A Novel Numerical and Experimental Investigation into Radial Injection for Suspension High Velocity Oxy Fuel (SHVOF) Thermal Spray

摘要

Suspension High Velocity Oxy Fuel (SHVOF) thermal spray typically utilises axial injections of suspension into the combustion chamber. Deposition of oxygen sensitive materials such as graphene have faced difficulty whilst injecting axially as the particles degrade with an extended exposure to oxygen at high temperatures. A radial injection outside of the nozzle reduces inflight particle time and hence can enable deposition of oxygen sensitive nano-materials. The aim of this study is to investigate how the injection parameters affect the inflight particle conditions. This study investigates how the suspension flow rate and the angle of suspension injection effects the inflight particle conditions. Due to the extensive previous work, alumina has been chosen as an exemplar for this work. This study employs an alternative combustion model to that currently employed within the literature, eddy dissipation concept model. This model does not suffer from the over prediction in the adiabatic flame temperature within the combustion chamber as experienced by the eddy dissipation model. The suspension is modelled using a two-way coupled DPM model with a multicomponent injection to model the suspension. Experimental observations are obtained using high speed imaging and the experimental observations of the liquid jet are compared to the numerical values. This study shows the importance of optimizing the suspension injection parameters and the injector design, as this can greatly affect the inflight particle conditions and therefore improve the quality of the coating deposition. An increase of above 30 % for the inflight particle characteristics can be obtained when optimising the suspension flow rate and the angle of injection.