摘要:

AbstractAn Optical Particle Counter with optically defined measuring volume was investigated with regard to an application in the range of fine particles (f.i. water droplets less then 1.5 μm in diameter). Because of a problematic detection behaviour in the examined size range caused by the analogue signal processor, it was necessary to explore signals generated by the measurement system. In view of the results obtained an alternative signal evaluation method was developed on basis of a digital system. The high flexibility of software systems in signal processing rendered possible on the one hand a clear definition of the lower detection limit of the instrument. On the other hand it was possible to lower the detection limit and herewith the size of particles to be resolved. A practical application for the new evaluation technique is given by the measurement of fractional efficiency curves of technical separators and classifiers, which clearly shows the advantages of the system presented. Most recent investigations are concerned with the maximum number concentration detectable with the Optical Particle Counter, which could be increased up to five times

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060121

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractParticle Image Velocimetry (PIV) is a new technique which provides an instantaneous velocity profile of a flow field. A PIV system at Edinburgh University has been adapted to study the phenomenon of roping in a pneumatic particle conveyance rig. The principle features of this PIV system are as follows. Double images of the particles transported by the fluid are recorded on photographic film using a conventional camera. The displacement of the particle pairs, which determines the velocity at a particular point, is determined to an automatic analysis system. PIV is proving to be a powerful method in the investigation of roping. A rope is a high density ribbon of particles which is created when a uniform air‐coal flow segregates at a pipe bend into two regimes: one has a low coal to air ratio whereas the second regime, termed the rope, has a high coal to air ratio. This particular problem is connected with the pulverised fuel (pf) pipes of coal‐fired electricity generating stations. The flow, as seen on Figure 1, is reproduced in a 26 mm scale model encompassing the main aerodynamic features of pf pipes. The rope forms in the vertical to horizontal 90° bend, falls from the top to the bottom of the horizontal pipe and creats a dep

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060122

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060123

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe interaction of suspended particles with ultrasonic waves can lead to changes in the sonic velocity and also to extinction of the waves. An evaluation of the frequency dependence of ultrasonic extinction offers the most appropriate means of determining the concentration and size distribution of particles suspended in a fluid. With an experimental apparatus covering the frequency range from 1.7 to 81 MHz, particles ranging from about 20 to 1000 μm in diameter can be analysed. The measurements can be conducted with particle concentrations as high as 10% by volume

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060124

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA Light scattering technique is described which can discriminate, size and count airborne fibres down to 1.6 μm diameter. The results are compared with Mie theory for spheres and two models for finite cylinders based on the Rayleigh‐Gans‐Debye approximation and rigorous infinite cylinder theory modified by Fraunhofer diffraction on the le

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060125

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA comparative study of a few probability distributions generally used in describing various spray properties based on droplet size and velocity is described. Four different size distributions and three different coupled distributions, representing jointly size and velocity, are considered. A comparison of the results calculated for eight sets of data, taken from three different sources for the size distribution, and one data set for the joint size and velocity distribution, shows that the log‐hyperbolic function presents the best choice among both one‐ and two‐dimensional distributions.Considerations on one‐ and two‐dimensional probability distributions are followed by a description of the conservation laws and their use in the prediction of the loss of momentum and energy of doplets. Finally, a proposal is made for how the sprays should be studied experimentally and analysed theoretically in order to obtain the maximum possible information. A few suggestions are then provided for further research in this

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060126

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA concept of effective surface area was defined as a geometrical controlling factor for a chemical reaction involving powdery materials. It is not uniquely determined for the specific material but depends on the sort of chemical reaction as well as the state of agglomeration. Case studies were given for dissolution or decomposition reaction for MgO, Mg(OH)2and Pb(CO)3with and without preliminary mechanical activation and granulation. The effective surface area for dissolution is mostly the external surface of the agglomerates, although the internal surface plays a role to some extent, depending on the compactness of the agglomerates.

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060127

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe Leitz TAS‐Plus image analysis system was programmed to automatically measure both the ‘shape’ fractal and ‘fragmentation’ fractal for various types of fine particle filter cakes. The automated nature of the analysis facilitated the collection of statistically significant volumes of ‘fractal’ data. This data was then revised, where possible, to conventional theories of flow behavior. Several new insights evolved from the study as explained in the follo

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060128

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe spray properties of most practical importance, namely mean drop size, drop size distribution, radial and circumferential liquid distribution, cone angle and penetration, are discussed in the context of plain orifice, pressure‐swirl, plain‐jet airblast and prefilming airblast atomization. Equations are presented for estimating mean drop size and spray cone angle in terms of the relevant liquid properties, gas properties, atomizer dimensions, and atomizer operating conditions. The relative merits of these equations are discussed and compared. Some aspects of atomization in need of further research are indica

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060129

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060130

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY