• 한국추진공학회지
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• 제27권1호
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• pp.27-36
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• 2023

소형로켓엔진에 적용되는 기체-액체 스월 동축형 인젝터의 분무성능을 파악하고자 형상변수와 추진제의 공급조건을 변화시켜 수류시험을 수행하였다. 인젝터의 형상변수인 스월 챔버의 직경 및 수축부의 각이 증가할수록 스월 강도가 증대되어 분무성능이 향상되었다. 또한, 기체-액체의 운동량 플럭스 비가 증가함에 따라 기체 유동이 액적 일부를 분무액막에서 이탈시켜, 분무시트의 중심부에서 gas-droplet mixture core가 형성되었다.

• 한국자기학회지
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• 제12권6호
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• pp.218-223
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• 2002

가슨 분무법으로 제조한 High-Flux형 $Ni_{x}Fe_{100-x}$(x=40~50, wt.%) 퍼멀로이 분말 및 압분 코아의 자기적 특성을 조사하였다. 포화자화는 45%Ni조성에서 최대 값을 보이며 이보다 보 함량이 낮아지면 인바 효과의 작용에 의해 급격하게 감소하였다. 압분 코아의 투자율은 Ni 농도가 낮아지면 현저히 증가하는 바 이는 자기변형의 감소에 기인하는 것으로 사료되었으며, 자심손실은 Ni=45%에서 가장 낮은 값을 나타내었다. Ni농도가 50%에서 45%로 낮아짐에 따라 자심손실이 감소하는 주원인은 전기 비저항의 증대에 따른 와전류 손실의 감소에 있는 것으로 생각되었다. Ni=45% 분말 합금으로 만든 압분 코아는 Ni=50%의 경우보다 더 우수한 투자율의 주파수 의존성, 큰 Q 값, 그리고 더 나은 직류 바이어스 특성을 나타내어 상용 High-Flux 코아(50%Ni-50%Fe)에 비해 더 좋은 압분 자심 재료가 될 수 있음을 확인하였다.

• 한국분무공학회지
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• 제27권3호
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• pp.134-143
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• 2022

When a recess is applied to a swirl coaxial injector that uses liquid and gas propellants, a self-pulsation phenomenon in which the spray oscillates at regular intervals may occur. The phenomenon is caused by the interaction between the liquid and gas propellants inside the injector recess region. The propellants' kinetic energies are expected to affect significantly the spray oscillation. Therefore, cold-flow tests using helium as a gas-simulating propellant were conducted and compared with the results of the previous study using air. Dynamic pressure was measured in the injector manifold and frequency characteristics were investigated through the fast Fourier transform analysis. In the experimental environment, the helium density was about seven times lower than the air density. Accordingly, the intensity of pressure fluctuations was confirmed to be greater when air was used. At the same kinetic energy condition, the perturbation frequency was almost identical in the low flow rate conditions. However, as the flow rate increased, the self-pulsation frequency was higher when helium was used.

• 한국분말재료학회지
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• 제9권5호
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• pp.303-306
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• 2002

P/M high speed steels with various Co contents were fabricated by gas atomization and Canning/HIP process. As Co content in P/M high speed steel increased, hardness, transverse rupture strength and yield strength in compressive testing increased due to solid solution hardening of Co in matrix. Especially, PM high speed steels with Co have high deformation resistance to repeated compressive loading.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.100-103
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• 1998

In this study, Al-Ni-Mm alloy has been produced by a gas atomization technique and consolidated by a powder extrusion method. The powders showed mixed structures of amorphous, fcc-Al phases and intermetallics. Each phase shows different size and quantity with different size of the powders due to the higher cooling rate of the finer powders. Because of the difference of the microstructure, the powders with the different size show differences of the mechanical properites of the powders and extrudates.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.860-865
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• 2012

