Development of a method to dagas oil utilizing cavitation

本研究的目的是开发一种新的方法，以脱气矿物油充分利用空化。研究计划包括三个步骤：1.利用空化作用使油中的气体分离; 2.去除油中的空化气泡; 3.研究空化起始对油中气体溶解度的依赖性。当油通过节流孔被吸入气缸时，就会发生气穴现象。以下技术已被引入以加速除气和气泡去除：在抽吸过程的中间，孔口关闭，活塞进一步向下移动到冲程末端。然后压力下降到几乎绝对零度，这有助于将气体从油中分离出来，气泡也会更快地上升到表面。在真实的测试中，该方法能够将露天罐中的油的气体溶解度降低至饱和溶解度的1/5以下。已经发现，节流孔直径、油温和节流孔关闭的时间对所获得的最小气体溶解度几乎没有影响。为了研究气体溶解度对气穴形成的影响，对具有不同气体溶解度的各种油液进行了气穴形成的压力差试验。从该试验中已经证实，油中较小的气体溶解度可以降低气穴的可能性。总之，本方法已被证明是有效的抑制油液压系统中的气蚀。

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.