided a research platform for further research.4.The aerodynamic characteristics of the rotor rotation were obtained by using the rotor rotation experimental platform,and the influence of the rotation speed on the rotor flow separation was studied.Experiment of plasma flow control for rotor rotating flow separation was carried out successfully,the data of rotor flow field with and without the plasma actuator excitation were obtained.The effective control of rotor flow separation at different rotational speeds was realized,when the flow was 8m/s,the rotor angle of attack was 18 degrees and the rotational speed was 600 r/min,the flow separation was completely suppressed.which provided a reference for the application of plasma flow control technology on rotor flow separation control.5.An equivalent device for controlling flow separation was designed to simulate the control effect of the plasma excitation region and the downstream of plasma excitation region on the separation flow,which proved that plasma excitation was effective in controlling flow separation on downstream of excitation region and excitation region,also the plasma excitation region was more effective,which had a reference value for the selection of the plasma actuator position.