Investigation of Dual-Flame-Front Stabilization in Partially Premixed Hydrogen Flames Using Synchronized PIV/OH-PLIF

Abstract With the growing interest in hydrogen combustion, innovative strategies are required to achieve low-NOx, stable, and safe combustion systems. This study investigates partially premixed hydrogen flames stabilized on a swirled coaxial injector, focusing on the interaction between multiple flame fronts and their surrounding flow fields. The injector features a dual-swirl configuration, with air introduced in an annular channel and an H2/air rich premixed mixture supplied through the central channel. A variety of flame structures with varying swirl has previously been stabilized while achieving low nitrogen oxide emissions. While this injection technology is promising, the double flames resulting from air-staging yields a complex multi-regime structure that requires further investigation. The analysis is focused on two flame conditions, differing by the intensity of swirl, highlighting its role in defining flame structure and emissions. Synchronized Stereo PIV (SPIV) and OH-PLIF diagnostics are used to simultaneously capture the velocity field and flame contours, allowing detailed analysis of flame-flow interactions. The results reveal distinct flame behaviors that are scrutinized. These findings emphasize the impact of rich premixing and swirl intensity on flame stabilization and pollutant formation. By altering the interaction between the central recirculation zone, shear layers, and flame fronts, the injector’s design strongly influences both aerodynamic and chemical processes. This study provides valuable insights for optimizing hydrogen combustion systems to balance flame stability and emission control.