碰撞和冲击作用下炸药颗粒燃烧反应特性研究

Formation、growth、combustion and reaction of hot spots at the granular scale are the key points to understand the shock initiation of heterogeneous explosives. Deep and meticulous investigation of this problem could deepen people's understanding about shock initiation of explosives at the granular scale, and provide foundations for establishing macroscale model of shock initiation based on the real processes. These investigations have very important scientific significance on the safety evaluation and practical application of explosives. In this project discrete element numerical method as well as experimental method (by impact and dropweight experiment) will both be used to systematicly investigate the combustion and reaction of granular explosives under impact and shock loading. First we will establish and perfect the discrete element method which could deal with gases and solids simultaneously, that is to say, it can calculate the reaction of explosives. Then the influences of crystaline quality、size and geometry shape of explosive granule、loading conditions etc. on the results of combustion and reaction of explosives will be investigated by discrete element method and compared to the experimental results.

颗粒尺度下炸药热点的形成、长大以及燃烧反应过程是理解非均质炸药冲击起爆的关键，对这一问题深入细致的研究可以加深人们从颗粒尺度对炸药冲击起爆规律的认识，为构建更符合实际过程的宏观起爆模型提供依据，对炸药安全评估和实际应用也具有重要的科学意义。本项目拟同时采用离散元数值方法和实验方法（飞片撞击和落锤实验）对颗粒炸药在碰撞和冲击作用下的燃烧和反应过程进行较为系统的研究。首先建立和完善气-固两相流耦合反应流动计算的离散元模拟方法，然后模拟研究炸药晶体品质、炸药颗粒尺寸和几何形状、加载条件等因素对燃烧反应结果的影响并与实验结果进行对比。

本项目在离散元方法中增加了内聚力断裂模型和热传导模型，并建立了气—固两相流耦合的离散元模拟方法，结合Arrhenius反应速率模型对冲击作用下HMX颗粒炸药的燃烧反应特性进行了数值模拟，分别研究了冲击波强度、颗粒尺寸和粘结剂的影响，结果表明：冲击波强度越高，炸药的燃烧反应越剧烈；颗粒尺寸越小其响应行为越接近均质炸药，较大的颗粒尺寸能够造成局部剧烈的燃烧反应；粘结剂具有缓冲作用，导致PBX炸药受到同样强度的冲击加载时，温升低于HMX颗粒炸药，反应质量分数也明显小于HMX颗粒炸药。用改进的落锤实验装置研究了落锤下落高度、颗粒尺寸和颗粒堆积程度对HMX晶体颗粒低速撞击响应过程的影响，结果表明：随落锤下落高度增加，颗粒炸药更容易发生点火燃烧；其他实验条件相同的情况下，颗粒尺寸越大越容易发生点火反应；颗粒堆积越紧密，塑性变形时间越长，反应持续时间越短。对HMX为基的粘结炸药（PBX）开展了落锤撞击实验，结果再次揭示了这样一个规律，即：非均匀炸药在低压长脉冲加载下基本都要经历压实——塑性扩展——颗粒破碎——形成热点——点火——燃烧——熄灭的典型非冲击点火过程。但无论是颗粒炸药还是高聚物粘接炸药，低速撞击下其点火发生的位置都偏离样品中心一定距离。本项目的研究结果能够加深对非均质炸药非冲击点火过程的认识，对武器装药安全评估和实际应用也具有重要的科学意义。