本文選題：甲烷 + 貧燃　； 參考：《中國科學(xué)技術(shù)大學(xué)》2015年博士論文

【摘要】：甲烷是煤層氣和天然氣的主要成分。高濃度煤層氣和天然氣作為優(yōu)質(zhì)燃料,在鍋爐、燃氣輪機等各種燃燒設(shè)備中得到了廣泛應(yīng)用。甲烷也是很強的溫室氣體,在煤礦開采過程中,為控制井下甲烷濃度,常常通過大量通風(fēng)將甲烷直接排入大氣中。煤礦安全事故,常常是低濃度甲烷的爆炸所引起的,控制甲烷濃度可有效防止礦難的發(fā)生。為了控制燃燒溫度,燃氣輪機常常運行于貧燃狀態(tài)。廢氣處理等場合,存在大量的低濃度甲烷氧化過程。對于貧燃甲烷著火過程的研究,具有重要的理論意義和實用價值。作者建立了一套包含激波管及對應(yīng)的配氣、壓力控制、光學(xué)測量系統(tǒng)的實驗平臺。利用激波與反射激波的壓縮效應(yīng),將甲烷/空氣混合物瞬間加熱至高溫工況,對其著火過程的OH發(fā)射譜進行了測量。在甲烷濃度10%-0.5%,溫度1500K-2000K,壓力約0.9atm的工況范圍內(nèi)以O(shè)H發(fā)射譜峰值為著火標(biāo)志測量了甲烷/空氣混合物的著火延遲。在實驗過程中通過達到縫合條件來延長有效的測量時間。對于激波管內(nèi)的縫合條件運行工況,采用層流模型、k-ω模型、k-ε模型、RSM模型,Spalart-Allmaras模型進行了數(shù)值模擬, k-ω模型以外的模擬結(jié)果都比較符合理想激波關(guān)系�？疾炝瞬煌Ｐ蛯W(wǎng)格的適應(yīng)性,結(jié)果發(fā)現(xiàn),S-A模型對網(wǎng)格的適應(yīng)性最強,其次為RSM模型,k-ε模型的適應(yīng)性比較差。在考慮邊界層網(wǎng)格后發(fā)現(xiàn)：只有對網(wǎng)格適應(yīng)性強的湍流模型,進行邊界層網(wǎng)格局部加密后,得到的計算結(jié)果會比較接近密網(wǎng)格效果。通過數(shù)值模擬及實驗結(jié)果,表明雖然完美的縫合條件很難達到,但是在靠近激波管低壓段端面的實驗測量區(qū)域,可以在甲烷著火的時間尺度內(nèi)保持反射激波形成的溫度壓力工況的穩(wěn)定,足以滿足實驗需要。對甲烷／空氣混合物著火延遲的測量和與GRIMECH 3.0詳細反應(yīng)動力學(xué)機理模擬值的對比表明：低溫時著火延遲會隨甲烷濃度的降低而縮短,但是在1900K以上的高溫工況,各種濃度工況的甲烷著火延遲差距非常小,GRIMECH3.0預(yù)測的著火延遲普遍比實驗測量值短。實驗數(shù)據(jù)顯示本文研究的工況全部為弱點燃工況,甲烷的著火延遲在同一溫度范圍內(nèi)存在一定的變化,用阿累尼烏斯關(guān)系式,即溫度倒數(shù)項與著火延遲對數(shù)項的線性關(guān)系擬合后,實驗測量的著火延遲體現(xiàn)出來的隨甲烷濃度與溫度的變化趨勢與詳細機理模擬值基本一致。由于我們采用OH生成速率達到峰值作為著火標(biāo)志時,反應(yīng)機理模擬難以體現(xiàn)從著火啟動到測量信號達到峰值的過程所需的時間,所以模擬值的計算結(jié)果要比實驗測量值更小。以實驗測量值為基礎(chǔ),在前人研究的基礎(chǔ)上給出了修正表觀活化能和指前因子后的著火延遲經(jīng)驗公式。以GRIMECH 3.0詳細反應(yīng)動力學(xué)機理為基礎(chǔ),計算了各個基元反應(yīng)對關(guān)鍵中間組分的生產(chǎn)與消耗貢獻,并利用敏感性分析的方法研究了甲烷氧化過程中各基元反應(yīng)對整體反應(yīng)速率的貢獻程度。分析表明,貧燃條件下甲烷氧化速率主要取決于CH3的轉(zhuǎn)化,CH3+O2=CH3O+O主導(dǎo)了整體反應(yīng)速率,CH3轉(zhuǎn)化為CH2(s)與兩個CH3復(fù)合為C2H5、C2H6為主反應(yīng)路徑之外的主要CH3轉(zhuǎn)化分支反應(yīng)路徑。H+O2=O+OH為主要的活性氧化劑產(chǎn)生反應(yīng)。在確定主反應(yīng)路徑的前提下,構(gòu)建了包含16種組分,31步反應(yīng)的貧燃甲烷氧化的簡化反應(yīng)動力學(xué)機理。該簡化機理主要適用于當(dāng)量比0.2以下的極端貧燃工況。
[Abstract]:Methane is the main component of coal bed gas and natural gas. High concentration coal bed gas and natural gas are widely used in all kinds of combustion equipment, such as boiler and gas turbine. Methane is also a very strong greenhouse gas. In the process of coal mining, to control the concentration of methane in the underground, methane is often drained directly into the large amount of methane through large amount of ventilation. In gas. Coal mine safety accidents are often caused by the explosion of low concentration methane. Controlling the methane concentration can effectively prevent the occurrence of mine disaster. In order to control the combustion temperature, the gas turbine often runs in the poor combustion state. There are a large number of low concentration methane oxidation processes in the waste gas treatment. The author established a set of experimental platform including shock tube and corresponding gas, pressure control, optical measurement system. Using the compression effect of shock wave and reflected shock wave, the methane / air mixture was heated to the high temperature condition at a moment, and the OH emission spectrum of the ignition process was measured. The methane concentration was 1. 