This work describes the diagnostic implementation and image processing methods to quantitatively measure diesel spray mixing injected into a high-pressure, high-temperature environment. We used a high-repetition-rate pulse-burst laser developed in-house, a high-speed CMOS camera, and optimized the optical configuration to capture Rayleigh scattering images of the vaporized fuel jets inside a constant volume chamber. The experimental installation was modified to reduce reflections and flare levels to maximize the images’ signal-to-noise ratios by anti-reflection coatings on windows and surfaces, as well as series of optical baffles. Because of the specificities of the high-speed system, several image processing techniques had to be developed and implemented to provide quantitative fuel concentration measurements. These methods involve various correction procedures such as camera linearity, laser intensity fluctuation, dynamic background flare, as well as beam-steering effects. Image inpainting was also applied to correct the Rayleigh scattering signal from large scatterers (e.g. particulates). The experiments demonstrate that applying planar laser Rayleigh scattering at high repetition rate to quantitatively resolve the mixing of fuel and ambient gases in diesel jets is challenging, but possible. The thorough analysis of the experimental uncertainty and comparisons to past data prove that such measurements can be accurate, whilst providing valuable information about the mixing processes of high-pressure diesel jets.

这项工作描述了用于定量测量喷射到高压高温环境中的柴油喷雾混合的诊断实现和图像处理方法。我们使用内部开发的高重复频率脉冲猝发激光器，高速CMOS相机，并对光学结构进行了优化，以捕获恒定容积室内汽化燃料喷嘴的瑞利散射图像。通过对窗户和表面以及一系列的光学挡板进行减反射涂层，对实验装置进行了修改，以减少反射和眩光水平，从而最大程度地提高图像的信噪比。由于高速系统的特殊性，必须开发和实施几种图像处理技术来提供定量的燃料浓度测量。这些方法涉及各种校正程序，例如照相机线性度，激光强度波动，动态背景光斑以及光束转向效果。还应用了图像修补来校正来自大型散射体（例如颗粒）的瑞利散射信号。实验表明，以高重复率应用平面激光瑞利散射来定量解决柴油喷气机中燃料和环境气体的混合是有挑战性的，但可能。对实验不确定性的彻底分析以及与过去数据的比较证明，这种测量是准确的，同时提供了有关高压柴油机喷流混合过程的宝贵信息。还应用了图像修补来校正来自大型散射体（例如颗粒）的瑞利散射信号。实验表明，以高重复频率应用平面激光瑞利散射来定量解决柴油喷气机中燃料和环境气体的混合是有挑战性的，但可能。对实验不确定性的彻底分析以及与过去数据的比较证明，这种测量是准确的，同时提供了有关高压柴油机喷流混合过程的宝贵信息。还应用了图像修补来校正来自大型散射体（例如颗粒）的瑞利散射信号。实验表明，以高重复频率应用平面激光瑞利散射来定量解决柴油喷气机中燃料和环境气体的混合是有挑战性的，但可能。对实验不确定性的彻底分析以及与过去数据的比较证明，这种测量是准确的，同时提供了有关高压柴油机喷流混合过程的宝贵信息。但可能。对实验不确定性的彻底分析以及与过去数据的比较证明，这种测量是准确的，同时提供了有关高压柴油机喷流混合过程的宝贵信息。但可能。对实验不确定性的彻底分析以及与过去数据的比较证明，这种测量是准确的，同时提供了有关高压柴油机喷流混合过程的宝贵信息。