Simulation of the plasticizing behavior of composite modified doublebase(CMDB)propellant in grooved calendar based on adaptive grid technology

The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process.To improve the accuracy of the simulation results,material parameters and model structure were corrected based on actual conditions,and adaptive grid technology was applied in the local mesh refinement.In addition,the rheological behavior,motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps,rotational rates and temperatures of two rollers.The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet.Compared with the gap,the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging.Meanwhile,under the synergistic effect of contact heat transfer as well as convective heat exchange,heat accumulated near the outlet and diffused along the reflux movement,which led to the countercurrent heat dissipation behavior of CMDB propellant slurry.The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored,which provided theoretical guidance and reference data for the optimization of calendering process conditions.Based on the simulation results,the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle.

Effects of Nano-Aluminium on The Combustion of A PolyNIMMO-Based Propellant

Propellants containing micro-aluminium particles have been shown to produce faster burn rates than conventional gun propellants.However,they are also more abrasive than conventional propellants.Nano-material propellants have been reported to give similar benefits to micron-material propellants but without the disadvantage of increased abrasion.Tests were conducted to compare the burn rates,ignitability and wear rates of a propellant loaded with 0% aluminium,15% micro-aluminium and 15%nano-aluminium.Closed vessel tests showed a burn rate increase of 39% in the range 30-250 MPa,and 70% at low pressure(50-100MPa)for the nano-aluminium propellant compared with the baseline propellant.The micro-aluminium propellant showed only a 10%increase in the burn rate compared with the standard propellant.The ignition delay for the nano-aluminium propellant was slightly shorter than that of the baseline propellant.Substantially increased wear rates were measured for the micro-aluminium propellant.The nano-aluminium propellant showed reduced wear rates compared with the micro-aluminium propellant but these were still substantially greater than those for the baseline propellant.

Experimental study on thermal decomposition kinetics of natural ageing AP/HTPB base bleed composite propellant

The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning calorimetry(DSC). The naturally ageing AP/HTPB base bleed propellant samples have been stored in a sealed plastic bag at room temperature(5-25 ℃) for more than 20 years. The experimental DSC results were obtained by placing samples(each about 1.5 mg) in a sealed pan under non-isothermal condition under different heating rates, 5.0, 10.0, 15.0, 20.0 and 30.0 ℃·min^(-1). The activation energy and pre-exponential factor were estimated based on the relationship between the exothermic peak temperature and the heating rate by Ozawa and Kissinger methods, respectively. The decomposition kinetic parameters is lower the values under laboratorial aging condition.

Ballistic Testing and Thermal Behavior of Cast Double-base Propellant Containing BuNENA

Preparation of cast double-propellant grains depends on the ability of nitrocellulose powder to swell and coalesce into a coherent mass when treated with a suitable solvent.The cast double-base process has been developed into a highly versatile technique for manufacturing solid rocket charges.Propellants manufactured by this process provide a wide range of energies and burning rates.Successful preparation of cast double-base propellant grains has been performed using compatible casting liquid with the casting powder.BuNENA was used as an energetic plasticizer for manufacturing of casting powder.Burning rate measurements have been performed using closed bomb SV-2to investigate the burning behavior along a wide range of operating pressure.Plateau burning had been detected in pressure range(50-70)×105 Pa for the composition included BuNENA.DTA and TGA thermal analysis were conducted to evaluate the thermal behavior of the prepared cast double-base propellants.Results from DTA were used to calculate the apparent activation energy.

Novel aspects for thermal stability studies and shelf life assessment of modified double-base propellants

Modified DB propellants, based on energetic nitramine(RDX) were manufactured by solventless extrusion process. Thermal stability and shelf life assessment of modified DB propellant were investigated. Shelf life assessment was evaluated using Van’t Hoff’s formula and artificial aging at 70℃ up to120 days. Quantification of total heat released and heat flow with aging time was conducted using differential scanning calorimetry(DSC) and thermal activity monitoring(TAMIII) respectively. Modified DB formulation based on 20 wt % RDX demonstrated enhanced thermal stability in terms of controlled heat flow, and slow decomposition reactions at elevated temperature. This formulation demonstrated extended service life up to 56 years compared with reference formulation. These novel finding was ascribed to the high thermal stability of RDX and its compatibility with DB constituents. This manuscript shaded the light on novel and effective approach for thermal stability via monitoring thermal activity with aging.

