Abstract
The flame spraying process has been analysed using three-dimensional Computational Fluid Dynamics (CFD) simulations. The process employed at the Volvo Aero Corporation for the coating of fan and compressor housings has been modelled. The gas combustion was simulated as a multi-component chemically reacting flow. The standard, two equations, k-ε turbulence model was employed. A statistical analysis of the computer simulation experiments revealed that particle velocity and particle temperature were dependent on four process parameters, namely the acetylene flow rate, the carrier gas flow, the powder feed rate and the spray distance. The most important factors influencing particle velocity and temperature were the acetylene flow rate and the carrier gas flow. The carrier gas flow rate was shown to have an unexpectedly large influence on particle in-flight properties. Simulations were repeated with particles of different median diameters. The study revealed that a very high correlation existed between particle temperature and particle velocity for particles of the same median diameter. Furthermore, the particle median diameter, when compared with the investigated process parameters, was found to have a more pronounced influence on both particle temperature and velocity. It would appear that the use of powder lots comprised of sufficiently fine-grained powders is the most promising single contribution towards increasing deposition efficiency that can be applied to the current process.
