固態氧化物燃料電池(SOFC)是一種高溫型燃料電池，其工作溫度高達800至1000℃，因此可將未反應之高溫燃料氣體導入後燃室進行燃燒反應，使化學能轉變為熱能並透過熱交換進行能量回收，除了可提升SOFC系統之運轉穩定性與整體效率之外，更具有永續能源技術之高度發展潛力。
研究目標主要為透過後燃室結構之設計與分析，計算後燃器之表現並提供有效提升性能之參考依據，透過計算流體力學方法進行SOFC系統後燃器之熱流場模擬分析，對於後燃器的開發具有節省成本、高效率之優勢，且部分流場特性如燃燒腔室均溫性、流體速度分布、燃燒室局部高溫等，受限於因燃燒溫度相當高，亦不容易透過實驗儀器來量測。
本文提出新型後燃室結構設計—橢圓擋板型結構，有效提升了對流熱傳效應與燃燒室均溫性，並降低〖NO〗_x生成量，且具有殘餘氫氣少與壓損低等多項優勢，更利於工業與商用SOFC系統上應用；當燃料入口管徑D_1或氫氮比降低時，有助於燃料與空氣混合，造成火焰較短、局部高溫較高、殘餘氫氣下降、〖NO〗_x生成量較多與壓損較大等結果，但在氫氮比低於20%時，會發生趨勢反轉之現象，而當燃料入口管徑D_1大於75 mm時，局部高溫開始逐漸回升；考慮SOFC系統前段之重組器與SOFC電堆對燃料成分的影響，當電堆燃料利用率較高時，進入後燃室的可燃氣體(H_2與CO)較少，燃料所含熱值較低，降低了整體溫度與〖NO〗_x生成量，於25 kW SOFC系統中，電堆燃料利用率80%相較於70%，出口均溫降低了65 K，而NO生成量減少約38%。

Solid oxide fuel cell (SOFC) is a type of high-temperature fuel cell, and the operating temperature of the SOFC reaches 800-1000°C. Therefore, the unreacted high-temperature fuel gases can be introduced into the burner which converts the chemical energy into thermal energy through the combustion reaction. Then the remaining energy can be recovered through the heat exchanger. As a result, the operation stability and overall efficiency of the SOFC systems increase. Besides, it shows the high development potential of the alternative and sustainable energy technology.
The objective of this thesis is to estimate the performance of the burner and to provide a reference for improving it effectively through the analysis and structure design of combustion chamber. This thesis applies the CFD (Computational Fluid Dynamics) method to simulate and analysis the thermal and fluid flow fields in the afterburner of SOFC systems. This approach has the advantages of cost-saving and high-efficiency for the development of the afterburner. Also, parts of flow characteristics, such as the temperature uniformity, fluid velocity profile, and high local temperature of the burner, are not easy to be measured with experiment instruments due to the limitation of high burning temperature.
This thesis proposes a new structure design of combustion chamber, the elliptical baffled burner, which enhances the effect of convective heat transfer and temperature uniformity effectively and suppresses the formation of 〖NO〗_x as well. Also, it has low residual fuel exhaust and pressure drop. These advantages make it easier to be applied in the industrial and commercial SOFC systems.
As the fuel inlet diameter or H_2/N_2 ratio decrease, it leads to shorter flame, higher local temperature, lower residual fuel exhaust, higher 〖NO〗_x emission, and larger pressure drop due to better mixing of fuel and air. However, the trends will reverse if H_2/N_2 ratio reduces to 20% or less, and the local temperature will start rising as the fuel inlet diameter exceeds 75 mm.
Take into consideration the influence of reformers and SOFC stacks on the fuel composition. When the stack fuel utilization increases, less combustible gas (H_2 and CO) is brought in the burner. Lower caloric value of the fuel causes reduction of the temperature and generation of 〖NO〗_x in the burner. For a 25 kW SOFC system, the stack fuel utilization of 80% reduces the exhaust temperature by 65 K and NO emission by 38% comparing to the stack fuel utilization of 70%.

[1] Market Analysis, 20th International Conference on Advanced Energy Materials and Research, 13-14 August 2018.
[2] A. Choudhury, H. Chandra, A. Arora, “Application of solid oxide fuel cell technology for power generation—A review,” Renewable and Sustainable Energy Reviews, Vol. 20, pp. 430-442, 2013.
[3] T. Somekawa, K. Nakamura, T. Kushi, T. Kume, K. Fujita, H. Yakabe, “Examination of a high-efficiency solid oxide fuel cell system that reuses exhaust gas,” Applied Thermal Engineering, Vol. 114, pp. 1387-1392, 2017.
[4] I. Frenzel, A. Loukou, D. Trimis, “An innovative burner concept for the conversion of anode off-gases from high temperature fuel cell systems,” 11th Conference on Energy for a Clean Environment, 5-8 July 2011.
[5] S. Voss, M. Mendes, J. C. Pereira, D. Trimis, “Comparison of Experimental and Numerical Results of Ultra-Lean H2/CO Combustion within Inert Porous Media,” Proceedings of the European Combustion Meeting, 2009.
