Effect of Streamlined Nose Length on the Aerodynamic Performance of a 800 km/h Evacuated Tube Train

The aerodynamic resistance of a train running in the open air limits the maximum speed that can be attained by the train.For this reason,evacuated tube trains(ETT)are being considered as valid alternatives to be implemented in the future.The atmosphere in the tube,the so-called blocking ratio and the length of the streamlined nose are the key factors affecting the aerodynamic performances of these trains.In the present work,we investigate evacuated tube trains with different lengths of the streamline nose on the basis of computational fluid dynamics(CFD).The three-dimensional steady compressible Navier-Stokes equations are solved.The running speed of the ETT is 800 km/h and the blocking ratio is 0.2.Results show that with the increase of the streamlined nose length,the aerodynamic drag and lift forces of the head car decrease gradually,and the drag and lift forces of the middle car change slightly.For the tail car,the drag force decreases,whereas the absolute value of the lift force increases.At a speed of 800 km/h,a slight shock wave appears at the rear of the tail car,which affects the aerodynamic forces acting on the train.

Aerodynamic Design of a Subsonic Evacuated Tube Train System

The so-called Evacuated Tube Train(ETT)is currently being proposed as a high-speed transportation system potentially competitive with airplane transportation.Aerodynamic resistance is one of the most crucial factors for the successful design of an ETT.In the present work,a three-dimensional concept ETT model has been elaborated.The aerodynamic characteristics of the subsonic ETT have been numerically simulated under different conditions.The train’s running speed varies from 600 km/h up to 1200 km/h,and the blockage ratio is in the range between 0.1 and 0.3.As the blocking ratio and running speed increase,the resistance of the head car increases greatly,while the resistance of the middle car changes slightly.The aerodynamic resistance of the tail car is affected by the shock wave emerging in the wake flow.Two different design criteria for the maximum allowed aerodynamic resistance are proposed for aerodynamic parameter matching.With an increase in the blockage ratio and running speed,the atmospheric pressure in the tube should be decreased to achieve a balance.

An Aerothermal Study of Influence of Blockage Ratio on a Supersonic Tube Train System

Evacuated tube transportation is an important development direction for the high-speed transportation technology of the future.However,a train running at supersonic speed in a closed tube can create an unstable aerothermal phenomenon,causing the temperature to rise sharply inside the tube and endangering the safe operation of trains and equipment.The blockage ratio is one of the key factors affecting the aerodynamic characteristics in the tube.In this paper,a 2 D axisymmetric model and Delayed Detached Eddy Simulation(DDES)based on the Shear Stress Transport(SST)k-ωturbulence model are used to study the aerothermal environment in the tube.The calculation method used in this paper was verified by a wind tunnel experiment.The aerothermal phenomenon and distribution of the flow field in the tube with different blockage ratios were compared and analysed.The results show that the aerothermal environment is significantly affected by the blockage ratio.A choking limit formed in the flow field will aggravate the aerodynamic phenomenon as the blockage ratio increases,which further deteriorates the aerothermal environment of the tube.Moreover,the existence of the choking limit,shock wave,and Mach disk make the flow field in the tube more complicated.

Numerical study on the influence of initial ambient temperature on the aerodynamic heating in the tube train system

The evacuated tube transportation has great potential in the future because of its advantages of energy saving and environmental protection.The train runs in the closed tube at ultra-high speed.The heat quantity generated by aerodynamic heating is not easy to spread to external environment and then accumulates in the tube,inducing the ambient temperature in the tube to rise gradually.In this paper,a three-dimensional geometric model and the Shear Stress Transport(SST)κ-ωturbulence model are used to study the influence of initial ambient temperature on the structure of the flow field in the tube.Simulation results show that when the train runs at transonic speed,the supersonic flow region with low temperature and low-pressure is produced in the wake.The structure of the flow field of the wake will change with the initial ambient temperature.And the higher the initial ambient temperature is,the shorter the low temperature region in the wake will be.The larger temperature difference caused by the low temperature region may increase the temperature stress of the tube and affect the equipment inside the tube.Consequently,the temperature inside the tube can be maintained at a reasonable value to reduce the influence of the low temperature region in the wake on the system.

