【作者】 张勇；

【导师】 郑珺； 邓自刚；

【作者基本信息】 西南交通大学 ， 车辆工程， 2019， 硕士

【摘要】 “创新是一个民族进步的灵魂,也是一个国家兴旺发达的不竭动力。”轨道交通领域内持续的技术创新,是保证轨道交通产业良好可持续发展的前提。轮轨列车因其具备网络化、大运量、安全、高效等特点,在中长途、中高速运输领域极具优势。但受空气阻力、轮轨黏着、蛇行失稳、运行噪声以及弓网极限速度等问题的制约,轮轨列车的运营速度很难有显著的提升。而结合磁悬浮技术和低真空管道技术的低真空管道磁浮运输系统,利用封闭低真空管道创造独特的低阻运行环境,使得“时速1000公里的超高速近地面飞行”成为可能。理论上,低气压运行环境会在一定程度上减弱管内气流与列车的相互作用,但列车极高的运行速度则有可能带来与之对立的影响。作为一种超高速交通工具,空气动力学问题是研发低真空管道磁浮运输系统首要面临的问题,气动特性与列车的安全性以及平稳性息息相关。因此,本论文系统分析了低真空管道磁浮运输系统的流场特征,推导了列车在低真空管道中匀速运行的气动阻力计算式。发现管道内运行的列车的气动阻力主要与管道气压、列车运行速度、阻塞比、列车长度以及管道、列车表面当量粗糙度,管道断面形式等参数有关。其次,采用三维、sutherland粘性、定常、可压缩的N-S方程和Realizable k-ε双方程湍流模型,在ANSYS FLUENT建立了低真空管道磁浮运输系统气动特性数值计算模型。对比研究了明线运行条件和低真空管道运行条件下列车的气动阻力,并分析了列车运行速度、阻塞比、管道气压对列车气动阻力的影响。结果表明,明线条件下,列车气动阻力主要来源于头车和尾车的压差阻力,中间车主要以摩擦阻力为主,列车速度达到980 km/h时的气动阻力竟达到143.34 kN,约为时速350 km/h高铁阻力的6-7倍;低真空条件下,列车的气动阻力与速度的平方成正比,且随着管道气压的增大而增大,近似成线性关系,随着阻塞比的减小而减小,气动阻力与阻塞比呈非线性关系;此外,考虑到能耗和牵引力极限,研究表明,要实现目标速度1000 km/h,经济合理的阻塞比应为0.32左右,管道气压应在0.01 atm附近甚至更低。此外,论文第四章研究了列车速度和管道气压对车身外表面和管道内壁面气动荷载的影响。研究表明,气动荷载随着列车速度的增大而增大,随着管道气压的减小而急剧减小。在低真空管道内运行的列车车头表面压力较大,中车表面气动压力变化较为平缓,在临近车尾处压力相对于管道内气压有所降低。对于管道壁面气动荷载而言,管道内壁面压力在列车前方较管道内初始气压值急剧增大,在列车后方较管道内初始气压值有所减小,在达到峰值后逐渐恢复至管道初始气压值。因此,降低低真空管道内的初始气压和列车运行速度,能够显著减小列车外表面和管道内壁面的压力值。最后,论文第五章研究了不同管道断面形式以及横通道对列车气动阻力和系统气动荷载的影响。结果表明,当管道气压降低至0.01 atm,阻塞比均为0.32时,不同管道断面形式下,管道壁面气动荷载变化规律基本相同,管道断面形式对系统气动荷载的影响不大。其次,列车在矩形管道内运行的气动阻力最小,以0.8 Mach运行时的阻力为10.76 kN,和在圆形管道内行驶的气动阻力基本相当,在拱形管道内的气动阻力最大。此外,通过设置横通道,可以在一定程度降低列车的气动阻力,降低头车和中车外表面的气动荷载,但对尾车作用则不太明显。当管道气压为0.01 atm,阻塞比为0.32时,列车在带横通道的管道中以0.8 Mach行驶的阻力可以进一步减小为9.877 kN。此外,设置横通道能够降低管道内壁面的最大气动荷载压力值,但在横通道的设置处则会带来一定的压力波动,波动幅值小于管道内壁面的最大气动荷载变化。更多还原

