NEPE推进剂的燃烧转爆轰特性

介绍了燃烧转爆轰的研究方法、表征参数和影响因素.用DDT管、光电管、应变片、验证板研究了NEPE推进剂混合过程中的燃烧转爆轰特性.研究结果表明,NEPE推进剂药浆的诱导爆轰距离与其在DDT管中的装填密度存在典型的U形曲线关系;当实际装填密度大于理论装填密度的95%时,NEPE推进剂药浆在试验条件下无法发生燃烧转爆轰,同时,NEPE推进剂药浆的诱导爆轰距离与DDT管的破碎程度具有较好的相关性,诱导爆轰距离越小,DDT管的破碎程度越严重.由于立式混合机的密闭性及混合过程中推进剂药浆的不均匀性,NEPE推进剂在混合过程中存在燃烧转爆轰的可能性.     

含ACP改性双基推进剂的燃烧转爆轰实验研究

为研究快燃物ACP对改性双基推进剂燃烧转爆轰性能的影响,利用DDT管建立相应的测试系统,对推进剂在多孔装药条件下的燃烧转爆轰过程进行了实验研究.实验中采用电离探针和压电式压力传感器记录了燃烧与爆轰波阵面的位置一时间关系和压力波形图,利用实验结果计算并比较了波阵面的传播速度、爆轰形成点的位置以及药床不同位置的压力值.结果表明,快燃物ACP能够增大改性双基推进剂转爆轰的倾向,当ACP的质量分数从5%增加到7%时,装药燃烧转爆轰的倾向增大比较明显.     

p(BAMO-AMMO)热塑性高能推进剂燃烧转爆轰试验研究

采用燃烧转爆轰(DDT)管法研究了p(BAMO-AMMO)热塑性推进剂主要固体组分RDX和AP含量、AP粒度及级配等对其燃烧转爆轰响应规律的影响。结果表明,在相同试验条件下,含质量分数65%AP的p(BAMOAMMO)推进剂发生了燃烧转爆轰响应,而含等量RDX的p(BAMO-AMMO)推进剂仅发生了燃烧反应。当RDX质量分数从65%增加到85%时,样品由燃烧反应变为燃烧转爆轰反应。含等量细粒度(d50=1.0μm)AP的推进剂发生燃烧转爆轰的倾向较含粗粒度AP(d50=105μm)的低。当粗、细AP以质量比为10∶3级配时,p(BAMOAMMO)推进剂未发生燃烧转爆轰反应。     

Effect of Temperature,Density and Confinement on Deflagration to Detonation Transition of an HMX‐Based Explosive

In order to obtain the characteristics of the deflagration‐to‐detonation transition (DDT) of PBX‐2 (an HMX‐based explosive) under different conditions, DDT tests were carried out as a function of charge density, temperature, and shell confinement. In these tests, the energetic materials were electrically ignited. The DDT response characteristics for PBX‐2 with 53 % and 99 % of theoretical maximum density (TMD) were evaluated by different shell thickness confinements at ambient temperature and at 85 °C. The test results with different densities, confinements and temperatures exhibited a wide range of reaction violence. Firstly, at both ambient temperature and at 85 °C under 10 and 20 mm shell thickness confinement, PBX‐2 did not undergo fully DDT at 99 % TMD, only a low velocity detonation (LVD) occurred. Secondly, PBX‐2 at 53 % TMD underwent DDT, and significant influence on the minimum run distance to detonation by the shell confinement thickness was observed. Strong confinement is favorable for the transition of DDT but the confinement does not influence reaction degree. Thirdly, the reaction degree of PBX‐2 at 85 °C was remarkably lower than that at ambient temperature. This insensitizing effect of temperature is induced by the melting and flowing of bonders which reduces the porosity and inhibits an important step of DDT, namely, high turbulent combustion.     

Laser‐induced Deflagration for the Characterization of Energetic Materials

Standard propellant and detonation tests typically performed to characterize the performance of energetic materials require large quantities of material (at least tens of grams) and can be expensive and time‐consuming. This work introduces a method for characterizing the deflagration of energetic materials in a laboratory setting, using only 15–20 mg of energetic material. Temperature, energy release and emission signatures were measured and analyzed for the laser‐induced deflagration of 8 different conventional military explosives. Graphite nanoparticles and micron‐sized aluminum powder were added to the explosive compositions to investigate their effect on the emission signatures. A high‐speed color camera recorded the deflagration events and was utilized as a full‐color pyrometer to calculate the average temperatures and image hotspots; the temperatures maps were compared to those measured by conventional two‐color pyrometry. The laboratory‐scale method presented here can be applied to novel energetic materials under development that may be available only in limited quantities to evaluate their potential as propellants or reduced emission signature explosives prior to scale‐up.     

