共查询到19条相似文献,搜索用时 125 毫秒
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单滴乳化燃料的微爆模型 总被引:2,自引:0,他引:2
本文分析了乳化燃料应用与机理研究的现状.在理论分析与实验研究的基础上,本文提出了一个新的分析单个乳化油滴微爆的理论模型-局部混合分阶段蒸发模型,反映了实际油滴内混合的过程,较好地解释了“冷滴”、“无水边界层”等实验现象,为进一步进行微爆的预报与分析影响微爆的因素打下了基础. 相似文献
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利用挂滴装置和高速摄影系统研究了单元推进剂LP1846液滴在0.2~4.0 MPa、673~973 K工况下的微爆特性。观察到液滴在不同环境压力和温度下的3种微爆模式,即液滴在着火前的轻度破碎、液滴在燃烧时的部分破碎和全部爆碎,并给出了微爆过程的特征照片,定量测试了液滴微爆延迟期、微爆温度和微爆直径与环境压力、温度的关系。初步分析了液滴微爆机理,认为第一种微爆机理主要是水组分的过热,第二、三种微爆机理是液相化学反应。研究结果对控制LP1846燃烧稳定性和指导液体发射药火炮内弹道设计均有参考价值。 相似文献
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基于对实验和理论的分析,提出一种异质结量子点隧穿(HQD)模型,并导出了纳米硅薄膜电导率完整的表达式.其主要思想是,纳米硅薄膜中的微晶粒(几个纳米大小)具有量子点特征,在微晶粒与界面之间由于两者能隙的差异构成晶间势垒,这类似于多晶硅中经常使用的晶间势垒模型(GBT).考虑到量子点中的单电子隧穿特征,认为纳米硅薄膜中的电传导是由微晶粒中电子弹道式输运与单电子越过势垒的隧穿构成的.这就是HQD模型的主要内容,理论结果与实验相符
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本文采用挂滴法研究了掺水质量分数30%(W30)的乳化柴油单液滴在573 K、673 K、773 K和873 K下的蒸发特性。结果表明,随着环境温度升高,归一化平方直径先增加后减小,首次微爆时刻逐渐小于进入准稳态时刻,而微爆频率先减小后增加,其微爆强度也先减小后增加,773 K是转捩点温度。本文还发现随着环境温度的升高,液滴气泡成核从单位点成核逐渐演变为多位点成核,并导致了大气泡形成过程从与强微爆过程重合过渡到与弱微爆过程重合,最终与强微爆和弱微爆过程分离。 相似文献
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Microexplosion of an emulsion droplet during Leidenfrost burning 总被引:2,自引:0,他引:2
Toshikazu Kadota Hajime Tanaka Daisuke Segawa Shinji Nakaya Hiroshi Yamasaki 《Proceedings of the Combustion Institute》2007,31(2):2125-2131
An experimental study has been made of the microexplosion of an emulsion droplet on a hot surface during Leidenfrost burning. Photographic observation is used to study how the emulsion droplet behaves and what happens inside the droplet and to measure the waiting time for the onset of microexplosion. Weibull analysis was used to obtain the distribution function of the waiting time for the onset of microexplosion and to derive the formula for the rate of microexplosion as a function of water volume and emulsion temperature. The base fuels employed were n-decane, n-dodecane, n-tetradecane, and n-hexadecane. The results show that the increase in emulsion temperature with lapse of time results in the agglomeration and coalescence of microdroplets of base fuel dispersed in the continuous phase of water inside the emulsion droplet, terminated by the complete separation of the two phases. At the end of the phase separation process, an opaque water droplet is formed in the central core and is enveloped by the transparent shell of base fuel. Preferential evaporation of the base fuel occurs after the phase separation. The volume of the base fuel decreases while the water volume remains constant. The onset of the microexplosion of an emulsion droplet burning on the hot surface is classified by the wearout type of the Weibull distribution. The waiting time for the onset of the microexplosion decreases with increases in the normal boiling point of base fuel, initial water content, ambient pressure, and test surface temperature. The rate of microexplosion increases with the lapse of time and with increased normal boiling point of the base fuel. The rate of microexplosion increases linearly with increasing water volume in the emulsion droplet and decreases exponentially with the inverse of emulsion temperature. 相似文献
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J. G. Linhart 《Czechoslovak Journal of Physics》1992,42(10):985-1004
A mechanism in which a quasi-spherical fast liner implodes on a Z-superpinch as a target is discussed. It is argued that if the target is a Pu-D-T cylinder the implosion can result in a fusion-fission microexplosion whose yield is of the order of 1 GJ. This ought to be sufficient to propagate nuclear reaction axially out into hard-to-ignite fuels such as DD, LiD. A reactor in which 10 GJ is liberated every 10 s is briefly mentioned.I am grateful to Dr. M. Srinivasan for criticism and bringing to my notice the work of authors unknown to myself and to Dr. B. Robouch for his generous help with numerical caiculations. I also wish to express my thanks to Prof. M. Haines and Prof. V. Nardi for several important suggestions. 相似文献
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A laser adhesiometer is developed to determine the adhesive and cohesive forces in multilayer materials. The obtained experimental dependences are explained using the laser microexplosion model. The advantages of determining the adhesive and cohesive forces using the laser adhesiometer over other methods are grounded. 相似文献
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Microexplosions in tellurite glasses 总被引:2,自引:0,他引:2
S.K. Sundaram C.B. Schaffer E. Mazur 《Applied Physics A: Materials Science & Processing》2003,76(3):379-384
Femtosecond laser pulses were used to produce localized damage in the bulk and near the surface of baseline, Al2O3-doped and La2O3-doped sodium tellurite glasses. Single or multiple laser pulses were non-linearly absorbed in the focal volume by the glass,
leading to permanent changes in the material in the focal volume. These changes were caused by an explosive expansion of the
ionized material in the focal volume into the surrounding material, i.e. a microexplosion. The writing of simple structures
(periodic array of voxels, as well as lines) was demonstrated. The regions of microexplosion and writing were subsequently
characterized using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and atomic force microscopy (AFM).
