Numerical investigation on mode transition of H2–O2–Ar detonation with stratification in confined channel

To reveal the propagation characteristics of non-uniform detonation, a high-fidelity numerical investigation on the propagation characteristics of layered H2–O2–Ar detonations in confined channels is conducted. The simulations are performed by solving the two-dimensional Navier–Stokes equations with a detailed chemical mechanism. Artificial inert species (H2* and O2*) are introduced to ensure the inert layer shares identical thermophysical properties with the reactive layer, purely isolating the reactivity effect. The influences of inert layer width, channel width, and argon dilution ratio are systematically examined. The results indicate that as the inert layer width increases, the propagation of detonation undergoes distinct mode transitions: from normal propagation mode to intermittent propagation mode in which detonation quenches and reignites intermittently, and then pulsating propagation mode in which no new transverse wave is generated after the detonation reignition. The critical re-ignition mechanism is closely associated with strong transverse waves. These transverse waves strengthen the leading shock and induce local explosions via wall reflections. Thermodynamically, the propagation speed decreases approximately linearly with the inert layer width ratio due to energy loss from product expansion into the inert layer. At high width ratios, the overdriven states during reignition maintain the propagation speed above the theoretical value assuming that the pre-shock gases are well mixed. Furthermore, unstable mixtures (10% Ar) exhibit significantly smaller speed deficits compared to stable ones (70% Ar), as their inherent stronger transverse wave generation capability effectively compensates for energy losses. These findings provide profound insights into non-ideal detonation phenomena in engineering applications like film cooling in rotating detonation engines.