Study on the Properties of Shock Wave from Aluminized Explosives Blast in Air

Author:Duan Xiao Zuo

Supervisor:xu geng guang jiao qing jie zhang qing ming

Database:Doctor

Degree Year:2017

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Pages:136

Size:5114K

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Aluminized explosive has been widely used in air blast for the good performance as gens of mixed explosives.In view of the non-ideal properties in the explosion process of aluminized explosive and the complexities of the effects of size and content of aluminum powder,confined space and so on,experiments,theory analysis were used as basic,combined with simulation in this study to identify the properties of shock wave in different aluminum powder size,content and confined space.The main contents are as follows:(1)Experiments of air blast from 10 kg aluminized explosives containing 0%40%aluminum powder were used to gain the ground reflection shock wave parameters at different locations,3 m to 12 m far from the horizontal projection point of explosion center.The overpressures and impulses at the same location increased first and decreased later along with the increase of aluminum content.For the overpressure,it gained max when aluminum content was 20%within 9m.In 12 m,it gained max when aluminum content was 30%.In the location of 3 m,4 m,5 m and 9 m from the projection of explosion center,the sample containing 30%aluminum powder had the max impulse.Within the test scope,the sample containing 30%aluminum powder had the max positive pressure time.(2)In order to comparing the transmission attenuation characteristics of the shock wave from aluminized explosive,similarity relation of polynomial form and power exponent form were fitted of the ground reflection shock wave parameters vs scaled distance.It has seen that the power exponent form contained higher correlation,which means the reflected shock wave parameters from aluminized explosives met the similarity law in power exponent form.At the same time,there are only two fitting parameters,which would be easier to build relationships with other physical quantities.(3)Experiments of confined explosion from aluminized explosives containing 25%or40%size of 50 nm,5μm or 50μm aluminum,and containing 15%45%size of 50μm aluminum,were conducted.Method of multipoint averaging noise reduction to gain quasi static pressure,and method of exponential attenuation approximation for attenuation coefficient of pressure was raised.Three parameters of quasi-static pressure,pQS,rise time of pressure,tQSS and the attenuation rate,ω,were used to represent the interaction parameters of shock wave.(4)For the same alumum content(25%or 40%),pQSS or tQS decreased along with thedecrease of aluminum size,andωdecreased along with the increase of aluminum size.For the same aluminum size,the sample containing 40%aluminum gained the higher values of pQSS and tQS and the lowerω.The tested results of the aluminized explosives containing 15%45%aluminum showed that,with the increase of aluminum,pQSS increased first and decreased later,tQS increased persistently andωdecreased first and increased later.The formula containing 40%aluminum gained the max pQSS and the leastω.(5)The shock wave propagation in air blast from three explosives,HL0,HL15 and HL30 were simulated.Results showed that:in the distance from the ground level of 2.5 m to 6 m,at the same for any explosives,the third wave point height increases with the increase of the horizontal distance.For HL30,point-of-three-waves were higher when burst height was 1 m than that of 1.5 m and 2 m.The calculated pressure histories were in good accordance with the tested histories,which explained that the numerical simulation perform well in simulating the ground reflection shock wave of aluminized explosive.(6)The simulated results of confined explosion from four explosives,TNT,HL0,HL15 and HL30 showed that the adding the complete afterburning energy(the complete combustion energy minus the detonation heat)in JWL EOS could performed well.The simulated results had less than 2%error compared with the tested results.For the same V/W,(volume of chamber/weight of charge)geometry symmetry of tank affected the initial blast process and rise time of pressure mainly and the quasi static pressure less.Both the quasi static pressure and rise time of pressure decreased with the increase of V/W.