Experimental study on flow oscillating mechanism of non-condensable gas jet through one- or multi-hole sparger in quiescent water

Abstract

Submerged gas jet plays a very important role in many industries occasion. It often causes load of pool structure induced by flow oscillation. Exploring the mechanism and key influencing factors of submerged non-condensable gas jet oscillation characteristics is of great significance to ensure the safe operation of the equipment. In the present work, the phenomenon of flow oscillation for non-condensable gas jet through a horizontal one- or multi-hole sparger from sonic to supersonic zone is studied experimentally. The steady and unsteady characteristic of flow process and flow structure are visualized by using high-speed camera, and pressure oscillation is obtained by simultaneous pressure measurement. Experimental results show that gas Froude number and sparger structure have great influence on the gas flow pattern. With Froude number increasing, gas flow pattern is obviously reinforced. Multi-hole sparger significantly weakens the gas jet behavior at horizontal direction away from holes comparing with one-hole sparger under the same Froude number. The spectrogram approaches of pressure oscillation indicates the dynamic pressure data contains two principal frequency components. First dominant frequency is identical with that of transient interfacial fluctuation, which is related to gas jet periodic expansion feedback and independent on Froude number and position. And second dominant frequency is not changed with the position, but decreases significantly with the increase of Froude number. Intensity of pressure oscillation increases with Froude number increasing and the distance from sparger decreasing. In addition, the multi-hole sparger can significantly reduce intensity of pressure oscillation under the same Froude number. Dimensionless relation is developed to evaluate the Froude number and sparger structure on the second dominant frequency and intensity of pressure oscillation. This study can be applied to well understanding of flow oscillation mechanism and provide technical support for looking for mitigation measures to reduce oscillation in the future.