Investigation of Microscopic Structures of Turbulent Diffusion Flames and Establishment of Analyzing Methods Taking Account of Elementary Kinetics

本课题的目的是通过激光光学装置对扰动扩散火焰微观结构动态行为的实验观察和对非稳态火焰的直接数值模拟，建立基于定量成像的湍流燃烧模型。（1）采用激光瑞利散射法，利用512 × 512像素的CCD像增强器和Nd：YAG激光器，获得了不同雷诺数下湍流扩散火焰平面内的瞬态温度场。(2)瞬时最高温度随喷嘴出口平均燃油速度的增大而减小。在较低的燃料流速下，火焰内部区域出现温度波动，随着燃料流速的增加，火焰内外区域的温度波动都增大。(3)在蒸汽应变的H_2/N_2-空气层流对流扩散火焰中， ...更多信息 直接数值模拟和激光瑞利散射二维温度测量结果表明，燃料侧微燃料射流对火焰产生的应变使火焰容易局部淬熄，而空气侧微燃料射流对火焰产生的应变使火焰几乎不淬熄，火焰温度有升高的趋势。(4)考虑到详细的化学动力学和多组分扩散的数值模拟将（3）中描述的现象归因于燃料组分中H_2的稀释或浓缩，这是由于与火焰曲率有关的物种之间的优先扩散。(5)在准稳态火焰中，优先扩散对火焰曲率的影响最为显著，主要是由于火焰熄灭，但随着不稳定性的增加，优先扩散对火焰曲率的影响逐渐减小。(6)在非稳态火焰中，尽管存在极高的拉伸率区域，但火焰在瞬间保持高温，而稳态平面火焰在该区域中不存在。最高火焰温度不能合理的局部拉伸率和变化广泛依赖于非定常效应。少

The purpose of this project is to make the models of turbulent combustion based on quantitative imaging by experimental observation of dynamic behavior of microscopic structures of disturbed diffusion flames by laser optical equipment and direct numerical simulation of unsteady flames. The result obtained through this project are as follows(1) Instantaneous planar temperature profiles in turbulent diffusion flames with various Reynolds number at the exit nozzle were obtained by the laser Rayleigh scattering method using CCD camera with the image intensifier which has 512*512 pixels and the ND : YAG laser.(2) The instantaneous maximum temperature tends to decrease when the average fuel velocity at nozzle exit increases. The temperature fluctuation appears at the inner region of the flame at low fuel velocity and the temperature fluctuation grows both of inner and outer region of the flame with increase of fuel velocity.(3) In H_2/N_2-air laminar counter diffusion flames strained by stea … More dily impinging micro fuel from fuel side, Direct numerical simulation and two-dimensional temperature measurements by laser Rayleigh scattering method show that the flame strained by the micro fuel jet from the fuel side is easily quenched locally, but on the contrary, the flame strained from the air side hardly extinguishes and the flame temperature tends to increase.(4) Numerical simulation taking into account detailed chemical kinetics and multicomponent diffusion attributes the phenomena described at (3) to dilution or concentration of H_2 of the fuel component due to the preferential diffusion-among species in relation to the flame curvature.(5) In quasi-steady flame, the effect of preferential diffusion in relation to flame curvature is outstanding and this is mainly attributed to flame extinction, but as unsteadiness increases, the effect of preferential diffusion in relation to flame curvature becomes small.(6) In unsteady flame, the flame sustain high temperature instantaneously in spite of extremely high stretch rate regime in which the steady flat flames cannot exist. The maximum flame temperature cannot be rationalized by the local stretch rate and changes widely depending on the unsteadiness effect. Less