Research On Aerodynamic Interference Of Helicopter Rotor Blades

Rotor will have a strong aerodynamic interference between the blades in the process of rotation, it will has an important influence to the aerodynamic characteristics and efficiency of the rotor blades. The research of aerodynamic interference between propeller blades has scientific and practical significance for rotor design. In this paper, the rotor CFD method is used to study the aerodynamic interference between the blades, the main works are as follows:The two blade of rotor is simplified as parallel wing, established the effective two-dimensional parallel wings physical model, numerical simulation of the interference flow field, directly observe the details of the flow, pressure changes and velocity changes, analysis of the mechanism of rotor blade aerodynamic interference.The results show that: the blade in the continuous rotary motion, any blades are always in a blade wake, when in small attack angle and small mach number, the aerodynamic interference of retreating blade is great; when in large attack angle and large mach number, the aerodynamic interference of retreating blade is lesser.However, the aerodynamic characteristics are not proportional to the aerodynamic interference. The aerodynamic interference between propeller blade section with the angle of attack, mach number and the interference distance are different. When the Angle of attack is 6°, the lift-to-drag ratio of front and behind wings is biggest, but at the same time the interference is also the strongest. In less than 0.6ma, the lift-to-drag ratio of behind wing is less than the front wing. The interaction between the blades is weakened with the increase of the distance between the blades.The aerodynamic performance of rotor blades can be improved with the reasonable choice of the number of blades and the improvement of the linear twist of propeller blades. According to the interference law of different parameters, the optimal blade number of the rotor model is calculated is 5 in this paper. Rotor blades from the root to the tip, the linear velocity and interference distance is gradually increasing, the linear velocity in less mach number, the best twist angle of blade section is slightly larger, in middle mach number, the best twist angle of blade section is slightly smaller.According to the number of blades and installation angle, established the three dimensional rotation model of rotor, numerical simulation of blade pressure distribution under different blade numbers and installation angles, calculated pulling force of the single blade and rotor. Through the analysis of the three-dimensional rotor flow field, it is known that the pressure distribution of the rotor blades is not uniform with the increase of the number of blades, and the aerodynamic interference between the blades is more and more intense, lead to the tensile strength increment of the entire rotor decreased. To non-twisted blade, the initial installation angle is different,the blade pressure distribution is different. Through the comparison of different setting angle of blade pressure distribution and the rotor force, the rotor model more appropriate installation angle is 6°.