Study on Near Field Dispersal of Fuel Air Explosive

Aim To study fuel dispersion in fuel air explosive(FAE) and computational ways of fuel dispersion velocity in the near area. Methods\ The dispersion process of fuel in FAE was analyzed by the use of results measured with KODAK EKTAPRO EM Motion Analyzer and setting up mechanical models. Results\ Computational methods for fuel dispersion velocity in the acceleration stage is given and taken as a base for the study of fuel dispersion in the intermediate and the far area. Conclusion\ When the fuel flow velocity is higher than that of the explosion gas in the center cavity, the fuel divides with the explosion gas and its velocity of flow reaches a maximum. The acceleration stage ends at that time. The fuel dispersion velocity at this time is the initial conditions for numeral analyses of dispersion process in the intermediate and far areas.

Effect of metal powders on explosion of fuel-air explosives with delayed secondary igniters

In order to improve the energy level of fuel air explosive(FAE) with delayed secondary igniters, high energetic metal powders were added to liquid fuels mainly composed of ether and isopropyl nitrate.Metal powders’ explosive properties and reaction mechanisms in FAE were studied by high-speed video,pressure test system, and infrared thermal imager. The results show that compared with pure liquid fuels, the shock wave overpressure, maximum surface fireball temperature and high temperature duration of the mixture were significantly increased after adding high energetic metal powder. The overpressure values of the liquid-solid mixture at all measuring points were higher than that of the pure liquid fuels. And the maximum temperature of the fireball was up to 1700C, which was higher than that of the pure liquid fuels. After replacing 30% of aluminum powder with boron or magnesium hydride, the shock wave pressure of the mixture was further increased. The high heat of combustion of boron and the hydrogen released by magnesium hydride could effectively increase the blast effect of the mixture. The improvement of the explosion performance of boron was better than magnesium hydride. It shows that adding high energetic metal powder to liquid fuels can effectively improve the explosion performance of FAE.

典型金属粉末对FAE冲击波效应和热毁伤性能的影响

为了探究典型金属粉末对燃料空气炸药(fuel air explosive,FAE)冲击波效应和热毁伤性能的影响,采用20 L球形液体爆炸测试系统并结合比色测温方法,深入研究了不同金属粉种类和含量下环氧丙烷(epoxypropane,PO)的燃爆特性、火焰结构及温度分布特征。实验结果表明:纯环氧丙烷的最佳质量浓度为780 g/m^(3),最大爆燃超压Δp_(max)=0.799 MPa,最大压力上升速率(dp/dt)_(max)=52.438 MPa/s。添加Al粉、Ti粉和Mg粉的环氧丙烷最大燃爆超压、最大压力上升速率和最大火焰平均温度均随着金属粉末质量比(I)的增加而增大,而最大压力上升时间的变化趋势则与之相反;最大燃爆超压和最大火焰平均温度的变化规律一致,从大到小依次为:Al/PO、Mg/PO、Ti/PO,且当金属粉的质量比I=40%时,3种固-液混合燃料的?pmax值相较于纯环氧丙烷分别增加了12.00%、8.41%和11.54%;此外,最大压力上升速率和燃烧速率的变化规律一致,从大到小依次为:Mg/PO、Al/PO、Ti/PO,且当金属粉的质量比I=40%时,3种固-液混合燃料的(dp/dt)max值相较于纯环氧丙烷分别增加了41.91%、39.60%和45.29%。研究结果表明,不同高能金属粉末在改善环氧丙烷燃爆性能方面各有优势,在FAE的配方设计时,应根据毁伤性能指标合理选择金属粉末作为含能添加剂。

Research on the Explosion Temperature Response of Fuel Air Explosive Measured by Colorimetric Pyrometer

An infrared colorimetric radiation thermometrical system was established based on the theory of optical radiation. The dynamic temperature history of fuel air explosive (FAE) was measured to obtain the temperature responses of primary initiation FAE and secondary initiation FAE in real time. And the characteristics of their temperature history curves were compared and analyzed. The results show that the primary initiation FAE has higher explosion temperature and longer duration compared to the secondary initiation FAE.

