Research On The Running Safety Of Middle Locomotive Of Combined Heavy Haul Train

For combined heavy haul train, the operating environment of middle locomotive is relatively poor, excessive longitudinal impulse is easy to cause the train derailment, sturcture failure, uncoupling separation and other safety accidents. Investigation results also indicated that coupler and buffer system has important effects on the running safety of heavy haul train. In order to analyze the running safety of middle locomotive of combined heavy haul train under different conditions, the dynamic model of ND coupler has been build up based on the theoretical analysis and structure character of coupler in this paper firstly, then established the dynamic model of short marshalling train which composed of middle locomotive and its adjacent gondola car by substructure method, qualitative analysis the matching relationship between the locomotive and coupler through the short marshaling model, and introduced the detail short marshaling train model to simplified longitudinal dynamics model of train finally, thus formed the dynamic model of train which could reflect the dynamic characteristics of middle locomotive and dynamic behaviors of coupler and buffer system. Analyzed the longitudinal impulse distribution of combined heavy haul train under different working conditions and its effect on the running safety of middle locomotive by simulation methods.The main work and conclusions are shown below:1. Analyzed the friction condition of ND coupler’s tail in theory based on classical friction law, the results show that the stability of ND coupler mainly depends on the friction state of coupler tail, and the theoretical calculation formula of the coupler critical rotation angle has been deduced. The couper in the steady state when its rotation angle is less than the critical value, when the coupler rotation angle exceeds the critical value, the friction surface of coupler tail is easy to cause relative sliding with the longitudinal compressive force, and lead to the unstability of coupler;2. It can be seen from the qualitative analysis about the safety of the locomotive when bearing longitudinal compressive strength, the friction state of coupler tail has great influence on the compressive stability of ND coupler, improve the friction coefficient of coupler tail could improve compressive stability of ND coupler effectively. In addition, change the structure parameters of locomotive and coupler and buffer system reasonably could limit the rotation behavior of coupler, so it should take full account of the matching rationality between locomotive and coupler and buffer system in the design phase;3. The simulation analysis of combined heavy haul train shows that ensure the compressive stability of coupler is the precondition to ensure the operation safety of middle locomotive. But for the perspective of longitudinal dynamic of train, ensure the communication signal of train is stable and reliable, install the controlled EOT, avoid emergency brake when the train under tensile or low speed state could reduce the longitudinal impulse of train effectively;4. The simulation analysis of coupling coupler between locomotive and rolling stock shows that the coupling surface would generate the corresponding normal contact force and tangential friction force to limit the relative movement between the coupler knuckles when the coupler bearing tensile or compressive force, it is easy to cause uncoupling separation accident between locomotive and rolling stock by the relative vibration and the larger vibration caused by track irregularities when the coupling coupler in a state of loose clearance, but from the simulation results, this kind of accident has certain chanciness, this accident phenomenon could be avoided effectively by reduce the coupler height difference between vehicles, set anti-separation stop in the bottom of coupler knuckle and other measures.