群组列车前后车间距对重载列车气动特性影响

Impacts of inter-train distances on aerodynamic drag reduction in heavy-haul train groups

群组列车小间距运行是未来重载铁路运输的潜在发展方向。文章采用计算流体力学方法,基于SST k-ω湍流模型,分析了群组列车前后间距对后方列车气动性能的影响。首先,进行算法验证,并与在中国空气动力与研究发展中心大型低速风洞进行的风洞试验结果进行比对,误差为3.4%,数值模拟得到的数据与风洞试验数据吻合较好。随后,进行网格无关性验证,选取了粗、中、细等3种网格划分方式进行仿真,粗网格误差较大,而在中等网格与细网格2种条件下,整车所受气动阻力变化小于3%,可认为这2种网格精度满足仿真计算要求,结果具有可靠性。最后,对2列重载列车在6种不同间距下进行了数值模拟及其分析。研究发现,随着车间距的缩短,前车对后车的气动优化效应逐渐显现,后方车辆整体气动阻力系数降幅达16%,其中机车部分减阻率达到17%,拖车部分减阻率为14%。前车尾部形成的低速尾流区是减阻的主要原因。对比不同车间距发现,当车间距大于700 m时,减阻效应不明显;当车间距小于200 m时,减阻效果无显著改善。综上所述,群组运行间距小于700 m时将优化后方列车的气动特性,并在间距缩减至200 m时达到最优减阻效果。

The operation of trains in groups at short distances represents a potential trend for the future development of heavy-haul railway transport.This paper analyzes the impacts of inter-train distances in this operational mode on the aerodynamic characteristics of trailing trains,using computational fluid dynamics(CFD)methods,based on the SST k-ωturbulence model.Initial algorithm validation was performed,and the results were compared with data from wind tunnel experiments conducted in a large low-speed wind tunnel at the China aerodynamics research and development center.The comparison indicated an error of 3.4%,suggesting a close alignment between the numerical simulation data and the results from the wind tunnel experiments.In the subsequent grid independence verification,three gridding methods were selected for simulations:coarse,medium,and fine grids.Apparent errors were observed in the coarse grid config-uration,while variations in aerodynamic drag acting on the whole train were less than 3%for the medium and fine grids.Therefore,the latter two levels of grid accuracy were considered conforming to simulation calculation requirements,making the corresponding results reliable.Further numerical simulations and analyses were conducted,using two heavy-haul trains at six different spacings.The study re-vealed that as the inter-train distance decreased,the aerodynamic optimization effect from the leading train on the trailing train gradually became apparent,with the overall aerodynamic drag coefficient of the trailing train decreasing by up to 16%.Specifically,the drag reduc-tion rate for the locomotive reached 17%,and that for the trailers was 14%.The main reason for drag reduction was identified as the low-speed wake zone formed at the rear of the leading train.Comparisons at different inter-train distances showed that the drag reduction ef-fect was minimal at distances greater than 700 meters,while no significant improvement in drag reduction effect was observed at distanc-es less than 200 meters.In summary,optimization of aerodynamic characteristics for trailing trains in group operation occurs at spacings of less than 700 meters,achieving the optimal drag reduction effect when the spacing is reduced to 200 meters.