【作者】 伊亚超；

【导师】 于欣；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2011， 硕士

【摘要】 目前能源危机中能源利用效率低的现状以及航空动力学中超燃冲压发动机研制所面临的稳定燃烧困难问题,对燃料的燃烧速率和效率提出了更高的要求,针对此问题,本文提出了飞秒激光诱导等离子助燃技术。通过飞秒激光诱导产生的等离子体中存在着大量的激发态组分和自由基,这些活性粒子的存在增加了燃烧链式反应的速率,从而可以提高火焰传播速度,实现助燃的效果。本文首先分析了激光激活气体反应分子助燃的可行性,在CHEMKIN软件中,利用层流预混火焰传播速度计算器模块并结合飞秒激光作用下的甲烷燃烧机理,建立起了飞秒激光激活气体反应分子的助燃模型。通过该模型分析了激光诱导等离子产生的几种活性组分对层流预混火焰的影响。最后通过敏感性分析并结合产物生成速率分析的方法对O和O₂（a¹Δ_g）的助燃机理进行了分析。通过模拟分析发现,预混气体中O、O3的存在都可以在整个当量比的范围内提高火焰传播速度以及H、O、OH组分的浓度,实现助燃的效果。CH₃和CH₂只对当量比小于一定界限的贫燃料火焰才具有助燃作用。激发态组分O₂（a¹Δg）和O₂（b¹Σ_g⁺）的存在都可以明显提高火焰传播速度和H、O、OH的浓度,但是O₂（a¹Δ_g）的助燃效果不如O₂（b¹Σ_g⁺）明显。分析发现,N₂（A³Σ_u⁺）和O₂作用时可以将O₂激发为O₂（a¹Δ_g）、O₂（b¹Σ_g⁺）或者解离为O,实现对层流预混火焰的助燃效果,同时N₂（A³Σ_u⁺）还可以和H2作用将其解离为H,通过提高预混气体中H的浓度而实现助燃。通过对甲烷燃烧机理分析发现,H+O₂（?）O+OH这个反应是层流预混火焰中控制火焰传播速度和H、O、OH组分浓度的最重要的反应。预混气体中O和O₂（a¹Δ_g）的存在增加了火焰传播速度敏感性为正的反应的正向反应速率以及火焰传播速度敏感为负的反应的逆向反应速率,因此使得火焰传播速度得到提高,解释了O和O₂（a¹Δ_g）可以实现助燃的原因。更多还原

【Abstract】 Facing the problem of low efficiency of energy utilization in current energy crisis and the difficulty of stable combustion in the development of scramjet in aerospace dynamics, the combustion rate and efficiency need a higher requirement. According to these problems, this paper proposes a method of using femtosecond laser induced plasma to assist combustion. There exist plenty of free radicals, excited components in the plasma induced by femtosecond laser. And the existence of these active particles increases the rate of chian reactions of combustion and flame propagating, achieving the effect of assisting combustion.The paper first analyzes the feasibility of combustion enhancement by femtosecond activation gas reactive molecules. Then we set up the combustion model using the flame propagation speed calculator module in CHEMKIN combined with methane burning mechanism with the action femtosecond laser. With this model, we analyze the influence of several active compents in plasma to the laminar pre-mixed flame. Using the methods of sentivity analysis and product generation rate analysis, we analyze the mechanism of combustion enhancement by O and O₂（a¹Δ_g） in laminar pre-mixed flame.Through the simulation analysis, we found that O and O3 can improve flame propagation speed and concentrations of H, O, OH compenents through the whole range of equivalence, achiving the effect of combustion enhancement. CH₃ and CH₂ can improve flame propagation speed for poor fuel flame when the equivalent is lower than a certain boundry. Excited components O₂（a¹Δ_g） and O₂（b¹Σ_g⁺） can obviously increase the flame propagation speed and concentrations of H, O, OH compents. The effects of combustion enhancement by O₂（b¹Σ_g⁺） are more apparent than O₂（a¹Δ_g）. We found that when acting with O₂, N₂（A³Σ_u⁺） can realize combustion enhancement by stimulating O₂ to O₂（a¹Δ_g） and O₂（b¹Σ_g⁺） or disintegrate O₂ into O. At the same time, through disintegrating H2 into H, N₂（A³Σ_u⁺） can also realize combustion enhancement by increasing the concentration of H component in laminar pre-mixed flame.Based on the mechanism analysis, we found that the reaction of H+O₂（?）O+OH is the most important one to control flame propagation speed and the concentration of H, O, OH in laminar pre-mixed flame. The existence of O and O₂（a¹Δ_g）in pre-mixed flame increase the forward reaction rate of the reactions with positive sensitivity to flame propagation speed and the reverse reaction rate of the reactions with negative sentivity to flame propagation speed. This phenomenon explains the reason of combustion enhancement by O and O₂（a¹Δ_g）.更多还原