含RDX四组元HTPB固体推进剂的冲击起爆特性研究

为了研究含RDX四组元HTPB固体推进剂的冲击起爆行为和在低温条件下的适应性,在常温和低温条件下,对该固体推进剂进行了冲击加载拉氏分析实验。采用锰铜压力计测量了推进剂中不同位置处的压力变化历程,采用电离探针测量了固体推进剂的爆速。分析了固体推进剂的爆轰成长规律,获得了推进剂的临界起爆压力、爆速、爆压和爆轰成长距离等爆轰特征参量。通过对比不同条件下的特征参量发现,低温对固体推进剂的冲击起爆特性影响较小。此外,还对固体推进剂的冲击起爆过程进行了数值模拟,标定了固体推进剂点火增长模型的反应速率方程参数和推进剂的未反应JWL状态方程参数。     

主控提前点火对复合推进剂慢速烤燃响应的影响

为研究主控点火对复合推进剂慢速烤燃响应特性的影响,设计并开展了典型复合推进剂装药慢速烤燃实验,结合数值计算和推进剂热分解失重及形貌演化过程,探讨了点火前推进剂内的温度分布情况及推进剂细观结构热损伤规律。研究发现:针对复合推进剂装药的慢速烤燃,在推进剂发生自热点火前温度较低时进行主控点火可以有效降低反应剧烈程度;随着加热温度的升高,推进剂中部分组分发生分解,导致推进剂内部温度高于壳体温度,同时推进剂中粘结剂及AP的分解会导致推进剂装药形成多孔状的结构,在点火后更易导致对流燃烧,加剧反应烈度;当壳体温度仅138 ℃时,推进剂温度最高点达到150 ℃,最高点首先出现在靠近喷管的尾部,考虑到粘结剂及AP部分分解导致的孔隙结构会加剧反应的响应烈度,主控点火温度应设定在138 ℃以下。     

含铝炸药水下滑移爆轰实验研究

为了研究含铝炸药水中爆炸近场范围内沿装药径向的冲击波特性及爆轰产物的膨胀规律,设计了水下滑移爆轰实验装置。采用高速扫描相机和阴影照相技术记录了一种RDX基含铝炸药的水下滑移爆轰过程,获得了清晰的水下滑移爆轰过程的扫描图像。通过对图像进行分析,得到了水中爆炸近场范围内沿装药径向冲击波的传播迹线及爆轰产物气泡的膨胀迹线,进而分析出冲击波传播速度、阵面压力及爆轰产物气泡的膨胀位移等参数的变化规律。此外,根据气泡的膨胀迹线,标定了该含铝炸药爆轰产物的JWL状态方程参数,并将其与Φ50mm圆筒实验确定的参数值在p-V图上进行了对比。结果显示,两者偏差较小,证实了该方法的可行性。     

考虑自然对流的某固体火箭发动机慢速烤燃特性数值分析

针对某高氯酸铵/端羟基聚丁二烯(AP/HTPB)推进剂固体火箭发动机，采用两步总包反应描述AP/HTPB的烤燃过程，建立了考虑发动机空腔自然对流的二维轴对称烤燃模型，对加热速率分别为3.6、7.2和10.8 K/h时火箭发动机的慢速烤燃行为进行了数值预测，研究了该火箭发动机的热安全性问题。结果表明，固体火箭发动机空腔内的自然对流对AP/HTPB推进剂的着火温度、着火延迟期和着火位置有一定影响，在热安全性精确分析中不可忽略。3种加热速率下，AP/HTPB推进剂的最初着火位置均出现在药柱肩部的环形区域内，3种加热速率对应的着火延迟期、着火温度及着火时壳体温度分别为30.71、20.06、18.68 h，526.52、528.10、530.64 K，和479.56、496.82、508.77 K。随着加热速率的增大，烤燃响应区域向推进剂与绝热层交界处移动，着火位置的二维截面由椭圆形变为半椭圆形。     

氧化性粘合剂夹层三明治推进剂模型细观燃烧数值分析

复合固体推进剂在细观层面上呈现准周期性阵列,取推进剂基本"胞元"建立周期性三明治模型,可简化细观结构建模,又能反映复合推进剂燃烧的本质特征(如异相界面、多重火焰相互作用等).由于实际推进剂中氧化剂颗粒的粒径分布较广,纯粘合剂三明治模型只能计算单尺寸氧化剂颗粒分布情形.本文采用隐式颗粒建模方法,引入氧化性粘合剂夹层三明治推进剂模型表征AP/HTPB双模推进剂,考虑细氧化剂AP颗粒对细观燃烧规律的影响.通过数值实验,分析氧化性粘合剂三明治模型的火焰结构与燃面型面、燃面特性及燃速特性,并与纯粘合剂三明治推进剂细观燃烧规律进行对比分析.     

NEPE固体推进剂含损伤的黏弹性本构研究

作为一种新型高能固体推进剂,NEPE推进剂在固体火箭发动机中得到了越来越多的应用。本文首先对NEPE固体推进剂进行了松弛试验和单轴等速拉伸试验,在试验结果的基础上,对积分型本构进行了修正,增加了率的影响函数。考虑到颗粒大小的分布,借用Weibull分布函数形式构建了受损面积比与伸长比、应变率的变化关系,建立了一个损伤函数,较好地描述了推进剂拉伸过程中的损伤。综合修正积分本构与损伤函数,给出了NEPE固体推进剂含损伤的黏弹性本构,并用多个速率的拉伸试验曲线进行了验证,结果显示试验值与理论值吻合较好。     

点火条件对密闭管道内预混氢气/空气燃爆特性的影响

基于流体动力学软件Fluent,开展数值模拟,研究点火位置（距管左端壁面100、200和500 mm）、点火温度（1 000、1 500和2 000 K）和点火面积（管左端壁面处半径为50、35和20 mm的点火域）等点火条件对1 000 mm密闭管道中预混氢气/空气（H₂/air）燃爆特性的影响。研究表明:点火位置距管左端壁面越远,中间节点处温度越高,温升越快;不同点火温度下管内最高温升速率基本同步,且提高点火温度,使得燃烧反应更剧烈,能提高管内气体温升速率,但却降低管内的压力峰值;点火面积越小,预混H₂/air燃烧前期温升越快。当采用半径为35 mm的点火域和点火位置距管左端壁面100 mm的点火方式时,预混H₂/air燃爆的各项参数相对较高。不同点火条件对密闭管内气体的动能和内能的影响规律类似于其对管内气体的流速和温度的影响规律,而对涡量的影响不明显。     

低冲击下固体推进剂延迟起爆现象

为了研究固体推进剂在低强度冲击作用下的延迟爆轰现象（XDT）,设计了2次冲击波加载的双隔板实验。用X光摄像技术观测了推进剂在低强度冲击作用下的延迟起爆现象。建立了推进剂双隔板实验计算模型,运用非线性动力学有限元方法对推进剂的双隔板实验进行了数值模拟,得到推进剂在2次独立冲击波加载作用下的压力历史,分析了推进剂发生延迟爆轰的受力过程。结果表明,在强度较低的冲击波作用下,该推进剂会发生XDT现象,对推进剂重复冲击加载作用和推进剂在加载作用下的敏化程度是控制XDT现象发生的主要因素。     

等离子体发生器放电参数对推进剂燃烧特性的影响

揭示了电热化学炮所用的等离子体发生器初始放电参数对推进剂燃烧特性的影响规律。实验主要在密闭药室里进行 ,研究了等离子体发生器中毛细管初始几何尺寸以及输入电能发生变化时 ,推进剂的燃烧行为发生的变化规律。研究结果表明 ,推进剂的燃烧行为对等离子体发生器初始放电参数有较强的依赖性。     

点火过程和初始条件对燃烧轻气炮内弹道性能的影响

采用计算流体力学方法对燃烧轻气炮膛内燃烧过程进行数值模拟,分析不同的点火点数目和点火能量以及初始温度和压力对燃烧轻气炮内弹道特性的影响。结果表明,采用合理的点火点数目、初始温度和压力条件可以有效控制氢气的燃烧过程,减弱燃烧室内的压力波动。模拟结果对燃烧轻气炮膛内燃烧过程控制具有重要参考价值。     

Numerical modeling of the processes within the combustion chamber of a solid propellant rocket engine during the stabilization of the design operation mode

Comprehensive numerical modeling of the processes occurring in the combustion chamber of a solid propellant rocket engine during the stabilization of the design operation mode is performed. The self-consistent problem considered includes nonstationary operation of an ignition device, warmup and ignition of a solid propellant charge followed by its nonstationary burning, nonstationary threephase homogeneous-heterogeneous flow of the combustion products in the combustion chamber, in the nozzle, and behind the engine nozzle unit, engine depressurization, and nozzle unit plug blowing-out. The results of the calculations are presented.     

固体发射药等离子体点火过程及弹道效应分析

总结了常规火炮点火的现状,分析了固体药电热化学炮（ＳＰＥＴＣ）点火的潜在优势,并对等离子体点火过程中存在的燃速增强机理进行了讨论。作为等离子体点火的弹道效应分析,利用电热增强固体药内弹道、等离子体发生器、脉冲功率源三者的耦合编码,计算了不同点火功率、不同毛细管径对ＳＰＥＴＣ炮弹道性能的影响。     

多孔发射药等离子体增强燃速

利用密闭爆发器实验系统进行了等离子体增强4/7高固体发射药燃速特性的实验研究。采用等离子体发生器的电能利用效率来表征密闭爆发器内输入的等离子体能量,拟合了考虑压力梯度影响和电功率增强的固体发射药瞬态燃速公式。根据实验数据得到4/7高固体发射药的电功率燃速增强因子为0.005 MW-1。与Woodley燃速公式相比,瞬态燃速公式与实验压力曲线符合程度更高,能够更精确地描述固体发射药在等离子体作用下的燃烧过程。     

再生式喷雾燃烧过程中着火延迟期的影响特性

对液体药火炮中的再生式喷雾燃烧过程进行了大量的实验研究，发现了着火延迟期对再生式喷雾燃烧过程的重要影响。建立了反映着火后燃烧室内压力状态与着火延迟期间各参量之间关系的分析模型；结果表明，随着着火延迟期的延长，延迟期间液体药堆积量不断增加，进而导致着火后压力升高率急剧增大。运用零维数学模型对整个再生喷雾燃烧过程进行了模拟，模拟结果进一步证实了分析模型结论，较好地再现了正常燃烧过程和非正常燃烧过程的基本特征，阐明了着火延迟期对再生喷雾燃烧过程影响的物理本质。     

Nonstationary burning of propellants with variable surface temperature

The author examines nonstationary processes (combustion at varying pressure, quenching, and ignition) for a model propellant whose burning rate u and surface temperature t₁ depend on pressure p and initial temperature T₀. All the processes in the surface reaction zone and the gas phase are assumed inertialess. It is shown that a theory of nonstationary combustion for such a model can be constructed by analogy with the Zel'dovich theory [1, 2], in which the surface temperature of the powder is assumed fixed. The variation of burning rate with time has been investigated for small sudden pressure changes. It is shown how a sufficiently large and steep pressure drop may cause quenching of the propellant. The process of propellant ignition is subjected to a qualitative analysis.The author thanks O. I. Leipunskii, A. G. Istratov, V. B. Librovich, and A. D. Margolin for their comments and advice.     

Performance of propellant decomposition products as fuel in an airbreathing PDE

Decomposition products of a solid propellant are considered as a possible fuel in an airbreathing pulse detonation engine (PDE). However, these decomposition products contain not only gaseous species but also a significant amount of solid carbon particles. Whether performance can be improved by burning these particles is investigated numerically. Thermodynamic calculations allow predicting the quantity of additional air required for optimum performance. Gasdynamic numerical simulations indicate that particle burning has an effect on the pressure impulse on the thrust wall. The particle size determines the detonation structure, according to the model of hybrid detonations, thus governing the delay and rate of heat release from particle combustion behind the detonation front. In the situation investigated here, the particles are incompletely burnt inside a 0.6-m-long tube. As a result, smaller particles ( ≤ 5μm) contribute to an increase in the impulse, by up to 6%. However, larger particles either have a negligible effect on the pressure impulse, if around 10 μm, or result in a decrease, if around 20 μm. Overall, the calculations show that the best efficiency is obtained for this fuel by diluting the gaseous decomposition products with an additional quantity of air, allowing for incomplete particle combustion rather than letting them behave as if inert, absorbing part of the energy released by gaseous combustion.This paper was based on a work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive Systems, Montreal, Canada, July 31–August 5, 2005.     

汽油机燃烧室内温度场测量的激光剪切干涉法

采用激光剪切干涉法测量了汽油机燃烧室内的温度场,并分析了剪切干涉法测温的基本原理,推导出利用干涉条纹图求解温度分布的关系式。在一台二冲程火花点火发动机上设置石英窗和信号同步系统,建立了适合高速摄影的激光剪切干涉测量装置。通过改变剪切干涉量,测取发动机燃烧室内干涉条纹图,从而获得缸内燃烧的二维温度场。结果表明,激光剪切干涉法抗振性强,光路简单可靠,可以进行高速摄像,是研究内燃机燃烧过程的有效方法。从温度场可以看出,燃烧过程中缸内大致可分为三个区,即已燃区、未燃区和燃烧区,具有不同的温度分布和温度梯度。燃烧区温度最高,温度梯度大;已燃区温度次之,梯度较小;未燃区温度最低,但梯度较大。     

Experimental study of syngas combustion at engine-like conditions in a rapid compression machine

As the world energy demand and environmental concern continue to grow, syngas is expected to play an important role in future energy production. It represents a viable energy source, particularly for stationary power generation, since it allows for a wide flexibility in fossil fuel sources, and since most of the harmful contaminants and pollutants can be removed in the post-gasification process prior to combustion. In this work, two typical mixtures of H₂, CO, CH₄, CO₂ and N₂ have been considered as representative of the producer gas coming from wood gasification, and its turbulent combustion at engine-like conditions is made in a rapid compression machine in order to improve current knowledge and provide reference data for modeling and simulation of internal combustion engines. Methane as main constituent of the natural gas is used as reference fuel for comparison reasons. Single compression and compression- expansion events were performed as well direct light visualizations from chemiluminescence emission. There is an opposite behavior of the in-cylinder pressure between single compression and compression-expansion strokes. For single compression, peak pressure decreases as the ignition delay increases. In opposite, for compression-expansion the peak pressure increases as the ignition delay increases. This opposite behavior has to do with the combustion duration under constant volume conditions. Conclusion can be drawn that higher pressures are obtained with methane-air mixture in comparison to both typical syngas compositions. These results could be endorsed to the heat of reaction of the fuels, air to fuel ratio and burning velocity. Another major finding is that syngas typical compositions are characterized by high ignition timings due to its low burning velocities. This could compromise the use of typical syngas compositions on high rotation speed engines.