207 気流による液泡分裂に関する液体物性の効果(流体工学(乱流・混合・拡散))

Abstract

To reduce the greenhouse gases, bio fuels are developing as an alternative fuel instead of fossil fuels. As carbon dioxide and so on are the causes of global warming, low carbon combustion is one of the crucial issues to conserve the global environment. Liquid atomization technology should contribute to the field of fuel combustion and others, such as the cooling of exhausted warm water at geothermal power plants and so on. A liquid bubble contains gas in a liquid drop. So, it has a larger surface area than a liquid drop of the same mass. It could have the advantage for fuel combustion and cooling of exhausted warm water. In order to apply it in these areas, effects of liquid physical properties for liquid bubble breakup due to airstreams were investigated. Experiments were conducted using a horizontal air-suction-type wind tunnel. Liquid and air were fed to a nozzle, and uniformly sized liquid bubbles were produced. The liquids used in the experiment were water and several kinds of ethanol in water solutions. The breakup processes and characteristic breakup patterns were precisely observed using a digital high-speed video camera. The displacement of liquid bubbles in the airstream was measured in the entire process. The deformation rate was also measured. The author has been studying on the deformation and breakup of liquid bubbles and liquid drop, such as breakup [1-3], displacement [4, 5], deformation [6, 7]. The liquid bubble has many important scientific applications such as the cooling of warm exhausted water, fuel combustion [8], and a compound liquid jet [9]. It is also useful for the study of structure of collapsing liquid drops and liquid bubbles by shock waves. By comparing a structure of collapsing liquid bubbles with liquid drops, the collapsing mechanism was revealed in a high-speed airstream behind a shock wave [10-12]. If liquid bubbles are used to combust bio-ethanol fuel, biodiesel fuel (BDF), and glycerin which is a by-product of BDF, more effective combustion could be obtained than in the case of liquid droplets. The experiment was conducted to investigate the effects of liquid physical properties for liquid bubbles breakup due to airstreams. The breakup pattern is impacted due to surface tension, and viscosity of liquid. Several characteristic deformation and breakup patterns are observed. Some of them are never observed for liquid drops. The breakup processes and characteristic breakup patterns are precisely observed. The displacement of liquid bubbles in the airstream is measured in the entire process. The deformation rate, that is, a time variation of liquid bubble diameters is also measured. These data are obtained by analyzing the breakup processes recorded by the digital high-speed video camera.