A Computational and Experimental Investigation into Radial Injection for Suspension High Velocity Oxy-Fuel (SHVOF) Therm
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A Computational and Experimental Investigation into Radial Injection for Suspension High Velocity Oxy-Fuel (SHVOF) Thermal Spray S. Chadha1 • R. Jefferson-Loveday1 • F. Venturi1 • T. Hussain1
Submitted: 4 April 2019 / in revised form: 25 June 2019 Ó The Author(s) 2019
Abstract Suspension high velocity oxy-fuel thermal spray typically utilizes axial injections of suspension into the combustion chamber. There are certain cases where the oxygen-sensitive nanoparticles benefit from a reduction in the time and temperature spent in the gas flow. Therefore, a radial injection outside of the nozzle can enable deposition of oxygen-sensitive nanomaterials. This study investigated the effect of the suspension flow rate, angle of injection and the injector diameter on the in-flight particle conditions. The combustion reaction is modeled using the eddy dissipation concept model with a robust reaction mechanism and compared to the current approach within the literature. This approach has not been employed within SHVOF thermal spray and provides a robust treatment of the reaction mechanisms. The suspension was modeled using a two-way coupled discrete particle model. Experimental observations were obtained using high-speed imaging, and observations of the liquid jet were compared to the numerical values. Keywords combustion modeling high-speed imaging HVSFS radial injection SHVOF supersonic crossflow suspension thermal spray List Cs Cn rAB
of Symbols Time scale constant = 0.4082 Volume fraction constant = 2.1377 Error introduced from the removal of species B onto Species A
& T. Hussain [email protected] 1
Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK
VA,i xi Y*i s* Y We dBi n*
Stoichiometric coefficient of species A in the ith reaction Reaction rate of the ith reaction Fine-scale mass fraction Reaction time scale Vapour mass fraction Weber number Delta function, value 1 if reaction contains species B Length fraction of fine scales
Subscript d Particle diameter g Gas l Liquid p Particle s Value at droplet surface Al2O3 Aluminium oxide
Introduction Surface engineering is a field of study that looks to alter the properties of substrate surface to increase its lifespan and durability and to reduce the surface degradation. One common approach in surface engineering is coating the surface of a substrate with a protective layer. Hence, the field of thermal spray arose to allow for the deposition of materials onto the surface of substrates to produce a protective coating. High velocity oxy-fuel (HVOF) thermal spray was developed in the 1980s to allow for the deposition of dense coatings to coat surfaces of a substrate in a protective coating. Suspension HVOF is a subset of HVOF thermal spray that allows for the deposition of nanoparticles using a suspension feedstock. Typically, in SHVOF thermal spray, premixed fuel and oxygen are injected into a
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J Therm Spray Tech
combustion chamber where the mixture undergoes combustion. The suspension is then injected
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