Development and characterization of swirl-stabilized diffusion mesoscale burner array

A diffusion mesoscale burner array with integrated fuel manifold and injection holes has been developed for compact and efficient propulsion and power systems. Each burner element is equipped with its own fuel injection holes built into its swirl-inducing geometry to improve flame interaction and reduce flame length. The diffusion mesoscale burner array provides comparable performance to a premixed mesoscale burner array under similar operating conditions despite fuel unpremixedness. Overall, diffusion flames on the mesoscale burner array exhibit 7.8% lower global equivalence ratios at lean blow-off conditions compared to premixed flames. Imaging of two primary combustion intermediates, OH and CH2O, is carried out using planar laser induced fluorescence to visualize the post- and pre-combustion zones of diffusion and premixed flames. Simultaneous 10 kHz high-speed OH fluorescence images and pressure measurements are used to study flame response and stability under external acoustic perturbation at a frequency of 200 Hz. OH fluorescence images show higher heat release and flame front fluctuations for diffusion flames. Rayleigh index reveals similar thermo-acoustic stability characteristics between diffusion and premixed flames. However, diffusion mesoscale flames exhibit large flame surface variation under external acoustic perturbation by spectral proper orthogonal decomposition analysis.