金属蒸汽中的激光维持爆震波

 应用我们发展的一个激光与金属蒸汽相互作用的简化物理模型对激光维持爆震波的点火激励、传播规律作了数值研究并取得了较好的结果。计算得到的LSD波阈值与激光脉宽的关系表现出典型的幂规律I_th∝τ^-1/2。此外，还得到了一些关于LSD波屏蔽效应的有益结果。在LSD波充分发展的阶段，LSD波阵面的光学厚度可达5~10的量级，这表明LSD波具有很强的屏蔽作用。     

叠氮化铅的等离子体电子作用机理初探

本文分析了装有不同药剂的半导体桥（Semiconductor Bridge,SCB）火工品的电流信号,结合叠氮化铅（Lead Azide,LA）的铅核反应机理,探索性地分析了等离子体中电子对药剂分解反应的影响.表明SCB等离子体中的电子可能直接参与铅核的生成反应,使Pb²⁺/Pb⁰转化变得容易,实现6.89μs的发火.     

悬浮RDX炸药粉尘爆轰的数值模拟

用两相流模型对悬浮RDX炸药粉尘爆轰波进行了数值模拟。RDX炸药颗粒在爆轰波阵面后的高温高速气流中加速并升温,颗粒表面发生熔化。参考液滴在高速气流作用下剥离的效应,假设炸药熔化部分在高速气流的作用下发生剥离,破碎成极小的颗粒,瞬时发生分解反应,释放出能量支持爆轰波传播。数值模拟了在不同粒径和浓度的悬浮RDX炸药粉尘中爆轰波的发展与传播过程,得到了爆轰波流场中气-固两相的物理量分布,并确定了爆轰波参数。在较低的RDX粉尘浓度条件下,爆轰波阵面压力的峰值曲线出现振荡。当RDX粉尘浓度在80~150 g/m3时,数值模拟得到的爆轰波阵面压力峰值曲线的振荡是规则的;当RDX粉尘浓度为70 g/m3时,爆轰波阵面压力峰值曲线出现不规则振荡。     

Spontaneous ignition of ultra-fine magnesium powder without an original oxide coat at room temperature in O2/N2 mixture streams

To examine the pyrophoric characteristics of Mg powder, we generated ultra-fine Mg particles (average particle diameter: about 0.3 μm) without an original oxide coat in an Ar stream. The ignition of the powder was measured by using the impinging O₂/N₂ mixture streams over a wide range of the experimental parameters: pressure, oxygen concentration and velocity of the streams. The Mg powder was found to ignite even at room temperature. The spontaneous ignition temperatures in the range of 278  324 K were insensitive to all the experimental parameters. The ignition delay time had a tendency to decrease with increasing experimental parameters.The ignition process of the Mg powder was found to be controlled by the surface reaction rate without an oxide coat. We proposed a new ignition hypothesis considering a critical oxide thickness on the Mg powder particles at the transition temperature from protective to non-protective nature: that is, the ignition of the Mg powder occurs when the powder temperature rises above the transition temperature before surface reactions form a protective oxide coat with the critical thickness on the individual particle surfaces. According to this hypothesis, an ignition model of Mg powder cluster was developed, and the relation between the spontaneous critical ignition temperature and the ultra-fine powder size, depending on the critical thickness of the protective oxide coat, was clarified. The critical oxide thickness was estimated.     

激光脉冲参数对冲击点火的影响

针对激光脉冲参数对冲击点火的影响进行理论分析和数值模拟.首先从冲击波的产生和碰撞过程出发,理论分析冲击脉冲峰值功率、脉宽和上升沿时间对点火的影响;然后通过数值模拟,以点火时间窗口作为评价标准,验证理论分析结果.研究表明:冲击脉冲峰值功率是点火成败的关键因素之一,脉冲宽度则需达到百皮秒以提供足够的点火能量,上升沿时间在小于600 ps的情况下不会对点火造成明显影响. 关键词： 冲击点火 激光冲击脉冲 点火时间窗口     

Detailed investigation of ignition by hot gas jets

Experimental and numerical investigations of the ignition of hydrogen/air mixtures by jets of hot exhaust gases are reported. An experimental realisation of such an ignition process, where a jet of hot exhaust gas impinges through a narrow nozzle into a quiescent hydrogen/air mixture, possibly initiating ignition and combustion, is studied. High-speed laser-induced fluorescence (LIF) image sequences of the hydroxyl radical (OH) and laser Schlieren methods are used to gain information about the spatial and temporal evolution of the ignition process. Recording temporally resolved pressure traces yields information about ambient conditions for the process. Numerical experiments are performed that allow linking these observables to certain characteristic states of the gas mixture. The outcome of numerical modelling and experiments indicates the important influence of the hot jet temperature and speed of mixing between the hot and cold gases on the ignition process. The results show the quenching of the flame inside the nozzle and the subsequent ignition of the mixture by the hot exhaust jet. These detailed examinations of the ignition process improve the knowledge concerning flame transmission out of electrical equipment of the type of protection flameproof enclosure.     

双破片同时撞击对B炸药冲击起爆的数值模拟研究

 采用Lee-Tarver点火增长模型对单钨珠撞击带壳B炸药的过程进行了计算,所得到的不同尺寸钨珠引爆炸药的阈值速度与实验结果吻合良好。数值模拟了双钨珠同时撞击带壳B炸药的过程,计算了破片引爆炸药的阈值速度,分析了炸药的点火增长过程。结果表明：双破片同时撞击炸药时,引爆阈值速度随着破片间距的增大呈抛物线规律增大;当破片间距较大且撞击速度略高于阈值速度、双破片同时撞击时,炸药内部爆轰波的初始形态随破片速度而变化。     

高功率脉冲激光对阶跃折射率多模光纤损伤机理

 理论分析和模拟仿真研究了激光点火系统中光纤端面损伤、光纤初始输入段损伤和光纤内部损伤机理。结果显示：端面损伤主要是由光纤端面的杂质和缺陷引起；光纤初始输入段损伤是由光束的初次反射造成光纤局部激光能量密度增大引起的；光纤内部体损伤主要由于激光自聚焦效应引起损伤和光纤受到的意外应力产生微小碎片，吸收激光能量，引起光纤局部损伤。给出了激光点火系统中提高光纤损伤阈值的一般方法，主要包括光纤端面处理、设计合理的激光注入耦合装置。     

激光点火系统上位模拟器研究

激光器件的优良性能大大提升了它在武器系统中的应用前景。上位模拟器是模拟武器系统对激光点火系统实施指令的控制单元,通过上位模拟器的操作可以实现对激光点火系统的远程控制。上位模拟器的研究是基于硬件和控制软件的,具备有发火控制、保险与解除保险控制、通讯、温度检测与背向光检测等多种控制功能。上位模拟器的研究为激光点火系统在武器系统中的实际应用奠定了良好的基础。     

激光二极管点火系统研究进展

综述了激光点火方式、激光二极管点火系统的组成及最新发展。提出了一种激光二极管点火系统结构,描述了各部分的关键技术。介绍了国外在光回路检测、保险与解保险及多路点火方面的研究成果,以及国内在温度控制、光纤芯径对点火阈值功率的影响和激光点火器设计的研究成果。指出了当前激光点火技术在武器装备中的应用和现阶段激光点火遇到的技术难点。