Numerical and experimental studies of flow field in hydrocyclone with air core

For the flow field in a d50 mm hydrocyclone, numerical studies based on computational fluid dynamics (CFD) simulation and experimental studies based on particle image velocimetry (PIV) measurement were carried out respectively. The results of two methods show that air core generally forms after 0.7 s, the similar characteristics of air core can be observed. Vortexes and axial velocity distributions obtained by numerical and experimental methods are also in good agreement. Studies of different parameters based on CFD simulation show that tangential velocity distribution inside the hydrocyclone can be regarded as a combined vortex. Axial and tangential velocities increase as the feed rate increases. The enlargement of cone angle and overflow outlet diameter can speed up the overflow discharge rate. The change of underflow outlet diameter has no significant effect on axial and tangential velocities.

Effect of air core on the shape and discharge of the outflow through a bottom outlet

Experiments were conducted to study the generation of air core and its effect on the outflow shape and discharge in a cylindrical water tank with a bottom well-designed outlet. Depending on the stages of the air core in the tank, the outflow shape can vary from a smooth water jet to a smooth spindle shape with air-core, and to water sprays. The diameter of the nozzle size also has influence on the outflow pattern. The existence of the penetrated air core can dramatically reduce the outflow discharge, with the discharge coefficient decreasing with the nozzle diameter.

Air Cored Rogowski Coil for Measurement of Partial Discharges

A Rogowski coil was designed to measure partial discharge （PD） signal with low currents and high frequency. The possibilities of obtaining better measurements of PDs were explored by changing the inductance, mutual inductance, resistance, and capacitance of the coil. The designed Rogowski coil was calibrated under square wave voltage and arbitrary sine wave voltage. Then, according to the parameters of the Rogowski coil, the effect of changing some of these variables was simulated using a bode plot. Comparison shows that the simulation results were consistent with the experimental ones. A needle-plate in air gap model was set up and its PD under impulse voltage was measured. The results demonstrate that the Rogowski coil is adapted to measurement of PDs.

DESIGN OF THE AIR-CORE TRANSFORMER IN SPHERICAL TOKAMAK

An ideal current distribution in the air core transformer coils is obtained using variation principle.Climbing mountain method is utilized for optimizing the dimension and position of the real coils.Not only can the requirement of minimizing the stray field in the plasma region be guaranteed,but also integer turns for the coil can be realized.The latter brings a significant convenience to engineering.

Numerical Analysis of Magnetic Force of Dry-Type Air-Core Reactor

This paper presents a coupled magnetic-circuit method for computing the magnetic force of air-core reactor under short-time current. The current and the magnetic flux density are computed first and then the magnetic force is obtained. Thus, the dynamic stability performance of air-core reactor can be analyzed at the design stage to reduce experimental cost and shorten the lead-time of product development.

Calculation and Design of Dry-type Air-core Reactor

Based on the method of compound and additional conditions under the conditions of the equal temperature rise and the equal potential drop (P.D.) of resistance, the application of design software of dry-type air-core reactor is introduced in this thesis. The analytical methods of the inductance are also given. This approach is proved entirely feasible in theory through the simplification with Bartky transformation, and is able to quickly and accurately calculate reactor inductance. This paper presents the analytical methods of the loss of dry-type air-core reactor as well.

Seasonal air temperature variations retrieved from a Geladaindong ice core, Tibetan Plateau

A 70-year history of precipitation δ^18O record has been retrieved using an ice core drilled from a plat portion of the firn area in the Guoqu Glacier （33°34＇37.8″ N, 91°10＇35.3″ E, 5720 m a.s.l.） on Mt. Geladaindong （the source region of Yangtze River） during October and November, 2005. Based on the seasonality of δ^18O records and the significant positive relationships between monsoon/non-monsoon δ^18O values and summer/spring air temperature from the nearby meteorological stations, the history of summer and spring air temperature have been reconstructed for the last 70 years. The results show that both summer and spring air temperature variations present similar trends during the last 70 years. Regression analysis indicates that the slope of the temperature-δ^18O relationship is 1.3℃/‰ for non-monsoon δ^18O values and spring air temperature, and 0.4℃/‰ for monsoon δ^18O values and summer air temperature. Variation of air temperature recorded in the ice core is consistent with that in the Northern Hemisphere （NH）, however, the warming trend in the Geladaindong region is more intense than that in the NH, reflecting a higher sensitivity to global warming in the high elevation regions. In addition, warming trend is greater in spring than in summer.

