基于CFD的导管调距桨尺度效应研究

常规螺旋桨在进行水动力实验时,需要满足临界雷诺数的要求,这样,实桨的尺度效应就可以忽略。但是,对于非常规螺旋桨,如导管螺旋桨,尺度效应能否忽略值得研究,因为机翼型导管和螺旋桨水动力性能各自随几何尺寸变化的规律不一致。基于CFD计算方法,对某导管调距桨的尺度效应进行数值研究。在获得可靠的数值模拟方法后,数值模拟了两个螺距比和两个进速下不同尺寸导管螺旋浆的流场。比尺包括1、1.7、3.4、4.25、8.5和17共6个几何尺寸。计算结果表明,导管螺旋桨敞水性能的尺度效应比预期的要明显。随着尺寸增大即雷诺数增大,导管的推力先略有增加后基本不变,螺旋桨的扭矩和推力略有下降,但效率有所增加;小螺距比工况下的尺度效应要比大螺距比的大。

Study on the Scale Effect of a Ducted Controllable-pitch Propeller Based on CFD

When doing hydrodynamic experiments for conventional propellers, therequirementfor critical Reynolds number should be met in order to neglect the scale effect for real propellers. However, as for unconventional propellers like ducted propellers, whether the scale effect can be neglected is worth investigating since changes of open water hydrodynamic performances of the wing-type duct and propeller with size are not consistent with each other. Based on the CFD method, a numerical study on the scale effect of a ducted controllable-pitch propelleris carried out in this paper. After obtaining a reliable numerical simulation method, flow fields of the ducted controllable-pitch propellers with different sizes are simulated for two pitch ratios and two speeds of advance. A total of 6 scales including 1, 1.7, 3.4, 4.25, 8.5 and 17 are considered. Predicted results show that the scale effect of open water performances of the ducted controllable-pitch propeller is more obvious than expected. As the size increases i.e. the Reynolds number increases, thrust of the ducts lightly increases and torque and thrust of the propeller slightly decrease, but the efficiency is improved; the scale effect for propellers with small pitch ratios is greater than that of large ones.