Physics

Internal medicine

Mach number

Organic chemistry

Acetylene

Hydrogen

Mechanics

Oblique shock

Atomic physics

Explosive material

Chemistry

Detonation

Shock (circulatory)

Quantum mechanics

Oxygen

Argon

Shock wave

Medicine

Thermodynamics

Physics of Fluids

Stoichiometric acetylene-oxygen mixtures diluted by argon are widely used in normal detonation waves but have not yet been used in oblique detonation waves (ODWs). The present study simulates ODWs in acetylene-oxygen-argon mixtures, with a dilution ratio Φ = 50%-90%, using the reactive Euler equations with a detailed chemistry model, and describes the characteristics of acetylene ODWs. Similar to ODWs in hydrogen-air mixtures, the transition from the oblique shock wave to ODW may be either abrupt or smooth and the effects of Φ are investigated with a variable incident Mach number M0. When M0 changes between 8 and 10, the transition is abrupt in the case of Φ = 50%, while it is smooth in the case of Φ = 90%. In the case of Φ = 70%, a high M0 corresponds to a smooth transition, while a low M0 corresponds to an abrupt transition. A further study on the initiation mechanism was performed by comparing the numerical initiation length with the length obtained via the constant-volume combustion calculation, which demonstrated that the initiation is kinetic-controlled in the cases of Φ = 70% and 90%, but wave-controlled in the case of Φ = 50% with M0 below 8.5. Moreover, an initiation structure featured by two-shock in the product was observed for the first time, and its formation mechanism is qualitatively discussed and compared to hydrogen ODWs.

Structure of wedge-induced oblique detonation in acetylene-oxygen-argon mixtures