Minimizing gas accumulation in two-phase flow within a diverging horizontal channel using cross-flow millimeter-size steps

Low-pressure separation zones in diffusers can lead to large air accumulations during two-phase flows, reducing pressure recovery. This issue is responsible for the performance drop in centrifugal pumps handling gas-liquid flows. Unlike pumps, diffusers without rotating components allow for more precise experimental characterization. This study aims to reduce gas accumulations through geometric modifications using cross-flow toothed steps. The diffuser is designed with an increasing included angle to ensure flow separation. Various two-phase flows were considered and recorded with high-speed cameras. Three toothed steps with teeth heights of 2, 5, and 8 mm were examined. The results indicate that these cross-flow steps significantly reduce gas accumulations, particularly at high water flow. Generally, the steps could enhance bubble dispersion and increase turbulence, thereby reducing gas accumulations. These findings will validate computational models and aid in optimizing real centrifugal pumps.