The influences of jet precession on near field particle distributions

Abstract

The effects of jet precession on the mean and fluctuating components of the distributions of 20 μm spherical particles in the first 10 nozzle diameters downstream from a simulated pulverised fuel burner have been investigated experimentally. Precessing jets are a class of oscillating flow with application in the combustion of pulverised fuels, especially in rotary kilns. The particle distributions have been determined using planar nephelometry, a laser-based instantaneous concentration technique. The influence of the momentum ratio of precessing jet to co-annular jet flow on the distribution of particles is assessed. Mean and fluctuating components of centreline particle distributions, half-widths and radial profiles are presented. It is found that small amounts of jet precession result in an elongation and narrowing of the overall particle distributions. Further increases of precessing jet momentum leads to a wider distribution of particles.