Study On The Propagation Characteristics Of Detonation Wave In Multi-layer Bend Tube

The study of the detonation phenomenon has great practical significance in engineering.On the one hand,detonation-based engines have many advantages such as large thrust-weight ratio,high thermal efficiency,and low pollution.Therefore,they have a wide application background in aerospace field;on the other hand,detonation of combustible gas in industrial production often leads to huge disasters,which affect the safety of people’s lives and property.In this paper,The propagation mode and limit of the detonation wave were studied experimentally by using smoke film and high-speed camera.Moreover,the flame front image,velocity evolution and cell structure of detonation were obtained.The numerical simulating were performed to study the flow field of the detonation wave propagating in curved tube by solving the two-dimensional Euler equations with elementary reaction model.The 5th order WENO scheme was used to discretize the convection term,and ASIRK-2B was utilized to deal with the the stiffness caused by the chemical source.The main conclusions of this thesis can be described as follows:1.The initial pressure range corresponding to three propagation modes of detonation wave in bend tube was experimentally studied.When the inner radii decreases,the lower limit of the initial pressure of the stable propagation mode increases.2.The detonation limit was studied experimentally.R_i/λIs introduced as a sensitivity parameter to characterize the detonation limit.The detonation limit are found to be at the range of 2.6≤R_i/λ≤4.8 for C₂H₄+3O₂,CH₄+2O₂ and 2H₂+O₂+3Ar mixtures.3.The stable propagation of detonation wave in bend tube was studied.The detonation wave front maintains a fixed curved shape.The velocity distributions along the detonation surface are divided when the detonation propagates from straight tube to bend tube.However the angular velocity remains unchanged.The cell size gradually decreases from inside wall to outside wall in radial direction and remains constant in the circumferential direction.The pressure,temperature,OH and H₂ mass fraction of the flow field near the outer wall are higher than that near the inner wall.4.The critical propagation mode of detonation wave in bend tube was studied.The shape of the flame front is irregular and unstable,and the circumferential velocities of detonation wave show a large degree of oscillation.5.The unstable propagation mode of detonation wave in bend tube was studied.Three kinds of periodic detonation wave phenomena are obtained in the unstable propagation mode:（1）Partial extinction of the detonation wave near the inner wall.The cell structure near the inner wall undergoes cyclical changes of regeneration,decay,and local disappearance.The periodic angle decreases with the increase of initial pressure;（2）The galloping detonation phenomenon.The detonation fails completely and then re-generates.（3）Spinning detonation phenomenon like“petals”.The periodic angle which is independent of the initial pressure of premixed gases decreases with the increase of the inner wall radius.