水平支撑偏心受压构件承载力的简化计算

根据锅炉钢结构设计的特点,按《钢结构设计规范》(GB 50017-2003)的要求,提供了水平支撑偏心受压构件承载力标准值的简化计算方法。     

基于深度卷积神经网络的转子轴心轨迹智能识别

转子轴心轨迹作为转子故障的典型特征之一,可以提供更具代表性的故障特征信息。对转子轴心轨迹形状进行准确识别是构建转子故障特征征兆的基础。为提高转子轴心轨迹形状识别的泛化能力,提出一种基于深度卷积神经网络的转子轴心轨迹成像及形状识别方法(DimShapeNet)。将转子轴心轨迹映射到二维数字图像中,利用反灰度化预处理方法,去除二维数字图像中多余的颜色信息;将预处理后的转子轴心轨迹数字图像输入深度卷积神经网络中进行训练。结果表明：经过反灰度化预处理的转子轴心轨迹数字图像在深度卷积神经网络的训练中更有优势;相比于传统的转子轴心轨迹形状识别方法,基于深度卷积神经网络的转子轴心轨迹形状识别方法具有更高的准确性和更好的鲁棒性。     

风电齿轮箱浮动构件支撑刚度的分析与优化设计

以9 MW海上风电机组两级行星一级平行轴齿轮箱为研究对象,采用集中参数法建立其多体动力学模型,研究各级浮动太阳轮和内齿圈的支撑刚度对两级行星轮系均载特性和浮动构件振动特性的影响,基于正交试验法得到支撑刚度对传动轴振动的影响规律并对其进行优化设计。研究结果表明：综合考虑浮动构件的影响,在两级均载系数对支撑刚度敏感的区间内,浮动构件支撑刚度显著影响齿轮箱的振动特性;与仅考虑齿轮箱均载特性相比,优化后齿轮箱整体振动指标降低8.9%。     

基于截面配筋率的钢筋混凝土统一本构关系研究

为避免数值化分析中直接处理钢筋与混凝土之间的复杂关系,推导出钢筋混凝土构件轴心受压统一理论公式,做了不同配筋率与不同混凝土强度等级下的钢混棱柱体轴心受压试验,利用试验量测的荷载位移数据,结合Matlab曲线拟合工具的线性回归与拟合功能,建立了一种基于截面配筋率的能够描述钢筋混凝土材料力学性能的统一本构关系。对试验梁进行数值化分析表明,所建立的数值化模型应力应变特征与试验结果吻合较好,证明了该模型在钢筋混凝土实际运用过程中的可行性与适用性。     

多轴涡轮

多轴涡轮包括外侧的上覆盖物、塔架结构，它具有若干垂直的细长构件，这些垂直的细长构件相互与支撑用的水平的细长构件相连接；以及若干在一个旋转构件上的较1小的叶片，该旋转构件与若干旋转构件一起连接至塔架结构。一个优选实施例包括冲击叶轮，它们连接至旋转构件上，所建立的扫过面的高度与直径之比大于4。     

GFRP复合横担空心支柱绝缘子轴压失稳试验研究

开展了4组12根玻璃纤维增强复合材料（GRFP）复合横担支柱绝缘子轴心受压稳定性试验,分析了其破坏过程、破坏特征、管件变形、极限承载力及破坏形式,与欧拉公式、Perry-Robertson公式计算结果进行了对比分析,根据试验结果采用最小二乘法推导了GRFP圆管构件的极限承载力计算公式,其计算结果与试验结果吻合较好。     

液化石油气喷雾特性的试验与计算研究

采用高速摄影技术对液化石油气(LPG)喷雾特性进行试验研究,并利用准维气相射流模型模拟计算LPG喷雾的发展过程,计算结果与试验结果吻合较好。研究结果表明:在喷孔直径、背压等参数相同的条件下,LPG喷雾锥角和喷雾轴心浓度的衰减率随启喷压力升高而增大,而启喷压力对喷雾轴心速度的衰减率和喷雾贯穿距离则影响较小;在喷孔直径、启喷压力等参数相同的条件下,喷雾锥角、喷雾轴心速度和浓度的衰减率均随背压的升高而增大,而喷雾贯穿距离则随背压的升高而减小;背压对贯穿距离、喷雾锥角、喷雾轴心速度和浓度衰减率的影响均大于启喷压力。     

