Study On Supersonic Premixed Mixtures' Detonation Initiation Via Hot Jet In Expanded Channel

Detonation combustion is an isochoric Fickett-Jacobs thermodynamic cycle, while the deflagration combustion is an isobaric Brayton-Joule one. The efficient of Fickett-Jacobs cycle is more higher than the Brayton-Joule one in theory. The possibility of a high increase in cycle efficiency is a main motivator for studies of the application of detonative combustion to the supersonic propulsion system. Using the experimental observation and numerical simulation, the representative supersonic premixed mixtures' initiation process in expanded channel via a hot jet have been investigated. The initiation characters have also been studies.The experiment observations show that the induced bow shock will bifurcate when reflects on the expanded channel. The hot jet's temperature and pressure is high. The bow shock will also induce combustion. The hot jet and the induced combustion promote the formation of detonation wave. Under the influence of the boundary layer, the initiated detonation will appear in partial. The initiation character is experimental studied by changing the hot jet's condition and the main flow's condition. Studies show that when the equivalent ratio is high. The initiated detonation will be overdriven easily. When the equivalent ratio is low, the detonation will initiate hardly and there will be the detonation reinitiation and quenching. When the main flow's static temperature is lower down, the partial detonation area will be less, but the ability to resist quenching will be stronger. When the hot jet's position is put forward to near the expanded starting place, the initiated detonation wave will be more wider in area, and it will be more difficult to reinitiate the mixtures when the detonation wave is quenched. When the diameter of the hot jet is smaller, the initiation time will be longer.The Block-structured Adaptive Mesh Refinement code is adopted and adjusted in simulation work. The representative process show that the mach stem will be stronger after the reflection on the expanded channel. Besides, the triple point and separate shock wave will form under the effect of the bow shock's reflection. The interaction between the separate shock wave and mach stem will accelerate the formation of detonation wave. The initiated wave's overdriven degree is small which is near the CJ state. The initiation character is numerical studied by changing the hot jet's condition and the channel's configuration. Studies show that when the hot jet's position is put forward, it will be hard to get the steady detonation wave. When the hot jet's position is put afterward it will be hard to form detonation wave. When the hot jet's diameter is smaller, the initiated detonation wave will more steady but the initiation time will be more longer. The expanded angle has an important influence on initiated detonation wave's propagation. When the expanded angle is bigger, the speed of the detonation' propagate forward will decrease significantly. When the height of the channel increase, the penetration of the hot jet will decrease and the reflection wave will become weak thus making the supersonic mixtures more difficult to initiate.