激光驱动含能复合飞片速度特性

采用真空磁控溅射方法制备了CuO/Al2O3/Al,(CuO/Al)Ⅱ/CuO/Al2O3/Al,(CuO/Al)Ⅷ/Al2O3/Al三种复合飞片,利用激光共聚焦显微镜和扫描电镜对复合飞片进行表征,结果表明,不同材料膜层的分界面清晰可见,复合薄膜的表面结构致密,颗粒基本尺寸可以达到nm级,均匀性好。利用光子多普勒测速技术对三种复合飞片速度进行测量,结果表明:将飞片靶放置在空气电离点偏前的位置(入射激光方向),增大聚焦光斑,能改善激光电离空气引起的能量屏蔽作用;含能烧蚀层CuO/Al的存在,有助于提高飞片速度。在含能薄膜烧蚀层厚度一定的情况下,增大周期、减小每层薄膜厚度,有助于提高含能薄膜反应程度,减小飞片上升沿时间。在同等激光能量密度下,(CuO/Al)Ⅷ/Al2O3/Al的上升沿时间低于(CuO/Al)Ⅱ/CuO/Al2O3/Al。     

Doppler程序对金红石型TiO2的空位缺陷研究

金红石型TiO2是一种非常好的稀磁半导体材料,其自身的本征缺陷与室温铁磁性起源密切相关。本文利用Doppler程序在广义梯度理论（GGA）的基础上,计算了正电子在金红石型TiO2块材中不同缺陷处的湮没寿命。主要包括自由态正电子的湮没寿命,单空位和双空位处束缚态正电子的湮没寿命。并从理论上给出了含有空位缺陷时金红石型TiO2的符合多普勒展宽能谱。     

PIV measurements of velocities and concentrations of wood fibres in pneumatic transport

A method for simultaneous measurement of the concentration and velocity of wood fibres suspended in air was developed. The velocity of the wood fibres was measured by the use of particle image velocimetry (PIV). The concentration of wood fibres was measured using the raw images from the PIV equipment as input data. An image processing procedure was used to determine the volume fraction of the fibre particles in the images. The method gave good qualitative and quantitative results for low volume fractions of fibres; for higher volume fractions the quantitative results were unsatisfactory.Latin letters C Concentration of fibres [g/m³] - d Diameter of fibre [m] - M_w Water mass [kg] - M_f Fibre mass [kg] - m Calibration mass flow [kg/s] - m₂₅ Calibration mass flow at C=25 g/m³ [kg/s] - n Fan rpm [-] - t Thickness of light sheet [m] - t Time between laser pulses [s] - U_i Velocity component in i-direction [m/s] - v Streamwise velocity [m/s] - v_average Average streamwise velocity [m/s] - x_i Particle displacement in i-direction [m] Greek letters _f Volume fraction of fibres [-] - _average Average volume fraction of fibres [-] - Area fraction of fibres in image [-] - Density of fibre particle [kg/m³]     

STUDY OF AXIAL VELOCITY IN GAS CYCLONES BY 2D-PIV, 3D-PIY, AND SIMULATION

The axial velocity distribution in a gas cyclone has been examined with two-dimensional particle image velocimetry (2D-PIV) and three-dimensional particle image velocimetry (3D-PIV) experiments in this study. Due to the limitation of 2D-PIV configuration, the contamination generated by the strong tangential velocity in the cyclone can be registered in the axial velocity detected by 2D-PIV. Efficient methods are proposed in this work to remove this contamination. The contamination-removed 2D-PIV data agree well with 3D-PIV results. The distributions of the axial velocity are also computed by the Reynolds stress model (RSM) and verified using the PIV experimental results. Reasonable agreements are obtained.     

Analysis of regular and irregular acoustic streaming patterns in a rectangular enclosure

This study reports an experimental investigation of the non-linear phenomena of regular (classical) and irregular streaming patterns generated in an air-filled rigid-walled square channel subjected to the acoustic standing waves of different frequencies and intensities. The interaction of acoustic waves and thermoviscous fluids is responsible for these phenomena. The resonator’s walls are maintained at isothermal condition. Synchronized particle image velocimetry (PIV) technique has been used to measure the streaming velocity fields. The experimental results show that at a given excitation frequency, regular streaming flow patterns are observed up to a certain value of the excitation amplitude. As the amplitude increases beyond this limit, the regular streaming is distorted to an irregular flow structure. The regular and irregular streaming are classified in terms of streaming Reynolds number . It is found that for Re_s2<50, classical streaming flow patterns are established and then deform to irregular and complex shapes as Re_s2 exceeds 50.     

热毛细对流速度场测试研究

为了探索微重力状态下表面张力驱动流速度场的测试技术，本文在地面进行了模拟实验，对位于热壁下流体中气泡周围的表面张力驱动流进行了研究，并用ＰＩＶ技术测量了流场的速度分布．     

激光多普勒测速技术在气液两相流中的应用

本文采用激光颗粒动态分析仪(PDA)测量了钢包底部喷吹气液两相流中气泡的直径和气泡上升速度的分布;采用激光多普勒测速仪(LDA)测量了气液两相区和液体单相循环区液体速度场的分布。测量结果表明:气泡在脱离喷嘴上浮一定距离后,其大小基本保持不变;在气液两相区中,气泡速度和液体速度的分布均服从高斯分布;液体在单相区作循环流动,在侧壁与底部交接处,存在液体流动的“死区”。     

Transport of salts and micron-sized particles entrained from a boiling water pool

The entrainment of soluble (KI, CsI) and non-soluble (Al₂O₃) substances through droplets, which are produced by disintegrating steam bubbles at the surface of a boiling water pool, is determined in a pilot-scale facility. Integral measurements are conducted at steady-state conditions in an atmosphere of either pure steam or an air–steam mixture. The ratio of the entrained liquid mass flow and the gas mass flow through the pool, the entrainment factor, is determined for air–steam ratios between 0 and 0.47 kg/kg in the gas atmosphere and at constant total pressures between 2 and 6 bar. The influence of the vertical temperature profile in the gas atmosphere on the convective velocity field is demonstrated by phase Doppler anemometry and particle image velocimetry measurements at a location 2.1 m above the pool surface. The influences of nucleation and natural convection are demonstrated during slow de-pressurization of the facility at rates below 420 Pa/s.     

单镜头三维粒子成像测速

本文提出了一种用单镜头进行三维流场测量的方法，建立了包括摄录系统、数字图象处理及识别系统及流动装置的３Ｄ－ＳＣＰＩＶ系统。完成了现有条件下的原理性定量测量实验。