Optimal driving strategy for traction energy saving on DC suburban railways

Energy saving on electrified railways has been studied for many years and the technical solution is usually provided by a combination of driving strategy (e.g. coasting), regenerative braking and energy storage systems. An alternative approach is for the driver (or automatic train operation system if fitted) to manage energy consumption more efficiently. A formal method for optimising traction energy consumption during a single-train journey by trading-off reductions in energy against increases in running time has been demonstrated. The balance between saving energy and running faster has been investigated by designing a fitness function with variable weightings. Energy savings were found, both qualitatively and quantitatively, to be affected by acceleration and braking rates, and, by running a series of simulations in parallel with a genetic algorithm search method, the fitness function was used to identify optimal train trajectories. The influence of the fitness function representation on the search results was also explored.     

Implementing absorption refrigeration cycle in lieu of DMR and C3MR cycles in the integrated NGL,LNG and NRU unit

In this paper, the potential of absorption refrigeration cycle to be replaced by C3MR and DMR cycles and to reduce energy consumption in the integrated structure of NGL, LNG and NRU is investigated. Having simulated and optimized, the absorption refrigeration cycle is replaced by one of the compression cycles in the two presented integrated structures, and the new integrated process with AR-MR1 refrigeration cycle (pre-cooling by absorption refrigeration system and liquefaction by mixed refrigerant) is presented. The new structures are investigated through exergy and economic analyses. The integrated structure of AR-MR1 in comparison with C3MR and DMR processes has reduced the power consumption by about 18.4% and 12.6%, respectively. Sensitivity analysis of economic parameters has been carried out with respect to the utility price as well as effect of product price on the market with respect to the presented structures.     

Coasting point optimisation for mass rail transit lines using artificial neural networks and genetic algorithms

Energy consumption of a rail transit system depends on many parameters. One of the most effective methods of reducing energy consumption in a rail transit system is optimising the speed profile of the trains along the route. A new efficient method will be presented for the optimisation of the coasting points for trains in a global manner. The proposed approach includes realistic system modelling using multi-train, multi-line simulation software and application of artificial neural networks (ANN) and genetic algorithms (GA). The simulation software used can model regenerative braking and train performance at low voltages. Using ANN and GA together, optimal coasting points for long line sections covering five stations and two lines are achieved. Simulation software is used for creating training and test data for the ANN. These data are used for training of the ANN. Trained ANNs are then used for estimating energy consumption and travel time for new sets of coasting points. Finally, the outputs of the ANN are optimised to find optimal train coasting points. For this purpose, a fitness function with target travel time, energy consumption and weighting factors is proposed. An interesting observation is that the use of ANN increases the speed of optimisation. The proposed method is used for optimising coasting points for minimum energy consumption for a given travel time on the first 5 km section of Istanbul Aksaray-Airport metro line, where trains operate every 150 s. The section covers five passenger stations, which means four coasting points for each line. It has been demonstrated that an eight input ANNs can be trained with acceptable error margins for such a system.     

Performance improvement of nitrogen expansion liquefaction process for small-scale LNG plant

Liquefaction of natural gas is usually a kind of high energy consumption process. Therefore, any performance improvement of the liquefaction process will definitely reduce the energy consumption. Nitrogen expansion liquefaction process is regarded as a suitable process for small-scale LNG plant due to its simplicity, quick startup and convenient maintenance. However, the disadvantage of the process is high-energy consumption. An efficient way to lower its energy consumption is to add a precooling cycle. In this paper, two different precooling cycles including propane precooling cycle and R410a precooling cycle are proposed to the nitrogen expansion liquefaction process to improve the liquefaction process performance. Unit energy consumption as an objective function is optimized in terms of several key operating parameters. Based on the optimization results, the effects of the liquefaction rate and methane recovery rate on the process performance are investigated. The thermodynamic analyses are adopted to the processes as well as the two precooling cycles. Furthermore, the exergy analyses of the main equipment are also presented and discussed. The results show that the unit energy consumption for the nitrogen expansion process with R410a precooling and with propane precooling reduce by 22.74% and 20.02% respectively, compared with nitrogen expansion process without precooling.     