Effect of Center High Explosive in Dispersion of Fuel

The dispersion of the fuel due to the center high explosive, including several different physical stages, is analyzed by means of experimental results observed with a high speed motion analysis system, and the effect of center high explosive charge is suggested. The process of the fuel dispersion process can be divided into three main stages, acceleration, deceleration and turbulence. Within a certain scope, the radius of the final fuel cloud dispersed is independent of the center explosive charge mass in an FAE (fuel air explosive) device, while only dependent both on the duration of acceleration stage and on that of the deceleration. In these two stages, the dispersion of the fuel dust mainly occurs along the radial direction. There is a close relation between the fuel dispersion process and the center explosive charge mass. To describe the motion of fuel for different stages of dispersion, different mechanical models should be applied.

A new equivalent method to obtain the stoichiometric fuel-air cloud from the inhomogeneous cloud based on FLACS-dispersion

The fuel-air cloud resulting from an accidental discharge event is normally irregular in shape and varying in concentration. Performance of dispersion simulations using the computational fluid dynamics （CFD）-based tool FLACS can get an uneven and irregular cloud. For the performance of gas explosion study with FLACS, the equivalent stoichiometric fuel-air cloud concept is widely applied to get a representative distribution of explosion loads. The Q9 cloud model that is employed in FLACS is an equivalent fuel-air cloud representation, in which the laminar burning velocity with first order SL and volume expansion ratio are taken into consideration. However, during an explosion in congested areas, the main part of the combustion involves turbulent flame propagation. Hence, to give a more reasonable equivalent fuel-air size, the turbulent burning velocity must be taken into consideration. The paper presents a new equivalent cloud method using the turbulent burning velocity, which is described as a function of SL, deduced from the TNO multi- energy method.

Flame behavior, shock wave, and instantaneous thermal field generated by unconfined vapor-liquid propylene oxide/air cloud detonation

Energy output and heating effects are essential for vapor-liquid fuel/air cloud detonation in the fuel-air explosive(FAE) applications or explosion accidents. The purpose of this study is to examine the dynamic large-size flame behavior, shock wave propagation law, and instantaneous thermal field generated by unconfined vapor-liquid propylene oxide(PO)/air cloud detonation. Based on computational fluid dynamics(CFD) and combustion theory, a numerical simulation is used to study the detonation process of a PO/air cloud produced by a double-event fuel-air explosive(DEFAE) of 2.16 kg. The large-scale flame behavior is characterized. The flame initially spreads radially and laterally in a wing shape. Subsequently,the developed flame increases with a larger aspect ratio. Moreover, the propagation laws of shock waves at different heights are discussed. The peak pressure of 1.3 m height level with a stepwise decline is obviously different from that of the ground with an amplitude of reversed ’N’ shape. In the vast majority of the first 6.9 m, the destructive effect of the shock wave near the ground is greater than that of the shock wave at 1.3 m height. Furthermore, the dynamic instantaneous isothermal field is demonstrated.The scaling relationship of various isotherms in the instantaneous thermal field with the flame and initial cloud is summarized. The comprehensive numerical model used in this study can be applied to determine the overpressure and temperature distribution in the entire fuel/air cloud detonation field,providing guidance for assessing the extent of damage caused by DEFAE detonation.

