Development of reverse phase HPLC techniques for determination of stabilizer depletion rates in high energy gas generator propellants

Abstract

Reverse phase high performance liquid chromatographic methods have been developed for determining the stabilizer content in a nitrate ester plasticized gas generator propellant. The accuracy and precision of these methods are demonstrated by the results of stabilizer depletion rate determinations obtained over a three month accelerated aging period. The stabilizers investigated included diphenylamine (DPA), 2-nitrodiphenylamine (2-NDPA), 4-nitrodiphenylamine (4-NDPA), resorcinol and ethyl centralite (EC). Details of the analytical technique and methods development will be discussed.     

Detonation properties of ammonium nitrate/nitramine-based composite propellants

ABSTRACT

Ammonium nitrate (AN) propellants have attracted attention because of their low cost and ecofriendliness despite certain major disadvantages such as low burning rate, poor ignitability, low energy, and volume change due to phase transition of AN. The addition of nitramine to AN propellants is one of the approaches to overcome these disadvantages. However, AN/nitramine propellants are characterized by easy initiation, high sensitivity, and high detonation velocity because of the high energy of nitramine. The detonation properties of AN/nitramine propellants were investigated in this study. It was observed that the AN/nitramine propellant required a booster to detonate the propellants, as detonation did not occur while using only a commercial electric blasting cap. It was further observed that the detonation velocity (D) increased linearly as the mass of nitramine per unit propellant volume was increased, and AN had a negligible effect on the detonation properties. An approximate equation was derived from the relationship between D and the mass per unit propellant volume of nitramine. The dominant factors that can be used to estimate the detonation/no-detonation boundaries of the propellants were identified, and the experimental boundary equations were determined using these factors.     

Safety assessment studies of a damaged high-energy solid propellant

Abstract

This article presents a study of the effects of damage on the thermal decomposition, combustion and deflagration-to-detonation transition (DDT) of the NEPE (Nitrate Ester Plasticized Polyether) propellant in order to assess its safety. The study includes: (1) to induce damage into the propellants by means of a large-scale drop-weight apparatus; (2) to observe microstructural variations of the propellant with a scanning electron microscope (SEM); (3) to investigate thermal decomposition tests; (4) to carry out closed-bomb tests and (5) to perform DDT tests. The NEPE propellant is found to be a viscoelastic material. The matrices of damaged samples are severely degraded, but the particles are not. The results of the thermal decomposition tests, closed-bomb tests and DDT tests show that the microstructural damage in the propellant has some marked effects on its thermal decomposition rate, bum rate and transition rate from deflagration to detonation. It is shown that the impact damage strongly influences on safety properties of the NEPE propellant.     

Combustion mechanism of the low signature propellant containing 1,7-diazido-2,4,6-trinitrazaheptane(dath)

Abstract

The thermal decomposition behavior of the low signature (LS) propellant containing 1,7-diazido-2,4,6-trinitrazaheptane(DATH) is investigated by DSC, TG and DTG technique. Several analysis methods are used to study the physico-chemical structure of surface before and after combustion and the burning flame structure of this kind of propellant. Because DATH decomposes to produce a great quantity of N₂, the physico-chemical structure of burning surface of the propellant is obviously different from that of RDX-CMDB (Composite Modified Double-Base) propellant. It's mainly N₂, that gives rise to forming a lot of pores on the burning surface for its release. These pores can increase the burning rate because of extending the burning surface and increasing thermal-transfer intensity. In comparison with decomposition and combustion process of RDX-CMDB propellant, the propellant containing DATH creates the different decomposition products from the condensed phase to the fizz zone.     

The solubility of gases under pressure in liquid propellants

Abstract

A corresponding states correlation has been developed for the solubility of pure gases and mixtures in LGP 1846, a HAN based liquid propellant [1]. For nitrogen, methane, xenon, krypton, and argon, and their mixtures the correlation can be used to estimate gas solubilities for pressures upto 100 MPa in the temperature range 258 < T < 303 K. The correlation is in satisfactory agreement with all available experimental data for these systems. Dissolved gases are expected to significantly effect many physical and chemical properties of liquid propellant systems.     

Mechanical and thermomechanical properties of NC base propellants

Abstract

Compressive mechanical properties have been investigated as a function of temperature and strain rate for a modified'' double-base propellant (JA2) and comparison made with similar studies for a triple-base propellant. Measurements were made at strain rates of 10 sec.^?1 and 10^?3 sec.^?1 and temperatures of 80°C to -60°C. At the higher strain rate the double-base propellant shows ductile behavior at 20°C and brittle failure at the low temperature. However, comparison with triple-base propellants indicates that this double-base propellant is much less brittle at the lower temperature and considerably less fragmentation is observed for the double-base propellant. While the ductile-to-brittle transition can be related to a glass type transition temperature, the difference in fragmentation is apparently related to composition and structure. The relationship of ductile and brittle failure to abnormal burning and the related unsafe gun firing conditions is discussed.     

