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直升机旋翼以固定不变的转速工作,仅能使有限状态的旋翼效率达到最优,而通过旋翼转速的变化,可以实现不同飞行状态下的旋翼效率最优。为了研究不同旋翼转速时的旋翼气动特性,首先建立了适合旋翼在低转速飞行情况下的气动特性分析模型,该模型包含了Leishman-Beddoes非定常动态失速模型与适合于低马赫数(Ma<0.3)分析的Sheng失速修正模型;其次,在低速风洞2.5m旋翼模型试验台上试验研究了模型旋翼的悬停效率及前飞需用功率与旋翼转速之间的关系。试验与计算结果的对比表明:所建立的气动分析模型能够准确地计算旋翼在低转速情况下的气动特性;通过优化旋翼转速,增大了桨叶剖面迎角,提高了桨叶剖面的升阻比;并且当旋翼以最优转速旋转时,模型旋翼的悬停效率最大可以提高32%,前飞需用功率最大可以降低22%。
Helicopter rotors work at a constant rotational speed, which can only make rotor efficiency in a limited state optimal. By the change of rotor speed, rotor efficiency under different flight conditions can be optimized. In order to study the aerodynamic characteristics of the rotor at different rotor speeds, a aerodynamic model suitable for the rotor at low revolving speed is established. The model includes the Leishman-Beddoes unsteady dynamic stall model and the model suitable for low Mach number (Ma <0.3 ); Secondly, the model rotor hover efficiency and the relationship between the power required before the fly and the rotor speed were tested on a 2.5 m low-speed wind tunnel 2.5 m rotor model test bed. The comparison between the experimental results and the calculated results shows that the established aerodynamic analysis model can accurately calculate the aerodynamic characteristics of the rotor under low rotating speed. By optimizing the rotational speed of the rotor, the attack angle of the blade is increased and the lift resistance of the blade profile is increased And when the rotor rotates at the optimal rotation speed, the maximum hover efficiency of the model rotor can be increased by 32%, and the maximum power required by the forward flight can be reduced by 22%.