轨道交通列车运行能耗优化研究

本文对轨道交通单或多列车面向节能的优化决策进行研究．列车需求能源的量极大,对轨道车辆合理的调配,降低运行能耗的研究意义重大．列车运行所处环境的复杂性和对轨道线路的起伏性,致列车受力是随时变化的．实现通过模拟轨道列车运行研究出优化模型,应用价值和理论意义重大．采用极大值原理、多目标二次规划、非线性方程模型最优化轨道列车所耗能量,在能量最优化情况下研究了位移、速度和时间、速度的规律变换．     

吸能材料缓冲性能评价方法综述

目的 进一步科学评价吸能材料缓冲性能,以促进吸能材料的研究与推广应用。方法在对常见吸能材料进行分类的基础上,全面调查吸能材料缓冲性能测试方法,系统分析缓冲性能数据表征及处理方法。结果 缓冲性能测试方法主要借助压缩试验与冲击试验2类,其中压缩试验又可分为静态压缩试验与动态压缩试验;缓冲性能数据表征及处理方法主要有缓冲曲线法、能量吸收率曲线法、能量吸收图法、Janssen因子法与Rusch曲线法5种类型。能量吸收图法因能够同时汇集不同密度、应变率条件下材料吸能特性与缓冲效果,反映材料最佳吸能点,在使用过程中更具广泛性。结论 推荐采用能量吸收图来表征吸能材料的缓冲吸能特性。     

Robust energy-efficient train speed profile optimization in a scenario-based position–time–speed network

Train speed profile optimization is an efficient approach to reducing energy consumption in urban rail transit systems. Different from most existing studies that assume deterministic parameters as model inputs, this paper proposes a robust energy-efficient train speed profile optimization approach by considering the uncertainty of train modeling parameters. Specifically, we first construct a scenario-based position–time–speed (PTS) network by considering resistance parameters as discrete scenario-based random variables. Then, a percentile reliability model is proposed to generate a robust train speed profile, by which the scenario-based energy consumption is less than the model objective value at \alpha confidence level. To solve the model efficiently, we present several algorithms to eliminate the infeasible nodes and arcs in the PTS network and propose a model reformulation strategy to transform the original model into an equivalent linear programming model. Lastly, on the basis of our field test data collected in Beijing metro Yizhuang line, a series of experiments are conducted to verify the effectiveness of the model and analyze the influences of parameter uncertainties on the generated train speed profile.     

An Energy-Efficient Protocol Using an Objective Function & Random Search with Jumps for WSN

Wireless Sensor Networks (WSNs) have hardware and software limitations and are deployed in hostile environments. The problem of energy consumption in WSNs has become a very important axis of research. To obtain good performance in terms of the network lifetime, several routing protocols have been proposed in the literature. Hierarchical routing is considered to be the most favorable approach in terms of energy efficiency. It is based on the concept parent-child hierarchy where the child nodes forward their messages to their parent, and then the parent node forwards them, directly or via other parent nodes, to the base station (sink). In this paper, we present a new Energy-Efficient clustering protocol for WSNs using an Objective Function and Random Search with Jumps (EEOFRSJ) in order to reduce sensor energy consumption. First, the objective function is used to find an optimal cluster formation taking into account the ratio of the mean Euclidean distance of the nodes to their associated cluster heads (CH) and their residual energy. Then, we find the best path to transmit data from the CHs nodes to the base station (BS) using a random search with jumps. We simulated our proposed approach compared with the Energy-Efficient in WSNs using Fuzzy C-Means clustering (EEFCM) protocol using Matlab Simulink. Simulation results have shown that our proposed protocol excels regarding energy consumption, resulting in network lifetime extension.     

Energy-saving operation approaches for urban rail transit systems

With the accelerated urbanization in China, passenger demand has dramatically increased in large cities, and traffic congestion has become serious in recent years. Developing public urban rail transit systems is an indispensable approach to overcome these problems. However, the high energy consumption of daily operations is an emerging issue due to increased rail transit networks and passenger demands. Thus, reducing the energy consumption and operational cost by using advanced optimization methodologies is an urgent task for operation managers. This work systematically introduces energy-saving approaches for urban rail transit systems in three aspects, namely, train speed profile optimization, utilization of regenerative energy, and integrated optimization of train timetable and speed profile. Future research directions in this field are also proposed to meet increasing passenger demands and network-based urban rail transit systems.     

