摘要
为研究RB‑2X(2,4‑二硝基苯甲醚(DNAN)/奥克托今(HMX)/铝(Al)/黏结剂)和RM‑2X(DNAN/HMX/3‑硝基‑1,2,4‑三唑‑5‑酮(NTO)/Al/黏结剂)两种新型DNAN基含铝炸药热响应特性,开展RB‑2X炸药在1.0 K·mi
图文摘要
The small‑scale cook‑off experiments and simulations were carried out for RB‑2X and RM‑2X explosives. The air gap effect formed by cooling and contraction of fused cast explosive was analyzed. The thermal‑ignition response of large‑scale cook‑off bomb was also predicted.
关键词
发展钝感炸药是世界各国弹药发展的重点,是世界弹药发展过程的必然结
国外针对DNAN炸药研究较早,但主要面向研制钝感炸药配
目前国内对新型DNAN基熔铸炸药研究依旧很少,本研究通过对新型DNAN基含铝炸药RB‑2X和RM‑2X进行慢速烤燃实验和数值模拟,分析炸药在不同条件下的热响应特性;在慢速烤燃实验中,熔铸炸药会因冷却收缩从而与壁面形成空气间隙,以往在数值模拟中却没有考虑空气间隙的影响,因此本研究通过模拟分析空气间隙效应;预测装填RM‑2X大尺寸弹药在不同热刺激条件下的热响应特性,为研发新型DNAN基炸药提供依据。
炸药的热刺激响应实验一般采用小型烤燃实验装置,

图1 小型烤燃弹实验装置简图
Fig.1 Structural diagram of small‑scale cook‑off bomb setup

图2 小型烤燃实验装置实物图
Fig.2 Photo of small‑scale cook‑off setup
烤燃实验虽能得到预设监测点温度‑时间关系和炸药点火时间等数据,但是不能获取不同时刻炸药熔化液相分布、炸药温度场等数据。由于RB‑2X和RM‑2X均为混合炸药,因此采用多组元网格单元方
根据小型烤燃实验装置,建立炸药烤燃三维计算模型

图3 小型烤燃弹计算模型
Fig.3 Computational model of small‑scale cook‑off bomb
为预测热刺激下装填RM‑2X大尺寸弹药响应规律,基于弹药的实际尺寸和装药结构,建立四分之一简化计算模型如

图4 大尺寸弹药简化计算模型
Fig.4 Simplified computational mode of large‑scale bomb
炸药烤燃过程中,炸药的能量、质量、动量运输方程采用如下通用形式表
(1) |
式中,t为时间,s;ρ为密度,kg∙
对于空气域部分,则采用P1辐射模型,对于辐射流qr,采用下述方程计
(2) |
式中,α为吸收系数,
两种炸药均为混合炸药,主要组分有DNAN、HMX、NTO和Al粉。对于HMX,其烤燃过程中首先吸收热量发生β‑HMX→δ‑HMX晶型转变,之后随加热进程δ‑HMX发生分解反应并生成最终产物,因此HMX热分解过程采用四步反应动力学模型描
反应1 β‑HMX↔δ‑HMX (一阶吸热反应)
反应2 β‑HMX+δ‑HMX→δ‑HMX (双分子吸热反应)
反应3 δ‑HMX→产物 (一阶吸热反应)
反应4 δ‑HMX+产物→产物 (双分子放热反应)
各反应过程所使用的反应速率方程为:
(3) |
(4) |
(5) |
(6) |
HMX单位时间内热分解反应生成的热量为:
(7) |
式中,k为玻尔兹曼常数,1.380649×1
DNAN熔点约366 K,低于3次实验爆炸时刻的最低中心温度464.35 K,因此在加热过程中会吸热熔化,由固相转变为液相,随温度升高发生分解反应生成产物,用液相分数来表示液态物质在单元中的容积比,当单元中材料仍为固体时,液相分数为0;完全熔化成液体时,液相分数为1,采用单步反应动力学模型描述DNAN分解反
DNAN→产物, | (8) |
DNAN单位时间内热分解反应生成的热量为:
(9) |
对于NTO炸药,采用单步反应动力学模型描述其热反应过
NTO→产物, | (10) |
NTO单位时间内热分解反应生成的热量为:
(11) |
式中,rx为反应速率,
在烤燃实验中Al粉不能受热分解,不参与烤燃过程中的化学反应,采用量纲分析方法,选取与温度有关的物性参数热传导系数和比热容、密度、铝粉的细观特征长度为基本量来度量Al粉源项,假设Al粉各物性参数不随温度变化,则Al粉作为定常吸热源
(12) |
式中,a为标定参数;λ为热传导系数,W∙
Note: ρ is density, Cv is heat capacity, λ is thermal conductivity.
Note: a is calibration parameter, λ is thermal conductivity,Cv is heat capacity, ρ is density, l is characteristic length.
Note: Z is pre‑exponential factor, Sf is forward activation entropy, Ef is forward activation energy,Sr is reverse activation entropy, Er is reverse activation energy, Q is heat of reaction.
Note: Z is pre‑exponential factor, E is activation energy, Q is heat of reaction.
对于混合炸药,各个单元在热分解反应过程中产生的总热量为各组分与其质量分数乘积之
3发实验后烤燃弹照片如

