Analysis On The Operation Performance Of Heavy Haul Trains Under Different Operating Modes

In recent years,the rapid development of economy and the growing demand of transportation capacity are pushing our heavy haul development towards large axle load and long group.Long and heavy haul train means train braking wave transmission needs longer time and the longitudinal impulse of the train cannot be ignored.For complex terrain and more mountains in our country,the heavy load railway has to adopt the big ramp and small curve to overcome the terrain level difference.If braking under the complex line conditions,the longitudinal impulse of the train will aggravate the interaction between wheel and rail,which becomes the main risk source of driving safety.It is of great significance to study the performance of heavy haul trains on the curve section of the long steep downgrade.A dynamic model of heavy haul train is developed in this paper to simulate the performance of the curve section of the long steep downgrade.Based on the analysis of the performance of heavy haul trains on the condition of service braking,emergency braking and cyclic braking,this paper gives the recommended value of curve radius on the long steep downgrade.The research results are as follows:(1)Based on the multi-body dynamics and train longitudinal dynamics,considering the characteristics of train air brake and the hysteretic characteristics of the buffer,the train longitudinal dynamics model,the space wagon model and the longitudinal,transverse and vertical hybrid train dynamics model are established.The correctness of the model is verified,which provides a scientific method for the analysis of the performance of the heavy haul trains on the curve section of the long steep downgrade.(2)Under the braking condition,the position of the maximum coupler force of the train is not consistent with the position of the maximum coupler force on the curve and the two values are quite different.Under this condition,the train is running with different load in front and rear,and in the state of torsion on the track plane.The front bogie is lifted and the rear bogie is extruded on the condition of service braking and emergency braking,while on the condition of cyclic braking the front bogie is extruded and the rear bogie is lifted.Comparing with the performance without the longitudinal impulse,it is found that the longitudinal impulse caused by the train braking aggravates the interaction between wheel and rail and the emergency brake is most obvious.Under the condition of 13‰ downhill and 500m curve radius,the wheel rail lateral force increases by 28%,the derailment coefficient increases by 33.3%,the overturning coefficient increases by 55.6%,and the wheel load reduction rate increases by 100%.(3)Analyze the influence of radius of circular curve on driving performance.When the curve radius is less than 800m,considering the longitudinal impulse and without considering the longitudinal impulse,the changes of dynamic indexes are larger.While curve radius is larger than 800m,the changes of dynamic indexes in these two cases tend to be gentle.Considering the improvement of the running safety and mitigating the curve disease,800m is suggested to be the minimum curve radius of the long steep downgrade.