Aerodynamic simulation of evacuated tube maglev trains with different streamlined designs

Based on the Navier-Stokes （N-S） equations of incompressible viscous fluids and the standard k-ε turbu- lence model with assumptions of steady state and two dimensional conditions, a simulation of the aerodynamic drag on a maglev train in an evacuated tube was made with ANSYS/FLOTRAN software under different vacuum pressures, blockage ratios, and shapes of train head and tail. The pressure flow fields of the evacuated tube maglev train under different vacuum pressures were analyzed, and then compared under the same blockage ratio condition. The results show that the environmental pressure of 1 000 Pa in the tube is the best to achieve the effect of aerodynamic drag reduction, and there are no obvious differences in the aerodynamic drag reduction among different streamline head shapes. Overall, the blunt-shape tail and the blockage ratio of 0.25 are more efficient for drag reduction of the train at the tube pressure of 1 000 Pa.

The approach to calculate the aerodynamic drag of maglev train in the evacuated tube

In order to study the relationships between the aerodynamic drag of maglev and other factors in the evacuated tube, the formula of aerodynamic drag was deduced based on the basic equations of aerodynamics and then the calculated result was confirmed at a low speed on an experimental system developed by Superconductivity and New Energy R＆D Center of South Jiaotong University. With regard to this system a high temperature superconducting magnetic levitation vehicle was motivated by a linear induction motor （LIM） fixed on the permanent magnetic guideway. When the vehicle reached an expected speed, the LIM was stopped. Then the damped speed was recorded and used to calculate the experimental drag. The two results show the approximately same relationship between the aerodynamic drag on the maglev and the other factors such as the pressure in the tube, the velocity of the maglev and the blockage ratio. Thus, the pressure, the velocity, and the blockage ratio are viewed as the three important factors that contribute to the energy loss in the evacuated tube transportation.

Numerical simulation and analysis of aerodynamic drag on a subsonic train in evacuated tube transportation

The aerodynamic drag on a train running in an evacuated tube varies with tube air pressure, train speed and shape, as well as blockage ratio. This paper uses numerical simulations to study the effects of different factors on the aerodynamic drag of a train running at subsonic speed in an evacuated tube. Firstly, we present the assumption of a steady state, two dimensional, incompressible viscous flow with lubricity wall conditions. Subsequently, based on the Navier-Stokes equation and the k-c turbulent models, we calculate the aerodynamic drag imposed on the column train with a 3-meter diameter running under different pressure and blockage ratio conditions in an evacuated tube transporta- tion （ETT） system. The simulation is performed with FLUENT 6.3 software package. An analyses of the simulation re- sults suggest that the blockage ratio for ETT should be in the range of 0.25-0.7, and the tube internal diameter in the range of 2-4 m, with the feasible vacuum pressure in the range of 1-10 000 Pa for the future subsonic ETT trains.

A study on characteristics of shock train inside a shock tube

Shock tubes are devices which are used in the investigation of high speed and high temperature flow of compressible gas. lnside a shock tube, the interaction between the reflected shock wave and boundary layer leads to a complex flow phenomenon. Initially a normal shock wave is formed in the shock tube which migrates toward the closed end of the tube and that in turn leads to the reflection of shock. Due to the boundary layer interaction with the reflected shock, the bifurcation of shock wave takes place. The bifurcated shock wave then approaches the contact surface and shock train is generated. Till date only a few studies have been conducted to investigate this shock train phenomenon inside the shock tube. For the present study a computational fluid dynamics （CFD） analysis has been performed on a two dimensional axi-symmetric model of a shock tube using unsteady, compressible Navier-Stokes equations. In order to investigate the detailed characteristics of shock train, parametric studies have been performed by varying different parameters such as the shock tube length, diameter, pressure ratio used inside the shock tube.

低真空管道列车关键气动问题研究进展

低真空管道列车系统结合应用了管道运输和磁浮推进技术,是一种颇具潜力的未来地面高速交通方式。列车在极狭长的管道空间内长距离往返,通常诱发以管内壅塞现象为主导的大尺度跨声速流动和多车干扰,导致气动阻力急剧增加和气动热环境恶化,从而面临突出的空气动力学问题。本文从管道全场和列车近场两个视角出发,对管道列车流动特征进行了总结,并对近年来国内外该领域气动力/热/噪声研究的进展进行了梳理。在此基础上,围绕管道列车全线多车运行热点问题,对运行速度、管道阻塞比、发车间隔、运行模式的选取进行了讨论。最后,展望了低真空管道列车气动研究领域未来发展方向,指出高效研究方法、多车运行流动干扰、多车运行气动热、长大管道气动噪声、减阻/降热/降噪技术等是今后需要重点研究的领域。

