• 한국분무공학회지
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• 제27권3호
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• pp.144-154
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• 2022

Gas injection is a technique applied to improve throttling in liquid rocket engines and atomization in effervescent injectors. When a gas is injected into a liquid, it creates a two-phase flow inside the injector. The changes (bubbly flow, slug flow, annular flow, etc.) in the two-phase flow affect the injector's spray characteristics. In this study, cold-flow tests were performed by using three injectors with different orifice diameters and four aerators with different gas injection hole diameters. The experiments were done by changing the thrust ratio (liquid mass flow rate ratio) and gas-liquid mass flow rate ratio. Two-phase flow transition, breakup length, and discharge coefficient according to the injector/aerator design and flow conditions were investigated in detail.

• 한국분무공학회지
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• 제24권1호
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• pp.27-34
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• 2019

An experimental study on the spray characteristics of aerated-liquid jets discharged from effervescent injectors to a subsonic crossflow was conducted to investigate effects of a gas to liquid mass ratio (GLR) and a ratio of the orifice length to the diameter (L/d). The present effervescent injectors consist of a plain orifice injector and an aerator. To analyze breakup length and spray trajectory, instantaneous spray images were taken by a high speed camera. As the GLR increased, the spray penetration became higher under the same liquid mass flow rate and the breakup length became shorter due to the bubble expansion or the annular liquid film breakup. To predict the spray trajectory of two-phase flow jets into the crossflow, the homogeneous and the separated flow models were compared.

• 한국분무공학회지
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• 제24권4호
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• pp.185-193
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• 2019

The effervescent atomizer is one of twin-fluid atomizers that aeration gas enters into bulk liquid and two-phase flow is formed in the mixing section. The effervescent atomizer requires low injection pressure and small amount of aeration gas, as compared to other twin-fluid atomizers. In this study, cold flow test was conducted to investigate the spray characteristics of aerated impinging jets. The present effervescent impinging atomizers were composed of the aerator device and like-on-like doublet impinging atomizer which had different impinging angles. To analyze the spray characteristics such as breakup length and droplet size distribution, the image processing technique was adopted by using instantaneous images at each flow condition. Non-dimensional parameters, induced by the homogeneous flow model, were used to predict the breakup length. The breakup length was decreased with the mixture Reynolds number and impinging angle increasing. The result of droplets showed that the size distribution was axisymmetric about the center of the injector and their diameter tended to decrease with increasing GLR.

• 한국추진공학회지
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• 제23권2호
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• pp.1-12
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• 2019

액체로켓엔진에서의 추력조절을 위해 기체주입식 가변추력 방법에 대한 기초적인 연구를 수행하였다. 기체주입식 가변추력은 간단한 구조로 추력을 조절할 수 있을 뿐만 아니라 밀도 감소에 비례하여 증가된 분사차압에 의해 미립화 성능 증가라는 장점을 갖는다. 본 연구에서는 기체주입식 와류형 분사기를 이용하여 액체 질량유량과 기체주입량의 변화에 따른 분무 불안정, 분무형상, 분무각, 분열 길이와 같은 분무특성을 살펴보았다.