高速列车谐波转矩振动分析及自抗扰控制

高速列车在实际运行过程中,当路面不平顺、车轮磨耗或者列车由明线运行到突然进入隧道均可能会引起转矩脉动,引起齿轮箱振动加剧。为研究谐波转矩波动幅值对高速列车牵引齿轮箱振动加速度的影响,建立考虑时变啮合刚度、啮合阻尼、啮合误差、齿侧间隙的齿轮传动系统与三相异步动态电机耦合的机电传动系统模型,在Simulink平台上分析牵引传动系统在谐波转矩幅值变化的工况下齿轮箱输入端振动加速度特性。结果表明,谐波转矩增大使齿轮箱振动加速度加大,且横向振动加速度增加最明显。耦合系统叠加混合型自抗扰控制器(ADRC)后,对谐波转矩引起的齿轮箱横向振动具有较好的抑制作用。     

基于LEACH协议的改进路由算法

针对LEACH协议在簇头选择过程中消耗能量多和节点间能量消耗不均匀的问题,本文提出了一种基于时间的均匀分簇混合路由协议( ECHT)在簇头竞选阶段中,节点广播成为簇头的时间与其剩余能量成反比,越早广播的节点将成为簇头.在数据传输阶段中,采用多跳与单跳相结合的方式将数据传送到基站,并计算数据传送开销来修改节点能量以此确定网络生命周期.仿真结果显示,ECHT协议能有效地均衡网络节点的能量消耗和延长网络生命周期.     

Research of rail traction shafts and axles fractures towards impact of service conditions and fatigue damage accumulation

Traction shafts and axles of railway vehicles are designed to be safe and reliable in normal service conditions. Accidental and unpredictable conditions including bad exploitation (rail tracks, maintenance and extreme long service life) make the probability of shaft and axle fracture realistic. This article contains the experience and analysis of the traction shafts and axles fractures and fracture processes. Research also shows service conditions with results presented in the form of service stress spectrums. Besides normal service conditions, the results also include unpredictable phenomenon such as natural torsion vibrations of the shaft and wheels caused by stick–slip processes at the moment of the set in motion of a full-loaded train or at the moment of braking. These vibrations create an extremely high level of torque which is the main cause of cracks initialization. The next part of the article contains the results of the traction shafts and axles endurance research. The results of testing are transformed using the results of calculation by the FE method and by statistical estimation of the failure probability distribution. The main part refers to the interaction (impact) of service stress probability and failure (endurance) probability, which leads to the traction shaft (axle) reliability definition. Using the established model, locomotive traction shaft reliability is calculated and analyzed. The final part of the article contains suggestions for the traction shafts (axles) failure prevention.     

基于运行数据包络线的冷水机组运行优化策略研究

为提高冷水机组能效,本文提出一种基于冷水机组运行数据性能包络线的负荷分配优化控制策略。基于历史运行数据,采用数据衍生与移动窗口方法,获取了冷水机组的性能包络线,并基于性能包络线对负荷分配进行优化。通过在我国南方某机场空调系统运行测试,对本策略进行了验证并与顺序启停控制策略进行了对比,结果表明:该控制策略具有较好的节能效果。在典型日,该控制策略相比顺序启停控制策略的节能效果提升8. 2%。     

某地铁列车空调制冷系统的仿真与优化

我国的地铁建设正处于高速发展期,但目前典型地铁列车空调制冷系统的能效比只有2.2～2.3,远低于同类工况下住宅空调制冷系统的能效水平。针对此问题,先建立了某地铁空调制冷系统模型,仿真与系统测试结果吻合良好。然后通过详细的仿真分析,改进蒸发器和冷凝器的制冷剂流路设计、采用小排量高能效比压缩机等方法,使得系统在冷量和成本基本不变的情况下能效比提升了21.7%。最后,研究了制冷剂R410A替代R407C的系统性能变化,系统能效比可进一步提升11.3%,达到3以上。该研究方法及结果对于设计高效节能的地铁列车空调制冷系统具有参考价值。     

一种联合优化的水声通信网路由算法设计

针对传统的无线网络路由建立算法在水下小型网络中时延及能耗代价高的问题,提出了改进的DSDV(Destination Sequenced Distance Vector)路由过程,并在此基础上设计出与拓扑结构、MAC层联合优化的算法。该算法建立了以改进的DSDV路由建立时间、能耗及路由信息的完整性为代价函数,以MAC层的包长度、包间隔、拓扑结构中的点和边数等为矢量参数的数学模型,并结合无向图的广度优先搜索算法及最短路径算法,提出了在上述矢量参数条件下代价函数的最优化设计,形成一套适用于小规模区域性观测应用背景的水声通信网的路由建立方法。仿真结果表明,在相同的物理层条件下,联合优化的算法与未优化的DSDV相比,在相同的时间内建立完整的全网路由的概率最大可提高30%。     