新型钢管混凝土枕式无砟轨道动力响应试验研究

采用钢管混凝土构件连接轨枕块形成钢管混凝土轨枕,基于钢管混凝土轨枕设计城市轨道交通用钢管混凝土枕式无砟轨道结构。为掌握钢管混凝土枕式无砟轨道结构在城市轨道交通列车运行条件下的力学性能,验证结构设计的安全性、合理性,分别在减振地段、普通地段铺设钢管混凝土枕式无砟轨道,通过行车试验,测试分析不同列车行驶速度下无砟轨道钢轨、轨枕、道床结构的动力响应。研究结果表明:在列车车速为40、60和80 km/h运行条件下,轮轨垂向力最大值为86.18 kN,横向力最大值为13.99 kN,脱轨系数最大值为0.21,轮重减载率最大值为0.23,测试值均明显小于相应的安全限值,无砟轨道结构满足行车安全性要求;在列车动荷载作用下,钢管混凝土轨枕钢管压应力最大值为3.55 MPa,拉应力最大值为3.77 MPa;轨枕块压应力最大值为1.32 MPa;道床钢筋压应力最大值为2.30 MPa,拉应力最大值为3.54 MPa;道床底压应力最大值0.22 MPa。这些动力响应结果均满足材料的的限值,表明结构保持了良好的力学性能,结构设计合理可行。

间歇经口至食管管饲法联合自创吞咽功能训练在脑卒中吞咽障碍患者的应用研究

目的探讨间歇经口至食管管饲法与自创吞咽功能训练联合应用于脑卒中吞咽障碍患者的效果。方法选取河南大学淮河医院2022年1月—2023年12月收治的50例脑卒中吞咽障碍患者,应用随机数字表法将其分为两组,每组各25例。对照组采取持续留置鼻饲的同时应用自创吞咽功能训练进行训练,观察组采取间歇经口至食管管饲的同时应用自创吞咽功能训练进行训练。对比两组吞咽障碍改善情况、干预前后营养状况指标及生活质量变化,比较两组并发症发生率。结果观察组总有效率高于对照组(P<0.05)。干预后两组血清总蛋白、白蛋白和血红蛋白水平和体质量指数均升高,观察组高于对照组(P<0.05)。干预后两组生活质量综合评定量表评分升高,观察组高于对照组(P<0.05)。观察组并发症发生率低于对照组(P<0.05)。结论对脑卒中吞咽功能障碍患者采取间歇经口至食管管饲法与自创吞咽功能训练,能够更有效改善患者吞咽功能,提升其生活质量,且可降低留置饲管营养支持过程中的并发症发生率。

基于传播图理论的真空管飞行列车的无线信道建模与容量分析

无线信道建模是分析和评估无线通信系统特性的重要环节。为了满足下一代轨道列车的通信需求,本文基于传播图信道建模理论,对真空管环境下列车在管道内运行过程中的无线电传播信道进行研究。结合朗伯散射模型和几何绕射理论模型进行仿真,过程中主要考虑了视距传输、单散射径、单散射加绕射三种情况。仿真得到了多输入多输出(multiple-input multiple-output,MIMO)条件下的信道传输矩阵,提取并分析了功率时延谱、K因子、多普勒谱和信道容量在列车处于不同位置时的变化情况,结果表明,所提出的模型有助于分析在真空管场景下MIMO系统的信道衰落特性和信道容量。

分析夹管训练结合渐进性盆底肌康复对前列腺增生术后患者睡眠质量的影响

目的:分析前列腺增生术患者实施夹管训练结合渐进性盆底肌康复对术后睡眠的改善效果。方法:选取2022年11月至2023年11月福州市长乐区人民医院泌尿外科收治的手术治疗前列腺增生患者94例作为研究对象,按照随机数字表法分为对照组和观察组,每组47例。对照组给予常规护理干预,观察组给予夹管训练结合渐进性盆底肌康复干预。采用失眠严重程度指数(ISI-C)比较2组患者的失眠发生情况,采用斯坦福嗜睡量表(SSS)比较2组患者干预前后嗜睡程度的变化,采用睡眠状况自评量表(SRSS)比较2组患者的睡眠质量,比较2组患者的控尿功能,包括统计术后日漏尿次数、日排尿次数以及恢复控尿时间,并通过尿动力学分析仪监测2组患者的尿动力学指标,记录最大膀胱容量、膀胱初感容量、最大尿流率。结果:干预后,观察组SSS评分、ISI-C评分、SRSS评分均显著低于对照组,观察组最大膀胱容量、膀胱初感容量、最大尿流率均显著高于对照组,观察组日漏尿次数、日排尿次数以及恢复控尿时间均显著低于对照组,差异均有统计学意义(均P<0.05)。结论:对前列腺增生术患者实施夹管训练结合渐进性盆底肌康复可加快恢复控尿功能,改善尿动力学指标,有助于缓解嗜睡程度和失眠症状,提高睡眠质量,值得推广应用。

