An investigation of geometrically induced swirl applied to lean phase pneumatic flows

Fokeer, Smeeta (2006) An investigation of geometrically induced swirl applied to lean phase pneumatic flows. PhD thesis, University of Nottingham.

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Abstract

This thesis provides unique insights into the application of a geometrically induced swirl by a three-lobed helix pipe on a lean phase of particulate suspension in air along a horizontal pipe section. A series of experimental and computational studies were applied to three flow conditions employing high speed photography, Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA), as well as Computational Fluid Dynamics (CFD) techniques. The CFD simulation predictions were validated both qualitatively and quantitatively against the experimental data and were then used to obtain further insights into the characteristics of the flow behaviour.

The LDA measurements of u, v and w velocities were shown to be in good agreement with the predicted CFD velocity components. Additional pressure loss caused by the swirl pipe was found to be proportional to the Reynolds number of the flow and increased further with an addition of particles to the swirling flow.

It was concluded that the swirl pipe imparts a wall jet type swirl to both an air-only flow and a lean pneumatic flow with velocity and momentum shifts from axial to tangential closer to the wall. The cusps and ridges of the twisted three lobe surfaces were shown to create a primary flow parallel to the flow axis, and secondary flows of a circulatory motion perpendicular to the primary flow. As a result, the trajectories followed by particles were observed to be affected by their size. The generated turbulence was shown to impart higher core axial velocity for both air and particles. The swirl was found to decay proportionally with the distance downstream of the swirl pipe and inversely to the flow's Reynolds number.

The major conclusions drawn from the study were that the swirl pipe locally increases the conveying velocity and produced an improved particle distribution across the downstream section of the pipe.

Item Type:Thesis (PhD)
Supervisors:Lowndes, I.S.
Kingman, S.
Uncontrolled Keywords:Pneumatic conveying, Laser Doppler Anemometry (LDA), Swirl, Turbulence, Computational Fluid Dynamics (CFD)
Faculties/Schools:UK Campuses > Faculty of Engineering > School of Chemical and Environmental Engineering
ID Code:256
Deposited By:Smeeta Fokeer
Deposited On:22 Oct 2007
Last Modified:06 Feb 2009 14:43

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