前飞速度和升力偏置量对共轴刚性旋翼气动特性影响分析

共轴刚性旋翼前飞状态的气动特性主要由工况环境中的来流速度、密度和桨叶的翼型配置、弦长分布和扭转分布等气动布局参数决定。气动布局参数的综合影响决定了共轴刚性旋翼的的升力偏置量。了解前飞速度和升力偏置量对前飞性能的影响规律有利于设计更适合于高速飞行的共轴刚性旋翼。因此,本文通过求解可压雷诺平均N-S(Reynolds-averaged Navier-Stokes,RANS)方程对4 m直径的由两副2片矩形桨叶旋翼构成的共轴刚性旋翼模型的前飞流场进行了数值模拟,获得了不同前进比下的气动力并对不同升力偏置量下的旋翼性能进行了对比。数值模拟结果表明,随前进比增大,桨叶展向拉力分布更加趋于合理,拉力中心向桨叶中段移动,可以充分给桨尖卸载;旋翼升力主要由前行侧桨叶提供,升力偏置量过大容易产生激波诱导失速,不利于高速前飞。

Flow-Field Characteristics Measurements of Coaxial Rigid Rotor in Forward Flight

Forward aerodynamic performance of coaxial rigid rotors mainly depends on flow velocity and density in working condition, and airfoil configuration, chord distribution and twist distribution in aerodynamic configuration parameters. Synthesis effects of rotor aerodynamic configuration parameters reflect on the value of lift-offset. It facilitates designing coaxial rigid rotors suited to fly in high speed to investigate influence principles that flow velocity and lift-offset impose on forward performance. Therefore, forward flow-field of a 4 m diameter coaxial rotor composed of two 2-blade rotors are numerically simulated by solving the Reynolds-averaged Navier-Stokes(RANS)equations. Aerodynamic forces at different advance ratios and performance with different lift offset are obtained. The results show that thrust distribution on the blade spanwise is more reasonable, and thrust center moves toward middle blade part which could offload the blade tip. The lift of rotor is mainly provided by the advancing side of each rotor and large lift-offset leads to shock wave stall, which has adverse effect on high-speed forward flight.