【作者】 赵平辉；

【导师】 陈义良；

【作者基本信息】 中国科学技术大学 ， 工程热物理， 2007， 博士

【摘要】 多孔介质内燃烧技术具有燃烧效率高、污染物排放低的优点，已经成为国内外研究的一个热点。本文采用数值模拟和实验的方法，对多孔介质内预混燃烧过程的机理进行了分析研究。数值模拟是本文的重点，主要包括三部分内容：一维多孔介质内预混燃烧的模拟、考虑湍流的多孔介质内预混燃烧的模拟和二维多孔介质内预混燃烧的模拟。采用一维稳态层流反应流模型对多孔介质内的预混燃烧进行数值模拟是本文最主要的内容。模型考虑气固之间的对流换热和气相的弥散效应，采用详细的化学反应机理和双通量辐射传递方程。由于一维稳态层流火焰面的求解是一个特征值问题，文中还对该问题的数值求解方法进行了研究，通过对初值、迭代方法和网格等的优化，数值计算的稳定性和收敛性大大增强。本文首先分析不同化学反应机理和弥散效应模型对计算结果的影响。研究表明，在当量比较小时，一步反应机理与详细机理的计算结果基本一致；在当量比较大时，使用一步反应机理会产生较大的误差，需要使用详细的反应机理，其中GRI 3.0精度最高，GRI 2.11和GRI 1.2次之，Peters最差；在当量比较大时，弥散效应对多孔介质内燃烧影响很大，考虑弥散效应可以大大改善计算的结果。本文还对单层和双层多孔介质燃烧器内的火焰结构、火焰传播及驻定机理、污染物排放、辐射输出效率等问题进行研究。结果表明，相比于自由流中的预混燃烧，多孔介质内燃烧可以实现超绝热火焰温度、拓宽贫燃极限、提高层流火焰传播速度、减少污染物的排放；单层多孔介质燃烧器不利于火焰驻定在多孔介质内，双层多孔介质燃烧器易于把火焰驻定在交界面附近，可以防止回火和吹脱。当气流速度较大时，层流模型的计算值与实验值有较大的差距，需要考虑湍流的影响。本文推导了多孔介质内燃烧的一维湍流模型，并进行了数值计算。结果表明，用湍流模型计算的火焰传播速度、NO和CO的排放量比层流模型更接近实验值，说明考虑湍流效应可以改善数值计算的结果。但是NO的计算值与实验值仍有较大差别，需要考虑更精确的模型。为了考虑由壁面粘性和散热引起的火焰面结构的多维效应，并对前面模拟中的一维假设进行检验，使用二维层流反应流模型对多孔介质内的预混燃烧进行模拟。结果表明，多孔介质内的边界层很薄，且厚度一定，流动和燃烧可以近似为一维情形，多孔介质内主流区的火焰结构与使用一维模型的计算结果相似。通过实验对多孔介质内的预混燃烧火焰进行观察和测量。实验使用丙烷／空气预混气，多孔介质材料选为氧化铝泡沫陶瓷。实验得到的结论验证了前面的计算结果。更多还原

【Abstract】 The study of the combustion in porous media has become an international hotspot because combustion in porous media has the virtues of the high combustion efficiency and the low emissions. The premixed combustion in porous media was studied experimentally and numerically in this paper. The numerical simulation, the main task of the paper, includes three parts: one-dimensional laminar premixed combustion modeling, one-dimensional turbulent combustion modeling and two-dimensional combustion modeling.The numerical simulation of the combustion in porous media using one-dimension steady laminar reacting model was intensively studied with the interphase convective heat change and dispersion effects, the detailed mechanism and two-flux radiative transfer equation. The numerical method was also carefully studied to solve the steady premixed flame propagation with eigenvalue. The stability and convergence are strengthened by optimizing the initial value, the iterative method and the numerical gird.The influence of different chemistry reaction mechanisms and dispersion effects was numerically analyzed firstly. The results show that one-step mechanism has the same result with the detailed mechanism with small equivalence ratio, and the detailed mechanism should be included with large equivalence ratio. Four detailed mechanisms, GRI 3.0, GRI 2.11, GRI 1.2 and Peters, were studied. The results show that GRI 3.0 mechanism is the best, and Peters mechanism is the worst. The influence of the dispersion effects is large with relatively large equivalence ratio, and the computational result can be greatly improved if the dispersion effects are considered.The flame structure, the flame propagation and stability, the emissions and the radiative output efficiency in a one-layer and a two-layer porous porous burner were also studied. The combustion in a porous burner has more special characteristics such as superadiabatic flames, broader lean flammabilities, higher flame propagation speed, et al. compared to the combustion in a free space burner. The flame is easily stabilized between the two layers in a two-layer porous burner to overcome the shortcomings of the flashback and blow up in a one-layer porous burner. The turbulent model should be taken into account since the laminar method was not suitable for higher gas velocity in burner. The one-dimensional turbulent model was developed and numerically studied in porous burner. The flame propagation speed and the emissions of NO and CO with the turbulent model are better than that with laminar method. It should be noted that a more accurate model is needed to have better predicted NO emission.The two-dimensional combustion simulation in porous burner was performed to take into account the effects of the viscosity and the heat loss from the wall, which was also used to validate the assumptions in the one-dimensional model. The flow and flame is approximately one-dimensional in porous media due to the very thin boundary layer in 2-D simulation.The C₃H₈/Air premixed flames in the AL₂O₃ porous ceramic foam were observed and measured. The conclusions by computation are well agreed to that by experiment.更多还原