An experimental study on effects of fluid aerodynamics and particle size distribution in particle-laden jet flows
Abstract
The present study focused on performing experimental investigations of turbulent gas solid flows by means of laser Doppler velocimetry (LDV) and flow visualization. Glass bead particles with mean diameter of 25 and 70 microns were used in this study. The first goal of this dissertation was to investigate the effect of fluid aerodynamics on particle motion in the near field region of coaxial particle-laden jets. The fluid aerodynamics was modified by varying the inlet velocity ratio of the annular to central jet velocity at 0, 1.0, and 1.5. The solid loading of the particles was set at 0.5. Flow visualization showed that as the velocity ratio increased, the instantaneous spatial distribution of the particles became less symmetric with respect to the axial axis and wavier. LDV measurement indicated that the dispersion of particles was enhanced with decreasing particle size and with increasing the velocity ratio greater than 1.0. The present study also recognized the particle-phase radial velocity fluctuation as an important parameter to characterize the particle-turbulence interaction and the spatial distribution of particles in coaxial laden jets. The second goal of this dissertation was to explore the effect of particle size distribution (PSD) in a turbulent pipe flow with Re of 8,400. Binary mixtures of the 25 μm and 70 μm particles were investigated, and the PSD of the binary mixtures was varied by modifying the mass fraction of the fine particles, while the total solid loading was maintained at 1.0. LDV measurements showed that the addition of the fine particles enhanced the axial mean velocity of the coarse particles near the pipe center. In contrast, the motion of the fine particles was not influenced by the presence of the coarse particles. Based on this finding, it was hypothesized that the fine particles did not engage direct collision with the coarse particles, but the fine particles increased the resistance for the coarse particles to move as if the effective gas viscosity was increased. Moreover, the investigation of PSD effect was extended to a particle-laden jet flow. The radial spreading of the coarse particles was reduced by the presence of the fine particles.
Degree
Ph.D.
Advisors
Curtis, Purdue University.
Subject Area
Chemical engineering|Mechanical engineering
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