一种新型抗冲击曳光管设计与验证

根据某型现代小口径高炮武器系统曳光训练弹的研制要求,设计了一种新型抗冲击曳光管,对曳光管壳、曳光组件、曳光装药方案及曳光药剂抗冲击结构进行了优化,并对曳光管发火性能、动态发光强度和曳光时间进行了试验验证。结果表明,该曳光管在分别保常温(15℃,48h)、低温(-40℃,48 h)和高温(50℃,48 h)后,均能够满足动态发光强度不小于3 000 cd、曳光时间不小于6 s、曳光颜色为红色的技术指标要求,从而实现在弹丸4 000 m飞行轨迹上指示弹道的功能。

夹管训练结合渐进性盆底肌锻炼在前列腺增生切除术后军队退休干部患者膀胱功能康复中的作用

目的探讨夹管训练结合渐进性盆底肌锻炼在前列腺增生切除术后军队退休干部患者膀胱功能康复中的作用。方法选取空军军医大学第二附属医院2020年3月至2021年5月收治的行手术治疗的186例前列腺增生军队退休干部患者作为研究对象,依照信封随机法分为观察组和对照组,每组93例;对照组采用常规康复训练干预,观察组采用夹管训练结合渐进性盆底肌锻炼方案干预。在患者康复训练前及康复训练6个月后对治疗效果进行评价,包括临床疗效、控尿能力、尿动力学相关指标、国际前列腺症状评分、国际下尿路症候群症状(LUTS)评分、生活质量(QoL)评分、改良Barthel指数(MBI)、不良反应、泌尿道感染率及再次入院率。结果康复训练6个月后观察组临床疗效优于对照组(P<0.05),排尿、漏尿的次数少于对照组(P<0.05),恢复控尿的时间短于对照组(P<0.05),漏尿点压力(LPP)和最大尿道闭合压(MUCP)大于对照组(P<0.05),国际前列腺症状评分和LUTS评分低于对照组(P<0.05),MBI和QoL评分高于对照组(P<0.05),观察组泌尿道感染率和再次入院率低于对照组(P<0.05)。结论夹管训练结合渐进性盆底肌锻炼可有效促进前列腺增生切除术后军队退休干部患者的膀胱功能康复,具有较高的临床价值。

间歇性经口至食管管饲法联合康复训练对脑卒中后吞咽障碍患者的影响研究

目的:研究间歇性经口至食管管饲法联合康复训练对脑卒中后吞咽障碍患者病耻感、营养状态及吞咽功能的影响。方法:选取2019年1月—2021年12月南阳市第二人民医院收治的150例脑卒中后吞咽障碍患者作为研究对象,按照随机分配原则分为实验组和对照组,每组各75例。对照组患者接受常规护理治疗模式,实验组患者行间歇性经口至食管管饲法联合康复训练模式,比较两组患者治疗效果,比较干预前、干预后两组患者病耻感程度、吞咽功能评分及营养状态评分情况。结果:干预后,实验组患者病耻感程度评分均低于对照组患者,差异有统计学意义(t=73.613、177.429、30.003,P<0.05)。干预后,两组患者洼田饮水试验评分、标准吞咽功能评定量表(SSA)评分均低于干预前,差异有统计学意义(P<0.05)。实验组患者干预后营养风险筛查2002(NRS2002)评分低于对照组患者,差异有统计学意义(t=8.717,P<0.05)。结论:间歇性经口至食管管饲法联合康复训练应用于脑卒中后吞咽障碍患者中,对于改善患者吞咽功能具有显著的临床效果,且能够降低患者的病耻感,改善患者的营养状况,减少不良反应的发生。

