Control Of Helicopter Rotor Hub Vibration Load And Blade Dynamic Stall

Adding the trailing edge flap in the rotor blade is a potential helicopter intelligent rotor. Theperformance of the rotor and helicopter can be improved by optimizing the distribution ofaerodynamic load through the controlled motion of trailing edge flap in the azimuth of rotor disc andalong the blade span. In this thesis, the control of helicopter rotor hub vibration loads and retreatingblade dynamic stall by using trailing edge flap has been investigated, which has important theoreticalsignificance and application value.In this thesis, a four-bladed hingeless rotor was studied, adopting the dynamic model of an elasticblade with stiff trailing edge flap, using the Leishman-Beddoes unsteady two-dimensional dynamicstall model for calculation of the aerodynamic loads of blade section and using theHariharan-Leishman unsteady two-dimensional subsonic model for calculation of the aerodynamicloads of the trailing edge flap section. In steady flight condition, a computational analytical modelwas established for solving the aeroelastic responses of rotor with trailing edge flaps.In this thesis, an analytical model for control of rotor hub vibration loads by using single trailingedge flap was established. The analytical results indicated that the controlled swing angle of trailingedge flap had the significant influence on the rotor hub vibration loads. The4vibration loads couldbe optimized by using an improved control algorithm. In steady flight condition, the sinusoidal swingof trailing edge flap with a small amplitude (<3°) could effectively affect the rotor hub vibration loads.The hub vibration loads amplitude changed in the form of sinusoid with the phase difference of theflap swing. The changing trends were consistent with the flight testing results. The flap swing withdifferent frequency and amplitude had different effects on each component of the hub vibration loads.Using the relationship between the rotor hub vibration loads components and the swing parameters oftrailing edge flap obtained in the condition of sinusoidal swing of the flap, the transfer functionrequired for active control algorithm was established. All six components of the4vibration loadsrotor hub vibration loads could be effectively controlled by the control of trailing edge flap.In this thesis, an analytical model for control of retreating blade dynamic stall by using singletrailing edge flap was established. The analytical results indicated that the reasonable controlled swingof the flap could effectively alleviate the dynamic stall of retreating blade in the high speed and highload flight condition. The dynamic stall occurring area on the rotor disc and the azimuth-historyresponse of aerodynamic loads on corresponding section of blade are given in the flight condition.The sinusoidal swing of single trailing edge flap could balance the aerodynamic loads on advancing and retreating side of the rotor disk and could delay the occurring of dynamic stall on retreating blade.Combining control effect of rotor hub vibration loads and retreating blade dynamic stall by trailingedge flap, three trailing edge flaps were installed in the blade and two laws of flap motion wereoptimized to control the dynamic stall and the vibration loads at the same time.In this thesis, a model experiment of driven system composed of trailing edge flap andpiezoelectric bimorph beam was conducted to establish a resonance driving method for trailing edgeflap. The beam actuator was made of piezoelectric material. A larger angle of trailing edge flap wasobtained through exciting system resonance.