双跨转子联轴器偏角不对中试验测量与分析

转子系统联轴器不对中是旋转机械频发的故障之一,尤其体现在多跨多轴系转子系统。模拟双跨-三支撑转子系统建立有限元模型,利用坎贝尔图得出一阶临界转速;搭建双跨-三支撑转子系统试验装置,试验测得在联轴器偏角不对中故障影响下,转子系统振动的频谱图、轴心轨迹和时域波形,分析转子系统振动特性。试验结果表明:随着偏角不对中量的不断增大,转子系统在通过临界转速时,1倍频振幅的增长倍率呈现递增趋势;转子在升速过程中,在偏角不对中故障影响下,2倍频伴随升速过程,且轴心轨迹会呈现"8"字形;在偏角不对中故障影响下,3倍频在通过临界转速时,其增长倍率最大;对于三支撑系统,与联轴器不同侧的转子系统受到联轴器偏角不对中振动的影响很小。     

国际

正全球能源格局轴心或逐渐由中东向西半球转移中国石油经济技术研究院18日发布的一份报告指出,随着油砂、盐下油和页岩油气资源成为能源"新宠",全球能源格局轴心已出现由中东向西半球转移之势,世界石油新版图逐渐浮出水面。《国外石油科技发展报告(2013)》指出,加拿大油砂、美国页岩油气和巴西深海"盐下油"资源丰富,     

多跨转子系统联轴器偏角不对中试验研究

为了减少多跨转子系统联轴器不对中故障,建立了双跨-三支撑转子系统试验装置,对试验转子系统进行有限元分析,将有限元结果与试验测得的临界转速进行对比验证,并测得联轴器偏角不对中条件下转子系统频谱图、轴心轨迹和时域波形。结果表明:随着偏角不对中量的不断增大,转子系统在通过临界转速时,1倍频振幅的提升倍率呈递增趋势;转子升速过程中,在不对中量的影响下,2倍频伴随整个升速过程,且轴心轨迹呈现"8"字形;在不对中量的影响下,3倍频在通过临界转速时的振幅提升倍率最大;对于双跨-三支撑转子系统,与联轴器在异侧的转子受联轴器偏角不对中振动的影响很小。     

A Methodology to Simulate the Impact of Tube Fouling on Steam Generator Performance With a Thermal-Hydraulic Code

ABSTRACT

Corrosion product deposits in the secondary side of nuclear plant steam generators may result in tube fouling. Tube fouling is a deposit that is influential for the heat exchanges between the primary and the secondary circuits. It may cause a steam pressure decrease and a power reduction. This paper presents a methodology to simulate the impact of tube fouling on steam generator performances. Simulations are performed with ThermoHYdraulique des Composants, which is Electricité de France reference code for the three-dimensional (3D) modeling of two-phase thermal-hydraulic flows in whole nuclear components such as steam generators. Tube fouling induces an additional thermal resistance on tubes. This resistance is supposed to correspond to the conductive resistance of a dense deposit by using the Maxwell model for a continuous solid phase with inclusions. As fouling deposit thicknesses are not uniformly distributed on the tube bundle, several thermal resistance distributions are investigated. In most cases, tube fouling concentrated in the hot leg is the most influential distribution. Nevertheless, for a large amount of deposits, tube fouling uniformly distributed in both hot and cold legs becomes more influential. This simulation series is an initial step. The strategy to improve the thermal resistance model is discussed.     

排气门正时对柴油机冷起动性能的影响

通过在一台单缸直喷柴油机上进行实验,分析了不同排气门正时条件对柴油机冷起动过程燃烧及排放性能的影响.结果表明,通过调节排气门关闭正时,适当增大缸内残余废气量,可显著改善起动过程初始着火循环的着火燃烧性能和提高起动过程缸内燃烧的稳定性.不同排气门关闭条件对起动过程的排放有着非常重要的影响.适当提前排气门关闭时刻,可以显著降低冷起动过程的烟度排放,特别是降低冷起动过程初始阶段的烟度排放.而对于NO2排放,由于残余废气具有很强的热效应,随着排气门关闭时刻提前,Nox排放呈上升趋势.     

