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Powder particles flow blockage and sub- poly Behavior

Author: HuangShiCheng
Tutor: OuYangHongWu
School: Central South University
Course: Powder Materials Science and Engineering
Keywords: Powder Flow Block Of poly
CLC: TB383.3
Type: Master's thesis
Year: 2009
Downloads: 100
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Abstract

Powder (particulate matter) is different from the solids, liquids and gases for a class of soft matter, is a complex fluid, the need for new theories and methods of its research and awareness. Yield powder flow behavior blocking and sub polyethylene powder metallurgy process of unloading, mixing and loading, and other key processes are closely related, directly affects the production of powder metallurgy process and results. Therefore, the basic physical properties of powders and characterization of a very important scientific value and engineering significance. In order to ascertain powder particle flow and congestion characteristics of poly mechanism and its influencing factors, this paper systematically studied several different shapes and sizes of dry / wet drum particulate matter at low flow through the bottleneck below the critical size The critical blockage changes and Bipropellant particles flowing in stacking ramp means spontaneous behavior of poly. The results showed that: 1. Powder state correlation with the physical properties, characterized by the powder flowability properties reflect not only the particle also reflect the state of motion. Shear deformation rate of particles of the particulate material reflects the shear capacity of the state or maintain flow. Based on the particles under low speed drum surface linear velocity distribution characteristics of the drum by measuring the low thickness of the free surface of the powder flowing h, the proposed time of the shear deformation of the particles Tγ = 1 / {ω [(R / h) 2-1]} (where ω is speed, R the drum radius) Characterization Powder flowability as a new method not only reflects the state of particle flow characteristics (mobility with the flow state is changed), but also General properties of the particles (such as particle size and shape) of. The method is simple and reliable, its characterization results under certain speed with the use of flow cytometry to the Hall showed good consistency. Adding a small amount of liquid, increasing the adhesive force between the powder particles, the wet particle shearing motion inside the evolution of clusters dramatically changed mobility of particulate matter. (2) particle size below the critical bottleneck through the blockage and particle motion patterns are closely related. Particle flow through the bottleneck found showing four different movement patterns (jet, inclined stream, jumping stream and spiral flow), the speed of movement patterns between different mutual interference (arching) is the formation of clogging and a \mechanisms; clogged bottleneck before the outflow probability distribution of the number of particles unimodal distribution function: With the particle flow is reduced (surface friction coefficient increases) and the density increases, the probability distribution of peak reduction and the right, and the average size of the collapse (outflow the number of particles) increased. 3 Bipropellant powder particles in the drum and stacked inclined low flow behavior occurs not only depending upon the group of polyethylene per degree of difference between the physical properties of particles, the particles but also the pouring flow rate Q (equivalent to the drum The rotational speed ω) and the added amount of liquid W (volume ratio) are closely related. When the flow rate Q or liquid dosage W reaches a critical value, the behavior of poly will disappear. For example, the pouring of the mixed particle diameter ratio of 3:1 sand particles, Q up 31.25ml / s or W reaches 0.7%, of polyethylene will disappear. Therefore, reducing particulate matter Bipropellant difference, increasing the flow rate or liquid dosage will help prevent the emergence of poly behavior. Comprehensive analysis of the above factors and sub-particles clogging behavior of poly (such as model and phase diagram creation and theoretical analysis) remains to be intensified.

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