EXPERIMENTAL STUDY ON HYBRID DETONATION OF HYDROGEN-AIR MIXTURE WITH SUSPENDED METAL PARTICLES

Hybrid detonation phenomena encompass a complex interplay of gas-phase and heterogeneous reactions, showcasing a rich diversity of behaviors. To unlock the transformative potential of detonation propulsion technology in novel applications, a profound understanding of hybrid detonation is paramount. In this study, we harnessed a horizontal detonation tube to conduct experiments on hybrid detonations involving hydrogen-air mixtures and suspended aluminum powder. Through meticulous blending of micro-sized and nano-sized spherical aluminum powders with stoichiometric proportions of hydrogen and air, the resulting mixture was directly initiated within a 13-meter-long and 224-millimeter-diameter detonation section. This investigation unveiled an array of hybrid detonation waveforms, encompassing both single and double shock structures, depending on the particle sizes of the aluminum powders. By delving into the ignition and combustion characteristics of aluminum particles within the detonation gases, we elucidated the direct impact of heterogeneous reactions on the wave structure of hybrid detonations. For instance, when using 100 nm or 1 μm aluminum particles, the hybrid detonations displayed single-shock structures, featuring heightened detonation velocity and peak pressure compared to their gas-phase counterparts. Notably, the exothermicity of aluminum particles' ignition initiated prior to reaching the sonic surface. Conversely, with 20 μm or 40 μm particles, a delayed ignition led to double-shock structures in the hybrid detonations, where gas-phase reactions supported the initial shock, while heterogeneous combustion bolstered the subsequent one. Notably, for 10 μm particles, the pressure curves exhibited a singular peak with significantly elevated pressure, despite no increase in detonation velocity. This essentially represented a double-shock structure with closely spaced shocks, indistinguishable within the pressure curves due to limitations in the sensors' spatial resolution. The experimental outcomes collectively offer an extensive comprehension of hybrid detonation. They shed light on the ignition and combustion characteristics of aluminum particles under intricate conditions, and underscore the pivotal role of heterogeneous reactions in shaping the complex nature of hybrid detonation.