Shearing Wind Helicity and Thermal Wind Helicity

在Ⅴ和ω分别地是速度和涡度向量的地方， Helicity 被定义为 H = Ⅴ·ω。许多工作指出了那越大他合法地是，天气系统的生活周期是越多 longer。然而，直接关系他合法地对天气系统的进化不够清楚。在这篇论文，这个概念他合法地作为砍被概括风他合法地(SWH ) 。动态地，平均 SWH 是，这被发现直接与天气系统的平均气旋的旋转的增加有关。身体上，事实上， SWH 在涡度方程是扭转学期和分叉学期的和，这也被指出。热风(TWH ) 作为 SWH 的衍生物，因为它连接温度地和垂直的风，他也合法地这里被讨论地。这二数量可能为诊断一个天气系统是有效的。这篇论文在圆柱的坐标使用这二数量学习飓风安德鲁的发展验证他们的实际使用。通过分析飓风， TWH 能很好描述象潜伏的热的强壮的传送对流和版本那样的飓风的特征，这被发现。SWH 是为为诊断飓风的发展诊断天气系统，而且一个有效天气系统的不仅好数量。

Contrasting Trend of Wintertime Wind Speed Between Near-surface and Upper Air in China During 1979-2021

The long-term height-resolved wind trend in China under global warming still needs to be discovered.To fill this gap,in this paper we examined the climatology and long-term(1979-2021)trends of the wintertime wind speed at the near-surface and upper atmosphere in China based on long-term radiosonde measurements.At 700,500,and 400 hPa,much higher wind speed was found over eastern China,compared with western China.At 300,200,and 100 hPa,maximum wind speed was observed in the latitude zone of around 25-35°N.Furthermore,westerly winds dominated most parts of China between 20°N and 50°N at altitudes from 700 hPa to 100 hPa.A stilling was revealed for the near-surface wind from 1979-2003.From 2004 onward,the near-surface wind speed reversed from decreasing to increasing.This could be largely due to the joint impact of reduced surface roughness length,aerosol optical depth(AOD),and increased sensible heat flux in the ground surface.The decrease of AOD tended to reduce aerosol radiative forcing,thereby destabilizing the planetary boundary layer(PBL).By comparison,the wintertime wind in the upper atmosphere exhibited a significant monotonic upward trend,albeit with varying magnitude for different altitudes.In the upper troposphere,the wintertime maximum wind was observed along a westerly jet stream,with a pronounced upward trend within the zone approximately bounded by latitudes of 25-50°N,particularly above 500 hPa.This accelerating wind observed in the upper troposphere and lower stratosphere could be closely associated with the large planetary-scale meridional temperature trend gradient.Besides,the direction for the wind at the near-surface and lower troposphere(925 and 850 hPa)exhibited a larger variance over the period 1979-2021,which could be associated with the strong turbulence of PBL caused by the heterogeneous land surface.For those pressure levels higher than 850 hPa,large wind directional variance was merely found to the south of 25°N.The findings from long-term radiosonde measurements in winter over China shed light on the changes in wind speed on the ground and upper atmosphere under global warming from an observational perspective.

Ceramic thermal wind sensor based on advanced direct chip attaching package

An advanced direct chip attaching packaged two-dimensional ceramic thermal wind sensor is studied.The thermal wind sensor chip is fabricated by metal lift-off processes on the ceramic substrate. An advanced direct chip attaching(DCA) packaging is adopted and this new packaged method simplifies the processes of packaging further. Simulations of the advanced DCA packaged sensor based on computational fluid dynamics(CFD) model show the sensor can detect wind speed and direction effectively. The wind tunnel testing results show the advanced DCA packaged sensor can detect the wind direction from 0 to 360 and wind speed from 0 to 20 m/s with the error less than 0.5 m/s. The nonlinear fitting based least square method in Matlab is used to analyze the performance of the sensor.

Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind

The purpose of this study is to improve the efficiency of the power generation system of a solar tower using fluid dynamics. The power generation system of a solar tower can be designed and constructed at relatively low cost. However, the energy output tends to be low for its physical size compared with other renewable energy production systems. The technical and scientific improvement of these types of generation systems has lost its momentum since the shutdown of the wellknown Spanish pilot plant “Manzanares Solar Chimney” in 1989, although it still has the potential to play a role in renewable energy in the future. We have focused on the tower component of the system to seek possible enhancements of the power output of the internal turbine. As a result of our fluid dynamic shape optimization, a diffuser-shaped tower was employed to increase the internal flow speed of a scaled model. The results show a remarkable improvement in the power output of the internal wind turbine.

