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RESEARCH PAPERS: Suspensions and Soret Effect

Dense Particulate Flow in a Cold Gas Dynamic Spray System

[+] Author and Article Information
B. Samareh

Department of Mechanical and Industrial Engineering, Concordia University, Montreal, QC, H3G 1M8 Canada

A. Dolatabadi

Department of Mechanical and Industrial Engineering, Concordia University, Montreal, QC, H3G 1M8 Canadadolat@encs.concordia.ca

J. Fluids Eng 130(8), 081702 (Jul 30, 2008) (11 pages) doi:10.1115/1.2957914 History: Received May 29, 2007; Revised February 25, 2008; Published July 30, 2008

The effect of particle-gas and particle-particle interactions in a cold spray process is studied when the particle loading is high. To examine the effect of the presence of a dense particulate flow on the supersonic gas, an Eulerian-Eulerian approach is used. It is found that when the volume fraction of the injected particles is increased, the turbulence of the gas phase will be augmented by the motion of particles and consequently, the shape, the strength, and the location of the compression and expansion waves will be altered. Shock-particle interactions are demonstrated for various volume fractions. Another important parameter, which will affect the spraying deposition efficiency, is the substrate stand-off distance. It is found that the stagnation pressure alternates for different stand-off distances because of the formation of compression and expansion waves outside the nozzle exit. The particle normal velocity on impact is a strong function of the stagnation pressure on the substrate as particles must pierce through the bow shock formed on that region. The effect of the particle size and number density are also studied for different loading conditions. It is found that small and large particles behave differently as they pass through shock diamonds and the bow shock, i.e., in the case of very small particles, as the loading increases, the impact velocity increases, while, for the large particles, the trend is reversed.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of the cold spray process

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Figure 2

Pressure contours for two different grid resolutions of (a) 80×375 and (b) 120×800 at a loading of 0.1% (distances shown are from nozzle exit, cm)

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Figure 3

Grid dependency test for the two-phase analysis at a loading of 15% and mesh sizes of 80×375 and 120×800

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Figure 4

Schematic of the nozzle and substrate (Not to scale)

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Figure 5

Nozzle geometry and boundary conditions (not to scale)

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Figure 6

Contours of the flow field variables for the free-jet case without particle injection. (a) Mach number contours, (b) pressure contours (kPa), and (c) Temperature contours (K) (distances shown are from nozzle exit, cm).

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Figure 7

Pressure, temperature, and Mach number plots (distances shown are from nozzle exit, cm)

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Figure 8

Mach number contours for the free-jet case with 2μm particles injected at loadings of (a)=0, (b)=0.1%, (c)=1.0%, and (d)=15% (distances shown are from nozzle exit, cm)

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Figure 9

Axial volume fraction variations for 2μm particles injected at loadings of (a)=0.1%, (b)=1.0%, and (c)=15% (distances are from nozzle exit, cm)

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Figure 10

Pressure variations on a flat substrate for different stand-off distance from nozzle exit

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Figure 11

Pressure (kPa) contours for the case with a substrate located at 5cm from nozzle exit with particle loadings of (a)=0, (b)=0.1%, (c)=1.0%, and (d)=15% (distances are from nozzle exit, cm)

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Figure 12

Pressure distribution on centerline for the case with a substrate located at 5cm from nozzle exit and with different loadings

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Figure 13

2μm and 60μm particle axial velocities for the case with a substrate located at 5cm from the nozzle exit and with different loadings

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Figure 14

Particle impact velocity on a substrate at a stand-off distance of 5cm for various loadings

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Figure 15

Volume fractions of 2μm particles with different loadings at the nozzle exit

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