激光衍射仪在雾化油滴粒度测量上的应用

本文简述了应用以Fraunhoffer几何光学理论为基础的LPI—2型激光衍射粒径仪测量雾化油滴尺寸和分布特性,阐明了这一应用对深入开展油雾化研究的重要意义。     

气泡雾化喷嘴在不同液体物性下的喷雾特性研究

利用PS-Ⅱ激光衍射粒度仪测量分析了气泡雾化喷嘴在雾化不同动力粘度，不同表面张力的液体时的特性，发现液体的粘性对于气泡雾化效果影响程度不大，随着动力粘度的增加，平均直径稍有增大，当动力粘度很高时由于泡状流更容易形成，所以平均直径有所减小，而液体表面张力的变化对于雾化质量的影响显。     

火花点火发动机激光诱导荧光及散射测量技术应用研究

本文就汽车发动机的激光测量技术问题，重点介绍了散射光法及激光诱导荧光法在发动机研究开发过程中的应用及其机理。这些方法对电子控制稀燃火花点火发动机的设计和优化具有重要意义。     

便携式超声波流量计在供水流量测量中的应用及注意事项

介绍了便携式超声波流量计在制药行业的应用，使用方法及注意事项。     

长测距三维激光扫描仪在露天矿山测量中的应用

利用长距离三维激光扫描仪进行露天矿山测量可以实现不可估量的测量成效.通过分析长距离三维激光扫描仪在露天矿山测量原理,以某矿山工程为例,利用三维激光扫描仪对矿山测量中的数据采集、处理、对比进行系统化分析,总结了三维激光扫描仪开展露天测量的优势及注意事项.     

激光散射理论在汽轮机蒸汽湿度及水滴直径测量中的应用

蒸汽湿度的存在不但降低汽轮机组的运行效率,而且会引起严重的叶片水蚀,给汽轮机组的经济性和安全性带来很大的危害.根据激光散射理论和Mie散射理论,利用半导体激光器发射出三个不同波长的光能够在线测出汽轮机末级蒸汽湿度及水滴颗粒大小和分布,为监控和减少湿蒸汽对汽轮机的危害提供最直接的数据.图5表1参11     

激光数码全息技术在两相流三维空间速度测量中的应用

研究了利用激光数码全息技术实现两相流三维空间速度场测量的方法.用1台脉冲激光器照射两相流,平面光和颗粒衍射光发生干涉,在数码相机的CCD平面上生成全息图像.用1台跨帧数码像机连续拍摄两相流全息图像,对全息图应用基于小波变换的三维图像重建算法,在计算机上实现物体三维图像的重建,再利用图像互相关测速技术从连续的重建三维图像中提取两相流三维空间的速度场.实验中将2只置于不同空间位置的喷嘴向不同方向喷射雾化的气液两相流,并对生成的流场进行测量.结果表明该方法可以实现两相流三维空间速度场测量.     

激光诱导磷光测温技术在缸内温度测量中的应用

将激光诱导磷光测温技术应用到发动机缸内气体的二维温度测量中.其原理是利用Dy:YAG磷光剂受355 nm波长的激光激发后辐射的458 nm和494 nm磷光强度比进行温度测量,实验在一台侧向换气的光学发动机上进行,测试了该发动机压缩行程的二维温度分布,与由缸压计算的缸内平均温度比较,误差均小于5%.     

激光精密测量技术在大型水轮发电机组安装中的应用

为提高大型水轮发电机组安装的测量精度和效率,提出了AT901-LR激光跟踪仪测量方法,即利用Leica公司生产的AT901-LR跟踪仪配合T-Probe、球棱镜、基座及专用工装,采用统一的三维控制网的点位布设,通过对水轮机部件、发电机定子组装过程测量的实际应用,并与测圆架测量结果进行比较。结果表明,测量结果偏差极小,精度高,符合现场安装要求,从而验证了AT901-LR激光跟踪仪测量方法具有较高的精度,这也为大型水电机组安装提供了一种新型的测量工具和测量方法。     

