An experimental investigation of particle size distribution effects in dilute -phase gas -solid flow

A particle-laden flow has been investigated with laser-Doppler velocimetry (LDV) for both monodispersed and binary mixtures of glass beads. Although a large body of work exists for gas-solid flows over a range of particle sizes in the literature, few of the previous experimental data sets have covered the range of solids loadings investigated in this work. Significant effects of particle size distribution (PSD) have been previously demonstrated in the literature; however, the total number of data sets and the range of conditions that have been explored are minimal. Gas-solid flow models employing kinetic theory in order to describe the random motion of the solids have also been developed and have enjoyed success in prediction of both gas and solid-phase velocities for particles with diameters of 200 microns and greater. The goals of this dissertation have been to explore the effects of solids loading on the motion of particles in both monodispersed and binary mixtures for a range of particle sizes and loadings, which are industrially relevant, and to assess the validity of current gas-solid flow models using kinetic theory on these data. Particle clustering is observed for dense conditions with monodispersed mixtures of 70-micron particles, and increases in the solids loading led to increases in the particle fluctuating velocity. The models of Bolio et al. (1995) and Hrenya and Sinclair (1997) are able to qualitatively predict these trends resulting from increased solids loading. Binary mixtures of 25 and 70-micron particles show that the gas-phase turbulence intensity is decreased when the mass fraction of the finer solids is increased in the mixture. This result agrees with predictions of the gas-solid flow model for a bimodal PSD developed by Agarwal and Sinclair (1997). The effect of varying the mass fraction of particles in binary mixtures of coarser solids with diameters as large as 500 microns was also investigated. Decreasing the mass fraction of finer solids in these mixtures lead to increases in the fluctuating velocities of both particle phases due to the decreased occurrence of inelastic particle collisions when the overall particle number density in the mixture is reduced