指導教授：馬小康臺灣大學：機械工程學研究所王明勇Wang, Ming-YungMing-YungWang2014-11-292018-06-282014-11-292018-06-282014http://ntur.lib.ntu.edu.tw//handle/246246/263305基於石化燃料在世界上蘊藏量有限，為此世界各國都在研究開發替代能源。其中包含風能、太陽能、氫能、洋流潮汐能，以及本文所要探討的生質燃料能。由於前述幾種能量均需要特殊的設備與大量的資金，唯獨固定床式固態生質燃料氣化爐是簡易及方便組裝。可應用在以農業廢棄物為主之生質燃料的農村地區。本文利用火場動態模擬器(Fire Dynamics Simulator, FDS) 程式模擬氣化爐內生質燃料之氣化過程，並以此設計一具改良之下引式氣化爐。為提昇整體系統的能源利用，故另外設計排氣通道計算其表面各處溫度以評估貼上熱電片模組(Thermoelectric generator，TEG)後的廢熱回收效能。改良之下引式氣化爐在當量比(ER)為0.3時氣化爐有最佳操作狀況，而空氣滲入氣化爐內的量應少於排氣流量的5%。此時熱值可達5.71MJ/m3 且氫氣產生濃度為26.53 vol%。當初始水份含量為11.18%時所測到的產氣效率(cold gas efficiency, CGE)為66.85%，此值亦落在65.07%到70.44%的計算範圍內。另生質燃料之初始水分含量介於10%至20%之間時氣化效果較佳。實驗量測單片熱電模組最佳效率是在144℃溫差、負荷在1Ω 和 5Ω下最大電壓可達1.33V 和 1.83V，單位面積電功率為857W/m2。綜觀整個實驗與計算的結果，FDS程式可有效的模擬和分析氣化爐內的氣化性能，並據此改善與增進氣化爐的氣化效率。Based on fossil fuels in the world have limited, and usage keeps increase in the present there are quick to shorten its serviceable life. For this tendency, all countries are research and development in alternative energy sources, which includes wind energy, solar energy, hydrogen energy, ocean currents, tides, and the biofuels of this article discussion. Due to the front mention different kinds of alternative energy development would require special equipment and need to spend a great deal of money, but solid biomass fuels fixed-bed gasifier would easy to assemble and construct. It can be promoted the application of biomass fuel of agriculture wastes in local rural area. Computational Fluid Dynamic (CFD) modeling applications of the biomass gasification process help to optimize the gasifier. This study aims to investigate the impact of several physical parameters on the behavior of gasification in a fixed-bed downdraft gasifier. To that end, the study presents a comparison of the results computed using the Fire Dynamics Simulator (FDS) model with the experimental results of biomass gasification. Therefore, different sets of simulations and experiments have been performed to examine the effects of initial moisture content, equivalence ratio, high heating value (HHV), and cold gas efficiency (CGE). At the optimum operation, the equivalence rate is 0.3, the HHV can reach 5.71 MJ/m3, and the produced hydrogen concentration is 26.53 vol%. For an initial moisture content of 11.18%, the measured CGE is 66.85%, which is within the range of 65.07% to 70.44%. In general, the initial moisture content of the rice husks is suggested in between 10% to 20%. Meanwhile FDS is also application on biomass gasifier venting duct temperature distribution for investigated searching the best position of the modules to enhance the system thermal efficiency. The electrical characteristic of TEG modules at temperature difference 140℃, the maximum voltage can reach 1.33V and 1.83V at 1Ω and 5Ω respectively, however the output power attain 1.37W is higher than cooling pump power waste 0.45W, and the TEG power per unit area can reach 857W/m2. The overall results indicate that the FDS model can effectively simulate and analyze gasification performance inside the gasifier, and the performance of an improved downdraft gasifier system (IDGS) is improved by higher cold gas efficiency.口試委員會審定書 i 誌 謝 ii 中文摘要 iii 英文摘要 iv 目 錄 vi 圖目錄 ix 表目錄 xii 符號彙編 xiii 第一章 緒論 1 1.1 研究背景及動機 1 1.2 文獻回顧 4 1.2.1 氣化歷史介紹 4 1.2.2 氣化工作原理 5 1.2.3 氣化爐應用 9 1.2.4 氣化爐數值模擬 11 1.2.5 熱電效應 12 1.3 研究目的 13 第二章 FDS理論基礎 16 2.1 基本假設 16 2.2 FDS理論模式 16 2.2.1 固體熱傳導模式 17 2.2.2 燃燒模式 – Mixture Fraction Combustion Model 19 2.2.3 熱輻射模式 22 2.2.4固體表面熱對流熱傳 23 2.2.5固體表面的邊界條件 24 2.2.6 紊流模式 - Large Eddy Simulation (LES) 24 2.2.7 質量守恆方程式 25 2.2.8 動量守恆方程式 25 2.2.9 能量守恆方程式 26 2.2.10 理想氣體狀態方程式 27 2.3 數值方法 29 2.3.1 質量方程式的數值處理 30 2.3.2 動量方程式的數值處理 31 第三章 實驗設備與模擬過程 36 3.1 實驗與模擬之流程 36 3.2 模擬既有之氣化爐方法 39 3.3 改良之氣化爐實驗與模擬方法 43 3.2.1 實驗設備 43 3.2.2 實驗程序 49 3.2.3 模擬過程 50 3.2.4 參數定義 52 3.4 熱電晶片效應評估 53 3.3.1 實驗設備 54 3.3.2 實驗程序 56 3.3.3 模擬過程 56 第四章 結果與討論 58 4.1 模擬既有之氣化爐 58 4.1.1 格點獨立性測試 58 4.1.2 出口抽氣速度的影響 59 4.1.3 空氣滲入量的比較 64 4.1.4 台灣本土農業廢棄物氣化後的比較 69 4.1.5 生質燃料水份含量的影響 73 4.2 改良之氣化爐實驗與模擬 77 4.2.1 FDS程式模擬結果的顯示 77 4.2.2 不同之當量比下空氣進氣量與空燃比之比較 80 4.2.3 不同之當量比下產氣率之比較 81 4.2.4 氣化爐內溫度之比較 82 4.3 熱電晶片效應評估 83 第五章 結論與建議 89 參考文獻 91 簡歷 993194963 bytesapplication/pdf論文公開時間：2014/08/04論文使用權限：同意有償授權(權利金給回饋學校)氣化下引式氣化爐生質燃料火場動態模擬器熱電模組thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/263305/1/ntu-103-D94522038-1.pdf