Detonation Limit Of Pre-mixed Mixtures And Characterization On Spinnign Detonation Cellular Structure

Detonation is a kind of strong combustion phenomenon,the detonation wave impacts the unreacted gas,generate detonation chemical reaction,form a high-temperature and high-pressure zone,and releases a large amount of energy.The explosion phenomenon brings a large number of casualties,property losses and environmental damage.In order to study the explosion suppression and explosion protection,the detonation limit and the characterization of detonation cellular structure were studied.In this paper,a modified model of acoustic theory was constructed,and the detonation experiments were carried out with multiple conditions and components.On the basis of the linear acoustics theory,the adiabatic compression on unreacted gas by the leading shock wave is discussed.Also,the thermodynamic state of unreacted gas before and after the adiabatic compression is analyzed,and the modified parameters are deduced as well as the cellular structure model is constructed.In this paper,a detonation experiment system was built,and a number of groups of pre-mixed mixture were selected to for experiments under different tubes.The detonation wave velocity was measured,the velocity fluctuation was calculated,and the low-frequency and high-frequency spinning detonation cellular structure were recorded.According to the experimental results,the control factors of detonation failure are discussed.The detonation wave velocity of C2H2+O2,C2H2+2.5O2 and C2H2+2.5O2+70%Ar decreased to 65%vCJ,and the velocity fluctuation was ?=50%.Cellular structure is an essential factor for self-sustained detonation.The detonation fails when it is devoid of cellular structure.The cell structure analysis and cell size measurement of the inner and outer walls of the annular channel were carried out,and the expression between cell size and initial pressure was discussed.According to the experimental results of low-frequency spinning detonation,the ratio of tube diameter-pitch and the Angle between the trajectory and the tube axis are calculated.The maximum error between the experimental and theoretical values of 2H2+O2+3Ar,CH4+2O2,C2H2+5N2O and C2H2+2.5O2+85%Ar is 8.8%and 8.7%.The experiment results agree with the cellular structure model.For high-frequency spinning detonation,trajectories on smoked foils were processed and traced by Photoshop,then,a MATLAB program was carried out on that traced-tajectory picture to analyze and recognize cellular structure.A series of parameters were extracted from end-on results of high-frequency spinning detonation,such as the cell number,cell area,and the angle between triple-points on the same diameter and the distance between cell center.Next,a formula was deduced to describe the instability of pre-mixed mixture on the end-on cellular structure.In this study,the control factors of detonation failure for per-mixed mixtures in tube are obtained,the kinetic model of spinning detonation cellular stucture is constructed,and the structure characteristics of low-frequency spinning detonation cell are described.Through experimental study,the control mechanism of cellular structure in detonation self-sustaining propagation is revealed,and the relationship between cell size and initial pressure in annular tube and outer wall is obtained.The analysis method of high frequency spinning detonation is presented,the influence of boundary layer effect on the end face structure is studied,and the relationship between the end face structure of high frequency spiral detonation and the per-mixed mixtures instability is revealed.