An Overview of High-efficiency Synchronous Reluctance Machines

In recent years the synchronous reluctance machines(SynRMs)have received much attention.They have some good features such as high torque density,high reliability and low cost.This paper aims to give an overview of SynRMs with particular emphasis on the history,research status and industrial application.Besides,concept and basic operating principles of such machines are also described.Moreover,some hot spots of the research on the SynRMs are introduced.Several methods to improve the average torque and reduce torque ripple of the SynRMs in the past literatures are presented including topology design and control strategies.An overview of the methods from different aspects to realize high efficiency for the SynRMs is given which contain rotor optimization,winding configuration,material improvement,control schemes and so on.Some approaches suitable for high speed application are also introduced.It can be seen that the SynRMs have broad development prospects and great potential in industrial application.

Air flow patterns and noise analysis inside high speed angular contact ball bearings

The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.

Effect of Alloying Additions on the Oxidation of High Speed Steels under Dry and Wet Conditions

An investigation has been carried out into the effects of chromium and vanadium content on the oxidation rate and on the adhesion of oxide scales grown on three different chemical compositions of high speed steels under dry and wet conditions.The oxidation tests were carried out in a thermobalance at 650℃for up to 14.4 ks.The mass gain of the specimens increased with increasing contents of water vapour. Alloy composition had no effect on the oxidation rate in dry conditions.The'adhesion'of the oxide scale was determined using indentation with a Rockwell C diamond and the pull adhesion test to determine the interfacial toughness and the tensile strength of the oxide metal bond,respectively.Generally,the results of the investigation indicated that oxide adhesion was lowest for the specimens exposed to dry conditions, and that with increasing water vapour content,the scale was more adherent.Indentation test results showed that an increase in the V concentration was deleterious to oxide adhesion in both the dry and wet environments,whereas an increase in the Cr-content had little effect on adhesion.

Current Status and Prospects of High-Speed Direct-Drive Power Generation Technology

Turbine generators play a pivotal role in efficiently converting gas internal energy into electrical energy,finding extensive applications in diverse green energy and power equipment.The adoption of a high-speed direct-drive structure eliminates mechanical losses associated with the reducer between the turbine and generator,enhancing system efficiency and compactness.However,this configuration introduces challenges in design and manufacturing.This article explores the various application scenarios of high-speed direct-drive power generation systems,examining their roles in organic Rankine cycle power generation,gas turbine power generation,supercritical CO_(2) power generation,vehicle exhaust turbine power generation,and natural gas pressure reduction power generation.Considering the high-speed,high-pressure,high-temperature,and high-efficiency challenges in turbine power generation systems,the key technologies are reviewed including high-speed bearings,rotor dynamics,high-speed motors,high-frequency variable frequency technology,sealing technology,axial force adjustment,thermal management,turbine aerodynamic design,and system control strategies.The article further delves into the current research and development status of high-speed direct-drive power generation systems across different application scenarios.Finally,the article presents prospects for the future development of efficient,reliable and widely adaptable high-speed direct-drive generators,offering valuable insights for researchers and practitioners in the field.

Development and Installation of High Pressure Boilers for Co-Generation Plant in Sugar Industries

The sugar cane containing minimum 30% fiber was referred as bagasse and used the generation of power required for the operation of sugar mill. The bagasse is fired in the boiler for producing steam at high pressure, which is extracted through various single high capacity turbines and used in the process. The installation of high pressure boilers and high pressure turbo-generators has provision for the operation of co-generation plant during the off-season also that enhances the power generation from 9MW to 23MW. The annual monetary benefits achieved are Rs. 204.13 million and this was based on cost of power sold to the grid @ Rs 2.548 per unit, sugar season of 219 days and off season of 52 days. This required an investment of Rs 820.6 million. The investment had an attractive simple payback period of 48 months.

