Study On Optimum Design Of Vibration Isolation Performance Of Diesel Locomotive Cab Under Excitation Of Diesel Engine

Diesel locomotives occupy an important position in railway transportation in China,and are still irreplaceable,especially in many secondary trunk lines,special lines and shunting operations.It is necessary to convert the chemical energy of fuel into electric energy and transfer the electric energy to traction motor to drive diesel locomotive to run along the track.However,the diesel engine and the main generator connected with the diesel engine in the locomotive will produce intense internal dynamic excitations due to the impact of combustion and explosion in cylinder,reciprocating motion of piston parts,and high-speed rotation of rotating parts.And then,the vibrations of diesel engines and main generator stimulated by these dynamic excitations mentioned above will be transmitted to the cab through the chassis of the car body,which could causes high-frequency vibration and acoustic problems in the cab,greatly reduces the comfort of the cab,deteriorate the working environment and harm the health of the cab crew.In addition,some adverse effects have been brought to drivers' safe and efficient driving,as well as drivers' scientific and reasonable response to emergencies consequently.Therefore,designing scientific and reasonable cab suspension structure and its parameters is of great theoretical significance and engineering application value to reduce cab vibrations,as well as improving driving comfort,working environment and driving safety.Diesel locomotive cab and chassis are usually rigidly connected in the early years,which resulted in poor isolation effect due to that the vibration generated by diesel engine-main generator is transmitted directly to the cab.In recent years,with the application of isolated cab,the vibration of the locomotive cab has been effectively controlled.While,how to scientifically and reasonably design the dynamic parameters and layout of the cab vibration isolation system to achieve the best vibration isolation effect has always been the main issue in both academic and business circles.A series of research work has been carried out on the optimization design of cab vibration isolation for diesel locomotives,and a multi-degree-of-freedom decoupling optimization design method for cab vibration isolation of diesel locomotives based on the biogenetic algorithm is proposed in this paper.Primarily,a 6-DOF dynamic analysis model of the cab is established based on the vibration isolation structure of diesel locomotive cab.Meanwhile,the vibration isolation performance of the cab under the initial parameters of the isolator is evaluated from the aspects of frequency matching and vibration decoupling.In addition,the frequency characteristics of diesel engine vibration are analyzed through the tested vibration data of the diesel engine,and the excitation frequency in the design of cab vibration isolation is defined.Additionally,modal analysis of locomotive chassis is also carried out,which provides a reference for frequency matching of cab vibration isolation system.Secondly,the optimization objective function is designed based on matching the natural frequencies of the cab isolation system and decoupling the degrees of freedom of the dynamics system.After that,the location and stiffness of the cab isolator are optimized by using the biogenetic algorithm.Eventually,the whole cab model of diesel locomotive including cab is established and the cab vibration response under different gear and different parameters of cab isolator is calculated and analyzed based on the whole cab model.By contrast,the optimized cab vibration isolation performance is also analyzed.The results show that:(1)reasonable arrangement of the isolator position in the cab of diesel locomotive can effectively reduce the coupling effects between the degrees of freedom of the cab and is conducive to the rational allocation of the natural frequency of cab vibration;(2)the vibration isolation optimization results obtained by using the proposed multi-degree-of-freedom decoupling optimization method based on the biogenetic algorithm are better than those of the traditional single-degree-of-freedom optimization method,and the vibration level of the cab after optimization is obviously improved compared with that before optimization;(3)the optimization method and results of vibration isolation proposed in this paper can provide some theoretical guidance for the vibration isolation design of diesel locomotive cab.