对固体氧化物燃料电池阳极中氢气和蒸汽的逆向气体传输进行了数值研究,以阐明气体的局部行为和孔隙结构对气体传输的影响。模拟氢气和蒸汽等摩尔逆向传输的三维分析表明,扩散在细孔中占主导地位,而在较大孔隙中则以对流为主。还阐明了在等摩尔气体传输时,氢气主要在细孔中传输,而蒸汽主要在较大孔隙中传输。随着气体浓度梯度的降低,大孔中的氢气传输显著降低,这表明在较低气体浓度梯度下扩散特性的重要性。另一方面,气体浓度梯度的变化对蒸汽传输和孔径之间的相关性影响不大。此外,孔隙结构尺度越大,对气体浓度梯度的依赖性就越明显。
研究亮点包括:
通过 3D 数值分析研究了氢气和蒸汽的逆向传输。
扩散在细孔中占主导地位,而对流在较大孔中占主导地位。
氢气流过细孔,而蒸汽流过较大孔。
讨论了气体浓度梯度和温度的影响。
较大孔隙中的氢气流动方向与整体流动方向相反。
Fig. 1. Schematic image of calculation domain for counter gas transport analysis.
Fig. 2. Pressure-gradient dependence of (a) molar fluxes of hydrogen and steam and (b) molar flux ratio of hydrogen to steam in hydrogen-steam binary system at 800 °C.
Fig. 3. Dependence of molar flux (left) and molar flux ratio (right) on local pore size in REF, PF4, and PF8 under the condition at (a) ΔPt=0 and (b) ΔPt=ΔPequi at 800 °C. Pressure gradient formed at the equimolar gas transport ΔPequi/wx of REF, PF4, and PF8 are 497, 331, and 200 MPa m−1, respectively.
Fig. 4. Dependence of molar fluxes (left) and molar flux ratio (right) derived from (a) diffusional gas transport and (b) convective gas transport on local pore size in REF, PF4, and PF8 under the condition at the equimolar gas transport at 800 °C. Pressure gradient formed at the equimolar gas transport of REF, PF4, and PF8 are 497, 331, and 200 MPa m−1, respectively.
Fig. 5. Dependence of (a) molar flux of steam, (b) molar flux of hydrogen, and (c) pressure gradient at equimolar gas transport on mole fraction difference between boundaries 1 and 2.
Fig. 6. Dependence of normalized molar flux on the local pore size in (a) REF, (b) PF4, and (c) PF8 at the equimolar gas transport under the condition that mole fraction difference ΔXi was varied at 800 °C. Global mean molar fluxes of REF, PF4, and PF8 are |N‾equi,REF|= 0.60, 0.45, 0.32, 0.20, 0.096, |N‾equi,PF4|= 5.5, 4.2, 3.0, 1.9, 0.94, and |N‾equi,PF8|= 10.9, 8.4, 6.1, 4.0, 1.9 (unit: mol m−2 s−1).
Fig. 7. Dependence of (a) molar flux of steam, (b) molar flux of hydrogen, and (c) pressure gradient at equimolar gas transport on temperature.
Fig. 8. Dependence of normalized molar flux on the local pore size in (a) REF, (b) PF4, and (c) PF8 at equimolar gas transport under the conditions that mole fraction difference between boundaries 1 and 2 was set to 1.0 at various temperature. Global mean molar fluxes of REF, PF4, and PF8 are |N‾equi,REF|= 0.60, 0.60, 0.59, 0.57, 0.51, |N‾equi,PF4|= 5.5, 5.4, 5.1, 4.5, 3.7, and |N‾equi,PF8|= 10.9, 10.4, 9.4, 8.1, 6.3 (unit: mol m−2 s−1).
Kohei Yamazaki, Masashi Kishimoto, Hiroshi Iwai,
Three-dimensional numerical simulation of counter gas transport in porous anodes of solid oxide fuel cells,
Journal of Power Sources,
Volume 627,
2025,
235766,
ISSN 0378-7753,
https://doi.org/10.1016/j.jpowsour.2024.235766.
(https://www.sciencedirect.com/science/article/pii/S037877532401718X)