Optimized Design Research On Crankshaft Connecting Rod Mechanism Of High-Power Marine Diesel Engine

With the increasing trend of high-power marine diesel engines,the issues of stress concentration and fatigue reliability in the crankshaft connecting rod mechanism have become more prominent.Therefore,it is crucial to carry out optimization design for the crankshaft connecting rod mechanism of high-power marine diesel engines.This research aims to improve fatigue strength,reliability,achieve lightweight design,and enhance power density and economic efficiency.In this study,the substructure method and finite element reduction technique are employed to analyze the fatigue reliability of the crankshaft,yielding a minimum safety factor of 2.209.Although the crankshaft exhibits high reliability during operation,it has excessive design margin.Based on topology optimization,this paper proposes a lightweight crankshaft and conducts fillet optimization to reveal the influence of fillet structure on the safety factor.After completing the multi-objective optimization of the crankshaft,its weight is reduced by about 6.3%,the safety factor is increased by 7%,and the minimum value is 1.88.Therefore,the optimized crankshaft can not only ensure safety during operation but also has appropriate design margin.In addition,based on the crankshaft research data and BP-GA algorithm,this paper developed a fillet design tool.Compared with traditional methods,the analysis accuracy of the design tool is as high as 96%,which is sufficient to ensure the accuracy of the results and has important significance for the design and optimization of key components in the field of marine diesel engine.As two mutually coordinated components,optimizing the crankshaft will change the dynamic characteristics of the connecting rod.Therefore,after completing the multi-objective optimization of the crankshaft,it is necessary to conduct fatigue strength analysis and structural optimization of the connecting rod.This paper utilizes transient stress calculation techniques to analyze the impact of bolt preload on the stress in the connecting rod,revealing the relationship between the two factors.It is found that both excessive and insufficient bolt preload can have a negative effect on the fatigue strength of the connecting rod.When the bolt preload is set to 80 k N,the safety factor increases from 1.33 to 1.97,effectively addressing the issue of connecting rod failure.The analysis results are divided into a data set and a validation set,and a crossvalidation method is employed to propose a fitting formula between the two.Finally,the validity of the simulation study is verified through diesel engine failure analysis.Through strength analysis and structural optimization of the crankshaft connecting rod mechanism,the research data provided by this paper has important significance for the development and design of new marine diesel engine.