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叙述了低温等温情况下,重力和界面张力平衡的激光惯性约束聚变靶丸内表面液氢层分布的Young-Laplace(YL)方程.为了得到靶丸壳内连续液氢层分布的有效解,考虑了液体与固体(衬底)分子间的London-van der Waals力以及该力的迟滞影响.计算结果表明,只有在靶丸内部引力为零或者固体液体分子间的London常量为无穷大时,才能得到等温环境中有均匀厚度的连续液氢层.
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基于充模过程的两相黏弹性流体模型, 采用同位网格有限体积法, 结合浸入边界法和界面追踪的复合水平集流体体积方法实现了带嵌件型腔内充模过程的动态模拟. 基于上述模型和算法模拟了熔体前沿界面及熔接线的动态演化过程, 而且通过线性应力-光学定律得到了熔接线附近的流动诱导应力分布情况; 讨论了熔体温度及模具温度对熔接线区域凝固层厚度的影响. 数值结果表明: 本文提出的方法可用于模拟复杂型腔内的充模过程以及熔接线的自动追踪; 由于聚合物黏弹性熔体流动的复杂性, 当两股熔体相遇后, 熔接线不同位置的应力分布变化较大; 熔体或模具温度越高, 熔接线区域凝固层厚度越薄, 提高熔体或模具温度能够改善甚至消除充模过程中的熔接线. 相似文献
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气流床煤气化炉炉壁渣层流动与传热模拟 总被引:1,自引:0,他引:1
本文对气流床煤气化炉内高温合成气和渣层的流动、换热、相变过程进行了分析,在合理简化和假设的基础上建立了描述渣层流动、热质传递和相变的渣层数理模型.通过对气化炉内气固两相流和化学反应的模拟,得到灰渣颗粒在气化炉壁面的沉积率,进而对所建立的模型应用SIMPLE算法进行了求解,获得了气化炉壁面灰渣流动、传热和相变过程的数值模拟结果.结果表明:壁面温度对渣层厚度的影响较炉膛温度要大得多;当壁面温度不变时,炉膛温度增加,固态渣层厚度减少;炉膛温度不变时,壁面温度降低,固态渣层厚度增加. 相似文献
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计算了InGaAs/AlGaAs量子阱的激射波长与阱垒厚度的关系,并通过Rsoft软件计算了不同温度下的材料增益特性.计算并分析了渐变层厚度对分布布拉格反射镜(distributed Bragg reflectors,DBRs)势垒尖峰及反射谱的影响,通过传输矩阵理论得到P-DBR和N-DBR的反射谱和相位谱.模拟了垂直腔面发射激光器(vertical surface emitting lasers,VCSEL)结构整体的光场分布,驻波波峰与量子阱位置符合,基于有限元分析模拟了氧化层对电流限制的影响.通过计算光子晶体垂直腔面发射激光器(photonic crystal vertical cavity surface emitting lasers,PC-VCSEL)中不同的模式分布及其品质因子Q,证明该结构可以有效地实现基横模输出.通过光刻、刻蚀、沉积、剥离等半导体工艺成功制备出氧化孔径为22μm的VCSEL和PC-VCSEL,VCSEL的阈值电流为5.2 mA,斜率效率0.67 mW/mA,在不同电流光谱测试中均是明显的多横模输出;PC-VCSEL的阈值电流为6.5 mA,基横模输出... 相似文献
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通过求解一维稳态的尘埃等离子体鞘层模型,得到了等离子体鞘层势、正离子密度、电子密度和尘埃颗粒密度随一维横向的分布,Bohm判据及鞘层边界无量纲Bohm速度随尘埃密度的变化曲线,尘埃颗粒的带电量和尘埃密度的关系,尘埃颗粒的温度对尘埃颗粒自身在鞘层中分布的影响。结果表明,随着尘埃密度的增加,鞘层的厚度在减小,鞘层内的电子密度在下降,而且尘埃颗粒的带电量也在逐渐减少;随着尘埃温度的增加,鞘层的厚度减小,电子密度下降,而且鞘层附近的尘埃颗粒在逐渐增多。 相似文献
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Baolu Shi Qing Cao Dingjiang Xie Weikang Peng Ningfei Wang 《Proceedings of the Combustion Institute》2019,37(4):4329-4336
To utilize sustainable biofuel, the current study proposes a novel combustion technique that directly burns liquid ethanol without a spray system. Two swirling air flows are induced by tangentially injected the gas from two concentric tubes at different stages. The liquid ethanol is fed by a liquid tank at the center. At the beginning methane flame assists in preheating the system to vaporize liquid ethanol and ignite the vapor. Thereafter methane is switched off, and liquid ethanol can be continuously vaporized through self-burning released heat. The heat and mass transfer processes are examined to illustrate such self-sustained burning–heating–evaporating system. The ethanol flow rate is gradually increased to provide different heat output. The flame structures, temperature distributions and pollutant emissions are carefully examined. The results show that the ethanol can be steadily burned to provide heat output between 0.7 and 2.5?kW. Generally a blue flame is obtained, and the NOx and CO concentrations are ultralow. By increasing ethanol flow rate to exceed 8?mL/min, an unsteady, sooting flame is observed owing to incomplete evaporation and poor mixing. A parametric study is conducted to evaluate the influences of liquid tank position, flow rate and tip structure on the combustion characteristics. Additionally, an optimal operation condition is proposed. The current study provides a promising method to burn low-boiling liquid fuel in a clean, efficient and compact way. 相似文献
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I. V. Marchuk 《Journal of Engineering Thermophysics》2009,18(3):227-237
In this paper, steady thermocapillary flow in a thin horizontal layer of a viscous incompressible liquid with a free surface
is considered. An axially symmetric steady problem with a localized thermal action on a horizontal liquid layer with a deformable
free surface is solved in a thin-layer approximation. In addition to the thermocapillary effect, the model takes into account
the capillary pressure caused by the free surface variable curvature and the convective mechanism of heat transfer in the
liquid. Analytical expressions for the velocity vector components as functions of the liquid layer thickness and surface temperature
are obtained. The free surface and velocity profiles caused by various kinds of heating are calculated. The influence of convective
heat transfer on the flow pattern is analyzed. 相似文献
