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2.
An analytical model for gas leakage through contact interface in proton exchange membrane fuel cells
《International Journal of Hydrogen Energy》2022,47(75):32273-32286
Sealing performance between two contacting surfaces is of significant importance to stable operation of proton exchange membrane (PEM) fuel cells. In this work, an analytical micro-scale approach is first established to predict the gas leakage in fuel cells. Gas pressure and uneven pressure distribution at the interface are also included in the model. At first, the micro tortuous leakage path at the interface is constructed by introducing contact modelling and fractal porous structure theory. In order to obtain the leakage at the entire surface, contact pressure distribution is predicted based on bonded elastic layer model. The gas leakage through the discontinuous interface can be obtained with consideration of convection and diffusion. Then, experiments are conducted to validate the numerical model, and good agreement is obtained between them. Finally, influences of surface topology, gasket compression and gasket width on leakage are studied based on the model. The results show that gas leakage would be greatly amplified when the asperity standard deviation of surface roughness exceeds 1.0 μm. Gaskets with larger width and smaller thickness are beneficial to sealing performance. The model is helpful to understand the gas leakage behavior at the interface and guide the gasket design of fuel cells. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(83):35423-35436
The gas diffusion substrate (GDS) is essential in the proton exchange membrane fuel cells. Its fabrication techniques affect the performance significantly and are worthy of investigation. In this study, a manufacturing process of the GDS is proposed to understand the formation process of GDS and promote its structure and performance more pertinently. Different states during the preparation process, raw carbon paper, pre-curing, curing, carbonation, and graphitization, are characterized and measured. Experimental and numerical methods are employed to determine the relationships between microstructure, transport, and mechanical performance variation with the fabricating processes. The results show that its porosity, average pore size, and effective diffusivity decrease first and increase after curing. These parameters after graphitization are lower than that of the carbon paper (CP). The electrical resistivity increases dramatically while pre-curing and decreases gradually after curing, carbonation, and graphitization, and it is much reduced after graphitization. Moreover, mechanical measurement results show that both the picks of tensile strength and flexural modulus occur after curing. Its tensile strength shows little change after graphitization compared to the initial paper's. In contrast, the flexural modulus is improved significantly. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(49):21231-21240
To explore the feasibility and related mechanism of MFC biosensor for wastewater detection under the action of combined heavy metals. Cyclic voltammetry (CV) and scanning electrochemical impedance spectroscopy (EIS) were used to explore the related bioelectrochemical process. The response of the reactor to single/combined heavy metals, low/high heavy metal concentrations, and the differences in ohmic resistance (Rs) and charge transfer resistance (Rct) were investigated using Ni as the core heavy metal and the combined action of Cd, Cu and Zn. The results indicated that there was a linear relationship between the concentration and output voltage of the MFC biosensor under the action of combined heavy metals (R2 = 0.8803–0.973). However, the internal resistance (Rint) of the MFC biosensor under the action of single heavy metal was far less than that of the combined heavy metal group, and the power density (19.849 W m?3) was 4 times that of the combined heavy metal group (3.109–4.589 W m?3). The Rs of the biosensors in the combined heavy metal group were 0.868Ω and 0.860, which were higher than 0.768Ω of the single heavy metal sensor. With the increase of the concentration of heavy metals in the influent, the increase of Rct was more obvious in the combined group, while the Rs in the single group significantly increased (P < 0.05). The results imply that it is possible for MFC biosensors to be used in the detection of actual water polluted by various heavy metals, but the biosensor performance is mainly limited by Rct, which needs to be further improved. 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(92):39204-39214
In this work, the SnS2 nanoflowers (SnS2 NFs) were solvothermally prepared in the solvent of ethanol, while SnS2 nanoplates (SnS2 NPs) were obtained through the identical conditions except for the solvent of water. The flowers were assembled with numerous nanosheets with very thin thickness, and the NPs exhibited hexagonal shape. When used as the battery-type electrode material for supercapacitors, the SnS2 NFs delivered a specific capacity of as high as 264.4 C g?1 at 1 A g?1, which was higher than the 201.6 C g?1 of SnS2 NPs. Furthermore, a hybrid supercapacitor (HSC) was assembled with the SnS2 as positive electrode and activated carbon (AC) as negative electrode, respectively. The SnS2 NFs//AC HSC exhibited a high energy density of 28.1 Wh kg?1 at 904.3 W kg?1, which was higher than the 24.2 Wh kg?1 at 844.3 W kg?1 of SnS2 NPs//AC HSC. Especially, when the power density was enhanced to the highest value of 8666.8 W kg?1, the NFs-based device could still hold 20.4 Wh kg?1. In addition, both HSC devices showed an excellent cycling stability after 5000 cycles at 5 A g?1. The present method is simple and can be extended to the preparation of other transition metal sulfides (TMSs)-based electrode materials with brilliant electrochemical performance for supercapacitors. 相似文献
6.
