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a numerical investigation of free-fall swirling gas atomization process


a numerical investigation of free-fall swirling gas atomization process

haghighatjoo, mohammadreza (2020) a numerical investigation of free-fall swirling gas atomization process. Masters thesis, Concordia University.

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Gas atomization is a complex multi-physics route in the powder production field. Fine spherical metal powders can be produced using this technique via atomizing superheated molten metals. In the powder production industry, free-fall gas atomizer is often used for the melt atomization. The most significant advantage of using this type of atomizer is that it avoids melt build-up in the vicinity of gas and melt nozzle exits; the problem which is much more pronounced in the close-coupled gas atomizers. Obtaining smaller particle median diameter (d50) and narrower particle size distribution (PSD) have been the major manufacturing challenge. In the present work, a numerical parametric study is carried out on the atomization process variables of a novel layout of free-fall atomizer in order to reduce d50 and narrow down PSD. The used free-fall atomizer features a swirl motion of gas stream which allows the breakup point of the molten jet to be located at a closer distance to the die and benefits the most from the kinetic energy of the gas jets. A two-way coupled Eulerian-Lagrangian approach is utilized. Ideal gas law and k-epsilon turbulence model are employed to simulate the gas flow. In addition, the adaptive mesh refinement (AMR) technique is used to refine the computational domain locally and model the supersonic jet flow more accurately. The number of cells in the domain reaches around 40 million, and five to six shock diamonds are captured using this technique. To model the discrete (particulate) phase, the effects of Reynolds, Mach, and Knudsen numbers on the drag coefficient and Nusselt number on heat transfer are included. Moreover, Kelvin-Helmholtz Rayleigh-Taylor (KHRT) breakup model is used to simulate the molten metal atomization process. It is found that under the same operating condition, the increase in gas to melt ratio (GMR) and number of nozzles result in a smaller d50 and narrower PSD. This numerical analysis also investigates the effect of change in a range of radial and swirl angles. It is observed that increasing the radial angle and decreasing the swirl angle could narrow down the particle size distribution and reduce the particle median diameter.

Divisions:Concordia University > Gina Cody School of Engineering and Computer Science > Mechanical, Industrial and Aerospace Engineering
Item Type:Thesis (Masters)
Authors:haghighatjoo, mohammadreza
Institution:Concordia University
Degree Name:M.A. Sc.
Program:Mechanical Engineering
Date:November 2020
Thesis Supervisor(s):Dolatabadi, Ali
Keywords:Free-fall gas atomizer- Numerical simulation- Superheated molten metal powder- Supersonic compressible gas flow- Additive manufacturing- Discrete phase model
ID Code:987672
Deposited By: Mohammadreza Haghighatjoo
Deposited On:23 Jun 2021 16:32
Last Modified:01 Dec 2022 01:00


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