|M.Sc Student||Ben-Shmuel Yaron|
|Subject||Modelling and Calculation of Fluid Flow and Fractional|
Efficiency of a Tangential Flow Cyclone
|Department||Department of Mechanical Engineering||Supervisor||Professor Emeritus Michael Shapiro|
|Full Thesis text|
The Cyclone separator is a two-phase device for separation of particles dispersed in the carrier fluid flow. It is now commonly employed in industry for the removal of dust particles from gases and liquids. The advantages of cyclones are in their simplicity and low costs in terms of construction, operation and energy consumption. However the cyclones are efficient in removal of relatively large particles, namely with diameters exceeding 2-5mm. Improvement of cyclone operation may be achieved by its rational design based on the adequate modeling of the flow field and particle transport within these devices. This research is aimed at development of computational model of the flow velocity field and particle motion within the tangential flow cyclones.
The turbulent gas flow field in several cyclone separators is computed employing Reynolds Stress Model (RSM) and using the FLUENT 6.1 commercial solver. A special effort is made to appropriately define the flow region and construct the adequate mesh able to capture the flow peculiarities. Towards this goal a special interface mesh/geometry builder is developed using GAMBIT pre-processor. As a result the pressure drop across the cyclone is calculated and compared with the available experimental data. The deviation of pressure drop predictions for Stairmand tangential cyclones with the inlet flow Reynolds number of 105 is less than 4%. Basing on the computed flow field, separation efficiencies of 0.3 - 3.5 mm quartz powder particles in the cyclones designed by Gottschalk and Bohnet  are calculated.
The calculation results establish the relative merits and predictive capacities of several computational models as tools for rational hydraulic cyclone design. We also investigated the effects of cyclone design parameters, boundary conditions and particle physical properties on the fractional efficiency. The computed fractional efficiency agrees with the experimental data collected for 1- 3.5 mm particles within 25%. Further steps in improving the particle capture model in cyclones are contemplated in order to improve the agreement especially for submicron particles, where the model still significantly overpredicts the experimental capture efficiency.