Zhao Yan, Tong Chenning, Ma Lin
Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634-0921, USA.
Appl Spectrosc. 2009 Feb;63(2):199-206. doi: 10.1366/000370209787392021.
The study of complicated flows continuously calls for new nonintrusive flow diagnostics. A novel flow visualization technique based on photodissociation spectroscopy (PDS) is described, demonstrated, and assessed in this paper. This technique is centered around the creative use of photodissociation (PD). A PD precursor is seeded in the flow of interest, either passive or reactive. A laser pulse is then generated to completely and rapidly photodissociate both the precursor and the products formed from the precursor (if it reacts) into photofragments. A target photofragment is then imaged to obtain multidimensional information about the flow. An analytical methodology was developed to assess the feasibility of the PDS-based technique. This analytical method was applied to the case where molecular iodine was used as an example PD precursor, and the results were validated by experimental data. Both the analytical and experimental findings provided a promising outlook for this new technique as a practical flow visualization technique. With a properly chosen PD precursor, the PDS-based technique provides an attractive alternative for imaging several critical flow properties, including the mixture fraction and temperature field. This technique shares some key advantages with established techniques, e.g., a high spatial and temporal resolution comparable to the planar laser-induced fluorescence (PLIF) technique. Meanwhile, this technique offers several unique advantages to overcome the limitations of existing techniques, including enhancing the signal level and simplifying the interpretation of the signal.
对复杂流动的研究不断需要新的非侵入式流动诊断方法。本文描述、展示并评估了一种基于光解离光谱（PDS）的新型流动可视化技术。该技术以光解离（PD）的创造性应用为核心。将一个PD前驱体注入感兴趣的流场中，它可以是被动的或反应性的。然后产生一个激光脉冲，使前驱体以及由前驱体形成的产物（如果它发生反应）完全且快速地光解离成光碎片。接着对目标光碎片进行成像，以获取有关流动的多维信息。开发了一种分析方法来评估基于PDS技术的可行性。该分析方法应用于以分子碘作为示例PD前驱体的情况，并通过实验数据对结果进行了验证。分析和实验结果都为这项新技术作为一种实用的流动可视化技术提供了广阔的前景。通过适当选择PD前驱体，基于PDS的技术为成像多种关键流动特性（包括混合分数和温度场）提供了一种有吸引力的替代方法。该技术与现有技术具有一些关键优势，例如具有与平面激光诱导荧光（PLIF）技术相当的高空间和时间分辨率。同时，该技术还具有一些独特优势，可克服现有技术的局限性，包括提高信号水平和简化信号解释。
