I. Two-phase flow in vertical and annular fluidized beds. II. Unsteady disturbances in axial compressors

Citation

Folsom, Blair Allen (1974) I. Two-phase flow in vertical and annular fluidized beds. II. Unsteady disturbances in axial compressors. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/SBE9-8D93. https://resolver.caltech.edu/CaltechETD:etd-10132005-133650

Abstract

Part I is a study of vertical and annular fluidized beds. The vertical fluidized bed was used to determine the responses of a total head probe and an electromagnetic probe to the average velocity through the bed. Both probes indicated velocities substantially higher than the calculated average fluid velocity for the suspension. The fluidized bed consisted of glass beads suspended in water flow and had an aspect ratio of 20. The average concentration distribution was measured over the height of the bed as well and was found to be constant within one tube diameter of the top and bottom of the bed.

The annular fluidized bed consisted of a suspension of small nylon spheres in a vortex-sink flow of water in a special annular chamber. The velocity distribution was deduced from pressure measurements in the flat side walls and the concentration distribution of particles was measured with a special optical meter. The drag coefficient of the particles and the wall shear stress were calculated from the measurements. At low concentrations the side wall boundary layers had a major effect on motion of the particles. At higher concentration the drag coefficient of the particles was found to have approximately the same value as for a vertical fluidized bed at the same concentration and Reynolds number. The wall shear stress coefficient was found to be of the same order of magnitude as for channel flow at the same Reynolds number.

Part II is an analytical study of unsteady disturbances in an axial compressor. The blade forces were represented as a continuous distribution of body forces acting on the fluid and the equations of motion were linearized. Only axial variations in the mean flow were considered and the disturbances were limited to planar pressure and entropy waves. A numerical integration gave results that depended on frequency and indicated that the largest velocity fluctuations inside the compressor always occurred at either the front or rear. Two related problems were also considered. Disturbances were superimposed on the flow through a duct with a restriction, similar to a blade row, and the reflected and transmitted waves were determined as functions of frequency. The response of turning vanes, treated as an actuator disc, to small disturbances was also determined.

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