Natural ventilation performance of single room building with fluctuating wind speed and thermal mass

Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates.Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed,wind direction,internal heat source and building structural thermal mass,the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation.From a new point of view,the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building fa-ade thermal mass effect.Given a same hourly turbulence intensity distribution,the wind speeds with 1 min frequency fluctuations were generated using a stochastic model,the modified GARCH model.Comparisons of natural ventilation profiles,effective ventilation rates,and air conditioning electricity use for a three-month period show statistically significant differences(for 80% confidence interval) between the new calculations and the traditional methods based on hourly average wind speed.

Erratum to “Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind” [Energy and Power Engineering Vol. 6 No. 11 (October 2014) 362-370]

The original online version of this article (Masataka Motoyama, Kenichiro Sugitani, Yuji Ohya, et al. (2014) “Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind”, 2014, 6, 362-370. http://dx.doi.org/10.4236/epe.2014.611031) was published in October, 2014.The author wishes to correct the following error in text and Figures 9-11.

Structure of ADAFs in a general large-scale B-field:the role of wind and thermal conduction

We have explored the structure of a hot flow bathed in a general large-scale magnetic field.The importance of outflow and thermal conduction on the self-similar structure of a hot accretion flow has been investigated.We consider the additional magnetic parameters β r,,z=c 2 r,,z /(2c 2 s),where c 2 r,,z are the Alfve'n sound speeds in three directions of cylindrical coordinates.In comparison to the accretion disk without winds,our results show that the radial and rotational velocities of the disk become faster,but the disk becomes cooler because of the angular momentum and energy flux which are taken away by the winds.Moreover,thermal conduction opposes the effect of winds and not only decreases the rotational velocity but also increases the radial velocity as well as the sound speed of the disk.In addition,we study the effect of the global magnetic field on the structure of the disk.Our numerical results show that all the components of a magnetic field can be important and they have a considerable effect on velocities and vertical structure of the disk.

基于U-net神经网络的油浸式变压器绕组流-热耦合快速计算

该文针对采用传统数值方法进行大型油浸变压器绕组温升仿真时间较长的问题,提出一种基于U-net神经网络训练的快速计算方法,可以迅速地预测变压器绕组温升及热点。首先,根据流热耦合原理筛选输入变量,并运用流热耦合方法计算不同工况下的输出结果,并将之制作成训练集和测试集。同时,详细讨论3个对网络训练影响最显著的超参数;其次,将归一化后的训练集输入U-net神经网络进行训练,并设置超参数最佳组合;最后,将预测集输入训练好的模型进行预测计算及反归一化操作,预测绕组热点与Fluent仿真结果相差仅0.44 K,单次仿真时间从200 s缩短为0.07 s。预测结果与实验温度平均误差最大为2.31 K,最小为0.98 K,预测方差为0.31左右。结果表明:该方法可用于快速获得油浸式变压器绕组的温度及热点,可满足变压器温度热点数字孪生的实时性仿真要求。

Effect of thermal diffusion and electrostatic force on evolution of wind-blown sand flow

A theoretical model is suggested to mathematically describe the effect of thermal diffusion from a sand-bed on evolution of a wind-blown sand flow.An upward wind field is engendered by the thermal diffusion and the coupling interaction among the horizontal and upward wind flow,saltating grains,and a kind of electrostatic force exerted on the grains are considered in this theoretical model.The numerical results show that the effect of the thermal diffusion on the evolution process of wind-blown grain flow is quite obvious and very similar to the effect of the electrostatic force on the evolution.Not only the time for the entire system to reach a steady state(called the duration time),the transport rate of grains,the mass-flux profiles and the trajectory of saltating grains are affected by the thermal diffusion and the electrostatic force exerted on saltating grains, but also the wind profiles and the temperature profiles at the steady state are affected by the wind-blown sand flow.

考虑可再生能源配额的风水火多能源电力系统年度调度模型

通过分析配额制的实施对购电策略的影响,建立考虑可再生能源配额的风水火多能源电力系统的年度调度模型。为减小计算负担,将月度的负荷与风电用数个典型场景及其占比来表示。提出能够自动选择最佳聚类数的改进k-means算法,并应用于典型场景生成过程中。将同一天的负荷与风电的历史数据曲线拼接为一条功率曲线,并基于改进k-means算法进行聚类,得到考虑负荷与风电时序相关性的典型场景。仿真结果表明:(1)所提典型场景生成方法对年度电量刻画的精度平均提高了12.7%,由其所生成典型场景的平均符合率提高了20.25%,所提方法具有更好的年度电量刻画效果和更高的平均场景符合率;(2)当绿色证书的价格高于风电与火电价格差值时,实施配额制后能够提高风电的消纳量,这对绿色证书价格的确定具有重要参考价值。