a. RB‑2X(1.0 K·mi

b. RM‑2X(1.0 K·mi

c. RM‑2X(0.5 K·mi
图5 点火后烤燃弹照片
Fig.5 Photo of cook‑off bomb after ignition

图6 实验和计算RB‑2X炸药中心温度‑时间曲线(1.0 K·mi
Fig.6 Temperature‑time curves of RB‑2X explosive at the center point from experiment and calculation (1.0 K·mi

图7 实验和计算RM‑2X炸药中心温度‑时间曲线(1.0 K·mi
Fig.7 Temperature‑time curves of RM‑2X explosive at the center point from experiment and calculation (1.0 K·mi

图8 实验和计算RM‑2X炸药中心温度‑时间曲线(0.5 K·mi
Fig.8 Temperature‑time curves of RM‑2X explosive at the center point from experiment and calculation (0.5 K·mi
Note: tc is temperature at the center point.

图9 RM‑2X炸药不同时刻液相分数分布(1.0 K·mi
Fig.9 Liquid phase fraction distribution of RM‑2X explosive at different times (1.0 K·mi

图10 RM‑2X炸药不同时刻温度分布(1.0 K·mi
Fig.10 Temperature distribution of RM‑2X explosive at different times (1.0 K·mi
为研究熔铸炸药冷缩产生的空气间隙对烤燃模拟过程的影响规律,在计算模型中将空气间隙设为0,0.1,0.2,0.3,0.4,0.5,0.75 mm和1 mm,炸药为RM‑2X炸药,加热速率为1.0 K·mi
定义延迟时间为有空气间隙与无空气间隙计算点火时间的差值。

图11 延迟时间与空气间隙宽度关系图
Fig.11 Relation between delay time and air gap width

图12 大尺寸弹药中心温度‑时间曲线(1.0 K·mi
Fig.12 Temperature‑time curves at center point of large‑scale bomb (1.0 K·mi
Note: tc is temperature at the center point.
(1)对RB‑2X和RM‑2X炸药进行烤燃实验的结果显示RB‑2X炸药在加热速率1.0 K·mi
(2)对RB‑2X和RM‑2X炸药烤燃实验进行了数值模拟,结果表明,计算获得的温升曲线与实验结果吻合较好,RB‑2X炸药点火时间与实验值偏差为1.13%,RM‑2X炸药点火时间最大偏差为5.63%,证实所建烤燃模型合理。
(3)模拟了熔铸炸药壳体壁面与炸药之间的空气间隙对炸药响应时间的影响,计算结果表明爆炸延迟时间随空气间隙宽度增大而缓慢增大;当空气间隙扩大到0.75 mm后,延迟时间稳定在90 s。因此在烤燃实验装药过程中应尽量减小空气间隙的宽度,降低空气间隙效应的影响。
(4)对装填RM‑2X大尺寸弹药的烤燃特性进行了模拟预测,结果表明随弹药尺寸增大和加热速率增大,炸药点火时中心温度会有明显降低;当加热速率从1.0 K·mi
致谢
感谢北京理工大学陈朗教授团队为本文小型烤燃弹实验提供帮助,在此深表感谢!
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