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液体药火药高能气体压裂是利用以氧化剂、燃烧剂、溶剂，添加适量的燃烧敏化剂为主要组分，配制成液体状的高能材料，进行油气井增产、增注作业的一种高能气体压裂技术。文章就液体药氧化剂、燃烧剂的选择、液体药的配方，经优化设计计算，找出了适合现场应用的液体药组成；文中还对液体发射药点火和燃烧性能进行了论述，研究了现场井下液体药点火工艺和点火药量。由于液体发射药燃速慢，最高压力仅50～60 MPa，井下装填药可达500～1200 kg，压力持续时间40 s左右。由于其压力持续时间长，因此可以造成宽长裂缝，缝长可达25~50 m，与水力压裂缝长相近。增产比为2.5~5，有效期达6个月以上，特别适用于低渗油气藏致密油层的压裂。文中介绍了液体药现场试验的结果及其取得的地质与经济效益。     

Tuning the thermal,mechanical, and combustion properties of NC-TEGDN-RDX propellants via incorporation of graphene nanoplates

ABSTRACT

Graphene nanoplates (GNPs) were incorporated into a solid composite propellant (NC-TEGDN-RDX) to tune the thermal, mechanical, and combustion properties of the material. Physical, thermal, and combustion properties of NC-TEGDN-RDX with <2 wt% addition of GNPs were characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile/compressive/impact strength testing, and constant volume combustion experiments. Microstructure of the composite propellants examined using SEM demonstrated uniform dispersion of the GNPs at low-weight percent additives (<1 wt%), but began to show large agglomerations of the additives at higher additive content. Decomposition enthalpy of the propellant with 1 wt% GNPs increased by ~130 J/g compared to neat propellants. Moreover, the maximum burning rate was observed for samples containing 1 wt% GNPs, with values of 19 cm/s at 20°C and 17 cm/s at ?40°C. Dynamic vivacity of the propellant achieved a maximum upon addition of 1 wt% GNPs. The pressure exponent of the propellant decreased with the addition of GNPs, as well. The mechanical properties including tensile, compressive, and impact strength were improved at 20°C and ?40°C. These results demonstrate that the addition of GNPs may offer new methods by which to tune and improve thermal decomposition, thermal conductivity, combustion performance, and mechanical properties of the NC-TEGDN-RDX propellants.     

Development of high burn rate azide polymer propellant

Abstract

The combustion characteristics of high burn rate azide polymer composite propellant were examined by using ? 70 mm BMI composite rocket motor of L/D = 16. Azide polymer propellants have much higher specific impulse than HTPB propellant at below the AP content of 85%. AP/B/N propellants showed a plateau-mesa burning at a pressure range between 7 MPa and 15 MPa with a burn rate of approximately 28 mm/s. Very fine AP, however, diminished this favorable combustion characteristics. The AP/B/N also had excellent mechanical properties at an operational temperature range to enable the case bonded. The BMI motors burned stably and showed an excellent performance. The thickness of the insulation at the aft closure, 5.5 mm including a stress relief boot, was good enough.     

Formulation and Comparative Study of Rheological Properties of Loaded and Unloaded Ethanol-Based Gel Propellants

The current trend in the area of highly energetic storable liquid rocket propellant research is to develop environmentally friendly gelled/metallized systems and to explore the feasibility of their application in rocket engines. The idea stems from the fact that the conversion of a conventional liquid propellant to a gelled state and its subsequent metallization has the potential to significantly enhance the performance and density-specific impulse. The gelation of liquid fuels could be induced at a critical gellant concentration of as low as 8 wt% for the pure ethanol case and as low as 4 and 6 wt% for metallized ethanol depending on the metal type. Furthermore, the gel formed should be thixotropic. Metallized gels using 20 wt% Al and B metal powders could also be formulated. These metallized (Al and B) ethanol gel systems showed a reduction in the critical gellant concentration depending on the degree of metallization. The rheological properties of metallized and nonmetallized ethanol gels using methyl cellulose (MC) as a gelling agent at different ambient temperatures (283.15, 293.15, 303.15, 313.15, and 323.15 K) were experimentally investigated in this study. The gel fuels were rheologically characterized using a rheometer at shear rates ranging from 1 to 12 s^?1 and 1 to 1,000 s^?1. Metallized and nonmetallized ethanol gels were found to be thixotropic in nature. The apparent viscosity and yield stress (for shear rate range 1 to 12 s^?1) of gels were observed to significantly decrease at higher ambient temperatures and as the gellant and metal particle concentrations decreased. The thixotropic behavior was found to be a strong function of the Al and B metal particle concentration for all test temperatures at shear rate ranges from 1 to 12 s^?1 and 1 to 1,000 s^?1. It was also a function of the MC concentration at a shear rate range of 1 to 1,000 s^?1.     