Fingerprints of microexplosions (concentric lines within the region and a concentric ring outside the region), due to the
shock wave generated during microexplosions, were evident. In the case of the baseline glass, no chemistry change was observed
within the region of the microexplosion. However, Al2O3-doped and La2O3-doped glasses showed depletion of the dopant from the edge to the center of the region of the microexplosions, indicating
a chemistry gradient within the regions. Interrogation of the bulk- and laser-treated regions using micro-Raman spectroscopy
revealed no structural change due to the microexplosions and writing within these glasses.
Received: 27 December 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. +1-509/376-3108, E-mail: sk.sundaram@pnl.gov 相似文献
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Superposition of orbital angular momentum of photons by a combined computer-generated hologram fabricated in silica glass with femtosecond laser pulses
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This paper introduces a novel method to realize the superposition of orbital angular momentum of photons by combined computer-generated hologram (CCGH) fabricated in silica glass with femtosecond laser pulses. Firstly, the two computer-generated holograms (CGH) of optical vortex were obtained and combined as a CCGH according to the design. Then the CCGH was directly written inside glass by femtosecond laser pulses induced microexplosion without any preor post-treatment of the material. The vortex beams with different vortex topological charges (including new topological charges) have been restructured using a collimated He-Ne laser beam incidence to the CCGH normally. A theoretical and experimental explanation has been presented for the generations of the new topological charges. 相似文献
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《Composite Interfaces》2013,20(3):213-221
The formation of higher order aggregates in aqueous media from naturally occurring surfactants (biosurfactants) and its mechanism have been studied. A liposome (vesicle), as a kind of artificial cell, is prepared according to a newly developed microencapsulation technique from phospholipids by mimicking the molecular structure of biomembranes. Secondly, the surface active properties of alkaline salts of spiculisporic acid depend on the kinds of alkali as its gegen ions; these have been studied for the purpose of a detailed understanding of vesicle formation of the alkylamine salts of spiculisporic acid in the binary system consisting of spiculisporates and water. Thirdly, the solution behavior of the ternary system of spiculisporates-oil-water is examined. Divalent cationic salts of spiculisporic acid formed oil-in-water (O/W) emulsion gels due to ionic-bonding network formation of spiculisporates around emulsified oil droplets and these are important for their gelling properties. These gelling systems may have potential to be O/W emulsion-type paints and safe fuels. 相似文献
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We introduce a novel method to generate the optical vortex with computer-generated hologram (CGH) fabricated inside glass by femtosecond laser pulses. The CGH was directly written inside glass by femtosecond laser pulses induced microexplosion without any pre- or post-treatment of the material. We also realized the restructured optical vortex beams of both the transmission and reflection pattern with high fidelity using a collimated He-Ne laser beam. The total diffractive efficiency of both the transmission and reflection pattern is about 4.79%. 相似文献
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Direct optical fabrication of 3D photonic crystals in a high refractive index LiNbO3 crystal by using the femtosecond laser-induced microexplosion method is investigated. The focal distortion, caused by the refractive index mismatch-induced spherical aberration, can be significantly reduced by using a so-called threshold fabrication method. As a result, 3D fcc photonic crystals are fabricated by stacking quasi-spherical voids layer by layer. Photonic stopgaps with suppression rates of up to 30% in the transmission spectra are observed. The angle dependence of the stopgaps is also revealed. 相似文献
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《Ultrasonics sonochemistry》2014,21(2):722-728
An ultrasonic technique was applied to preparation of two-phase water-in-oil (W/O) emulsified fuel of water/diesel oil/surfactant. In this study, an ultrasonic apparatus with a 28 kHz rod horn was used. The influence of the horn tip position during ultrasonic treatment, sonication time and water content (5 or 10 vol%) on the emulsion stability, viscosity, water droplet size and water surface area of emulsion fuels prepared by ultrasonication was investigated. The emulsion stability of ultrasonically-prepared fuel significantly depended on the horn tip position during ultrasonic irradiation. It was found that the change in the stability with the horn tip position was partly related to that in the ultrasonic power estimated by calorimetry. Emulsion stability, viscosity and sum of water droplets surface area increased and water droplet size decreased with an increase in sonication time, and they approached each limiting value in the longer time. The maximum values of the viscosity and water surface area increased with water content, while the limiting values of the emulsion stability and water droplet size were almost independent of water content. During ultrasonication of water/diesel oil mixture, the hydrogen and methane were identified and the cracking of hydrocarbon components in the diesel oil occurred. The combustion characteristics of ultrasonically-prepared emulsion fuel were studied and compared with those of diesel oil. The soot and NOx emissions during combustion of the emulsified fuel with higher water contents were significantly reduced compared with those during combustion of diesel oil. 相似文献