多孔颗粒火药床燃烧转爆轰的敏感性研究

本文以不同粒度硝胺火药RDU-4,硝胺火药RPB,3/1-S为研究对象,探讨了多孔颗粒火药床燃烧转爆轰的敏感性。研究结果表明,火药颗粒尺寸越小,硝胺火药燃烧转爆轰越易实现:硝基胍组分具有抑制燃烧转冲击的作用,就同一装填条件下燃烧转冲击的难易而言,以RPB最易,3/1-S次之,RDU-4最难     

多孔火药填充床中燃烧转爆轰(DDT)的模拟与分析

随着火炮装药装填密度的提高和火箭推进剂中硝胺组份的增加,它们的总体性能虽有改善,但同时使燃烧转爆轰的感度也加大。在一定条件下,粒状高能固体火药填充床中,将出现DDT现象。本文着重研究燃烧转爆轰前的过程。描述DDT过程的两相反应流体动力学模型用MacCormack有限差分格式求解,得到的转爆距离和爆轰速度与试验观察结果符合得很好。计算表明,粒状药床中的两种转变机制似乎是可以相互转化的。     

爆轰快速点火实验研究及机理分析

为了验证采用爆轰可迅速引燃点火药进而引燃主装药的可行性及掌握此种点火方式下的点火情况,建立了火药装药系统下直列式起爆器爆轰点火实验系统.在特定装药条件下,对点火后实验装置内压力变化情况进行了测量,得出采用爆轰点火方式可以实现点火延迟时间为0.3 ms的目标,以及得出此种点火方式下,火药燃烧特点及实际应用时的注意事项,如...     

长管强约束条件下压装PBX炸药点火实验研究

为探究压装炸药PBX-A在较强约束条件下、在药柱一端使用点火药引燃后能否发生燃烧转爆轰,在传统DDT管的基础上重新设计了特定位置约束增强的厚壁钢柱壳管实验装置,利用多路PDV诊断技术,配套高速摄影记录对点火药引燃炸药实验过程中的柱壳膨胀、断裂特性等实验现象进行了全过程连续监测。对比由爆轰驱动的相同装药条件下实验现象及对应过程物理状态的区别,发现:爆轰实验和点火实验 的总反应时间历程存在数量级的差别;柱壳上各个测点速度历程反映出装置内部炸药反应引起的压力增长历程特征,以及炸药反应的传播过程均存在明显差异。分析表明,在较强约束条件下,典型压装炸药PBX-A在一端使用点火药引燃后的反应行为实际是以高温、高压反应产物沿装药缝隙对流,炸药表面的层流燃烧及其伴随的结构响应行为为主要表现形态;从反应压力水平及其增长的时间历程来看,炸药基体中没有形成冲击波,因而无法实现从冲击到爆轰的转变。     

APS—RS型高速相机在气相爆轰实验中的应用研究

基于气相燃烧转爆轰机理研究,探索利用APX-RS型高速数字相机测量氢氧混合气体在电火花点火后的火焰和前驱冲击波的变化历程,获得火焰加速以及冲击波的产生与成长过程的高速摄影图像;计算了不同位置的前驱冲击波参数和气体状态参数;分析了燃烧转爆轰机制。结果表明：APX—RS型高速相机可以成功地拍摄气相燃烧转爆轰过程,并获得氢氧混合气体燃烧转爆轰为局部爆炸机制。     

弱约束条件下NEPE推进剂燃烧转爆轰研究

建立了推进剂燃烧转爆轰（ＤＤＴ）弱约束实验系统，利用探针和Ｘ光实验测量系统，研究了ＮＥＰＥ推进剂ＤＤＴ过程。实验发现，由燃烧到爆轰的转变过程中存在一未燃未爆区，该区域将ＤＤＴ流场分隔为爆燃区和冲击转爆轰（ＳＤＴ）区。分析了该高能推进剂的ＤＤＴ机理。     

弱约束条件下NEPE推进剂燃烧转爆轰研究

建立了推进剂燃烧转爆轰（ＤＤＴ）弱约束实验系统，利用探针和Ｘ光实验测量系统，研究了ＮＥＰＥ推进剂ＤＤＴ过程。实验发现，由燃烧到爆轰的转变过程中存在一未燃未爆区，该区域将ＤＤＴ流场分隔为爆燃区和冲击转爆轰（ＳＤＴ）区。分析了该高能推进剂的ＤＤＴ机理。     

