Research On Detonation Initiation And Development Mechanisms In Elevated Temperature Supersonic Premixed Mixture

Starting from an analysis of chemical reaction mechanism and by means of theoretical analysis, numerical simulation and experimental studies, this dissertation systematically and thoroughly studies the direct initiation and development of detonation in high temperature premixed supersonic flow as well as the effect of initial temperature on detonation.By adopting the sensitivity analytical method, several popular hydrogen/oxygen detailed reaction models are verified by reference to the experimental data obtained from three kinds of reactor. It is found that relatively reasonable results can be obtained from the Connaire and Balakrishnam reaction models under a wider range of experimental conditions. Methods for simplifying complex reaction models are put forward on the basis of sensitivity analysis and quasi-steady state assumptions, and a set of reaction models suitable for the numerical simulation of hydrogen/oxygen detonation by using the adaptive chemical method are established.On the basis of detonation theory and analysis of the parameters and structure of detonation according to ZND model, it can be found that when the initial temperature of the mixture rises, the velocity of CJ detonation wave and pressure rise ratio will drop drastically. Since the temperature after the wave rises only slightly while the pressure rise ratio drops greatly, it can be seen that the influence of initial temperature of the mixture on the structure of detonation is a complex one. By analyzing the sensitivity of induction segment length in detonation structure and species consumption in heat release segment to reactions, and by studying the crucial species in induction segment and heat-released segment through element-tracking method, the key reactions and important species in detonation development are identified.The detonation development and the oblique detonation initiation and development in planar constant area duct are respectively simulated by using adaptive chemical numerical method. The research demonstrates that in detonation developmental in planar constant area duct, the traverse wave plays an important role in the evolution and development of detonation three wave point. The elevation of the mixture temperature will reduce the strength of traverse wave and three wave point, cause the structure of detonation to change into a 1D planar one, and make it more likely for detonation failure to occur in the development of self-sustained detonation. In the initiation and developmental process of oblique detonation, the elevated temperature of mixture will cause the onset location to move forward, and the change of detonation wave angle near the three wave point tends to become mild.A continuous high-enthalpy premixed supersonic combustor is designed. Through numerical simulation of its combination process and combustion delay analysis and experiment, it is proved that this combustor can not only ensure an effective combination process but also solve the pre-ignition problem. By adopting the high speed schlieren technique, the dynamic processes of the shock-induced combustion and detonation development are studied, and the influence of shock angle, mixture stoichiometric ratio and other factors on these processes as well as the underlying mechanism are analyzed. The result shows that the average propagation speed of detonation wave in high-temperature premixed flow is lower than that of CJ detonation. During the initiation, the interaction between combustion and flow slightly increases the shock angle, causing the temperature and pressure after the wave to rise slightly. When the flow after the wave is on the verge of detonation onset and large disturbance occurs, detonation will take place rapidly because of the interaction of shock and combustion. During the development, because of the instability of detached detonation itself and its coupled oscillation with the boundary, the detonation angle and the position of initiation location three wave point will oscillate; when the reaction mixture activity of combustible mixture increases, the three wave point of detonation will move abruptly upward. For the mixture of low mixture mobility, it is even hard for oblique detonation with relative large force to initiate the detonation and keep the status; with the increase of mixture mobility, the phenomenon of onset followed by detonation failure and then followed by onset again will occur in the detonation developmental process; and with the further increase of mixture mobility, the detached detonation will be able to keep developing.