点加热稳态导热系数测量方法研究

针对稳态导热系数测量方法测量过程时间较长、测量装置复杂、以及样品制备和加工工艺复杂等现状,提出了一种新型的点加热稳态导热系数测量方法,构建相应的三维稳态传热物理模型,使加热面温升只与热流密度、样品导热系数和测温点位置相关。通过聚焦连续激光加热样品,缩短样品达稳态时长至分钟量级;建立对照光路消除表面发射率和激光稳定性对温度测量的影响;红外热像仪测量加热表面稳态温度分布,结合物理模型实现导热系数测量。采用多种已知导热系数的标准材料和线性法对测量方法进行验证,并应用该方法测量硅藻土导热系数为0.49～0.60 W/(m·K),误差为6.06%。该方法的测量迅速及非接触特性使其可应用于工程实地测量。     

面向碳中和的生物柴油制备及应用研究进展

对制备清洁能源——生物柴油的化学催化酯交换法及其他方法,生产生物柴油的反应器及其后续开发利用等进行总结,并分析目前生物柴油在发展过程中所存在的问题,对其未来发展方向提出一些建议。     

测量方式对太阳电池输出性能测试的影响

通过对二线与四线接法测试单晶硅太阳电池I-V曲线的实验结果对比,分析串联内阻对于太阳电池短路电流、开路电压、填充因子及最大输出功率测量结果的影响。结果发现串联内阻越大,太阳电池的短路电流、填充因子及最大输出功率测量结果越小,但对开路电压基本无影响。且太阳电池接收光强越大即输出电流越大时,串联内阻的影响也越大。二线法因串联内阻较大,相较四线测量方法,在光强分别为1160.69、734.61、470.15和232.14 W/m²时,最大功率降幅分别为64.73%、40.26%、22.98%、11.88%;填充因子降幅分别为64.10%、40.96%、22.22%、12.66%。表明内阻大小影响二线及四线测量结果,四线法测量方式能有效规避串联引线电阻和部分接触电阻,是较理想的测量方式。     

叶片型面CMM测量与误差处理技术

介绍了汽轮机叶片的测量方法,并着重叙述了三坐标测量机(CMM)测量的原理;在对叶片截面进行测量过程中,分析了影响CMM测量精度的误差源,列出了CMM测量中经常出现的问题,并提出了相应的误差处理方法。     

风力机叶片制造误差对功率和推力影响的量化研究

为量化叶片制造误差对风力机功率和推力的影响,以NREL Phase VI S809风力机叶轮为研究对象,基于区间分析法和修正叶素动量理论,建立风力机不确定气动响应模型,量化弦长扭角制造误差对功率和推力影响的相对波动幅度,采用极差分析法进行敏感性分析,获得不确定影响敏感位置。结果表明,叶片扭角误差对性能影响更为显著;当弦长误差和扭角误差为±0.02c和±0.6°时,功率和推力最大相对波动达到3.26%和8.09%;弦长误差影响敏感位置为叶根,而扭角误差敏感位置为叶尖,可在此部位施加质量参数要求以控制性能偏差。     

适应于快速热处理设备的温度测量与控制系统设计

提出了一种适应于快速热处量设备(RTP)的温度测量与控制方法。介绍了快速热处理设备工作原理和主要关键技术;针对温度测量与温度控制两大关键技术,提出了先进的解决方案,即一种增强反射及发射率在线测量与补偿的温度测量方法和基于系统模型多输入多输出(MIMO)温度控制方法;通过实验验证了该温度测量方法和温度控制方法的可行性与先进性,并将该温度测量与温度控制系统应用于我们自主研发的快速热处理设备上,证明该温度测量与控制系统完全能满足设备的各项工艺指标。     

温度对秸秆生物炭理化特性和电化学特性的影响

采用程序升温限氧法,在不同温度下制备小麦秸秆生物炭,探究其表面形态、官能团和理化特性随碳化温度升高的演变规律。在此基础上设计基于生物炭的电极,并对其电化学性能进行测试。结果表明：生物炭内部保留了秸秆纤维素多层的束状结构,呈层状、狭缝型非均匀的孔道。随着碳化温度的升高,其表面形态经历蜂窝状小孔、多层维束结构坍塌、边缘熔融和表面析出结晶盐4个阶段。秸秆生物炭具有优越的电容性能,以WB600 ℃的电化学性能最为突出。当碳化温度≥600 ℃时,在波数1430~1870 cm^-1之间,还出现众多杂乱的弱峰。这是由于随着碳化温度的升高,生物炭中—CH==基团转化为C==O基团,生成具有环状结构的得电子基团——醌类。     

基于ERA-Interim再分析数据的南海波浪能资源评估

利用欧洲中期天气预报中心近37 a（1979年1月—2015年12月）ERA-interim高分辨率（0.125°×0.125°）波浪再分析数据,计算南海海域的波浪能流密度、有效波高、平均周期、有效波时等波浪能参数,分析南海海域的波浪能资源时空分布特征。研究表明：1）南海波浪能资源呈现明显的季节分布特征,冬季资源最丰富,秋季次之,夏季最贫乏;2）波浪能资源丰富区位于吕宋海峡—中南半岛东南海域一线,呈东北—西南走向,大值区为吕宋海峡附近海域,波浪能流密度高达16 kW/m;3）综合考虑能流密度、有效波时间、与大陆最近港口距离和岛礁面积,建议A（112.33°E,16.81°N）岛屿作为开发利用的首选。     

贯通测量误差预计在矿山测量中的应用

贯通误差点的多少,直接关系到整个矿井工程质量和使用。在矿山测量中就选择合理的贯通测量方案和合适的测量方法进行分析,提出贯通方案测量技术措施,并对误差预计方法用实例加以说明。     

发射率结合辐射光强实时测量高温辐射源2维温度场

提出了一种由光纤光谱仪与黑白CCD相机构成的新型实时在线高温温度场测量系统.该系统用光纤光谱仪和黑白CCD相机同时测得高温辐射源的真实发射率和光强场,然后根据发射率和光强场计算得到高温辐射源的温度场.利用该系统对高温发光物体——卤素灯灯丝的温度场进行测量,得到了不同电压值下卤素灯灯丝的温度场分布图,并将所得温度场的最高温度与相应工况下发射光谱法测量得到的最高温度进行比较.结果表明:两者相对偏差在5%以内;所提出的测量方法既弥补了发射光谱法不能获得场分布的缺陷,又避免了比色法测温中单色波长带宽和发射率瞬时变化带来的误差,是一种有效的温度场测量方法.     

A calculation method for estimating internal resistance of battery online

内阻是蓄电池最重要的特性参数之一,也是评价蓄电池性能的重要指标。针对现有测量蓄电池内阻方法无法在线测量、需要专用设备测量的不足,提出了一种在线测量蓄电池内阻的计算方法。依据蓄电池在充放电过程中检测到的电流、电压,根据蓄电池充电、放电过程中电流反向会有过零点这一特性,利用对电流的定积分来抵消计算电池内阻过程中蓄电池内部化学反应引起的电池内阻变化,通过一系列计算来估算出蓄电池内阻。基于MATLAB软件,编写了蓄电池内阻估算算法程序,在Simulink中实现了仿真验证。结果证明该计算方法无需借助辅助设备和测试设备就可实现在线估算蓄电池内阻,具有简单方便、计算精确、易于实现等优点。     

Experimental analysis on the degradation behavior of overdischarged lithium-ion battery combined with the effect of high-temperature environment

A set of experiments are performed in the present work to investigate the degradation behavior of lithium-ion battery during overdischarge cycling, as well as the influence of a high-temperature environment on the degradation. Among, different discharge cut-off voltages (1.0, 0.5, and 0.2 V) are included. During the overdischarge process, batteries experience a stage where a violent electro-thermal behavior is exhibited, involving sharp decreases in the voltage and current, and a fierce increase in the surface temperature; moreover, several parameters such as the discharge capacity, energy density, and internal resistances are all increased after overdischarge. Besides, a poor rate capacity and serious capacity degradation can also be seen during the overdischarge cycling, which is further reflected by the evolution of battery surface temperature, charge/discharge voltage, and internal resistances. What is more, it is found that battery electro-thermal parameters, eg, temperature rise, degradation rate, and internal resistances, increase exponentially as overdischarge deepens. Finally, a high-temperature environment is verified to deteriorate the degradation of overdischarged battery.     

State of health prediction model based on internal resistance

The state of health (SOH) is a crucial indicator of lithium-ion batteries. A battery cycle and calendar life are critical for electric vehicle batteries. Complex interactions occur between the SOH and internal resistance of a battery. In this study, several ternary lithium-ion battery charge discharge experiments were performed to investigate the effects of the ambient temperature, discharge rate, and depth of discharge on a battery's internal resistance. An SOH prediction model was then constructed and used to evaluate the remaining capacity of the electric vehicle battery. The model was verified through various experiments, and a comparison of experimental and model-derived data revealed a favorable agreement. Thus, the model accurately predicted the SOH of a ternary lithium-ion battery.     

Dynamic model of a lead acid battery for use in a domestic fuel cell system

This paper presents a review of existing dynamic electrical battery models and subsequently describes a new mathematical model of a lead acid battery, using a non-linear function for the maximum available energy related to the battery discharge rate. The battery state of charge (SOC) is expressed in a look-up table relative to the battery open circuit voltage (VOC). This look-up table has been developed through low discharge experiments of the battery modelled. Further, both the internal resistance and self-discharge resistance of the battery are subsequently expressed as functions of the open circuit voltage. By using an electrical model with these characteristics and a temperature compensation element to model different rates of charge and discharge, a relatively simple and accurate battery model has been developed.The new model takes into account battery storage capacity, internal resistance, self-discharge resistance, the electric losses and the temperature dependence of a lead acid battery. It is shown in this paper how the necessary parameters for the model were found. The battery modelled was a Hawker Genesis 42 Ah rated gelled lead acid battery.The simulation results of the new model are compared with test data recorded from battery discharge tests, which validate the accuracy of the new model.     

Thermal modeling of a cylindrical LiFePO4/graphite lithium-ion battery

A lumped-parameter thermal model of a cylindrical LiFePO₄/graphite lithium-ion battery is developed. Heat transfer coefficients and heat capacity are determined from simultaneous measurements of the surface temperature and the internal temperature of the battery while applying 2 Hz current pulses of different magnitudes. For internal temperature measurements, a thermocouple is introduced into the battery under inert atmosphere. Heat transfer coefficients (thermal resistances in the model) inside and outside the battery are obtained from thermal steady state temperature measurements, whereas the heat capacity (thermal capacitance in the model) is determined from the transient part. The accuracy of the estimation of internal temperature from surface temperature measurements using the model is validated on current-pulse experiments and a complete charge/discharge of the battery and is within 1.5 °C. Furthermore, the model allows for simulating the internal temperature directly from the measured current and voltage of the battery. The model is simple enough to be implemented in battery management systems for electric vehicles.     

Experimental investigation on the essential cause of the degrading performances for an overcharging ternary battery

Ternary power batteries, as the mainstream power sources of electric vehicles, are liable to inducing thermal runaway (TR) with respect to their sensitivity to abusive conditions. Among various abuse conditions, the overcharge of a battery has been considered as the most common and severe case giving rise to thermal safety accidents. In this study, an overcharged battery and a normal battery, both using ternary/graphite electrodes, were investigated and analyzed synergistically through thermal behaviors and electrochemical characteristics. Initially, a series of electrochemical parameters including charge and discharge voltage plateaus, discharged capacity and time at different discharge rates, and internal resistances were carried out. Then, the heat generation behaviors between normal and overcharged batteries were evaluated. Furtherly, the interconnectedness with the electrochemical capacity degradation and heat generation aggravation of the ternary battery after overcharge was analyzed. Besides, the essential causes of the deterioration of electrochemical properties and severe heat behaviors resulting from overcharge were intensively analyzed via microscopic perspectives. In addition, the electrochemical characteristics fading of abused ternary battery triggered by overcharge were investigated, especially under higher temperature (55°C) and ultralow temperature (−20°C) conditions. Therefore, for an overcharged battery, this research not only elaborates the essential causa of the degraded electrochemical and anabatic thermal performance from a materials and thermal science perspective but also provides a foundation for further promoting the safety properties of commercialized power batteries with ternary chemical systems.     

State-of-health monitoring of lithium-ion batteries in electric vehicles by on-board internal resistance estimation

For reliable and safe operation of lithium-ion batteries in electric or hybrid vehicles, diagnosis of the cell degradation is necessary. This can be achieved by monitoring the increase of the internal resistance of the battery cells over the whole lifetime of the battery. In this paper, a method to identify the internal resistance in a hybrid vehicle is presented. Therefore, a special purpose model deduced from an equivalent circuit is developed. This model contains parameters depending on the degradation of the battery cell. To achieve the required robustness and stable results under these conditions, the method uses specific signal intervals occurring during normal operation of the battery in a hybrid vehicle. This identification signal has a defined timespan and occurs regularly. The identification is done on vehicle measurement data of terminal cell voltage and current collected with a usual vehicle sampling rate. Using the adapted internal resistance value in the model, a degradation index is calculated by compensating other influences, e.g. battery temperature. This task is the main challenge, as the impact of the temperature on the resistance, for example, is one order of magnitude higher than the influence of the degradation for the investigated lithium-ion cell. The developed estimation and monitoring method is validated with measurement data from single cells and shows good results and very low computational effort.     

Testing of the performance and energy-storage applied for retired LiFePO4 batteries

针对某电动公交车退役LiFePO₄动力电池,测试了电池的容量、直流内阻、常温下的储存性能,进而测试电池的倍率充放电性能、高低温特性和循环性能,分析了新旧电池相关参数的差异及变化规律;在此基础上,重组电池模组,测试其循环性能;最后集成了1MW·h梯次利用电池储能系统并参与风电平滑。结果显示,该动力电池容量衰退初始容量75%左右时,直流内阻只有小幅增加,电池常温下的储存性能、倍率性能、高低温性能下降不显著,电池单体和模块的循环性能良好,显示出该退役LiFePO₄电池具有较好的梯次利用价值。     

Simulation and verification of lithium-ion battery temperature changing process

针对软包锂离子电池放电过程中温度变化过程进行研究,依据电池产热基本理论,通过内阻实验及0.5 C放电倍率下的温升实验计算出瞬态生热率曲线,得出电池熵热系数,建立生热速率随放电深度不断变化的瞬态生热模型,基于该模型进行不同放电倍率的温度仿真模拟,并与实验进行对比。结果表明,温度变化模拟结果与实验相吻合,生热率变化模拟结果与实验计算值相符合,模型可以很好地模拟电池在不同放电倍率下的温度变化,对电池温升过程分析及电池热管理过程控制具有指导意义。     

Battery testing by calculated discharge-curve method—Constant resistive load algorithm

Battery testing by calculated discharge-curve method (CDCM) includes battery, battery average cell and each of battery's cell 3D discharge curves. These discharge curves were generated by calculated discharge-curve algorithm (CDCA), using either high- or low-frequency monitored discharge data and are lying in battery/cell rectangular parallelepiped: open-circuit voltage–initial discharge current–time.CDCA defines the ordered six-tuple: time–current–voltage–capacity–energy on load–internal energy losses by which battery and battery's cells dynamic characteristics may be analyzed. Any of the six-tuple variables may be divided into the set of i = 1, …, n steps by constant step across the overall discharge interval and used as the domain of CDC algorithm procedure.CDCM, respectively, introduced average current and average voltage as the ratio of capacity to time and energy to capacity. Battery/cell rectangular parallelepiped: time–average current–average voltage is defined at any step of discharging.In this paper, the linear dependencies of average characteristics on the both power of battery/cell internal resistance and load intensity were presented and algebrically proofed. Battery's cells may be compared to battery average cell and may be classified by any characteristics.Discharge curves of alkaline-manganese MALLORY batteries, 9K62 (50 and 100 Ω), PX24 (100 and 166 Ω), PX21 (150 and 250 Ω) and 7K62 (100, 200 and 500 Ω) [T.R. Crompton, Small Batteries 2 (1982) 52] were used to demonstrate battery and battery average cell standard and CDC method characteristics.The mathematical calculations were conducting on IBM PC using Microsoft Excel software.