层流扩散过滤燃烧火焰特性的研究

Diffusion filtration comubstion widely exists in natural world and engineering application and is an important teachnolgoy for exploiting advanced combusiton system. The flame characteristics of laminar diffusion combustion is investigated based on the macro scale and pore scale model.A relationship between the flame height and parameters is eastablished by experimental measurement and theoretical anlysis,thus the overall flame structure is studied by macro scale.The physic of flame formation in pore and the basic law are explored using pore scale multi-dimensional model.The flame hight expressions are eastablished analytically, tacking into account the gas diffusion and dispersion in porous media and establishing species conservation equation. A simplified analytical solution for flame height is presented by anlogying with the classical laminar diffusion flame theory. The structure of the porous media by the magnetic resonance imaging is re-contructured, the gas flow, heat transfer and combustion process are deeply uncovered and microcosmic mechanism of flame is expored using a pore scale 3-D numerical model. The spheres are randomly poured into the combustor to form a packed bed with a constant height per time, the flue gas and temperature distributions in the burner are dynatically measured and analyzed, the flames are observed and recored from photographs of the upper and the side of the combustor, and then the flame images are constructed. Based on the experimental results, the flame height, flame structure, and its influence factors are investigated by experimental study, the transition mechansim between the immersion and surface flames are clarified.This project is intended to form a relatively comprehensive combustion theory for diffusion filtration combustion, and to provide theory foundation and science data for developing the diffusion filtration combustion teachnology.

扩散过滤燃烧是自然界和工程中广泛存在的一种燃烧现象，是开发先进燃烧系统的一项重要技术。本申请从两个层次，即整个系统的宏尺度和微孔径的介尺度，深入认识层流扩散过滤燃烧火焰特性。通过实验测试和理论分析构建火焰高度与主要参数的理论表达式，从宏观尺度上系统认识火焰的整体形态。基于孔隙尺度的多维数值模拟，探索微孔内火焰形成的内在机制和基本规律。考虑组分扩散和弥散，建立组分守恒方程，并与经典的Jost理论类比，分别解析出火焰高度的理论和定性表达式。使用核磁共振成像重构随机小球填充床骨架结构，建立三维数学模型，揭示微孔内的流动、传热和燃烧，深入探索火焰的微观机理；采用"光影法"和传统测试技术，分次等量注入小球，实时测量温度分布和烟气成分，多方位采集火焰影像，研究火焰高度、结构和影响因素，理清浸没火焰与表面火焰的转化机制，形成较系统的扩散过滤燃烧火焰理论，为扩散过滤燃烧的利用提供理论基础和科学依据。

扩散过滤燃烧是自然界和工程中广泛存在的一种燃烧现象，是开发先进燃烧系统的一项重要技术。本申请从两个层次，即宏尺度和微孔径的介尺度，深入认识层流扩散过滤燃烧火焰特性。通过实验测试和理论分析，构建火焰高度与主要参数的理论表达式，从宏观尺度上系统认识火焰的整体形态。基于孔隙尺度的多维数值模拟，探索微孔内火焰形成的内在机制和基本规律。考虑组分扩散和弥散，建立组分守恒方程，并与经典的Jost理论类比，分别解析出火焰高度的理论和定性表达式。使用核磁共振成像重构随机小球填充床骨架结构，建立三维数学模型，揭示微孔内的流动、传热和燃烧，深入探索火焰的微观机理。.实验结果表明，在多孔介质燃烧器中共存两种火焰，在小球孔隙中的浸没火焰I与多孔介质表面火焰II。在填充床高度为40-160mm的范围内，两个明亮的火焰区域，显示的是扩散过滤燃烧的反应区域和火焰形态。对于火焰I，反应区域的宽度很窄，这是扩散燃烧的特性。但是，通过红外热像仪的温度测量表明，在多孔介质内部具有很宽的温度分布区域，这与经典的扩散燃烧存在很大的差异。当填充床高度增加时，高温区域向下游传播，同时高温区域的宽度增加。通过双温三维数学模型，将燃烧器壁面纳入到计算区域，研究了扩散过滤燃烧特性。结果表明，当填充床高度较小时，存在着实验证实的两种火焰。同时，火焰II的最高温度达到2265K (气流入口速度0.06m/s，小球直径2.5mm，甲烷质量分数0.188)。通过系统的研究，形成了较系统的扩散过滤燃烧火焰理论，为扩散过滤燃烧的利用提供理论基础和科学依据。