Investigation On Mechanism Of Detonation Initiation By Hot Jets

The initiation of detonation is a key problem for detonation combustion system. Hot jet initiation is believed to be a promising way for detonation initiation because of its high energy. By means of theoretical analysis, numerical simulation and experimental studies, this dissertation systematically and thoroughly studies the process,mechanism and application of detonation initiation by hot Jets.Firstly, choosing detonation tubes as the object, the single pulse detonation operating DDT(Deflagration to Detonation Transition) characteristics of detonation tubes with quiescent H2/Air mixtures are studied experimentally. Disturbing the flow can avail in DDT, and the parameters of length, spacing and starting location and etc of schelkin is of huge importance in initiation; DDT can be realized in mixing ratio from 0.65 to 2.0 when using a proper inner diameter in tube. The minimum length of schelkin of a detonation tube with a 1580mm longth and 32mm inner diameter is summarized by experiment. As a comparison, experiments in dynamic filled detonation tubes are carried out, which provide a detonation wave with lower pressure and detonation velocity.To enhance the energy of flame jet, a notion of contractive configuration designing is put forward, the effect of it is confirmed by simulation, and the principles of the selection of jet enhance configurations are summarized: the later convergence, larger convergence scale and use of multilevel convergence. Simulation in 9 component/21 equation elementary reaction model for H2/Air mixtures is employed to simulate the process of the shock wave propagate the contractive configuration, explaining the mechanism of detonation initiation by reflected transverse wave assembling. Then an abundance of experiments focusing on the effects of convergence configurations on detonation jet are implemented, which provide with pressure and cellular information. Subsequently, comparative numerical simulations on the cellular evolution around contractive configurations are put forward with H2/Air single-step reaction model.Basing on the study of principles of jet, through the study of initiation in quadrate by chamber High-energy spark, flame jet and detonation jet experimentally, the necessity of the application of jet initiation is validated. Experiments and numerical simulations on the mechanics of horizontal and transversal initiations, including the development of pressure and the propagation of cellular structures, are employed with different tube diameters and jet types. The high speed schlieren technique is implement ed to shoot the process of hot jet initiation and propagation of detonation. The initiation by hot jets is due to"hot spot"and is started from over-driven detonation, decay ing gradually to CJ detonation. And the transversal jet ejecting method is found better than the horizontal one. Variety of transversal jet initiation related parameters, such as jet speed, jet location, jet angle, and jet width, are simulated in detail. Ultimately, jet initiation is experimentally implemented in the initiation of annular detonation chamber successfully.