Study On Coupling Vibration Characteristics Of Internal Combustion Powertrain And Vehicle Body And Vibration Reduction

As an important part of rail transit,internal combustion bullet train has the characteristics of low investment in early construction and low cost of operation and maintenance.It is widely used in many parts of the world,and also has a certain application potential in China’s shortdistance transit,branch line transportation and non-electrified railway sections.The internal combustion powertrain is the core power source of the internal combustion motor vehicle,which is generally suspended under the car body.In order to reduce the influence of the excitation of the internal combustion power unit on the vibration of the vehicle body,the two-layer vibration isolation system of the powertrain is usually taken as the research object,and the dynamic reaction force transmitted to the vehicle body is taken as the optimization objective to optimize the vibration isolation parameters.Using this optimization method,the simulation cycle can be reduced,and the results obtained can meet the requirements of engineering application to a certain extent.However,with the development of light weight of vehicle body and high power of power unit,the optimization design of vibration isolation system based on the powertrain dynamics model ignoring the vibration of vehicle body can not meet the increasingly stringent vibration control standards.Therefore,it is necessary in traditional powertrain rigid body dynamics model on the basis of the more established considering unit,frame,body flexible internal-combustion power assembly-body coupled model,and increase the train running stability and ride comfort evaluation index,internal combustion power assembly and car body coupled vibration characteristics analysis and research of vibration reduction.In this paper,a rigid-flexible coupling system dynamics model considering the vibration of unit,intermediate frame and car body is established.The accuracy of the model is verified by the modal test results.The inherent characteristics and vibration response characteristics of two kinds of vehicle system dynamics models with and without the consideration of unit flexibility are compared and analyzed.The effects of the parameters of the first and second stage isolators and the structural stiffness of the unit on the vibration characteristics of the vehicle system are discussed.Three new vibration isolation technologies,V-type low stiffness vibration isolator,magnetic suspension quasi zero stiffness vibration isolation system and damping reducible stiffness vibration isolation system,were introduced to study the vibration reduction.The results show that the modal frequency point at 103.5 Hz unit structure vibration and the frame structure coupling vibration,part of the vibration of the frame structure and structural vibration exists a certain degree of coupling,this kind of structure vibration and the whole machine vibration,parts between structural vibration and structural vibration coupling vibration may be increased to a certain extent the vibration of the system.The flexibility of the unit has a certain influence on the vibration performance of the system.The maximum relative error of the vertical velocity of the unit can reach 23.94%,the maximum error of the vibration intensity of the unit can reach 14.00%,and the maximum relative error of the acceleration of the measuring point of the car body can reach 6.9%.Therefore,in order to more accurately calculate the vibration characteristics of the system and further optimize the vibration isolation performance of the system,It is necessary to consider the structural vibration of the unit when establishing the rigid-flexible coupling dynamics model of the vehicle.Reducing the stiffness of the first and second stage isolators can reduce the vibration speed,dynamic reaction force and vehicle body acceleration response amplitude of the powertrain in the middle and high frequency band,and improve the comfort and stability of the train.The vertical stiffness plays a major role.However,reducing the stiffness of the isolator will aggravate the vibration of the system in the low frequency band.The vibration of high frequency system can be effectively reduced by increasing the structural stiffness of unit.The three new vibration isolation technologies can effectively reduce the vibration of the vehicle system under various operating conditions and improve the running stability and ride comfort of the train.Among them,the vibration isolation performance of the vibration isolation system which can be reduced by damping is the best.The running stability index of the car body is reduced by 0.9(900r/min working condition),the reduction ratio is up to 66.9%(1100r/min working condition),and the comfort index is reduced by 8.7%(900r/min working condition).In this paper,a rigid-flexible coupling model of internal combustion powertrain and vehicle body considering the flexibility of unit,frame and vehicle body is used to analyze the coupling vibration characteristics of internal combustion powertrain and vehicle body and study the vibration reduction.The design and research of the vibration isolation system for the powertrain of the internal combustion motor vehicle has certain engineering application value,and it has certain reference significance for the vibration analysis and vibration control of other trains with suspension system.