Study On The Influence Of Cross-section Expansion On The Detonation Process Of Pulse Detonation Engine

Pulse detonation engine is one of the new type of propulsion power plant in 21st century.Compared w:ith the conventional aeroengine,pulse detonation engine has a lot of obvious advantages such as high burning efficiency,simple structure,and high specific impulse.But the structure optimization of pulse detonation engine and the improvement of the thrust still is an urgent problem to solve in engineering.In this dissertation,theoretical and experimental investigations about the sudden expansion of section to pulse detonation engine were conducted.The method of two-dimensional viscous CE/SE was employed to simulate the gasoline/air interior flow field of the detonation wave entering from the small-diameter pipe into the suddenly expanding large-diameter pipe.At the same time,the experimental platform about the sudden expansion of section was built and the experimental study was carried out.The main contents and conclusions are as following:(1)A mathematical model of multiphase detonation about the sudden expansion of section to pulse detonation engine has been established.The two-dimensional viscous CE/SE method is derived to solve the equations and simulate the gasoline/air interior flow field of the detonation wave entering from the small-diameter pipe into the suddenly expanding large-diameter pipe.The results of numerical calculation show that the detonation wave will produce a vortex at the location of the turning point when it enters the suddenly expanding pipe.And the formation of Mach reflection will lead to the formation of high temperature and high pressure area which makes the spherical wave front smooth.At the same time,Steady detonation wave will form again.(2)The detonation wave in expanding pipe of different strctures and ignition parameter is studied.The results of numerical calculation show that,if the diameter is larger,the position of Mach stem will be later and the pressure will be higher.The changes of the ignition intensity will shorten the DDT time effectively and have less effect on the position of Mach stem and the size of pressure.The increase of the length to the small detonation pipe has no effect on DDT distance in the suddenly expanding pipe.The increases of the initial droplet cause the peak pressure to increase and then decrease.The DDT time and distance also increase in the suddenly expanding pipe.(3)The sealing property and thee strength of detonation tube and flange meet the requirements.Then,the experimental platform about the sudden expansion of section was built to study the propagation characteristics of detonation wave in the suddenly expanding pipe and the experimental study was carried out.The results show that the propagation characteristics of the detonation wave entering into the suddenly expanding pipe have the same results as the numerical simulation.The changes of filling degree have large effects on overdrive detonation,the attenuation and formation process in the suddenly expanding pipe.