Numerical Simulation And Experimental Study On The Gas-Particle Two-Phase Flows In Cyclone Separators

The strong swirl turbulent flow in cyclone separators caused major difficulties in modeling their internal gas-solid flows. In this thesis, the strongly swirling turbulent flow in gas-solid cyclone separators is simulated using the standard k-? RNG k- and Reynolds stress equation models (DSM). It is demonstrated via comparison between the simulation results with experimental data that the DSM model is superior to the other models. It correctly predicts the Ranking vortex of tangential velocity and the anisotropic behavior of the Reynolds stresses. Certain discrepancy remain between the simulation results and the experiment results, not only caused by the turbulent model, but also by the simplification of the inlet boundary condition and the mesh generation.Modeling gas-particles interaction flows is complex. In this thesis, gas-phase transport equations coupled with the gas-particle interaction are derived based on the DSM turbulent models to handle the interaction of momentum and kinetic energy of turbulence between the gas and particles. The improved Lagrangian stochastic model has attributed to the successful prediction of the turbulence inhomogeniety, turbulence anisotropy, and particle crossing-trajectories effect. The collisions between the particles are also considered in this thesis.Numerical results for the particles trace and collection efficiencies in the cyclone separator were compared with available experimental data and with theoretic models. The gas-particles two-phase flows in the horizontal pipe and U-beam separator were also studied in this thesis.Electrical capacitance tomography (ECT) is a new method to measure the volume distribution of solids. It is not affected by the opacity of particles. In addition the method is non-intrusive and rapid (150 frames per second at current stage of development), which suggests that certain fluctuations in the internal flow can bemeasured. In this paper, ECT is used to investigate the distribution of solids in a cyclone separator. The relationship between the inlet velocity and the flow rate of particles are investigated. Also, based on the 2D images, virtual 3D images reconstruction was implemented via a novel interpolation method. 3D images are displayed through a Windows Open-GL program. This approach has been tested on the CFBs and the formation and motion of the bubbles can be tracked clearly in 3D. The 3D image are also compared with the CFD results and good agreements are obtained.In this paper theoretical and experimental studies are carried out on cross correlation techniques using electrical capacitance sensors applied to non-intrusive restrictive velocity and mass flow rate measurement in a cyclone separator. The mass flow rate is determined from two parameters, namely the solids velocity and the volumetric concentration. The former is measured by cross-correlating the capacitance fluctuations caused by the conveyed solids, and the latter by using the image reconstruction method. The two parameters are then combined to yield the solids mass-flow rates. In addition, measurements are possible non-intrusively and rapidly(~200 frames per second) that makes online analysis possible. The feasibility and reliability of this measuring method are verified by the experimental results.