[6] T. H. Yen, W. T. Hong, W. P. Huang, Y. C. Tsai, H. Y. Wang, C. N. Huang, C. H. Lee, “Experimental investigation of 1kW solid oxide fuel cell system with a natural gas reformer and an exhaust gas burner,” Journal of Power Sources, Vol. 195, pp. 1454-1462, 2010.
[7] J. Oh, S. Dong, J. Yang, “The effect of fuel composition on the characteristics of a non-premixed synthetic natural gas-air flame,” Fuel Processing Technology, Vol. 126, pp. 66-75, 2014.
[8] W. T. Hong, T. H. Yen, C. N. Huang, H. I. Tan, Y. Chao, “Design and development of major balance of plant components in solid oxide fuel cell system,” International Journal of Energy and Environment, Vol. 4, pp. 73-84, 2013.
[9] P. Pianko-Oprych, Z. Jaworski, “Numerical investigation of a novel burner to combust anode exhaust gases of SOFC stacks,” Polish Journal of Chemical Technology, Vol. 19, pp. 20-26, 2017.
[10] R. Zadghaffari, J. S. Moghaddas, Z. Rahimiahar, “Numerical investigation of a burner configuration to minimize pollutant emissions,” APCBEE Procedia, Vol. 3, pp. 177-181, 2012.
[11] K. Azizi, M. K. Moraveji, H. Hassanzadeh, H. A. Najafabadi, “Consideration of inclined mixers embedded inside a photobioreactor for microalgae cultivation using computational fluid dynamic and particle image velocimetry measurement,” Journal of Cleaner Production, Vol. 195, pp. 753-764, 2018.
[12] J. Q. E, Q. G. Peng, X. L. Liu, W. Zuo, X. H. Zhao, H. L. Liu, “Numerical investigation on hydrogen/air non-premixed combustion in a three-dimensional micro combustor,” Energy Conversion and Management, Vol. 124, pp. 427-438, 2016.
[13] Z. Ren, G. M. Goldin, V. Hiremath, S. B. Pope, “Simulations of a turbulent non-premixed flame using combined dimension reduction and tabulation for combustion chemistry,” Fuel, Vol. 105, pp. 636-644, 2013.
[14] H. Selim, A. K. Gupta, A. Al Shoaibi, “Effect of reaction parameters on the quality of captured sulfur in Claus process,” Applied Energy, Vol. 104, pp. 772-776, 2013.
[15] H. Selim, S. Ibrahim, A. Al Shoaibi, A. K. Gupta, “Investigation of sulfur chemistry with acid gas addition in hydrogen/air flames,” Applied Energy, Vol. 113, pp. 1134-1140, 2014.
[16] H. Selim, A. Al Shoaibi, A. K. Gupta, “Experimental examination of flame chemistry in hydrogen sulfide-based flames,” Applied Energy, Vol. 88, pp. 2601-2611, 2011.
[17] F. Zidouni, E. Krepper, R. Rzehak, S. Rabha, M. Schubert, U. Hampel, “Simulation of gas-liquid flow in a helical static mixer,” Chemical Engineering Science, Vol. 137, pp. 476-486, 2015.
[18] D. Rauline, P. A. Tanguy, J. M. L. Blevec, J. Bousquet, “Numerical Investagation of the Performance of Several Static Mixers,” The Canadian Journal of Chemical Engineering, Vol. 76, pp. 527-535, 1998.
[19] O. Byrde, M. L. Sawley, “Optimization of a Kenics static mixer for non-creeping flow conditions,” Chemical Engineering Journal, Vol. 72, pp. 163-169, 1999.
[20] E. S. Szalai, F. J. Muzzio, “Fundamental Approach to the Design and Optimization of Static Mixers,” AIChE Journal, Vol. 49, pp. 2687-2699, 2003.
[21] H. S. Song, S. P. Han, “A general correlation for pressure drop in a Kenics static mixer,” Chemical Engineering Science, Vol. 60, pp. 5696-5704, 2005.
[22] W. F. C. van Wageningen, D. Kandhai, R. F. Mudde, H. E. A. van den Akker, “Dynamic Flow in a Kenics Static Mixer: An Assessment of Various CFD Methods,” AIChE Journal, Vol. 50, pp. 1684-1696, 2004.
[23] A. Paglianti, “Recent Innovations in Turbulent Mixing with Static Elements,” Recent Patents on Chemical Engineering, Vol. 1, pp. 80-87, 2008.
[24] M. Coroneo, G. Montante, A. Paglianti, “Computational Fluid Dynamics Modeling of Corrugated Static Mixers for Turbulent Applications,” Industrial & Engineering Chemistry Research, Vol. 51, pp. 15986-15996, 2012.
[25] K. Rashid, S. K. Dong, R. A. Khan, S. H. Park, “Optimization of manifold design for 1 kW-class flat-tubular solid oxide fuel cell stack operating on reformed natural gas,” Journal of Power Sources, Vol. 327, pp. 638-652, 2016.
