Investigations into the Sensing Mechanism of Acoustic Emission Sensors for Particle Size Measurement in a Particular Case: Normal Incidence

In situ continuous particle size measurement is desirable in a variety of industries. Acoustic emission (AE) is a well suitable technique to achieve on-line continuous sizing of particles in pneumatic conveying pipelines, which utilizes the AE signals due to the impact of particles with a waveguide protruding into the particle flow. Although early attempts have been made to reveal the relationship between the AE parameters and the particle size, the fundamental sensing mechanism of the AE-based technique for particle size measurement is still not established. For instance, the effect of particle size distribution on several AE parameters remains to be examined. This paper aims to gain an in-depth understanding of the AE sensing mechanism for on-line particle sizing by quantifying the parameters of the AE signal, including peak amplitude, count, rise time, duration, energy and root mean square (RMS) value. A theoretical model considering the energy dissipation during plastic impact is also developed to determine the particle size from the AE signal. The proposed method is verified through experimental tests with glass beads on a single-particle test rig. Experimental results obtained indicate that the proposed method is feasible to infer particle size information from the energy of an impact event. The particle size can be measured with a relative error mostly within over the range from 0.4 mm to 1.2 mm.