Research On Some Key Technical Issues Of Compound High Speed Helicopter

The objective of study of this paper is the compound high speed helicopter. The methods of theory and test are combined to investigate the aerodynamics characters of the rotor at high speed ratio, rotor/wing aerodynamic interaction at low speed ratio, the aerodynamics characters of vectored thrust ducted propeller , and the control of the compound high speed helicopter.A method is proposed to predict the aerodynamics of characters of rotor at speed ratio up to 0.8. In allusion to the particularity of the serious reverse flow region of high speed rotor, A dynamic model is conducted which consists of the compressibility of the advancing blade, the serious stall effect of the retreating blade,and the influence of the great sweep flow on the blade, A time-vary and non-uniform induced velocity model and unsteady flap motion model of blade are set up to adapt to the rotor aerodynamic model. The method is then used to calculate the aerodynamic performance of H-34 rotor with various combinations of advanced ratio and rotor attack angle and the results are compared with the wind tunnel test data. The results show that the method can predict the aerodynamic characteristic of high advanced ratio rotor reasonably. The arcticle furthermore analyses the effect of the reverse flow region on the performance of the H-34 rotor at various high advanced rotor ratios as well as on the angle of attack, the lift and drag coefficients of the blade sections.The rotor/wing aerodynamic interaction of the compound high speed helicopter in hover and at low speed condition is studied with theoretics and experimental method. The theoritics method comprised rotor free wake model which considers the viscidity and distorsion of the wake vortex as well as the roll up effect of the tip vortex, a wing model combining the source panel with doublet panel is adopted for the consideration of both the thickness and the lift effects of the wing. Then an iterative analytical model for the rotor/wing aerodynamic interaction of the compound high speed helicopter is established. In the experimental investigation, the rotor/wing aerodynamic interaction in hover and at low speed condition is studed by the wind tunnel test of the compound helicopter model. It is found that the interaction of the wing to the rotor is connetcted with the rotor disk loading and the relative position between rotor and wing. While the interaction of the rotor to the wing is connected with not only the rotor disk loading and the relative position distance between rotor and wing, but also the deflection angle of wing flaperon (reflect wing camber). At last, the theory method is validated by the test result.A model to predict the aerodynamic characteristics of the vectored thrust ducted propeller is proposed baset on moment theory, blade element theory and vortex theory. The model of fan, duct and rudder of the vectored thrust is developed respectively, and also the method to analyze the moment of the duct in oblique flow is proposed in allusion to the asymmetrical flow on the lip of the duct, then the method to predict the aerodynamic characteristics of the vectored thrust ducted propeller is formed. At last, the calculation results are validated to the test data.The redundant control of the compound high speed helicopter at steady flight condition is investigated finally. A flight dynamics model is developed on the sample of UH-60L/VTDP. The trim optimization of flight state from hover to 370km/h is conducted using the optimization method of SQP(Sequential Quadratic Programming), and the variety of manipulated variable, attitude as wel as the lift and thrust along with the flight speed is obtained. The results show that in hover and at low speed the lift and thrust are offered mainly by rotor, the vectored thrust takes effect as a tail rotor of a helicopter. The loading on the rotor is reduced and the wing supplement lift as forward speed is increased, at the maximum speed the rotor supplements only 40% lift, while the wing supplements 60% lift, and the thrust is supplemented fully by the vectored thrust, which embodies the comounding of the lift and thrust.