Spectral Dynamics of Computer Simulated Two-Dimensional Fewtube Fluidized Beds

摘要

Fluidized bed combustion technology attracts intense commercial interest for its capability of burning high-sulfur coal in a more economic and environmentally acceptable manner, despite the unsolved erosion problem. Detailed knowledge of the complex phenomena of solids circulation and bubble motion in the bed could enhance the understanding of the problem and find solutions. Argonne National Laboratories (ANL) has been developing a methodology to investigate local erosion phenomenon in bubbling fluidized bed combustor (FBC) systems: (1) use of state-of-the-art two-phase two-dimensional hydrodynamic computer model (FLUFIX) to compute temporal and spatial distributions of the flow properties in an FBC and (2) use spectral analysis and several separated erosion models to evaluate flow dynamics and local erosion patterns and rates. In this paper, the spectral analysis uses the computational hydrodynamic results of a two-dimensional generic fewtube FBC system to correlate flow properties, porosity, pressure and velocities, as well as to determine oscillation modes and bubble propagation speeds. Several findings from this analysis are: flow properties have major oscillation modes of frequencies ranging from 0.7 to 4 Hz; porosity and pressure oscillations propagate from the bottom of the bed up with propagation speeds ranging from 0.4 to 1 m/s; pressure is well correlated with the lagging porosity at a location; phase diagrams show the randomness of oscillations but the attractor leading to chaotic motion is not found. 14 refs., 11 figs.