Modeling the gas flow and coating particles in the hydrogen fueled HVOF process

摘要

Careful process manipulation and adjustment in HVOF spraying is important to optimize the coating, and thus to achieve desired performance in various applications. Gas-particle interactions are commonly monitored by measuring the particle in-flight temperature and velocity. However, for process parameter adjustment, a more detailed understanding of the gas-particle interactions is needed, and for this computational modeling offers an interesting opportunity. Specifically, for a HVOF torch with hydrogen as the fuel gas, the effects of parameter manipulation on coating particle behavior are not well described in the literature. In this work, a computational model is built for the gas flow, and coating particles in-flight, in a HVOF process (Sulzer Metco Diamond Jet Hybrid 2600) that uses hydrogen as the fuel. The model is compared to experimentally obtained shock diamond profile, free jet temperature, and particle in-flight velocities and surface temperatures. The gas flow is solved without the presence of the coating particles. Turbulence is taken into account with realizable k-ε model, and the combustion is described as a single-step reaction according to an eddy-dissipation model. The computational fluid dynamics (CFD) calculations are conducted with OpenFOAM. Subsequently, the acceleration and heating of individual coating particles are modeled in a "snapshot" of the gas flow. The particle acceleration is governed by drag due to the gas, and the particle heating is determined by conduction and radiation between the particulate and the gas phases.