本論文應用雷射吸收光譜偵測氫氧自由基（OH Radical）濃度的變化，以進行甲烷與丙烷在等當量比時的點火延遲現象觀察。實驗方法是利用震波管瞬時壓縮加熱CH4/O2/Ar與C3H8/O2/Ar二種混合氣，使其燃燒產生OH自由基，並觀察環狀染料雷射（Ring-Dye Laser）所產生之單頻紫外光（310.213 nm）被OH自由基吸收的情形，並以此定義本實驗點火延遲時間。希望藉由丙烷點火延遲觀察，更能瞭解丙烷燃燒現象與反應動力特性。

本實驗中燃氣（甲烷、丙烷）與氧氣在等當量比混合後，經氬氣稀釋為實驗氣體，混合濃度為0.45%、0.225%、0.15%，實驗溫度1450 K~2150K，壓力為1及3大氣壓。實驗結果顯示在同溫同壓下，丙烷點火延遲時間遠較甲烷為短，期間差異約略在一個級數（Order）。就丙烷而言，點火延遲時間隨溫度、濃度、壓力增加而縮短，在高溫（1600K以上）高壓情況下尤其顯著。實驗結果與文獻經驗式預測值相差甚大；分析顯示經驗式未考慮點火延遲時間之壓力影響，顯示文獻經驗式仍需進一步修正；實驗結果分析亦顯示點火反應機構隨壓力變化而改變。

從反應動力初步分析，推測在高溫高壓環境下，丙烷點火由於氫原子的直接釋出而由C3H8 + M iC3H7 + M C3H6 + M 反應途徑之反應速率所控制。隨溫度壓力降低，C3H8 + M CH3 + C2H5 + M 及C3H8 + M nC3H7 + M CH3 + C2H6 + M 等反應途徑釋出之C/H活性基所誘發之鏈分岐，亦漸影響丙烷之點火延遲現象。

The ignition delay of CH4/O2 and C3H8/O2 stoichiometric mixtures diluted in argon have been studied in shock tube by laser absorption spectroscopy of OH radical at temperatures 1450K~2150K and pressures 1~3atm. The results showed the ignition delay time of propane mixtures were an order of magnitude shorter than that of methane mixtures at the same temperature and pressure. For propane ignition delay observation, the delay time was shortened as the concentration and the pressure increased. The analysis also showed the pseudo activation energy for propane ignition increased with pressure, which indicated the key reaction path for propane ignition changes when pressure was changed. One possible interpretation of pressure effect is that the dissociation of propane follows C3H8 + M iC3H7 + M C3H6 + M at higher pressures. At lower pressures, the other propane dissociation paths C3H8 + M CH3 + C2H5 + M and C3H8 + M nC3H7 + M CH3 + C2H6 + M participate the ignition process and resulting a slower ignition. The above presumption requires verification by detailed kinetic modeling with an adequate propane oxidation mechanism.

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