Hydrodynamic and Acoustically Driven Instabilities of Jet-A1-Fueled Bluffbody-Stabilized Flames

The integrated fuel injector and bluffbody flameholder configuration is frequently employed in advanced aeroengine afterburners operating under elevated inlet temperature conditions. Although the non-premixed nature of liquid fuel injection into high-velocity vitiated crossflow plays a critical role in determining fuel spray structure and reacting shear layer dynamics, detailed measurements conducted under well-controlled afterburner-relevant conditions have been rare. To address this technical problem, we investigate hydrodynamic and acoustically driven instabilities of jet-A1-fueled bluffbody-stabilized flames arising from low-density-ratio conditions between 1.9 and 2.4, corresponding to bluffbody inlet temperatures of 900–1300 K and adiabatic flame temperatures of 2116–2373 K. Using combined analyses of single-shot OH planar laser-induced fluorescence and three-dimensionally reconstructed [Formula: see text] chemiluminescence distributions, we demonstrate that discrete fuel injection forms segregated U-shaped reaction zones at the trailing edges, leading to growth-merging and reemergence of parallel flame branches oriented perpendicular to the near-field development. The instabilities are governed by simultaneous excitations of hydrodynamic and acoustic modes, associated, respectively, with asymmetric vortex shedding at a Strouhal number of 0.19- and 20-kPa-level pressure perturbations coupled to the fifth-order longitudinal mode at 1.10 kHz. Spectral proper orthogonal decomposition identifies staggered growth-convection and wall impingement-dilatation of coherent structures with and without local extinction.