Novel approach to quantify the chemical stability and shelf life of modified double-base propellants

Double-base(DB) propellant is vulnerable to auto-catalytic decomposition reactions during storing with the evolution of nitrogen oxides. Modified DB propellant based on energetic nitramines(RDX) can offer enhanced thrust and action time. This study is devoted to evaluate the impact of RDX on chemical stability and shelf life of DB propellant. Extruded modified DB propellant based on RDX was manufactured by solventless extrusion process. Shelf life assessment was performed using an artificial aging at70 ℃ up to 120 days and employing Van't Hoffs formula. Quantification of evolved NOx gases and stabilizer depletion with aging time was conducted using Bergmann-Junk test and HPLC respectively.Modified DB formulation based on RDX 20 wt % demonstrated enhanced chemical stability and extended service life up to 46 years compared with reference formulation. This finding was ascribed to the high chemical and thermal stability of RDX as well as its compatibility with DB constituents; no side chemical reactions could take place during storing. This manuscript shaded the light on RDX as effective energetic constituent that offered DB propellants with enhanced performance, good chemical stability, and extended service life.

Study on Influence of Functional Composition Distribution on Combustion Performance of a Modified Single Base Propellant

The modified single base propellant samples were prepared by impregnating blasting oil into single base grains and deactivating deterrent in water medium. The concentration distribution of functional compositions in this propellant was determined by using FTIR micro-spectroscopy. Its combustion performance was investigated by means of closed-bomb and interior ballistic tests. The results show that the concentration of NG distributes parabolically along the radius and the concentration of NA decreases from the surface to the centre exponentially. The deeper the NG impregnates, the slower the NA concentration decreases, the stronger the progressive combustion is and the better the interior ballistic performance is. When the depth corresponding to maximum NG concentration is about 1/2 of the web and the NA decreases slowly, the progressive combustion is the strongest and the interior ballistic performance is the best.

A Study of Estimating the Safe Storage Life, Self-accelerating Decomposition Temperature and Critical Temperature of Thermal Explosion of Double-base Propellant Using Isothermal and Non-isothermal Decomposition Behaviours

A method of estimating the safe storage life （τ）, self-accelerating decomposition temperature （TsADT） and critical temperature of thermal explosion （Tb） of double-base propellant using isothermal and non-isothermal decomposition behaviours is presented. For double-base propellant composed of 56±1wt% of nitrocellulose （NC）, 27±0.5wt% of nitroglycerine （NG）, 8.15±0.15wt% of dinitrotoluene （DNT）, 2.5±0.1wt% of methyl centralite, 5.0±0.15wt% of catalyst and 1.0±0.1wt% of other, the values of r of 49.4 years at 40℃, of TSAOT of 151.35℃ and of Tb of 163.01℃ were obtained.

Combustion Properties of Metal Particles as Components of Modified Double-Base Propellants

Metal particles such as aluminum（ Al）,magnesium（ Mg）,boron（ B） and nickel（ Ni）,as well as Mg/Al alloy（ Mg/Al = 3/4） are currently the most widely used ingredients in modified doublebase propellants. In this contribution,the combustion properties of the metal species are studied by means of the high-speed photography technique and the non-contact wavelet-based measurement of flame temperature distribution. The combustion process of the Al,Mg and Mg/Al samples shows both gas phase reaction and surface oxidation,which yield volatile and nonvolatile products,corresponding to the oxide and suboxide respectively. However,the combustion of B and Ni shows only gas phase reaction,due to their high melting point as well as high enthalpy of vaporization. In addition to the experiments,a hypothetical combustion model has been proposed to clarify the combustion characteristics of metal species in modified double-base propellants.

Distally based perforator sural flaps for foot and ankle reconstruction

Distally based perforator sural flaps from the posterolateral or posteromedial lower leg aspect are initially a neurofasciocutaneous flap that can be transferred reversely to the foot and ankle region with no need to harvest and sacrifice the deep major artery. These flaps are supplied by a perforating artery issued from the deep peroneal artery or the posterior tibial artery, and the chainlinked adipofascial neurovascular axis around the sural/saphenous nerve. It is a versatile and reliable technique for soft-tissue reconstruction of the heel and ankle region with 180-degrees rotation. In this paper, we present its developing history, vascular basis, surgical techniques including flap design and elevation, flap variations in pedicle and component, surgical indications, and illustrative case reports with different perforating vessels as pivot points for foot and ankle coverage.

