Improved Aeration Using Perforated Venturi Throat of a Vertical Liquid Jet System with Downcomer

The performance of a vertical water jet system with a downcomer for bubble generation has been investigated experimentally. The aeration rate was controlled using perforated throat Venturi with 2, 4, 8, and 16 holes of 1 mm diameter each. Moreover, the bubble plume size and the Sauter mean diameter (SMD) were investigated by image processing obtained from a high-speed camera and a particle sizer algorithm. The void fraction and the entrained gas flow as a function of the liquid flow rate were also studied. A new correlation for the entrained gas flow rate as a function of the Froude number and the ratio of the perforation to throat area is proposed, with high accuracy. The effect of liquid flow on the bubble diameter was analysed for different levels of perforations using probability density function (PDF). The bubble penetration depth was also shown for different perforations at different liquid flow rates. The penetration depth increases significantly with the liquid superficial velocity. The Sauter mean diameter decreases linearly with the liquid superficial velocity as well as the void fraction. The results demonstrate an influence of the number of aspiration holes on the size of the bubbles generated such that the Sauter mean diameter increases with the increasing number of holes in the perforated section. The proposed controlled Venturi flow rate and confined plunging jet system technique is tested in this paper for the first time in the literature and shows considerable potential for controlling water aeration.