PSS瞬光瞬态颗粒测量装置的研制和应用

为了测量和分析瞬态喷雾过程的雾化特性，设计了激光瞬态颗粒测量装置，并以此对标准颗粒，医用喷雾器，柴油机喷嘴，结晶成核过程等作了验证试验，证明其具有测量准确，快速简便，自动化程度高等优点。     

图像法用于流化床颗粒运动速度测量的实验研究

借助于高速CCD研究了用图像法测量流化床内颗粒运动速度的可行性，在二维冷态流化床实验台上拍摄了流化床颗粒运动图像，并用互相关算法计算这些图像，得到了颗粒运动的瞬态速度场分布，取得了流化床内颗粒运动速度场的定量结果，为流化床运动特性研究提供了新的方法。     

用于测量柴油机气缸内碳粒浓度和火焰温度的光电系统

利用颗粒衍射原理，研制出一套用于测量柴油机气缸内局部瞬态碳粒浓度和火焰温度的光电测量系统。该系统采用分叉光纤，省去了一套复杂的光学分光组件。利用该测量系统对一台柴油机气缸内进行了相应测量，并分析了测量数据，结果表明活塞凹坑区的火焰温度和碳粒浓度相当高，在活塞的顶岸区，它们的循环变动很大。     

等离子喷涂过程中金属与陶瓷颗粒倾斜入射的数值模拟

本文利用有限元法，研究了等离子喷涂过程中喷涂角度对熔融颗粒沉积微观形貌的影响，计算了金属Ni颗粒和陶瓷Al2O3颗粒在一定喷涂角度下的微观变形形貌和瞬态压力峰值。结果表明，喷涂角度对液滴甫展等效直径，延展因子，上游比例系数以及瞬态碰撞压力峰值都有显著影响。研究结果对进一步深入研究致密涂层的形成以及涂层微观组织与宏观性能之间的有关系提供了理论依据。     

利用高压探头和电阻分压器进行高压测量的性能比较

本文以电快速瞬变脉冲群发生器为例，针对电磁兼容研究领域中的高压脉冲瞬态信号的获取和测量问题展开了讨论。通过原理分析、实验结果比较，对电阻型高压分压器和高压探头这两种高压衰减器的频率响应特性进行了评估，确定了更加科学、准确、简便的高压脉冲瞬态信号的测量方法，并提出了测量过程中的注意事项，对于电磁兼容领域中各种脉冲干扰量的研究具有一定参考价值。     

金属氧化物纳米流体的导热性能研究

采用瞬态热线法测量了4种不同种类、不同体积份额配比的纳米流体的导热系数,分析了纳米颗粒属性、体积分数、悬浮稳定性及温度等因素对纳米流体导热系数的影响.实验结果表明,在流体中加入纳米颗粒将显著提高流体的导热系数.     

《颗粒粒径的光学测量技术及应用》即将出版

由中国颗粒学会理事、上海理工大学王乃宁教授等撰写的《颗粒粒径的光学测量技术及应用》一书即将由中国原子能出版社于 2 0 0 0年上半年出版。为充分反映颗粒测量技术的最新进展 ,该书除介绍传统的颗粒测量方法外 ,重点讨论了目前已在国内外得到十分广泛应用的各种激光测粒仪和光散射测粒技术。全书理论密切联系实际 ,对各种方法的基本原理、工作特点、适用范围、最新发展等都有详细的分析和讨论 ,并对其具体应用 ,如固体颗粒 (粉末 )和液滴的测量、微米级和纳米超细颗粒的测量、气体和液体中颗粒相粒径和浓度的测量、稳态和瞬态测量、离线…     

等离子喷涂过程中金属与陶瓷颗粒倾斜入射的数值模拟

本文利用有限元法 ,研究了等离子喷涂过程中喷涂角度对熔融颗粒沉积微观形貌的影响 ;计算了金属Ni颗粒和陶瓷Al2 O3 颗粒在一定喷涂角度下的微观变形形貌和瞬态压力峰值。结果表明 ,喷涂角度对液滴舍甫展等效直径、延展因子、上游比例系数以及瞬态碰撞压力峰值都有显著影响。研究结果对进一步深入研究致密涂层的形成以及涂层微观组织与宏观性能之间的关系提供了理论依据。     

LabVIEW的瞬态热线法导热系数测试系统的开发

研制了一种基于LabVIEW平台的瞬态热线法测量导热系数的测试系统,从测量原理、系统硬件、系统软件、数据处理等方面说明了该系统的设计过程.采用有限容积法对瞬态热线法导热系数的测量过程进行数值模拟,并建立迭代算法处理实验数据.通过LabVIEW调用动态链接库混合编程实现了LabVIEW平台对Fortran语言的调用,集成了数据采集和处理模块,实现了测试系统的自动化.通过测量氮气的导热系数验证了该测试系统的可靠性.     

