Investigation On The Lateral Vibration Characteristics Of Ship Propulsion Shafting Under Complex Supporting Condition

As the “heart” of the ship,the ship power plant plays an important role in driving the entire ship,and attributes to the safety,stability and comfort of the ship.With the attention of the country and the rise of the shipping industry,the deadweight tonnage required by large transport ships and professional engineering ships are getting larger,and not only the structure of the propulsion shaft system is more complicated,but the incentives received are more diverse,which makes the vibration problem of the propulsion shaft system more complicated.Some traditional calculation formulas can no longer meet the design and calculation requirements for the propulsion shafting of large ships today.Therefore,it is urgent to analyze the vibration characteristics of the ship propulsion shafting under various complex boundary conditions in accordance with the latest development.Under this background,a classical propulsion shafting of a large ship is studied in this paper by numerical calculation and finite element simulation.The specific research content is as follows.First,the ship propulsion shafting structure is discretized,and the transfer matrices of various components are deduced.Through the state vectors at the left and right ends of the components,the discrete shafting matrices are connected to obtain the transfer equation of the entire shafting system,and then the propulsion shaft discrete model is obtained.At the same time,a finite element continuous model of the propulsion shafting is established.The models in the comparison are compared to verify the correctness of the two analysis models.Then,the lateral vibration characteristics and forced response of the propulsion shafting model are analyzed.Linking the lateral vibration of the shafting with the lateral vibration,explaining that the former is a special form of the latter at h(ω = 0).When the axial stress is considered,the vibration characteristics and forced response of the propulsion shafting are analyzed respectively.On the equivalent support method of the bearing,and when a part of the rigid support is brought in,the characteristics of the propulsion shaft system are analyzed.Taking into account the abrasion of the heel bearing,the effective contact length is changed,and the influence of this boundary factor on the vibration of the shaft system is analyzed.The arrangement of the stern bearing on the stern shaft will also have an effect on the vibration of the shafting.Considering the above factors,the free and forced vibration of the shafting is analyzed.Finally,the influence of the stern bearing’s boundary factors on the lateral vibration characteristics of the propulsion shafting is analyzed.The boundary factors mainly include the distance between the two stern bearings on the stern shaft,the stiffness of the three equivalent support systems,as well as the parameters of oil film-base support model of rear stern bearing.Through the above analysis,it is finally found that the factor that has the greatest effect on the lateral vibration is the rear stern bearing,and among the parameters of its support system,the oil film stiffness plays a major role.Therefore,a dynamic analysis model of the oil film lubrication of the rear stern bearing is established.The influence of some structural parameters of the rear stern bearing on the oil film stiffness is studied,and the vibration characteristics of the propulsion shafting are further analyzed.The influences of key factors such as load,aspect ratio,radial clearance,and journal inclination of the rear stern bearing are mainly studied.