推进剂的撞击损伤状态对其燃烧转爆轰的影响

设计加工了燃烧转爆轰的实验装置,并建立了相应的测试系统,旨在研究NEPP推进剂颗粒装药的燃烧转爆轰形成机理。并以大型落锤为加载手段,撞击NEPP推进剂试样,经实验发现,损伤明显地促进了颗粒装药燃烧向爆轰的转变,增加了该推进剂使用的危险性。     

铝粉/空气二维黏性两相爆轰的数值模拟

为了深入研究爆轰波形成和传播的机理与特性,建立了管内铝粉/空气二维黏性两相爆轰过程的数学模型,采用守恒元与求解元方法进行数值计算,并对其物理参数的分布进行了分析。结果表明:管内燃烧转爆轰的初期,压力沿径向变化明显,与壁面碰撞有明显的反射波;燃烧转爆轰的中后期,压力沿轴向变化明显,但径向效应仍不能忽视,碰撞形成的反射波对最终稳定爆轰波的形成影响较大。研究结果同时表明:不仅铝粉颗粒初始半径对爆轰波的形成与传播有一定的影响;而且气体的黏性作用在研究爆轰管内近壁面处流场时不容忽视。研究结果有利于进一步揭示铝粉燃烧转爆轰的机理。     

铝粉－空气混合物燃烧转爆轰（DDT）过程的实验研

在水平粉尘爆轰管上分别对２ｍ、５ｍ和１３ｍ三种粒径的铝粉－空气混合物进行了弱点火条件下燃烧转爆轰的实验研究。实验分别考察了粉尘浓度、颗粒尺度及扬尘方法等因素对爆轰特性（如爆轰速度、最大压力等）的影响。结果表明，２ｍ球形铝粉最大爆轰压力达７．８ＭＰａ、稳态爆速达１．９５ｋｍ／ｓ；５ｍ铝粉亦有爆轰特征，但状态较弱；１３ｍ的铝粉达不到爆轰。混合物的浓度对爆轰参数有影响，并存在最优浓度，在此浓度下，爆轰参数取得最大值，而且最优浓度的值随粉尘颗粒直径增加而增大。扬尘方法对爆轰特性有影响，预混粉尘与激波卷扬粉尘对比实验表明，其压力与速度的典型差别分别高达３００％与７４％。     

A two-phase mixture theory for the deflagration-to-detonation transition (ddt) in reactive granular materials

In this paper, a two-phase mixture theory is presented which describes the deflagration-to-detonation transition (DDT) in reactive granular materials. The theory is based on the continuum theory of mixtures formulated to include the compressibility of all phases and the compaction behavior of the granular material. By requiring the model to satisfy an entropy inequality, specific expressions for the exchange of mass, momentum and energy are proposed which are consistent with known empirical models. The model is applied to describe the combustion processes associated with DDT in a pressed column of HMX. Numerical results, using the method-of-lines, are obtained for a representative column of length 10 cm packed to a 70% density with an average grain size of 100 μm. The results are found to predict the transition to detonation in run distances commensurate with experimental observations. Additional calculations have been carried out to demonstrate the effect of particle size and porosity and to study bed compaction by varying the compaction viscosity of the granular explosive.     

一种改进的颗粒移动床μ(I)拟流体模型及应用

颗粒移动床在工业领域应用广泛, 发展实用可靠的颗粒移动床模型具有理论和应用价值. 本文基于颗粒流μ(I)模型, 补充局部颗粒体积分数与颗粒局部压力和局部颗粒流密度的关系式, 将移动床内密集颗粒处理成可压缩拟流体, 建立了颗粒流单相可压缩流μ(I)模型, 并建立了颗粒流?壁面摩擦条件, 在计算中对颗粒流拟黏度和拟压力项进行正则化处理. 采用上述模型与方法对3种典型散料在移动床缩口料仓内的流动进行模拟, 与实验对比, 得到了玻璃珠、刚玉球和粗沙的μ(I)模型参数, 分析了3种不同散料在料仓内的颗粒速度、体积分数等分布特性, 模拟结果较好地揭示了料仓内不同物料的整体流和漏斗流特性; 进而以玻璃珠为例, 对移动床颗粒单管绕流流动进行了模拟, 所得结果合理揭示了管流附近的流动特性. 计算结果表明, 对于本文的计算工况, 颗粒体积分数变化最大范围为0.510 ~ 0.461, 绝大部分区域流动惯性数小于0.1, 改进的单相μ(I)模型能合理预测出密集颗粒流移动床内的流动特性, 方法可行且较多相流算法能明显减小计算量.      

