Influences of the heating rate and rheological properties on slow cook-off response of composition B
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摘要: 为探究慢速烤燃过程中不同升温速率下B炸药流变特性的尺寸效应对相变后内部温度场的分布特征与点火位置的影响,设计了
$\varnothing $ 76 mm与$\varnothing $ 130 mm两种尺寸的烤燃弹。通过慢烤试验分别获得了1 ℃/min与3.3 ℃/h两种升温速率下,各烤燃弹内部监测点的温度变化曲线,结合数值模拟进一步分析了各工况下烤燃弹内部温度场的变化特点。研究结果表明:在升温速率为1 ℃/min时,两种尺寸的烤燃弹在炸药还未完全相变前就已发生响应,对流的存在导致炸药顶部的熔化速率明显高于底部,B炸药流变特性的尺寸效应不明显;当升温速率为3.3 ℃/h时,相变完成后,尺寸偏小的烤燃弹内部流场强度低,温度场变化十分缓慢,而尺寸偏大的烤燃弹内部流场强度较大,温度场很快体现出典型的液相温度场分布特征,B炸药的流变特性具有明显的尺寸效应;无论升温速率的快慢与尺寸的大小,炸药发生相变后温度最高点、自热反应区域与最终响应区域都出现在药柱顶部附近。Abstract: In order to investigate the difference of internal temperature distribution and the location of response in slow cook off of Comp B with consideration about the rheology and its size-effect when under different heating rates, 2 types of cooking off bombs with diameters of 76 mm and 130 mm were designed. The temperature curves of the internal monitoring points in the bombs at the heating rates of 1 ℃/min and 3.3 ℃/h were obtained by the slow cook off test, and the characteristics of temperature field under various conditions were further analyzed in simulation. The results show that: at the heating rate of 1 ℃/min, the internal explosives of the 2 sizes of bombs have already responded before they have completely melted, affected by the convection, the explosive of the top melted significantly quicker than that of the bottom, size effect on the rheology was not obvious; When the heating rate is 3.3 ℃/h, after the phase changing is completely done, the intensity of internal flow field is low, and the temperature field of the smaller bomb changed very slowly. However, the internal temperature field in the larger bomb changed quickly to a typical liquid temperature field because of an intenser flow, size effect on the rheology was more palpable. Moreover, in any conditions, the highest temperature location, self-heating and response areas are all near the top of the explosive.-
Key words:
- Comp B /
- slow cook-off /
- rheological behavior /
- heating rate
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表 1 烤燃弹具体尺寸
Table 1. Size of the cook off bombs
方案编号 弹体直径/mm 弹体长度/mm 弹体壁厚/mm 药柱直径/mm 药柱长度/mm 测点间距/mm 1 130 430 15 100 400 50 2 76 255 7.5 61 240 30 表 2 响应时刻各测点温度
Table 2. Temperature of each measuring points when ignition
弹径/mm 升温速率 温度/℃ 外壁 测点1 测点2 测点3 测点4 测点5 测点6 测点7 76 1 ℃/min 194.2 127.4 82.9 78.7 78.3 78.2 78.3 (失效) 3.3 ℃/h 171.8 227.6 205.2 201.4 193.4 (失效) 190.2 184.1 130 1 ℃/min 193.8 79.3 66.2 65.3 64.9 64.5 64.3 64.5 3.3 ℃/h 175.1 191.1 187.3 185.4 182.8 179.5 176.7 175.3 表 3 B炸药与壳体的物性参数
Table 3. Physical parameters for Comp B and shell
材料 ρ/(kg·m−3) C/(J·kg−1) k/(W·m−1·K−1) Qm/(J·kg−1) Ts/℃ Tl/℃ B炸药 $\left\{ {\begin{array}{*{20}{l}} {1\;690}&{(T {\simfont\text{≤}} {T_s})} \\ {1\;690 - 0.675\left( {T - {T_{\rm{s}}}} \right)}&{(T {\simfont\text{>}} {T_{\rm{s}}})} \end{array}} \right.$ 1 126 $\left\{ {\begin{array}{*{20}{l}} {0.17}&{(T {\simfont\text{<}} {T_{\rm{s}}})} \\ {0.17 - 0.025\left( {T - {T_{\rm{m}}}} \right)}&{({T_{\rm{s}}} {\simfont\text{≤}} T {\simfont\text{≤}} {T_{\rm{l}}})} \\ {0.15}&{(T {\simfont\text{>}} {T_{\rm{l}}})} \end{array}} \right.$ 128 000 80 82 45钢 7850 475 14 − − − 注:ρ为密度;C为比热容;k为导热系数;Qm为熔化热;Ts为相变起始温度;T1为相变结束温度。 表 4 B炸药化学反应动力学参数
Table 4. Chemical kinetic parameters for Comp B
Ea/(J·mol−1) Q/(J·kg−1) A 22 000 5.82×106 2.01×1018 表 5 试验与数值模拟响应温度的比较
Table 5. Comparison of response temperatures from experiment and simulation
弹体直径/mm 升温速率 响应温度/℃ 误差/% 试验 数值模拟 76 1 ℃/min 194.2 195.0 0.4 3.3 ℃/h 171.8 172.4 0.3 130 1 ℃/min 193.8 193.7 −0.05 3.3 ℃/h 175.1 174.6 −0.3 -
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