共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
3.
质子交换膜燃料电池(PEMFC)气体扩散层(GDL)具有各向异性属性,常规数值模拟对GDL采取均匀模型,忽略了各向异性传递过程对PEMFC性能的影响。本文发展了一个三维非等温单相模型,在GDL平面内和GDL厚度方向采用不同的传递系数,模拟了各向异性传递系数对PEMFC整体和局部性能的影响。在本文计算条件下,GDL各向异性和均匀模型模拟得到的电池极化曲线几乎完全相同,但电池电流密度分布和温度分布等局部特性存在很大差异。该结果进一步证明了不能单独用极化曲线来验证电池数学模型的正确性。 相似文献
4.
5.
质子交换膜电解水制氢技术的发展受到成本的约束。通过提高电流密度以提高单位质子交换膜电解池的氢产量可以降低单位应用成本,但高电流密度下电解池内部传质过电势的升高会导致制氢效率的下降。本文从降低质子交换膜电解池在高电流密度下的传质过电势入手,设计了有利于传质的“钛毡–钛网”式叠层扩散层结构,并进行对照实验分析了不同扩散层结构对电解池性能的影响规律。实验证明,钛毡叠加30目钛网的叠层扩散层结构可以使高电流密度(5 A/cm2)下的传质过电势降低至0.25 V(与钛毡或30目钛网作为扩散层相比,传质过电势分别降低了0.24 V与0.55 V),本项工作也为后续扩散层结构的优化提供了思路。 相似文献
6.
7.
8.
9.
10.
11.
12.
分形复合油藏非牛顿幂律流体不稳定渗流的数学模型 总被引:2,自引:0,他引:2
对不稳定渗流的数学模型进行了推导并建立了分形复合油藏不稳定渗流模型.在无限大地层、有界定压、有界封闭三种外边界条件下分别求出了它们在Laplace空间的解析解.对于两区的特殊情况,分析了井底压力动态特征和参数影响,制作了典型曲线.非牛顿幂律流体的幂律指数,分形参数均对典型曲线产生较大的影响,呈现出与牛顿流体和均质油藏明显不同的特征.这对于非均质油藏非牛顿流体的不稳定试井分析和研究非线性渗流特征都是十分重要的. 相似文献
13.
14.
15.
A finite-volume method for the modeling of transient photon propagation in turbid media with an irregularly shaped foreign object is presented. The procedure can account for non-rectangular foreign object. Body-fitted coordinates are used to discretize the spatial domain. Absorbing, anisotropic scattering non-homogenous medium can be modeled. The procedure is validated using existing numerical results for a homogenous medium. The procedure produces physically possible trends for different optical properties of the foreign object. 相似文献
16.
Shen YongMing Wang JinHua Zheng BingHui Zhen Hong Feng Yu Wang ZaiXing Yang Xu 《中国科学:物理学 力学 天文学(英文版)》2011,54(1):127-142
Understanding the dynamics of water renewal in a reservoir is essential when the transport and fate of dissolved substances are evaluated.A three-dimensional hydrodynamic model was implemented to compute average residence time and water age in Dahuofang Reservoir in China.The model was verified for a one-year time period in 2006.A simulation reproduced intra-annual variation of mixing represented by the fall/winter mixing and the spring/summer stratification.The simulated variation of vertical thermal struc... 相似文献
17.
18.
P. J. Severin 《Fiber and Integrated Optics》2013,32(1):23-48
The optical fiber scattering loss coefficient is measured directly in a scattering sphere or deduced indirectly from total loss measurements. The results show agreement for graded-index silica-based fibers, but they seem conflicting for graded-index compound-glass fibers. This is explained from the diffusion-controlled refractive index profile and the ensuing mode-dependent scattering and absorption loss due to the different optical properties of core and cladding glass. Using this model the two-lengths total loss measurement method is discussed. A detailed experiment is described that convincingly illustrates the mode of operation of the scattering sphere as used in daily practice. The wavelength-independent term in the total loss, different for fibers drawn from the same glass, is explained as being scattering partly due to 1-mode mixing of modes with the same β by imperfections that affect high-1-modes predominantly. The total loss of the glasses to be investigated can be measured using low NA excited silicone-clad fibers and safely can be decomposed into scattering and absorption contributions. 相似文献
19.
The c-axis charge transport of the hole doped triangular antiferromagnet is investigated within the tJ model by considering the incoherent interlayer hopping.It is shown that the c-axis charge transport of the hole doped triangular antiferromagnet is essentially determined by the scattering from the in-plane fluctuation.The c-axis conductivity spectrum shows a lov-energy peak and the unusual high-energy broad band,while the c-axis resistivity is characterized by a crossover from the high temperature metallic-like behavior to the Iow temperature insulating-like behavior,which is qualitatively consistent with those of the hole doped square lattice antiferromagnet. 相似文献
20.
The dynamics of polymers in a random smooth flow is investigated in the framework of the Hookean dumbbell model. The analytical expression of the time-dependent probability density function of polymer elongation is derived explicitly for a Gaussian, rapidly changing flow. When polymers are in the coiled state the pdf reaches a stationary state characterized by power-law tails both for small and large arguments compared to the equilibrium length. The characteristic relaxation time is computed as a function of the Weissenberg number. In the stretched state the pdf is unstationary and exhibits multiscaling. umerical simulations for the two-dimensional Navier–Stokes flow confirm the relevance of theoretical results obtained for the -correlated model. 相似文献