Measurement of Continuous Phase Velocities in a Confined Solid-Liquid Jet Using LDV

Artikel i vetenskaplig tidskrift, 2014

A two-component LDV was used to investigate how flow structures in a liquid jet are influenced by the presence of solid particles. Solid glass spheres with a density of 2.5 kg/dm(3) and three different sizes (0.5 mm, 1 mm, and 2mm) at different solids loading (0-6.2 vol.%) were used as particles, while water served as continuous phase. No significant influence of the solid particles on the rate of decrease in the centerline liquid velocity or the jet expansion ratio could be observed. Two flow regimes were identified: a stable jet characterized by a symmetric shear layer close to the nozzle, and a flow dominated by large-scale instabilities farther from the nozzle. The spreading of particles was dominated by interparticle collisions in the region close to the nozzle and by jet instability in the region farther from the nozzle. With increased solids loading increased liquid RMS values in the region close to the nozzle could be found. The effect on RMS values was larger with larger particles. For the 1mm particles the RMS increased in this region, but decreased in the region farther from the nozzle. The presence of 2mm particles acted to stabilize the jet, and the instability moved farther downstream. Suspensions with smaller particles had no effect on the instability, strength, or location.