新能源汽车动力电池冷却系统热仿真及优化

动力电池的温度控制是新能源汽车发展中的一个难题,而电池冷却系统在动力电池的温度控制过程中起着相当重要的作用。利用Solidworks软件对电池包进行建模,利用ICEM CFD软件对电池包模型进行网格划分等前处理。利用Fluent软件并采用控制变量法分别对冷却管道截面宽度、冷却液质量流量和冷却液进口温度等3个对电池包散热性能影响较大的参数进行仿真计算和对比分析。根据仿真结果选择可优化电池包散热性能的参数,并在原方案基础上提出了一种新的冷却管道分布方案。经过仿真计算发现,该方案可有效降低电池在使用过程中的最高温度和温差,提高了电池冷却系统的散热性能。     

基于数值模拟的汽油机喷嘴结构优化CFD分析

以5WY-2817A汽油机喷嘴为研究对象,旨在提高该汽油机喷嘴流动特性,利用UG软件对喷嘴进行实体建模,通过喷雾稳态试验对模拟计算提供边界条件。利用AVL-FIRE软件进行喷嘴稳流三维数值计算,研究了不同压力室高度、喷孔分布直径和阀座锥角对喷孔处压力与速度的影响关系。研究结果表明,压力室高度0.2mm,喷孔分布直径1.4mm,阀座锥角43°时喷孔处燃油流动特性最佳。该结构优化可作为改善喷嘴雾化性能的最佳方案。     

Modeling and simulation of phase change material based energy storage system using fluid-solid coupling

固态电热储能技术可以有效地解决风电、光伏、核电等清洁能源消纳问题,成为大规模储能的研究热点之一。针对固态电热储能系统相变材料的传热性能进行研究,根据外置电阻式蓄热体结构特点,提出一种基于流固耦合的蓄热体建模与仿真方法,对流场、温度场耦合的问题进行三维数值模拟,从而得到蓄热体在不同工作时刻的温度场、流场分布。通过数值模拟结果与实验数据进行对比,验证流固耦合建模与分析方法的正确性。     

The system level heat dissipation analysis about energy storage

预装箱式储能系统,作为新型的工程形式,和传统的现场施工方式相比,能极大地节约工期。可靠的热设计是电池系统可靠安全运行的基础。本文基于有限元分析软件,针对复杂的锂电池储能系统,对不同热设计方案进行分析选择,对热设计的可靠性进行验证。     

Numerical optimization of the spatial conductivity distribution within cathode microstructures of lithium‐ion batteries considering the cell performance

A numerical approach targeting the optimization of the spatial conductivity distribution within a three‐dimensional electrode microstructure of lithium‐ion batteries is presented. Its methodology is based on a spatially resolved three‐dimensional electrochemical model of a lithium‐ion battery half cell on the particle scale. Although being independent of the underlying electrode microstructure, the method is exemplarily applied on a computer‐generated periodic electrode structure consisting of smooth spherical particles. In the first step, parameter variations are performed to investigate the influence of the electrical conductivity on the simulated half‐cell performance. The simulations show that the performance‐limiting effect of low electrical conductivity values can be attributed to a through‐plane directed inhomogeneity of the local intercalation flux density. Furthermore, it is shown that if a homogenous surface intercalation flux density is reached, a further increase of the spatially uniform conductivity would not result in better half‐cell performance. In the second step, the determined optimum spatially uniform conductivity value is taken as a basis for the spatial optimization approach. The resulting conductive structure within the electrode shows gradient‐like behavior directed perpendicular to the electrode surface, while highest conductivity values are to be expected in the region close to the current collector. Therefore, multiple layer coating is suggested as a suitable practical manufacturing approach. Due to the proposed two‐stage optimization approach, the resulting conductive structure reveals conductivity saving potential without altering the macroscopic cell performance.     

Numerical simulation of high‐temperature phase change heat storage system

In this paper, numerical results pertaining to cyclic melting and freezing of an encapsulated phase‐change material (PCM) have been reported. The cyclic nature of the present problem is relevant to latent heat thermal energy storage system used to power solar Brayton engines in space. In particular, a physical and numerical model of the single‐tube phase change heat storage system was developed. A high‐temperature eutectic mixture of LiF‐CaF₂ was used as the PCM and dry air was used as the working fluid. Numerical results were compared with available experimental data. The trends were in close agreement. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(1): 32–41, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10132     

Application of lithium battery with mobile container energy system

锂电池一体化箱式移动电源系统主要应用于新能源较为丰富,供电电网薄弱,供电质量要求较高,占地面积有限和多种突发临时性供电需求等地区.该电源系统由电池组,电池管理系统(BMS),双向变流器(PCS),能量管理系统(EMS)及智能辅助系统组成.通过对系统功能单元的构成,各部分功能特性以及关键技术突破三方面进行讨论,在此基础上展望一体化箱式移动电源系统的发展方向和应用前景,为该类型电源系统的创新和推广提供借鉴.     

