为实现雾化过程中局域内单液滴的测量, 采用德拜级数展开研究了高斯光照射下球形液滴一阶彩虹区域的散射光强分布, 以及高斯光束腰大小对光强分布峰值角度的影响.根据德拜级数展开计算的散射光强分布反演液滴的折射率和粒径,证明了根据高斯光的彩虹散射反演液滴信息的可行性.基于广义洛伦兹-米氏理论计算一阶彩虹区域的总光强分布, 根据总光强分布反演液滴折射率和粒径, 讨论了高斯光束位置对反演液滴信息的影响.对于半径在200~1 000 μm区间的液滴, 高斯光束位于中心入射时, 反演折射率的误差小于2.38×10-4, 粒径的相对误差在-3.31%~3.31%之间.与采用平行光彩虹技术相比, 采用高斯光束为入射光可以得到较高的光能聚集区, 较好地定义测量区大小,既可以有效避免多个液滴同时出现在测量区的情况、减小颗粒之间复散射的影响, 又可以提高信号强度.

For the measurement of a single drop in spray, the Debye series for scattering of a Gaussian beam by a spherical drop is used to study the light intensity distribution in the primary rainbow region and the influence of the Gaussian beam on the peak position of the intensity distribution. According to the intensity distribution calculated by the Debye series, the refractive index and size of drop are inversed, which prove that the Gaussian beam scattering could be used for drop measurements. And then, generalized Lorenz-Mie theory is used to compute the total light intensity which is used to inverse the refractive index and size of drop. And the influence of Gaussian beam position on the inversion of drop information is also investigated. For a Gaussian beam centered on the Descartes ray position, the absolute error of the refractive index is smaller than 2.38×10-4 and the absolute value of relative error of drop radius is smaller than 3.13% for drops with a radius between 200 and 1 000 μm. Compared with the rainbow technique using parallel beam, it possible to obtain a measurement area with high intensity and appropriate volume by using Gaussian beam. Therefore, the simultaneous occurrence of many drops in measurement area can be effectively avoided. And we could reduce the influence of multiple scattering between drops and increase the signal intensity.