本研究分別以數值模擬與實驗方法，針對預混焰在毫米尺度微管槽內加速傳遞及緩燃焰轉爆震焰機制進行探討。透過包含多步化學動力反應模型之三維暫態反應流模擬，解析火焰加速傳遞過程；並配合高速攝影、紋影顯影及碳膜顯影，分別對於火焰傳遞、火焰結構及震波結構進行實驗研究。研究中以數值模擬探討熱邊界、管槽尺度、截面形狀、當量比及點火方式對火焰加速之影響。在絕熱壁面、較小尺度、圓形截面、化學當量下燃氣比例及環狀點火條件下，火焰較快由緩燃焰進入爆震焰。各模擬案例皆不解析紊流方程，故紊流並非緩燃焰轉爆震焰產生之必要條件。於緩燃焰階段，因高溫已燃氣體膨脹對火焰面前未燃氣體進行預壓縮。微管邊界層效應使氣流阻滯，造成燃燒壓力的提升並使單位時間燃氣消耗量增加。此效應與燃氣膨脹形成正向循環，加速火焰最終產生局部爆炸，轉變成爆震焰。在實驗觀察部分，則分別使用氮氣、氬氣、氦氣及二氧化碳做為稀釋氣體，探討氣體稀釋對於火焰傳遞動態之影響。結果顯示稀釋比例提高，除了火焰亮度降低外，爆震焰產生前會有不穩定震盪現象的產生。火焰及震波結構顯影顯示，氫/氧焰傳遞初期有鬱金香焰產生。在以10 %氮氣稀釋之化學當量乙烯/氧氣所進行之碳膜實驗中歸納得知，爆震焰產生初期細胞長度(cell length)約為0.75 mm；於穩定爆震焰傳遞區間，細胞長度則約為1.75 mm。

The objectives of the present research were to study the mechanisms of flame acceleration and deflagration-to-detonation transition (DDT) in microscale tubes and channels. Both 3D transient reacting flow simulations with detailed chemical mechanisms and experimental approaches were applied. High speed cinematography, schlieren visualization, and soot film method are utilized to reveal the flame evolution, flame structure, and detonation cell structure, respectively.
In the numerical study, the effects of wall thermal boundary condition, tube diameter, shape of the channel cross-section, equivalence ratio, and ignition configuration on the flame propagation were investigated. Adiabatic wall, smaller diameter, circular cross-section, stoichiometric mixture, and ring-shaped ignition configuration were found to be able to faciliate DDT. Since turbulence was not modeled in the simulation, the results implied that the existence of turbulence was not essential for DDT to occur. The mechanism of DDT in microscale tubes relied on the choking effect. The wall constraint and expansion of the burned gas resulted in a pre-compression to the upstream unburned gas, which enhanced mass burning rate. The compression was further enhanced by the increased amount of burned gas. A local explosion eventually occurred due to the excessive compression, and deflagration-to-detonation transition was triggered.
In the experiments, stoichiometric ethylene/oxygen mixtures were diluted with nitrogen, argon, helium, and carbon dioxide to study to the effect of dilution on flame propagation in microscale channels. The results showed that flame emission intensities decreased. Asymmetrical flame propagation was observed for high dilution ratio. Tulip flame was observed using schlieren method during the early stage of hydrogen/oxygen flame propagation. For stoichiometric ethylene/oxygen mixture diluted with 10 % nitrogen, soot film visualization revealed that detonation cells were about 0.75 mm in the early stage of detonation, and developed to approximately 1.75 mm in stable detonation wave propagation regime.

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