Hydrolysis of the energetic materials present in a composite modified double base solid rocket propellant

Abstract

The aqueous hydrolysis of the nitroglycerin (NG), nitrocellulose (NC), and HMX present in CYH, a composite modified double base solid propellant, was successfully performed using either sodium hydroxide (NaOH) or ammonia (NH₃) as hydrolyzing agents. The rate of hydrolysis was faster for NaOH compared to NH₃. For both hydrolysis agents the rate of hydrolysis of NG was the fastest, followed by NC and then HMX. It was determined that 4 parts of NaOH were required to hydrolyze the energetic ingredients in 10 parts of CYH. A similar determination was not made for NH₃.

The original set of experiments were done on a small scale (0.030-10 grams of propellant) with laboratory glassware. Later experiments involved the hydrolysis of larger amounts of propellant (200 grams), again using laboratory glassware. The last set of experiments were accomplished with a small scale glass reactor (4 liters) with up to 900 grams of propellant per run. In addition, exhaustive chemical analysis yielded useful information about the hydrolysis products. The combined data was used to design a reactor for the hydrolysis of 4,000 Ibs of CYH propellant.     

Rheological and wall-slip behaviour of composite propellant suspension containing Al-nanopowder

ABSTRACT

Hydroxyl terminated polybutadiene composite propellant suspension mainly containing ammonium perchlorate (70%) and aluminium nanoparticles (ANP) (0–6%) was evaluated rheologically to determine the effect of wall slip occurring due to the formation of an apparent slip layer. True rheological properties have been obtained from gap-dependent steady-shear data using Tikhonov regularization method for the composite suspension. The advantage of this method is that it converts the gap-dependent steady-shear data into true rheological properties. The two-stage method can successfully establish both the true shear stress vs. shear rate behaviour and wall-slip parameters. The errors during rheological experimentation are analysed by determining the slip velocities and slip layer thickness. Slip velocity is observed to increase linearly with shear stress. Also, the slip layer thickness decreases with the increase in ANP content in the composite suspension. The maximum slip layer thickness of 2.13 µm is obtained for composition in which ANP is absent, and the same decreased to 0.24 µm for the composition containing 6% ANP. The rheological measurements show least deviation from gap-independent values as the amount of ANP in the propellant increases. Finally, a correlation of apparent slip layer thickness with normalized filler fraction is investigated to check the effect on wall-slip behaviour.     

Numerical modeling of composite propellant response to drop weight impact

Abstract

Finite element analysis is used to study the dynamic response of propellant subjected to drop weight impact. The model of the propellant incorporates varying amounts of ammonium perchlorate (AP) particles to account for stress concentrations due to sample inhomogeneity. The intent of this study is to examine locations which may lead to critical initiation shear stresses such as AP sliding on AP or AP sliding on steel. The initial full AP model used a 60% (by weight) solids loading corresponding to a research propellant formulated for a companion experimental program. Due to the unusually high number of slidelines which are needed to model the friction between the AP particles and surrounding media, the code was not capable of compiling the full model. Other models have been run to examine the effects of a few AP particles on the resulting stress state in the propellant. These models show significant increases in the maximum shear stress at locations immediately surrounding the AP particles. Quantitative comparisons are also made between homogeneous propellant and AP–in–propellant models. Two–dimensional geometric constraints of the code are also discussed. In particular, it is shown the default axisymmetric and the alternative plane strain geometries have limitations which do not allow for proper modeling of the particles. Finally, the limitations of using hydrocodes for simulating the effects of particles in propellant are discussed along with recommendation for further work.     

Simulation for the migration of nitrate ester plasticizers in different liners contacting with propellant by molecular dynamics

