摘要:

AbstractA method called “image‐sedimentation”, based on the application of Stokes' law to suspension and image techniques, is proposed for the rapid analysis of particle size distributions. A parallel beam of optical light, after passing through a cell containing particles, is measured with a linear image sensor with 2048 photodetectors to determine the attenuated light intensity displayed on a monitor screen. The settling height between any given point and the liquid surface can be measured accurately by use of this image technique without any additional mechanical device to move either the light beam or the glass cell containing the suspension. Consequently, the total time required for the determination of the particle size distribution, typically of a carborundum powder having a median diameter of 5 μm, takes only 5 min as compared with more than 20 min by using other instruments based on the sedimentation pri

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140602

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractTwo descriptors based on mathematical morphology are described which permit discrimination between convex and concave polygonal shapes which often characterize crystalline particles. Their computation is based on the comparison between the silhouette of the particle and a reference shape. Three reference shapes are discussed: the convex hull, the circle circumscribed to the particle and the equivalent circle.

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140603

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractIn previous work, the relative performance of various methods used to characterize the particle size distribution of powders composed of fine irregularly shaped particles was assessed. It was found that methods employing Fraunhofer diffraction theory were inferior with respect to particle counting methods. Furthermore, calculated particle size distributions varied considerably between manufactures of Fraunhofer devices. It is well known that the Mie optical model can also be used to analyze the data collected by laser diffraction instruments. Here, we have compared particle size distributions collected using two Laser diffraction instruments to those determined by the Aerosizer. In our earlier work the Aerosizer was shown to produce results nearly identical to those determined by image analysis. The results of this study indicate that the use of the Mie optical model does not correct for deficiencies previously noted for laser diffraction methods. Considerable variation exists between the results obtained on laser diffraction instruments manufactured by different companies. Our earlier recommendation to use extreme caution when employing laser diffraction instruments to characterize fine powders continues to be supported in the present work.

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140604

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe influence of the surface roughness of solid conducting spheres on the response of a phase‐Doppler anemometer (PDA) is described by using a ray theory model. A rough particle surface is modeled as an ensemble of distorted spheres. First‐ and second‐order reflection and diffraction are considered for far‐field calculations of the PDA phase difference. The numerical simulations are accompanied and supported by experimental results. Single roughSnspheres are captured inside an electro‐dynamic trap and investigated with a standard phase‐Dop

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140605

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA compact and commercial aerosol generator capable of generating narrowly size‐distributed aerosols with high mass concentrations was designed, fabricated and tested. The aerosol generator, consisting of a Delavan simplex nozzle (Model 30610‐4), an L‐shaped settling chamber and a virtual impactor with a clean air core, was modified and improved fromCheinandLundgren's work [20] to be more compact and readily commercial. The performance of the aerosol generator was evaluated using corn‐oil, sodium chloride and uranine solutions. The results indicated that the cornoil droplets produced by the generator had a mass medium aerodynamic diameter (MMAD) of 7.20 ± 0.32 μm with a geometric standard deviation (GSD) of 1.48 ± 0.01 and the aerosol generation rate was 13.8 ± 1.3 mg/min. Solid aerosols generated from NaCl solution were found to have an MMAD in the range 1.39–4.88 μm with a GSD of 1.34–1.47 with the volumetric solution concentration varying from 0.1% to 9%. At the same time, the aerosol generation rate varied from 0.27 ± 0.05 to 15.8 ± 1.8 mg/min. depending on the solution concentration and the particle size produced. In addition, a 0.01% uraniane solution was tested to generate a submicron aerosol with an MMAD of 0.93 μ

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140606

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA new method is introduced to analyze the accuracy of phase‐Doppler anemometry (PDA) for sizing large particles in two‐phase flows. The method is based on Fourier optics theory (FOT) and geometrical optics theory (GOT) to calculate the intensity ratio of refractive and reflective light scattered by a sphere under a slit constraint. To examine the accuracy in calculating the light intensity, the results from the GOT method were compared with those of the direct simulation based on the generalized Lorenz‐Mie theory (GLMT). This newly developed FOT/GOT method also predicts the results of phase jump due to the slit constraint. The performance of dual‐mode phase‐Doppler anemometry can also be simulated by th

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140607

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140608

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140609

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19970140601

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY