CFD Study of Fuel Combustion in a High Velocity Oxygen-Fuel Thermal Spray Gun

Thermal spraying by High-Velocity Oxygen-Fuel (HVOF)process is being used in an increasing variety of coating applications.In this study a computational fluid dynamics (CFD)model is developed to predict gas dynamic behavior in a high-velocity oxygen-fuel (HVOF)thermal spray gun in which premixed oxygen and propane are burnt in a combustion chamber linked to a parallel -sided nozzle.The CFD analysis is applied to investigate axisymmetric,steady-state,turbulent,compressible,chemically reacting,subsonic and supersonic flow within the gun.A segregated,finite volume numerical technique is used to solve the coupled conservation of mass,momentum,and energy equations for the gas in a sequential manner.A standard,two -equation,realizable k   turbulence model is employed for the turbulent flow field.An eddy dissipation model is used to solve the global reaction.This approach is based on the solution of transport equations for species mass fractions.The reaction rates are assumed to be controlled by the turbul ence instead of the calculation of Arrhenius chemical kinetics.Results describe the general gas dynamic features of HVOF spraying and then give a detailed discussion of the computational predictions of the present analysis.The gas velocity,temperature,pressure and Mach number distributions are presented for various locations inside the gun.The gas Mach number increases through the gun and reaches a maximum value of approximately 2.3 out of the nozzle exit.In addition,the results reported in this paper illustrate that the numerical simulation can be one of the most powerful and beneficial tools for the HVOF system design,optimization and performance analysis.

Keywords:

HVOF-CFD-gas dynamics-thermal spray-combustion