Development of cold‐hot water dispenser with thermoelectric module systems

In the present study, the results of a cold‐hot water dispenser with a thermoelectric module system (TMS) are presented. The cold‐hot water dispenser with thermoelectric module system consists of a cold water loop, a hot water loop, a coolant loop, and a thermoelectric module. The thermoelectric cooling and heating modules consist of four and two water blocks, nine and three thermoelectric plates, respectively. The cooling and heating capacities obtained from the cold‐hot water dispenser with TMS are compared with those from a conventional cold‐hot water dispenser with a compression refrigeration system (CRS). As compared with the conventional cold‐hot water dispenser with CRS, the cold‐hot water dispenser with TMS can be operated at the minimum cold water temperature of 10 to 13°C and the maximum hot water temperature of 65°C. The obtained results are expected provide guidelines to design cold‐hot water dispensers with TMS.     

Experimental study on a small scale of gas hydrate cold storage apparatus

To have an overall investigation of cold storage characteristics to help to promote the application, a novel small scale of gas hydrate cold storage apparatus was designed. The amount of cold energy, growth rate, Hydrate Packed Factor (HPF) and overall heat transfer coefficient during the cold storage process were calculated and analyzed under different heat exchangers, sodium dodecyl benzene sulfonate (SDS) concentrations, hydration enhancement ways, inlet coolant temperatures and flow rates, etc. Results show that the cold storage performance could be improved greatly by adding a heat exchanger with vertical metal fins; SDS with concentration of 0.04 wt.% could help to improve the cold storage performance effectively. In addition, decreasing of the coolant temperature or increasing of the coolant flow rate could also make the amount of cold storage increased; it was found that mechanical blending for 5 min was the better hydration enhancement way than others, which presents the perspective for practical application.     

Proposal and thermodynamic performance study of a novel LNG-fueled SOFC-HAT-CCHP system with near-zero CO2 emissions

The cold energy in many liquefied natural gas (LNG) satellite stations is directly carried away by air or seawater. This causes cold energy waste and environmental cold pollution. To solve this problem, a combined power, heating and cooling system (CCHP) driven by LNG is established based on solid oxide fuel cell (SOFC) and humid air turbine (HAT), namely SOFC-HAT-CCHP system, in which, not only can the waste cold energy cool compressor inlet air to decrease power consumption, but supply cold energy for the cold storage and CO₂ recovery. Based on FORTRAN and Aspen Plus, the thermodynamic performance calculation models and the simulation work of the new system are carried out, such as the exergy and energy analysis, as well as the effects of the selected important variables. The results indicate that total exergy efficiency and total power efficiency are 64.7% and 54.4%, and the total thermal efficiency is 79.1%. Besides, the capture rate and purity of the CO₂ are 98.7% and 98.9% respectively. The novel system is environmental protective, energy-saving and efficient, which may provide a new direction to reasonably utilize the waste cold energy in LNG satellite stations.     

Effect of cold flow improvers on flow properties of soybean biodiesel

The influence of three cold flow improvers, namely, olefin-ester copolymers (OECP), ethylene vinyl acetate copolymer (EACP) and polymethyl acrylate (PMA), on the low-temperature properties and viscosity–temperature characteristics of a soybean biodiesel was evaluated on a low-temperature flow tester and a rotatory rheometer. The crystal morphologies of the biodiesel at low temperatures were investigated through a polarizing microscope. The results indicated that the ability of the cold flow improvers differed in improving the cold flow properties of soybean biodiesel, of which OECP was the best candidate. OECP can significantly reduce pour point (PP) and cold filter plugging point (CFPP) of biodiesel and retard viscosity increase of biodiesel at low temperatures when incorporated into biodiesel at the additive contents of 0.03%. On the other hand, OECP functioned by inhibiting the wax crystals from growing to a larger size and provided a barrier to crystal agglomeration at low temperatures, thus improving the cold flow properties of soybean biodiesel.     

