摘要:

AbstractThe present paper deals with pressure oscillations in regenerative liquid propellant guns (RLPG) presenting the state‐of‐the‐art research into sources and control of these combustion instabilities. Pressure oscillations with amplitudes up to 50 % of mean pressure and frequencies up to 60 kHz or more are present in experimental data of RLPGs, especially at medium and large calibers. Amplitudes increase with the volumetric energy density of the liquid propellant and the mass flow rate during injection. Frequency analyses reveal that both acoustic modes and combustion noise are components of the recorded oscillations. Acoustic modes, in particular, have the potential to couple to resonant modes in near‐field mechanical structures. A multi‐phase, multi‐dimensional model investigation at ARL indicates that pressure waves reflected from internal boundaries are amplified as they pass the combustion zone of the highly pressure‐sensitive liquid propellant in a localized region near the injector. Experimental data lead to a similar understanding of the amplification of pressure oscillations in RLPGs. Experiments in the United States and in Germany confirm that the pressure oscillations can be mitigated by altering the combustion characteristics of the liquid propellant. Also, techniques that more effectively disperse the liquid propellant jet and thereby decrease the local accumulation of liquid propellant, may reduce pressure oscillations as shown in 30‐mm RLPG experiments. Further, energy‐absorb‐ing chamber walls or liners can serve as broad‐band filters and have been shown experimentally to be effective in reducing the amplitude of all frequencies. In addition, physical methods such as cavities and baffles reduce significantly specific acoustic frequencie

ISSN:0721-3115    

DOI:10.1002/prep.19950200502

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractApplication of Curie point pyrolysis gas chromatography (Py‐GC) and principal component analysis (PCA) in combination with a new normalization method could show the presence of patterns in PCA score plots not visible with the commonly used normalization method. In the first four principal components (PC's), two patterns were observed which could be attributed to aging and the crosslink density (CD). Aging of PBX samples has a complex effect on the peak loadings on PCI and are difficult to reveal. This in contrast to the peak loadings on PC3 and PC4 where both PC's are dominated by only one compound (respectively, C5H6and cyclohexene). This means that the formation of both these compounds proceeds independently from each other, i.e., by different mechanisms. It was shown that aging is slowed down in samples containing more of the antioxidant Flexzone. From the correlation matrix a few compounds were found to have very high correlations (>0.98). This was the case for methane, propane and n‐butane in both unaged and aged samples indicating that these compounds do not originate form moieties that are affected by aging. Also, cis‐ and trans‐butene have such high correlations and were formed in a 0.86:1 ratio, probably through the same mechanism. The absolute intensities decrease upon aging suggesting that both compounds originate form those parts of the polymer that are sensitive to aging. PC2 was related to saturated and unsaturated hydrocarbon compounds. The unsaturated compounds result from the elimination of water (free OH groups) from samples with CD values

ISSN:0721-3115    

DOI:10.1002/prep.19950200503

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractTNP, a heterocyclic nitramine containing a CNO2functionality, has been studied as regards the kinetics and mechanism of thermal decomposition, morphology and the gaseous products evolved therof, using thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR), differential scanning calorimetry (DSC), X‐ray diffraction (XRD) and hot stage microscopy. The elementary cell parameters obtained form the XRD pattern are: a = 18.818 ± 0.005 Å, b = 18.818 ± 0.005 Å and c = 4.867 ± 0.005 Å. The crystal belongs to the hexagonal system with c/a ratio = 0.259. IR spectra of TNP have also been recorded and the bands assigned. Kinetics of thermolysis has been followed both by isothermal TG and IR. The best linearity with a correlation coefficient of 0.986 was obtained for the three‐dimensional diffusion controlled Jander‐equation. Kinetic parameters were evaluated from the induction period as well as from isothermal TG. Activation energy was found to be 202.05 kJ/mol and log A(in s‐1) 22.78 from TG and 181.133 kJ/mol and log A (in s1) 20.97 from IR, respectively. The corresponding values were 171.17 kJ/mol and log A (in s‐1) 21.20 from the induction period data. The effect of a series of additives incorporated to the extent of 5 %, on the initial thermolysis of TNP, has also been studied. Evolved gas analysis by IR showed that CO2, NO2, NO and N2O are produced in larger amounts than CO and HCN. The cleavage of the NN bond appears to be the primary step in the