Applications of High-Efficiency Abrasive Process with CBN Grinding Wheel

High-efficiency abrasive process with CBN grinding wheel is one of the important techniques of advanced manufacture. Combined with raw and finishing machining, it can attain high material removal rate like turning, milling and planning. The difficult-to-grinding materials can also be ground by means of this method with high performance. In the present paper, development status and latest progresses on high-efficiency abrasive machining technologies with CBN grinding wheel relate to high speed and super-high speed grinding, quick point-grinding, high efficiency deep-cut grinding, creep feed deep grinding, heavy-duty snagging and abrasive belt grinding were summarized. The efficiency and parameters range of these abrasive machining processes were compared. The key technologies of high efficiency abrasive machining, including grinding wheel, spindle and bearing, grinder, coolant supplying, installation and orientation of wheel and workpiece and safety defended, as well as intelligent monitor and NC grinding were investigated. It is concluded that high efficiency abrasive machining is a promising technology in the future.

某300MW机组高压进汽结构气动优化

采用数值模拟的方法对某300MW汽轮机的高压进汽结构进行了气动优化,通过增大关键部位通流面积、增大过渡倒圆,降低了流速,总压损失由4.11%降低到0.045%,出口静压不均匀度由0.67降低到0.020。

计及高风速和低风速影响的海上风电机组两阶段滚动优化维护策略

针对复杂天气变化影响下海上风电机组维护决策问题,提出了考虑高风速与低风速影响的海上风电机组两阶段滚动优化机会维护策略。首先,提出考虑高风速冲击影响的维护役龄回退模型,量化实际部件退化与及维护成本关系。其次,建立了考虑低风速停机事件维护机会影响的海上风电机组长短期两阶段预防性机会维护模型,滚动更新长期预防性机会维护阈值。最后仿真结果表明,本文所提模型能够有效降低海上风电机组停机成本以及故障损失,提高机组寿命周期内的维护效益。

基于Dinkelbach-Quadratic算法的高速铁路通信能效优化功率分配研究

为了提高高速铁路通信能量效率,提出一种基于Dinkelbach-Quadratic变换的迭代算法来解决高速铁路通信下行链路的功率分配问题。通过在小区内部署远程天线单元构建高速铁路通信分布式天线系统模型,基于完美信道状态信息(CSI)和列车内接入点反馈的最小速率要求建立能效优化模型;基于所建立的非凸优化模型,采用Dinkelbach变换将分数形式的非线性规划问题转换为求差形式;利用Quadratic变换特性对目标函数进一步展开;采用交替迭代的方法完成能效最优的功率分配。仿真结果表明:所提算法在满足最小传输速率和最大发射功率的同时,可以兼顾系统能量效率和频谱效率;随着发射天线数量和接收中继数量的增加,系统性能也有明显提升,相比传统算法系统的能效和频谱效率至少提升5%。

400 km/h高铁隧道出入口缓解微气压波综合效果分析

为准确预测高速铁路隧道出口微气压波幅值,以三维、非定常、可压缩流动理论为基础,利用Fluent软件模拟时速400 km的列车驶入100 m2端墙式双线隧道时,分析列车在不同入口侧部开口缓冲结构、出口侧部开口缓冲结构及出口仰坡斜率下对出口微气压波的影响效应,并结合出入口缓冲结构综合分析微气压波联合缓解效果。结果表明:1)对出口微气压波峰值、出口缓冲结构、仰坡斜率进行相关性分析,结合辐射立体角公式线性拟合立体角变化趋势,得出立体角随缓冲结构开口率、洞门仰坡斜率的增大均呈现由急到缓的2段式上升曲线;2)数值分析得到在不同入口缓冲结构开口率下初始压缩波压力梯度变化规律和出口微气压波缓解效率规律,再结合隧道出口缓冲结构、仰坡斜率提出微气压波联合缓解效率预测公式,预测分析微气压波联合缓解效果在不同影响因素下的变化趋势;3)针对预测结果结合数值模拟验证工况进行误差分析,表明可以将出口立体角分析结果与入口缓冲结构缓解规律相结合。

