Harmonics and inter harmonics estimation of DFIG based standalone wind power system by parametric techniques

This paper presents application of parametric techniques (Estimation of signal parameter by rotational invariance techniques (ESPRIT), Root multiple signal classification (Root MUSIC)) for the estimation of harmonics/inter harmonics produced by wind generator under constant, variable rotor speed, load imbalance. Accuracy of estimation by parametric techniques is checked on synthetic signal as well as signal extracted from DFIG based standalone system with constant rotor speed and balanced load condition. Further sliding window concept is applied to parametric techniques to estimate the harmonics/inter harmonics under variable rotor speed and load unbalance. Series of simulation results demonstrate the advantages of the sliding window ESPRIT over sliding window Root MUSIC in the estimation of harmonics and inter harmonics under variable rotor speed as well as load unbalance condition.     

The operation types and operation window for high-purity hydrogen production for the sorption enhanced steam methane reforming in a fixed-bed reactor

The operation types and operation window for high-purity H₂ production for the sorption enhanced steam methane reforming (SE-SMR) with Ni/Al₂O₃ catalyst and CaO sorbent in a fixed-bed reactor are investigated by an experimentally verified 2D numerical method. Four chemical reactions including steam reforming, water gas shift, global steam reforming, and CO₂ sorption are considered. The operation window is defined as the H₂ and CO molar fractions at outlet satisfying both y_H2,out ≥ 90% and y_CO,out ≤ y_CO,allow (= 1%, 2% or 3%) in dry base. Under the conditions of y_H2,out and y_CO,allow, there are six operation types, of which 2 types are within the operation window and 4 types are not within the operation window as the temperature, weight hourly space velocity (WHSV) and steam to methane (S/C) molar ratio vary. For a common case of S/C = 3, the operation windows for y_CO,allow = 3% at WHSV = 8.5 h^?1 and 42.5 h^?1 are located at 570–670 °C and 640–690 °C respectively, based on the parameters in this work. The operation window of temperature is wider with decreasing WHSV, and it becomes wider remarkably as the S/C ratio increases. The lowest temperature inside the operation window is 550 °C. The effects of the temperature, WHSV and S/C ratio on the operating types, y_H2,out and y_CO,out are also presented and discussed in details.     

Optical and thermo-mechanical properties of fine-grained transparent yttria ceramics fabricated by hot-press sintering for infrared window applications

In this work, highly transparent yttria ceramics Φ?=?55?mm in size were fabricated by a hot-pressing method with 1 at.% ZrO₂ or 12 at.% La₂O₃ as a sintering additive. For a 4-mm-thick specimen doped with ZrO₂, the in-line transmittance reaches 71.1% at 400?nm and 80.9% at 1100?nm, and the transmittance of the La₂O₃-doped specimen is comparable to that of the ZrO₂-doped specimen. By means of the relatively low sintering temperature of 1600?°C, the present samples exhibited very fine microstructures (<2?μm), giving rise to excellent mechanical strength levels (～200?MPa). With regard to the 1 at.% ZrO₂-doped specimen, the combination of high strength and high thermal conductivity (～10 W/m?K) substantially improved parameters related to the thermal shock resistance. The results of this study indicate that the hot-pressed transparent yttria ceramic doped with 1 at.% ZrO₂ is optically, mechanically, and thermally suitable for high-temperature IR window applications.     

