Journal of the Society of Powder Technology, Japan
Online ISSN : 1883-7239
Print ISSN : 0386-6157
ISSN-L : 0386-6157
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Volume 28, Issue 10
Displaying 1-5 of 5 articles from this issue
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  • Influences of Bed Porosity on the Impact Efficiency of Air-borne Fine Particles to a Bed Particle
    Kenichi USHIKI, Shinichi YUU, Shigeki TANAKA, Wataru EGUCHI
    1991 Volume 28 Issue 10 Pages 612-618
    Published: October 10, 1991
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.28.612
    JOURNAL FREE ACCESS
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    The impact efficiency of air-borne fine particles on a bed particle has been studied, extending over wide range of the bed porosities. The conventional cell model seems to be effective in predicting the impact efficiency only when the bed porosity is high enough. Two bed structure models besides the conventional cell model were introduced and tested in this paper. A modified cell model in which fine particles enter a cell from a narrow area and at an accelerated velocity is useful when the bed porosity is more than 0.8. An impactor model which considers a bed as a round nozzle cascade impactor with a small aspect ratio was found to be effective when the bed porosity is less than 0.8.
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  • An Examination of the Separation of Differently Shaped Particles Based on Grindability
    Yoshiteru KANDA, Kaname ENOMOTO
    1991 Volume 28 Issue 10 Pages 619-623
    Published: October 10, 1991
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.28.619
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    The particle shape affects the grindability of powdered or granular materials. In order to examine the possibility of the separation of differently shaped particles by comminution, the compressive crushing of powder beds was performed. The sample used was 3.5×4 mesh quartz. The diameter of a circumcircle, N, and the thickness, T, of the sieved particles were measured, and the shape index defined by (N/T) was calculated. The relationships between the energy input in a powder bed and the mean shape index of unfractured particles was studied.
    The results were summarized as follows:
    (1) The mean shape index of unfractured particles decreased with increase in the energy input when the probability of crushing was less than 0.5.
    (2) It was found that a comminution was applicable to the shape separation of granular materials having differently shared particles.
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  • Air Flow and Pressure Loss in a Centrifugal Air Classifier
    Mitsuhiro ITO
    1991 Volume 28 Issue 10 Pages 624-631
    Published: October 10, 1991
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.28.624
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    Air velocity distribution and pressure loss in a centrifugal air classifier were investigated. First, theoretical equations for air velocity and pressure difference were derived from the Navier-Stokes equation, and these were compared with observed data. Although a fair agreement between the observed and calculated values was obtained in air velocity, a great difference was found in pressure difference. A reason for the later was the dissipation energy Ev of vortex air with high speed. Also, 0.05-0.1m2/s of eddy diffusivity for momentum was observed.
    A simple method for estimating Ev was experimentaly found to follow the form:
    Ev=0.44|ΔU|2 where ΔU is the air velocity difference at the classifier.
    When a powder was induced into the classifier, additional pressure loss by powder was not affected by the feed rate of the powder and was kept at a constant value depending on the properties of powder, such as powder density and particle size, and on the conditions of the classifier, such as rotor speed and airflow rate.
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  • The Experimental Stress-Strain Rate Relationsship of Granular Materials
    Shinichi YUU, Shigenori KAMIMURA
    1991 Volume 28 Issue 10 Pages 632-637
    Published: October 10, 1991
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.28.632
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    The flow of granular materials is important in the field of material handling. However, there are many unknown factors in analyzing these flows. Constitutive relations (stress and strain rate relations) are needed to describe the flow dyna macs of granular materials. We experimentally obtained the constitutive relations of granular materials by using a chute-type shear apparatus. The chute in which the granular material is contained and covered by a top board, can be moved on straight rails, while the top board is loaded vertically and is fixed at rest. The shear stresses, normal stresses and strain rates which were measured by using the chute type shear apparatus give the constitutive relations of the granular materials. The experimental results describe well the flow characteristics (e. g. the stress ratio of shear to normal stresses is proportional to the strain rate, etc.) under the condition in which the friction forces between granular materials dominate.
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  • Asbestos Used Form and Emvironmental Problem
    Kunihiko ASAKUNO
    1991 Volume 28 Issue 10 Pages 638-643
    Published: October 10, 1991
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.28.638
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