为解决现有瓦斯抽采钻孔封孔工艺的封孔效果较差、导致瓦斯抽放效果不佳的问题,研究提出了新的瓦斯抽采钻孔密封关键工艺,在胡底煤业13091巷进行了瓦斯抽采现场试验。试验结果显示,应用该工艺后瓦斯抽采浓度、瓦斯抽采量均有大幅提高,取得了显著的瓦斯抽采效果和经济社会效益。 相似文献
7.
某石英脉型金矿,原矿金品位为7.62g/t,通过重选+浮选的联合选矿工艺选别后,其尾矿中金品位为0.75g/t,总回收率在90.50%左右。为进一步研究尾矿中金的可回收价值,开展工艺矿物学研究,以查明影响金在选别过程中流失的矿物学因素。通过工艺矿物学自动分析仪(BPMA),扫描电镜(SEM-EDS),XRD等对尾矿开展工艺矿物学检测分析。结果表明:尾矿中的金矿物主要为自然金,偶见银金矿;金矿物主要以与脉石裸露连生的形式存在;其次包裹于脉石矿物中;还有少量为单体;另有少量以次显微金的形式分布于磁黄铁矿为主的硫化物中;金矿物的粒度极其微细,基本都分布于10μm以下,且有近一半分布于5μm以下。损失的金矿物主要以与脉石连生的形式存在,且粒度十分微细,通过再磨-浮选进一步回收的难度较大,裸露金含量超过60%,可采用堆浸对金回收,以提高金的回收率。 相似文献
8.
为提高跨临界CO2空气源热泵热水系统运行性能,对不同压缩机频率、电子膨胀阀开度和水流量下的系统及部件运行特性进行了实验研究,并对循环加热模式下的调节方式进行了优化。结果表明:当阀开度减小时,系统性能系数COP和制热量随过热度的增大而减小;压缩机存在最大电效率点,并且电效率极值点会随着运行频率的增大而向低过热度段发生移动;与电子膨胀阀调节方式相比,水流量调节方案下系统COP提升了13.22%;在循环加热模式下不同加热时期的最优阀开度并不相同,根据最优高压理论对其调节方式进行了优化,最大优化率为15.96%。 相似文献
9.
为了研究不可凝气体(non-condensable gases, NCG)对火电与光热发电机组上广泛使用的大扁管空冷凝汽器性能的影响,以工程机组凝汽器上普遍应用的通流面积220 mm×20 mm的大扁管为研究对象,针对汽轮机典型工况下的实际蒸汽流量,基于Lee相变方程、VOF方法以及组分扩散模型,对蒸汽与NCG混合气体管内两相流凝结换热进行数学建模与数值计算。结果表明:由于大扁管的狭窄通流几何结构与高蒸汽流量,NCG对管内蒸汽凝结的抑制效果要远低于预期;当入口空气质量分数按2%增加时,凝结管凝结换热系数仅下降2%左右,这与NCG导致低流量圆管凝结性能急剧下降的结论不同;空气正常泄漏不会导致空冷凝汽器性能下降而影响发电机组效率。 相似文献
10.
为了提高燃气轮机性能数字孪生体求解过程的鲁棒性,提出了一种基于改进广义牛顿法的燃气轮机性能数字孪生体构建方法。首先,选择广义牛顿法作为性能数字孪生体的求解方法;其次,在广义牛顿迭代法的基础上,调整隐式非线性方程对应曲线切线的斜率,改进广义牛顿法的初值设置方法;最后,构建性能数字孪生体,将改进广义牛顿法嵌入性能数字孪生体。通过PGT25+型燃气轮机实测数据验证提出的方法,结果表明:扩大初值范围后,基于改进广义牛顿法的性能数字孪生体的仿真精度仍与原始方法一致,该方法能够提高性能数字孪生体的鲁棒性,扩大性能数字孪生体的适用范围。 相似文献