声波信号多尺度分解与固体颗粒质量流率的测定

利用声发射检测技术，根据不同速度的颗粒撞击壁面产生不同能量的声发射信号，结合小波分析，建立了单粒径颗粒质量流率预测模型，该模型可以定量描述颗粒质量流率随特征频段的声发射信号能量与表观气速的变化规律。以空气-聚乙烯颗粒体系为例，分别考察了0.84、0.59、0.42、0.21 mm 4种线性低密度聚乙烯颗粒，在表观气速为4.62～6.35 m·s-1条件下的声发射信号。在考察的气速范围内，在0～500 kHz频率范围内对声发射信号做7尺度的小波分解，发现特征频段的声发射信号能量与表观气速平方之比和固体颗粒的质量流率呈线性关系。同时，基于单粒径颗粒质量流率预测模型，根据混合颗粒声发射能量为各单一粒径颗粒声发射能量的线性叠加，得到混合颗粒的质量流率预测模型，模型的计算值与称重法获得的质量流率相比，平均相对误差为4.15%，表明声发射检测技术能便捷、快速、准确、环保地实现循环管内颗粒质量流率的在线检测。

Multi-scale analysis of acoustic emissions and measurement of particle mass flowrate in pipeline

A model of particle mass flowrate was proposed to explore the quantitative relationship between acoustic emission (AE ) energy, superficial gas velocity, and particle mass flowrate, by using wavelet transform and based on the mechanism that AE signals with different characteristic frequency band energies are emitted when the particles with different velocities impact with the wall.The system of air and polyethylene particles were used as an example and investigated in the superficial gas velocity range from 4.62 m·s-1 to 6.35 m·s-1 and with four kinds of single size LLDPE particles 0.84 mm, 0.59 mm, 0.42 mm, 0.21 mm in size respectively.AE signals were analyzed by using 7 scales wavelet transform in the frequency range from 0 to 500 kHz.It was found that the ratio of the characteristic frequency band energy to the square of the superficial gas velocity varied linearly with particle mass flowrate.Based upon the proposed model for predicting mass flowrate of single size particles, and according to the principle that the AE energy of multi-size particles is a linear superposition of the AE energies of single size particles, the prediction model for multi-size particles was obtained.The average absolute relative error between the values calculated with the prediction model and the experimental values obtained by weighing the polyethylene particles was 4.15 %.Therefore, this model could predict particle mass flowrate in an environmentally friendly way with fairly good accuracy.