油气场站火灾爆炸风险的神经支持决策树识别与预测

为了有效防控油气场站火灾爆炸事故,从影响因素之间因果关系的角度出发,提出利用神经支持决策树(Neural-Backed Decision Tree,NBDT)算法构建油气火灾爆炸可解释预测模型。该方法利用词频逆向文件频率(Term Frequency-Inverse Document Frequency,TF-IDF)算法从风险描述信息中提取出关键词并计算权重,整合得到64个风险二级因素,构建了油气场站的火灾爆炸数据集;采用神经支持决策树算法构建分类模型,对油气场站火灾爆炸事故进行预测和可解释分析,可以基于数据可视化地分析油气火灾爆炸事故的风险与诱因。结果表明,NBDT模型预测准确率为0.976,AUC为0.913,明显优于其他模型;模型可视化结果分别从单因素和多因素角度分析,确立7种二级风险主控因素和6种二级风险组合主控因素。13种风险主控因素的确立,可以为既有油气场站火灾爆炸预测和防控机制提供理论支撑。

高温环境因素对固-液混合燃料物理稳定性的影响

固-液混合燃料的物理稳定性对于燃料的质量和安全性均有重要的意义。高温环境引发的易挥发液体组分的气化将对燃料的物理稳定性产生极为复杂的影响。通过自主设计的实验装置模拟、加速燃料物理稳定性改变,并分别从液体燃料析出及密度分布变化趋势,分析高温环境因素的作用。结果表明:自然堆垛状态下燃料的顶部受饱和蒸汽压的改变影响较大,而中部、底部则由于燃料的紧密堆积,形成各自独立的气液平衡。同时,液体燃料于高温环境中对固体的润湿效果随之增强,更有利于液体组分完成对固体颗粒的吸附。在303~333 K的温度条件下,固液体积比为1.25∶1,硝基甲烷占液体组分40%的固-液混合燃料保持最佳的物理稳定性。

中心装药对FAE燃料成雾特性影响的试验分析

为了优化燃料空气炸药(FAE)装置参数,采用高速运动分析系统,观测燃料云雾的分散过程,研究中心装药对燃料云雾体积的影响规律。试验结果表明,燃料空气炸药装置的中心装药起爆后,燃料开始分散,云雾体积逐渐增大。燃料云雾抛散过程和最终体积与中心装药有关,当中心装药能量较小时,燃料云雾最大体积随中心装药能量增大而增大,当中心装药能量达到临界值以后,燃料云雾的最大体积不再随能量增大而增大。

提高FAE威力的研究（Ⅰ）─—高能量燃料的选择

提高ＦＡＥ威力的途径是选用高能量燃料配方和优化云爆条件。该文讨论了几种燃料的特性。含铝混合燃料具有能量性能好，爆压、爆温较高，冲击波作用范围和破坏威力有较大提高之优点。Ｈ、Ａｌ、Ｍｇ、Ｂ元素具有最优的能量性能。

爆炸抛撒过程中FAE云雾的运动特性

为研究爆炸抛撒过程中燃料空气炸药（FAE）云雾的发展和变化特征,通过高速摄影观测了不同密度FAE的云雾形成和运动状态,用数值仿真计算了燃料圆柱外表面中心点处质点的速度变化,在距爆心2.5 m处利用光电探测方法测量了云雾相对浓度变化。结果表明：燃料在云雾形成之前的运动主要以射流为主,云雾形成后主要为扩散运动。燃料密度越大,相同时刻云雾扩展直径越大。燃料质点的速度在爆炸抛撒条件下经历先快速增大后缓慢降低的过程,最高速度达到377 m·s-1。在10~80 ms,燃料浓度的变化幅度表现出由大到小的变化,显示抛撒云雾内部的燃料颗粒空间分布具有非均匀性的特点,并且适当延长云雾运动时间,燃料颗粒分布的均匀性可得到有效改善。

FAE爆炸场超压与威力的实验研究

利用现场测试系统动态灵敏度标定技术,分别等精度测试了FAE和TNT爆炸场峰值超压。在此基础上获得了各自的爆炸波峰值超压随传播距离的拟合曲线和TNT当量比。结果表明:FAE爆炸场超压分布规律与TNT有显著区别,前者属于大体积云雾爆炸,爆炸场可划分为云雾爆轰区、云雾边缘区和冲击波作用区;在云雾爆轰区,超压平均值在2.6MPa左右,在小于2/3云雾半径的范围内比同质量的TNT低,在大于2/3的云雾半径范围则显著大于TNT;在冲击波作用区,环氧丙烷燃料的FAE爆炸超压约是TNT爆炸效果的5倍,超压均呈衰减趋势,但FAE衰减比TNT缓慢许多。

