Experimental Research On Impact Of Inert Gas On Detonation Propagation Under Perturbation

The flammable gas leaked in industrial production will explode once ignition source is encountered and detonation will accelerate under the initial conditions and boundary conditions.The high pressure produced by detonation will seriously threaten the safety of industrial production,so it is particularly important to study suppression characteristic of detonation wave propagation.Based on this,the detonation propagation velocity,cell structure and dynamic parameters of flame propagation are obtained by means of gaseous detonation experimental setup.The flammable gas is isolated from the inert gas in the tube,and the effect of the inert gas on the detonation wave suppression is obtained by combining the experimental study with the mechanism analysis.The main work and conclusions are as follows:（1）By changing the initial pressure and the concentration of argon in the gas mixture,the propagation of detonation wave without disturbance is experimentally studied.The results show that there are three propagation modes of steady state,fast fluctuation and failure mode with the decrease of initial pressure.The cell size of detonation wave decreases with the increase of initial pressure.The cell structure of the unsteady gas is irregular,the tripe point trajectory is connected with a line,the steady state gas cell structure is regular.（2）The effect of polypropylene film as a flexible obstacle on the propagation characteristics of detonation wave is studied experimentally.For the single PET obstacle,there are different propagation modes（velocity loss and detonation failure）with the number of layers increasing after the detonation wave passes through the flexible obstacle.As the number of layers increases,the leading shock wave increases in the opposite direction and the diameter of the detonation wave decreases gradually.With the further reduction of the caliber,the incident wave of detonation wave can not reach the rigid wall after the incident wave passes through the obstacle,so it can not quickly form the Maher reaction which causes the detonation wave to fail.（3）When the detonation wave passes through a flexible obstacle,there are two ways（a）when the maximum static pressure of the obstacle is far less than the physical overpressure produced under this initial condition.When the detonation wave passes through the obstacle,the maximum static pressure of the barrier is far closer or slightly greater than the pressure impact of the preamble shock wave（b）.When the physical overpressure is produced under this initial condition,the detonation wave rigid can not be damaged by the overpressure impact of the lead shock wave when it reaches the front end of the obstacle,and can only be deformed.At this time,the high temperature and high pressure of the reaction zone compels the material properties to change and then break up when the flame is gathered at the front end of the obstacle.（4）The experiment has been completed the propagation law of detonation wave passing through inert gas with different lengths and once again entering the diluted combustible gas with different argon.The results show that the detonation wave has 6 stages:first deceleration section,second deceleration section,third deceleration section,acceleration section,overdrive detonation section and steady state section in the whole propagation process.When passing through the length of 800 mm CO₂ and C₃F₇H inert gas section,it is possible to enter detonation wave instantaneously into the combustible gas.When the distance of the inert gas increases to1200 mm,the detonation wave is still formed after the CO₂ inert gas,only the distance between the deflagration and detonation increases,and the detonation wave can not be formed in the limited distance after the C₃F₇H inert gas.It shows that the inhibitory effect of C₃F₇H on the detonation propagation is obvious.（5）The experimental results and theoretical analysis are used to obtain the shock wave degradation mechanism of a detonation wave passing through an inert gas cluster into a combustible mixture.When the detonation wave passes through the flexible obstacle into the inert gas section,the high calorie chemical reaction will be terminated.The detonation wave is transmitted at the gas interface and degenerates into the motion shock wave.The main reason for the attenuation of the transmission shock wave is the discontinuation of the exothermic reaction.The main inhibition effect of CO₂ on flame propagation is the process of cooling and dilution,and the main inhibition effects of seven fluoro propane on the flame are the thermal decomposition of the seven fluoro propane,the cooling of active free radical,the binding process of the inert free radical and the active free radical.