Critical Factors And Mechanism On Whirling Vibration Of Ship Propulsion Shafting

Served as the heart of ship,marine propulsion system plays a vital role one the aspect of marine's economy,mobility,safety and reliability.As the requirements improved on the process in shipbuilding industry,technology,quality,execution of “EEDI”(Energy Efficiency Design Index)and new noise levels on board ships of IMO,advanced marine propulsion system is required to be carried out.The higher requirements,more complex in structure,function and performance bring out various excitations and complex vibration characteristics.Traditional computational methods,especially of whirling vibration,which is difficult to meet requests of engineering design.To provide solutions for improving the vibration marine propulsion system performance,it is need to pay more efforts on mechanism and characteristics analysis of complex ship shafting vibration in-depth.Against this background,this paper is based on the comprehensive rotor system experiment platform with regulating elements designed by own,focus on the major shafting elements.Combination with the method of mathematical derivation,numerical calculation,dynamic simulation experimental testing and other means,the calculation about elements' coupling physical location relationships,dynamic characteristics,exciting force,flexural shafting's vibration response and experiments were performed.Main research works are as follows:Based on basic principles of mechanics of materials and elasticity,imaginary eigenvalues and eigenvectors were put forward with finite element method.Model of four degrees anisotropic rotor system is established.Analysis of elements' dynamic characteristics was also performed.Focus on the research of elements such as bearing and coupling which directly determine shaft condition,the single disturbance models of bearing displacement-load,unbalance fore and moment with misalignment,force of bent shaft were derived.Simulations of elements' influence on whirling vibration were included.Influence by secondary excitations may appear in shafting from one element to others and lead to complex vibration response.As major controlled object in the reasonable alignment of shafting,bearing displacement was taken as research subject to explore the coupling physical location relationship between other elements.The influence on centerline's degree of flexibility,shafting coupling misalignment and bearing's dynamic parameters of shaft condition were modeling and simulated.The multiple disturbances characterization method and corresponding calculation method were completed with proof by simulation on model of test bench.A special rotor system test bench with regulatable condition was established to verify the theoretical model.Based on the platform with regulating elements,experiments including unbent shafting and forced vibration under three flexural condition set were carried out.With test data,simulations of single as well as multiple disturbances were given to prove the correction and feasibility of the theory above.Calculation and characterization method of complex flexural shafting with multiple disturbances was completed.Further investigations were also put forward on a ship's propulsion shafting.The model was established with theoretical calculation of characteristic properties as well as flexural condition.Response magnitude date in the time and frequency domain by different rotating speeds was provided from a battery of tests.The correctness of method was validated with the comparison results.