Measured and Simulated Particle Flow Field Characteristics in High Swirl, Supersonic Plasma Spray

摘要

High power, supersonic plasma guns operatingin the 100-200 kW range are a relatively new developmentin the thermal plasma spray coating process. Thesedevices produce molten particles with three to fourtimes the impact velocity of conventional plasma sprays.With this increased range of particle velocity it isimportant to understand the relationship betweensprayed particle size, velocity, temperature,trajectory, and spray pattern. Measurements of particlevelocity, temperature, and size along with spray patterncharacteristics have been obtained for a plasma spraysystem operating at 110 kW. The plasma and particle flowfields were also simulated with a pseudo 3-D model. Themodel assumes that the gas flow is axi-symmetric whilethe particles are treated in a fully 3-D manner. Theparticle behavior is modeled by a stochasticdiscrete-particle model which includes turbulentdispersion. Because the flow field has a high swirlnumber, it was found that the injection geometry playsa particularly important role in determining particletrajectory, heating, and acceleration. In spite of thecomplexity of the system, i.e., supersonic plasmavelocity with a high swirl component, the simulationproduced reasonably accurate mean velocities,temperatures, temperature, and size distributionsindicate that not all aspects are adequately modeled.