Research On The Structural Strength Analysis Method Of The Azimuth Thruster System

A high-powered azimuth thruster is required to work in the extremely harsh marine environment. This puts forward a high demand for structural strength of all the azimuth thruster parts. Influenced by its large size, high external forces, complicated structural form and unique working characteristics, the strength analysis method for conventional propulsors can not precisely evaluate the strength of the high-powered azimuth thruster. Therefore, a targeted strength analysis method is urgent for the high-powered azimuth thruster.In order to evaluate the strength of a 5000 kW Z-drive azimuth thruster, research on the strength analysis method of its main parts is carried out. Here the main parts include the propeller, the duct and the spiral bevel gears. Main works and conclusions are as follows:Firstly, hydrodynamic performances of the azimuth thruster at different rotating angles are analyzed by the CFD method. The fluid pressure on the thruster changes with the rotating angle and its regularity is obtained.Secondly, the method of transferring distributed pressure from fluid field to structure field on the structure surface is mainly discussed, among which a simple interpolating method and an automatic transmission technology for fluid pressure are proposed. Then the impact of pressure transmission and grid matching on the accuracy of strength calculation is deeply studied, and reasonable selecting principles of weighting coefficients and element size are presented.Thirdly, the impact of different structural forms on the duct strength is studied. The structural forms involve the length of brackets, the layout of reinforcement plates and the fixation of the top. Then some optimized design approaches for the duct are presented under the premise of meeting the strength requirement and lightening the structural weight.Lastly, a study on the calculating method of the gear impact force is carried out. The theoretical formulas for calculating the impact force of spiral bevel gears are derived by the elastic collision theory. Then the influence of tooth backlash and speed change on the impact force is analyzed. In addition, the effects of gear impact on the loads of drive shafts and contact fatigue life of gears are discussed.