Multi Regime combustion under technically relevant conditions: Experimental and numerical investigation of thermo-chemical states and flame structures

• Applicants: Professor Dr. Andreas Dreizler; Professor Dr.-Ing. Dirk Geyer; Professor Dr. Christian Hasse
• Subject Area: Energy Process Engineering
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325144795

Multi-regime combustion, also known as partially premixed or multi-mode combustion, describes flames in which premixed and non-premixed reaction zones exist and interact in close proximity to each other. These complex flame structures are common in technical systems and require detailed investigations to understand and model the underlying mechanisms. In the first funding period (FP1) of this project, significant progress was made in the experimental and numerical characterization of multi-regime combustion. A novel multi-regime burner (MRB) was developed that allows full optical accessibility for mixture formation and flame stabilization outside the burner. This design includes a recirculation zone that replicates technically relevant stabilization mechanisms, allowing a wide range of multi-regime conditions to be set. Experimental investigations included extensive characterization of the flow and reaction fields using 1D Raman/Rayleigh spectroscopy, planar laser-induced fluorescence (PLIF), particle image velocimetry (PIV) and chemiluminescence. In parallel, numerical simulations were performed using flamelet models and large eddy simulations (LES). The introduction of the novel gradient-free regime identification (GFRI) method enabled a precise analysis of local flame structures and their classification into different combustion regimes. The second funding period (FP2) will focus on the investigation of H2-enriched, highly swirled, confined flames. This change introduces two new scientific challenges: the interaction of local reaction zones with the highly swirled turbulent flow and the effects of differential diffusion on the local thermochemical state. Planned activities include: (1) performing high-resolution measurements of flame structure and thermochemical state in an advanced multi-regime burner for H2/CH4 mixtures, (2) developing a 2D flamelet model that accounts for differential diffusion and multi-regime conditions in H2/CH4 combustion, and (3) integrating the experimental and numerical methods for detailed analysis of multi-regime combustion (prior and a-posteriori analyses). These comprehensive investigations are only made possible by the close cooperation between the participating research institutions and are supported by the involvement of a Mercator-Fellow. The results will both deepen the fundamental understanding of multi-regime combustion and lead to improved models that can be used in the development of more efficient and environmentally friendly H2-based combustion systems.

• DFG Programme: Research Grants