The Optimized Design For Shaft Bracket Of Subsea Supply Vessel

In recent years,the design for naval architecture has become more and more abundant.The optimization of design has also achieved remarkable achievements,especially in the field of marine engineering.However,in present designs the large and medium-scaled offshore projects have used the traditional propulsion system with propeller and rudder,which is the long part of propulsion shaft system to suspend in the stern of ship.In this case,the shaft bracket will have to be used to support shaft and propeller.The bracket is regards as the appendage of ship,which could cause the increase of resistance force and impacting the rapidity of the ship,and it need have enough sufficient strength and stiffness to keep the propeller normal operation.The Subsea Supply Vessel(SSV)which is the research object in this article has also used the above described propulsion system and shaft bracket.The SSV is mainly engaged in firefighting,platform supplying,subsea equipment installing and decommissioning and so on,and it has been equipped with dynamic position system for well operation of various functions.Due to the special functions,the vessel often has to work in harsh sea conditions to keep the continuity of project or mission.Compared with normal merchant ship,the working environment of propulsion system and shaft bracket is more complicated.Based on the importance of shaft bracket for propulsion system,the safety performance should be paid more attention than others.In particular,the using of dynamic position system will make the flow field around bracket more turbulent,and the impact onto the shaft bracket is particularly prominent.In many of past offshore projects,due to the insufficient of vibration resistance for bracket shaft,the vibration response in whole stern structure will happen severely during the dynamic position system working,it seriously affected the vessel's normal working and schedule or safety.Therefore,the optimization design for shaft bracket is very necessary,it could not only ensure the more safety operation of vessel,but also could obtain higher economic benefits.The main contents of this article shall include following:(1)This article shall briefly introduces the origin,working environment and importance of the shaft bracket.And it expounds the research direction and current achievement at domestic and foreign for the design.(2)Through reading a large number of reference researches,knowing the structural type and working environment of shaft bracket,the loads forced on the shaft bracket has been gained firstly and the models of geometric and mathematical have been set up after analysis and summary.And the detail analysis respectively for yield strength and vibration have been carried out based on the modal.At the same time,the optimal design parameter are determined for shaft bracket structure by scientific and reasonable optimization method.(3)Introducing the basic theory of finite element analysis,the FEM analysis shall be taken as the main method.Based on the propulsion system arrangement of SSV project,the section type of shaft bracket structure shall be determined as the design parameter for optimization.The calculation of yield strength and modal analysis for the four different sections will be carried out by FEM software.Comparing and analyzing the results comprehensively,the optimal section could be obtained.And the analysis result could provide the method and direction for the related optimization design in the future.