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姓名 鄭偉隆(Wei-lung Cheng) 查詢紙本館藏 畢業系所 機械工程學系 論文名稱 低氮氧化物燃燒器實驗和數值研究及其應用
(Experimental and numerical studies on a low NOx burner and its applications)相關論文 檔案 [Endnote RIS 格式]
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摘要(中) 本研究利用熱再循環燃燒技術，發展一低氮氧化物燃燒器，並首次搭配CFD-RC 數值分析軟體進行瑞士捲燃燒器數值模型的建立，結合丙烷氣化學反應機制進行燃燒反應模擬。在實驗量測上，沿著瑞士捲進氣流道到燃燒室中心區，再到出口流道，共擺放了9 支R 型和2 支K 型熱電偶，以掌握1.5 圈瑞士捲燃燒器內溫度變化之情形並評估其熱再循環率(HR)，HR 定義為循環熱與燃料化學熱加上循環熱之比。實驗結果顯示，在當量比φ＝0.5，燃氣雷諾數(Re)為60 ~ 880 範圍內，捲式燃燒器內部所有熱電偶之溫度值會隨著Re 增加而增加，且最大溫度量測值均發生於特別設計之燃燒室中心，這表示預混丙烷焰可被穩定地駐留於燃燒室中心。我們進一步分析Re 對HR 之影響，發現HR 會隨著Re 增加而增加，當Re 從60
增加到 880 時，HR 則從11%增加到25%。藉由熱傳導的作用，燃燒器的壁面溫度也會上升，同時單位時間內有更多的預混燃氣在常溫狀態下進入燃燒器，因此壁面與燃氣間的溫度梯度越大，造成對流效應的影響越大，對於預熱未反應燃氣的效果越好，故HR 越大。在生成物排放量測上，當φ＝0.5 時，於Re = 380 ~ 750 範圍內，所量得NOx 之濃度均在10 ppm 以下，而CO 濃度則會隨著Re 增加而有增加的趨勢，判斷原因有二：一為Re 越大，使得CO 生成物滯留在燃燒器內部的時間就越短，無法有充分的時間進行轉化成CO2 的過程，二是在燃燒室維持高溫的情形下，有少部分CO2 會轉為CO(吸熱反應)。數值分析方面，針對在Re= 630 和φ＝0.5條件下，進行2-D 數值模擬，並與實驗結果作比較。有關數值模擬考慮絕熱和非絕熱兩種情況，其結果與實驗結果，雖然在定性上溫度分佈之趨勢是相同的，但在定量方面則仍有不小的差異，顯示2-D 的數值模型無法完全的模擬出實際的燃燒特性。再者，非結構性網格模型的採用和化學反應步驟的過於簡化，也會影響模擬結果之準確性，這些均是未來數值模擬應努力改善的重點。在應用方面，結合1.5 圈捲式燃燒器(約8×８cm2 大小)和多片熱電材料，成功地建構一小型熱電產生器，在串聯兩片熱電材料下(每片尺寸: 3×3 cm2)，可輕易獲得1.6W 的穩定輸出電功率，可使數個小功率馬達或燈泡長時間運轉和發光。摘要(英) This study applies heat-recirculation technology to develop a low NOx burner. A commercial numerical program (CFD-RC) is used as a design tool to model chemical reacting flow using propane/air mixtures in a Swiss-roll burner (SRB). Measurements of the temperature distributions, heat-recirculation rate, and concentrations of exhaust gas in the SRB are carried. We employ 2 K-type and 9 R-type thermocouples to measure temperature distributions of the SRB and estimate the heat-recirculation rate (HR=Qr×100%/(Qi +Qr)),
where Qr is the recirculation heat per unit time and Qi is the chemical heat of the fuel per
unit time. The experimental result shows, φ =0.5 and the Reynolds number (Re) ranging
from 60 to 880, values of the temperature distribution in SRB increase as Re increases. The
maximum temperature occurs in the center of combustor, proving that C3H8 /air premixed
flames can be stabilized in the combustion zone. We analyze the effect of Re on HR, for
which HR increases as Re increases. As Re increases from 60 to 880, the percentage of HR
increases from 11% to 25%. As Re increases, the wall temperature increases and more
reactants with ambient temperature enter into the SRB. Therefore, the temperature gradient
between the mixture and the walls is enhanced with increasing Re. This promotes the
convective heat transfer and thus increasing HR. Measurements of emissions show that NOx
concentrations are less 10 ppm at φ =0.5 for Re = 60~880. On the other hand, the
concentrations of CO increase as Re increases. This is probably because CO has insufficient
time to react to CO2 due to large Re, or the backward reaction step for CO2 to CO occurs
during high temperature in the combustion zone. For numerical simulations, only 2-D
simulations are carried out to compare with experimental result for Re = 630 at φ =0.5. The
comparison shows that the temperature distribution between numerical and experimental
results has similar trend, but there are quantitative differences due to 2-D numerical
simulation, the unstructured grid model, and the overly simplified chemical reaction steps.
