• 한국추진공학회지
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• 제26권1호
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• pp.12-19
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• 2022

덕티드 로켓의 가스발생기에 사용되는 추진제는 연료과농 추진제로서, 일반적인 고체 로켓 추진제에 비하여 과량의 금속연료와 소량의 산화제를 포함한다. 본 논문에서는 연료과농 추진제를 제조하기 위하여 보론 분말과 MgAl(Magnesium-Aluminium Alloy)를 적용하였다. 이 금속연료를 적용한 추진제의 특성을 분석하였고, 이를 통하여 최적의 조성을 연구하였다. 추진제의 연소생성물 분석을 통하여 보론 비드가 아닌 미립의 보론 분말로도 가스발생기용 연료과농 추진제가 가능함을 확인하였다.

• 한국연소학회지
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• 제11권1호
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• pp.19-26
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• 2006

Structure of edge flame established in a mixing layer, formed between two uniformly flowing pure $CH_4$ and pure $O_2$ streams, is numerically investigated by employing a detailed methane-oxidation mechanism. The numerical results exhibited the most outstanding distinction of using pure oxygen in the fuel-rich premixed-flame front, through which the carbon-containing compound is found to leak mainly in the form of CO instead of HC compounds, contrary to the rich $CH_4-air$ premixed flames in which $CH_4$ as well as $C_2H_m$ leakage can occur. Moreover, while passing through the rich premixed flame, a major route for CO production, in addition to the direct $CH_4$ decomposition, is found to be $C_2H_m$ compound formation followed by their decomposition into CO. Beyond the rich premixed flame front, CO is further oxidized into $CO_2$ in a broad diffusion-flame-like reaction zone located around moderately fuel-rich side of the stoichiometric mixture by the OH radical from the fuel-lean premixed-flame front. Since the secondary CO production through $C_2H_m$ decomposition has a relatively strong reaction intensity, an additional heat-release branch appears and the resulting heat-release profile can no longer be seen as a tribrachial structure.

• 한국연소학회지
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• 제20권1호
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• pp.32-42
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• 2015

The combustion instability was experimentally investigated in model gas turbine combustor with dual swirl burner. When such instability occurs, a strong coupling between pressure oscillation and unsteady heat release excites a self-sustained acoustic wave which results in a loud sound, and can even cause fatal damage to the combustor and entire system. In present study, to understand the combustion instability with a premixed mixture, the detailed periods of pressure and heat release data in unstable flame mode were investigated by various measurement methods at relatively rich condition and lean condition near flammable limits. Also, to prepare the utilization of synthetic natural gas (SNG) fuel in gas turbine system, an investigation was conducted using a simulated SNG including methane as a reference fuel to examine the effects of $H_2$ content on flame stability. These results provide that the instability due to flash-back behaviour like CIVB phenomenon occurred at rich condition, while the repetition of relighting and extinction caused the oscillation of lean condition near flammable limit. From the analysis of $H_2$ content effects, it is also confirmed that the instability frequency is proportional to the laminar burning velocity at both rich and lean condition.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.19-24
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• 2002

Recent studies of a triple flame suggested that the presence of triple point (triple line in this planar configuration) could explain the mechanisms of stable fuel-lean premixed flames with equivalence ratio lower than the flammability limit. In the present study, for better understanding of the stability mechanisms of fuel rich-lean premixed flames, the fuel-rich flames were replaced with hot coils that will provide heat flux into the fuel-lean flames. It is found that the fuel-lean premixed flames could be stabilized without any triple point (triple line): however, the equivalence ratio limit for stable fuel-lean flame in this case is higher than that of the present work with the presence of fuel-rich flames. These results demonstrate that heat flux coming from fuel-rich flames should be considered in order to properly understand the roll of a triple flame for stable fuel rich-lean flames.

• Journal of Advanced Marine Engineering and Technology
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• 제26권1호
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• pp.37-47
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• 2002

Recently gasoline direct injection method has been applied to gasoline engine to reduce fuel consumption rate by controlling fuel air mixture on lean condition by means of stratified charging, and to reduce simultaneously. Pollutant emissions especially NOx and CO by lowering the combustion temperature. But difficulty of controling local fuel air ratio at ignition area in flammability limit unavoidably appeared, because it is merely controlled by injection timing with spatial and temporal distribution of fuel mixture. In this study, the authors devised a uniquely shaped combustion chamber so called three-chamber GDI engine, intended to keep the more reliable fuel air ratio at ignition area. The combustion chamber is divided into three regions. The first region is in the rich combustion division, where the fuel is injected from the fuel injection valve and ignited by the spark plug. The second region is in the lean combustion division, where the combustion gas from the rich combustion division flows out and burns on lean condition. And the last region is in the main combustion division ie in the cylinder, where the gas from the above two combustion divisions mixed together and completes the combustion during expansion stroke. They found that the stable range of operation of three-chamber GDI engine on low-load condition exists in the lean area of average equivalence ratio. And they also found that the reformed engine reveals less specific fuel consumption and less pollutant emissions compared with conventional carburettor type gasoline engine.

