预混燃烧火焰的光偏折层析三维动态可视化

使用光偏折层析(CT)方法研究了非稳态预混燃烧流 场的参数测量及火焰结构表征。建立了适用于瞬态流场层 析的叠栅光偏折投影条纹图有序阵列采样系统,实现了单光栅副、单CCD、多方向、同时和 同光路条件的动 态采样。构建适用于少数投影光偏折计算层析的混合正则化重建算法。实验测量中,对C 4H10/空气预混燃烧 流场进行6视角动态采样,使用混合正则化算法对燃烧流场进行截面二维温度分布重建,使 用Sobel梯度 算子进行火焰内外区域温度分布的阈值分割。对4个不同时刻共计150 条莫尔条纹进行信息提取并重建出 20个截面的温度分布,使用移动立方体面绘制算法和光线投射体绘制 算法对三维体数据进行 显示,实现了燃烧流场参量分布及火焰结构的三维动态可视化。

Three-dimensional dynamic visualization of premixed flame based on optical deflection tomography

The distributions of premixed combustion parameters and the flame stru ctures are investigated using deflection tomography.A projection sampling system for defle ction tomography is presented to obtain the chronological arrays of Moiré fringe patterns.Deflecto grams at six view angles are captured synchronously in the same optical path condition using only a pair of gratings.This kind of apparatus is suitable for the tomographic measurement of the transient flow field.Hybrid regularization method for deflection tomography is introduced to reconstruct th e two-dimensional temperature distribution of the premixed combustion.The experimental investigat ion is performed using a premixed flame by burning a mixture of C₄H₁₀ and air.The samplin g system is used to obtain six orientation Moiré fringes.150fringes in total are processed and temperature distributions in 20cross sections are reconstructed from projection data in different moments usi ng hybrid regularization method. The reconstruction result is in an average error of ~5% when compared with the thermocouple measurement.The Sobel operator is applied to the threshold segmentation of tw o-dimensional temperature distributions.Visualization tool kit with the marching cube and ray casting algorithms is employed to reconstruct the flow structure.The experiment results demonstrate t hree-dimensional dynamic visualization of the temperature distributions and the flame structures of a pre mixed combustion.