Abstract No.:
5298

 Scheduled at:
Thursday, June 08, 2017, Hall 28 4:20 PM
Cold Gas Spraying II


 Title:
Nozzle-internal particle velocity measurements and loading effect on particle acceleration inside a cold spray nozzle

 Authors:
Morten Meyer* / The University of Dublin, Ireland
Federico Caruso / Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Ireland
Rocco Lupoi/ Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Ireland

 Abstract:
The advantages of the solid state deposition process Cold Spray (CS) over conventional spray technologies go hand in hand with the requirement of high and well-predictable particle velocities. The acceleration of particles primarily takes place within the CS-nozzle while measurements of their velocity are conducted downstream of its exit. Despite their essential value, these observations are limited, in that only the result of the acceleration can be evaluated, not the actual driving mechanisms themselves. Previous work has indicated that there is no conclusive understanding of these mechanisms, especially in cases of increasing particle loading.
The present study therefore presents a transparent rectangular CS-nozzle design for a low stagnation pressure regime. A novelty to the field of thermal spray is the first report of particle in-flight measurements within the CS-nozzle using Particle Tracking Velocimetry (PTV) at varying particle loadings and pressure levels.
It is found that particle velocities decrease with increasing particulate loading as the momentum exchange of the gas is enhanced, particularly in the subsonic flow region. This effect is aggravated for higher working pressures, as energetic particle-particle and particle-wall collisions cause increasing losses, depending on the number density of particles. This study forms the basis for comprehensive nozzle-internal analysis.


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