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.

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.

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.

Flame Propagation Characteristics of Propane-Air Mixture in Ducts with Obstacles

An experimental study on acceleration mechanism of flame propagation of propane-air mixture in ducts with obstacles was conducted. The acceleration mechanism of flame propagation is mainly due to the positive feedback of the turbulence region induced by obstacles for combustion process. It can be seen from the experimental results that the maximum explosion pressure can increase by 20%, the maximum rate of pressure rise can increase by 10 times and the flame propagation velocity can increase by 20 times when obstacles are present.

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。

起爆方式对圆台型云爆弹装置燃料抛撒初期运动规律的数值模拟

为提高燃料空气炸弹(Fuel Air Explosive,FAE)装置爆炸抛撒燃料的极限速度并使速度更加平均,在不改变现有装置整体结构的情况下,采用数值模拟的方法研究起爆方式对FAE装置燃料抛撒径向极限速度的影响。使用有限元分析软件的任意拉格朗日-欧拉算法对圆台型FAE装置抛撒燃料进行数值模拟,对比单点起爆、多点起爆和近似线起爆情况下相同位置节点的径向抛撒速度变化情况。研究结果表明,对于燃料上的单元而言,距离较近的起爆点设置会对这个单元上燃料的抛撒运动产生抑制效果,近似线起爆的方式可以使云雾抛撒得更加均匀,为FAE爆炸燃料抛撒数值模拟的进一步细化研究奠定了基础。

内燃机夏季“高温病”的分析与解决方案

随着气候变暖,燃气内燃发电机组在夏季运行出力衰减甚至故障停机的问题频繁发生。对于一些能源服务公司而言,机组“高温病”亟待解决。通过对内燃机燃烧系统流程与原理分析,提出进风温度基本决定了混合气初始温度,为此可以通过冷却进风方式将混合气温度维持在高限值以下,这对于一些建筑通风管路复杂的既有项目,具有十分重要的现实意义。

An Analysis on the Motion Characteristics of Fuel and Shell in Launching

The relative characteristics of motion of the fuel and shell upon launching is analyzed. By means of mechanical analysis and calculation, it is proposed that relative motion exists not only in the ranges between the fuel and shell of the warhead, but also in the fuel in different positions. The result of study indicates that the position of the fuel in the warhead has a marked influence on the relative motion, while the frictional coefficient between the fuel and shell has less influence upon it.

Experimental Study on Single Ignition Characteristics of Mixed Solid and Liquid Fuel

In order to probe into the single ignition characteristics of mixed solid and liquid fuel, optical and electrical experinments on unconfined volume dispersion and single ignition of few dosage of ternary fuel mixture are successfully done. Experimental results show that cloud detonation is distinguished from explosion of trinitrotoluene charge. The single ignition process of mixed fuel containing aluminum powder（Al）, propylene oxide （PO） and explosive （TNT） can be divided into four stages, the overpressure within its explosion field first increases, then decays with increase of distance. Explosion effects can be enhanced with adding proper trinitrotoluene into fuel mixture, the optimized ratio is m （Al） ： m （PO）： m （TNT） - 55：35： 10. The overpressure of binary mixed fuel containing Al and TNT decays like trinitrotoluene charge with increase of distance, but its value is higher than the trinitrotoluene charge＇s in the same mass at longer distance. The continual action time of plus overpressure during cloud detonation reaches magnitude of 10 ms and is about 100 times longer than the trinitrotoluene charge＇ s.

高能液固混合燃料配方优化及毁伤分析

为筛选优化高能燃料空气炸药(FAE)的配方组分,以石油醚、环氧丙烷和乙醚作为液体燃料,硝酸异丙酯和硝基甲烷作为液体敏化剂,金属铝粉作为固体组分,通过EXPLO5计算软件比较了不同配比FAE的爆炸压力和爆炸温度,并在无约束条件下进行了液体和液固FAE配方的云雾爆轰实验,对爆炸场、温度场等参数进行了毁伤效果分析,并量化评估了各体系的热毁伤、超压毁伤的效果。结果表明,石油醚、环氧丙烷与硝酸异丙酯混合的混合液体FAE,在石油醚质量占比55%~70%条件下,爆轰性能上表现较优。液固混合FAE中液固比例为1∶1条件下具有较良好的爆轰性能,并在无约束云雾分散实验中表现出最佳的云雾分散状态。两种体系的FAE配方在1 kg的二次起爆药量下云雾爆轰可以稳定反应,能达到爆轰状态,且在毁伤能力均具有较优效果。