护理专案在心脏外科术后获得性吞咽障碍患者中的应用效果

目的 探讨护理专案在心脏外科术后获得性吞咽障碍患者行吞咽康复训练中的应用效果。方法 采用便利抽样法,选取2021年7月—2023年6月在厦门大学附属心血管病医院住院的60例心脏外科术后发生获得性吞咽障碍患者为研究对象。将实施护理专案前的30例患者设为对照组;将给予护理专案后的另外30例患者设为观察组。比较2组患者康复训练执行率、鼻饲管平均留置天数及吞咽障碍并发症(主要为显性误吸及吸入性肺炎)发生率。结果 观察组吞咽障碍康复训练执行率为90.00%,高于对照组的20.00%,差异有统计学意义(P <0.05);观察组鼻饲管平均留置天数短于对照组,吞咽障碍并发症总发生率低于对照组,差异有统计学意义(P <0.05)。结论 护理专案可提高护理人员吞咽障碍康复执行率,降低患者鼻饲管平均留置天数,有效促进心脏外科术后吞咽障碍患者康复进程,改善患者预后。

静脉输液治疗培训盒联合同步投影在留置针冲封管培训中的应用

目的探讨一种静疗教学培训盒联合同步投影在留置针冲封管培训中的应用。方法选取2021年7月至2022年6月南昌市第一医院各个科室定期参与静疗专科培训的300名护士作为研究对象,采用随机数字表法将其分为试验组和对照组,每组各150名。两组均按照《临床静脉导管维护操作专家共识》实施操作技术教学,试验组运用新型静疗培训盒装置联合同步投影进行留置针冲封管维护培训。比较培训前后两组的理论知识、留置针维护冲封管操作考核、1 min找错训练结果及护士对于培训的满意度。结果试验组的理论知识成绩高于对照组,差异有统计学意义(P<0.05);试验组的操作成绩高于对照组,差异有统计学意义(P<0.05);试验组的1 min找错训练得分及满意度高于对照组,差异有统计学意义(P<0.05)。结论结合静疗教学培训盒联合同步投影在留置针冲封管培训,能提高专科护士的专科理论知识,工作坊的自主操作模式让专科护士准确掌握对留置针使用不同输液接头进行冲封管操作的规范性,大大提高了专科护士对培训的满意度。

真空管道列车动态运行气动特性研究

研究真空管道列车瞬态气动特性能为建设多态耦合真空管道列车实验平台提供参考。建立了三维真空管道列车模型,采用剪切应力运输(Shear Stress Transport,SST)k–ω湍流模型求解流场,通过对比不同时刻列车匀速和加速时的气动阻力、压力分布及流场特性,揭示了加速度对真空管道列车气动阻力的影响机制。研究结果表明:头车和尾车气动阻力主要受管道壅塞和尾部激波脱离的影响,在非壅塞状态下,尾车阻力增长缓慢而头车阻力基本不变。相比于加速工况,匀速工况启动速度较大,斜激波反射造成列车表面压力波动,波动幅值随时间逐渐降低。加速时头车压缩前方空气过程较缓慢,前驱激波强度较低,头车气动阻力和周围压力的变化滞后于列车运行速度的变化,且加速度越小滞后效果越明显。在匀速运行阶段,壅塞段和尾部激波段长度与运行时间成正比。

极端温度下高速铁路钢管混凝土拱桥行车安全

研究目的:为研究温度荷载作用下桥梁结构产生的变形对桥上行车安全性的影响,以成贵高铁某钢管混凝土拱桥为研究对象,基于ANSYS建立大跨桥梁-轨道精细化有限元模型,分析不同温度荷载作用下结构变形规律。在此基础上,将桥梁-轨道结构有限元模型导入SIMPACK中进行联合仿真,构建列车-轨道-桥梁耦合振动分析模型,最后从列车运营安全性与舒适性方面讨论不同温度荷载作用和不同车速下列车动力响应指标的变化规律。研究结论:(1)桥梁上挠温致变形引起的轨道附加不平顺比下挠更不利;(2)组合温度作用下,行车安全性指标仅轮重减载率出现超限,建议将其作为高速铁路桥上行车安全的主要评价指标;(3)温度梯度是导致轮重减载率出现超限的重要原因,实际工程中分析温度作用对列车行车安全的影响时,应考虑温度梯度的作用;(4)垂向Sperling指标对温度作用十分敏感,为保障行车舒适性,列车在极端温度条件下行驶时应控制车速;(5)本研究成果可为钢管混凝土拱桥的行车安全性评价提供参考。