Model experiments on unconventional ducted propulsor without rotating blades

传统的螺旋桨有大的旋转叶片以获得有效的推力，各个叶片作为螺杆在水中推进。在本研究中，提出了一种非常规导管推进器。它有一个风道，一个旋转的凸台和安装在风道内表面上的螺纹面的叶片。凸台旋转运动引起的粘性旋转流动被叶片沿管道内表面弯曲。根据这种内部流动，可以产生前端的吸流和后端的加速吹流。对这种新型推进器的性能进行了实验研究。研究了原模型及其在不同设计参数下的改进模型。实验结果证实了该推进器所产生的推力，但推进器效率低于常规螺旋桨。对于这种新型的管状推进器，还将有更多的实际改进。

A conventional screw propeller has large rotating blades to get effective thrust force, and the respective blades advance in water as screws. In the present study, an unconventional ducted propulsor is proposed. It has a duct, a rotating boss and vanes with screw surfaces installed on the duct inner surface. Viscous rotational flows caused by rotating motion of boss are curved by the vanes along the duct inner surface. According to this inner flow, suction flows at the front side and accelerated blowing flows at the rear side can be induced.Experimental studies on performances of this new propulsor are carried out. Original models and their improved models based on the various design parameters are investigated. As results of the experiments, thrust forces caused by the new propulsor are confirmed, however, propeller efficiencies are lower than those of conventional screw propeller. For this new type duct-shaped propulsor, more practical improvements will be expected.