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设备对扰动扩散火焰微观结构动态行为的实验观察和非定常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)利用具有512*512像素像强器的CCD相机和ND: YAG激光器，采用激光瑞利散射法获得了不同雷诺数湍流扩散火焰在出口喷嘴处的瞬时平面温度分布。(2)瞬时最高温度随喷管出口平均燃油速度的增加而降低。低燃料速度时，火焰内部温度波动较大，随着燃料速度的增加，火焰内部和外部温度波动均增大。(3)在H_2/ n_2 -空气层状反扩散火焰中，受到来自燃料侧的微燃料的直接数值模拟和激光瑞利散射法的二维温度测量表明，来自燃料侧的微燃料射流应变的火焰容易局部熄灭，而来自空气侧的火焰几乎不熄灭，火焰温度有升高的趋势。(4)考虑了详细的化学动力学和多组分扩散的数值模拟，将(3)所描述的现象归因于与火焰曲率有关的物质间优先扩散所导致的燃料组分的H_2稀释或浓缩。(5)在准稳态火焰中，优先扩散对火焰曲率的影响突出，这主要归因于火焰的熄灭，但随着非稳态的增加，优先扩散对火焰曲率的影响变小。(6)在非定常火焰中，尽管有极高的拉伸率，火焰仍能瞬间保持高温，而在这种状态下，稳定的扁平火焰是不可能存在的。火焰的最高温度不能由局部拉伸率来合理确定，并且由于非定常效应而变化很大。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