The Study On The Visualization Of Pyrotechnic Combustion Flow Field And The Combustion Mechanism

Pyrotechnic composition is a non-uniform porous media made by mechanical mixing of combustible agent,oxidizing agent,adhesive and other powdered materials,severe burning reaction of pyrotechnic combustion makes gas,liquid droplets and solid particles coexist in the flame,so it is difficult for most pyrotechnic products to show the similar clear flame structure to that appeared during combustion of hydrocarbon fuels and propellants.Based on instruments of particle image velocity spectrometer(PIV),high speed camera(HSC),infrared temperature measurement equipment,etc.,the pyrotechnic composition combustion flame flow field and temperature field visualization were studied in this thesis,on the basis of the which,the combustion reaction mechanism of these kind of composite materials were studied.The particle size and concentration distributions of combustion particles in the combustion flame of pyrotechnics were studied.By using HSC,the whole process dynamic flow of discrete particles in the burning pyrotechnic flame was measured.By using intermittent high pressure jet of air sampling method,the one-dimensional particle size and concentration of burning particles in the combustion flame jet axis were analyzed by flame interception,thermal cardboard ablation,image processing.Particle size and concentration of particles in the axial direction of combustion flame jet were analyzed based on the standard particle calibration and parameter correction..The flame flow field and gas particle two-phase flow were studied.Based on the test results of PIV and HSC,the burning particle trajectory tracking model was established through image processing,threshold segmentation,particle grouping,edge detection,contour extraction means,etc.In addition,the burning particle concentration distribution,the velocity vector and the spatial position in the flame region were obtained through the multi resolution analysis pattern processing scheme according to the difficulty of particle identification in different brightness area.The three-dimensional space distribution of burning particles in the pyrotechnic flame was obtained through the burning particle velocity and flame flow field distribution rule.The temperature field distribution of combustion flame was studied.Based on the contribution of a large number of burning particles to the combustion flame temperature,through the use of a single burning particle radiation and heat transfer rule,the pyrotechnic flame temperature field was reconstructed based on the burning particles distribution,and the calculate results were verified by infrared thermometer.Summarizing the research of predecessors,the pyrotechnic combustion reaction mechanism was concluded based on the burning particles and further elaborated based on the characteristics of burning particles of application examples by heat and flame radiation application examples such as based on particle combustion of pyrotechnical combustion reaction mechanism.The thermal constants of non-uniform porous structure pyrotechnic compositions were measured by Hot Disk TPS2500S thermal constant analyzer and the empirical formulas were fitted.The relationship between the thermal constant of the pyrotechnic compostion and the combustion effect was discussed.According to the different radiation effects of pyrotechnic combustion flame,the mechanism of infrared decoy radiation effect and light extinction effect was analyzed.Based on a large number of combustion particles with high temperature burning particle effect,the combustion mechanism of the boundary layer,the particle flow field and the temperature field distribution of the combustion particles was studied.This study show that the pyrotechnic composition is a heterogeneous porous medium,the violent combustion reaction is inevitable to make a large number of composite particles and elemental metal particles into the combustion flame,the space distribution and combustion reaction rules of burning particles in the combustion flame fully embodies the pyrotechnic combustion reaction characteristics and plays a key role in the mechanism of pyrotechnic effects,such as the ignition ability,light radiation law etc.