基于动态内热源特性的车用锂离子动力电池温度场仿真及试验

针对电动汽车动力电池在充放电工作过程中由于热量聚集而导致的温度场非均匀性问题,采用数值仿真与试验相结合的方法,基于电池内阻温升特性,考虑耦合正负极耳的热影响,建立生热速率的时变内热源模型,获得更加精确的电池温度场分布及其动态变化规律,并深入进行温度一致性分析。以某车用锂离子动力电池为样本,对电池单体及模块分别进行温升计算和三维温度场分析及相应的测试试验。结果表明:同一充/放电倍率下,放电温升明显大于充电温升,且电池最大温差随着倍率的增大而增大;电池的温升是一个随时间先增大后恒定的非线性变化过程,且随着放电倍率的增大电池温升速率越大;电池模块温度场并非电池单体温度场的简单叠加,且在相同充放电倍率下电池模块的热一致性不如电池单体。     

电化学储能用锂离子动力电池充放电特性试验研究

为了研究储能用锂离子动力电池的充电容量特性和放电热特性,以15 Ah/3.2 V磷酸铁锂软包电池为研究对象,在不同试验工况下对电池单体进行充放电试验,分析了恒流-恒压充电阶段电池充电容量与充电倍率、充电截止电压及充电环境温度之间的关系,以及恒流放电阶段不同倍率、不同温度下电池的温升特性。研究结果为后续电池组的充电一致性和电池组热管理技术开发提供了可靠的数据基础。     

新能源汽车锂动力电池热模型及仿真研究

本文基于一款常用三元锂动力电池建立电池三维热模型,通过数值模拟的仿真研究方法,得出了电池单体温度场仿真结果。结果显示,随着放电倍率提高,电池的温升速率、最高温度和最大温差都有不同程度的增加,以前后表面进行换热时,电池的最高温度最小。     

基于ANSYS的电动汽车动力电池温度场的研究

针对电动汽车动力电池在各种工况下的温升以及电池成组后温度场分布问题,应用有限元软件Ansys,对电池0．3C、1C放电至截止电压时的温升进行热仿真分析;对成组电池0．3C放电至截止电压进行了温度场仿真;对电池单体,分析了在电池上添加散热肋片时电池的温升。结果显示：随着电池放电倍率的上升,电池的温升越高,电池内外的温度不均匀性越大;电池成组后放电时会产生热量聚集现象,使位于中间位置的电池温度进一步上升;散热肋片能使电池最高温度下降2℃左右,但由于电池包中电池间隙太小导致其增加散热效果不明显。     

动力锂电池温度场仿真分析

动力锂电池是纯电动汽车的核心部件,性能受温度影响较大,较高的温度会减少电池的循环使用寿命,甚至造成燃爆事故。针对锂电池在工作过程中的发热问题,根据电化学反应理论与电池生热理论,建立了基于NTGK模型的电化学-热耦合模型并进行仿真分析,得到了不同放电倍率下电池的最大温升和最大温差的变化情况。搭建试验平台对仿真结果进行试验验证,结果表明,试验温度变化曲线与仿真分析结果基本吻合,验证了模型的可行性,且随着放电倍率增大,电池的温升越快,最高温度和最大温差越大。     

锂离子单体电池热特性仿真分析

在电动汽车行驶时,电池组持续发热,电池组内部会集聚大量的热,从而导致电池的工作温度超过正常范围,造成了一定的安全隐患。鉴于此,选取了一种电动汽车常用的锂离子电池组作为研究对象,对其单体锂电池热特性进行了仿真分析,并探讨了其散热性能。结果表明:锂离子电池最佳工作温度为298～313 K,并且单体放电倍率为2C时,就达到了电池温度的工作极限范围,需要进行快速散热处理。     

基于电化学-热耦合模型的锂电池热源分析

锂离子电池在使用过程中的产热情况会影响电池性能。以磷酸铁锂电池为研究对象,建立了三维电化学-热耦合模型,模拟了不同放电倍率下锂离子电池的平均温度及内阻变化情况,分析可逆热与不可逆热对电池产热的影响。随着放电倍率的增大,电池平均温度升高,内阻变大,电池外部与内部温度场呈不均匀化;可逆热与不可逆热是影响电池产热的主要因素。     

[动力电池]基于电-热耦合模型的锂离子电池组热管理系统设计与优化

针对电池组放电过程各部位生热不均匀现象,研究了其生热机理,建立电池电-热耦合模型,得到电池单体电流密度及生热速率在电芯上的分布规律。基于该生热规律模拟电池模组在不同放电倍率下的温升,根据电池模组的热物性参数及冷却要求(电池模组温度控制在25~40℃,温差小于5℃)计算冷却水流速,并设计相对应的水冷结构。对比研究不同放电倍率、不同厚度导热板的电池模组仿真结果,得到最优导热板厚度(0.5 mm)。最后根据仿真结果对水冷系统进行优化,进一步减小了电池模组的温差。     

连接排对电芯成组工艺和性能的影响分析

以某电动汽车电池模组为对象,研究了模组放电倍率、汇流排接触面积和电流I/O位置等设计参数对模组温度场电场的影响。通过对温度场分布的分析,考察了设计参数对电池单体和汇流排的温度变化、温度的均匀性以及二者之间热交换情况的影响。研究表明:电流放电倍率不仅对温升影响较大,还会影响汇流排和电池单体之间的热交换,高倍率电流充放工况下电池发热应该考虑汇流排电热效应的影响。接触面积和电流I/O位置会对电池单体温升、度均衡性以及电流均衡性产生不同程度的影响。     

高功率锂离子电池放电倍率对容量影响的研究

锂离子电池比能量高，循环寿命长，具有高稳定性，已应用于各个领域。研究高功率锂离子电池放电倍率对容量的影响，对不同放电倍率的高功率锂离子电池进行容量测试，明确高功率锂离子电池的容量衰减问题，得到不同倍率下循环使用后高功率锂离子电池的容量和电压曲线。采用混合功率脉冲特性方法对高功率锂离子电池内阻进行测试和计算，分析结果表明，高功率锂离子电池在高荷电状态下内阻伴随放电率的提高而减小，在较低荷电状态下内阻则呈现出一定的复杂趋势。通过研究，可以促进高功率锂离子电池的应用。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.