【Abstract】 Innovation is the soul of a nation’s progress,and it is also the inexhaustible driving force for a country’s prosperity.As for the field of rail transit,continuous technological innovations are the premise to ensure the favorable and sustainable development of the rail transit industry.Due to its network,large volume,safety,efficiency and other characteristics,the wheel-rail trains have great advantages in the field of medium and long distance,medium and high speed transportation.However,it is difficult to improve the operation speed of the wheel-rail train significantly,due to the inevitable limits,such as aerodymanic drag,wheel-rail adhesion,hunting instability,running noise and the limiting speed of pantograph-catenary.The maglev transport system with low-Pressure tube(LPT-MT system),which combines magnetic levitation technology with a low-pressure tube,can create a unique low-drag operation environment by using a closed low-pressure tube,making it possible for ―flying near-ground with 1000 km/h‖.Theoretically,although the interaction between the air flow and the train will be reduced to some extent under the low-pressure envirionment,the ultra-high running speed of the train may bring some negetive effect.Aerodynamics is the primary problem for the research and development of LPT-MT system deemed as an ultra-high speed transport,and aerodynamic characteristics are closely related to the safety and stability of the train.Therefore,the flow field characteristics of the LPT-MT system were analyzed systematically in this paper,and the formula of aerodynamic drag of the train was conducted when it was running inside the low-pressure tube at a constant speed.It was found that the aerodynamic drag of the train running in the tube,is mainly related to the pressure in the tube,velocity and length of the train,block ratio,the equivalent surface roughness of the train and tube,the tube section forms and other parameters.Then,a three-dimensional,sutherland viscous,steady-state compressible N-S equation and a realizable k-ε two equation turbulence model were used to numerically calculate the aerodynamic characteristics of the LPT-MT system in ANSYS FLUENT software.The aerodynamic drag of the maglev train under the condition of open air and low-pressure tube is studied,and the influence of block ratio,velocity of the train and tube pressure were analyzed as well.It turns out that the aerodynamic drag of the train mainly comes from the pressure drag between the head car and the tail car when the train is running in the open air condition,and the mid car mainly produce frictional drag.When the train speed reaches 980 km/h,the aerodynamic drag reaches 143.34 kN unexpectedly,which is about 6-7 times than the aerodynamic drag of high speed railway under 350 km/h.When the train is running in the low-pressure tube,the aerodynamic drag of the train is directly proportional to the square of the speed,and increases with the tube pressure linearly,and it also decreases with the decrease of the blocking ratio non-linearly.In addition,considering the energy consumption and traction power limit,the study shows that,if you want to achieve the target speed of 1000 km/h,the economical and reasonable block ratio should be about 0.32,and the tube pressure should be around 0.01 atm or even lower.In addition,the fourth chapter studies the influence of the train speed and tube pressure on the surface of the train and tube wall.It shows that the aerodynamic load increases with the train speed and tube pressure.When the train is running in the low-pressure tube,the load on the head car surface is very large,while the load on the mid car surface is relatively flat,and the load on the tail is small even less than the initial tube pressure.As for the aerodynamic load on the tube wall,they increased sharply in front of the train,and decreased in rear of the train,compared with the initial tube pressure,then,returned to initial tube pressure gradually after the fluctuated peak.Therefore,reducing the initial pressure in the tube and the speed of the train,can significantly decrease the aerodynamic load on the external surface of the train and the inner wall of tube.Finally,the fifth chapter studies the influence of different tube section forms and cross aisle on the aerodynamic drag of the train and aerodynamic load in the system.It was found that the aerodynamic loads on the inner tube wall are basically the same even under different tube sections forms,and the tube section forms has little influence on the aerodynamic load of the system,when the tube pressure is 0.01 atm and block ratio is 0.32.The aerodynamic drag of the train is the minimum when running in the rectangular tube.When the train speed is 0.8 Mach,the drag is 10.76 kN,which is basically the same as that running in the circular tube,and when the train is running in the archy tube,the aerodynamic drag is the maximum.In addition,by setting the cross aisle,the aerodynamic drag of the train can be reduced to some extent,and the aerodynamic load on the external surface of the head and the mid can be reduced,however,such effect is helpless on the tail.When the tube pressure is 0.01 atm and the block ratio is 0.32,the aerodynamic drag of the train in the tube with cross aisle can be reduced further to 9.877 kN,even the speed of the train is 0.8 Mach.In addition,setting cross aisle can reduce the the maximum aerodynamic load on the inner wall of the tube,but it also bring some pressure fluctuation at the location of cross aisle,and the fluctuation amplitude is smaller than the maximum aerodynamic load variation.更多还原