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Experimental data from vented explosion tests using stoichiometric methane–air and 18% hydrogen–air mixtures in a 63.7 m3 chamber with a 2.7 or 5.4 m2 vent are presented. Results from experiments conducted using stoichiometric propane–air in 2.42 m3 vessel with a 0.26 m2 vent are also reported. The tests were focused on the effect of fuel, enclosure size, ignition location, vent size, and obstacles on the pressure development of a propagating flame in a vented enclosure. The dependence of the maximum pressure generated on the experimental parameters was analyzed. It was found that the pressure maxima may be caused by pressure transients controlled by the interplay of the maximum-flame area, the burning velocity, and the overpressure generated by an external explosion. A simple model was proposed to estimate the maximum pressure for each of the main pressure transients. The model was found to agree with the experimental data within the experimental uncertainty. 相似文献
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The Saffman-Taylor viscous fingering instability occurs when a less viscous fluid displaces a more viscous one between narrowly spaced parallel plates in a Hele-Shaw cell. Experiments in radial flow geometry form fan-like patterns, in which fingers of different lengths compete, spread and split. Our weakly nonlinear analysis of the instability predicts these phenomena, which are beyond the scope of linear stability theory. Finger competition arises through enhanced growth of sub-harmonic perturbations, while spreading and splitting occur through the growth of harmonic modes. Nonlinear mode-coupling enhances the growth of these specific perturbations with appropriate relative phases, as we demonstrate through a symmetry analysis of the mode coupling equations. We contrast mode coupling in radial flow with rectangular flow geometry. 相似文献
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叙述了四极质谱(QMS)的结构和气体分析质谱(GAM)的定量分析工作原理。四极质谱具有快速扫描响应,较高的响应灵敏度的特点,在经过标准气体校准后,加上独特的气体进样系统,可用于惯性约束聚变(ICF)靶丸内混合气体组分含量及总量的定量分析。同时,在经过坐标尺度放大等手段,可以对混合气体中质量数极为接近的氘(4.028 2)和氦(4.002 6)在高分辨模式下进行基线分离。用四极质谱对各种靶丸结构、不同混合气体种类的气体进行了定量组分分析,为ICF实验用靶提供了同批次实验数据。 相似文献
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An approximate solution of the problem of quenching and re-ignition of products/reactants pockets mixed by turbulence is presented. The approach is based on the analysis of thermal regimes of the pocket, but not on the concept of flame stretch. Critical conditions for quenching and re-ignition of the mixed pockets are obtained in a simplified analytical model, and applied to the problem of the sharp difference between the cases of weak and strong flame acceleration in gas explosions. The critical conditions of the mixed eddies in the turbulent flow are shown to depend on the size of the mixed eddies, mixture properties and turbulence intensity. The critical Karlovitz number, Ka, for thermal quenching is shown to increase with the ratio of densities between reactants and products, σ, and with the overall reaction order, n, and to decrease with the Zeldovich number β (dimensionless activation energy) and Lewis number, Le. For the smallest mixed pockets, which are about the size of the laminar flame thickness, the critical Ka-number defines the boundary of the domain of broken flamelets and distributed reaction zones. This number is shown to be of the same order of magnitude as that found from experiments and from direct numerical simulations. The critical conditions for thermal quenching of the largest pockets that can be mixed by turbulence are shown to be independent of the turbulent intensity and could be expressed as a function of σ on β, n, and Le. The mixture properties, thus, may prescribe certain types of flame behavior in turbulent flows. The corresponding critical conditions are linked to the sharp boundary between the cases of weak and strong flame acceleration, which was not satisfactorily explained in previous studies. These critical conditions are shown to have similar critical σ-values and general trends as the experimental data. 相似文献
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基于声表面波技术的气体传感器包括采用敏感膜和结合气相色谱两种方式。比较而言,采用敏感膜的声表面波气体传感器体积小、功耗低,适应小型化毒气报警器的发展要求,但可检测的气体种类少、灵敏度低、存在交叉干扰问题;声表面波与气相色谱联用的气体分析仪灵敏度高、可检测气体种类多、很好地解决交叉干扰问题,特别适合于复杂大气背景条件下的气体成分分析。本文从传感器响应机理分析与物理功能结构两方面出发介绍了两类声表面波气体传感器的研究进展情况。 相似文献
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Virgilijus Vai?aitis Valerijus Smilgevi?ius Vygandas Jarutis 《Optics Communications》2011,284(8):2206-2209
Terahertz emission from air excited by the tightly focused fundamental and second harmonic pulses of femtosecond Ti:Sapphire laser has been analyzed. It has been found that the curved phase fronts of the pump waves cancel each other resulting in the flat phase front of the nonlinear polarization at terahertz frequency. Also, in addition to the phase terms obtained using plane-wave approximation, we have found the yet unreported phase term, which in most cases can be as large as π/2. 相似文献
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针对分置式斯特林制冷机存在的磨损和污染主要失效模式,论述了磨损特性的激振法测阻尼比试验方法和工质污染的分析方法和结果。磨损和污染的试验分析方法可用于斯特林制冷机研制时的失效模式控制。 相似文献
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采用蒙特卡罗方法模拟了高空核爆炸瞬发辐射中子、γ射线、X射线电离大气的过程,给出了几种爆炸场景下瞬发辐射产生的附加电离电子密度空间分布.针对大气密度随高度非均匀连续变化的特性,采用质量距离抽样方法取代常用的步长抽样方法,无需根据大气密度随高度的变化进行分层处理,提高了计算效率.结果表明:对于不同的爆高,瞬发辐射电离分布存在显著的差异;随着爆高的增加,瞬发辐射附加电离区范围增大,但电子密度的峰值减小.
