Development of a method to dagas oil utilizing cavitation

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The aim of the study is to develop a new method to degas a mineral oil making the most of cavitation. The study plan consists of 3 steps ; 1.utilization of cavitation to separate gas from an oil, 2.removal of cavitation bubbles from an oil, 3.examination of dependency of cavitation initiation on gas solubility in an oil.In order to cause cavitation and subsequent gas separation in an oil, a sharp-edged orifice and piston-cylinder have been used. Cavitation occurs in an oil when it is sucked into the cylinder through the orifice. The following technique has been introduced to accelerate the degassing and bubble removal : at the middle of the suction process the orifice is closed and the piston moves further down to the stroke end. Then the pressure goes down almost to absolute zero, which helps separate gas from the oil and also bubbles to rise faster to the surface. In the real test this method was able to decrease gas solubility of an oil contained in an open-air tank to less than 1/5 of the saturated solubility. It has been discovered that the orifice diameters, the oil temperature and the timing of orifice closure have little influence upon the minimum gas solubility attained. That means a larger orifice and a faster movement of a piston should be adopted to degas an oil more effectively.In order to investigate the influence of gas solubility on cavitation initiation, pressure differences across an orifice to start cavitation have been examined for the flow of various oils with different gas solubilities. From this test it has been confirmed that a smaller gas solubility in an oil can reduce the possibility of cavitation. In conclusion the present method has proved useful to suppress cavitation in oil hydraulic systems.