Design And Experimental Study On Vibration Isolation Of Powerpack For Hybrid-power Multiple Unit

The power pack,as the power source for the operation of the hybrid-power multiple unit on the non-electrified circuit,will produce a large disturbed force during the work time,which not only causes strong vibration,but also transmits the vibration to the car body,causing the car body to be damaged.Vibration affects the comfort of passengers and the smoothness of train operation.In severe cases,it can cause partial fatigue and fracture of the vehicle structure,and even affect driving safety.Therefore,it is necessary to isolate the power pack from vibration.This paper mainly designs and verifies the double-layer vibration isolation of the power pack from three aspects: theoretical derivation,simulation calculation,and experiment.The power pack is simplified into a double-layer vibration isolation system with some substructures,which consists of a frame,a diesel generator set,a cooling system,and exhaust gas aftertreatment.The diesel generator set and the frame are elastically connected to form a first-level vibration isolation system,the frame and the car body are elastically connected to form a second-level vibration isolation system,and the cooling system and exhaust gas aftertreatment are elastically connected with the frame to form a sub-structure vibration isolation system.In the study,the components of the power pack are regarded as rigid bodies,and the car body is regarded as a rigid foundation,and the dynamic equations of the doublelayer vibration isolation system with 24 degrees of freedom are derived.The SQP method is used to carry out multi-objective optimization design for the doublelayer vibration isolation system of the power pack.First of all,the vertical dynamic stiffness,lateral and vertical stiffness ratio,and longitudinal and vertical stiffness ratio of each vibration isolator are used as design variables,and the Monte Carlo sensitivity analysis method is used to perform sensitivity analysis on the design variables.The sensitivity coefficient of the stiffness is very small,and the vertical dynamic stiffness of the substructure can be ignored in the optimization design process,thereby reducing the number of environmental variables and achieving the purpose of improving the efficiency of the optimization design.Secondly,take the transfer rate and static balance as the constraint conditions,take the vibration intensity of the unit and the dynamic reaction force transferred to the foundation as the optimization objectives,and combine the dynamic equations of the power pack and the SQP method to optimize and calculate the dynamic stiffness of the double-layer vibration isolation system.The rigid-flexible coupling model of the power pack was established by ADAMS,and the vibration characteristics were analyzed based on the optimal dynamic stiffness.The results show that the vibration intensities of the unit are less than 28 mm/s,and all are in the A/B level;The dynamic reaction forces transmitted to the platform are less than 100 N;the vibration level drop values of the double-layer vibration isolation system are greater than 20 d B(the vibration isolation efficiency>90%),and the vibration isolation effect is excellent.Finally,A vehiclepower pack rigid-flexible coupling simulation model is established based on SIMPACK,and the influence of whether the train is excited by the power pack on the comfort of the car body is analyzed.The results show that the power pack’s excitation has the greatest impact on the comfort of the car body and the comfort index has increased by about 20% on average.The test of vibration intensity,vibration level drop and dynamic reaction force vibration was carried out on the power pack by the platform suspension method under no-load1000r/min and load 1000～1800 r/min.The test results show that under all working conditions,the vibration intensities of the unit are less than 28 mm/s,all in A/B level;the dynamic reaction forces transmitted to the platform are less than 100 N;the vibration level drop values of the double-layer vibration isolation system are all More than 20 d B,the vibration isolation effect is excellent.That shows the design of the vibration isolation optimization method is reasonable,which provides a guiding basis for the practical application of power pack vibration isolation design in engineering.