Experimental Research And Geometry Optimization For Rotors Of A Four-axis UAV

The research and design of rotor geometry has been proceeded since the beginning of last century.The geometry determines the efficiency of the air propeller which used as propulsion system for aircraft and the main rotor which used as lift system for helicopter.The required power can be decreased and the lift-power ratio can be increased by optimization of the geometry of rotors which are critical for the improvement of the overall aircraft performance.In the first part of the paper,the solutions of calculating the performance of rotors were concluded.The accuracy and efficiency of blade momentum theory,circulation theory,prescribed vortex method and computational fluid dynamic were compared on the performance of C-T rotors.Besides,the aerodynamic model of overlapped twin rotors was established,and the effect of overlapping area on twin rotors was analyzed by momentum source method and previous experimental data.In the next part of the paper,the lift system of a heavy load four-axis UAV was designed,mainly on the parameters of the rotor.The blade and connecting structure of the rotor were designed,and the load of rotating rotors and the load path were analyzed.On top of this,finite element analysis was made on the critical components to validate the strength requirement of connecting structure.The designed lift system were assembled to UAV for test.The experiment indicated that the requirements for the UAV were achieved.The experimental data of the overlapped twin rotors was compared with the calculated results,which indicated that the calculation method was reasonable.In the last part of the paper,the optimization design aimed at the hovering state of a single rotor was made by the minimum induced loss method and the genetic algorithm.The final design of the geometry of the rotor was determined by comparing the results of these two method.At last,the improvement of the rotor performance was analyzed,and the maximum thrust of unit power increased 10 percent for optimized rotor.