储能与液流电池技术

大规模高效储能技术是解决可再生能源发电不连续、不稳定、不可控特性的重要途径,也是构建坚强智能电网的核心技术。本文对各种储能技术进行了综合分析,并对适用于大规模储能的抽水储能、压缩空气储能、钠硫电池、锂离子电池、铅酸电池和液流电池的技术特点、优劣势、发展前景进行了深入阐述;最后,对储能技术的发展思路进行了探讨,认为坚持技术开发与应用示范并重,进一步降低储能设备成本,提高其可靠性和稳定性并辅以一定的鼓励政策,是推进储能技术的产业化和实用化的重要途径。     

微喷管内气体流动的实验研究与数值模拟

通过实验和数值模拟来研究气体在渐缩微喷管内流动,基于连续介质模型研究了二维微喷管内的流场及推力特性,研究分析了流量和气体入口温度对微喷管流场结构和喷管性能的影响。研究结果表明,随着流量的不断增加,气体稀薄效应相应减小,粘性力对喷管流动的影响降低,边界层逐渐变薄,马赫数不断增大,微喷管的推力大小近似与流量成线性变化,但流量变化对微喷管流场结构影响并不显著。当温度增大时,粘性损失对喷管影响较大,导致边界层变厚,影响了微喷管推进性能,流场马赫数和微喷管推力随温度的升高而下降,说明低温气体有利于提高微喷管的推进性能。     

水力旋流器流场的数值模拟研究

用计算流体力学软件FLUENT，采用RSM模型对油水分离用水力旋流器的流场进行了数值模拟。模拟结果表明旋流器流场呈Rankine涡的特点，且与他人实验结果吻合较好，说明该湍流模型和算法是可行的；旋流器上游区内流体紊流现象严重，两侧有循环流存在，这都对两相分离不利，应改进结构以改变这种流动形式；另外还对油-水两相流场进行了研究．初步揭示了液-液两相分离的现象，这都为进一步研究旋流器的结构优化提供了参考。     

中速磨煤机构件对气相场影响的数值模拟

中速磨煤机内部气相场研究对于燃煤电厂节能减排降碳具有重要意义。然而,中速磨煤机内部构件复杂且存在旋转部件,已有研究往往对磨煤机结构及运行进行简化处理,这势必影响气相场模拟的准确性。采用Realizable k-ε湍流模型,对7种不同结构及运行工况下磨煤机内部气相场开展数值模拟,进行网格无关性验证,并评价磨辊、磨碗与风环、分离器的简化处理对气相场数值模拟结果的影响。结果表明,忽略磨辊对研磨区气相场影响明显,而磨辊转速由28.62r·min^-1变化为57.24 r·min^-1时,典型截面气相速度和磨煤机压力损失几乎不变;忽略磨碗与风环的转动,风环上方平均风速将被低估14.97%,磨煤机压力损失将被低估5.02%;忽略分离器部分对研磨区气相场影响很小,而对研磨区上方内锥体区域气相场影响显著,并使得典型截面气相速度误差高达4.80 m·s^-1。研究结果可为磨煤机内部流场准确、高效的数值模拟提供方法指导。     

Numerical investigations on unsteady flow of a scroll expander for compressed air energy storage

本工作以适应用于微型压缩空气储能（micro-CAES）系统的涡旋膨胀机为研究对象,采用计算流体力学（CFD）的方法对涡旋膨胀机工作过程进行非定常数值模拟,得到膨胀机内部温度场、压力场和速度场的分布,研究了吸气温度对涡旋膨胀机性能的影响规律及工作腔流场分布特点,结果显示：膨胀机吸气温度的升高,能够增加单位质量流量的输出功;随着吸气温度的下降,动涡旋盘所受轴向气体力增大,径、切向气体力减小;膨胀机工作过程中工作腔内的温度分布并不是沿涡旋盘半径方向逐渐下降,两侧背压腔存在较大的机械能损耗,背压腔温度会高于上游排气腔。该研究结果为涡旋膨胀机排气结构的设计提供了理论依据。     

连铸中间罐内流场和温度场数值模拟研究

以本钢连铸中间罐为研究对象,通过建立罐内钢液的流动的数学模型,计算出六流T型中间罐内钢液的流动状况和温度分布情况,其结果表明:在罐内中间流与边流之间钢液流速和温度分布是存在差异的.因此,确定了有利于发挥中间罐冶金功能的控流方案,为连铸稳定生产获得合格坯提供了理论依据.     