Research on Preparation of Perfusion Explosive Using Foamed SF‐3 Double‐Base Propellant

Perfusion explosives were prepared using foamed SF‐3 propellants, which were synthesized by a two‐stage batch foaming process with different saturation time in supercritical fluid CO₂ as a foaming agent. The foamed SF‐3 propellants were characterized by scanning electron microscopy (SEM). Underwater detonation tests and test‐board detonation tests were carried out to investigate detonation performance of the prepared perfusion explosives. Results showed that more saturation time during the foaming process leads to more pores and cracks. Perfusion explosives prepared using foamed SF‐3 propellants exhibited much higher shock wave energy and stronger damage effectiveness than those using unfoamed SF‐3 propellants. Perfusion explosives prepared using foamed SF‐3 propellants with a saturation time of 2 h exhibited the highest shock wave energy and damage effectiveness, which decreased as the saturation time increased.     

Burning Characteristics of Ammonium Nitrate‐based Composite Propellants Supplemented with Ammonium Dichromate

Ammonium nitrate (AN)‐based composite propellants have attracted much attention, primarily because of the clean burning nature of AN as an oxidizer. However, such propellants have some disadvantages such as poor ignition and low burning rate. Ammonium dichromate (ADC) is used as a burning catalyst for AN‐based propellants; however, the effect of ADC on the burning characteristics has yet to be sufficiently delineated. The burning characteristics of AN/ADC propellants prepared with various contents of AN and ADC have been investigated in this study. The theoretical performance of an AN‐based propellant is improved by the addition of ADC. The increase in the burning rate is enhanced and the pressure deflagration limit (PDL) becomes lower with increasing amount of ADC added. The increasing ratio of the burning rate with respect to the amount of ADC is independent of the AN content and the combustion pressure. The optimal amount of ADC for improving the burning characteristics has been determined.     

Burning Rate – Pressure Relationship of NG‐PE‐PCP‐based High Energy Propellants

Nitramines are known to produce lower burning rates and higher pressure exponent (η) values. Studies on the burning rate and combustion behavior of advanced high‐energy NG/PE‐PCP/HMX/AP/Al based solid propellant processed by slurry cast route were carried out using varying percentages of HMX and AP. It was observed that propellant compositions containing only AP and Al loaded (total solids 75 %) in NG plasticized PE‐PCP binder produce comparatively lower pressure exponent (η) values similar to AP‐Al filled HTPB based composite propellants. However, energetic propellants containing high level of nitramine (40–60 %) produce high pressure exponent (0.8–0.9) values in the same pressure range. Incorporation of fine particle size AP (ca. 6 μm) and change in its concentration in the propellant composition reduces η value marginally and influences the burning rate. However, such compositions have higher friction sensitivity.     

几种典型固体推进剂的燃烧转爆轰实验研究

为探索影响固体推进剂发生燃烧转爆轰的因素,对4种典型固体推进剂样品进行了实验研究。通过选用不同壁厚的样品管及改变样品的装填形式,实现了燃烧转爆轰。利用电离探针对试样稳定爆轰时的爆速进行了测试。结果表明,含RDX、NG高敏感度含能材料的颗粒状CMDB推进剂及药柱内部含有大量气孔的NEPE推进剂发生燃烧转爆轰。推进剂的配方、装药形式、外界约束条件是影响推进剂发生燃烧转爆轰的主要因素。证明了推进剂在特定条件下可以发生燃烧转爆轰。     

铝粉-空气混合物的燃烧转爆轰过程

利用自行设计的长29.6 m、内径199 mm配有40套喷粉扬尘装置的大型水平爆轰管,研究了细片状铝粉-空气混合物在40 J弱点火条件下火焰从发生到加速、最后实现爆轰转捩的全过程,探讨了铝粉浓度和点火延迟时间对爆轰参数的影响.结果表明,铝粉-空气混合物燃烧转爆轰(DDT)过程可分为慢速反应压缩阶段和快速反应冲击阶段.当点火延迟时间为370 ms,铝粉质量浓度为300 g/m~3时,在管道中距离点火位置83倍长径比处峰值超压为9.8 MPa,爆速为1 670 m/s,发生了DDT过程.在铝粉-空气混合物自持爆轰波的传播过程中,由于呈现螺旋爆轰波结构,爆速和峰值超压随着传播距离振荡.     

