Study On The Initiation And Propagation Characteristics Of Detonation Waves In Annular Channels

The development of detonation waves has great practical significance to the future propulsion technology,especially the propagation characteristics and mechanism of detonation waves in annular channels are the foundation of the study of rotating detonation engine.The propagation mechanism of detonation waves in annular channels is more complex and changeable than that in straight channels due to the effect of channel geometry.In this paper,various characteristics of detonation waves in annular channels were investigated experimentally and numerically.The cell structures of triple points trajectory of detonation waves and flame propagation time sequence diagrams were obtained by smoke trace technique and high-speed photography technique,respectively.The WENO scheme and Runge-Kutta were used to solve the Euler equation.The research work in this paper is mainly divided into the following three parts:?1?In this paper,the factors affecting the DDT process of direct ignition of premixed gas in annular channels were studied experimentally.The effects of the channel geometry,initial pressure of premixed gas and the type of premixed gas on DDT distance were discussed respectively.Compared the results obtained from cell structures with flame propagation time sequence diagrams,the same conclusions can be reached:the DDT distance in annular channels decreases with the increase of inner wall radius,initial pressure and premixed gas sensitivity.?2?In this paper,the stable propagation characteristics of 2H₂/O₂/3Ar premixed gas in annular channels were studied by experiments and numerical simulation.The experimental and numerical results mutually confirmed that the detonation wave intensity is most stable near the outer wall,and the propagation velocity and pressure fluctuation are small;the detonation velocity and pressure near the inner wall undergo periodic increase and decrease,which proves that the detonation intensity near the inner wall are enhanced and decayed periodically.By analyzing the propagation of triple points in numerical results,it can be found that triple points on the detonation front often disappear and appear,but the number of disappearance and appearance is basically similar,so that the number of triple points on the detonation front maintains a dynamic equilibrium,so as to maintain the stable propagation of the detonation.The comprehensive analysis of the position changes of triple points shows that the new triple points are mostly appeared near the outer wall,while the vanishing position of triple points is closer to inner wall.?3?In this paper,the unstable propagation modes of detonation in annular channels and straight channels were studied by experimental comparison.It was found that there are two modes of unstable detonation propagation in straight channels:stuttering detonation mode and galloping detonation mode.There are three modes of unstable detonation propagation in annular channels:detonation partial failure mode,single-head detonation mode and galloping detonation mode,which indicated that the unstable detonation propagation process in annular channels is more variable.This also proves that the propagation characteristics of detonation in annular channels are more complex.