Phase-averaged, 3D OH-LIF reconstruction for multi-nozzle, micromixed hydrogen combustion

Micromix fuel injection strategies for hydrogen combustion produce multiple, distributed, compact, and often stratified flames. Single injectors can present highly-tridimensional and non-axisymmetric flame structures along the reactive fuel injection wakes. Their integration into multi-nozzle combustion systems, as commonly found in industrial applications, generates increasingly complex interactions between flames produced through this micromix injection and between neighboring nozzles. Two-dimensional, planar laser-based diagnostics can therefore only provide limited insight into the combustion process of these burners. Five premix/micromix injectors, positioned in a cross pattern, burning pure hydrogen are studied in this work. Three-dimensional (3D) OH volumes are interpolated from 25 OH planar laser-induced fluorescence (PLIF) slices over three inline injectors, resulting in a measurement volume spanning (). The laser diagnostic is registered with the acoustics signal to obtain phase-averaged datasets and capture the complex flame dynamics through a complete period. Comparison with single PLIF measurements demonstrates that, while a single slice provides valuable insight, out-of-plane motion and flame-flame interaction between distributed micromix injections and neighboring nozzles require increasingly complex diagnostics. The reconstruction captures flame merging between micromixed, jet-in-crossflow flames within a single nozzle and between injectors. It highlights the importance of injector clocking to mitigate the formation of hot spots in these systems.