ISSN:0721-3115    

DOI:10.1002/prep.19950200504

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractInitiation intensity of a booster charge was varied by inserting plexiglass layers of different thicknesses. The time differences between shockwave arrival in the acceptor charge and the axial and radial detonation breakthroughs were determined, as well as the distance of the first radial breakthrough from the initiation plane ‐ referred to as the 90° distance Δs or Corner Turning Distance (CTD). Changes in the initiation time and Δs are small as long as the initiation intensity is sufficiently above to the threshold value. This result applies for cast explosive charges, TNT/RDX (35/65), Composition B type charges, and high performance pressed charges, HMX/Binder (9

ISSN:0721-3115    

DOI:10.1002/prep.19950200505

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractSimple one‐dimensional quasi‐static heat transfer calculations can be used to estimate fast cookoff times of cylindrical munitions with metal cases. The most critical parameter for the thermal analysis is the heat flux to the ordnance from the fire. One must remain aware that heating will be different for transparent flames of propane or methane test fires than they are for the opaque smoky flames of wood and jet‐fuel fires. Good values for material thermal conductivities and energetic material ignition behavior are also needed. Low‐conductivity composite cases cannot be analyzed in the same way because case mechanical failure is the primary initial failure path, rather than thermal conduction leading directly to ignition of the energetic material. Reaction violence cannot be calculated in a simple way with the present state of the art.Simple hand analysis of slow cookoff problems is limited to simple symmetric shapes of the type that were published over 30 years ago involving constant boundary temperatures. Modern computers, using finite‐difference codes can be used to readily solve problems with varying boundary temperatures to predict time to cookoff. However, as this paper shows, quasi‐static solutions of symmetric shapes (slabs, cylinders and spheres) can be obtained with desktop computer spreadsheets that give the same results as the finite‐difference codes. There are no a priori methods for predicting the violence of the slow cookoff reaction. These same comments apply as well to intermediate cookoff heating rates (greater than 3.3 K/h).Calculations by the methods of this paper place tools for designing experiments to explore cookoff behavior and for designing ordnance to meet insensitive munitions requirements on virtually

ISSN:0721-3115    

DOI:10.1002/prep.19950200506

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractWhen disposing of trinitrotoluene (TNT), the TNT‐melt must be pre‐treated. One possibility is to emulsify the melt in water after the TNT has been dismantled from the explosive charge. Production of these emulsions can be accomplished using emulsifying machines based on the rotor‐stator principle, e.g., ring gear dispersing machines or colloid mills. Droplet size reduction results from the normal and tangential stresses applied to the droplet as it is subjected to laminar or turbulent flow fields.Knowledge of the droplet size and droplet size distribution of the dispersed phase is important to determine the quality of an emulsion and the emulsification process. In this paper, results from the discontinuous production of TNT‐water emulsions are presented. In addition, the use of laser diffraction spectrometry for analyzing TNT droplet size is de

ISSN:0721-3115    

DOI:10.1002/prep.19950200507

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractSimultaneous thermogravimetry‐differential thermal analysis‐mass spectrometry have been used to characterize the zirconium/potassium perchlorate/nitrocellulose pyrotechnic system, by examining the components and their binary and ternary combinations under inert atmosphere conditions. Zirconium and potassium perchlorate were found to give an exothermic solid state reaction between 300°C and 500°C and the reaction was influenced significantly by the presence of small amounts of nitrocellulose. The decomposition of unreacted potassium perchlorate was observed to commence in the latter stages of the reaction and was found to be catalyzed by presence of the reaction products ZrO2an

ISSN:0721-3115    

DOI:10.1002/prep.19950200508

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe decomposition products of emulsion explosives and of other composite explosives containing ammonium nitrate, such as ANFO, were investigated. The compounds were thermolyzed at high temperature and pressure on the microsecond and millisecond time scales by adiabatic gas compression. It was found that the first step in emulsion decomposition is pyrolysis of the oil to form reactive intermediates like Hċand CH3ċ. These reactive species are oxidized by the decomposition products of ammonium nitrate in a later sequence of reaction step

ISSN:0721-3115    

DOI:10.1002/prep.19950200509

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe model is based on the more recent work of Hirsch and the original analytical work of Pugh, Eichelberger and Rostoker. Namely, the simplified Gurney formula for imploding cylinders derived by Hirsch is combined with the PER theory forming one‐dimensional computer code, and then it is used for predicting the 80‐mm diameter shaped charge jet parameters. Good agreement has been found with the experimental resu

ISSN:0721-3115    

DOI:10.1002/prep.19950200510

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

ISSN:0721-3115    

DOI:10.1002/prep.19950200511

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY