Interferometric laser imaging for droplet sizing: A method for droplet-size measurement in sparse spray systems
Interferometric laser imaging for droplet sizing: A method for droplet-size measurement in sparse spray systems
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DOI：
10.1364/ao.34.008409
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发表时间：
1995-12-20
期刊：
影响因子：
1.9
通讯作者：
Boyle, RD
中科院分区：
文献类型：
--
作者：
Glover, AR;Skippon, SM;Boyle, RD
报道了一种用于表征稀疏多分散喷雾体系的全场时间分辨干涉方法。该方法利用了广角前向散射区的角强度振荡。脉冲激光器用于通过喷雾照射平面片材，该喷雾从45度方向离焦成像。图像由一组散焦点组成，每个散焦点代表一个单独的液滴，并且叠加在散焦点上的是对应于该液滴的角强度振荡的一组条纹。用于图像分析的高分辨率数字化宏观摄影记录提供了全场能力。在图像平面中的每个斑点上的条纹的空间频率取决于在物平面中的相应液滴的直径，并且示出了一个简单的几何分析是适当的作为液滴尺寸的函数的条纹的空间频率的计算。通过软件套件自动分析图像，该软件套件使用高斯模糊、Canny边缘检测和Hough变换来定位图像场中的单个液滴。然后通过最小二乘拟合到Chirp函数来确定条纹空间频率。该方法适用于直径在几毫米至几百毫米范围内且数密度高达10（3）至10（4）的液滴。液滴尺寸测定的方法的准确性已被评估通过测量已知的液滴尺寸的单分散气溶胶，和测量的液滴尺寸分布在多分散气溶胶由汽油燃料喷射器产生的。该方法的一个扩展，使用高速摄影测量速度的两个分量，除了大小和位置，进行了讨论。一个双波长的方法也可以提供测量液滴中的模型燃料添加剂的浓度的能力，并描述了可行性研究的结果。
A full-field, time-resolved interferometric method for the characterization of sparse, polydisperse spray systems is reported. The method makes use of the angular intensity oscillations in the wide-angle forward-scatter region. A pulsed laser is used to illuminate a planar sheet through the spray, which is imaged, out of focus, from the 45 degrees direction. The image consists of a set of out-of-focus spots, each of which represents an individual droplet, and superimposed on which is a set of fringes corresponding to the angular intensity oscillations of that droplet. Macrophotographic recording with high-resolution digitization for image analysis provides a full-field capability. The spatial frequency of fringes on each spot in the image plane is dependent on the diameter of the corresponding droplet in the object plane, and a simple geometric analysis is shown to be appropriate for the calculation of the spatial frequency of fringes as a function of droplet size. Images are analyzed automatically by a software suite that uses Gaussian blur, Canny edge detection, and Hough transforms to locate individual droplets in the image field, Fringe spatial frequency is then determined by least-squares fitting to a Chirp function. The method is applicable to droplets with diameters in the range of several millimeters to several hundred millimeters and number densities of up to 10(3) to 10(4). The accuracy of the method for droplet-size determination has been evaluated by measurements of monodisperse aerosols of known droplet size, and measurements of droplet-size distribution in a polydisperse aerosol produced by a gasoline fuel injector are also presented. An extension of the method, using high-speed photography to measure two components of velocity in addition to size and position, is discussed. A two-wavelength approach may also offer the capability to measure the concentration of model fuel additives in droplets, and the results of a feasibility study are described.