Cold start characteristics of proton exchange membrane fuel cells

In this study, the effects of the start-up temperature, load condition and flow arrangement on the cold start characteristics and performance of a proton exchange membrane fuel cell (PEMFC) are investigated through in-situ experiments with the simultaneous measurements of the current and temperature distributions. Rather than the commonly recognized cold start failure mode due to the ice blockage in cathode catalyst layer (CL), another failure mode due to the ice blockage in flow channel and gas diffusion layer (GDL) leading to significantly high pressure drop through cathode flow field is observed at a start-up temperature just below the lowest successful start-up temperature. Three ice formation mechanisms are proposed, corresponding to the ice formations in cathode CL, GDL and flow channel. The general distributions of current densities and temperatures during the constant current cold start processes are similar to the constant voltage cold start processes, except that the temperatures at the end of the constant current cold start processes are more evenly distributed over the active reaction area because of the increased heat generation rates. The cold start characteristics are mainly dominated by the cathode flow, and changing the flow arrangement has unimportant impact on the cold start performance.     

The effects of long-term storage on the cold flow properties and viscosity of canola-based biodiesel

In this study, the effects of long-term storage on the viscosity and cold flow properties of biodiesel were investigated. Canola oil with a high content of unsaturated fatty acid was used to produce biodiesel in the experiments. Biodiesel sample was kept in ordinary atmospheric storage conditions for 6 months. The samples were taken from the biodiesel feedstock in every 30 days and cold flow properties and kinematic viscosity of the samples were measured. During 6-month storage, no significant deterioration was observed in cold flow properties and kinematic viscosity of biodiesel. Additionally, the same pour point (PP) and cold filter plugging point (CFPP) values (?11°C) were obtained during this period.     

Heat pipe based cold energy storage systems for datacenter energy conservation

In the present paper, design and economics of the novel type of thermal control system for datacenter using heat pipe based cold energy storage has been proposed and discussed. Two types of cold energy storage system namely: ice storage system and cold water storage system are explained and sized for datacenter with heat output capacity of 8800 kW. Basically, the cold energy storage will help to reduce the chiller running time that will save electricity related cost and decrease greenhouse gas emissions resulting from the electricity generation from non-renewable sources. The proposed cold energy storage system can be retrofit or connected in the existing datacenter facilities without major design changes. Out of the two proposed systems, ice based cold energy storage system is mainly recommended for datacenters which are located in very cold locations and therefore can offer long term seasonal storage of cold energy within reasonable cost. One of the potential application domains for ice based cold energy storage system using heat pipes is the emergency backup system for datacenter. Water based cold energy storage system provides more compact size with short term storage (hours to days) and is potential for datacenters located in areas with yearly average temperature below the permissible cooling water temperature (∼25 °C). The aforesaid cold energy storage systems were sized on the basis of metrological conditions in Poughkeepsie, New York. As an outcome of the thermal and cost analysis, water based cold energy storage system with cooling capability to handle 60% of datacenter yearly heat load will provide an optimum system size with minimum payback period of 3.5 years. Water based cold energy storage system using heat pipes can be essentially used as precooler for chiller. Preliminary results obtained from the experimental system to test the capability of heat pipe based cold energy storage system have provided satisfactory outcomes and validated the proposed system concept.     

Cold pre-compression of membrane electrode assembly for PEM fuel cells

Direct compression from the land structure of bipolar plate in a PEM fuel cell is considered as an important factor for the higher performance under the land than under the channel areas. Therefore the objective of this study is to determine if a cold pre-compression treatment on the whole membrane electrode assembly (MEA) area may have a significant positive effect on the overall performance of the cell. Five different levels of cold pre-compression have been applied and the experimental results show that the overall performance of the cell first increases with the level of compression to a maximum, and then decreases. These results clearly show that cold pre-compression of the MEA can significantly enhance the performance of the entire cell and there exists an optimal level of compression. Results of electrochemical impedance spectroscopy (EIS) show that the cold pre-compression results in a significant reduction in charge transfer resistance, especially in the high current density region. Further study by the cyclic voltammetry (CV) shows that the electro-chemical area (ECA) is changed with the different cold pre-compressed MEAs and there exists an optimal compression that results in the maximum ECA.