The Study Of Sensitivity Analysis And Optimized Design Of Vibration Isolation Parameter Of Powerpack In Diesel Railcar

As an important part of the diesel motor car,the design of vibration isolation parameter of the power pack directly affects the operation status of the vehicle system.Due to the large number of vibration isolation parameter and the large coupling effect among the components,the design efficiency of the vibration isolation parameter of the two-stage vibration isolation system of the power pack is low.For this reason,the global sensitivity analysis method is introduced into the design of the vibration isolation parameter of the power pack in this thesis.The main parameters that affect the vibration isolation performance of the power pack system are determined and used as optimization variables to optimize the vibration isolation parameter of the power pack,which effectively reduces the number of design variables and improves the design efficiency.To reduce the number of variables in the vibration isolation design of the power pack,the mathematical model of the power pack structure of a two-stage vibration isolation system is established.The function expression of the unit’s vibration intensity and the vibration isolation efficiency of the system is derived,and the global sensitivity analysis of the vibration isolation parameter of the power pack is carried out by using the Sobol method.The results show that for the vibration intensity of the unit and the isolation efficiency of the system,the sensitivity of the lateral vertical ratio(the ratio of the lateral stiffness to the vertical stiffness of the vibration isolator),the longitudinal vertical ratio(the ratio of the longitudinal stiffness to the vertical stiffness of the vibration isolator),the vertical stiffness of the four secondary vibration isolators on the frame and the three primary vibration isolators on the unit are high.The parameters mentioned above are taken as design variables of vibration isolation design of the power pack,and 13 design variables in the original design are reduced to 9.Based on the results of the sensitivity analysis of the vibration isolation parameter of the power pack,nine main parameters that affect the vibration isolation performance are taken as the optimal variables of the optimal design of the power pack.Then,to prevent the power pack from overturning too much and avoid the resonance of the power pack system,the static balance condition and the matching relationship between the system modal frequency and the excitation frequency are taken as the constraints.The vibration isolation efficiency of the system and the unit’s vibration intensity are taken as the optimal objectives to carry out the multi-objective optimal design for the vibration isolation parameter of the system.The results show that the vibration isolation performance of the optimized power pack has been improved to a great extent compared with the original system,especially at no load of 1000 r/ min,the improvement of the vibration intensity and the unit’s vibration isolation efficiency of the power pack is obviously large,and the improvement rate reaches 12% and 29.61%,which verifies the reliability of the optimization method.To test whether the vibration intensity and vehicle comfort of the optimized power pack structure can meet the standard requirements when it is placed under the vehicle,based on the the optimized vibration isolation system,the vehicle-power-pack rigid-flexible coupling model is established.The vibration characteristics of the rigid-flexible coupling model are analyzed,and the vehicle comfort and the unit’s vibration intensity are calculated under the working condition of the power pack.The results show that the unit’s vibration intensity of the power package under all operating conditions is less than 0.018 m/s,which is above level B,and the comfort index of the three positions is less than 1,which is very comfortable.It proves the rationality of the two-stage vibration isolation system design method of the power package.To verify whether the vibration intensity of the unit and the vibration isolation efficiency of the system can meet the engineering requirements in practical application,the test process of the power-pack ground platform experiment is introduced at the end of this thesis,and the acceleration time-domain signal of the corresponding test point is measured.Finally,the experimental data are processed by the numerical program,and the experimental results of the unit’s vibration intensity and vibration isolation efficiency of the system are obtained.The results show that the vibration intensity of the unit is less than 0.018 m/s in all working conditions,which is above level B,and the vibration isolation efficiency of the system is also above 85%,that is to say,the designed power pack system meets the engineering requirements.In addition,the simulation results of the unit’s vibration intensity and vibration isolation efficiency of the power package have a little deviation from the experimental results,and the trend of the simulation results of the two indexes are similar to the experimental results with the change of the working conditions,which verifies the accuracy of the model and the rationality of the optimization design method.The optimal method of powerpack’s vibration isolation parameter in this thesis can be used in the engineering practice,which can guide the powerpack’s design.