Atmospheric Methane over the Past 2000 Years from a Sub-tropical Ice Core, Central Himalayas

A high-resolution 2ooo-year methane record has been constructed from an ice core recovered at 7200 m a.s.1, on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend in the concentration of methane during the industrial era that is similar to observations from polar regions. However, we also observed the differences in the atmospheric methane mixing ratio between this monsoon record and those from polar regions during pre-industrial times. In the time interval o N 1850 A.D., the average methane concentration in the Dasuopu ice core was 782±40 ppbv and the maximum temporal variation exceeded 200 ppbv. The difference gradient of methane concentration in Dasuopu ice core with Greenland and Antarctica cores are 66±40 ppbv and 107±40 ppbv, respectively. This suggests that the tropical latitudes might have acted as a major global methane source in preindustrial times. In addition, the temporal fluctuation of the pre-industrial methane records suggests that monsoon evolution incorporated with high methane emission from south Asia might be responsible for the relatively high methane concentration observed in the Dasuopu ice core around A.D. 800 and A.D. 1600. These results provide a rough understanding of the contribution of tropical methane source to the global methane budget and also the relationship betweenatmospheric methane and climate change.

Late Holocene glacier variations indicated by theδ18O of ice core enclosed gaseous oxygen in the central Tibetan Plateau

Theδ18O of ice core enclosed gaseous oxygen(δ18Obub)has been widely used for climate reconstruction in polar regions.Yet,less is known about its climatic implication in the mountainous glaciers as the lack of continuous record.Here,we present a long-term,continuousδ18Obub record from the Tanggula glacier in the central Tibetan Plateau(TP).Based on comparisons of its variation with regional climate and glacier changes,we found that there was a good correlation between the variation of theδ18Obub in this alpine ice core and the accumulation and melting of this glacier.The more developed the firn layer on glacier surface,the more positive theδ18Obub.Conversely,the more intense the glacier melting,the more negative theδ18Obub.Combined with the chronology of ice core enclosed gases,the glacier variations since the late Holocene in the central TP were reconstructed.The result showed that there were four accumulation and three deficit periods of glaciers in this region.The strongest glacier accumulation period was 1610-300 B.C.,which corresponds to the Neoglaciation.The most significant melting period was the last 100 years,which corresponds to the recent global warming.The Medieval Warm Period was relatively significant in the central TP.However,during the Little Ice Age,there was no significant glacier accumulation in the central TP,and even short deficit events occurred.Comparisons of the late Holocene glacier variation in the central TP with glacier and climate variations in the TP and the Northern Hemisphere showed that it was closely related to the North Atlantic Oscillation.

STUDY OF STRUCTURE AND RIGIDITY OF AIR-JET TEXTURED YARN(ATY)

This paper deals with the structure of air-jet textured yarn(ATY),especilly its core structurein dedail.It is described that overfeed of supply yarn does influence the ATY structure.Then thebending rigidity of ATY has been measured and analyzed.The results shows that various supplyyarns affect the core structure and bending rigidity of ATY.

基于小波分析的空心电抗器匝间短路磁场探测方法研究

为了解决目前干式空心电抗器匝间短路检测方法灵敏度和准确度不足的问题,根据故障发展期探测线圈感应电压的异常变化,提出一种新的基于小波分析的空心电抗器匝间短路磁场探测方法。首先,对电抗器故障发展期探测线圈电压信号进行仿真分析,得到电抗器不同位置匝间短路时探测线圈信号变化特征。再基于信号分解小波系数中有用信号与噪声相对比值最大的原则,逐层自适应选取最优小波基函数,利用小波变换对信号进行阈值去噪,提取故障特征量从而实现对电抗器匝间短路发展期及时准确地判断,避免故障进一步发展。通过搭建电抗器匝间短路故障检测系统实验平台,验证了基于小波分析磁场探测法的灵敏度和可靠性,为电抗器的安全稳定运行提供有效保障。

