| Due to the open operating environment,railway transportation is prone to the pollution of the third medium such as water,oil,leaves and so on,which leads to the problem of low adhesion.In order to ensure the safety of the train under the condition of low adhesion,sanding is widely used to improve the adhesion level on railway.Due to the particle loss in the process of sanding,the amount of particles from sanders and the amount of particles entering the wheel/rail interface vary significantly.Therefore,it is of great guiding significance for further optimization and regulation of sanding application to study the dynamic process of sanding and clarify the influence rules of different factors on utilization efficiency of particles.According to the relative motion of the wheel and rail in the train movement,an experimental test device for simulating the train sanding process was designed.Based on this device,the jet behavior and the utilization efficiency of particles were studied.The influence rules of different application parameters on the sanding process were obtained.The main conclusions are as follows:(1)A 1:1 full-size train sanding process simulation test device was designed and developed,which could simulate and test the utilization efficiency of particles under conditions of the train running speeds of 0～120km/h and the cross wind speeds of 0～15m/s.On the basis of the device,the visual detection function of the sanding process was realized by using high-speed camera and image processing technology,which could dynamically detect the sanding process under different parameters,including different train speeds,cross wind speeds,types of sanders,nozzle installation positions,particles,particle jet speeds,etc.(2)In the process of particle injection,with the decrease of particle size,both the particlejet velocity and the sanding flow rate increased.The diffusion angle of the jet was related to the movement form of particles in the tube.With the increase of the jet velocity of particles,the movement form of particles experienced the transition from flow with fixed bed,jump flow,non-uniform flow to uniform flow,and the diffusion angle decreased accordingly.(3)In the process of particle injection,due to the influence of cross wind,the particle trajectory had a certain lateral offset.With the increase of the speed of cross wind,the deviation degree of the trajectory of particles increased.The small particles was affected more significantly.When the velocity of transverse wind was high(15 m/s),the trajectory of some XS particles were changed from longitudinal to nearly transverse(the maximum deviation angle was 81.8°).Large particles were less affected.The trajectory was not easy to change(the maximum deviation angle was 40.4°).When the jet velocity of particles was greater than that of the transverse wind,the lateral migration of particles was not obvious.(4)Under the condition without cross wind,the smaller the particle size,the higher the jet velocity and the smaller the jet diffusion angle,the higher the efficiency of particles.The utilization efficiency of particles was higher when the nozzle was towards the rail than towards the wheel-rail contact point.Under the condition with cross wind,when the velocity of cross wind was close to the jet velocity of particles,the utilization efficiency of small particles was higher.When the velocity of cross wind was greater than the jet velocity of particles,the utilization efficiency of small particles decreased rapidly with the increase of cross wind velocity,while the efficiency of large particles decreased slowly and was higher than that of small particles.(5)During the train sanding process,the ranking of absolute value of correlation coefficient of particle utilization rate was as follows: ratio of cross wind velocity to particle jet velocity > jet diffusion angle > particle jet velocity > particle size.Therefore,the utilization efficiency can be improved by increasing particle jet velocity,reducing jet diffusion angle and selecting appropriate particle size. |
