Experimental Research Of Combustion Stability Of Delay Element Of Civil Millisecond Detonator

The millisecond delay detonators are widely used in various economic construction fields such as metallurgy,coal,building materials,water conservancy and hydropower,transportation,nuclear industry,urban construction and so on.With the development of the new technology of engineering blasting,puting forward higher requirements on the delay reliability of delay detonator.At present,there is still a big gap between the delay precision of domestic pyrotechnic delay element and foreign products,and it needs to be further improved.This paper mainly discussed the influence of the ignition mode,the chamber length and the indoor temperature and pressure conditions on the stability of the millisecond delay element.The experiment designed a special mould,simulating the state of delay element in detonator,and using high speed camera recorded delay times of each explosive core of delay elements;Gas chamber pressure and peak temperature were measured respectively by piezoelectric pressure sensor and micro thermocouple;Each explosive core was treated as a separate delay element,and calculating the standard deviation of delay time of the medicine core.Experiment results showed:(1)Through high speed photography,it can be clearly observed that:The delay element was ignited by the nonel denonator,there were a small number of burning delay particles are ejected from the ignition end.The ejected particles can be considered as the first layer of the laminar combustion product formed by the pulsatile combustion of the delayed explosive.(2)Under the same conditions,comparing with nonel denonator,the delay time of fusehead ignition was shorter,the change of the chamber length has no significant effect on the delay time.Using the method of significance test analysis:The ignition of the electric firing head,chamber length from 12mm increased to 20mm,the delay time of the 2 segment and 4 segment delay element was increased.(3)The gas chamber pressure of 2 segment delay element was in the range of 0.5-2.5MPa,and 4 segment was in the range of 0.5-3.OMPa,burning rate and pressure were showed a good linear relationship between burning rate and pressure;The burning rate of the two kinds of delay elements increased with the increase of the peak temperature of the chamber.The effect of pressure on the burning rate was dominant due to the rapid disappearance of the preheating effect.(4)Through theoretical analysis,ignition of micro gas delay composition was a gas phase ignition process,delay time shortened with the increase of gas chamber pressure and temperature.(5)Taking the explosive core as the research unit,calculating the standard deviation of the delay time for all each explosive core of delay element.It was found that there was no obvious relationship between the standard deviation of the delay time and the pressure and temperature in the chamber,indicating that at the same situation,the main reason for the delay precision was not the pressure and temperature in the chamber,but delay element itself factors.