Turbulent flame propagation in obstacle-filled tubes

摘要: Turbulent flame acceleration experiments have been carried out in steel tubes of 5 cm, 15 cm and 30 diameter ranging from 11 m to 17 length. Circular orifice plates spaced on apart were used as flow obstructions. The blockage ratios BR=1−(d/D)2 are 0.44, 0.39 0.28 corresponding diameters 3.74 11.7 25.8 for the tubes, respectively. Mixtures hydrogen, acetylene, ethylene, propane methane with air over a range fuel compositions. results indicate existence four propagation regimes: quenching, choking, quasi-detonation C-J detonation regimes. In quenching regime, is first found accelerate then extinguish itself after propagating past certain number plates. process regime can be considered successive ignition sequence chamber separated by Ignition one due venting hot combustion products upstream through orifice. Quenching occurs when jet fails ignite mixture too short mixing time compared chemical reaction time. For mixtures very near limits, an alternative mechanism stretching proposed. When not quenched, it eventually reaches steady state. It that gasdynamic choking (sonic conditions) friction heat release provide controlling state speed. Again, limit mixtures, condition may brought about positive negative effects augmentation burning rate. most cases interest, prevails. more sensitive transition observed. criterion requires ratio d cell size λ 1d/λ≤13. present study where order BR≈0.4, critical value d/λ≈3. under these conditions observed travel obstacle-filled tube at velocities significantly below normal accord previous observations rough tubes. Such detonations referred quasi-detonations. sufficiently such d/λ13, becomes insensitive obstacles front propagate wave.