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Computational fluid dynamic modelling of gas flow characteristics in a high-velocity oxy-fuel thermal spray system

Computational fluid dynamic modelling of gas flow characteristics in a high-velocity oxy-fuel thermal spray system
Computational fluid dynamic modelling of gas flow characteristics in a high-velocity oxy-fuel thermal spray system
A computational fluid dynamics (CFD) model is developed to predict gas dynamic behavior in a high-velocity oxy-fuel (HVOF) thermal spray gun in which premixed oxygen and propylene are burnt in a 12 mm combustion chamber linked to a parallel-sided nozzle. The CFD analysis is applied to investigate axisymmetric, steady-state, turbulent, compressible, and chemically combusting flow both within the gun and in a free jet region between the gun and the substrate to be coated. The combustion of oxygen and propylene is modeled using a single-step, finite-rate chemistry model that also allows for dissociation of the reaction products. Results are presented to show the effect of (1) fuel-to-oxygen gas ratio and (2) total gas flow rate on the gas dynamic behavior. Along the centerline, the maximum temperature reached is insensitive to the gas ratio but depends on the total flow. However, the value attained (?2500 K) is significantly lower than the maximum temperature (?3200 K) of the annular flame in the combustion chamber. By contrast, the centerline gas velocity depends on both total flow and gas ratio, the highest axial gas velocity being attained with the higher flow and most fuel-rich mixture. The gas Mach number increases through the gun and reaches a maximum value of approximately 1.6 around 5 mm downstream from the nozzle exit. The numerical calculations also show that the residual oxygen level is principally dependent on the fuel-to-oxygen ratio and decreases by approximately fivefold as the ratio is varied from 90 to 69% of the stoichiometric requirement. The CFD model is also used to investigate the effect of changes in combustion chamber size and geometry on gas dynamics, and the results are compared with the nominal 12 mm chamber baseline calculations.
CFD, gas dynamics, HVOF, modeling
1059-9630
461-469
Gu, S.
bac1c02d-1867-47c3-81a7-0f25fc891a96
Eastwick, C.N.
08df7780-3254-4e4f-a6e6-dd5b4c89e913
Simmons, K.
a7bf7932-d262-4f2d-b019-5e87fde1a3c3
McCartney, G.
16a32ebd-652b-4f77-aec6-468a1cd77ddc
Gu, S.
bac1c02d-1867-47c3-81a7-0f25fc891a96
Eastwick, C.N.
08df7780-3254-4e4f-a6e6-dd5b4c89e913
Simmons, K.
a7bf7932-d262-4f2d-b019-5e87fde1a3c3
McCartney, G.
16a32ebd-652b-4f77-aec6-468a1cd77ddc

Gu, S., Eastwick, C.N., Simmons, K. and McCartney, G. (2001) Computational fluid dynamic modelling of gas flow characteristics in a high-velocity oxy-fuel thermal spray system. Journal of Thermal Spray Technology, 10 (3), 461-469.

Record type: Article

Abstract

A computational fluid dynamics (CFD) model is developed to predict gas dynamic behavior in a high-velocity oxy-fuel (HVOF) thermal spray gun in which premixed oxygen and propylene are burnt in a 12 mm combustion chamber linked to a parallel-sided nozzle. The CFD analysis is applied to investigate axisymmetric, steady-state, turbulent, compressible, and chemically combusting flow both within the gun and in a free jet region between the gun and the substrate to be coated. The combustion of oxygen and propylene is modeled using a single-step, finite-rate chemistry model that also allows for dissociation of the reaction products. Results are presented to show the effect of (1) fuel-to-oxygen gas ratio and (2) total gas flow rate on the gas dynamic behavior. Along the centerline, the maximum temperature reached is insensitive to the gas ratio but depends on the total flow. However, the value attained (?2500 K) is significantly lower than the maximum temperature (?3200 K) of the annular flame in the combustion chamber. By contrast, the centerline gas velocity depends on both total flow and gas ratio, the highest axial gas velocity being attained with the higher flow and most fuel-rich mixture. The gas Mach number increases through the gun and reaches a maximum value of approximately 1.6 around 5 mm downstream from the nozzle exit. The numerical calculations also show that the residual oxygen level is principally dependent on the fuel-to-oxygen ratio and decreases by approximately fivefold as the ratio is varied from 90 to 69% of the stoichiometric requirement. The CFD model is also used to investigate the effect of changes in combustion chamber size and geometry on gas dynamics, and the results are compared with the nominal 12 mm chamber baseline calculations.

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More information

Published date: September 2001
Keywords: CFD, gas dynamics, HVOF, modeling
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 47925
URI: http://eprints.soton.ac.uk/id/eprint/47925
ISSN: 1059-9630
PURE UUID: 7ea653ac-6782-4858-b6db-afd4073b66c3

Catalogue record

Date deposited: 01 Nov 2007
Last modified: 07 Jan 2022 22:30

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Contributors

Author: S. Gu
Author: C.N. Eastwick
Author: K. Simmons
Author: G. McCartney

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