Analysis of a high-velocity oxygen-fuel (HVOF) thermal spray torch. Part 2: Computational results

The fluid and particle dynamics of a high-velocity oxygen-fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The details of the CFD simulation are given in a companion paper. This paper describes the general gas dynamic features of HVOF spraying and then discusses in detail the computational predictions of the present analysis. The gas velocity, temperature, pressure, and Mach number distributions are presented for various locations inside and outside the torch. The two-dimensional numerical simulations show large variations in gas velocity and temperature both inside and outside the torch due to flow features such as mixing layers, shock waves, and expansion waves. Characteristics of the metal spray particle velocity, temperature, trajectory, and phase state (solid or liquid) are also presented and discussed. Particle velocities and temperatures are shown to be lower for this type of torch than previously believed.