Detonation Combustion In Supersonic Flow

Based on detonation combustion in supersonic combustible mixtures,in this thesis detonation initiation,propagation mode and self-sustaining mechanism were investigated with the combination of high-resolution adaptive simulations,experimental observation and theoretical analysis.In order to have a deep understanding of detonation initiation and propagation in supersonic combustible mixtures using a hot jet in depth,numerical simulations and experimental observation were carried out to investigate the influence of continuous injection of the hot jet on detonation initiation,propagation mode and its self-sustaining.The results show the injection of the hot jet into the supersonic incoming flow can prompt the formation of overdriven detonation.Detonation propagation in supersonic combustible mixtures can be controlled to some degree through the injection control of the hot jet.As for the Mach number and pressure of the supersonic incoming flow,there exists a range for successful initiation;as for the other parameters,there exists a critical value for successful initiation or not.Through experimental observation,there exist two combustion modes after the successful ignition of the hot jet in supersonic combustible mixtures.Aiming at the nonuniformity of the supersonic incoming flow,detonation simulations were conducted for nonuniform velocities and species respectively,to explore the possibilities of detonation initiation and its self-sustaining propagation in nonuniform supersonic combustible mixtures.The results show that in supersonic combustible mixtures with nonuniform velocities,a dynamically stable structure of shock/Mach detonation is formed and propagates forward at a constant velocity.In supersonic combustible mixtures with nonuniform species,the lateral expansion of detonation and a new dynamically stable state of detonation are found.Taking into account the influence of the combustor structure,detonation combustion in cavity-embedded channels and expanding channels were investigated respectively.The results show that the cavity can help to realize detonation initiation successfully and result in the formation of overdriven detonation.In expanding channels,the flow nonuniformity resulting from the expansion fan induces the generation of unburned jet behind the shock front.A new mechanism of rapid turbulent mixing between the unburned jet and the product is found along with the stationary detonation propagation.To some degree,detonation can propagate more quickly with larger expanding angles and expansion ratios.Based on the real three-dimensional detonation,large-scale three-dimensional detonation simulations in supersonic combustible mixtures with the detailed reaction model were conducted to investigate in depth the real detonation initiation and propagation using a hot jet.The results show that the side wall can accelerate the collision and reflection of the triple lines in three-dimensional simulations which makes a critical impact on detonation initiation in supersonic combustible mixtures.Although the characteristic parameters are almost the same,three-dimensional detonations have a secondary oscillation mode besides the common one.It is indicated that three-dimensional detonations show stronger instabilities,which is also verified through the quantitative comparison.