Study On The Hydrodynamics Of Dense Gas-particle Two-phase Turbulent Flows In Fluidized Bed

Dense gas-particle two-phase turbulent flows in fluidized bed has been widely applied in the field of chemical engineering, energy, pharmaceutical engineering and sustainable energy. But, it is not clear for a better understanding of complex hydrodynamic mechanism in particle-fluid system. Therefore, experimental measurement technique is limited to some extents. Up to now, numerical simulation approach has been utilized as an importance research methods with rapid development of calculation algorithm and facilities.In this work, mathematical model,algorithm design and source code debug are all based on the Euler-Euler continuum medium two-fluid model and kinetic theory of granular flows, as well as the two-phase turbulent second-order moment closure idea. Based on the unified two phase turbulent second order moment-particle temperature model, an improved unified second order moment-particle temperature model with frictional stress model are established to consider the rotation particle collision. A set of calculation code are performed for numerical simulation of dense gas-particle turbulent flows in downer. Distributions of particle volume fraction,particle veloctiy, correlation of gas particle velocity fluctuation and particle temperature are obtained and validated by experimental data. Predicted results considering particle frictional stress are better than those of not considering ones. With respect to the momentum coefficient between gas and particle, Beestra’s model deduced from kinetic theory of granular flows has a accurate prediction for particle volume fraction, especially at near wall region with higher particle volume fraction, which is better than those of semiempirical fitting correlations of Wen and DeFelice.Wavelet analysis approach has advantages of multi resolution behaviors in Space and time frequency analysis and it is superior to conventional FFT methods. It becomes an important approach to capture the complex flow structure more accurate. Using KFIX code based on the kinetic theory of granular flows, bubble movement behavior, particle volume fraction, particle averaged velocity, particle dispersion characters in bubble fluidized bed are obtained. A series of pressure fluctuation signals are analysed by wavelet approach for indicating the particle fluctuation and bubble movement. A typical non-linear character of dense gas-particle system are observed clearly.