共查询到20条相似文献，搜索用时 15 毫秒
1.
Radiative ignition of quasi‐homogeneous mixtures of ammonium perchlorate (AP) and hydroxyterminated polybutadiene (HTPB) binder has been investigated experimentally. Solid propellants consisting of fine AP (2 μm) and HTPB binder (~ 76/24% by mass) were ignited by CO2 laser radiation. The lower boundary of a go/no‐go ignition map (minimum ignition time vs. heat flux) was obtained. Opacity was varied by adding carbon black up to 1% by mass. Ignition times ranged from 0.78 s to 0.076 s for incident fluxes ranging from 60 W/cm2 to 400 W/cm2. It was found that AP and HTPB are sufficiently strongly absorbing of 10.6 μm CO2 laser radiation (absorption coefficient ≈250 cm−1) so that the addition of carbon black in amounts typical of catalysts or opacitymodifying agents (up to 1%) would have only a small influence on radiative ignition times at 10.6 μm. A simple theoretical analysis indicated that the ignition time‐flux data are consistent with in‐depth absorption effects. Furthermore, this analysis showed that the assumption of surface absorption is not appropriate, even for this relatively opaque system. For broadband visible/near‐infrared radiation, such as from burning metal/oxide particle systems, the effects of in‐depth absorption would probably be even stronger. 相似文献
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Jiang Zhi Li Shu‐Fen Zhao Feng‐Qi Liu Zi‐Ru Yin Cui‐Mei Luo Yang Li Shang‐Wen 《Propellants, Explosives, Pyrotechnics》2006,31(2):139-147
A comparison of various experimental results for combustionrelated properties evaluation, including burning rates, deflagration heat, flame structures and thermal decomposition properties, of AP/RDX/Al/HTPB composite propellants containing nano metal powders is presented. The thermal behavior of n‐Al (nano grain size aluminum) and g‐Al (general grain size aluminum i.e., 10 μm) heated in air was also investigated by thermogravimetry. The burning rates results indicate that the usage of bimodal aluminum distribution with the ratio around 4 : 1 of n‐Al to g‐Al or the addition of 2% nano nickel powders (n‐Ni) will improve the burning behavior of the propellant, while the usage of grading aluminum powders with the ratio 1 : 1 of n‐Al to g‐Al will impair the combustion of the propellant. Results show that n‐Al and n‐Ni both have a lower heating capacity, lower ignition threshold and shorter combustion time than g‐Al. In addition n‐Al is inclined to burn in single particle form. And the thermal analysis results show that n‐Ni can catalyze the thermal decomposition of AP in the propellant. The results also confirm the high reactivity of n‐Al, which will lead to a lower reaction temperature and rather higher degree of reaction ratio as compared with g‐Al in air. All these factors will influence the combustion of propellants. 相似文献
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Carmen Lpez‐Munoz Francisco‐Javier Snchez Velasco Jos‐Ramn García‐Cascales Ramn Mur Ramn‐Antonio Otn‐Martínez 《Propellants, Explosives, Pyrotechnics》2019,44(11):1482-1493
In this work, a model for the characterization of unsteady combustion of AP/HTPB composite propellants is benchmarked against experimental data. The model describes a change of phase of the propellant from condensed to gas phase and afterwards its combustion by a simplified chemistry scheme. A Finite Volume approximation is used to solve the system of equations. Firstly, the conservation equations including all source terms but combustion source terms are solved, in this case the numerical fluxes are computed by using Rusanov numerical scheme. Diffusive source terms are solved explicitly. After this, a first order Euler scheme is used to solve the system of ordinary differential equations resulting after considering the combustion source terms. The code is validated with two tests: the burning of a strand composed by AP and HTPB in sandwich configuration and the burning of a strand composed by AP particles uniformly distributed within HTPB. In both cases, simulation results are compared with experimental data. Influence of the pressure in burning rate, AP mass fraction, temperature and gas velocity are examined for sandwich test. For the strand, the effect of the pressure and initial temperature is also analyzed. Results show a good agreement between experimental and numerical data. 相似文献
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James C. Thomas Andrew R. Demko Thomas E. Sammet David L. Reid Sudipta Seal Eric L. Petersen 《Propellants, Explosives, Pyrotechnics》2016,41(5):822-834
Modern chemical synthesis techniques have allowed for improved incorporation of nano‐scale additives into solid propellants. Various methods were implemented to incorporate titania nanoparticles into three representative ammonium perchlorate composite propellants (APCP), and the mechanical properties of each formulation were tested and compared to those of an analogous baseline. Advanced imaging techniques were applied to all particle synthesis methods to characterize particle size and particle network type and size. Uniaxial tensile testing was performed to measure propellant ultimate strength, ductility, and elastic modulus. In general, the addition of nano‐titania additives to the propellant decreased propellant strength and modulus, but improved ductility. Propellant formulations containing in‐situ titania exhibited an increase in ductility of 11 %, 286 %, and 186 % with a corresponding reduction in strength of 82 %, 52 %, and 17 % over analogous baselines. These trends corresponded to a simultaneous decrease in propellant density, indicating that when implementing nano‐sized additives, care must be taken to monitor the effect of the altered manufacturing techniques on propellant physical properties in addition to just monitoring burning rates. Tailoring of propellant manufacturing procedures and the addition of Tepanol bonding agent to an in‐situ APCP formulation fully recovered the propellant density and ultimate strength while retaining the enhanced ductility. 相似文献
