【摘要】 使用声发射技术研究Geldart A/B/D类型颗粒的气固流化床塌落过程,根据声能量随时间变化曲线的特征,提出判别颗粒Geldart类型的判据,即A类颗粒的床层底部声能量曲线存在恒速下降的线性脱气段,而B、D类颗粒则不存在线性脱气段.进一步,结合Hilbert-Huang变换(HHT),分析塌落过程的声发射信号,获得塌落过程中声信号的边际谱,揭示了不同Geldart类型颗粒在塌落过程中的运动特性:A类颗粒与壁面间的碰撞比较强烈,而D类颗粒仅与壁面发生摩擦,B类颗粒介于A、D类颗粒之间.实验结果表明,结合HHT分析的声发射技术可用于气固流化床中流体力学的测定.更多还原

【Abstract】 Acoustic emission(AE)technique was used to study the collapse processes of Geldart’s group A/B/D particles in a gas-solid fluidized bed.According to characteristics of the variation curves of acoustic energy,a criterion to distinguish the Geldart’s group classification was presented.The variation curve of the acoustic energy at the bottom bed with time for Group A particles showed a linear degassing segment, but there was no linear degassing segment for Group B/D particles.Furthermore,based on Hilbert-Huang transform(HHT)analysis,the marginal spectrum of AE signals was obtained during the collapse processes and the particle motion behavior during collapse processes of Group A/B/D particles were revealed.Group A particles collide with the wall frequently while there are only friction interaction for Group D particles, and the movement characteristic of Group B particles is between Group A particles and Group D particles. The experimental results show that the acoustic emission(AE)technique based on HHT analysis is feasible for determining hydrodynamics of gas-solid fluidized beds.更多还原