Research On Vibration Isolation Of Marine Diesel Engine Based On Layered Structure

With the formulation and implementation of anti-vibration regulations for ships,the requirements for vibration isolation of diesel engines are becoming more and more stringent.At present,after taking anti-vibration measures,there are still serious vibration problems in the engine room.With the advancement of the strategic goals of energy saving,high efficiency and environmental protection of ships,the challenges faced by traditional vibration isolators and complex vibration isolators are increasing day by day.Optimizing the vibration isolation of marine diesel engines,studying new concepts of vibration isolation structures,and expanding the vibration isolation bandwidth are research tasks with important theoretical significance and technical value.In this work,a marine diesel engine is taken as the research object.Aiming at the vibration problem of marine diesel engine,the theoretical analysis of vibration isolation and the research and design of new vibration isolation structure are carried out.Based on vibration isolation theory,finite element modeling and multi-body dynamics modeling methods,combined with the vibration isolation theory of periodic structures and skin laminated model,the periodic laminated vibration isolator is designed and studied.At the same time,JICHAI4190 marine diesel engine was selected as the object of vibration isolation,and the vibration isolation system was built and tested.The main research content and results of this thesis are as follows:(1).Based on analysis of structure and vibration isolation mechanism of the existing vibration isolator,combined with the laminated characteristics of the skin,steel and rubber are used as the vibration isolator materials,and a skin-like laminated vibration isolation model of steel-hard rubber-soft rubber is proposed and established.The static analysis results show that there are symmetrical deformation bulges at both sides of bottom rubber,and the total displacement increases with the number of layers.The transient analysis shows the relationship between the periodic layers number and the elastic deformation displacement.The single group of skin-like vibration isolation structures and its double-period layered vibration isolation structures have good vibration isolation effect.(2).Based on the design of the periodic laminated structure,the vibration characteristics of the three-dimensional multilayer vibration isolator model are studied by using the finite element method.The results show that the mode shapes of several groups of stacked isolators are similar,but the first mode frequency of isolators increases,and the vibration level difference increases.(3).According to the geometric model of 4190 diesel engine,a simulation system for motion and periodic vibration isolation is established by using multi-body dynamics method.Under different operating conditions,the vibration behavior of diesel engine with periodic vibration isolation is studied.The simulation results show that the periodic laminated structure has advantages in vibration isolation of diesel engine system.(4).The excitation response and vibration level comparison analysis of the laminated vibration isolator are carried out by using LMS vibration test system.Experimental results confirm the vibration isolation advantage of the double-period three layered structure.At the same time,a periodic lamination vibration isolation experimental system for 4190 diesel engine was built.The test results under steady state and variable-speed conditions further verify the excellent effect of the bionic laminated vibration isolation in terms of vibration isolation bandwidth and vibration isolation level.