瞬态热线法导热系数测量的数值模拟

利用有限元方法对瞬态热线法导热系数测量进行了数值模拟,对各种因素如加热功率、热线半径以及实验温度等对测量过程的影响进行了分析,并将模拟得到的温升曲线与实验测量得到的温升曲线进行了比较,结果表明:通过选择适当的参数值,模拟曲线可以与实测曲线吻合得很好,实验值与模拟值的偏差小于实验结果的不确定度.本结果的获得对进一步理解瞬态热线法导热系数测量过程,提高导热系数测量技术水平具有借鉴意义.     

提高激光粒度仪测量准确性的补偿方法

通过理论推导以及对实测数据的回归分析,得到了激光粒度仪环形探测器各环信号的两个补偿系数。并对国家标准物质研究中心提供的标准颗粒ＧＢＷ（Ｅ）１２０００５进行了测试,证了该方法可有效地提高激光粒度测量的准确性。     

Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 2. Closure study

Spectral particle extinction coefficients of atmospheric aerosols were measured with, to the best of our knowledge, a newly designed differential optical absorption spectroscopy (DOAS) instrument. A closure study was carried out on the basis of optical and microphysical aerosol properties obtained from nephelometer, particle soot/absorption photometer, hygroscopic tandem differential mobility analyzer, twin differential mobility particle sizer, aerodynamic particle sizer, and Berner impactors. The data were collected at the urban site of Leipzig during a period of 10 days in March 2000. The performance test also includes a comparison of the optical properties measured with DOAS to particle optical properties calculated with a Mie-scattering code. The computations take into account dry and ambient particle conditions. Under dry particle conditions the linear regression and the correlation coefficient for particle extinction are 0.95 and 0.90, respectively. At ambient conditions these parameters are 0.89 and 0.97, respectively. An inversion algorithm was used to retrieve microphysical particle properties from the extinction coefficients measured with DOAS. We found excellent agreement within the retrieval uncertainties.     

基于原位微锻造冷喷涂技术的金属涂层研究进展

原位微锻造冷喷涂技术是一种通过在喷涂粉末中混入大尺寸喷丸颗粒,借助喷丸颗粒对已沉积涂层的锤击效应实现喷涂沉积层的原位致密化,同时提高沉积体的自身强度和与基材的结合强度的技术.为此,对原位微锻造冷喷涂技术的发展状况进行了总结.首先,对该技术工作原理进行了简要介绍,并探讨了喷丸体积分数、颗粒尺寸等参数对涂层的影响;其次,探...     

Particle formation in ambient MALDI plumes

The ablated particle count and size distribution of four solid matrix materials commonly used for matrix-assisted laser desorption ionization (MALDI) were measured with a scanning mobility particle sizer (SMPS) combined with a light scattering aerodynamic particle sizer (APS). The two particle sizing instruments allowed size measurements in the range from 10 nm to 20 μm. The four solid matrixes investigated were 2,5-dihydroxybenzoic acid (DHB), 4-nitroaniline (NA), α-cyano-4-hydroxycinnamic acid (CHCA), and sinapic acid (SA). A thin film of the matrix was deposited on a stainless steel target using the dried droplet method and was irradiated with a 337 nm nitrogen laser at atmospheric pressure. The target was rotated during the measurement. A large number of nanoparticles were produced, and average particle diameters ranged from 40 to 170 nm depending on the matrix and the laser fluence. These particles are attributed to agglomeration of smaller particles and clusters and/or hydrodynamic sputtering of melted matrix. A coarse particle component of the distribution was observed with diameters between 500 nm and 2 μm. The coarse particles were significantly lower in number but had a total mass that was comparable to that of the nanoparticles. The coarse particles are attributed to matrix melting and spallation. Two of the compounds, CHCA and SA, had a third particle size distribution component in the range of 10 to 30 nm, which is attributed to the direct ejection of clusters.     

