| With the rapid development of our country’s economy,the technology of railway heavy haul transportation is constantly improving.But because of the group leader and heavy haul train load,there will be great longitudinal impulse in the operation process.It is also an important problem affecting the safe operation of trains.The longitudinal impulse of train is affected by many factors,among which the characteristics of air braking system have a great influence.Therefore,it is of great significance to study the braking characteristics of train for improving the longitudinal dynamic performance of heavy-duty train.In this paper,by analyzing the causes of longitudinal impulse action of 20,000 tons train,the braking characteristics of train were analyzed,and the changing law between the maximum coupler force and the divergence degree of brake cylinder pressure of train under different pressure reduction was studied.On this basis,the influences of changing slave control locomotive and tail-train lag time,master-slave control locomotive exhaust speed and controllable tail-train exhaust speed on train braking characteristics and longitudinal impulse under different decompressure of common braking were analyzed,and the measures to reduce the divergence degree of brake cylinder pressure were proposed.The influence of piston travel length of brake cylinder on the longitudinal dynamic performance of the ten kiloton and twenty kiloton train under four working conditions of decompression 50 k Pa braking,common full braking,emergency braking and decompression 50 k Pa rerelief was simulated and analyzed.The calculation results show that the coupler force in the braking process of the20,000-ton train is mainly the hook force generated by extrusion,which is caused by the influence of the braking wave propagation characteristics of the train and the boost characteristics of the brake cylinder,the brake cylinder pressure between vehicles will have a great difference.Changing the lag time of slave locomotive and train tail,exhaust speed of master-slave locomotive and controllable exhaust speed of train tail will affect the propagation characteristics of train brake wave.The shorter the lag time of slave control locomotive and train tail,the slower the exhaust speed of master-slave control locomotive and the faster the exhaust speed of controllable train tail,the smaller the maximum hook force generated during train braking,and the smaller the divergence degree of brake cylinder pressure at the moment when the maximum hook force is generated.The length of piston stroke of brake cylinder has great influence on the longitudinal dynamic performance of train.When the piston stroke of brake cylinder is uniformly distributed,the longer the piston stroke of brake cylinder,the smaller the maximum coupler force of train and the weaker the braking capacity.When the piston stroke of 190 mm is compared with 145 mm,the maximum coupler force of 10,000 tons and 20,000 tons train is reduced by 33.4% and 35.9%,respectively.Braking distance increased by 34.1% and 36.8%,respectively;The maximum retractor force decreased by 44.1% and 55.8%,respectively,when decompressed by 50 k Pa and relieved.Under the differential distribution of piston stroke before and after the brake cylinder,the maximum hook force of the first half train with a longer piston stroke and the second half train with a shorter piston stroke decreased by 23.9% and 26.4%,respectively,compared with the first half train with a shorter piston stroke and the second half train with a longer piston stroke.The braking distance increased by 1.5% and 2.7% respectively.When decompression was 50 k Pa and then relieved,the maximum retracting force of 10,000 tons train was reduced by 7.5%,and the maximum retracting force of 20,000 tons train was basically unchanged. |
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