• 한국연소학회지
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• 제4권2호
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• pp.63-74
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• 1999

The effects of EGR and premixedness on NO formation have been numerically investigated. The flame structure is classified into three categories; premixed flame($=1)$, rich/lean premixed flame(${\alpha}=0.6$ and 0.8) and diffusion flame(${\alpha}=0$). NO formation/destruction mechanisms are assorted to thermal, reburn and Fenimore mechanisms. The temperature of unburned gas is arranged to 298 and 500 K to have access to the condition in a real internal combustion engine. The results show that all three NO formation/destruction reaction rates in the fuel rich flame zone could be decreased by EGR for rich/lean premixed flames, while those in the fuel lean flame zone are not significantly changed. Near the stagnation plane, however, only the thermal NO reaction rate is decreased. The contribution of reburn and Fenimore mechanisms for the net NO production becomes less significant as the premixedness of a flame increases. The larger amount of NO reduction with EGR is expected under the higher temperature and/or higher fuel/air premixedness conditions due to the increased contribution of the thermal mechanism. The role of Fenimore and reburn mechanisms could be important for rich premixed and diffusion flames; therefore, the effect of EGR on NO reduction could vary with fuel/air premixedness. The premixedness of a partially premixed flame changes the flame structure and could affect the NO production characteristics.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.143-147
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• 2007

케로신과 디젤은 단일 구성물이 아닌 여러 가지 탄화수소 연료로 이루어진 혼합연료이며 화학반응 메커니즘에 대한 모델링이 매우 어려운 실정이다. 본 연구에서는 Dagaut가 개발한 298 화학종, 2352 화학반응 단계를 이용하였으며 완전혼합반응기 연소모델을 적용하여 농후 연소 비평형 화학 반응을 계산하였다. 또한 Frenklach의 soot 모델을 적용하여 soot 생성 연구를 수행하였으며 Dagaut의 화학반응 모델에 Appel이 제안한 화학 반응 단계를 추가하여 케로신과 디젤 연료에 대한 soot 모사를 가능하게 하였으며 수정된 모델은 간단한 soot 반응 메커니즘을 사용하였음에도 불구하고 soot 생성 예측이 가능하였다.

• 한국항공우주학회지
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• 제34권10호
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• pp.56-60
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• 2006

액체 로켓 엔진용 가스발생기 개발을 위해서는 추진제 O/F ratio에 따른 연소 가스의 열역학적 물성치 예측이 필수적이다. 본 연구에서는 액체산소/Jet A-1 조합의 연료 과농 가스발생기의 실 추진제 연소 시험을 통해 O/F ratio 변화에 따른 연소 생성 가스의 온도를 계측하였다. 또한 연소실 내 동압 섭동 측정 및 정압 측정 결과를 이용하여 비열비, 가스 상수, 정압 비열과 같은 연소 가스의 열역학적 물성치를 간접적으로 산출해내었다. 본 실험값은 화학평형코드 결과를 통해 구한 보간 계수를 이용한 예측 결과와 비교해보았을 때 동일한 경향 및 유사한 값을 가지는 것으로 밝혀졌으며 이는 보간 계수 예측 방법이 설계 도구로 충분히 적용 가능하다는 결과를 확인하였다.

• 한국항공우주학회지
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• 제44권7호
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• pp.576-584
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• 2016

본 연구는 다단 하이브리드 로켓의 낮은 비추력 성능을 향상시키는 방법으로 AP 첨가 추진제를 제안하고 있다. 추진제에 첨가된 AP 첨가비율 변화에 따라 다단 하이브리드 로켓의 비추력 성능 변화와 연료과농 연소특성 변화를 살펴보았으며, 이때 AP 첨가비율은 하이브리드 로켓의 연소 특징을 유지하기 위해 최대 15 wt%로 제한하였다. 결과에 의하면, AP 15 wt% 추진제는 AP 0 wt% 추진제와 비교하여 비추력 성능이 약 3% 향상되었다. 또한, 동일한 연소온도를 유지함에도 불구하고, AP 첨가비율을 증가시키면 산화제 유입량, O/F비 변화량, 그리고 연소압력은 감소하며 반경반향 온도 분포가 좋아지는 등 다단 하이브리드 로켓의 성능향상에 긍정적인 효과가 나타났다. 그러나 오직 AP를 추진제에 첨가하는 것만으로 다단 하이브리드 로켓의 비추력 성능을 일반 화학로켓의 수준으로 향상시키는 것이 매우 어려운 일임을 고려할 때, 추가적으로 금속입자 첨가를 통해 비추력 성능을 향상시킬 계획이다.

• 동력기계공학회지
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• 제7권4호
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• pp.12-18
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• 2003

Various measures have been tried to reduce the NOx emission from diesel engine, but with partial success because the mechanisms of NOx and PM formations appear to have trade-off relation between each other. Therefore it has been known to be difficult to reduce NOx emission and PM emission simultaneously. Two stage combustion method i,e. a combustion process which has rich combustion stage and lean combustion stage one by one, has been developed successfully to reduce NOx formation in the continuous combustion chambers such as in the boilers. But until yet it is not successful to apply the same method in intermittent combustion chamber like in the diesel engine cylinder, as it was, only several research works were carried out. In this study, devised was a uniquely shaped combustion chamber with reformed piston crown intended to keep fuel-rich condition during early stage of combustion and fuel-lean condition during next stage. It was found that the NOx emission decreased significantly at various conditions of operation with the two stage combustion type engines of PR20 type, but other values such as smoke, CO and specific fuel consumption deteriorated as usual.