• Journal of Advanced Marine Engineering and Technology
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• v.18 no.4
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• pp.94-101
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• 1994

실험 데이터는 급확대비 3:1 팽창의 시험관에서의 실험결과를 나타내고 있으며, 실험에 이용된 동작유체로써는 공기가 사용되었다. 입구관에서 레이놀즈수는 60,000으로부터 120,000까지 변하게 하였고, 스월강도는 0으로부터 16까지 변화되게 하였다. 균일한 열 플럭스 경계조건이 사용되었는데, 그 결과 관벽온도 및 체적온도는 24$^{\circ}C$로부터 71$^{\circ}C$까지에 걸쳐 나타났다. 플롯상에 국소 Nusselt수는 최대 열전달점에서 정점을 이루는 모습을 보여 주고 있다. 스월강도가 0으로부터 최대값으로 증가 되었을때, 최고 Nusselt수의 위치는 시험관에서 4로부터 1스텝 하이트로 변경되는 것이 조사되었다. 이러한 최대 Nusselt수의 상류부 이동은 완전 발달된 유동에서의 값보다 2.2배에서 8.8배나 많은 그의 크기를 증가시킨다고 할 수 있다.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.27-36
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• 2023

To understand the atomization performance in gas-liquid swirl-coaxial injector applied to a small rocket engine, a cold-flow test was performed by varying the design parameters and supply condition of propellants. As the swirl-chamber diameter and the angle of the convergent section, which are design parameters of injector increased, the spray performance of the injector improved by increasing the swirl strength. In addition, as the gas-liquid momentum-flux ratio increased, the gas flow separated some of the droplets from the liquid film, and a gas-droplet mixture core was formed in the center of the spray sheet.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.7
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• pp.70-75
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• 2005

In this study, experimental investigations were conducted on NOx emission characteristics with fuel swirl flow in swirl combustor. Many types of vanes, which altered air and fuel swirl angles, were employed to verify the mixing processes. For strong air swirl, fuel counter-swirl resulted in relatively large turbulent intensity, high energy to the high frequency region and narrow width of high temperature region compared with co-swirl condition. These effects of fuel counter-swirl resulted in low NOx emission characteristics at strong air swirl condition. And NOx reduction mechanism was also discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.70-75
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• 2012

In this paper, the regression rate of the End-Burning Hybrid Rocket with variation of swirl intensity was investigated experimentally with the variation of fuel diameter, injector shape and angle. When fuel grain diameter is large, fuel mass flow rate increases. And the injector diameter increase, fuel regression rate decrease. The impinging effect of oxidizer flow on fuel surface for fuel combustion efficiency is stronger than swril effect in this End-burning propulsion system. The relation between the regression rate, oxidizer mass flux and swirl intensity was obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.232-236
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• 2006

하이브리드 로켓에서 그레인 전체 부분에서 고른 연소율 향상을 이룰 수 있는 방법으로 스월 유동과 나사산 그레인을 동시에 적용하여 실험을 실시하였다. 그 결과 입구부분과 연료 후반부에 집중된 연소현상을 확인하였다. 스월 유동은 스월 유동의 종류에 상관없이 일정한 감소율을 나타낸다. 그리고 연소율 향상은 연료 벽면에서의 회전 유동 강도에 비례한다고 가정 할 수 있다. 따라서 입구부분의 집중된 연소현상을 해소하고 일정한 연소율 향상을 이룰 수 있는 스월 유동 조건에 대해 연구하였다.

• Journal of Energy Engineering
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• v.20 no.4
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• pp.338-345
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• 2011

The swirl flow applied for high efficiency and reduction of emission such as NOx, CO in a gas turbine engine makes recirculation zone by shear layer in the combustion chamber. This recirculation zone influences a decreasing flame temperature and flame length by burned gas recirculation. Also it is able to suppress from instability in lean-premixed flame. In this study, it was found that the swirl flow field was characterized as function of swirl number using PIV measurement in dump combustor. As increasing swirl number, a change of flow field was presented and recirculation zone was shifted in the nozzle exit direction. Also turbulent intensity and turbulent length scale in combustor were decreased in combustion. It has shown reduction of eddies scale with swirl number increasing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.139-146
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• 2021

In hybrid rocket combustion, the oxidizer swirl injection is frequently used to stabilize the combustion as the rotational velocity component affects the boundary layer flow. However, as the swirl strength increases, a problem arises where the combustion performance changes too much. Thus, this study attempts to control the low frequency instability while minimizing the change in combustion performance by adapting attenuated swirl injection with fuel insert used in reference [7]. To this end, a series of experimental tests were performed by varying swirl intensity and the location of the fuel insert. In the tests, the occurrence of combustion instability and combustion performance were closely monitored. The results confirmed that combustion instability was successfully suppressed at the condition of the swirl angle 6 degree and the location of fuel insert 310 mm. And, the changes in combustion pressure, O/F ratio, and fuel regression rate were found as minimal compared to the baseline case. Also the results reconfirmed that the formation of positive coupling between two high frequency oscillations in 500 Hz band, combustion pressure(p') and heat release oscillation(q'), is the necessary and sufficient condition of the occurrence of low frequency instability.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.377-380
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• 2007

Large Eddy Simulation has been conducted to investigate both stable and unstable flame structures in a swirl turbulent combustor. While a flame is stabilized with periodic dynamic structure at 600K, a slight increase in the flame temperature of inlet mixture, 660K, lead to bifurcation of flame at swirl angle 45 degrees. It was observed that both swirl number and mixture temperature affect a flame bifurcation and the former is a major parameter. One major mechanism contributing to the unstable flame is that the local flame speed overshadows the local flow velocity near the wall of the combustor.

• Journal of Energy Engineering
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• v.14 no.3 s.43
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• pp.180-186
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• 2005

As an engine has a wide range of RPM $(3000\~12000\;RPM)$, variable control system is necessary in order to increase engine performance. SCV has been frequently referred to as a possible way to increase engine performance at low RPM. The purpose of this study is to investigate on the influence of SCV, specially at the range of lower revolution, in a high-speed small engine. Experiments were conducted on 4 Valves SOHC/air-cooling single cylinder engine and SCV shapes have been tested fur swirl intensity, the performance of power, fuel consumption and emission. As a result, we find to use SCV range be below 5000 RPM which fuel consumption decreased $9\%$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.236-241
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• 2009

To identify turbulent flow characteristics of non-reacting case resulted from cooling flow injection in a rectangular swirl combustor, 3D Large Eddy Simulation(LES) was implemented and Proper Orthogonal Decomposition(POD) analysis was used for post-processing. The combustor of concern is the LM6000, lean premixed dry low-NOx annular combustor, developed by GEAE. It was observed that increase in speed of shear layer resulted from the inflow of cooling flow caused intensified vorticity magnitude in central toroidal recirculation zone. In the case of vorticity magnitude in corner recirculation zone, however, was weakened. In addition, pressure fluctuation in combustor was damped down and longitudinal acoustic mode was significantly dissipated