超音速火焰(HVOF)喷涂过程中颗粒行为数值模拟的研究进展

介绍了近年来描述HVOF喷涂过程中颗粒行为的数学模型,并结合不同粉末的特点给出了相应的模型修正.简要总结了数值模拟的研究成果,从颗粒的尺寸、形貌、密度及喷涂距离等方面分析了不同工艺参数对喂料颗粒在喷涂过程中状态变化的影响以及与涂层组织和性能之间的关系,从而为深入了解HVOF喷涂工艺的特点提供了一条有效途径,也为热喷涂的模拟研究提供了一些参考和借鉴.     

两种付立叶变换光学系统的信息处理能力的比较

讨论了平行光付立叶变换系统与会聚光付立叶交换系统的空间带宽积的不同计算方法，比较了两者的特点与数量关系，给出的计算实例表明，空间带宽积在优化激光粒度仪设计中占有中心地位。     

Investigation on the atomization characteristics of a solid-cone spray for dust reduction at low and medium pressures

Water spray is the most widely used means of wet dust reduction, and its atomization parameters are directly related to the effect of dust reduction. In order to obtain the atomization properties of solid-cone spray for dust reduction, the paper used droplet velocity and particle size to characterize its atomization characteristics. The Phase Doppler Particle Analyzer (PDPA) was used to precisely measure droplet sizes and velocities of a solid-cone spray at distances of 15?cm, 25?cm and 45?cm horizontally from the nozzle outlet, using low and medium spray pressures. The results show that the droplet size was fluctuant before spray pressure increasing to 2.0?MPa and then decreased gradually with the increasing of spray pressure. The droplet velocity increased with the raising spray pressure and the velocity at 45?cm is the minimum. The droplet size measurements taken 45?cm from the nozzle exhibited more complex slope changes in particle size curve that were not existed at the closer distances spray of 15?cm or 25?cm, which implies that the near-field spray is more stable than far-field spray. This study is of important significance for further understanding the characteristics of solid-cone spray and guiding its application in dust reduction.     

The control of particle size distribution for fabricated alumina nanoparticles using a thermophoretic separator

Control of the particle size distribution of fabricated alumina nanoparticles from general alumina powder with a large geometric standard deviation (GSD) was studied. A thermophoretic separator was used to control the GSD of the nanoparticles, and unevaporated and primary particles were separated to yield a small GSD. The fabricated nanoparticles were characterized by field emission scanning electron microscopy (FESEM) and a scanning mobility particle sizer (SMPS). We confirmed that the GSD of the nanoparticles was controlled by the thermophoretic separator. A temperature difference between 79 K and 151 K was applied to the thermophoretic separator for control of the nanoparticle GSD. The GSD of the fabricated alumina nanoparticles was improved from 1.74 to 1.44.     

An experimental study on the spray characteristics of pressure nozzle in a fluid bed granulation

The particles with a narrow size distribution are proper products in a fluid bed granulation and coating. As well, the process efficiency is one of the most important parameters, and the wall deposition of sprayed liquid reduces it. The modality of spray volume distribution is a key parameter in the definition of particle size distribution and process efficiency. This work is done in two steps: In the first step, an experimental study on spray characteristics including spray flux distribution, spray cone angle, and discharge coefficient is conducted. Based on the experimental data, the curves of liquid volume flux versus nozzle pressure and height are obtained. The results indicate that the flux distribution changes significantly with even small pressure and height changes. In the second step, the granulation process is carried out in a semi-industrial conical fluid bed, and the particles size distribution curves and the deposited mass on the bed wall are obtained. The results show that the precise determination of the spray flux distribution is an appropriate way to predict the well-advised nozzle pressure/height in order to achieve the narrow particle size distribution and high efficiency of the process.     

Inline method of droplet and particle size distribution analysis in dilute disperse systems

In the present article a measurement method of particle size distributions (PSD) in industrial installations which use a dispersed phase of low concentration (like spray dryers or spray scrubbers) is introduced. A new type of inline-measurement system has been developed and designed to work in spray drying conditions. A standard digital camera is used to record shadows of flowing particles inside the spray drying chamber. Collected images were analyzed by a newly developed software which recognizes particles only in the focus area and eliminates several types of artifacts. The constructed prototype of the PSD inline-analyzer was installed and used to monitor large laboratory scale spray dryer. All data collected by the designed system during the spray drying experiments were compared with data measured with an offline reference system to show accuracy of the new measurement technique.