Study On Dynamic Stall Control Of Helicopter Rotor Based On Co-flow Jet

When the helicopter is flying at high speed,the advancing side always produces shock-induced dynamic stall,and the retreating side is apt to dynamic stall at high angles of attack,which leads to a sharp decline in the aerodynamic performance of the rotor.These phenomena greatly limit the flight speed of the helicopter,and even threaten the flight safety.Therefore,it is of far-reaching significance to research the dynamic stall control method of the helicopter rotor.The main contents of this dissertation are as follows:In this paper,the rotor dynamic stall control was studied by numerical simulation method.The governing equations adopted the Reynolds average Navier-Stokes equations,the spatial discretization adopted the Roe scheme,the temporal discretization adopted dual time steps for unsteady calculation,and the turbulence simulation adopted the Sparlart-Allmaras model.The rotor movement was simulated using sliding grid technology.The accuracy of the numerical simulation method of the rotor flow field in this paper was verified by standard examples such as the Caradonna-Tung rotor and the AH-1G/OLS rotor.First of all,the rotor airfoil OA212 was taken as the research object,and the study of co-flow jet suppression of the rotor airfoil dynamic stall at low speed and high angles of attack was carried out.The results showed that the co-flow jet can effectively suppress the dynamic stall of the airfoil.By analyzing the flow field around the co-flow jet rotor airfoil and the baseline airfoil,the working mechanism of the co-flow jet was obtained.In addition,the momentum coefficient of the co-flow jet,the position of the injection/suction slot,and the size of the injection/suction slot were parameterized to obtain their influence rules on the suppression of dynamic stall.And then,the study of co-flow jet suppression of transonic shock-induced dynamic stall of rotor airfoil SC 1095 was carried out.An improved sloping co-flow jet was also proposed,which can suppress the shock-induced dynamic stall more effectively than the traditional stepped co-flow jet,while possessing a good effect on the dynamic stall at low speed and high angle of attack.It proved that the improved co-flow jet proposed is an effective flow control method that simultaneously suppresses the dynamic stall of the advancing and retreating blades.Besides,the mechanism of suppressing dynamic stall of rotor airfoil by this method and the influence law of control parameters of coflow jet on suppressing dynamic stall induced by shock wave were studied.Finally,for the application of co-flow jet to suppress the real helicopter rotor dynamic stall,the research on co-flow jet to suppress the dynamic stall of rotor airfoil under variable flow conditions was carried,which further verified the effectiveness of this method in suppressing the real rotor dynamic stall.On this basis,taking the real helicopter rotor as the research object,the research on rotor dynamic stall suppressed by an improved sloping co-flow jet was carried out.Moreover,by comparing the aerodynamic characteristics and flow field characteristics of the co-flow jet rotor and the baseline rotor,it was verified that the co-flow jet can effectively improve the aerodynamic performance and the dynamic stall characteristics of the rotor.