Design Of Energy-saving Rectifier At The Stern Of A Certain Type Of Bulk Carrier

As the global marine industry develops,the technology level and performance of ships are constantly upgraded.However,the ensuing high speed development has also brought a series of problems,one of which is the control of greenhouse gas emissions generated by ships.Currently,the installation of energy-saving appendages to improve propulsion performance of propellers is widely used.One of the effective methods is the installation of propeller rectifiers.However,the parameter design of the propeller rectifier has a great influence on its energy saving effect,so it is important to study the influence of the design parameters of the rectifier on the energy saving effect.The research target of this paper is the design and optimization of the stern fairing device of 64000 DWT bulk carrier,one of the main built ship types of China Merchants Jinling Ship(Weihai)Co.Firstly,this study carried out model modeling for the target ship type and propeller,and numerical calculation simulation was performed.In order to verify the accuracy of numerical simulation,the numerical calculation results were compared with the experimental data of ship model provided by shipyard,and it was found that the error of numerical calculation was not more than 3%,which satisfied the accuracy requirement of numerical calculation.At present,the research on the hull,propeller and energy-saving devices is mainly based on the model test method.However,the model test method is costly,long and influenced by uncontrollable variables.Therefore,in this paper,Computational Fluid Dynamics(CFD)is chosen as the main research tool.Numerical simulations are used to study the mechanism of the action of the tail rectifier and analyze its flow field characteristics to gain more insight into its effect.The mechanical characteristics of the propeller before and after the installation of the rectifier,the flow field characteristics and the working principle of the rectifier were analyzed,and the influence of the variation of the design parameters of the rectifier on the propulsion performance of the propeller was investigated,in which the installation angle of attack of the pre-rotor of the rectifier,the pre-rotor height,the pre-rotor width and the pitch between the rectifier and the propeller were mainly selected,and it was found that there existed a reasonable range of values for all these design parameters.In this range,the rectifier can achieve relatively good energy-saving effect.After that,the influence of Reynolds number on the energy saving effect of the rectifier was investigated,and it was found that there is a critical value,when the Reynolds number is less than this number,the energy saving efficiency increases faster with the increase of Reynolds number,and when the Reynolds number is larger than this critical value,the growth rate of energy saving efficiency changes less,which shows that the rectifier may have better energy saving effect in the real scale.After that,the difference of the energy saving effect of the rectifier with and without rudder was examined,and it was found that the energy saving effect of the rectifier was better when there was no rudder than when there was a rudder.Finally,the scale effect of the rectifier is investigated based on the SST model,and it is found that there is a significant scale effect of the rectifier,and the energy saving effect of the rectifier is better than the model scale at the real scale.