Research On Aerodynamic Interaction And Flight Characteristics Of Compound Helicopter With Rigid Coaxial Rotor

The compound helicopter with rigid coaxial rotor (compound helicopter) is a research hotspot incurrent helicopter technology. In this thesis, focusing on the compound helicopter, the in-depth studyof interaction flowfield’s CFD simulation and flight dynamics method is carried out. Firstly, amomentum-source-based numerical method suitable for rotor/propulsion propeller/fuselageinterference flowfield simulation is established, meanwhile, by combining the momentum-sourcemethod, a nonlinear flight dynamics model with high fidelity is developed for compound helicopters.On this basis, the interaction flowfield of rotor/propulsion propeller/fuselage, trim characteristic aswell as "lift offset" of an "ABC" rotor and other aspects of a compound rotor are studied. The mainwork is as follows:As background of present research, the objectives of the thesis are briefly introduced, and thenthe research status of "ABC" rotor aerodynamic characteristics, control strategy as well as control andstability characteristics of a compound helicopter are outlined, shortcomings in current researches arealso pointed out, and finally, the research method employed in this paper is presented.Considering computational accuracy, efficiency and requirement of the momentum source modelfor grid, a set of unstructured grid is developed in this thesis, which is suitable for the simulation ofcompound helicopter rotor/propulsion propeller/fuselage interference flowfield. On this basis, usingEuler equation, A CFD model which can be used to simulate interaction flowfiled of compoundhelicopter rotor/propulsion propeller is established, and through the correlation with experiment data,the model developed in this paper is validated.In Chapter3, a mathematical model for "helicopter mode","transition mode" and "airplane mode" analysis of compound helicopter control is established, and it is future combined with the fuselagemotion equations, flight dynamics model for this helicopter configuration is then derivated whichcovers all the flight mode. In this model, the momentum-source-based CFD method is used tocalculate the aerodynamics of rotor and propulsion propeller, aerodynamics of fuselage are calculatedusing CFD software, so as to improve the accuracy of flight dynamics model.Based on the flight dynamics model established in Chapter3, in the fourth chapter, analysismethod of trim characteristics for the compound helicopter with rigid coaxial rotor is presented. Byapplying the method, the trim characteristics of compound helicopter at three different flight modesare calculated and analyzed. Applying the aerodynamic interaction analysis method established in Chapter2, and combing thetrim analysis model developed in Chapter4, the interaction flowfiled of compound helicopter withrigid coaxial rotor under various flight conditions is future calculated. Meanwhile, the effects ofdifferent parameters on the rotor/propulsive propeller/body interaction flowfield are analyzed.Finally, the essence of the principle of the "ABC" rotor system-"lift offset" is analyzed, and theinfluence of specific parameters of "ABC" rotor on the aerodynamic lift and trim characteristics of acompound helicopter with rigid coaxial rotor are investigated, and some conclusions with practicalsignificance are drawn.