The effervescent injector uses a method of improving atomization by injecting gas into a liquid. This has the advantage of using more various fluids because there is little consideration for the amount of dissolved gas or the volatility of liquid to be considered in the existing two-phase flow injec...
The effervescent injector uses a method of improving atomization by injecting gas into a liquid. This has the advantage of using more various fluids because there is little consideration for the amount of dissolved gas or the volatility of liquid to be considered in the existing two-phase flow injector. In addition, the effervescent type injector has the advantage of achieving good atomization even at low pressure drop. Therefore, it is being studied for application to food and combustion fields. In addition, when gas is injected, the density of the sprayed mixture is lowered, and thus high pressure drop can be achieved even at a small flow rate. Therefore, studies are also being conducted to apply to throttling of rocket engines.
The effervescent injector forms a two-phase flow inside the injector. The two-phase flow develops in the form of bubbly flow to slug flow and annular flow as the flow rate of the gas increases. When slug flow appears, a pulsation that becomes unstable in spraying appears. If pulsation occurs, it adversely affects the atomization of droplets. Therefore, observing and classifying changes in two-phase flow is an important factor in determining the flow conditions of the injector. In addition, the atomization characteristics of gas injection type injectors are also an area of interest to many researchers. Therefore, the atomization characteristics of the effervescent swirl injector were measured using PDPA(Phase Doppler Particle Analyzer).
A plain orifice injector made of acrylic was manufactured to observe two-phase flow formed inside the effervescent injector. When the liquid flow rate was constant, as the GLR increased, it changed from bubbly flow to slug flow or annular flow. As the liquid flow rate increased, the change in two-phase flow due to the increase in GLR appeared in a more complex form. In addition, the smaller the diameter of the aerator's gas injection hole, the less slugs were found, and the larger the diameter of the gas injection hole, the more the slug flow were. Under the conditions of complicated two-phase flow, spraying showed unstable appearance.
In many studies, it is known that effervescent injectors have good atomization. Therefore, an experiment using PDPA was conducted to confirm the atomization characteristics of the effervescent swirl injector. In the case of distance from the injector outlet, the SMD value was similar with the increase in GLR, but it was found that the SMD gradually decreased with the increase in GLR as the breakup length approached. In addition, the distribution of the average droplet velocity inside the recirculation zone showed a higher value as the GLR increased. From the above results, it was confirmed that if the gas injection method is used in the swirl injector, better atomization occurs inside the spray, and the coalescence of droplets occurs actively after rapid breakup at the position where the liquid film exists.
The effervescent injector uses a method of improving atomization by injecting gas into a liquid. This has the advantage of using more various fluids because there is little consideration for the amount of dissolved gas or the volatility of liquid to be considered in the existing two-phase flow injector. In addition, the effervescent type injector has the advantage of achieving good atomization even at low pressure drop. Therefore, it is being studied for application to food and combustion fields. In addition, when gas is injected, the density of the sprayed mixture is lowered, and thus high pressure drop can be achieved even at a small flow rate. Therefore, studies are also being conducted to apply to throttling of rocket engines.
The effervescent injector forms a two-phase flow inside the injector. The two-phase flow develops in the form of bubbly flow to slug flow and annular flow as the flow rate of the gas increases. When slug flow appears, a pulsation that becomes unstable in spraying appears. If pulsation occurs, it adversely affects the atomization of droplets. Therefore, observing and classifying changes in two-phase flow is an important factor in determining the flow conditions of the injector. In addition, the atomization characteristics of gas injection type injectors are also an area of interest to many researchers. Therefore, the atomization characteristics of the effervescent swirl injector were measured using PDPA(Phase Doppler Particle Analyzer).
A plain orifice injector made of acrylic was manufactured to observe two-phase flow formed inside the effervescent injector. When the liquid flow rate was constant, as the GLR increased, it changed from bubbly flow to slug flow or annular flow. As the liquid flow rate increased, the change in two-phase flow due to the increase in GLR appeared in a more complex form. In addition, the smaller the diameter of the aerator's gas injection hole, the less slugs were found, and the larger the diameter of the gas injection hole, the more the slug flow were. Under the conditions of complicated two-phase flow, spraying showed unstable appearance.
In many studies, it is known that effervescent injectors have good atomization. Therefore, an experiment using PDPA was conducted to confirm the atomization characteristics of the effervescent swirl injector. In the case of distance from the injector outlet, the SMD value was similar with the increase in GLR, but it was found that the SMD gradually decreased with the increase in GLR as the breakup length approached. In addition, the distribution of the average droplet velocity inside the recirculation zone showed a higher value as the GLR increased. From the above results, it was confirmed that if the gas injection method is used in the swirl injector, better atomization occurs inside the spray, and the coalescence of droplets occurs actively after rapid breakup at the position where the liquid film exists.
주제어
#Atomization, Discharge coefficient, Effervescent Injector, Pulsation, Pressure drop, Sauter mean diameter, Two-Phase flow
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