Measurements of Ignition Delay Times and Species Concentrations in a Rapid Compression Machine

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Basic Information

Duration:
01.01.2019 to 31.12.2025
Organizational Unit:
Combustion Fundamentals
Funding:
German Research Foundation (DFG)
Status:
Running

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During the development of potential future fuels in the FSC Cluster, it is critical to understand the fundamental combustion kinetics of the candidate molecules. Therefore, kinetic models are built, which have to be validated and tested in order to be used for application relevant simulations. Ignition delay times are a well-established validation target for the overall reactivity of a certain fuel. In our rapid compression machine (RCM), we are able to rapidly and reliably screen different neat fuels and fuels mixtures. Besides, variations of temperature, pressure, stoichiometry, dilution, and vaporizable fuel-additives are possible.

To gain further inside into the ignition process, concentration profiles for the fuel and intermediate species are measured in the course of this project. These concentration profiles allow then the in-depth validation of certain reaction pathways and critical branching ratios, which leads to more precise kinetic models. Additionally, certain intermediates, which are considered pollutants or might be harmful, can be tracked in the early fuel development process. To measure the species concentrations both gas sampling and laser absorption techniques are used. The sampling of gas probes during the ignition process allows for subsequent analysis in a gas chromatography - mass spectrometry (GC-MS) system, which is able to detect and quantify a variety of (oxygenated) hydrocarbon species. As the experiment is influenced by the sampling process, only a single point in time can be investigated per experiment while using this method. To gain a time-resolved signal from a single experiment, laser absorption techniques are applied. Additionally, also unstable intermediates can be detected, which is not possible by the GC-MS system. As laser absorption techniques are typically limited in the wavelength range at operation, only a limited number of intermediates (typically only one) can be tracked. By combining both techniques we can gain in-depth insights into the combustion characteristics of potential bio-hybrid fuels and contribute to the fuel design process within the FSC.