الفهرس 
Classification of DiffusersOnly 14 pages are availabe for public view
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Abstract
Diffusers are very important devices used to convert kinetic energy into
pressure energy. Diffusers are subjected to many applications such as fluid machines,
aircraft intakes, combustion chambers, etc. The pressure rise through the diffuser is a
measure of its performance, therefore there is a need to understand the diffusion
phenomena within the diffuser. There are different parameters concerning diffuser
design (geometric) and working (dynamic) that affect the performance of such parts.
Also, there are parameters concerning the application in which the diffuser will be
used. Some of these parameters are those concerning solid-phase in a gas-solid twophase
flow through diffusers which will be the goal of the present study.
In this thesis, numerical and experimental studies have been carried out to
investigate gas-solid flow in a vertical straight-walled diffuser. In the numerical study,
Eulerian-Lagrangian approach is used to simulate the two phases. The continuous
phase (gas) is simulated using Eulerian frame by solving Reynolds-Averaged Navier-
Stokes equations (RANS), while the dispersed phase (solid) is simulated using particle
tracking method by solving particle equations using 4th order Runge-Kutta method.
The pressure-velocity coupling is achieved using SIMPLE algorithm. Coupling
between the two phases is established by adding particle source terms and void
fraction in calculation of the continuous phase taking into account the effect of
particle-particle collisions (i.e. 4-way coupling). The lift forces, particle dispersion and
particle-wall collisions are also considered in the simulation of solid-phase. To
evaluate and choose the suitable turbulence model, three turbulence models namely
standard k-ε model, standard Chen-Kim model and suggested-coefficient Chen-Kim
model are examined. The experimental study is carried out on a pilot scale vertical
pneumatic transport system. Four different geometries of diffuser are tested at various
inlet Reynolds numbers and different mass loading ratios. Sand particles of different
sizes and mass flow rates are used to represent the solid phase. Measurements of static
pressure distributions along the test section are performed.