关键词:
高空核爆炸
瞬发辐射
大气电离
蒙特卡罗方法 相似文献
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Nuclear fusion from Coulomb explosions of deuterated methane clusters subjected to ultraintense femtosecond laser pulses 下载免费PDF全文
This paper reports that Coulomb explosions taken place in the
experiment of heteronuclear deuterated methane clusters
((CD4)2) in a gas jet subjected to intense femtosecond
laser pulses (170mJ, 70fs) have led to table-top laser driven DD
nuclear fusion. The clusters produced in supersonic expansion had an
average size of about 5nm in radius and the laser intensity used
was 3×1017W/cm2.The measured maximum and average
energies of deuterons produced in the laser--cluster interaction were
60 and 13.5keV, respectively. From DD collisions of energetic
deuterons, a yield of 2.5(±0.4)×104 fusion neutrons
of 2.45MeV per shot was realized, giving rise to a neutron
production efficiency of about 1.5×105 per joule of
incident laser pulse energy. Theoretical calculations were performed
and a fairly good agreement of the calculated neutron yield with
that obtained from the present experiment was found. 相似文献
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应用声表面波气相色谱快速定性分析姜黄挥发油。声表面波气相色谱采用DB-5毛细管色谱柱,初始温度45℃,6℃/s程序升温至160℃,检测结果与气相色谱质谱结果进行比较。姜黄挥发油定性分析中, 声表面波气相色谱20s完成检测,而气相色谱-质谱需要30min完成,声表面波气相色谱检测更高效;同时,声表面波气相色谱与气相色谱质谱共同检测出姜黄挥发油中10种化学成分,且10种化学成分相对百分含量总和占挥发油总成分的90%以上,由于色谱柱长度区别,声表面波气相色谱检出的化学成分相对较少;定量分析中,对声表面波气相色谱进样方式进行了考察,顶空进样与液体进样对化学成分相对百分含量检测有较大差异;采用与气相色谱质谱一致的液体进样方式,对姜黄挥发油中反式石竹烯定量分析,声表面波气相色谱最低检出限可以达到16.9 pg,在0.001624~0.01624 mg/mL范围内R=0.9976具有较好的线性关系,且精密度和重复性较好。声表面波气相色谱能够用于姜黄挥发油的快速定性和定量分析,为中药挥发油的分析提供了新的快捷的检测技术基础。 相似文献
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基于目标发射光谱分析法的原理,通过分析小尺寸实验平台上测得的体积分数10%的甲烷爆炸火焰光谱数据,提出甲烷爆炸火焰光谱特征分析方法,包括频域特征参数光谱密度、波段辐射光强度、波段平均及偏差,时域特征参数波段辐射能量、时间段平均及偏差和特性参数偏度、峰度、半宽的计算方法;分析得出当甲烷爆炸火焰光谱波长值为某些定值时,光谱密度在1 nm范围内在正向与负向之间转换,表明光强密集程度变化剧烈;甲烷爆炸火焰光谱波段定积分在550~900 nm波段最强;甲烷爆炸火焰光谱信号随着波长的增大可测时间增长,信号强度在达到峰值后整体呈衰减趋势,在衰减过程中间隔出现依次减弱的强度增强;研究结果表明目标发射光谱分析法可应用于甲烷爆炸感应期内火焰光谱的动态半定量分析,分析得出的光谱特征可作为检测甲烷爆炸火焰的判据。 相似文献
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A capillary wave was created on a surface by vibrating from the bottom of a container. When the amplitude of the container vibration approached the critical point, called the onset state, the surface broke up and bursted into very small drops on the air. The numerical analysis was used to determine the amplitude of the onset. The onset point was found to be 0.349 μm at f = 500 kHz. The critical amplitude hcr was determined by using a multi-Fourier horn nozzle (MFHN) device. The onset point was measured to be 0.37 μm using a laser Doppler vibrometer (LDV) with the MFHN at f = 486 kHz. These drops indicate that particle size distributions of 10.8 μm and 7.0 μm were produced by the MFHN at f = 289 kHz and f = 486 kHz, respectively. These results agreed with those obtained using Kelvin’s equation, which predicted D = 0.34λ. 相似文献
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The secular equation (GF - Eλ)L = 0 contains more force constants than can be calculated from the equations formulated using the frequencies. For a 3 × 3
matrix, there are 6 force constants but only 3 frequencies. Attempts were made by others to estimate all the 6 constants to
satisfy the frequencies and Coriolis constants and rotation distortion constants. However, many attempts are not made in these
estimations to satisfy the intensities. A full complement of equations is derived to evaluate all the force constants combining
the intensity equationsI =L’A withLL’ =G and evaluated the force constants ofA
1 species of CH3Cl and CD3Cl. A simple analysis of a 2 × 2 matrix shows thatF
12/F
22=G
12
−1
/G
22
−1
as reported earlier. 相似文献
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Infrared intensity analysis of MXY2 type molecules has been attempted. The dipole momentμ of C=O is obtained to be different for different moleculesviz. for CH2O, 1.9052; for COCl2, 1.1517; for COF2, 0.6340; and for COBr2, 0.7687. Similarly in the case of CSF2 and CSCl2
μ
C=S it was found to be 0.2473 and 0.2983 respectively. This shows that the effect of the electro-negative halogen atoms is very
important.
Presented at the ‘National Symposium on Molecular Spectroscopy’, Annamalai University, Annamalainagar on 28 February 1976. 相似文献
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