叶片安放角对微型轴流式水轮机性能的影响

为探究叶片安放角对微型轴流式水轮机水力性能的影响,以一比转数为548的微型轴流式水轮机为研究对象,在不改变其他几何参数的前提下,仅偏置转轮叶片各翼型剖面,得到7个不同叶片安放角的转轮;在试验验证的基础上,通过全流场数值计算,分析了改变叶片安放角对微型轴流式水轮机水力性能的影响.结果表明:随着叶片安放角的减小,在相同流量下水轮机的水头与出力均增大,高效率区域向小流量区域偏移,水轮机可高效运转的范围有一定程度的增大;随着叶片安放角的增大,水轮机的水头与出力减小,高效率区域向大流量区域偏移.适当减小叶片安放角的水轮机能在较大水头(流量)变化范围内维持较好的性能.其中,安放角为-4°的水轮机最高效率达到82.13%,高效率区的范围最大.该研究可为微型轴流式水轮机转轮的设计提供一定参考.

高铁开通对城市能源利用效率的影响机制及空间溢出效应研究

将高铁开通视为一项准自然实验,基于2006—2019年城市面板数据,运用多期双重差分法实证检验高铁开通对城市能源利用效率的影响,并进一步分析其影响机制及空间溢出效应。研究发现:(1)高铁开通对城市的能源利用效率具有显著的提升作用。(2)高铁开通通过提高铁路货运效率、替代公路客运、优化产业结构及促进技术创新,提升了城市的能源利用效率。(3)高铁开通对邻近城市的能源利用效率存在正向空间溢出效应,并存在800公里的空间距离衰减边界。(4)高铁开通对城市能源利用效率的提升作用在不同区域、等级、规模、资源禀赋的城市存在显著的异质性,其中对中西部城市、小城市、普通城市、资源型城市的能源利用效率提升作用更为显著;此外,高铁开通对衰退型的资源型城市能源利用效率的促进效果最大,对成熟型的资源型城市的影响次之,但对成长型和可再生型的资源型城市不存在显著性影响。研究结论为理解高铁在能源利用效率方面的作用提供了新视角和新证据,也为实现“节能减排”和“交通强国”提供了政策启示。

CO_(2)压缩机组驱动汽轮机节能改造与安装

某进口CO_(2)压缩机组驱动汽轮机已运行45年,存在缸体变形、效率低、轴承磨损等问题。为解决上述问题,决定更换1台国产新机。文章对压缩机组汽轮机节能改造与安装的过程进行了分析和总结,并通过该汽轮机节能改造与安装项目研究了新、旧汽轮机在结构设计方面的异同;同时,针对四轴系的大型压缩机组,研究了如何在保证压缩机3个轴系不动的情况下,以低压缸为基准实现汽轮机中心在前后、高低、左右3个坐标方向上高精度(0.01 mm级)定位的方法,并利用该方法完成了新汽轮机(总质量22 t)的逆向、精准安装。

高水头电站水轮机泥沙磨损评估及抗磨蚀综合措施

对于高水头电站,泥沙磨损的影响在水轮机的设计和参数选择中是一个不可忽视的问题。以科哈拉水电站为例,根据电站的泥沙特性,对水轮机的泥沙磨损进行试验和评估。从水轮机参数选择、水力设计、结构及工艺、材料及表面防护、调度运行等方面提出了针对性的抗泥沙磨蚀综合措施。研究内容可为其他高水头电站水轮机抗磨蚀方案的设计提供参考。

光热汽轮机高低位布置研究

文章着重研究目前投运或在建中小功率光热汽轮机的布置方式,并结合相关常规汽轮机的布置经验,从基建成本、布置美观性、安装检修等多方面分析,总结出适合光热汽轮机的布置方式为中低位布置。

基于流场换热的阀壳瞬态温度场分析及强度评估

文章基于浸入边界法,对汽轮机阀壳进行了流场分析,得到了阀壳在不同开度下的换热系数场和温度场,根据机组启停曲线分析了阀壳瞬态温度场,并在循环热载荷和压力载荷下的得到了阀壳在启停过程的低周疲劳和长时运行时的高温蠕变,为研制更加安全、高效的汽轮机阀壳提供了重要理论依据。

