Tomographic optical soot diagnostics in unsteady flames

尽管两国在交通电气化和能源转换脱碳方面做出了巨大努力，但在未来许多年里，化石燃料和其他碳基燃料的燃烧仍将是两国能源转换的主要领域。在这方面，减少燃烧过程产生的烟灰排放，无论是对健康的不利影响还是对全球变暖的重大影响，都是一项重大挑战。尽管在建模方面取得了很大的进展，但对湍流燃烧过程中烟灰的形成仍然没有完全的了解，例如与内燃机相关的过程。促进更好地了解的一个主要挑战是必须对复杂和波动的烟灰分布进行时间上高分辨率的探测。该项目通过实现对烟灰基本特征的四维（三维空间和时间分辨）测定来解决这一挑战。埃尔兰根和上海的团队的合作方式，他们的专业知识理想地互补，为开发这种先进的诊断工具奠定了最有希望的基础。提出的研究项目的总体目标是开发一种方法，该方法可以在其完整的三维结构中以高时间分辨率（kHz）测量烟灰的特征参数（浓度，初级粒径，温度）。为此，将进一步发展双色热法（2CP）和体积照明时间分辨激光诱导白炽灯（TiRe-LII）方法，并与先进的层析重建方法相结合。该方法的一个特点是通过使用定制的光纤束，以最小的实验费用实现了设置，总共使用三到四个高速摄像机同时测量2CP和TiRe-LII。该项目采用明确的步骤，在实验和数值研究之间密切协调。从具有已知特征的参考火焰出发，该方法最终可以应用于瞬态扩散火焰。为了快速有效地评估大量数据，LII和层析成像评估的算法都将进一步发展，包括使用卷积神经网络。在项目结束时，将有一个测量系统和评估技术，可以获得不同火焰类型的参考数据，以了解烟灰的形成和氧化，并验证数值方法。

Although great efforts are being made for the electrification of mobility and decarbonisation of energy conversion, the combustion of fossil and other carbon-based fuels will be a major sector of energy conversion in both China and Germany for many years to come. In this context, the reduction of soot emissions from combustion processes, both in terms of adverse health effects and the significant contribution to global warming, is a major challenge.Despite great progress in modelling, there is still no complete understanding of soot formation in turbulent combustion processes, as is, e.g., relevant for combustion engines. A main challenge in contributing to a better understanding is the necessity of a temporally highly resolved detection of complex and fluctuating soot distributions. This project addresses this challenge by enabling a four-dimensional (3D spatially and temporally resolved) determination of essential soot characteristics. The collaborative approach of the groups in Erlangen and Shanghai, whose expertise ideally complements each other, forms a most promising basis for the development of this advanced diagnostic tool.The overall objective of the proposed research project is the development of a method with which characteristic parameters of soot (concentration, primary particle size, temperature) can be measured with high temporal resolution (kHz) in their full three-dimensional structure. For this purpose, the methods of two-color pyrometry (2CP) and time-resolved laser-induced incandescence (TiRe-LII) with volumetric illumination will be further developed and combined with advanced tomographic reconstruction methods. A specific feature of the approach is the realization of a set-up with minimized experimental expenditure, performing simultaneous measurements of 2CP and TiRe-LII with three or four high-speed cameras in total, which is achieved through the use of customized fiber bundles.The project uses well-defined steps, closely coordinated between experimental and numerical studies. Starting from a reference flame with well-known characteristics, the method can finally be applied to a transient diffusion flame.For a fast and efficient evaluation of the large amounts of data, both the algorithms for LII and tomographic evaluation will be further developed including the use of convolutional neural networks. At the end of the project, a measurement system and evaluation technique will be available with which reference data can be obtained for different flame types to understand soot formation and oxidation and to validate numerical methods.