四川盆地及周缘上奥陶统五峰组岩相特征

上奥陶统五峰组分为页岩段和观音桥段。对比分析四川盆地及周缘五峰组页岩气钻井岩心以及测试数据,根据岩心和全岩矿物组分特征,以硅质矿物(石英)、黏土矿物和碳酸盐矿物为三端元,进行岩相划分。页岩段可识别出4种岩相类型:硅质页岩、含黏土硅质页岩、含灰硅质页岩以及含灰黏土质页岩;观音桥段发育含介壳泥质灰岩。页岩气钻井实测数据表明,页岩段4类页岩岩相品质(有机碳含量、脆性矿物含量以及含气量)差异较大,硅质页岩品质最优,含灰黏土质页岩品质最差。页岩段岩相类型以及观音桥段分布特征受控于沉积环境。川南永川地区等相对浅水的区域页岩厚度较大,但是硅质页岩厚度较小,页岩段整体品质较差,不建议作为水平井靶窗;川南威远地区受古陆和古地形影响,硅质页岩厚度较小,也不建议作为水平井靶窗;川东南焦石坝、武隆、丁山以及南川地区硅质页岩厚度超过4 m,可作为水平井靶窗。     

砂轮振动对磨削区时变润滑效应的影响

为研究砂轮振动对磨削区压力、膜厚及温度的影响,建立考虑时变效应的砂轮振动磨削的润滑模型,分析陶瓷结合剂CBN砂轮磨削45~#钢的过程中的最大压力、最小膜厚和最大温度随振动的幅值、频率及砂轮速度的变化情况。结果表明:考虑砂轮振动的时变效应时,不同瞬时下的压力及膜厚变化较大;随砂轮振幅和频率的增大,当砂轮振动到最低点时最大压力及最大温度增大,最小膜厚减小,而振动到最高点时则相反;时变效应使最大压力、最小膜厚与最大温度出现了滞后现象;当砂轮速度增大时,最大压力减小、最小膜厚增大,这有利于润滑且能减少磨粒磨损,但是最大温度增大容易产生磨削烧伤和热变形,影响工件磨削后的表面质量,所以应据此选择合适的砂轮速度。     

模糊时间窗约束下的装配线物料配送方案优化

为解决装配线物料无法及时准确配送的问题,提出了一种动态的联合配送策略,在此基础上以最小化单个产品配送成本、最大化工位满意度为目标,建立模糊时间窗约束下的物料配送数学模型。利用NSGA-Ⅱ算法求解出最佳的工位组划分、小车出发时间和配送路径,并对配送小车容量及配送时间窗进行优化。利用Plant Simulation软件搭建某生产线仿真模型进行模拟,验证了配送方案的可行性。与一般配送策略进行对比,结果表明,在保证配送工位满意度的前提下,优化时间窗能进一步降低单个产品的配送成本。     

矿井水质评价的变权识别模型的建立及应用

根据属性识别理论,建立矿井水质的变权识别模型,利用污染贡献率确定权重系数,与其它评价模型相比,变权识别模型具有排序功能,实现了对矿井水水质有效的识别和更细微的区分。经对阜新市矿区地下水水质评价实例验证该模型是合理有效的,为矿井水水质评价和矿井水的治理与回用提供了一种新的方法。     

套管开窗侧钻工艺研究

套管开窗侧钻是提高老油田原油产能的一项有效措施，它能够节约钻井投资和地面建设投资。套管开窗侧钻广泛应用于油田的大修、处理套管损坏的井和油田中后期的挖潜增效。主要针对套管开窗侧钻工艺进行了系统全面的研究总结，得到了一些有用的结论。     

交叉双尖窄状多重温室与太阳能热利用

文章介绍了将日光温室进一步改造为内部成交叉双尖窄状的多重温室,并将这种特殊结构的温室安装在建筑物窗户外面下端的墙壁上,就构成一种窗户型太阳能热利用装置。文中详细论述了由此产生的众多优越性。     

生活与采暖热水机组合理设计

依据住宅人数、旅馆或医院床位数m、热水小时变化系数k、热水用水定额q、燃油燃烧效率η等参数的相互关系,推出不同功率燃油热水机组设备单台、双台、叁台工作时的相应流量、K、m、油耗等参数值,并列成表格,方便读者和用户根据建筑规模参考选用;对北京双半月停止市政热水采暖季节,也提出了生活与采暖热水机组合理选择与互补的设想。