FAE爆炸波对地面目标作用的三维数值研究

利用二阶迎风TVD格式 ,对多组分全N S方程进行全耦合数值求解 ,研究了近地空中环氧丙烷 (C3H6 O)形成的圆柱形云雾爆炸波和地面作用问题 ,得到了对目标作用前、后冲击波的传播和波系结构的演化以及不同时刻爆源组分的分布。对目标表面计算单元的压力进行面积加权平均 ,得到目标各表面平均超压随时间变化的曲线。压力值的动画显示表明了目标表面所受载荷的大小和分布随时间变化的规律。修改初、边值条件 。

一次起爆FAE的燃料扩散特征

利用高速摄影和红外测温计,实测了伴有爆炸反应的FAE燃料扩散速度、半径及云雾的温度;分析表明:化学一次起爆FAE装置,燃料出壳体后2ms达最大运动速度。化学起爆和高速分散一次起爆试验装置燃料抛撒都具有较高的初始扩散速度,装置的结构参数对燃料扩散过程有较大影响。

高威力FAE液态燃料的优化选择

应用系统工程理论建立了高威力 FAE的燃料优化分析评价方法 ,对 FAE液态燃料进行了优化排序和筛选 ,得到了综合效能较优的

燃料空气炸药（FAE）装置爆炸场的研究

燃料空气炸药（ＦＡＥ）装置在一次点火后，液体燃料在中心装药爆轰驱动下，抛撒在空气中形成燃料空气云，用高速摄影记录了该燃料空气云的形成过程。为达到所要求的气云形状，在对高速摄影照片充分分析的基础上，本文对ＦＡＥ装置的结构设计提出了改进意见。燃料空气云在二次点火后实现爆轰，本文测量了沿地面主力学线的压力时间曲线，用高精度、高分辨率的ＴＶＤ格式与瞬时爆轰模型对燃料空气云爆炸场进行了初步的数值模拟，得到了不同时刻的压力等值线与沿地面的压力分布。结果表明；计算与实验得到的各测点的压力最大值基本相等。

FAE威力评价方法与目标防护分析

对燃料空气炸药（ＦＡＥ）爆炸场特性进行了分析；从冲击波超压－ 冲量毁伤准则出发，提出一种以靶板毁伤效应为评价依据的ＦＡＥ威力评价方法，并结合易损性等效原理。

抗高过载FAE燃料的性能

通过试验验证了抗高过载FAE燃料的物化性能、爆炸威力及抗过载能力,研究内容包括燃料的内相容性、撞击感度、摩擦感度、静爆威力、燃料爆炸的火球发展历程以及燃料在各种撞击过载和发射过载条件下的状态变化等。结果表明,燃料的爆炸比威力大于2.0倍TNT当量,装填密度大于1.55g/cm3;燃料内相容性和安定性良好,抗过载能力经过小样试验大于2×105m/s2,其性能基本满足工业化生产的安全性要求。

多元固相FAE的离散与爆轰的协调研究

一次起爆技术使FAE的两个主要研究方向,即燃料选择与云爆技术,更加紧密地结合在一起,导致对燃料的离散与爆轰的自协调要求更加严格。根据燃料的离散与爆轰的自协调的各制约因素对燃料组分进行选择,再改变燃料组分的质量配比以反馈研究燃料的离散与爆轰的协调性。实验证明所选择的混合燃料的离散与爆轰的协调性决定了超压峰值、正压作用时间、火球覆盖体积等参数,故可根据实际需要通过改变燃料组分配比来调节其协调性以研制不同特点的一次起爆型FAE。另外,基于VB.net平台自编的图像批处理程序,对由高速摄影拍摄到的FAE离散爆轰过程的图像进行处理,效率高、精度高,而且能和Excel、Origin等数据处理软件对接。