462748 Investigation of Continuum Two-Fluid Models in Simulating Fluidised Beds in Openfoam

Thursday, November 17, 2016: 1:46 PM
Golden Gate (Hotel Nikko San Francisco)
Corey Downie1, Kokou Dadzie1, Raffaella Ocone2, Jason Reese3, Jiamin Ye4 and Haigang Wang5, (1)Heriot-Watt University, Edinburgh, United Kingdom, (2)Chemical Engineering, Heriot-Watt University, Edinburgh, United Kingdom, (3)University of Edinburgh, Edinburgh, United Kingdom, (4)Institute of Engineering Thermophysics,Chinese Academy of Sciences, Beijing, China, (5)Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing, China

There is no single continuum based method that can simulate a range of rapid granular flow types in a single simulation. In this work we present modifications to an existing two-fluid model in OpenFOAM that allow for both compressible and incompressible flows to be simulated using a single model. A non-equilibrium multiphase compressible flow can be considered as having both a convective mass flux and volume flux. Volume flux may evolve independently from the mass flux. This gives rise to volume diffusion driven forces within constitutive equations. These corrections are here used to extend classical continuum two fluid models. Our approach also investigates Korteweg diffuse interphase constitutive model type to improve the two-fluid models. A gas-solid fluidised bed configuration is simulated and results are compared with experiments, with and without the modifications. The fluidised bed configuration is of a pseudo 2D bed with a uniform flow distributor at the base; various inlet velocities are simulated. The modification is applied to each phase which is then simulated independently to observe the effect of volume diffusion on each phase. Effects of the modifications are observed at 4 times the minimum fluidisation velocity. A decrease in the time averaged pressure drop for both modifications with the Korteweg diffuse interface model is shown showing the greatest decrease. To further test the capabilities of the modifications, a simulation of a circulating fluidised bed with six cyclones is conducted. It is a scaled model of a 660MWe super-critical pressure circulating fluidised bed. It consists of a 5.8m high riser section and has six cyclones arranged in axis –symmetric configuration which separates the particles at the top of the riser and are fed back to the riser near the base. The bottom of the riser has a distributor for the gas inlet which is represented by a uniform gas velocity inlet and a measured pressure drop. Simulations using the new models are compared with previously published data.

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