Numerical simulation of lithium‐ion battery performance considering electrode microstructure

A spatially resolved three‐dimensional microscale model of a lithium‐ion battery half‐cell is developed and applied to periodic electrode microstructures made up of spherical particles following a bidisperse particle size distribution. The geometries of the periodic unit cells are derived from discrete element simulations using periodic boundary conditions. Three different particle arrangements, which consist of two layered structures and one mixed particle array, as well as three different compression rates, are considered. In the study, the cathode is assumed to consist of LiMn₂O₄ as active material. Layered particle arrangements comprising the particle fraction of the smaller particle size in the region close to the separator are found to be beneficial especially for high‐rate applications. According to the simulation results, the high‐rate capability is reduced upon compression of the electrode microstructures. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrolyte flow optimization and performance metrics analysis of vanadium redox flow battery for large-scale stationary energy storage

Vanadium redox flow battery (VRFB) is the best choice for large-scale stationary energy storage, but its low energy density affects its overall performance and restricts its development. In order to improve the performance of VRFB, a new type of spiral flow field is proposed, and a multi-physics coupling model and performance metrics evaluation system are established to explore the electrolyte distribution characteristics. The results show that the new spiral flow field can effectively improve the uniformity of electrolyte flow and alleviate the phenomenon of local concentration polarization as compared with the traditional serpentine flow field and parallel flow field. Due to the long flow channel and large pressure drop, the system efficiency is low. However, coulombic efficiency, voltage efficiency and energy efficiency are significantly better than the traditional flow fields. Therefore, the novel flow field has obvious advantages in the application of small stacks.     

基于R1233zd的泵驱两相流锂电池散热系统研究

随着人们环保意识的提升,车用锂电池得以飞速发展,水冷系统以其简单的系统结构被广泛应用于车用锂电池散热领域。水冷系统利用工质显热换热,不仅换热能力有限,也存在因工质泄露而引发短路、燃烧的安全隐患。泵驱两相流系统散热能力较强且安全,近年来多应用于航空航天领域,但是在车用锂电池散热方面的应用和研究较少,因此本文提出基于R1233zd的泵驱两相流系统替代水冷系统的锂电池散热方案。R1233zd具有无毒、不可燃且绝缘的特性,同时兼具环保性和较高的散热潜力,相比于传统制冷剂R134a,R1233zd具有更低的GWP和更高的潜热。本研究使用实验的方法,在使用相同实验台架且保持环境温度和冷源温度相同的情况下,对比分析热负荷为500W、700W、900W和1100W时,水冷系统和泵驱两相流系统的散热效果。结果表明：1）在相同散热量的情况下,泵驱两相流系统需要更低的流量,本实验中,泵驱两相流系统的流量仅为水冷系统流量的1/7;2）泵驱动两相流系统具有更好的散热效果,本实验中,其冷板温度比水冷系统低2℃到6℃、冷板下表面温差为水冷系统的1/7;3）泵驱两相流系统能够更好地抑制局部热点的蔓延。综上所述,基于R1233zd的泵驱两相流锂电池散热系统具有非常广阔的应用前景。     

同轴径向热管换热器壳程流场数值模拟

基于多孔介质模型和分布阻力方法,引入Al-sanea和Taborek两种阻力关系式模拟同轴径向热管换热器壳程的流场。结果表明:换热器壳程静压沿烟气流动方向呈线性分布;随入口烟气速度的增加,换热器阻力损失增大、压降增大;且随入口烟气速度的增加,压降增加的速率增大。     

真空管热水器倾角的数值模拟分析

利用fluent软件中的太阳载荷模型对真空管家用太阳热水器进行了三维数值模拟计算,分析了30°、45°、60°倾角下真空管热水器内的流场和温度场随加热时间的变化及传热和流动过程。结果表明,真空管热水器在加热期间,在真空管管口的上壁面出现温度最大值,水箱内真空管管口以下水的温度相对于管口以上的温度分层很明显,水箱内真空管管口以上的热水温度几乎相同,说明水箱内管口以上的水进行了充分混合;对于30°和45°倾角的系统,随着加热时间的增加,水箱内管口以下的水温与管口以上的水温从10 K增加到30 K,以45°倾角为例,当考虑了水箱内管口以下的冷水区时,随着加热时间的增加,真空管与水箱内的温差从0.73 K增大到1.13 K,仅考虑水箱内均匀分布的三点时,随着加热时间的增加,真空管与水箱内的温差从0.15 K减小到了0.03 K;随着系统倾角从30°增加到60°,水箱内管口以下的冷水区域在逐渐减小。因此,为了减小水箱底部的冷水区,插入水箱内的真空管应尽可能短。     

330MW对冲燃烧锅炉燃烧和污染物排放的数值模拟

分别对330MW对冲锅炉在额定负荷、55％额定负荷工况下的流场、温度场、煤粉颗粒场和NOx场进行了模拟研究,模拟结果与实际运行经验吻合较好。通过研究得出了一些有参考价值的数据,对大型对冲燃烧锅炉的设计优化和安全运行具有较为重要的参考价值。     

Application analysis and prospect of electrochemical energy storage in power grid

为促进能源产业的优化升级,可再生能源的开发利用力度不断加大,电网的规划运行和调度管理将面临重大变革,亟需先进的大规模储能技术来改善可再生能源发电特性。本文从电化学储能技术在电网系统应用进行探讨,从各种电化学储能安全性、成本、技术特点等进行深入解析,归纳各种类型电化学储能的优势与不足,并对未来电化学储能在电网系统的应用前景做出展望。