바이오매스 합성가스는 저열량 가스이지만 유류를 대체하기 위한 목적으로 공업로, 보일러 등에서 혼소방법으로 이용되고 있다. 혼소버너의 기본구조는 오일버너를 중심부로 하고 저열량 가스 연료를 그 주위로 공급하는 형태로 설계되었다. 본 연구에서는 가스의 균일분산 방법과 가스노즐 각도를 변화시키는 방법을 적용하여 세 종류의 버너를 설계하였다. 연소공기량 증가에 따라 CO 발생량이 감소하였으며, 혼소조건에서 화염으로부터 잔염 발생 원인은 오일버너로부터 미립화 불량인 것으로 나타났다. 혼소조건에서는 가스와 오일연료에 대한 과잉공기 요구량이 서로 다르기 때문에 적절하게 연소공기량을 맞추기가 어려웠지만, 과잉산소 4.7~8.2% 범위에서 안정적인 연소조건 유지가 가능하였다. 본 연구를 통하여 합성가스와 유류의 혼소 이용은 합성가스 성분이 오일보다 연소속도가 빠르게 이루어져 오일버너 미립화를 촉진시켜주고, 오일 단독연소조건보다 CO 배출 농도를 낮게 유지할 수 있음을 알 수 있었다.

• 한국항공우주학회지
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• 제44권4호
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• pp.290-297
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• 2016

사각덕트에서 난류 유동장으로 분사되는 액체 제트의 액주 분열과 미립화 현상에 관한 LES를 수행하였다. 기체상태의 공기 유동 해석에 오일러리안 해법을 사용하고, 액적 추적을 위하여 라그랑지안 해법을 사용하여 기체-액체간 이상유동(two phase flow) 해석을 수행하였다. 액적 분열 모델, 아격자 스케일 모델 및 공간 차분법에 따른 액적 분열을 조사하였다. 액체 제트의 침투깊이를 경험식과 비교하였으며 경험식보다 약간 높음을 알 수 있었다. 제트 후류에서 사우터 평균직경에 대한 분석을 수행하였다.

• 한국분무공학회지
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• 제25권3호
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• pp.132-138
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• 2020

N₂O is hazardous atmosphere pollution matter which can damage the ozone layer and cause green house effect. There are many other nitrogen oxide emission control but N₂O has no its particular method. Preventing further environmental pollution and global warming, it is essential to control N₂O emission from industrial machines. In this study, the thermal decomposition experiment of N₂O gas mixture is conducted by using cylindrical reactor to figure out N₂O reduction and NO formation. And CHEMKIN calculation is conducted to figure out reaction rate and mechanism. Residence time of the N₂O gas in the reactor is set as experimental variable to imitate real SNCR system. As a result, most of the nitrogen components are converted into N2. Reaction rate of the N₂O gas decreases with N₂O emitted concentration. At 800℃ and 900℃, N₂O reduction variance and NO concentration are increased with residence time and temperature. However, at 1000℃, N₂O reduction variance and NO concentration are deceased in 40s due to forward reaction rate diminished and reverse reaction rate appeared.

• 한국분무공학회지
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• 제23권3호
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• pp.128-135
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• 2018

In this study, the following conclusions could be obtained from the analysis of emissions contribution rates and features for contaminated emissions by 13,456 gasoline vehicles passed in the vehicle load test (ASM-idle) under the inspection year 2013 to 2017. It was confirmed that the contamination of the CO, HC, NOx by the displacement is reduced on over 3L engine. As a result of comparing the exhaust gas in the low speed idle mode and the AS2525 mode, the exhaust gas in the low speed idle mode was measured high. It is estimated that if ISG function is applied, emissions from idle condition will be reduced. NOx emissions were reduced when the engine power was above 200HP. It has been confirmed that the amount of exhaust emissions are significantly reduced for vehicles manufactured after 2004. As a result of analyzing the exhaust gas according to the season, it is judged that there is a correlation between HC and NOx according to the ambient temperature. The concentration of exhaust emission in vehicles with high accumulated distance increases, which is considered to be the result of aging of the vehicle.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2721-2730
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• 1996

The present study conducted experimental study of spray combustion to investigate the effect of the inlet conditions of fuel and air on the flame structure, the flame stability and the characteristics of emission in the can-type model of a gas turbine combustor. In the experiment, the diameter of fuel droplet was measured using Malvern particle size analyser and temperatures in the combustion chamber were measured with R-type shielded thermocouple. In addition, flame structure was taken picture with camera and analysed. Gas analyser was also used to analyse the concentration of each components of exhausting gas. The experimental results showed that the flame condition was optimal with swirl number, 0.63 and equivalence ratio, 0.5 for controlling the flame stability, the combustion temperature and the NOx concentration. The present study concluded that both the flame structure and the emission formation were strongly affected by the swirl intensity, which selection was found as an important parameter for either stabilizing flame or lowering the quantity of NOx.