基于时序运行模拟的水火风光储互补系统电源优化配置

系统时序运行模拟是水火风光储互补系统电源规模优化配置的关键环节。对于水火风光储多能互补系统8760逐小时运行模拟,按照小时尺度构建的模型规模很大,直接求解困难。本文提出按时间尺度逐层分解、递进优化的高效求解算法,精确模拟系统全年逐小时调度运行过程。在此基础上,构建双层规划模型对由风电、光伏、水电、火电、抽水蓄能、梯级水电站混合式抽水蓄能和电化学储能等电源组成的并网多能互补系统的电源容量进行优化配置。将模型应用在青海省电网系统中,对风电、光伏、抽水蓄能电站和基于水电站的可逆机组容量进行优化,得到电源最佳配置方案。

基于火电灵活性改造的可再生能源消纳系统成本优化

随着风电等可再生能源的大规模发展,带来了消纳难等新挑战,通过火电灵活性改造可以增强电力系统灵活调节能力、提升可再生能源消纳空间,同时需要考虑火电灵活性改造的经济性和对可再生能源消纳的影响。因此,综合考虑火电机组常规运行成本及灵活性改造后增加的各项成本,结合碳排放成本和弃风成本,建立以总成本最小为目标的火电灵活性改造前后优化调度模型,采用对比差值法计算基于火电灵活性改造的可再生能源消纳系统成本。通过算例,将所建模型应用于对比改造前后、不同碳排放强度、是否考虑弃风等不同方案下的机组运行状况及消纳系统成本大小,并拟合得到可再生能源渗透率和消纳系统成本的关系曲线,验证了模型的有效性。

红外热像技术辅助下探讨中药薰药治疗风寒湿痹型膝骨关节炎的临床研究

目的:观察中药熏药治疗风寒湿痹型膝骨关节炎(Knee Osteoarthritis,KOA)患者的临床疗效,并采用医用红外热成像仪进行疗效系统评价。方法:根据随机数字表法将60例风寒湿痹型KOA患者分为治疗组与对照组,对照组予口服艾瑞昔布片,治疗组在对照组治疗的基础上配合柳州市中医医院中药验方进行膝部中药熏药治疗。治疗8周后,比较两组治疗前后膝周疼痛视觉模拟评分法(Visual Analogue Scale,VAS)评分、西安大略和麦克马斯特大学骨关节炎指数量表(Western Ontario and McMaster Universities Osteoarthritis Index,WOMAC)评分、超敏C反应蛋白、红细胞沉降率、经络穴位皮温等的变化情况。结果:治疗组与对照组VAS评分和WOMAC评分及炎症因子水平较治疗前均显著降低(P<0.01),治疗组VAS评分和WOMAC评分及炎症因子水平均低于对照组(P<0.01);两组治疗后主要穴位均温显著高于治疗前(P<0.01),且治疗组较对照组的均温改善显著(P<0.01);治疗组愈显率显著高于对照组,两组患者的愈显率进行比较,P<0.05。结论:中药验方熏药治疗方案能改善风寒湿痹型KOA患者的证候和有效缓解疼痛,显著降低KOA评分和提高相应经络穴位的红外皮温,并通过红外热像技术得到证实,可为临床适宜技术推广与应用提供可靠的临床数据和值得借鉴的研究思路。

基于电磁-流热双向耦合的变压器绕组温升计算及结构参数优化

变压器温升是影响其运行状态和使用寿命的关键因素。为了更准确地得到油浸式变压器绕组区域的温度场分布,采用有限元法对绕组的电磁-流热耦合过程进行了数值研究。根据电磁场及流体-温度场分布的特点,建立了变压器及绕组区域的计算模型。基于异构网格节点数据映射方法,将电磁场分析得到的绕组非平均损耗作为热源边界条件加载到流体-温度场计算网格中,并根据每次迭代时的温度对该热源进行修正,实现电磁-流热的双向耦合。在此基础上,建立热点温度与绕组结构参数之间的响应面,开展了对绕组热点温度及导体材料用量最小化的多目标优化研究。采用非支配排序遗传算法(non-dominated sorting genetic algorithm,NSGA-Ⅱ)获得了Pareto最优解,并对Pareto前沿面上的4种优化方案进行了分析。结果表明,优化后的绕组热点温度及导体用量明显降低。该文研究为变压器结构的优化设计提供了一种可行方法。

风光热储互补发电系统容量配置技术研究

针对无常规电源支撑的风光热储互补发电系统,协调规划装机容量对提高发电系统运行经济性和利用率具有重要意义。提出了一种双层优化配置方法,上层以最小度电成本及弃电率为目标,确定系统装机容量;下层以新能源发电消纳最大为目标,解决功率分配问题。通过反复迭代寻优,得到系统容量配置;然后;通过纳什谈判对优化结果进行选择;最后,对甘肃河西地区数据进行仿真分析。结果表明:风光热储互补发电系统最优容量配置下的度电成本为0.3064元/(k W·h);风电场加光伏电站装机容量与光热电站装机容量的最优比为6:1,对比相同装机容量的风光互补发电系统,风光热储互补发电系统具有更高的稳定性。

