Tomographic optical soot diagnostics in unsteady flames

尽管在交通电气化和能源转换脱碳化方面做出了巨大努力，但化石燃料和其他碳基燃料的燃烧将是未来许多年中国和德国能源转换的主要领域。在这种情况下，减少燃烧过程中的烟尘排放，无论是从对健康的不利影响还是对全球变暖的重大贡献来看，都是一个重大挑战。尽管在建模方面取得了很大进展，但仍然没有完全了解湍流燃烧过程中的烟尘形成，例如，与内燃机相关。一个主要的挑战，有助于更好地理解是一个时间上的高分辨率检测复杂和波动的烟尘分布的必要性。该项目通过实现基本烟尘特性的四维（3D空间和时间分辨）确定来解决这一挑战。埃尔兰根和上海的研究小组的协作方法，其专业知识完美地互补，为开发这种先进的诊断工具奠定了最有前途的基础。拟议研究项目的总体目标是开发一种方法，可以在它们的全三维结构中以高时间分辨率（kHz）来测量这些参数（浓度、初级颗粒尺寸、温度）。为此，双色高温测量（2CP）和时间分辨激光诱导白炽（TiRe-LII）与体积照明的方法将进一步发展，并结合先进的断层重建方法。该方法的一个具体特点是实现了最小化实验费用的设置，通过使用定制的光纤束，总共使用三个或四个高速相机同时测量2CP和TiRe-LII。该项目使用定义明确的步骤，在实验和数值研究之间密切协调。为了快速有效地评估大量数据，将进一步发展LII和层析成像评估算法，包括使用卷积神经网络。在项目结束时，将提供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，以了解碳烟的形成和氧化，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.