云爆弹内硝酸异丙酯气体快速检测

建立了一种用于云爆弹内硝酸异丙酯气体现场测试的装置和方法,在密封状态下实现气体的原位取样,利用集成光离子化检测器的便携式气体检测仪对弹筒内硝酸异丙酯气体浓度进行现场快速测试;通过气相色谱-质谱联用及红外光谱对现场采集的气体样品完成定性分析,采用气相色谱的方法对气体检测仪进行校准,实现现场测试数据的量值溯源。通过对某批次云爆弹的现场测试,获得了弹筒内硝酸异丙酯的气体浓度,为该云爆弹的安全贮存及故障分析提供了数据支撑。

湿度对管道内氢气-空气混合物爆炸特性影响的仿真研究

为了研究湿度对氢气-空气混合物爆炸特性的影响,应用FLACS软件建立一个左开右闭型氢气-空气混合物输送管道模型。通过改变管道内湿度摩尔体积分数D和混合物当量比Ф,仿真研究了氢气-空气混合物爆炸参数的变化。结果表明,当Ф=1.0时,D分别为10%、20%、30%、40%情境下,随着D的增加,最大爆炸压力最高下降了60%,火焰传播过程呈现出明显的衰减趋势,最大绝热火焰温度受湿度影响较小,取决于与点火源的距离;当Ф=0.5、0.8、1.0、1.2、1.5时,D的增加降低了爆炸强度,且在Ф=1.0时,湿度对爆炸超压和最大升压速率的抑制效果最为显著。此研究结果为预防氢气管道运输过程中的爆炸事故提供了理论参考。

多因素耦合作用对甲烷爆炸特性的影响

为了探究多因素耦合作用对甲烷爆炸特性的影响,采用1.2 L圆柱形爆炸装置,结合自主设计和搭建的可燃气体爆炸试验平台,从最大爆炸压力的角度分析了不同当量比φ(0.6~1.4)、初始温度T0(25~200℃)和初始压力p0(0.1~0.5 MPa)耦合条件对甲烷爆炸特性的影响规律。在此基础上,基于实验获得的最大爆炸压力数据,利用1stOpt构建了甲烷最大爆炸压力与当量比、初始温度和初始压力的非线性回归预测模型。结果表明:在初始温度和初始压力耦合作用下,初始压力越高,初始温度对最大爆炸压力的影响越大;初始温度越高,初始压力对最大爆炸压力的影响越小。在初始压力和当量比耦合作用下,在研究的实验条件范围内,当φ<0.9或φ>1.2时,初始压力越高,最大爆炸压力的变化越显著。在初始温度和当量比耦合作用下,在实验条件范围内,当φ>1.15时,初始温度越高,最大爆炸压力的变化越显著。此外,通过将基于1stOpt预测模型的预测结果与实验测试结果相比较,发现二者之间的相对误差均小于10%,表明该预测模型具有较高的精度和适应性。

高落速云雾爆轰的数值模拟

为了研究落速1000 m·s^(-1)条件下的燃料分散和爆轰过程,建立了燃料分散爆轰的计算仿真模型,以静态燃料分散及云雾爆轰实验结果作为数值方法进行了验证,分析了2 kg环氧丙烷燃料在高落速条件下分散爆轰的温度、压力随时间变化规律。结果发现:落速1000 m·s^(-1)条件下,数值模拟得到了云雾形态、浓度场随时间和空间的分布规律,云雾形态大致呈扇形,浓度随距离增加逐渐降低,最终达到稳定分布,云雾径向半径可达2.24 m,同时得到云雾爆轰过程及爆轰压力场、温度场的影响规律,起爆后形成弧形波阵面向外扩散且温度压力不断衰减。数值模拟结果与实验相吻合,为高落速云爆武器系统的安全设计提供了新途径。

大容量兆瓦级发电氢内燃机关键技术介绍

为了提升大容量兆瓦级发电氢内燃机的动力性能,防止早燃、回火和爆震等非正常燃烧现象的发生,从氢气喷射技术、燃烧策略和空燃比控制策略、废气再循环技术、涡轮增压技术、氢气喷嘴技术和尾气后处理技术等方面,对氢内燃机的关键技术进行详细的分析。结果表明:大容量兆瓦级发电氢内燃机目前广泛应用的进气道喷射技术存在内燃机动力性差的弊端,采用缸内直喷技术可以有效提升动力性能,降低回火风险;采用稀薄燃烧可以降低爆震的风险;采用成熟的氨(NH_(3))-选择性催化还原(SCR)尾气后处理技术可以降低氮氧化物(NO_(x))的排放。

基于多种控制机理的湍流爆炸燃烧模型研究

本文针对狭长受限空间油气爆炸燃烧发生、发展过程特点,建立不同控制机理制约不同反应步的分步反应湍流燃烧模型。该燃烧模型的基本思想在于将化学反应分为两步进行,各步的控制机理不同,各步释放的能量也不同．采用分解、混合、反应的分步方式来模拟油气爆炸燃烧过程,通过实验和数值计算结果表明,该模型能较好解决湍流爆炸燃烧过程的数值模拟问题,其结果与实验吻合很好。