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Research Papers

Modeling of Ceramic Particle Heating and Melting in a Microwave Plasma

[+] Author and Article Information
Kaushik Saha, Swetaprovo Chaudhuri

Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269-3139

Baki M. Cetegen1

Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269-3139cetegen@engr.uconn.edu

1

Corresponding author.

J. Heat Transfer 133(3), 031002 (Nov 15, 2010) (10 pages) doi:10.1115/1.4002448 History: Received June 17, 2009; Revised November 05, 2009; Published November 15, 2010; Online November 15, 2010

A comprehensive model based on finite volume method was developed to analyze the heat-up and the melting of ceramic particles injected into a microwave excited laminar air plasma flow field. Plasma flow field was simulated as a hot gas flow generated by volumetric heat addition in the microwave coupling region, resulting in a temperature of 6000 K. Alumina and zirconia particles of different diameters were injected into the axisymmetric laminar plasma flow at different injection velocities and locations. Additionally, noncontinuum effects, variation of transport properties of plasma surrounding the spherical particles and absorption of microwave radiation in the ceramic particles were considered in the model. Model predictions suggest that zirconia and alumina particles with diameters less than 50μm can be effectively melted in a microwave plasma and can produce more uniform melt states. Microwave plasma environment with the ability to inject particles into the plasma core provide the opportunity to create more uniform melt states as compared with dc arc plasmas that are influenced by characteristic arc root fluctuations and turbulent dispersions.

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Figures

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Figure 9

Surface and center temperatures of the particles injected along the centerline with an initial velocity of 45 m/s. Time: (a) zirconia: 30 μm–1.96 ms, 50 μm–2.55 ms, and 60 μm–5 ms and (b) alumina: 30 μm–2.02 ms, 50 μm–2.7 ms, and 60 μm–3.7 ms.

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Figure 10

Melt front movement of a 50 μm alumina injected along the centerline with an initial velocity of 45 m/s: (a) zirconia: a−t=2.55 ms, X=0.112 m, b−t=2.70 ms, X=0.119 m, c−t=2.77 ms, X=0.123 m, d−t=2.85 ms, X=0.126 m, and e−t=2.92 ms, X=0.130 m and (b) alumina: a−t=2.7 ms, X=0.119 m, b−t=2.77 ms, X=0.124 m, c−t=2.81 ms, X=0.125 m, d−t=2.84 ms, X=0.127 m, and e−t=2.88 ms, X=0.129 m

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Figure 2

Evolution of temperature and axial velocity distributions at three axial locations

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Figure 3

Variations of plasma temperature along the centerline and the temperature of the outer surface of the quartz wall along the axial direction

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Figure 4

Model validation with Bourdin (12) for a stationary 100 μm alumina particle in a nitrogen plasma bath at 10,000 K

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Figure 5

Effect of noncontinuum on heat-up of 10 μm and 30 μm zirconia particles up to melting point injected with a velocity of 45 m/s along the centerline

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Figure 6

Comparison of convective and radiative fluxes experienced by a 30 μm zirconia particle up to melting point injected along the centerline with an initial velocity of 45 m/s

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Figure 7

Temperature profiles of 30 μm (a) zirconia and (b) alumina particles injected along the centerline with different initial velocities from the particle injection tube at the instant when surface temperature reaches melting point

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Figure 8

Effect of injection locations in heat-up of 30 μm (a) zirconia and (b) alumina particles with an initial velocity of 45 m/s from the particle injection tube

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Figure 1

Schematic of the experimental setup of the microwave plasma torch

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