新型HAN基液体推进剂EMP⁃01液滴电点火特性

为探究新型硝酸羟胺(HAN)基液体推进剂EMP‑01液滴点火特性,搭建了通过将液滴静置在半球形凹槽内并插入电极的液滴电点火实验平台,在液滴直径6.5 mm、电极间距0.5 mm、电压加载速率为86.31 V∙s-1的工况下,研究了EMP‑01液滴的电点火燃烧特性,确定了着火延迟时间;同时,不改变液滴直径以及电极间距,研究了电压加载速率为34.20~246.37 V∙s^(-1)时液滴着火延迟时间与燃烧过程的变化规律。结果表明,电点火燃烧中,EMP‑01液滴分依次经历为加热、热分解、燃烧3个阶段,并且在热分解阶段会产生周期性的膨胀收缩。电压加载速率为34.20 V∙s^(-1)时,EMP‑01液滴无法成功点火;电压加载速率为49.49~246.37 V∙s^(-1)时,随着电压加载速率增加,EMP‑01液滴着火延迟时间不断减小,且减小速率逐渐变缓。

HMX含量对PBT基推进剂撞击感度和非冲击点火反应特性的影响

为了研究HMX的含量对PBT基推进剂撞击感度和非冲击点火反应特性的影响,开展了BAM落锤撞击感度试验、脆性试验和Susan试验。结果表明:随着HMX含量的增加,PBT基推进剂爆炸概率为50%时的特性落高(H50)减小,即推进剂的撞击感度随着HMX含量的增加而增大。对于HMX的质量分数分别为0、5%、10%和15%的PBT基推进剂,其临界撞击点火速度分别为168、147、136、131 m/s,临界撞击点火速度随HMX含量的增加而减小;在撞击速度为120~300 m/s的非冲击作用下,4种PBT基推进剂的反应等级为爆炸或部分爆轰,相同撞击速度下,HMX的质量分数为10%的PBT基推进剂相较于其他3种PBT基推进剂具有更剧烈的反应等级。

降速剂及其作用位点对丁羟四组元推进剂燃烧性能的影响规律

为研究降速剂对丁羟四组元推进剂燃烧性能的影响规律,将典型季铵盐和金刚烷衍生物两种高效降速剂引入核壳结构铝基复合颗粒Al@HMX和AP@Al,使其分别作用于HMX颗粒内部和AP颗粒表面,制备了4种含降速剂的铝基复合颗粒(Al/A@HMX,Al/B@HMX,AP@Al/A和AP@Al/B);采用扫描电子显微镜对样品形貌进行了表征;采用高速红外相机拍摄推进剂燃烧过程的火焰红外照片,并对推进剂的爆热、密度、点火延迟时间和燃速进行了测试。结果表明,加入惰性降速剂会导致推进剂爆热降低,而Al@HMX复合颗粒能部分抵消这一现象,使推进剂爆热值增加了338 J/g;降速剂能够抑制AP和HMX的热分解过程,使达到AlO辐射峰值前维持低强度的“平台段”;而引入Al@HMX后,推进剂的点火延迟时间比基础配方减小49.4%;在10~20 MPa范围内两种降速剂均能有效降低推进剂燃速,在此基础上采用Al@HMX可使含季铵盐丁羟四组元推进剂20 MPa下的燃速降低7.1 mm/s(38.4%),压强指数降至0.25;当降速剂作用于AP表面时,含质量分数1%季铵盐的推进剂在20 MPa下燃速可降低5.0 mm/s(27.3%)。

含添加剂水雾抑灭单基药火焰的小尺度实验研究

为探究含不同性质添加剂的水雾对单基火药燃烧抑灭性能的影响,在自主搭建的火药燃烧及灭火平台上开展纯水雾与含Na_(2)SO_(3)、FeCl_(2)、K_(2)CO_(3)、KHCO_(3)添加剂的水雾对单基火药燃烧抑灭性能的对比实验,研究灭火过程中温度、辐射热流、火焰形态等的变化。结果表明:含还原性(Na_(2)SO_(3)、FeCl_(2))和非还原性(K_(2)CO_(3)、KHCO_(3))添加剂的水雾抑灭性能明显优于纯水雾,灭火时间更短。含非还原性添加剂的水雾在低浓度下抑灭效果较差,当添加质量分数提升至3%以上时,抑灭效果显著提升;含还原性添加剂水雾对单基药的抑灭性能在各添加剂浓度下均优于含非还原性添加剂的水雾,且随着添加剂浓度的增大,抑灭性能表现出饱和性。

HAN-基凝胶推进剂的热分解反应动力学（英文）

为研究HAN-基凝胶推进剂的热分解特性,利用差示扫描量热仪(DSC)和热重分析仪(TGA)对两种含不同质量聚乙烯醇(PVA)的HAN-基凝胶推进剂样品进行热分析试验,并与一种双基推进剂进行对比。分析了HAN-基凝胶推进剂和双基推进剂的热分解过程,得到热分解反应的动力学参数;采用等转化率法计算了活化能,采用Zhang-Hu-Xie-Li等方法计算出热爆炸临界温度和自加速分解温度。采用Malek法推断出两种HAN-基凝胶推进剂样品的热分解反应的最可几机理函数。结果表明,HAN-基凝胶推进剂的热分解是一个连续的放热过程,热分解较为彻底,残渣较少,活化能约为100kJ/mol。当PVA含量增加时,其热爆炸临界温度和自加速分解温度升高。与双基推进剂相比,HAN-基凝胶推进剂具有较好的热安定性。

