Calibration and performance assessment of an innovative high-temperature cavitometer

Abstract

© 2016 The Authors. This paper describes a series of systematic experimental studies to evaluate the performance of a high-temperature cavitometer under well-controlled conditions. The cavitometer was specifically designed for measurements in liquid metals: it operates through a long tungsten waveguide (probe), providing thermal protection to the piezo sensing elements placed outside the hot area, and with sufficient bandwidth to enable the monitoring of broadband acoustic emissions associated with cavitation activity. It was calibrated electrically, and acoustically, at kHz and MHz frequencies, and so can be used to estimate acoustic pressures (in Pa), providing physical, and consequently practical, meaning to cavitation measurements within liquid metals. Results obtained from ultrasonic sources in a cylindrical vessel using water showed that the cavitometer is a reliable and robust device for characterizing direct field acoustic pressures and broadband emissions from the resulting cavitation. Additionally, preliminary characterization of the real-time acoustic pressures during ultrasonic processing of liquid aluminium (Al) in a standard clay-graphite crucible were performed for the first time. The use of the calibrated cavitometer will establish a more generalized approach for measuring the actual acoustic pressures over a broad range of liquid temperatures within a sonicated medium, demonstrating its potential use as a tool for optimizing, controlling, and scaling-up processes.