Rotating propeller and Straight-blade propeller from fishing trolling motor factory

　　The mechanism to push the ship forward: It is to change the force of nature, human or mechanical energy into the thrust of the energy converter. According to the action way, the propeller from boat trolling motor factory can be divided into active and reactive two types. Fiber, sails (sailing) by human or wind to drive the boat forward is as active, and paddle, oars, paddle wheel, water jet propulsion, the propeller from boat trolling motor factory is as reactive.. Most modern ships take the reaction propulsion system, abd the most widely used is the propeller from boat trolling motor factory.

　　The propeller from fishing trolling motor factory is to install respectively two ordinary propeller on the concentric two axis inside and outside, rotating at a constant speed in the opposite direction. Because it can reduce the loss of wake rotation, the efficiency is higher than the single propeller shaft, but its structure is complicated, the ship has not been used.

　　Since the 1960s, the ship tends to be large-scale, after using the high-power host, the vibration of ship structure damage, erosion, noise, and other problems, caused by the propeller excited vibration, have caused the attention of various countries.

　　The fundamental reason of propeller excitation lies in that the propeller blade load increase, behind the ship in the uneven wake, and in the work, it is easy to produce local unstable cavity, resulting in propeller acting on the hull pressure, the amplitude and phase are changing.