Diagnosis of malfunction in fluidized beds is always a very difficult problem for a long time in academic circles and industrial circles. In this paper,we use acoustic sensor to measure the passive acoustic emissions ...Diagnosis of malfunction in fluidized beds is always a very difficult problem for a long time in academic circles and industrial circles. In this paper,we use acoustic sensor to measure the passive acoustic emissions (AE) from a bubbling fluidized bed.By comparison between acoustic and pressure signals,we found that acoustic signals are very sensitive to large particles such as agglomeration and particle sintering occurred in the bed and so on.Analysis of AE mechanism shows that AE measurement mainly stems from particle-chamber collisions and friction.AE measurements are completely non-intrusive and are not subject to erosion, corrosion, or plugging.Therefore, study and measurement of AE in different fluidization conditions will provide many new methods and trains of thought for detecting early deterioration of the fluidization quality.展开更多
Intermittency means the occurrence of a signal that alternates randomly between long regular phases and relatively short irregular bursts.In this paper,we simplify the mathematical analysis of pressure signal by ideal...Intermittency means the occurrence of a signal that alternates randomly between long regular phases and relatively short irregular bursts.In this paper,we simplify the mathematical analysis of pressure signal by idealizing it as a train of signals of zero duration and of size unity in a bubbling fluidized bed,0.30?m in diameter and 3.8?m in height.Therefore,the simplified signals are zero corresponding to the laminar signals and unity corresponding to irregular bursts.Statistics show that mean laminar length decays with excess gas flow above u mf ,obeying a power law < l > ∝(u-u mf ) -0.55 .Similar results were obtained by Daw et al (1995) .These results suggest that laminar motion is disturbal more frequently and chaotic burst occurs more frequently as gas velocity increases,and chaotic nature of Type-Ⅰ intermittency of fluidizing systems is confirmed further.The chaotic irregular bursts can be considered as the result of intermittent gas bubbles in fluidized beds.展开更多
In this study on the nature of pressuresignals generated by a detemfinistic or stochastic process in a Dubbilng fluidized bed, pressure fluctuation measurements were carried out in a 300-mm-diamet column at 0.090m and...In this study on the nature of pressuresignals generated by a detemfinistic or stochastic process in a Dubbilng fluidized bed, pressure fluctuation measurements were carried out in a 300-mm-diamet column at 0.090m and 0.40m above the distributor for different gas velocities.The method of detecting deterministric dynamic underlying pressure signals is proposed on the basis of predictability of pressure fluctuations.The deterministic nature of dynamics in fluidizing systern was verified.The deterministic level dynamics in fluidizing system was analyzed for different locations of pressure measurements and different gas velocities.展开更多
文摘Diagnosis of malfunction in fluidized beds is always a very difficult problem for a long time in academic circles and industrial circles. In this paper,we use acoustic sensor to measure the passive acoustic emissions (AE) from a bubbling fluidized bed.By comparison between acoustic and pressure signals,we found that acoustic signals are very sensitive to large particles such as agglomeration and particle sintering occurred in the bed and so on.Analysis of AE mechanism shows that AE measurement mainly stems from particle-chamber collisions and friction.AE measurements are completely non-intrusive and are not subject to erosion, corrosion, or plugging.Therefore, study and measurement of AE in different fluidization conditions will provide many new methods and trains of thought for detecting early deterioration of the fluidization quality.
文摘Intermittency means the occurrence of a signal that alternates randomly between long regular phases and relatively short irregular bursts.In this paper,we simplify the mathematical analysis of pressure signal by idealizing it as a train of signals of zero duration and of size unity in a bubbling fluidized bed,0.30?m in diameter and 3.8?m in height.Therefore,the simplified signals are zero corresponding to the laminar signals and unity corresponding to irregular bursts.Statistics show that mean laminar length decays with excess gas flow above u mf ,obeying a power law < l > ∝(u-u mf ) -0.55 .Similar results were obtained by Daw et al (1995) .These results suggest that laminar motion is disturbal more frequently and chaotic burst occurs more frequently as gas velocity increases,and chaotic nature of Type-Ⅰ intermittency of fluidizing systems is confirmed further.The chaotic irregular bursts can be considered as the result of intermittent gas bubbles in fluidized beds.
文摘In this study on the nature of pressuresignals generated by a detemfinistic or stochastic process in a Dubbilng fluidized bed, pressure fluctuation measurements were carried out in a 300-mm-diamet column at 0.090m and 0.40m above the distributor for different gas velocities.The method of detecting deterministric dynamic underlying pressure signals is proposed on the basis of predictability of pressure fluctuations.The deterministic nature of dynamics in fluidizing systern was verified.The deterministic level dynamics in fluidizing system was analyzed for different locations of pressure measurements and different gas velocities.