变压器绕组热缺陷温度演化规律及其辨识方法

近年来变压器因绕组发生热故障烧毁时有发生,严重威胁电网安全。为保障变压器的安全稳定运行,开展了变压器绕组热缺陷温度演化规律及其辨识方法研究。首先,基于有限元法研究构建变压器绕组电磁-温度-流体多物理场耦合仿真模型,并通过温升试验验证仿真模型的有效性;然后,仿真分析绕组不同过热位置、热缺陷严重程度和运行工况对绕组局部区域温度的影响规律;最后,应用绕组轴向油道多点温度突变分析研究提出绕组热缺陷位置和严重程度辨识方法。研究结果表明:基于该文多场耦合仿真模型计算的温度值与温升试验实测值的误差小于6%;绕组不同区域发生热缺陷时,过热区域热量会沿油流导向路径快速传递,绕组油道内多点温升值会随其下方区域过热温度的增大呈现线性规律增长;该文提出的热缺陷辨识方法对热缺陷位置辨识的准确度为100%,对热缺陷温度估计的相对均方根误差为6.1%。采用该研究成果能及早发现变压器运行过程中绕组上的热缺陷,避免由缺陷向更严重的故障发展,保障变压器的安全运行。

风火打捆送出系统稳定特性研究和运行策略优化

为解决粤西海上风电集群与火电打捆送出的同步稳定问题,首先研究了风火打捆送出系统的同步稳定特性和影响因素,然后提出了提高风火打捆送出系统风电渗透率和同步稳定特性好的风电机组优先发电的运行方式优化策略。最后构建了风电场集群整体硬件在环接入的实时仿真系统进行验证,仿真结果表明所提出的同步稳定性提升策略可以提高风火打捆送出系统稳定极限,有力提升了风电并网消纳率和电网安全稳定水平。

考虑新能源爬坡的风光火耦合系统源荷匹配性分析及容量优化配置

风力发电、光伏发电与火力发电经同一点并网形成耦合系统,是我国北方地区发电侧灵活性调节电源与新能源间高效、低碳协同的一种形式.考虑区域新能源爬坡特性,结合源荷匹配分析,发掘和利用其规律,研究风光火耦合系统的容量优化配置方法,为耦合系统规划提供参考.首先,简述耦合系统运行模式和不确定性处理方法;其次,考虑耦合系统风光互补、爬坡事件和关键负荷特性,选取并提出相关指标用于源荷匹配评价;再次,考虑源荷特性、匹配、成本和收益等约束,建立耦合系统容量优化配置模型;最后,基于辽宁地区实际数据进行算例仿真,得到该地区耦合系统风、光的最优安装容量,并分析上述源荷相关因素与容量优化配置结果之间的相互影响,为新能源最优容量配置提供了参考与建议.

典型风电场地形大气稳定度对风机出力的影响

[目的]分析了大气稳定度对风机出力的影响,为提高计算流体动力学(Computational Fluid Dynamics,CFD)风能资源模拟精度提供技术参考。[方法]选取立于平坦和复杂山地两类典型地形上的两座测风塔不同高度的风速、气温、气压等观测数据,使用莫宁-奥布霍夫长度法分别计算两座测风塔所在区域的大气稳定度,参照Irwin大气稳定分类标准对稳定度计算结果分类,再根据分类结果进行两座测风塔轮毂高度处出力分析。[结果]结果表明:在近地面层,复杂山地大气热效应造成的表层垂直混合作用更为明显,造成的大气不稳定性较为强烈,但垂直混合作用不充分;复杂山地大气稳定度对风机出力的影响大于平坦地形,其不确定性更强。[结论]在进行CFD风电场流体建模时需要考虑大气稳定度的影响,特别是超低风速复杂山地场址条件下,大气稳定度的评估对风机选型及发电量仿真精度尤为重要。

建筑热羽流影响下空气污染物跨楼层扩散特性

采用风洞实验和数值模拟,以单侧通风6层建筑为研究对象,考虑水平来流和太阳辐射引起的近壁面热羽流的耦合作用,探究了不同理查德森数Ri下建筑壁面热流运动、温度分布及污染物在竖直方向的跨楼层扩散传播特性。研究表明:当Ri≤5.64时,水平风力占主导,建筑2/3高度以下迎风面有明显的下行及向两侧的流动,1层释放的污染物对2层及以上楼层几乎没有影响,此时归一化净逃逸速度NEV~*基本保持不变;当Ri>5.64时,壁面热浮升力作用不能被忽略,随着Ri的增大,NEV~*明显增大,表明有更多污染物从1层室内扩散出来,沿迎风面向上运动的热流对高层室内产生影响,导致污染物跨楼层传播的风险增大。