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I. S. Altarev Yu. V. Borisov A. B. Brandin V. F. Ezhov S. N. Ivanov G. K. Kunstman V. M. Lobashev V. A. Nazarenko V. L. Ryabov A. P. Serebrov R. R. Taldaev 《Physics letters. A》1980,80(5-6):413-416
A liquid hydrogen source of ultra-cold neutrons (UCN) developed for an experimental search for the electric dipole moment of the neutron is described. The results of an investigation of the yield of UCN from gaseous, liquid, and solid hydrogen as a function of temperature are presented. The UCN counting rate obtained at the output of the 6 × 7 cm2 neutron guide tube is 5 × 104 n/s. This counting rate corresponds to a flux of neutrons whose velocity along the axis of the neutron guide tube is below 7 m/s. Preliminary measurements of the UCN yield from liquid and solid deuterium have been carried out. 相似文献
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Anirban Garai 《Journal of Turbulence》2013,14(8):1-23
Surface layer plumes, thermals, downdrafts and roll vortices are the most prominent coherent structures in an unstably stratified boundary layer. They contribute most of the temperature and vertical velocity variance, and their time scales increase with height. The effects of these multi-scale structures (surface layer plumes scale with surface layer depth, thermals scale with boundary layer height and the resulting roll vortices scale with convective time scale) on the surface temperature and ground heat flux were studied using turbulence measurements throughout the atmospheric boundary layer and the surface temperature measurements from an infrared camera. Plumes and thermals imprint on the surface temperature as warm structures and downdrafts imprint as cold structures. The air temperature trace shows a ramp-like pattern, with small ramps overlaid on a large ramp very close to the surface; on the other hand, surface temperature gradually increases and decreases. Turbulent heat flux and ground heat flux show similar patterns, with the former lagging the latter. The maximum values of turbulent heat flux and ground heat flux are 4 and 1.2 times the respective mean values during the ejection event. Surface temperature fluctuations follow a similar power-law exponent relationship with stability as suggested by surface layer similarity theory. 相似文献
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近年来,随着我国互联网云计算的不断发展,云计算技术被应用于诸多领域。针对传统石油化工领域中储罐液仪表存在的罐内压力检测精准度差、温度感应灵敏度低与储罐液状态数据分析面窄等问题,提出云计算下石油化工罐区储罐液仪表设计。通过大数据运算核心进行框架构建,在此基础上,采用PCJD气流密度差算法、微感热源运算单元与数据流云算技术,对传统储罐液仪表进行设计改进,从问题的根源进行针对性解决。仿真对比试验证明,提出的云计算下石油化工罐区储罐液仪表设计,具有罐内液压力数据反馈精准度高,温度感应灵敏度高、储罐液综合数据分析速度快、数据分析完整度高等优点。 相似文献
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The effect of a conducting body with a large heat capacity on the thermal state of a hydrogen plasma in the boundary surface layer is analyzed. It is shown that, under certain conditions, the energy accumulated in the plasma within the boundary layer can be efficiently transferred to the conducting body; this leads to plasma overcooling. The mathematical model of plasma incorporates mechanisms for convective heat exchange and heat conduction. The possibility is analyzed of the existence of nonequilibrium recombination states with inverse population in the overcooled wall plasma. It is shown that the maximum gain (a few tenths of cm?1) on hydrogen nuclei is achieved at the 3-2 transition for the following initial parameters: the plasma pressure is 1–3 atm, the plasma temperature is 0.5 eV, the tungsten surface temperature is 300 K, and the body radius is 0.5–1.0 m. 相似文献
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The effect of hydrogen absorption on electrical resistance with temperature for TiNi and TiNi-Cr thin films was investigated. The TiNi thin films of thickness 800 Å were deposited at different angles (? = 0°, 30°, 45°, 60° and 75°) under 10?5 Torr pressure by thermal evaporation on the glass substrate at room temperature. A layer of Cr of thickness 100 Å was coated on the TiNi thin films. The changing rate of hydrogen absorption increases after Cr layer coating because Cr enhances the catalytic properties of hydrogen absorption in thin films. The rate of hydrogen absorption increases with temperature at lower range but at higher range of temperature it was found to decrease and also it was found that the hydrogen absorption increases with angle of deposition. 相似文献