On-line Deaeration of Liquid Utilizing a Maximum Developed Stationary Cavity in Cavitation

A new idea has been proposed to deaerate liquid flowing in a channel on an on-line basis, utilizing a near-vacuum cavity formed on the wall downstream of the point of separation in most vigorous cavitation. The idea has been materialized such a concrete method as connecting a vacuum pump to the cavity formed in a cylindrical constriction and sucking out gas coming out successively from the surrounding liquid. When the method was tested in a hydraulic unit with 25 L of oil in the tank, the gas solubility in the oil was lowered by 40% in 30 minutes. The two experimental factors such as a flow rate through the constriction and air dissolution from atmosphere were examined in the same test unit in terms of their effects on the method's capacity, showing that a larger flow rate results in a better deaseration capacity and a float covering the free surface of oil in a tank works to improve the capacity by preventing air dissolution into the oil. When the critical flow rate at which an incipient cavity emerged on the entrance edge of the cylindrical constriction was measured for oils with different air solubilities, it turned out a 60% reduction of gas solubility increased it by 33%. Moreover oil cloudy with cavitation bubbles after a start of deaeration became more and more translucent as the deaeration proceeded.