ISSN:0934-0866    

DOI:10.1002/ppsc.19960130302

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe production of liquid sprays represents a key technology for a wide range of industrial proceses. Most applications currently use pressure or air‐assisted atomization, resulting in the production of polydisperese sprays. Recent advances in experimental and numerical techniques for investigating liquid spraying processes, however, have enabled a closer examination of parameter optimization, leading to the conclusion that in may cases, a much narrower size distribution, or even a monodisperse spray, may exhibit many advantages. Currently monodisperse droplet generators, or drop‐on‐demand generators, do not meet this challenge of producing monodisperse sprays, primarily owing to the very low volume flow rate of liquid which is atomized. In the present work, a monodisperse sprya generator is introduced, which overcomes this difficulty for many applica

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130303

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractMeasurements of droplet deformation during wall impingement were performed for ethanol droplets and water droplets with diameters ranging from 100 to 200 μm. The wall temperature is well above the Leidenfrost temperature of the droplet liquid. With monodisperse droplet streams and a special illumination technique, slow motion images of the phenomena can be obtained. Measurements with high temporal resolution below 1 μs are possible using a standard video camera. The experimental results are compared with numerical results, which were obtained by solving the three‐dimensional Navier‐Stokes equations for incompressible fluids including surface tension effects. The fluids are treated with the volume‐of‐fluid method and the free surface is modeled according to the continuum‐surface‐force model. Numerical and experimental results show g

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130304

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe particle size distribution of an aerosol generated from an aqueous system is difficult to analyse because of the shrinkage of the droplets due to solvent evaporation. These problems are very important for the characterization of medical nebulizers, since most of the drugs delivered via inhalation are water soluble. In situ methods for droplet size analysis, such as laser diffraction, phase Doppler anemometry and light scattering, do not determine either the initial or the equilibrium size distribution. With the residual technique, which means evaporating the droplets and measuring the size and concentration of the residuals, the instability of the aqueous droplets plays no role and the necessary radioactive labelling of the sprayed material allows a direct determination of the mass flow rate at the mouthpiece of the nebulizer. In this way it is possible to discriminate between the delivered drug solution and the water necessary to humidify the incoming air. The output of nebulizers of different designs is given for various operating conditions, filling volumes and solution concentrations. The measured droplet size distribution of a nebulizer is found to be fixed mainly by its internal impaction system.

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130305

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractA Diesel spray injected into a high‐pressure test chamber was investigated with two different holographic techniques. The usual off‐axis recording geometry was used to investigate the very early beginning of the injection. Double pulsing of the recording laser facilitated velocity measurements. By using two different reference angles for the two recording the two images can be separated upon reconstruction of the holograms. Thus superior image quality could be achieved. Processes leading to jet formation could be identified: the spray tip is periodically axially decelerated and radially accelerated. Consequently, liquid moves at the tip off axis. The spray consists of fast central region surrounded by a slower outer jet region. The outer jet region exhibits periodic droplet concentration fluctuations which are interpreted as a result of the periodic processes at the spray tip. Some high concentration regions in the outer jet region were investigated using a dark‐field holographic technique. This technique permits single droplet velocity measurements and local droplet concentration determination at extremely high droplet concentrations. The most important result of these investigations is that no correlation between the local droplet concentration and the droplet velocity could be

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130306

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe results of recent researches on twin‐fluid atomization are briefly reviewed, with particular emphasis on the effects of air and liquid properties on mean drop size. It is stressed that no single equation for the mean drop sizes produced in twin‐fluid atomization can satisfactorily correlate all the experimental data from any given atomizer. This is because for all types of atomizers the mechanism of liquid breakup changes from one basic mode to another with changes in atomizer operating conditions and/or liquid properties. These different modes of atomization exhibit different dependencies on atomizer dimensions and various physical properties such as liquid viscosity and air density. Equations for estimating the mean drop sizes produced in the various modes of twin‐fluid atomization are presented and disc

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130307

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractUltrasonic standing wave atomization (USWA) is a new process capable of atomizing both high surface energy liquids and highly viscous liquids. Atomization is achieved through acoustic forces acting upon a liquid jet which is guided into the central pressure node of a standing wave field. Spherical metal powders with minimum mass median diameters of less than 15 μm have been produced from metal melts with surface tensions of about 0.5 N/m. Organic liquids with viscosities between 1 and 10 Pas have been atomized, yielding mass median diameters from 20 to 330 μm. The influence of different operating parameters on the mass median diameter of metal melts and highly viscous liquids was evaluated. Parameters which were varied were ambient gas pressure, vibration amplitude of the transducers, mass flow rate, density of liquid, viscosity of the liquid, surface tension and the outlet diameter. The powders and sprays were analyzed with laser diffraction particle sizers. The physical background of the atomization process is discussed and an equation for the prediction of the mass median diameter is derive

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130308

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130309

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130301

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY