Investigation Of Influence Mechanism Of The Wall Boundary Conditions On Detonation Initiation And Propagation

The wall boundary conditions play an important role both in the detonation initiation and propagation. Applying detonation to the propulsion system needs to explore the influence mechanism of wall boundary conditions on the detonation initiation and propagation. By means of theoretical analysis, numerical simulation and experimental studies, this dissertation systematically and thoroughly studies the influence mechanism of various wall boundary conditions on the initiation and propagation of detonation.Firstly, this dissertation studies the development of Deflagration to Detonation Transition (DDT) with H2 / Air mixture. At the critical state of initiation, the velocities of leading front and flame are about 1200m/s and 50%VCJ, respectively. Moreover, belt flame and a series of oblique shock on the wall between them are discovered, and rougher wall is beneficial to the belt flame form and develop. In the process of detonation initiation, obstacles can result the flame behind the leading front in acceleration, which is helpful for initiation of the detonation.Respectively propagating in the channels of obstacles and acoustically absorbing wall, the detonation will be both attenuated, even failed as the mixture isn't sensitive enough and the speed of failed detonation is reduce to about 60% CJ value. Subsequently, comparative numerical simulations of the detonation propagation and re-initiation in the obstacles wall channel are present with H2/Air single-step reaction model, which agrees well with the experimental results. The obstacles change the geometry of channel, therefore the detonation is be attenuated. Because the transverse waves reflect from the wall at the downstream channel, the attenuated detonation re-initiations.Finally, different characteristics and structures of the detonation propagating in the premixed supersonic stream are observed. The speed of the detonation near the wall boundary layer is higher than the detonation of mainstream, resulting geometry of the entire detonation wave in becoming plate, and make the propagation speed of mainstream area detonation be faster than CJ theory speed; Simulation in complete reaction model for H2/Air mixture is employed to simulate the propagation of the detonation in supersonic stream. The boundary layer leads to the bend of detonation and faster propagation speed than CJ value. The results also show that the influence of the low speed area near the wall on structure and speed of the detonation is great, while the influence of the high temperature area near wall is small.