现行岩心录井标准中存在的问题及修订建议

目前国内制定的钻井取心、井壁取心、地质录井等标准均涉及岩心录井的部分内容,对现场岩心录井作业都有一定的指导作用。但随着非常规油气勘探开发的推进,现行标准中存在的一些试验参数不明确、含油气级别划分不精细、岩心整理方法相对落后、岩心管理信息量较少等问题也日渐显露。针对现行标准中存在的问题进行修订,为此提出的修订建议是:通过恒温定时确定岩心密闭试验最佳参数为60℃恒温加热120 min,根据不同储层性质精细划分含油气级别、制定泥页岩储层岩心含油气级别,变更岩心标号原则、打印代替手写标识,岩心卡片以“二维码”形式呈现。这些修订建议有利于提高岩心录井观察试验的科学性、减小录井成本、增加时效,促进岩心录井的信息化发展。

空心变压器电路反映阻抗的深入研究

现有教材分析空心变压器电路时,对反映阻抗的阐述不够深入,使用的电路实例过于简单,读者困惑于各类阻抗的具体细节。通过详细的计算推导,揭示反映阻抗与回路阻抗本质,完善反映阻抗公式,给出电路去耦模型及分析方法,并借助两个复杂实例阐述其在电路计算中的便利性。通过三个概念(一次与二次回路阻抗、一次开路电压)、三组公式(两组反映阻抗、二次开路电压),直接计算变压器电路的一次与二次回路电流,丰富教材内容。

不同芯丝对喷气涡流包芯纱及其织物性能的影响

为探究不同芯丝对喷气涡流包芯纱及其织物性能的影响规律,以莫代尔纤维和智能调温纤维为外包纤维,分别以T400长丝、涤纶DTY长丝和锦纶6长丝为芯丝纺制3种包芯纱,并织成针织物。探讨相同成纱条件下不同芯丝喷气涡流包芯纱的强伸性能、毛羽以及条干均匀度,同时分析相应针织物的悬垂性、耐折皱性和抗起毛起球性。结果显示:芯丝为T400长丝的包芯纱强伸性能最好,且其织物的抗起毛起球性最好;芯丝为涤纶DTY长丝的包芯纱织物挺括抗皱,保形性较好;芯丝为锦纶6长丝的包芯纱毛羽最少、条干最均匀,并且织物悬垂性、透气性最好。

汉麻秆芯粉体制备方法的研究进展

由于汉麻本身具有天然的杀菌成分和良好的透湿透气性能,使其在纺织界逐渐受到重视。传统汉麻的外层韧皮纤维利用率较高,但汉麻秆芯则会被当做燃料焚烧或直接作为农业废物填埋掉,这部分大概占汉麻纤维产量的70%~80%。对汉麻秆芯能源的开发利用需要进行粉碎加工处理,以便进一步应用。以汉麻秆芯粉体制备理论、制备方法为研究对象,讨论了锤式粉碎、气流式粉碎、振动式粉碎等工艺技术,为汉麻秆芯粉体的转化利用做好前期处理工序准备。

喷气涡流纺纱机的发展现状及趋势

为了进一步推进喷气涡流纺纱机的发展,分析了喷气涡流纺纱机在全球的存量分布情况、近8年国内累计进口量及主要省份等市场情况,回顾了喷气涡流纺纱机的国内外技术发展历程,阐述了喷气涡流纺纱技术的创新应用,介绍了相关政策支持,并提出了喷气涡流纺纱机的发展思路。认为:我国喷气涡流纺纱机存量具有全球优势地位,正处于产业快速发展期,市场空间广阔,未来随着各种新工艺新技术层出不穷,在开发喷气涡流纺花式纱、包芯纱、细号纱以及差异化原料应用的优势将不断凸显,但国内急需开发拥有自主知识产权的喷气涡流纺纱机,突破关键技术装备和工艺,促使喷气涡流纺纱机在我国稳步健康发展。

