涵道螺旋桨气动机理数值分析

Numerical Investigation on Aerodynamic Characteristics of Ducted Propeller

基于滑移网格模型,通过求解三维非定常N-S方程,数值研究了涵道螺旋桨非定常旋转流场特性,比较研究了普通螺旋桨与涵道螺旋桨的推力、压力、流线等的分布规律,分析了涵道螺旋桨的气动机理。结果显示,虽然涵道螺旋桨产生的拉力小于普通螺旋桨,但涵道会产生附加推力,所以涵道螺旋桨总拉力大于普通螺旋桨,且总扭矩较小,因此气动效率更高。涵道提高螺旋桨气动效率的机理主要有三点:一是减小了滑流速度,螺旋桨产生的推力减小,但滑流损失降低;二是涵道减小了滑流区域环向诱导速度,从而减小了滑流区静压损失;三是涵道改变了螺旋桨桨尖绕流特性,消除了桨尖分离涡和叶素表面分离涡,从而增大桨尖部位叶素升阻比。

The unsteady and vertical flow of ducted propeller was numerical investigation based on the unsteady compressible Navier-Stokes equations with the sliding mesh technique.The different of the distribution of propeller thrust,pressure and streamline has been numerical studied by compare with propeller and ducted propeller,and the aerodynamic characteristics of ducted propellers has been obtained.The results showed that,the thrust of propeller in ducted was smaller than that of propeller,but the ducts would generate additional thrust.Therefore,the total thrust of ducted propeller was greater than that of propeller,and the total torque was smaller,so the aerodynamic efficiency of ducted propeller was higher than propeller.The mechanism to ducted propeller improved the aerodynamic efficiency of the three main points.First,the slip velocity would reduce,so the propeller thrust would decreases and slipstream energy loss would reduce.Second,the circumferential induction speed would reduce because of the ducted influence,thereby reducing the pressure loss in slip region.Three,the culvert changes of the flow characteristics of the propeller tip,the separation vortex of blade tip and the separation vortex of blade element surface would be restrained;the lift drag ratio of element on blade tip would be increased.