Particle velocities, sizes and flux distribution in plasma spray with two powder injection ports

A two-port powder injection scheme applied to atmospheric plasma spray (APS) was investigated using a 2-D Phase Doppler Anemometer (PDA). The 8 wt.% yttria partially stabilized zirconia (YSZ) powders were sprayed from a Miller SG-100 arc plasma torch. Radial distributions of mean particle velocities, diameter and volume flux were measured and evaluated under different combinations of plasma and carrier gas flow rates. It was found that as a result of the interaction between the powder–gas flows from the two opposite injectors, both the mean particle velocity and mean diameter distribution were more symmetrical about the centerline of the plasma torch. The volume flux distributions evaluated using PDA measurements were also compared with the actual sprayed stationary deposit. Although there existed some obvious difference between the two cases, measurements using a PDA were able to approximately predict the variation of actual deposits under different conditions.