Strange wave formation and detonation onset in narrow channels

Experiments are conducted in a smooth 10 × mm square cross-section, 1-m long channel, closed at the ignition end and open other end. Simultaneous two-direction schlieren visualization is used to investigate three-dimensional dynamics of transition detonation for stoichiometric H2–O2 mixture. Results show existence two distinct structures before onset: (i) asymmetric, composed an oblique shock trailed by flame, that runs preferentially along wall, seems get ignited inside boundary layer developed precursor shock; (ii) symmetric, referred as strange wave literature, propagating roughly speed sound combustion products. The combined effect induced preheating viscous heating near walls seem be responsible formation complex flame-shock interactions observed. A simple thermodynamic analysis applied using experimentally measured yield pressure ratio ~ 15 during its steady propagation; furthermore, estimate total energy losses required thermodynamically realize such propagation regime revealed approximately half released should dissipated (i.e. momentum heat losses). Finally, simultaneous optical access allows map exact location onset, showing 78 % cases exploded corners, highlighting role corner flows layers this scale.