ABSTRACT

The liquid components, such as plasticizer, in the charge of solid propellant can potentially migrate into the liner contacting with propellant gradually, causing negative effects on the energetic performance, mechanical properties, and combustion properties of the propellant, as well as its interfacial adhesion properties with the liner. The study and prediction of the migration of the liquid components by experimental means remain challenging. In the present work, nitroglycerin (NG) and 1,2,4-butanetriol trinitrate (BTTN) were used as the model plasticizers to explore the factors affecting the migration of plasticizers into three different liners including polyoxyethylene (PEG)/polyisocyanate (N-100), hydroxyl-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) and polydimethylsiloxane (PDMS)/tetraethoxysilane (TEOS) by molecular dynamics simulation. The cohesive energy densities (solubility parameter), surface tensions, interfacial tensions, contact angles and diffusion coefficients of the plasticizers and liners were determined. It was found that the cohesive energy densities (solubility parameter) and surface tensions of the liner prepolymer and nitrate esters were in the order of PDMS<HTPB<PEG and BTTN<NG, respectively. The interfacial tensions and contact angles between the components followed the order of PEG-NG<HTPB-NG<PDMS-NG and PEG-BTTN<HTPB-BTTN<PDMS-BTTN, respectively. The interfacial tensions and contact angles values of NG are larger than BTTN. The diffusion coefficients of the nitrate ester plasticizers in various liners were in the order of PEG/N-100-NG>HTPB/IPDI-NG>PDMS/TEOS-NG and PEG/N-100-BTTN>HTPB/IPDI-BTTN>PDMS/TEOS-BTTN. Comparing different plasticizers, the order of diffusion coefficient in all liners is NG>BTTN, indicating NG is much easier to migrate into liners than BTTN. These simulation results are consistent with the experimental migration trends of NG into the corresponding liners, indicating that the molecular dynamics simulation can be used to study and predict the migration of plasticizers in various liners accurately and conveniently.     

Catalytic activity of nano-sized CuO on AP-CMDB propellant

ABSTRACT

In this work, nano-sized CuO prepared by mechanical grinding method was applied to the AP-CMDB propellant. The catalytic activity of nano-sized CuO on AP-CMDB propellant was investigated by thermogravimetric analysis/differential scanning calorimetric techniques. The combustion rates at atmospheric pressure of AP-CMDB propellant modified by nano-sized CuO were measured by strand burner method. The experimental results show enhancements on the thermal decomposition and combustion of AP-CMDB propellant in the presence of nano-sized CuO. Compared with blank propellant, the thermal decomposition temperature of AP-CMDB propellant shifts downward. Simultaneously, the combustion rate of AP-CMDB propellant at atmospheric pressure increases by about 22.2%. Encouragingly, the catalytic activity of nano-sized CuO on AP-CMDB propellant is superior to that of the bulk CuO, which leads to a potential application of nano-sized CuO in the AP-CMDB propellant.     

Combined evaluation of nitrocellulose-based propellants: toxicity,performance, and erosivity

ABSTRACT

New formulations of nitrocellulose-based propellants were evaluated aiming less-toxicity-and-less-erosivity. Three original ingredients of M-14 propellant – dinitrotoluene, dibutyl phthalate, and diphenylamine – were replaced. The new formulations, with ballistic performances similar to M-14, were based on ethylcentralite, akardite-II, RDX, diethylene glycol dinitrate, triethylene glycol dinitrate, and acetyl tributyl citrate (ATBC). The toxicities of the crude ingredients were analyzed. The H₂ content in the combustion products was a key point in the analysis. The best results were found to the compositions based on ATBC and akardite-II only. The work can be used to guide future works related to new formulations of propellants.     

Effect of Cumulative Damage on Rocket Motor Service Life

ABSTRACT

Two series of antihail rocket propellant grains failed only 3 months after production, due to the appearance of cracks in the grain channel. Structural integrity analysis demonstrated sufficient reliability at the beginning of service life. Further analysis showed that under temperature loads, cumulative damage during the short period in field stocks caused the grain failure, despite the established opinion that such failure can become significant only after lengthy storage. A linear cumulative damage law is evaluated by exposing a number of hydroxyl-terminated polybutadiene (HTPB) composite propellant specimens to different but constant stress levels. The analysis showed that cumulative damage must not be overlooked at the design stage. Further, a positive correlation between the propellant cumulative damage law and tensile strength is strongly indicated.     

CATALYTIC UPGRADING OF USED LUBRICATING OILS

ABSTRACT

Several commercial catalysts were tested for their activity for upgrading waste lubricating oils. The feedstock was vacuum distilled to remove the light and the heavy ends. Two trickle-bed reactors placed in series were employed, the top reactor contained a high surface area alumina and the bottom reactor the catalyst. A Ni-Mo-AI₂O₃ catalyst was selected for further study on the basis of its higner activity and activity maintenance. Several different hydrogen pressures, reactor temperatures, and liquid volume hourly space velocities were employed to arrive at the most optimum process conditions. This paper will discuss the effect of catalyst and process conditions on the product liquid color, viscosity, nitrogen, and sulfur content.     

Modeling of Closed-Vessel Experiments and Ballistic Parameter Estimation

ABSTRACT

Closed vessels have been used for the regression of lumped ballistic parameters for decades. If material and energy balances are coupled with burning rate empirical correlations, uncorrelated parameters can be adjusted, describing accurately the thermochemical behavior of the generated gases, even if the chemical composition of the propellant is unknown (aging of the propellant). This work presents a system of differential Equations integrated to produce pressure profiles within the vessel that are highly dependent on the choice of empirical parameters. Such parameters are manipulated via maximum likelihood statistical procedures, leading to the best set of parameters to describe the propellant.