气固流化床中空隙率信号的小波分析

Analysis of the Voidage Signal in Gas-Solid Fluidized Bed by Wavelet Transform

在(?)90mm×000mm 的有机玻璃流化床中,采用 PV4A 颗粒测速仪对不同粒径的沙、聚氯乙稀(PVC)颗粒在操作气速为0.262～0.524 m/s 下不同轴/径向位置的空隙率波动信号进行测定。选用 db2为小波函数对信号进行多尺度分解和进行连续小波变换,计算不同尺度下分解信号的功率谱密度函数。研究表明,细节信号反映的是颗粒脉动和小气泡的运动特征,呈现宽频分布,有很强的随机性;近似信号主要反应大气泡的运动特征,有明显的主频存在,且随操作条件变化;连续小波变换表明空隙率波动信号在微观结构上具有自相似性。

In a gas-solid fluidized bed ( [empty set] 90 mm × 1000 mm), the fluctuating signals of voidage for sand and poly(vinyl chloride) (PVC) with different diameters were measured by the PV4A particle velocity analyzer, at different axis and radius positions under the gas flow rate 0.262-0.524 m/s. The signals were analyzed with db2 of wavelet function by multi-scale decomposition and continuous wavelet transform. The power spectrum density of decomposed signal under different scales was calculated. The results indicated that the detail signal reflected the character of granule's pulse and little bubble's running and distributed in wide frequency with very strong randomization, and that the approximate signal with obvious domain frequency showed the character of big bubble's running chiefly and changed with operation conditions. The results of continuous wavelet transform showed the fluctuating signals of voidage has self-similar in microstructure.