甲基紫试验中改性双基推进剂的热分解机制研究

目的 研究甲基紫试验中含Al改性双基推进剂以及含RDX改性双基推进剂2种典型改性双基推进剂的热分解机理。方法 将这2种典型改性双基推进剂与普通双基推进剂进行对比试验,采用TG-DSC-FTIR-MS联用技术,通过对分解温度、放热量、分解产物等特征参数进行分析,明确3种推进剂的非等温热分解行为。采用微热量热法,在与甲基紫试验相同温度下对3种推进剂进行等温热分解行为研究。结果 含Al改性双基推进剂在程序升温条件下的热质量损失和热分解行为与普通双基推进剂的基本一致。含RDX改性双基推进剂中的NG较其他2种推进剂更易挥发,相应分解反应初期NG分解释放的NO_(2)较少,且在整个热分解反应历程中分2个阶段,含硝酸酯基团的NC/NG体系先分解,再引起硝铵炸药RDX的热分解。在等温条件下,3种推进剂在40 min对应的反应深度均不超过0.4%,5 h对应的反应深度均不超过3%。但在分解反应初期,含Al改性双基推进剂分解反应的速率更快。结论 对比不同推进剂甲基紫安定性试验结果,并不是甲基紫试纸完全变色时间越长的热安定越好,说明甲基紫安定性试验方法存在一定的局限性。采用分解反应深度作为量气和量热方法转换的纽带,有望采用微热量热作为甲基紫试验的替代技术实现安定性的定量评价。

固体火箭超燃冲压发动机点火燃烧过程实验研究

为解决硼基贫氧燃料固体火箭超燃冲压发动机补燃室内硼颗粒超声速点火燃烧难题,设计制造了在超声速燃气射流掺混区域开设观察窗的点火燃烧过程试验样机,开展了含硼贫氧固体燃料的超声速点火试验。试验模拟了26 km,Ma5.9的飞行工况并通过高速摄像获得了点火燃烧过程的火焰形态。试验结果表明:掺混增强装置可以显著改善补燃室内存在的分层流动和一次燃气气固两相分离的现象,为硼颗粒提供良好的点火条件从而提升其附近硼颗粒的点火燃烧性能。通过合理设计掺混增强装置位置,将硼颗粒在一次燃气喷注口附近的高温点火区点燃比在补燃室中段点燃具有更高的燃烧效率,本文设计的燃烧组织结构在试验中实现了硼贫氧固体燃料0.812的燃烧效率。

SC-CO_(2)辅助挤出成型过程中双基发射药的流变特性

为了部分替代在发射药挤出成型过程中使用的有机溶剂,将超临界二氧化碳(Supercritical Carbon dioxide,SC-CO_(2))引入发射药的挤出成型过程中,借助其在临界点附近急剧变化的溶剂特性,实现增塑后可快速从产品中驱除,为最终实现SC-CO_(2)对有机溶剂的完全替代做铺垫。以剪切黏度为反映流变特性的参数,采用在线狭缝流变仪测量物料的剪切黏度并获得流变曲线,对物料在不同工艺条件下的流变特性进行研究。研究结果表明:SC-CO_(2)辅助双基药挤出成型过程中物料的流变行为可以用幂律模型描述,引入SC-CO_(2)后物料黏度显著降低,SC-CO_(2)在4.67 wt%含量下使得双基药的稠度系数降低17.10%,体现了SC-CO_(2)对于双基药的良好增塑作用;随着SC-CO_(2)含量、溶剂含量、温度等参数值持续升高,继续增大参数值所能提供的增塑效果将变得有限。

2/1樟单基发射药的真空与非真空环境安定性试验可替代性研究

基于深空探测用单基发射药在外太空中要经受长时间真空、温度交变等复杂的太空环境,而现有标准的安定性评估方法对其不适用的情况,设计了2/1樟单基发射药在75℃高温真空和非真空条件下的对比试验,测试双环境应力下药剂的安定剂含量、热分解性能及药剂成分等安定性敏感参量。结果表明:在试验周期10d内,药剂在75℃真空和非真空的试验环境下,其二苯胺含量、分解温度和氮含量等参数无显著性差异。本研究可为单基发射药在复杂多变环境下的安定性评估提供参考。