Finally, as the goal of the present work, we combine a series of Bismuth Telluride
thermoelectric (TE) materials with the aforementioned SRB to successfully establish a
small TE power generator. The result indicates that only two TE chips, each with 3×3 cm2,
can easily produce more than 1.6 watts for lighting several small bulbs constantly.關鍵字(中) ★ 數值模擬分析
★ NOx 和CO 量測
★ 熱電材料
★ 熱再循環關鍵字(英) ★ heat recirculation
★ thermoelectric materials
★ numerical simulation
★ NOx and CO measurements論文目次 中文摘要………………………………………………………………………I
英文摘要…………………………………………………………………….II
誌謝........................................................III
目錄………………………………………………………………………….IV
圖表目錄……………………………………………………………………VII
符號說明…………………………………………………………………....X
第一章 前言 1
1.1 研究動機 1
1.2 問題所在 2
1.3 解決方案 4
1.4 論文概要 5
第二章 文獻回顧 6
2.1 熱再循環燃燒原理 6
2.2 熱再循環燃燒器之研究 7
2.3 熱再循環燃燒技術之應用 11
2.4 熱電效應原理 12
2.4.1 Seebeck 效應 12
2.4.2 Peltier 效應 13
2.4.3 Thomson 效應 13
2.4.4 熱電材料的物理性質 14
2.5 熱電技術的應用 15
第三章 實驗設備與實驗方法 19
3.1 瑞士捲燃燒器之實驗系統 19
3.2 燃氣供應系統 19
3.2.1實驗氣體與流量控制混合裝置 19
3.2.2預混燃氣操作方式與相關計算 20
3.3 量測儀器系統 21
3.3.1溫度與電壓量測系統 21
3.3.2生成物濃度量測系統 22
3.4 過焓熱電產生器 22
3.4.1 熱電材料 23
3.4.2 熱電產生器之設計 23
3.5 實驗流程 25
第四章 數值方法 34
4.1 數值軟體介紹 34
4.2 數值理論與方法 35
4.2.1 統御方程式 35
4.2.2 計算區域 37
4.2.3 邊界條件 38
4.2.4 數值驗證 39
4.3 氣相化學反應model 40
第五章 結果與討論 46
5.1 超焓燃燒器性能分析 46
5.1.1燃燒器溫度分佈 46
5.1.2熱再循環率的評估 47
5.1.3無因次熱傳參數Q和無因次焓值H之探討 49
5.1.4生成物排放濃度分析 51
5.2 瑞士捲燃燒器數值模擬結果 52
5.3 熱電產生器性能分析 53
5.3.1 輸出電壓的穩定性分析 53
5.3.2 輸出功率分析 54
第六章 結論與未來工作 65
6.1結論 65
6.2未來工作 66
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