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.