含能材料密实床燃烧转爆轰的数值模拟

本文建立了含能材料密实床燃烧转爆轰的全粘性欧拉二维非定常两相反应流数学模型。将SIMPLE型的数值计算方法引入燃烧转爆轰的二维数值计算。对跨音速流动的处理和可压缩流体压力校正方程的建立提出了改进方法,并以无起爆药雷管作为算例。结果表明,本方法较好克服了二维两相流数值解的振荡现象。     

Numerical simulation of gas-solid flow with two fluid model in a spouted-fluid bed

The flow characteristics in a spouted-fluid bed differ from those in spouted or fluidized beds because of the injection of the spouting gas and the introduction of a fluidizing gas. The flow behavior of gas-solid phases was predicted using the Eulerian-Eulerian two-fluid model （TFM） approach with kinetic theory for granular flow to obtain the flow patterns in spouted-fluid beds. The gas flux and gas incident angle have a significant influence on the porosity and particle concentration in gas-solid spouted-fluid beds. The fluidizing gas flux affects the flow behavior of particles in the fountain. In the spouted-fluid bed, the solids volume fraction is low in the spout and high in the annulus. However, the solids volume fraction is reduced near the wall.     

Numerical simulation of gas–solid flow with two fluid model in a spouted-fluid bed

The flow characteristics in a spouted-fluid bed differ from those in spouted or fluidized beds because of the injection of the spouting gas and the introduction of a fluidizing gas. The flow behavior of gas–solid phases was predicted using the Eulerian–Eulerian two-fluid model (TFM) approach with kinetic theory for granular flow to obtain the flow patterns in spouted-fluid beds. The gas flux and gas incident angle have a significant influence on the porosity and particle concentration in gas–solid spouted-fluid beds. The fluidizing gas flux affects the flow behavior of particles in the fountain. In the spouted-fluid bed, the solids volume fraction is low in the spout and high in the annulus. However, the solids volume fraction is reduced near the wall.     

Ignition and growth of a detonation by a high energy plasma

Many experimental and numerical studies have been achieved to describe the transition process of deflagration to detonation when a projectile impacts an explosive. Also a large work has been done for the determination of various parameters — such as the impact pressure, the efficiency factors, etc. of the laser — material interaction. When a laser beam impacts an explosive, the P² criterion, characteristic of shock initiated detonations, is no longer valid due to the generated hot plasma whose effect is to decrease the DDT (Deflagration to Detonation Transition) duration. The present paper deals with a modelling of the plasma-explosive medium allowing the determination of distances and times of the DDT process. The two phase modelling of the granular explosive takes into account the creation of hot spots. The pressure of the plasma is computed using a semi empirical model, while the temperature is obtained from Maxwell Boltzmann statistics. The authors focused their attention on the equation of state for the detonation products and the numerical process.     

Numerical modelling of gas–solid fluidized beds using the two‐fluid approach

This paper details an approach to modelling gas–solid fluidized beds using the two‐fluid granular temperature model. Details concerning the difficulties associated with the boundary conditions, particularly for curved boundaries, are described along with a novel means of obtaining the internal stress of the solid‐phase, in part, by solving an implicit equation. This results in a scheme that is stable even when the solid volume fraction is close to maximum packing. A transient, mixed finite element discretization is used to solve the multi‐phase equations with a discontinuous finite element representation of the granular temperature and continuity equations. A new solution method is proposed to solve the coupled momentum and continuity equations based on Arnoldi iteration. Two fluidized beds are modelled, one in the bubbling regime and the other in the slugging regime. These simulations are compared with experiments. Copyright © 2001 John Wiley & Sons, Ltd.     

模型复合推进剂燃烧转爆轰研究

本文较详细地研究了模型推进剂(AP/wax,AP/A1/wax,AP/RDX/A1/wax)由燃烧转爆轰(DDT)的过程。分析了装药密度和铝粉含量对装药DDT的影响。结果表明:模型推进剂当其配比接近零氧平衡时较易产生DDT;含与不含铝粉的AP/粘合剂系复合推进剂药柱以及硝胺含量为20％的AP/硝胺炸药/A1粘合剂系复合推进剂药柱都不可能产生DDT。