• 한국분무공학회지
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• 제19권4호
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• pp.167-173
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• 2014

The spray characteristics of Gas-Centered Swirl Coaxial Injector was investigated that there were different characteristics with or without gas flow. As gas flow was accelerated, the momentum of gas was transferred to the momentum of liquid in the low liquid Reynolds number. Therefore, the axial velocity of liquid was increased and the measured value was smaller than without gas flow. However, in the high momentum flux ratio, the momentum transfer hardly occurred and the results had constant values. As the recess length was increased, the mixing area of gas and liquid also was increased, the results were decreased.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.320-323
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• 2008

In this study the effect of collision model was evaluated in spray field by CFD. A collision is basically the interaction between droplets and criteria of collision is determined by drop Weber number, impact parameter, and drop-size ratio. Early developed collision model considered coalescence and grazing collision with the exchange of momentum. However in experimental research there were bouncing, coalescence, reflexive separating and stretching separating in interaction between droplets. In this study the collision considering such complex phenomena is modeled and was compared with the basic collision model.

• 한국분무공학회지
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• 제22권4호
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• pp.159-168
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• 2017

Numerical studies on the spray characteristics of closed-type and open-type swirl injectors were conducted using ANSYS Fluent. By changing injection pressures, discharge coefficient and spray angle were calculated using the Reynolds stress BSL turbulent model. The numerical results were compared with previous experimental data to examine their accuracy. For a closed-type swirl injector, spray angles matched well with experimental results and discharge coefficients showed approximately 8% differences. On the contrary, discharge coefficients of an open-type swirl injector were similar with experimental result but its spray angles presented around 15% differences. Though the numerical results were not perfectly consistent with experimental data, it is thought that they could be sufficiently used for analyzing spray characteristics, specially which is hard to be measured from experiments. Numerical simulation with different turbulent models was also performed to examine their effects on the numerical results.

• 한국분무공학회지
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• 제3권1호
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• pp.34-42
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• 1998

The correlation between the droplets size and the velocity are investigated for an intermittent spray of the pintle type fuel injector employed in a port injection gasoline engine. The analysis such as the mean droplet size, SMD, and velocity under the fixed injection period and varied fuel pressures are conducted utilizing PDPA systems. As results, the experimental data obtained, show that the larger droplet sizes. the higher velocities during the spray tip arrival time, and that at Z=70mm, r=8mm, both droplet sizes and velocities are peak. At the upstream, flow of droplets are dominated by injection pressure, which are more effected inertia force of droplets at the downstream of Z=70mm.

• 한국분무공학회지
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• 제23권2호
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• pp.49-57
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• 2018

Numerical study under single-injection on bi-swirl coaxial injectors with different recess lengths was performed using ANSYS Fluent. The bi-swirl coaxial injectors which consisted of inner closed-type and outer open-type swirl injectors, had three different recess lengths. By changing mass flow rates, numerical simulation was repeated using the Reynolds stress BSL turbulent model. The numerical results such as discharge coefficient and spray angle were compared with previous experimental data and were found to be approximately matched well with them, irrespective of recess length. Quantitative data which was hard to be measured from experiments, were successfully obtained through the present numerical study.

• 한국추진공학회지
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• 제5권4호
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• pp.12-19
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• 2001

액체 로켓엔진의 산화제 분사기에 대한 유출 특성을 고찰하였다. 공동 유동 영역에서 유출 특성에 대한 수치해석 결과를 구하였으며 실험 결과와 비교하여 정량적인 정확성을 확인하였다. 유출계수는 공동 유동의 경우, 공동 수에 비례하였고 공동이 발생하지 않을 경우, 공동 수의 영향을 받지 않았다. 반면에 레이놀즈 수는 유출계수에 큰 영향을 미치지 않았다. 레이놀즈 수가 증가하면 유출계수는 약간 증가하였으며 이는 마찰 손실의 상대적인 감소로 풀이된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.229-234
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• 2004

The objective of the present study is to conduct model combustion tests for double swirl coaxial injectors to identify their combustion stability characteristics. Gaseous oxygen and mixture of methane and propane have been used as simulant propellants. Two model chambers tuned to the If acoustic resonance mode of a full-scale thrust chamber were manufactured to be used as a combustion cylinder. The main idea of the experiment is that the mixing mechanism is considered as a dominant factor significantly affecting combustion instability in a full-scale thrust chamber. Self-excited dynamic pressure values in a model chamber show different combustion stability zones with respect to a recess number. Upon test results, couplings between combustion conditions and the IT acoustic resonance mode become strengthened with the increase of a recess length.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.282-287
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• 2004

Unielement combustion tests were conducted using coaxial bi-swirl injectors. Major experimental parameters were a recess length and a fuel-side swirl chamber. Combustion efficiency mainly depends on a mixing mechanism for the present coaxial swirl injectors. Low-frequency pressure excitations around 200Hz were observed for all injectors. However, dynamic behaviors considerably differ for an external and an internal mixing case controlled by a recess length. The internal mixing induces mixture to be biased at a specific frequency in a mass flow rate, which results in a relatively high amplitude of pressure fluctuations but results for the external mixing case show that fuel and oxidizer mixture flow carries more complicated, multiple wave characteristics due to broad mixing region as well as disintegration and merging phenomena of propellant films.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.364-366
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• 2012

로켓 엔진의 연소실 내 음향학적 거동과 음향 감쇠 효과를 정량화하기 위한 방법을 연구하였다. DMD(Dynamic mode Decomposition) 방법을 이용한 결과와 기존의 정량화 방법인 damping factor를 이용해 구한 음향 감쇠 효과의 경향성을 배플 분사기가 장착된 연소실내의 음향 감쇠 정도를 비교 분석하여 나타내었다. 비교 결과, 기존의 정량화 방법과 DMD 방법을 이용해 구한 음향 감쇠 정도의 경향성이 일치하는 것을 확인하였다.

• 한국분무공학회지
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• 제23권4호
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• pp.159-168
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• 2018

Thrust throttling in a liquid rocket engine can be implemented via several ways such as high pressure drop injector, dual manifold, multiple chamber, pintle injector, and gas injection. Thrust throttling using gas injection controls thrust by usually injecting inert gas into propellant through an aerator to reduce the propellant's bulk density. In this study, the outside-in aerator was used in the propellant line to create two phase flow. Closed-type, open-type, and screw-type bi-swirl coaxial injectors were utilized for investigating throttling characteristics such as pressure drop, mixture density, and discharge coefficient according to gas-liquid mass ratio.