磁记忆等检测技术在锅炉压力容器焊接残余应力测量中的应用简析

针对目前焊接残余应力常用的几种无损测量方法进行了简单介绍和比较。提出了一种新的无损测量方法——金属磁记忆检到技术。分析了该技术在锅铲压力客器焊缝中的应用前景及存在的问题。     

Measurement of droplet size distribution in core region of high-speed spray by micro-probe L2F

In order to investigate the distribution of droplet sizes in the core region of diesel fuel spray, instantaneous measurement of droplet sizes was conducted by an advanced laser 2-focus velocimeter （L2F）. The micro-scale probe of the L2F is made up of two foci and the distance between them is 36 lain. The tested nozzle had a 0.2 mm diameter single-hole. The measurements of injection pressure, needle lift, and crank angle were synchronized with the measurement by the L2F at the position 10 mm downstream from the nozzle exit. It is clearly shown that the droplet near the spray axis is larger than that in the off-axis region under the needle full lift condition and that the spatial distribution of droplet sizes varies temporally. It is found that the probability density distribution of droplet sizes in the spray core region can be fitted m the Nukiyama-Tanasawa distribution in most injection periods.     

Modeling of particle formation by spray pyrolysis using droplet internal circulation

A mathematical model is developed to predict the morphology of powders prepared by spray pyrolysis process. For high velocity solution droplets, the contours of constant solute concentration and temperature coincide with the streamlines. Based on this fact, the liquid phase transport equations are simplified and solved, numerically. Variation of droplet surface temperature and solute mass fraction versus time are presented. In addition, the temperature and the solute mass fraction distributions within the droplet are provided. Using the solute mass fraction distribution, the model predicts whether the final particle is fully-filled or hollow with two cavities.     

A simplified prediction of droplet velocity distributions in a spray

The coupled droplet size and velocity distribution in a spray has been predicted using the maximum entropy formalism and fundamental conservation constraints. The shape of the droplet size distribution is in good agreement with the Rosin-Rammler distribution. The distribution of velocity at any particular droplet size is Gaussian in shape. A simple drag model is used to propagate the distribution downstream through a gas field having a constant and uniform velocity. It shows that in the absence of turbulence and other disturbances, the velocity distributions collapse toward their means long before those mean velocities reach the gas-phase velocity.     

Advances and challenges in droplet and spray combustion. I. Toward a unified theory of droplet aerothermochemistry

Major theoretical accomplishments in droplets and sprays in the twentieth century are reviewed in this two-part article, with emphasis focused upon the evolution of scientific concepts, paradigms and methodologies. A structural spray theory, which was developed from an early view of isolated droplets, has evolved in to a new view that the interacting droplet and meso-scale structures and clusters of many-droplet systems are also fundamental entities in practical sprays. The first part of this work addresses the major concepts in analytical developments, which serve as the framework of modern theories of an isolated and interacting droplet. Outstanding issues and critical bottlenecks that have prevented further advancement of the existing analytical theory of droplet physics are examined, and an emerging research trend in a unified theory of droplet phenomena discussed. Recent accomplishments and future prospects of a unified theory are presented to complement the status of this special branch of droplet science and its future application.     

Temperature distribution on inclined plate caused by interaction with supersonic jet

IntroductionThe phenomena of the impingement of a supersonicjet on a solid obstacle is very interesting and importantin relation to the aeronautical and other industrialengineerings[']-l']. A large number of papers hadconcerned with the impingement on a perpendicularplate and evidenced the flow phenomena and thepressure distribuhon on a plate and so on. However, theinvestigation of the impingement on an inclined platecan only be found in merely several papers['-']. Ih thesestudies, it is menti…     

A spherical cell model for multi‐component droplet combustion in a dilute spray

A model for sphericosymmetric thin‐flame combustion of a multi‐component fuel droplet in a dilute spray has been developed using a unit cell approach. The gas‐phase transport has been modelled as convective–diffusive while the liquid‐phase processes as transient–diffusive. Convective heat and mass transfer condition has been used at the cell surface. The results indicate that evaporation and combustion characteristics of the droplet are strongly affected by the variation of both ambient conditions and convective transfer coefficients. Using the model, the effects of droplet spacing in spray, ambient oxidizer concentration, ambient temperature and pressure have been considered. Droplet life increases with decrease in droplet spacing, ambient temperature and ambient oxidizer concentration. However, droplet life has a weak dependence on ambient pressure. Copyright © 2001 John Wiley & Sons, Ltd.     