基于PMV指标的列车空调节能研究

目前列车空调基本上是定风量运行的,由于列车空调负荷随时间和地点变化,定风量空调系统无法达到令人满意的热舒适性,而且浪费能源。本文通过分析PMV方程的特点,提出以PMV指标作为控制变量的变风量空调系统应用于列车空调,分析该空调系统的控制原理;通过实例计算分析,验证列车使用变风量空调系统的可行性,得到变风量空调系统的节能潜力。     

Designing train-speed trajectory with energy efficiency and service quality

With the development of automatic train operations, optimal trajectory design is significant to the performance of train operations in railway transportation systems. Considering energy efficiency and service quality, this article formulates a bi-objective train-speed trajectory optimization model to minimize simultaneously the energy consumption and travel time in an inter-station section. This article is distinct from previous studies in that more sophisticated train driving strategies characterized by the acceleration/deceleration gear, the cruising speed, and the speed-shift site are specifically considered. For obtaining an optimal train-speed trajectory which has equal satisfactory degree on both objectives, a fuzzy linear programming approach is applied to reformulate the objectives. In addition, a genetic algorithm is developed to solve the proposed train-speed trajectory optimization problem. Finally, a series of numerical experiments based on a real-world instance of Beijing–Tianjin Intercity Railway are implemented to illustrate the practicability of the proposed model as well as the effectiveness of the solution methodology.     

偏心故障下动车组牵引电机转子振动特性分析

气隙偏心和质量偏心是动车组牵引电机中普遍存在的两类偏心故障,而由此产生的不平衡磁拉力和机械不平衡力常诱发更为复杂的转子动力学行为,危害列车牵引驱动装置的安全可靠运行。为此,该文建立了静动气隙偏心和转子质量偏心下牵引电机转子系统的Jeffcott模型;推导了静动气隙偏心下牵引电机带负载运行时气隙磁密分布和转子铁芯表面Maxwell应力分布,并给出了可适用于静动气隙偏心、空载/负载运行和任意磁极对数的电机不平衡磁拉力统一解析表达式;采用四阶定步长Runge-Kutta算法计算了某型动车组牵引电机转子在不平衡磁拉力和机械不平衡力作用下的动力响应,并详细讨论了初始静偏心、质量偏心、径向刚度以及转速对系统振动特性的影响规律。结果表明:偏心故障下该型牵引电机转子轴心轨迹呈现接近圆形的椭圆状,其中质量偏心、径向刚度和转子转速会影响轴心轨迹大小,而初始静偏心和径向刚度则使轨迹中心沿静偏心方向偏移。同时,气隙偏心的存在使得具有质量偏心故障的电机转子位移频谱中较明显地包含零频、转频、固有频率、二倍转频、二倍供电频率及其与转频的组合等分量。     

Supply of cooling and heating with solar assisted absorption heat pumps: an energetic approach

The primary energy consumption of two kinds of solar assisted absorption systems (solar assisted absorption chiller during summertime and heat pump during wintertime or solar assisted absorption chiller with direct gas combustion for heating during wintertime) is compared with the primary energy consumption of a compression chiller which can work as a heat pump during wintertime. For the absorption systems three technical options were considered: a single effect machine; a double effect machine with the solar energy delivered to the lower temperature desorber and combustion heat of a gas burner delivered to the higher temperature desorber; a double effect machine with both solar energy and combustion heat delivered to the higher temperature desorber. The analysis performed in this article shows that solar assisted absorption chillers, absorption heat pumps and direct solar heating systems even with low and intermediate solar fractions can operate with considerably less primary energy consumption than compression systems. Further, the necessary solar collector area to achieve that goal is compatible with roof area available in buildings. It was also verified that, for the double effect absorption machines, there is no advantage in delivering the solar energy to the higher temperature desorber, thus establishing as preferable the solution in which it is delivered to the lower temperature desorber.     

无线传感器网络的流量自适应分簇算法协议

在分析LEACH路由协议算法的缺点的基础上,提出了一种用于无线传感器网络的基于流量自适应的TDMA分簇算法协议.该协议根据当前节点数据流量的变化,自适应地调整该节点在其簇内通信的时隙长度,减少节点空闲时消耗的能量和节点从睡眠到活跃状态来回切换的能量.仿真实验结果表明,与LEACH协议簇内时隙分配算法相比,运用这种新的时隙分配算法,可以节省节点的能量,提高网络的生存时间,改善网络性能.