Dispersion of a particle-laden air jet in a confined rectangular crossflow

Abstract

Dispersion of a particle-laden air jet issuing into a confined rectangular crossflow has been studied experimentally by means of a planar light-scattering technique. Experiments were run for a jet injected at 24° to the crossflow, using three jet-to-crossflow velocity ratios ( V r=0.5, 1.0 and 1.5), five downstream measurement locations ( x/ D=7.5, 12, 16, 20, 25) and mass fractions ( σ) of particles-to-jet air ranging from 3.5×10 −2 to 1.8×10 −1. Spherical particles with a mean diameter of d p=130–200 μm and material density ρ p=1050 kg/m 3 and nonspherical particles with a mean diameter of d p=200 μm and ρ p=1200 kg/m 3 were studied. The distribution of the 200-μm spherical particles downstream of the jet-crossflow intersection is more uniform than that of nonspherical particles, indicating that particle shape affects dispersion. The dispersion of both types of 200-μm particles in the crossflow is generally greater with increasing downstream distance. However, dispersion of 130-μm spherical particles becomes non-uniform with increasing downstream distance due to the action of a large-scale counter-rotating vortex pair. Dispersion of the particle-laden air jet in the crossflow is not greatly dependent on loading rate over the range of loadings studied. For both spherical and nonspherical particles, the penetration of particle-laden air jet issuing into the crossflow is greater than that of a single-phase air jet. Measurements of static pressure along the top of the main duct (crossflow) indicate that the effect of particles on the air-phase static pressure downstream of the jet-crossflow intersection is significant only for the higher particle loading rates.