Chemical kinetic models are key components for understanding and simulating reactive combustion processes. Our goal is to provide accurate and efficient models for the CFD and to apply them directly to provide initial assessments of conceptual design of the combustion system.
The department's core competencies include the creation and further development of detailed chemical kinetic models for aviation and aerospace fuels, transport fuels, and general fuels. These competencies are supported by quantum chemical methods for determining thermophysical properties and key reaction rates as well as by in-house experimental investigations in shock tubes, flow reactors, and laminar burners.
Advanced optimization methods are developed and used to improve the accuracy of chemical kinetic models. The department uses a highly efficient, in-house method: the linear transformation model (linTM). The model reduces the numerical costs by orders of magnitude compared to conventional methods. This opens up new possibilities for the optimization of comprehensive chemical kinetic models using extensive experimental data with numerically justifiable effort.
The method for rapidly reduction of the chemical kinetic models is derived on the basis of analysis and optimization methods from linTM. The thus reduced models enable significantly higher degrees of reduction compared to conventional methods. By re-optimizing the reduced model for intermediate species, ignition delay times, and flame speeds, a high level of accuracy is achieved, similar to that of a detailed model.
In addition, the department develops surrogate fuels to map thermophysical and chemical properties of complex fuels across several substances or classes of substances. These precisely defined model fuels can then be used, for example in CFD simulations, to reduce the complexity of the simulation. At the same time, these model fuels are used in experiments to determine the experimental boundary conditions for better reproducibility.
The various chemical kinetic models are applied directly for the conceptual design of internal combustion engines. This includes determinations of ignition delay times, laminar flame speeds, and pollutant formation potentials under technically relevant conditions as well as their transfer to technically relevant quantities such as, for example, octane/cetane numbers or turbulent flame speeds.
Literature
Goos, E.; Sickfeld, C.; Mauss, F.; Seidel, L.; Ruscic, B.; Burcat, A.; Zeuch, T., Prompt NO formation in flames: The influence of NCN thermochemistry. Proceedings of the Combustion Institute 2013, 34, 657-666.
Methling, T.; Braun-Unkhoff, M.; Riedel, U., An optimised chemical kinetic model for the combustion of fuel mixtures of syngas and natural gas. Fuel 2020, 262, 11.
Kathrotia, T.; Richter, S.; Naumann, C.; Slavinskaya, N.; Methling, T.; Braun-Unkhoff, M.; Riedel, U. 2018, Reaction Model Development for Synthetic Jet Fuels: Surrogate Fuels as a Flexible Tool to Predict Their Performance. In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition.