Numerical Analysis of Flow in Bubble Eliminator : Evaluation for Removal Performance of Bubbles

建設機械や産業用機械は油圧システムを動力源として作動している。これら油圧システムにおけるパワーの伝達媒体である作動油中に含まれる気泡は、システムの動作特性に影響をおよぼし、多くの場合、油圧機器トラブルの原因となる。そこで近年、旋回流を利用して油中気泡を取り除く気泡除去装置が開発された。この装置は旋回流により管内に圧力場を作り、圧力勾配を利用して気泡を除去することが出来る。本研究では、この気泡除去装置の気泡除去性能を明らかにするために、流れの数値解析を行い、性能の良い装置の最適形状を求めることを目的とする。Air entrainment in working fluids has greatly detrimental effects on function and lifetime of the fluid power components and systems. This may cause major problems such as cavitation and aeration, noise generation and vibration, oil temperature rise, and deterioration of oil quality. Especially, when bubbles in oil are compressed adiabatically at the high pressure in a pump, the temperature of bubble rise sharply and the surrounding fluid temperature also rise. Thus, it is important to eliminate the air bubbles from the oil to preserve oil quality, system performance and to avoid possible damage of the components. One of the authors has developed a newly device using swirl flow for bubble elimination capable of eliminating bubbles and of decreasing dissolved gases. This device is called the Bubble Eliminator. In this paper, numerical analysis has been performed for clarifying swirl flow characteristics and pressure distributions. The numerical analysis of two-phase flows has also been carried out to investigate the performance of bubble removal. As results of the numerical simulation, we will design a more efficient type of bubble eliminato