基于磁场检测的干式空心电抗器匝间短路故障诊断方法

匝间短路故障是干式空心电抗器最常见的故障,严重时会引起电抗器绝缘损坏、起火,甚至烧毁。及早诊断电抗器匝间短路故障,发出有效预警对电力系统安全运行具有重要意义。该文提出一种基于磁场检测的干式空心电抗器匝间短路故障诊断方法:独立于电抗器本体,上下安装与电抗器绕组同轴的检测线圈,通过检测线圈感应电压的变化,采用基于数理统计的准确识别匝间短路过程的3σ判据模型和算法,判断电抗器匝间短路故障并进行预警和报警。基于有限元数值计算软件,以一台型号为BKGKL-20000-35干式空心电抗器为研究对象,仿真分析了电抗器在不同位置发生匝间短路故障时检测线圈的感应电压变化规律,验证所提出方法的有效性。最后通过对试制样机的现场试验,验证了该方法实用可靠,可推广应用于实际电力系统中。

干式空心并联电抗器绕组匝间绝缘故障特征分析

本文通过有限元软件建立仿真分析模型,研究干式空心并联电抗器绕组匝间绝缘故障的物理特征,探寻便于故障监测的敏感状态量。首先在有限元仿真软件中建立基于实际电抗器的“场-路”耦合模型并验证正确性,之后在其绕组不同层、不同高度位置设置匝间绝缘故障,研究回路总电流、等效阻抗、有功功率损耗等电气特征量随故障位置的变化规律,并分析空间磁感应强度和绕组受力的变化情况。结果表明:所研究的电气特征量变化率随绕组单匝匝间短路位置的变化而变化,在径向上呈现从内层到外层增大的趋势,在最外层有所减小,在轴向上由绕组中部向端部逐渐减小。绕组单匝匝间短路状态下的空间磁感应强度和故障绕组受力明显增大,等效电阻、功率因数和有功功率损耗的变化率均在500%以上,变化显著且方便获取,可作为干式空心并联电抗器匝间绝缘故障的在线监测量。

汽车空调管接头复杂塑件注塑模设计

为某汽车空调管接头复杂塑件的注射成型设计了一副两板式模具,解决了该塑件因结构复杂导致脱模困难、难以实现自动化注塑生产的实际问题。由于该塑件的圆柱壳主体上附加设置了90°弯管接口、斜置直管接口、法兰台直通管接口、直管+65°弯管接口等4个异型结构特征,导致塑件的脱模机构设计非常困难。为解决该问题,采用脱模方向集成分类法等设计方法将塑件的脱模机构按区域来设计,在定模一侧设计了6个定模滑块先抽芯机构用于90°弯管接口、斜置直管接口这两个特征的先抽芯脱模,6个机构的抽芯动作由定模侧增加的一侧开模打开进行机械式驱动完成定模先抽芯动作。在模具动模一侧设置了4个脱模机构,包括2个滑块机构、1个滑块+弯管复合机构和1个大尺寸推管机构。分别由斜导柱和油缸驱动2个滑块机构,用于法兰台直通管接口脱模。滑块+弯管复合机构用于直管+65°弯管接口特征的脱模,先由斜导柱驱动滑块完成直线抽芯,后由油缸驱动弯管型芯带动直线抽芯滑块一起移动,完成65°弯管特征的旋转抽芯脱模。最后,由大尺寸推管机构顶出而实现塑件的完全脱模。

双路单喷口离心喷嘴的雾化特性实验研究

为满足燃气轮机喷嘴雾化质量的稳定性以及宽燃油调节范围的双重需求,提出一种双路单喷口离心喷嘴结构。利用高速摄影和马尔文仪,研究了喷嘴在三种供油模式下的流量特性和雾化特性(空气核芯、雾化锥角和索泰尔平均直径(SMD))。研究结果表明:双路单喷口离心喷嘴在双路同开时的总燃油流量小于主副油路单独供油时的燃油流量之和,且主副分路的流量占比保持不变。当主副油路旋流件的流道数均为4时,主副分路的流量占比为56.8%∶43.2%。与副油路单开相比,双路同开时的燃油流量最大提高了57.6%,雾化锥角减小了11%。与主油路单开相比,双路同开时的SMD在大流量工况下显著减小;将副油路旋流件流道数改为2时,主副分路的流量占比变为69.3%∶30.7%。流量占比的改变不会影响双路单喷口离心喷嘴在双路同开时的雾化锥角,但会影响喷雾的雾化粒径。副油路流量占比越高,双路同开时的雾化粒径越细,雾化性能越好。通过匹配双路单喷口离心喷嘴主副旋流件的结构参数,拓宽了燃油流量的调节范围,优化了高流量工况下的雾化锥角和雾化质量。