Experimental study on detonation characteristics of liquid fuel under near-lean limit conditions

This study delves into the contradiction between lean combustion and detonation stability in liquid-fueled pulse detonation engines (PDE) by employing a stratified combustion organization method with secondary oxidizer injection. The experiments on the detonation combustion characteristics of liquid fuel near the lean limit used 92# gasoline, 40% oxygen-enriched air, and air as reactants. Experimental results indicate that injecting a secondary stream of oxidizer after the deflagration-to-detonation transition (DDT) segment allows for stable multi-cycle detonation under globally lean conditions, even with an equivalence ratio as low as φ = 0.89. Additionally, this approach reduces the DDT distance by 34% through enhanced turbulence and boosts thrust by approximately 28.6%. Conversely, injecting the secondary stream before the DDT segment fails to produce a fully developed detonation wave. Furthermore, increasing fuel pressure further reduces the global equivalence ratio of the PDE. When combined with secondary oxidizer injection, this optimizes the isolation effect for high-frequency detonation.