Combustion processes in gas turbines, rocket engines, and other propulsion devices are often accompanied by unstable operating conditions. Examples are thermo-acoustic instabilities in gas turbines, auto-ignition in oxygen-diluted combustors, and flame lift-off in high-speed propulsion systems. While such conditions provide unique opportunities for improving fuel efficiency and for reducing pollutant emissions, the accurate prediction and control of such combustion-dynamical processes introduces significant challenges. This seminar discusses research progress and current state-of-the-art on the development of LES-combustion models for the prediction of turbulent combustion regimes.
1) Single-mode Combustion Regimes: The first part of this seminar will focus on the utilization of flamelet-based combustion models for predicting single-mode combustion regimes. These models are particularly attractive for engineering application, and challenges in extending these models for predicting extinction, auto-ignition, kinetics-controlled combustion, and heat-loss-effects are identified. Subsequently, these modeling-aspects are separately addressed, and different modeling approaches are presented to predict relevant combustion-physical processes. Underlying assumptions are assessed using direct numerical simulation data, and modeling results for combustion simulations of increasing physical complexity are presented.
2) Regime-independent and Multimode Combustion: The second part of this seminar will focus on advanced research topics, addressing the specific question of selecting an appropriate combustion model to accurately describe complex and multimode combustion regimes. Often, expert knowledge or experimental data is required to make an informed decision, and computational resources introduce additional constraints in this selection process. By addressing these issues, recent research progress on the development of fidelity-adaptive combustion models, the assessment of the compliance of combustion models, and the formulation of regime-independent combustion models are examined. Comparison of simulation results for increasingly complex combustion configurations are considered to quantify benefits of these combustion models, and to identify further research opportunities.