Ballistic Modification of Nitramine Propellants with Special Reference to NG‐PE‐PCP‐Based High Energy Propellants

The burning rate pressure relationship is one of the important criteria in the selection of the propellant for particular applications. The pressure exponent (η) plays a significant role in the internal ballistics of rocket motors. Nitramines are known to produce lower burning rates and higher pressure exponent (η) values. Studies on the burning rate and combustion behavior of advanced high‐energy NG/PE‐PCP/AP/Al‐ and NG/PE‐PCP/HMX/AP/Al‐based solid rocket propellants processed by a conventional slurry cast route were carried out. The objective of present study was to understand the effectiveness of various ballistic modifiers viz. iron oxide, copper chromite, lead/copper oxides, and lead salts in combination with carbon black as a catalyst on the burning rate and pressure exponent of these high‐energy propellants. A 7–9 % increase in the burning rates and almost no effect in pressure exponent values of propellant compositions without nitramine were observed. However, in case of nitramine‐based propellants as compared to propellant compositions without nitramines, slight increases of the burning rates were observed. By incorporation of ballistic modifiers, the pressure exponents can be lowered. The changes in the calorimetric values of the formulations by addition of the catalysts were also studied.     

发射药燃烧转爆轰的试验研究

为研究发射药燃烧转爆轰特性及其影响因素,采用联合国危险分级试验中燃烧转爆轰试验方法对单、双、三基以及不同药型的发射药进行燃烧转爆轰试验。结果表明,在管厚4mm弱约束条件下,只有三基小粒发射药发生爆轰,在管厚9mm强约束条件下,6/7双基药、6/7叠氮发射药、6/7三基药以及三基小粒药发生爆轰。发射药配方中添加硝化甘油(NG)、叠氮硝胺(DA)和黑索金(RDX)以及减小药型尺寸,可增强发射药的燃烧转爆轰能力,同时,提高壳体约束强度更易发生燃烧转爆轰。     

Studies into Laser Ignition of Unconfined Propellants

Prior to laser ignition tests, spectral absorption properties of three different solid motor propellants were analysed. The extruded double base (EDB) propellant exhibited >95 % absorption over the 250–550 nm wavelength band whereas, the cast double base (CDB) showed similar absorption over a wider band extending between 375–800 nm. The composite sample (CP) showed a uniform spectral absorption at about 90 % over 250–800 nm band. Ignition tests using an average of 500 nm output from an Ar‐ion laser showed that the double base propellants undergo deflagration prior to ignition due to the presence of carbon black material. Within the laser power density range of 24–125 Wċcm⁻², the threshold laser energy densities for deflagration and ignition in the double base propellant were found to␣be between 2–2.5 Jċcm⁻², and 40–215 Jċcm⁻², respectively. No deflagration was observed for the composite propellant, and the threshold ignition energy was found to be within the range, 11–18 Jċcm⁻² for the same range of laser power densities. From the ignition map for this propellant, the threshold energy for ignition at this wavelength was found to be approximately 18 Jċcm⁻² and was practically independent of laser power density. In the near infrared wavelength (780 nm) the EDB propellant was not readily ignitable due to its comparatively much higher reflectance at this wavelength. The ignition threshold values were found to be between 19–23 Jċcm⁻² for a similar power density level. The results indicate that the ignitability of propellants is enhanced through the promotion of deflagration.     

Synthesis and Application of Borate Ester Bonding Agents for a Four‐Component Hydroxy‐Terminated Polybutadiene Propellant

Low molecular weight interconnection monomers including polyepichlorohydrin, poly(propylene oxide), poly(ethylene glycol adipate), and poly(butylene adipate) were synthesized to evaluate the effects of the molecular structure of interconnection monomers on the bonding efficiency of borate ester bonding agents (BEBA) applied in four‐component hydroxy‐terminated polybutadiene (HTPB) propellants. The monomers were characterized by IR spectroscopy, elemental analysis, and gel permeation chromatography. A series of new borate ester bonding agents were synthesized using the as‐synthesized interconnection monomers as well as poly(ethylene glycol) and applied in the preparation of four‐component HTPB propellants. The application results showed that BEBA‐4 prepared from poly(butylene adipate) could significantly improve the mechanical properties of the four‐component HTPB propellant, reduce the slurry viscosity leading to improvement of processing properties and aging resistant performance, while no significant effect on the burning characteristics of the propellant was observed.     

4,5‐Bis(5‐tetrazolyl)‐1,2,3‐triazole: Synthesis and Performance

4,5‐Bis(5‐tetrazolyl)‐1,2,3‐triazole (BTT) was synthesized by a new method. Its structure was characterized by IR and ¹³C NMR spectroscopy and elemental analysis (EA). The thermal stability of BTT was investigated by TG‐DSC technique. The kinetic parameters including activation energy and pro‐exponential factor were calculated by Kissinger equation. The combustion heat, detonation products, hygroscopicity, impact, and friction sensitivity were also measured. The formation heat, detonation pressure, and detonation velocity of BTT were calculated. BTT has high detonation pressure and detonation velocity (P=35.36 GPa, D=8.971 km s⁻¹). BTT has potential application prospect as environmentally friendly gas generant, insensitive explosive and solid propellant.     

Non‐Isothermal Kinetic Study of the Thermal Decomposition of Melamine 3‐Nitro‐1,2,4‐triazol‐5‐one Salt

Study on thermal behavior of 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) salts was required to obtain important data for application purposes. These compounds have been shown to be useful intermediates for gun propellant ingredients, high energetic ballistic modifiers for solid propellants and other potential applications. In this paper, thermal decomposition and non‐isothermal kinetics of melamine 3‐nitro‐1,2,4‐triazol‐5‐one salt (MNTO) were studied under non‐isothermal conditions by DSC and TG methods. The kinetic parameters were obtained from analysis of the DSC and TG curves by Kissinger and Ozawa methods. The critical temperature of thermal explosion (T_b) was 574 K. The results show that MNTO is thermally more stable than NTO when compared in terms of the critical temperature of thermal explosion. Finally, the values of ΔS^#, ΔH^#, and ΔG^# of its decomposition reaction were calculated.     

Research on Perfusion Explosives from SF‐3 Double‐Base Propellants Using Supercritical CO2

Perfusion explosives were prepared using porous SF‐3 propellants, which were synthesized by a supercritical fluid foaming process. Scanning electron microscopy (SEM) was used to characterize the porous SF‐3 propellants. Massive holes were generated after the foaming process. The density of perfusion explosives using foamed SF‐3 propellants exceeds 1.3 g cm⁻³, and the detonation velocities exceed 6000 m s⁻¹. Underwater energy tests and high‐speed photography were carried out to investigate the detonation performance of perfusion explosives. The results showed that perfusion explosives using unfoamed SF‐3 propellants could not be detonated. However, perfusion explosives using their foamed analogs could be detonated herein.     

Characterization of ADN/GAP‐Based and ADN/Desmophen®‐Based Propellant Formulations and Comparison with AP Analogues

Several ADN‐based rocket propellant formulations containing different pre‐polymers (GAP diol/triol, Desmophen® 2200), curing agents (BPS, Desmodur® N100, Desmodur® N3400), plasticizers (BDNPA‐F, TMETN), and filler types (Al, HMX) have been manufactured. Propellant formulations were characterized by tensile tests, SEM analyses and DMA measurements. The study has focused on characterizations of the propellants in terms of evaluation of the strength and strain capability, investigation of the presence/absence of dewetting phenomena, compatibility issues and evaluation of the glass transition temperature. Ammonium perchlorate‐based propellant formulations have also been manufactured and analyzed in order to make comparisons. Aging was investigated using mass loss measurements.     

Research on Titanium‐Containing Micro‐Porous Propellants with Rapid Burning Rate

Micro‐porous propellants containing titanium powder were obtained by supercritical CO₂ (SC CO₂) foaming technique. The morphologies of the micro‐porous propellants were characterized by scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS) measurement. The burning rate, the impetus, and the heat of explosion of the micro‐porous propellants were measured by the closed vessel test and the calorimetric bomb test. The results show that the porosity increased with increasing titanium powder content; compared with Benite, the burning rate was substantially improved, and the maximum values of the impetus and the isochoric heat of explosion increased by 51.4 % and 6.5 %, respectively. The Ti‐containing micro‐porous propellants with rapid burning rate and better energetic properties described in this paper may have the potential to replace Benite as igniter material in a flame igniter of a gun propellant charge.     

Formulation and Characterization of a New Nitroglycerin‐Free Double Base Propellant

Double base propellants composed of nitrocellulose (NC) and nitroglycerine (NG) are widely used. However, the inclusion of liquid NG presents both stability and performance problems: the NG may migrate from the propellant in storage, and it softens the propellant at high inclusion levels. In this work, the novel nitrate ester 1,4‐dinitrato‐2,3‐dinitro‐2,3bis(nitratomethylene) butane (SMX) is considered as a replacement for NG in a double base propellant. Thermochemical calculations indicate improved performance when compared with the common double base propellant JA2 at SMX loadings above 40 wt‐%. Also, since SMX is a room temperature solid, migration may be mitigated. Both unplasticized and plasticized propellants were formulated to enable the study of the interaction of SMX with nitrocellulose. Thermal analysis of unplasticized propellant showed a distinct melt‐recrystallization curve, which indicates that a solid phase solution is being formed between SMX and NC, and that SMX would not act as plasticizer. Analysis of propellant prepared with diethyleneglycol dinitrate (DEGDN) plasticizer indicates that the SMX is likely dissolved in the DEGDN. The plasticized material also showed similar hardness and modulus to JA2. Safety characterization showed that sensitivity is similar to JA2. In short, replacing NG with SMX results in a new family of propellants with acceptable safety characteristics and which may also offer improved theoretical performance.