Experimental Fluid Dynamics Study in a Fluidized Bed by Deterministic Chaos Analysis

Abstract

Differential pressure fluctuations in gas-solid fluidized beds were analyzed by chaos analysis (construction of attractors, correlation dimension, Kolmogorov entropy) and mutual information. Experimental fluidization tests of three different particles were conducted. Two of them are from Geldart group B and one from Geldart group D. The fluidization experiments were performed in a cylindrical bed with 0.07 m i.d. and 1.0 m high. Pressure fluctuations were measured by three pressure transducers, and their signal time series were analyzed in the time domain (mean and standard deviation) and in the frequency domain (power spectra) for comparison and complementation of chaos analysis. Analyses in the time domain allowed a good estimation for determining whether or not the system is fluidized. The Fourier spectra provided more detailed information that could identify other phenomena such as the presence of bubbles. The chaos tools produced sensitive results, offering a qualitative and quantitative analysis for identification of the phenomena that occur in fluidization. Three different fluidization regimes could be indentified: multiple bubble bed, slugging bed, and exploding bubble bed.

Computational study of the bubbling-to-slugging transition in a laboratory-scale fluidized bed

“…As the simulated gas flow increased, the autocorrelation became more periodic (especially at higher levels in the bed), revealing the impact of a few, large bubbles. The time scales of the largest [15,26,28,79,83], as well as statistical distribution variations in the pressure fluctuations, such as those presented here, should be useful diagnostic tools for monitoring the bubbling-to-slugging transition. As noted above however, interpretation of these diagnostics will depend greatly on where (H/Ho) the pressure measurements are made.…”

“…Numerous statistical descriptions, some of which are based on concepts from nonlinear and complex systems theory, have been proposed for characterizing time-series measurements from fluidized beds [15,26,30,73,[77][78][79][80][81][82][83]. For this study we elected to concentrate on more traditional statistical measures to simplify the analysis and development of relationships between the pressure and bubble patterns.…”

Obtenção Da Velocidade De Mínima Fluidização a Partir Da Transformada De Wavelet

“…Os sinais utilizados neste trabalho foram adquiridos por Castilho et al (2011). Para este trabalho foram selecionados os sinais decorrentes de duas partículas do grupo B da classificação de Geldart, as quais tiveram seus diâmetros de partícula determinados, mediante peneiramento, segundo o diâmetro médio de Sauter.…”

“…Quanto ao ar comprimido, este se encontrava a uma temperatura próxima a 15°C. Maiores detalhes do equipamento pode ser encontrado em Castilho et al (2011).…”

Measurement, monitoring and control of fluidized bed combustion and gasification

“…Chaos analysis in fl uidization has been applied to describe the behavior of bubbles (Briongos et al, 2011;castilho et al, 2011), to retrieve information on the fl uidization regimes (Bai et al, 1997;van der stappen, 1996), and to assist scale-up and reactor monitoring (nijenhuis et al, 2007;Rüdisüli et al, 2012c;van ommen et al, 2004b. however, since there is no convincing proof that fl uidized beds exhibit low-dimensional chaotic behavior, Drahos and Ruzicka (2004) have postulated that chaos analysis is only useful if the sought information cannot be retrieved by simpler (linear) analysis.…”