Dynamic behavior of unsteady turbulent motion in pipe flows of dense gas-solid suspensions
Zhu, Chao
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Permalink
https://hdl.handle.net/2142/20031
Description
Title
Dynamic behavior of unsteady turbulent motion in pipe flows of dense gas-solid suspensions
Author(s)
Zhu, Chao
Issue Date
1991
Doctoral Committee Chair(s)
Soo, Shaolee
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Engineering, Mechanical
Language
eng
Abstract
Unsteady stratified motions in dense gas-solid suspension in horizontal pipe flows at low velocities have been observed, but the means for predicting these motions are lacking. For a dense suspension, the effects of particle-particle interaction, the damping of fluid motion by particles and the phase interactions between the dense phase and dilute phase have to be studied by relating both averaged and statistical properties of the phases. A complete set of instrumentation and methods were initiated and updated to quantify the nature of fluctuating motions in the dense suspensions.
Two improved recirculating test loops were capable of handling gas-particle suspensions continuously and indefinitely with particle-to-air mass flow ratios up to 12 in the 51 mm loop and 1.5 in the 127 mm loop. A newly developed photodiode array - collimated light source system, an improved isokinetic sampling system, and a venturi were used to measure bulk particle mass flow, particle mass flow distribution, and bulk air flowrate, respectively. A new technique called the corona charger method was introduced and used to determine instantaneous velocities of both gas and particle phases. The fluctuations of particle mass flows and densities were measured by an advanced ball probe system and an improved laser-Photomultiplier system. An important equality relating averages and fluctuations of mass flow, velocity and density of particle phase was derived and used to determine the particle intensity. Fluctuations in mass flow and density of particle phase were correlated in terms of frequency spectrums and integral time scales. The transport properties of dense suspensions were also calculated. Models for the wave motion in a stratified two-phase flow, for the leakage flow and averaged particle volume fraction in a standpipe, and for the determination of the coefficient of particle viscosity in a dense suspension were developed.
Using glass particles of 100 $\mu$m, 200 $\mu$m, and 450 $\mu$m, air-solid suspensions with bulk mass flow ratios of 3, 6, 9, and 12 at bulk air velocities of 8, 10, and 15 m/s were investigated. The results showed a consistency of the measurements using various independent instrumentation and methods.
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