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

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 24degrees 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 (a) of particles-to-jet air ranging from 3.5 x 10(-2) to 1.8 x 10(-1). Spherical particles with a mean diameter of d(p)= 130-200 mum and material density p(p) = 1050 kg/m(3) and nonspherical particles with a mean diameter of d(p)=200 mum and p(p)=1200 kg/m(3) were studied. The distribution of the 200-mum 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-mum. particles in the crossflow is generally greater with increasing downstream distance. However, dispersion of 130-mum 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. (C) 2002 Elsevier Science B.V. All rights reserved.