Experimental study of thermo-chemical conditions in ethanol flames

该项目的基本科学目标是研究复杂可再生燃料预混火焰中的化学-湍流相互作用的物理-化学过程。由于其技术相关性，乙醇作为一种更复杂的燃料特别适合这些研究。为了尽可能完整地量化热化学状态向量，必须开发一种基于自发拉曼/瑞利散射的新型测量装置。目的是同时，定量测量温度和所有主要物种浓度的预混乙醇火焰。这是一个挑战，因为与甲烷等更简单的燃料相比，反应区本身的中间（含氧）碳氢化合物（HC(O)）的数量和浓度都显着增加。因此，需要测量的主要物种的数量正在增加。为了开发一种能够同时测量火焰中中间HC(O)主要物种和乙醇浓度的技术，需要在三个中心主题上开展工作：(1)为了评估火焰中的浓度数据，必须确定乙醇和HC(O)物种在预混乙醇火焰中浓度较高时产生的温度依赖性拉曼响应。这些物质至少包括甲烷、乙烯以及醛类物质甲醛和乙醛。此类数据未在所需温度范围的文献中发表，或者根本无法获得。为此目的需要三种不同的流动装置，这将在项目过程中建立：首先，将开发一种新型气体加热器，它将允许将HC(O)-物种加热到非常高的温度。其次，将建立一个装置，用于连续产生确定流量的甲醛。第三，将实现一种用于稳定预汽化燃料乙醇火焰的喷射燃烧器配置。(2)对于研究，需要拉曼/瑞利光谱仪，它可以同时测量最突出的HC(O)中间体和其他主要物质（CO2, O2， CO, N2，燃料，H2O和H2）。为此，应开发一种新型光谱仪，它能够分离HC(O)中间体和乙醇的光谱紧密间隔的拉曼谱线。(3) HC(O)-中间体和乙醇的特征、温度依赖拉曼光谱将被测量并处理成一个文库。拉曼测量将首先在预混的层流乙醇火焰中进行，以便建立该方法。这些构成了开发适当的数据评估方法的基础，也是在第二个项目期间测量湍流乙醇火焰的基础。期望在激光燃烧诊断方面取得重大进展，以及在乙醇火焰湍流-化学相互作用的背景下对主要物种浓度的更好理解。

The essential scientific aim of the project is to examine the physico-chemical processes of chemistry-turbulence interaction in premixed flames of complex, renewable fuels. Due to its technical relevance ethanol as a more complex fuel is particularly suitable for these investigations. A novel measurement apparatus based on spontaneous Raman/Rayleigh scattering has to be developed in order to quantify the thermochemical state vector as completely as possible. The aim is the simultaneous, quantitative measurement of temperature and all major species concentrations in premixed ethanol flames. This is challenging since the number as well as the concentration of intermediate (oxygenated) hydrocarbon species (HC(O)) in the reaction zone itself is markedly increasing in comparison to more simple fuels like methane. Thus, the number of major species to be measured is increasing. Work on three central topics is required, in order to develop a technique able to measure the concentrations of the intermediate HC(O) major species as well as ethanol in flames simultaneously for the first time: (1) To evaluate the concentration data in flames, the temperature-dependent Raman response of ethanol and HC(O) species arising with higher concentrations in premixed ethanol flames must be determined. These species are at least methane, ethene as well as the aldehydes formaldehyde and acetaldehyde. Such data is not published in the literature for the required temperature range or is not available at all. Three different flow apparatus are required for that purpose, which will be set up in the course of the project: first, a novel gas heater will be developed, that will allow for heating the HC(O)-species up to very high temperatures. Second, an apparatus for the continuous generation of a defined flow of formaldehyde will be established. Third, a jet burner configuration to stabilize flames of the prevaporized fuel ethanol will be realized. (2) For the investigations, a Raman/Rayleigh spectrometer is required, which allows the most prominent HC(O) intermediates to be measured simultaneously to the other major species (CO2, O2, CO, N2, fuel, H2O and H2). For that purpose a novel spectrometer shall be developed, which is able to separate the spectrally closely spaced Raman lines of the HC(O)-intermediates and the ethanol from each other. (3) The characteristic, temperature-dependent Raman spectra of the HC(O)-intermediates and ethanol will be measured and processed into a library. Raman measurements will then be performed initially at premixed, laminar ethanol flames in order to establish the method. These form the basis for the development of an appropriate data evaluation method and also for measurements of turbulent ethanol flames in a second project period. Both a significant advancement in laser combustion diagnostics as well as an improved understanding of major species concentrations in the context of turbulence-chemistry interaction in ethanol flames are expected.