基于广义彩虹散射的雾化场椭球形液滴测量方法的研究

Spray is one of the most important research subjects in thermophysics engineering and energy utilization. Sprays and droplets are involved in numerous industrial processes, e.g. spray combustion, spray drying, spray cooling and chemical engineering, etc. The investigation of new measurement techniques for droplet parameters including size, size distribution, and temperature is a processing problem in the world. Rainbow technique can be used to measure the droplet size，size distribution, and temperature. However, this technique is still limited to spherical droplet under the illumination of a parallel beam. The project aims to develop the rainbow technique to the tilted spheroidal droplet under the illumination of a convergent Gaussian beam. The research work includes: to investigate the evolution of the optical caustic structures in response to shape deformation of tilted spheroidal droplet illuminated by Gaussian beam, in terms of rainbow fringe and hyperbolic umbilic fringe; to reveal the relationship between the spheroidal parameters and the optical caustic structures; to measure the generalized rainbow patterns from the tilted droplet illuminated by Gaussian beam. Based on the simulations and experiments, the generalized rainbow technique will be able to meaure the size, aspect ratio, tilt angle, refractive index, and temperature of the droplet simultaneously. The research results of this project will provide a novel measurement technique for improving the research of spherical and spheroidal droplets in spray.

雾化是工程热物理与能源利用领域重要的研究课题，广泛应用于喷雾燃烧、喷雾干燥、喷雾降温、化工等众多工业过程中，探索雾化场中液滴粒度大小、分布及温度的测试技术是当前雾化特征研究的前沿问题。目前的彩虹技术主要针对球形液滴，通常采用平行光照射，测量参数包括液滴的粒度、分布及温度等。然而，对椭球液滴的测量还存在困难。本项目以高斯光束照射下的倾斜椭球形液滴为研究对象，采用矢量光线追踪方法，研究椭球形液滴的彩虹条纹和双曲脐条纹演化过程，建立液滴参数与彩虹散射的关联；实验研究高斯光束照射下液滴的彩虹散射图样；结合理论和实验研究，实现雾化场中液滴多个物理参数(包括液滴粒径、椭球度、倾斜角、折射率和温度)的同时、在线测量。该项目研究成果将发展一套完整的雾化场椭球形(和球形)液滴的测量方法，提高雾化过程的认识水平。

雾化广泛应用于喷雾燃烧、喷雾干燥、喷雾降温、化工等众多工业过程中，探索雾化过程中液滴粒度大小、分布、折射率及温度的测试技术是当前雾化特征研究的前沿问题，液滴的光散特性研究是实现液滴参数测量的基础。本项目围绕液滴散射理论和液滴测量方法展开研究，取得的主要研究成果包括：(1) 建立了倾斜椭球形液滴光学焦散的 Boundary理论模型，该理论模型适用于任意形状的液滴、高斯光束入射以及其他任意有形光束入射的情况；(2) 研究了高斯光束照射下液滴彩虹散射特性和液滴参数测量问题，首次在理论上证明了采用高斯光束为入射光源的彩虹技术测量液滴信息的可行性；(3) 研究了椭球形液滴高阶彩虹散射中光学焦散特性，证明了高阶彩虹散射中光学焦散结构也适用于液滴椭球度的测量；(4) 另外，基于矢量光线追踪模型，我们还研究了彩虹散射中Möbius shift问题，给出了Möbius和Können近似公式的适用条件。上述研究成果为液滴参数（粒度大小、分布、折射率和温度）的测量奠定了理论基础，为提高雾化过程的认识水平提供了测试方法。