Swirl Flame Stability for Hydrogen-Enhanced LPG Combustion in a Low-Swirl Burner: Experimental Investigation

Recent progress in hydrogen combustion indicates that hydrogen could partially or fully replace traditional fuels in power plants, but maintaining stable flames remains a major challenge for many combustion systems. This study presents the effect of hydrogen enrichment of Liquid Petroleum Gas (LPG) on the low-swirl flame structure and flame temperature at different hydrogen mass fractions and equivalence ratios (φ = 0.501 and 1.04). The experimental observations for low-swirl flames under various conditions, including the effect of increasing hydrogen enrichment from 0% to ~20%, were discussed. Experiments were performed using a swirl burner, flame photography, and temperature measurements to evaluate the dynamic swirl flame, stability, and flame temperature distribution. The results show that moderate hydrogen enrichment (5–15%) improves flame stability and delays blow-off. In contrast, very high hydrogen concentrations may destabilize the flame due to higher reactivity and enhanced sensitivity to flow perturbations. Also, hydrogen enrichment up to ~20% enhances flame compactness, intensifies heat release, and reduces oscillatory instability without triggering blow-off or flashback, making hydrogen blending a promising strategy for stabilizing swirl flames at rich operating conditions. Finally, hydrogen enrichment consistently increases swirl flame temperature at both equivalence ratios.