Spray combustion characteristics of boron-containing gel in high particle loading conditions

Boron-containing gel demonstrates significant potential in terms of energy performance, safety, and controllability. However, the impact of high boron content on the combustion characteristics of gel fuels remains poorly understood. In this study, employing a flat flame burner and a comprehensive diagnostic approach, the influence of boron content (20%–50%) on the spray combustion characteristics of boron-containing gel fuel was systematically investigated. Dual microexplosion phenomena were identified: primary microexplosions of gel droplets and secondary microexplosions of boron agglomerates. Flame characteristic parameters revealed that as the boron content increases, the flame boundary initially expands and then contracts. BG50 exhibited a theoretical calorific value 1.13 times higher and a density 1.51 times greater than those of pure kerosene. Analysis of condensed combustion products revealed the presence of both irregular and spherical boron agglomerates, along with more severe agglomeration, larger agglomerate sizes, denser surfaces, and lower oxidation degrees at higher boron loadings. Temperature measurements confirmed that all boron-containing gels attained higher temperatures than pure kerosene, although BG50 showed a relative decrease compared to BG40. We anticipate that the complete release of energy from high-boron-loading gel fuels can be achieved by optimizing their rheological properties, modifying the boron particles, and promoting microexplosions.