The effect of ambient pressure on the evaporation of a single droplet and a spray

The effect of ambient pressure on the evaporation of a droplet and a spray of n-heptane was investigated using a model for evaporation at high pressure. This model considered phase equilibrium using the fugacities of the liquid and gas phases for the behavior of a gas being real, and its importance in the calculation of the evaporation of a droplet or spray at high pressures was demonstrated. For the evaporation of a single droplet, the fact that the droplet's lifetime increased with pressure at a low ambient temperature, but decreased at high temperatures, was explained with pressure and the droplet's temperature determining phase equilibrium. In this study, it was also found that the evaporation of a spray can be explained in terms of multiplex dependencies of the atomization and evaporation of a single droplet. The evaporation of a spray was enhanced by increasing the ambient pressure and this effect was more dominant at higher ambient temperatures.     

Effects of fuel droplet size on soot formation in spray flames formed in a laminar counterflow

The effects of fuel droplet size on soot formation in spray flames formed in a laminar counterflow are investigated experimentally and numerically. Sauter mean diameter (SMD) of quasi-monodispersed fuel spray (n-decane) is carefully controlled independently from the other spray characteristics using a frequency-tunable vibratory orifice atomizer, and the two-dimensional spatial distributions of soot volume fraction and soot particle size are measured by laser induced incandescence (LII) and time resolved LII (TIRE-LII), respectively. In addition, the soot formation processes are examined in detail by a two-dimensional direct numerical simulation (DNS) employing a kinetically based soot model with flamelet model. The results show that the soot formation area and location are strongly affected by the SMD of the fuel spray. As the SMD of the fuel spray increases, the average soot formation area expands, whereas local suppression of soot formation is instantaneously observed in the spray flames because of the appearance of groups of unburned droplets. The size of soot particles tend to be larger in the outer part of the soot formation area compared to soot in the inner part. This is because the surface growth of soot particles markedly proceeds compared to the coagulation and oxidation.     

Direct simulation of spray cooling: Effect of vapor bubble growth and liquid droplet impact on heat transfer

Numerical modeling of multiphase flow using level set method is discussed. The 2-D model considers the effect of surface tension between liquid and vapor, gravity, phase change and viscosity. The level set method is used to capture the movement of the free surface. The detail of incorporating the mechanism of phase change in the incompressible Navier–Stokes equations using the level set method is described. The governing equations are solved using the finite difference method. The computer model is used to study the spray cooling phenomenon in the micro environment of about 40 μm thick liquid layer with vapor bubble growing due to nucleation. The importance of studying the heat transfer mechanism in thin liquid film for spray cooling is identified. The flow and heat transfer details are presented for two cases: (1) when the vapor bubble grows due to nucleation and (2) merges with the vapor layer above the liquid layer and when a liquid droplet impacts the thin liquid layer with vapor bubble growing.     

Experimental and Numerical Evaluation of the Performance of Supersonic Two-Stage High-Velocity Oxy-Fuel Thermal Spray （Warm Spray） Gun

The water-cooled supersonic two-stage high-velocity oxy-fuel (HVOF) thermal spray gun was developed to make a coating of temperature-sensitive material,such as titanium,on a substrate.The gun has a combustion chamber (CC) followed by a mixing chamber (MC),in which the combustion gas is mixed with the nitrogen gas at room temperature.The mixed gas is accelerated to supersonic speed through a converging-diverging (C-D) nozzle followed by a straight passage called the barrel.This paper proposes an experimental procedure to estimate the cooling rate of CC,MC and barrel separately.Then,the mathematical model is presented to predict the pressure and temperature in the MC for the specific mass flow rates of fuel,oxygen and nitrogen by assuming chemical equilibrium with water-cooling in the CC and MC,and frozen flow with constant specific heat from stagnant condition to the throat in the CC and MC.Finally,the present mathematical model was validated by comparing the calculated and measured stagnant pressures of the CC of the two-stage HVOF gun.