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Selvakumar Subramanian Sthanikam Siva Prasad 《Propellants, Explosives, Pyrotechnics》2023,48(3):e202200316
Polyurethane based composite solid propellant (CSP) having aluminium as fuel and ammonium perchlorate (AP) as oxidizer is used in present day solid rocket motors (SRMs). Mechanical and burn rate properties of CSP are wholly dependent on the composition and packing fraction of bimodal AP. Any process deviation or anomalous behavior of propellant slurry at the end of pre/final mixing will result in unacceptable mechanical and ballistic properties leading to rejection of these mixes. Hence, it becomes essential to investigate for possible causes of anomalous behavior such as incorrect content and Coarse/Fine AP ratio (CAP/FAP), contamination with foreign materials, etc. Though suitable test procedures are already available for homogeneity/composition analysis and in vogue, there is no regular test procedures in case of interchange of raw materials of different formulations, to check for contamination of pre-mixes and to verify AP content in the mixes after mixing the curing agent. Herein, simple contingency procedures have been developed to estimate CAP/FAP in the pre-mix and AP content in pre/finalmix slurries. The CAP (before its use in premix and after CAP/FAP estimation) was examined using a particle size and shape analyzer and an optical microscope. Contamination checks were also carried out on the samples of premixes usingFT-IR and DSC. In addition, propellant samples cured under standard conditions were checked for possible deviations with respect to expected mechanical, interfacial, physical and ballistic properties. Conclusions drawn from the investigation can be used to clear the pre/final mix batches for further processing.It is to be noted that these cost-saving contingency procedures will hereafter form part of analytical testing routines during the processing of solid propellant segments. 相似文献
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Harmeet Singh Darshana Singh Dhanraj Chimurkar Jayesh Upadhyay Amit Kumar Arvind Kumar Shrikant Pande Priyesh More 《Propellants, Explosives, Pyrotechnics》2020,45(4):647-656
For enhanced range, higher payload capacities and for miniaturized propulsion systems, today's strategic and tactical weapon system designers demand for higher density and specific impulse of the propellant. In order to enhance the density impulse of HTPB/DOA/RDX/AP/Al based composite propellant, studies have been carried to replace conventional HTPB/DOA binder system with hydroxyl terminated block copolymer of polybutadiene and ϵ-caprolactone with NG as plasticizer. Total eight numbers of compositions were formulated with varying content of RDX. Both binder systems were compared in propellant compositions by evaluating various physical, thermal and ballistic properties. Various rocket performance parameters of each formulation were theoretically predicted by NASA CEC-71 program and burning rate was measured in pressure ranges of 3-7 and 7-11 MPa by the acoustic emission technique. In addition, density, viscosity build up, calorimetric values, thermal decomposition and sensitivity parameters of each composition were also assessed and compared. In an outcome, it was concluded that HTBCP25/NG based propellant compositions enhance the density by 4.4–5 % and calorimetric values by 12–15 % as compared to HTPB/DOA based compositions. Strand burning rate data show enhancement of burning rate by 40–70 % at 7 MPa pressure in HTBCP25/NG based compositions. Impact and friction sensitivity data also revealed their utility in propellant compositions for future applications. 相似文献
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聚丙烯基纳米SiO2复合材料的流变性能研究 总被引：6，自引：0，他引：6
采用普通毛细管流变仪和高压毛细管流变仪,通过测定流变性能,研究不同表面处理工艺对PP基纳米SiO2复合材料的团聚,分散和界面性能的影响。结果表明,纳米SiO2采用偶联剂处理并包覆长链分子型分散剂后,可增加界面层厚度,形成相间缓冲层,由此增大纳米颗粒与颗粒间的距离,使纳米颗粒团聚体变得松散,摩擦阻力有所下降,熔体流动性损失减少,PP基纳米SiO2复合材料的熔融流动性基本随纳米SiO2用量的增加而下降;当纳米SiO2质量分数约为3%时,该复合材料的熔体流变性能近似于纯PP,并在挤出或注射成型的剪切速率范围内加工流动性未明显下降。 相似文献
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Nadir Yilmaz Burl Donaldson Walter Gill William Erikson 《Propellants, Explosives, Pyrotechnics》2008,33(2):109-117