[26] K. Rashid, S. K. Dong, M. T. Mehran, “Numerical investigations to determine the optimal operating conditions for 1 kW-class flat-tubular solid oxide fuel cell stack,” Energy, Vol. 141, pp. 673-691, 2017.
[27] M. Reisert, A. Aphale, P. Singh, “Solid Oxide Electrochemical Systems: Material Degradation Processes and Novel Mitigation Approaches,” Materials, Vol. 11, 2169, 2018.
[28] J. Nielsen, P. Hjalmarsson, M. H. Hansen, P. Blennow, “Effect of low temperature in-situ sintering on the impedance and the performance of intermediate temperature solid oxide fuel cell cathodes,” Journal of Power Sources, Vol. 245, pp. 418-428, 2014.
[29] 李瑛，王林山，燃料電池，冶金工業出版社，北京，2000。
[30] Z. Y. Guo, D. Y. Li, B. X. Wang, “A novel concept for convective heat transfer enhancement,” International Journal of Heat and Mass Transfer, Vol. 41, pp. 2221-2225, 1998.
[31] M. Alliche, S. Chikh, “Study of non-premixed turbulent flame of Hydrogen/air downstream Co-Current injector,” International Journal of Hydrogen Energy, Vol. 43, pp. 3577-3585, 2018.
[32] J. Blazek, Computational Fluid Dynamics: Principles and Applications, Elsevier Science, New York, 2001.
[33] B. E. Launder, D. B. Spalding, Lectures in Mathematical Models of Turbulence, Academic Press, London, England, 1972.
[34] V. Yakhot, S. A. Orszag, “Renormalization Group Analysis of Turbulence. I. Basic Theory,” Journal of Scientific Computing, Vol. 1, pp. 1-51, 1986.
[35] T. H. Shih, W. W. Liou, A. Shabbir, Z. Yang, J. Zhu, “A New k-ε Eddy Viscosity Model for High Reynolds Number Turbulent Flows,” Computers & Fluids, Vol. 24, pp. 227-238, 1995.
[36] W. C. Reynolds, “Fundamentals of Turbulence for Turbulence Modeling and Simulation,” Lecture Notes for Von Karman Institute Agard Report, No. 755, 1987.
[37] Y. B. Zel’dovich, Y. P. Raizer, Physics of shock waves and high-temperature hydrodynamic phenomena, Dover Publications, Mineola, NY, 2002.
[38] Y. R. Sivathanu, G. M. Faeth, “Generalized State Relationships for Scalar Properties in Non-premixed Hydrocarbon/Air Flames,” Combustion and Flame, Vol. 82, pp. 211-230, 1990.
[39] W. P. Jones, J. H. Whitelaw, “Calculation methods for reacting turbulent flows: A review,” Combustion and Flame, Vol. 48, pp. 1-26, 1982.
[40] P. Cheng, “Two-Dimensional Radiating Gas Flow by a Moment Method,” AIAA Journal, Vol. 2, pp. 1662-1664, 1964.
[41] A. Coppalle, P. Vervisch, “The Total Emissivities of High-Temperature Flames,” Combustion and Flame, Vol. 49, pp. 101-108, 1983.
[42] T. F. Smith, Z. F. Shen, J. N. Friedman, “Evaluation of Coefficients for the Weighted Sum of Gray Gases Model,” J. Heat Transfer, Vol. 104, pp. 602-608, 1982.
[43] M. K. Denison, B. W. Webb, “A Spectral Line-Based Weighted-Sum-of-Gray-Gases Model for Arbitrary RTE Solvers,” J. Heat Transfer, Vol. 115, pp. 1002-1012, 1993.
[44] T. J. Barth, D. Jespersen, “The design and application of upwind schemes on unstructured meshes,” Technical Report AIAA-89-0366, AIAA 27th Aerospace Sciences Meeting, Reno, Nevada, 1989.
[45] W. K. Anderson, D. L. Bonhus, “An Implicit Upwind Algorithm for Computing Turbulent Flows on Unstructured Grids,” Computers & Fluids, Vol. 23, pp. 1-21, 1994.
[46] C. M. Rhie, W. L. Chow, “Numerical Study of the Turbulent Flow Past an Airfoil with Trailing Edge Separation,” AIAA Journal, Vol. 21, pp. 1525-1532, 1983.
[47] S. V. Patankar, D. B. Spalding, “A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows,” International Journal of Heat and Mass Transfer, Vol. 15, pp. 1787-1806, 1972.
[48] A. J. Chorin, “Numerical Solution of the Navier-Stokes Equations,” Mathematics of Computation, Vol. 22, pp. 745-762, 1968.
[49] T. H. Lim, R. H. Song, D. R. Shin, J. I. Yang, H. Jung, I. C. Vinke, S. S. Yang, “Operating characteristics of a 5kW class anode-supported planar SOFC stack for a fuel cell/gas turbine hybrid system,” International Journal of Hydrogen Energy, Vol. 33, pp. 1076-1083, 2008.