Accurate measurement of particle velocity using a double disc anemometer in erosive wear experiments

Abstract

Accurately characterizing abrasive particle velocity ejected from a nozzle in a pressurized airflow is crucial for solid particle erosion quantification, abrasive jet micromachining, and abrasive slurry micro-jet experiments. A double-disc anemometer (DDA) is an economical particle velocity measurement apparatus which is cost effective to implement. The DDA method determines particle velocity using the time it takes for particles to travel a known distance between two rotating discs mounted on the same shaft. Since 1975, the DDA has been used to measure solid particle velocities in gas-particulate flow streams. Particle velocity measurement using a DDA is an intricate process, which the experimental procedure lacks published standardization outlining, operation procedures, comprehensive error analysis, and post-processing advice, all required to report accurate and reliable results. This paper presents a new and improved DDA design, automated post-processing procedures, and experimental validation characterizing the flow development of $66\mu m$ glass bead abrasive blasted with a maximum mean particle velocity of $95.3m/s$. State-of-the-art laser Doppler velocimetry equipment (LDV) was used to validate the DDA results with an agreement of −2.8 % on average. Further, this paper investigates the disc separation distance and shaft angular velocity, discussing configuration recommendations for reliable measurements, with an optimal reported uncertainty of ± 3.2 %. Finally, a novel scarring analysis method was conducted to identify the intricacies of how the instrument’s geometries affect the velocity calculation.