Strand burner pressure–time data are analyzed to determine if the propellant burning rate can be extracted. This approach is based on strand burner pressure–time history that is related to the temperature change due to exothermic reaction heating of chamber gases and gas addition to the chamber by propellant combustion products. In support of this method, chemical equilibrium calculations were made to project product composition, internal energy, and other needed properties. A mathematical model was formulated and solved numerically and the calculated burning rates were compared with the experimental wire‐break time results provided simultaneously and with the propellant manufacturer's results, when available. The comparisons reveal that the approach has merit and that more accurate pressure determination coupled with additional thermochemical information and strand burner gas temperature measurements has the potential to make this approach a viable technique and one that can be applied in conjunction with other burning rate measurements. The proposed method is similar to a well‐developed technique which is commonly applied to ballistic powders but with adjustments for the differences in geometry, pressure, and time of event. 相似文献
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In this study, the hardening reaction speed of a rocket motor liner based on the Aging of a curing system comprised of a hardener and hardening catalyst was investigated. With the increasing Aging time of the curing system, the liner viscosity build-up was accelerated. The raw material having the biggest impact on the hardening reaction of the curing system's liner was triphenylbismuth (TPB). Stirring isophorone diisocyanate and TPB form an activated complex, and the activated complex facilitates the urethane reaction. If TPB is ligand bound with isocyanate, it forms a TPB-isocyanate complex. This is a type of TPB's oxide, and the formation of the activated complex is visible through changes in its color. In addition, lining hardening time can be adjusted by the Aging period of the curing system through used in this study, and the adhesive strength with the liner and propellant can be improved. 相似文献
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A new type of photodegradable poly(vinyl chloride)‐bismuth oxyiodide/TiO2 (PVC‐BiOI/TiO2) nanocomposite film was prepared by embedding a nano‐TiO2 photocatalyst modified by BiOI into the commercial PVC plastic. The solid‐phase photocatalytic degradation behavior of the as‐prepared film was investigated in ambient air at room temperature under UV light irradiation, with the aid of UV‐Vis spectroscopy, weight loss monitoring, scanning electron microscopy, and FT‐IR spectroscopy. Compared to the PVC‐TiO2 nanocomposite film, the PVC‐BiOI nanocomposite film and the pure PVC film, the PVC‐BiOI/TiO2 nanocomposite film exhibited a higher photocatalytic degradation activity. The optimal mass ratio of BiOI to TiO2 was found to be 0.75 %. The weight loss rate of the PVC‐BiOI/TiO2 nanocomposite film reached 30.8 % after 336 h of irradiation, which is 1.5 times higher than that of the PVC‐TiO2 nanocomposite film under identical conditions. The solid‐phase photocatalytic degradation mechanism of the nanocomposite films was briefly discussed. 相似文献
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《Propellants, Explosives, Pyrotechnics》2017,42(2):158-166
This study presents a comparison of commercially available titania nano‐particles produced using electric wire explosion with nano‐particles manufactured by the authors using a sol‐gel synthesis process. For the present study, 20‐nm titania was purchased off‐the‐shelf. It was determined to be rough spheres of 20 nm forming large, micron‐sized agglomerates, whereas particles synthesized using the sol‐gel process were found to be fundamentally 10 nm but with sub‐micron agglomerations thereof. The nano‐titania was added to 80% AP monomodal propellants at 0.3% and 1.0% by mass. Additional, 85% bimodal‐AP mixtures were made, comparing commercial titania to the laboratory‐synthesized particles at 1.0% by mass. Another set of samples compared a method of pre‐mixing the synthesized additives directly into the binder material at 0.3% by mass of laboratory titania; two additional pre‐mixed titania batches at 0.5% by mass were doped with either Fe or Cu into the nanocrystals. All propellants were tested up to 13.8 MPa at 3.8 MPa increments. Dry powder laboratory additives show a 60‐to‐100% increase in burning rate over the baseline samples with no catalyst and a 20‐to‐30% increase over the commercial nano‐particles. Pre‐mixed additives were found to produce similar burning rate increases but with lower concentrations required. This latest generation of particle synthesis techniques was further demonstrated in this study to have great potential for future propellant catalyst development. 相似文献
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S. Bernal M. A. Cauqui G. A. Cifredo J. M. Gatica C. Larese J. A. Prez Omil 《Catalysis Today》1996,29(1-4):77-81
The combined application of chemical techniques and HREM shows that platinum deactivation in Pt/CeO2 catalysts steadily increases with the reduction temperature (Tr: 473–1173 K). Though no suppression of the H2 adsorption was observed, the TPD-H2 traces indicate the occurrence of significant chemical changes with Tr. As revealed by HREM, the metal decoration starts at Tr: 973 K, a temperature well above those at which the chemical effects can be observed. 相似文献
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采用钛本丁酯和硝酸亚铈为前驱物制备出性能较好、可用于电致变色装置的离子贮存电极材料,分析了薄膜材料制备条件对其电化学性能的影响。结果表明该材料克隆了纯氧化铈材料对电化学响应速率低的不足,具有可逆的电化学离子注入及在可见光范围内保持透明的特性。 相似文献
19.