0%-0.5%, temperature 1500K-2000K, the ignition delay of methane / air mixture is measured by the peak of OH emission spectrum in the range of pressure about 0.9atm. In the experimental process, the effective measurement time is extended by suturing conditions. The laminar model, the k- Omega model, the k- epsilon model are used for the suture conditions in the shock tube. The model, the RSM model and the Spalart-Allmaras model are simulated, and the simulation results other than the k- Omega model all conform to the ideal shock relation. The adaptability of the different models to the grid is investigated. The results show that the S-A model has the strongest adaptability to the grid, followed by the RSM model, and the k- e model has a poor adaptability. The results of the numerical simulation and experimental results show that although the perfect suture conditions are difficult to reach, the experimental measurement area near the face of the shock tube low pressure section can be in methane. The stability of the temperature and pressure condition of the reflected shock wave in the time scale of the fire is sufficient to meet the experimental needs. The measurement of the ignition delay of the methane / air mixture and the simulation value of the dynamic mechanism of the GRIMECH 3 reaction show that the ignition delay will be shortened with the decrease of the methane concentration at low temperature, but it is above the 1900K. The gap of methane ignition delay in various concentration conditions is very small. The ignition delay predicted by GRIMECH3.0 is generally shorter than that of the experimental measurement. The experimental data show that the working conditions of this paper are all weak ignition conditions, the ignition delay of methane in the same temperature range is fixed, with the formula of the Arrhenius relationship, that is, the temperature. After the reciprocal term is fitted to the linear relation of the ignition delay logarithm term, the variation trend of the methane concentration and temperature measured by the experimental measured ignition delay is basically the same as the simulation value of the detailed mechanism. Because when we use the OH generation rate to reach the peak value as the ignition symbol, the reaction machine is difficult to reflect from ignition to the measurement letter. The time required for the process to reach the peak value is needed, so the calculation results of the simulated values are smaller than the experimental measurements. Based on the experimental measurements, the empirical formula of the ignition delay after the modification of the apparent activation energy and the pre finger factor is given on the basis of the previous research. Based on the GRIMECH 3 detailed reaction kinetics mechanism, the various bases are calculated. The contribution of the element reaction to the production and consumption of the key intermediate components, and the contribution degree of each element reaction to the overall reaction rate in the process of methane oxidation is studied by the method of sensitivity analysis. The analysis shows that the rate of methane oxidation mainly depends on the transformation of CH3, the CH3+ O2=CH3O+O dominates the overall reaction rate and CH3 is converted to CH under the condition of lean combustion. 2 (s) and two CH3 are combined with C2H5, and the main CH3 conversion path.H+O2=O+OH is the main active oxidant outside the main reaction path of C2H6. Under the premise of determining the main reaction path, the simplified reaction kinetics mechanism containing 16 components and 31 step reaction of Lean Methane oxidation is constructed. The simplified mechanism is mainly applicable. At the extreme lean burn conditions under the equivalent ratio of 0.2.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TQ038.1

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