Charalampous Georgios, Hardalupas Yannis
Mechanical Engineering Department, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
Appl Opt. 2011 Jul 10;50(20):3622-37. doi: 10.1364/AO.50.003622.
The droplet sizing accuracy of the laser technique, based on the ratio of laser-induced fluorescence (LIF) and scattered light (Mie) intensities from droplets, is examined. We develop an analytical model of the ratio of fluorescent to scattered light intensities of droplets, which shows that the LIF/Mie technique is susceptible to sizing errors that depend on the mean droplet size and the spread of the droplet size distribution. The sizing uncertainty due to the oscillations of the scattered light intensity as a function of droplet size is first quantified. Then, a new data processing method is proposed that can improve the sizing uncertainty of the technique for the sprays that were examined in this study by more than 5% by accounting for the size spread of the measured droplets, while improvements of 25% are possible when accounting for the mean droplet size. The sizing accuracy of the technique is evaluated in terms of the refractive index of liquid, scattering angle, and dye concentration in the liquid. It is found that the proposed approach leads to sizing uncertainty of less than 14% when combined with light collection at forward scattering angles close to 60° and the lowest fluorescent dye concentration in the liquid for all refractive indices.
基于液滴的激光诱导荧光（LIF）强度与散射光（米氏散射）强度之比，对激光技术的液滴尺寸测量精度进行了研究。我们建立了一个液滴荧光与散射光强度之比的分析模型，该模型表明，LIF/米氏散射技术容易受到尺寸测量误差的影响，这些误差取决于平均液滴尺寸和液滴尺寸分布的离散程度。首先对散射光强度随液滴尺寸变化的振荡所导致的尺寸测量不确定性进行了量化。然后，提出了一种新的数据处理方法，该方法通过考虑测量液滴的尺寸离散程度，可将本研究中所考察喷雾的该技术尺寸测量不确定性降低5%以上，而在考虑平均液滴尺寸时，尺寸测量不确定性有可能降低25%。该技术的尺寸测量精度根据液体的折射率、散射角和液体中的染料浓度进行评估。结果发现，当结合在接近60°的前向散射角处收集光以及液体中最低的荧光染料浓度时，对于所有折射率，所提出的方法导致的尺寸测量不确定性小于14%。