《Propellants, Explosives, Pyrotechnics》2017,42(9):1085-1094
In order to study the out‐of‐phase blowing effect of ammonium perchlorate/hydroxyl terminated polybutadiene (AP/HTPB) under transient depressurization, a two‐dimensional periodic sandwich model of AP/HTPB sandwich unsteady combustion was established. The gas‐solid two‐step total reaction was used to couple the gas‐solid boundary layer, and the AP/HTPB step‐down temperature criterion was applied. The numerical simulation comparative analysis under the initial combustion pressure 3.5 MPa∼10 MPa and the initial depressurization rate of 1000 MPa/s∼2000 MPa/s was experimented. The results show that under the condition of initial combustion pressure of 3.5 MPa and pressure reduction rate of 1000 MPa/s, the formation of narrow diffusion chemical reaction zone appears in the initial stage of depressurization; when the combustion pressure drops to about 1.7 MPa, the flame appears dual characteristics: diffusion and premixed combustion; when the pressure dropped to 0.1 MPa, the flame is premixed combustion. AP(g) is the main factor causing the out‐of‐phase blowing effect. During the initial stage of combustion, AP(g) decomposes rapidly and its decomposition product is close to the combustion surface; with the rapid decrease of pressure, the gas‐phase heat feedback decreases, leading to the decrease of AP(g) decomposition rate and AP(g) diffusion to the gas phase, which is the initial phase of out‐of‐phase blowing effect; when the gas phase heat feedback reduced and the temperature is below 750 K, the decomposition of AP(g) is stopped and the undecomposed AP(g) is further diffused to the gas phase region, which exacerbates the out‐of‐phase blowing effect, leading to the extinguishment of AP/HTPB. The unsteady combustion flame extinction time increases with the initial combustion pressure, and decreases with the initial depressurization rate. 相似文献
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《Propellants, Explosives, Pyrotechnics》2018,43(4):404-412
To investigate the effects of charge size on the slow cook‐off characteristics of trilobite ammonium perchlorate (AP)/hydroxyl‐terminated polybutadiene (HTPB) composite propellant with slits, a cook‐off model of three‐dimensional base bleed unit is developed based on the two‐step decomposition reaction mechanism of AP/HTPB propellant at the external heating rates from 3.3 to 9 K/h. The charge length of AP/HTPB propellant is 72 mm with 43 mm to 53 mm in grain diameter, and the grain diameter is 43 mm with 72 mm to 90 mm in charge length, respectively. The results show that heating rate and charge size determine the ignition position of AP/HTPB propellant. The effects of charge size on the ignition position and cook‐off temperature are small at the heating rate of 3.3 K/h. As the heating rate increases to 4.6 K/h–6 K/h, with the grain diameter and charge length extending, the ignition position gradually moves from the inner wall to the surface near the slit, meanwhile the cook‐off temperature changes obviously. When the heating rate increases to 9 K/h, the ignition position of AP/HTPB propellant at different charge sizes all occurs on the outer interface between the propellant and slit, there is no obvious influence of different charge sizes on the ignition temperature of AP/HTPB propellant. Additionally, the law of ignition time of AP/HTPB propellant to charge size is the same at different heating rates. 相似文献