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Numerical investigations of thermal spray coating processes: combustion, supersonic flow, droplet injection, and substrate impingement phenomena

Numerical investigations of thermal spray coating processes: combustion, supersonic flow, droplet injection, and substrate impingement phenomena
Numerical investigations of thermal spray coating processes: combustion, supersonic flow, droplet injection, and substrate impingement phenomena
The aim of this thesis is to apply CFD methods to investigate the system characteristics of high speed thermal spray coating processes in order facilitate technological development. Supersonic flow phenomena, combustion, discrete droplet and particle migration with heating, phase change and disintegration, and particle impingement phenomena at the substrate are studied. Each published set of results provide an individual understanding of the underlying physics which control different aspects of thermal spray systems.

A wide range of parametric studies have been carried out for HVOF, warm spray, and cold spay systems in order to build a better understanding of process design requirements. These parameters include: nozzle cross-section shape, particle size, processing gas type, nozzle throat diameter, and combustion chamber size. Detailed descriptions of the gas phase characteristics through liquid fuelled HVOF, warm spray, and cold spray systems are built and the interrelations between the gas and powder particle phases are discussed. A further study looks in detail at the disintegration of discrete phase water droplets, providing a new insight to the mechanisms which control droplet disintegration, and serves as a fundamental reference for future developments of liquid feedstock devices.

In parallel with these gas-particle-droplet simulations, the impingement of molten and semi-molten powder droplets at the substrate is investigated and the models applied simulate the impingement, spreading and solidification. The results obtained shed light on the break-up phenomena on impact and describe in detail how the solidification process varies with an increasing impact velocity. The results obtained also visually describe the freezing induced break-up phenomenon at the splat periphery.
Tabbara, Hani
005dd3f8-eeb2-4698-ad5d-3dbd699084a7
Tabbara, Hani
005dd3f8-eeb2-4698-ad5d-3dbd699084a7
GU, SAI
a6f7af91-4731-46fe-ac4d-3081890ab704

(2012) Numerical investigations of thermal spray coating processes: combustion, supersonic flow, droplet injection, and substrate impingement phenomena. University of Southampton, Faculty of Engineering and the Environment, Doctoral Thesis, 182pp.

Record type: Thesis (Doctoral)

Abstract

The aim of this thesis is to apply CFD methods to investigate the system characteristics of high speed thermal spray coating processes in order facilitate technological development. Supersonic flow phenomena, combustion, discrete droplet and particle migration with heating, phase change and disintegration, and particle impingement phenomena at the substrate are studied. Each published set of results provide an individual understanding of the underlying physics which control different aspects of thermal spray systems.

A wide range of parametric studies have been carried out for HVOF, warm spray, and cold spay systems in order to build a better understanding of process design requirements. These parameters include: nozzle cross-section shape, particle size, processing gas type, nozzle throat diameter, and combustion chamber size. Detailed descriptions of the gas phase characteristics through liquid fuelled HVOF, warm spray, and cold spray systems are built and the interrelations between the gas and powder particle phases are discussed. A further study looks in detail at the disintegration of discrete phase water droplets, providing a new insight to the mechanisms which control droplet disintegration, and serves as a fundamental reference for future developments of liquid feedstock devices.

In parallel with these gas-particle-droplet simulations, the impingement of molten and semi-molten powder droplets at the substrate is investigated and the models applied simulate the impingement, spreading and solidification. The results obtained shed light on the break-up phenomena on impact and describe in detail how the solidification process varies with an increasing impact velocity. The results obtained also visually describe the freezing induced break-up phenomenon at the splat periphery.

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Published date: June 2012
Organisations: University of Southampton, Engineering Science Unit

Identifiers

Local EPrints ID: 348993
URI: http://eprints.soton.ac.uk/id/eprint/348993
PURE UUID: 6ceb4cca-3b96-47f6-8b00-20a655913a91

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Date deposited: 06 Mar 2013 14:31
Last modified: 18 Jul 2017 04:45

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Contributors

Author: Hani Tabbara
Thesis advisor: SAI GU

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