Visual and Pressure Signal Investigations on Bubble Produced by Ejector Bubble Generator

Abstract

This study aims to investigate the pattern of bubble flow coming out of the ejector bubble generator (EBG). The flow pattern was captured using a high-speed camera. The pressure signal on the bubble generator outlet was also recorded using a differential pressure transducer, which was then processed to obtain a probability density function (PDF) and Power Spectrum Density (PSD). It indicates the flow pattern flowing at the bubble generator outlet. The results of this study occurred a time delay in the production of bubbles coming out of the EBG. The greater the air flow rate, the lower the time delay for bubble production. The bubble flow region produced by EBG was classified into the entrance, developed, and fully developed regions. In the fully developed region, large and small bubbles are separated. The greater the air flow rate, the higher the two-phase flow pressure at the EBG outlet and the PDF has one peak with a skewness value that tends to be positive (shift to the right side). The maximum value of the spectrum is at a low frequency (<100Hz) with a low magnitude as an indicator of the bubble flow pattern in the EBG outlet.