| The thin atmosphere on Mars provides the necessary conditions for the existence of Mars aircrafts.The complex terrain and environment of Mars have greatly limited the range and capability of Mars vehicles in the Mars exploration mission.Therefore,it is of great value for Mars aircrafts that can assist Mars vehicles to complete their missions.The significance of the Mars aircraft as an air assistance platform is lies reflected in the following four aspects:(1)The aircraft can greatly improve the speed and efficiency of Mars exploration;(2)The aircraft can cope with the harsh Martian terrain environment and reach areas that cannot be reached by the Mars Rover,especially in the southern hemisphere where there are a large number of steep craters;(3)The aircraft can hover around the cliffs to take sample or perform other operations;(4)The aircraft can expand the detection range with high altitude vision and assist the Mars Rover to choose its direction in order to avoid being trapped.The performance of the Mars aircraft mainly depends on the aerodynamic characteristics of the rotor.Therefore,it is necessary to carry out the analysis and experimental study on the aerodynamic characteristics of the rotor on Mars.Because Mars’ atmospheric density is only 1.4% of the Earth’s atmospheric density,and the temperature is very low,it is necessary to analyze the influence of the Martian atmosphere on the flow state of the outer flow field of the UAV blades based on the knowledge of aerodynamics.The aerodynamic simulation was used to study the influence of various parameters of the blade airfoil on the lift-drag characteristics of the airfoil,and to optimize the airfoil parameters as well as determine the airfoil suitable for the Mars environment.In order to evaluate the aerodynamic characteristics of the e ntire rotor of UAV in the atmosphere of Mars,based on the theory of helicopters,a theoretical model of rectangular blade for the thin atmosphere of Mars is established.Based on the aerodynamic simulation,the variation curves of aerodynamic lift coefficient and drag coefficient with Mach number and Angle of attack are obtained.Based on the theoretical model,combined with the aerodynamic simulation data,the curve of the aerodynamic characteristics of the rotor with the change of the blade pitch angle under the atmosphere of Mars is predicted.The blade aspect ratio and taper are two important parameters of the trapezoidal blade plane shape.In order to study the effects of blade aspect ratio and taper on rotor aerodynamic characteristics,based on the theoretical model of rectangular blades,the theoretical model of Rectangular blades with varying chord length and theoretical model of trapezoidal blades were established.Based on aerodynamic simulation,the law of lift coefficient and drag coefficient of airfoil changing with Maher number,attack angle and chord length is obtained.Based on the theoretical model,combined with the air fluid simulation data,the influence of the plane shape of the trapezoid blade(blade aspect ratio and taper)on the aerodynamic characteristics of the rotor is analyzed.Based on the rotor hovering measuring device installed in the Mars environment simulator,the aerodynamic characteristics of the rotor hovering are studied.Study the effects of rotor speed and blade pitch angle on the rotor aerodynamic characteristics.Determine the proper blade pitch angle.Validate the air flow simulation results and the theoretical model established in this paper. |
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