Numerical Investigation of In-Flight Behavior of Fe-Based Amorphous Alloy Particles in AC-HVAF Thermal Spray Process

Computational fluid dynamics is used to investigate the in-flight behavior of particles of Fe-based amorphous alloy powder in an activated combustion high-velocity air fuel spray process. The continuity, momentum, energy, and species equations are solved with a renormalization group k-epsilon turbulence model to predict the flow fields. A one-step chemistry model and eddy-dissipation model are used to simulate the combustion reaction. The processing of the Fe-based amorphous alloy particles in the gas flow is modeled based on the Lagrangian approach. The predictions show that the static pressure and flame temperature of the combustion products in the combustion chamber can reach up to 515,000 Pa and 1600 K, respectively, under the conditions considered in this study. Both the temperature and velocity of the alloy particles are strongly affected by the powder particle size. The particle injection position also has a great influence on the particle temperature. The greater the deviation of the injection point from the centerline, the higher the particle temperatures. The nitrogen flow rate and particle size were projected as two important parameters to avoid nozzle clogging, revealing that high gas flow rates and large particles favor expansion of the particle stream in the radial section during the spray process.