Spatial relationship of high-speed transportation construction and land-use efficiency and its mechanism:Case study of Shandong Peninsula urban agglomeration

Land-use efficiency is low for the urban agglomeration of China. High-speed transportation construction has been an important factor driving land use change. It is critically important to explore the spatial relationship between the high-speed transportation superiority degree and land-use efficiency. We built a model to evaluate the benefits of convenient high-speed transportation using the relative density of highways and the distance from high-speed rail stations and airports as a metric. We used 42 counties of the Shandong Peninsula urban agglomeration as an example. Land-use efficiency was calculated by a DEA model with capital, labor, economic benefits and environmental benefits as input and output factors. We examined the spatial relationships between high-speed transport superiority degree and land-use efficiency and obtained the following results. First, there are significant spatial differences in the relationships between the high-speed transportation superiority degree and land-use efficiency. Taking the two major cities of Jinan and Qingdao as the hubs, the core surrounding counties show significant spatial relationship between land-use efficiency and the high-speed transportation superiority degree. Spatial correlation declines as the distance from the hubs increases. Land-use efficiency is less than high-speed transportation convenience in areas along the transportation trunks that are distant from the hub cities. Correlation is low in areas that are away from both hub cities and transportation trunk routes. Second, high-speed transportation has a positive relationship with land-use efficiency due to the mechanism of element agglomeration exogenous growth. Third, high-speed transportation facilitates the flow of goods, services and technologies between core cities and peripheral cities as space spillover(the hub effect). This alters the spatial pattern of regional land-use efficiency. Finally, the short-board effect caused by decreased high-speed transport construction can be balanced by highway construction and the proper node layouts of high-speed rail stations and airports, resulting in a well-balanced spatial pattern of land-use efficiency.

站城融合理念下高铁站点换乘导视系统优化设计研究

目的本文以重庆建设国际性综合交通枢纽城市为研究背景,满足各类人群高铁出行的适宜性与多样性需求,升级城市形象展示窗口。深入剖析高铁站点导视系统在换乘枢纽中的实际应用情况,紧密关注城市智慧交通导视系统的发展趋势与最新动态,致力于解决用户在换乘过程中可能遇到的视觉困扰和引导不足等核心问题,并在此基础上提出具有针对性的优化设计方案。方法对城市高铁站轨道换乘导视系统的设计要点和布设方法进行举证研究,重点就城市智慧出行、数字导视系统进行分析,结合对乘客空间寻路、安全感、舒适感等心理需求的调研,总结轨道交通换乘站点导视系统的设计思路。综合考虑色彩及应用、字号及对比度、字体及视觉度、布设逻辑与信息分级,把控导视系统的视觉度、布设尺度、色彩材质、技术工艺。结合我国高铁站轨道换乘导视系统的发展现状,提出重庆西站换乘导视系统的优化设计策略。结论在尊重空间动向、用户体验、视觉流程的基础上,以智慧交通导视系统为研究对象,充分探寻高铁站点轨道换乘导视系统的高效性、便捷性,旨在提升枢纽的建设水平、运行效率,以及人民群众的出行体验。

红层地区高铁路堑基底上拱等级预测研究

轨面平顺性是高速铁路安全运行的重要保证。近年来,四川红层部分高速铁路(客运专线)出现路基上拱病害,致使轨面不平顺并影响高铁正常运营。对于高速铁路无砟轨道线路,基底上拱整治十分困难,如能在铺轨前进行上拱预测,就可采取相应措施以减缓路基上拱,因此高铁路基上拱预测研究势在必行。以成渝客运专线为研究对象,在综合分析路基上拱主要影响因素的基础上,选取路基中心开挖深度、岩层倾角、砂泥岩互层关系、泥岩饱和单轴抗压强度、泥岩膨胀性5个评价指标,采用熵权法确定各指标权重,运用功效系数法建立高铁红层路基上拱等级预测模型。将该模型应用于成渝客专和沪渝蓉高铁建设前期主要上拱段及上拱等级预测,验证了该模型的可行性与实用性。