• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집B
• /
• pp.328-334
• /
• 2000

The hybrid catalytic(catalytic+thermal) combustor of a lean methane-air mixture on platinum catalyst was investigated numerically using a 2-D boundary layer model with detailed homogeneous and heterogeneous chemistries. For the more accurate calculations, the actual surface site density of monolith coated with platinum was decided by the comparison with experimental data. It was found that the homogeneous reactions in the monolith had little effect on the change of temperature profile, methane conversion rate and light off location. However, the radicals such as OH and CO were produced rapidly at exit by homogeneous reactions. Thus the homogeneous reactions were important to predict the productions of CO and NOx exactly. In thermal combustor, the production of $N_2O$ was more dominant than that of NO due to the relative important of the reaction $N_2+O(+M){\to}N_2O(+M)$. Finally the production of CO and NOx by amount of methane addition were studied.

• 한국연소학회지
• /
• 제11권2호
• /
• pp.15-21
• /
• 2006

Characteristics of a plasma reactor for partial oxidation of methane, especially focused on the role and effectiveness of plasma chemistry, are investigated. Partial oxidation of methane is investigated using a rotating arc which is a three dimensional version of a typical gliding arc. Three different modes of operation were found. Each mode shows different reforming performance. The reason for the difference is due to the difference in relative role of thermal and plasma chemistry in overall process. A mode with high temperature results higher methane conversion and hydrogen selectivity in contrast to the mode with lower temperature where poor methane conversion and higher selectivity of $C_2$ species are observed. In this way, we can confirm that by controlling characteristic of process or controlling relative strength of plasma chemistry and thermal chemistry, it is possible to map an optimal condition of reforming process by rotating arc.

• 한국자동차공학회논문집
• /
• 제12권5호
• /
• pp.58-65
• /
• 2004

A cylindrical constant volume combustion chamber was used to investigate the combustion characteristics of stratified methane-air mixture under several initial charge conditions in the author's previous reports. The results showed that the improvement of thermal efficiency and reduction of heat loss was realized simultaneously by using 2-stage injection method. This paper deals with the reason why the stratified combustion has showed better combustion rate through the measurement and analysis of chemiluminescence of C $H^{*}$ and $C_{2}$$^{*}$ radicals. An optic fiber bundle is used to measure the local emission of C $H^{*}$ and $C_{2}$$^{*}$ radicals to map the relationship between the excess air ratio and local radical intensity ratio in the combustion vessel at 5 mm apart form the geometric center. The results show that there exist a relationship between the intensity ratio and the air-fuel ratio. It is revealed that the improvement of combustion rate in a lean-stratified mixture is realized through the 2-stage injection method. method.

• International Journal of Automotive Technology
• /
• 제6권4호
• /
• pp.323-332
• /
• 2005

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of a homogeneous charged methane-air mixture under various overall charge pressures, excess air ratios and ignition times. The flow characteristics, including the mean velocity and turbulence intensity, were analyzed with a hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer, a flame propagation image acquired by ICCD camera and exhaust emissions measured by 2-valve gas chromatography were used to investigate effects of initial pressures, excess air ratios and ignition times on the combustion characteristics. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to a near-zero value after 3000 ms and that the combustion duration was shorten and the flame speed and laminar burning velocity had the highest value under the condition of an excess air ratio of 1.1, an overall charge pressure of 0.15 MPa and an ignition time of 300 ms in the present study. The $CO_2$ concentration was proportional to the ignition time and overall charge pressure, the $CO_2$ concentration was proportional to the excess air ratio, and the UHC concentration was inversely proportional to the ignition time and overall charge pressure.

• 한국추진공학회지
• /
• 제25권6호
• /
• pp.45-52
• /
• 2021

본 연구에서는 액체 추진제 소형로켓엔진의 개발을 위한 선행연구로 연료과농 조건의 기체메탄-기체산소 연소시험 결과를 제시한다. 다양한 당량비에 대한 연소특성을 비교하기 위해 산소 공급 유량을 12 g/s로 설정하고 메탄 공급 유량을 변화시켰다. 시험 결과, 연소시험 중 형성되는 정상상태 특성속도가 후반에서 급작스럽게 증가하는 현상이 관측되었으며, 그 변화량은 당량비에 비례하여 커지는 경향을 확인할 수 있었다. 이를 바탕으로 특성속도의 변이특성에 종속하는 당량비 구간을 총 3가지 연소 범주로 구분하였다.

• 한국가스학회지
• /
• 제5권3호
• /
• pp.55-62
• /
• 2001

이 논문에서는 일정한 온도를 유지할 수 있는 자켓타입의 교반 반응기내에서 인공적으로 메탄 하이드레이트를 제조하였으며, 제조시의 하이드레이트의 형상 변화를 관찰하였다. 제조된 하이드레이트의 연소 시연에서는 하이드레이트로 천연가스의 수송 및 저장 가능성을 나타내고 있다. 또한 메탄 하이드레이트 제조시 제조 조건들, 반응기의 온도, 압력 및 교반속도 등의 영향에 대하여 측정하였다. 이러한 제조 조건에 따라 하이드레이트의 생성 속도 및 유도시간을 관찰하였다. 특히 하이드레이트의 성장 즉 핵의 생성과 하이드레이트의 구조 형성에 커다란 영향을 주는 것은 인자들 중에 온도와 압력으로 가스 하이드레이트에 관한 가스의 저장과 수송측면을 알아 볼 경우에 필히 검토해야 할 부분으로 판단된다.

• 한국수소및신에너지학회논문집
• /
• 제17권1호
• /
• pp.75-81
• /
• 2006

Lean premixed combustion is a well known method for low $NO_x$ gas turbine combustor. But lean combustion is usually accompanied by flame instability. To overcome this problem, the hydrogen ($H_2$) was added to main fuel methane to increase flammable limit. In this paper, the effects of hydrogen addition on lean premixed combustion of methane ($CH_4$) were investigated numerically. Results showed that the extinction stretch rate increases and the extinction temperature constant with relatively small amount of $H_2$ addition. The flame temperature and NO emission increase with $H_2$ addition at the same stretch rate and equivalence ratio but it could increase the range of lean extinction and extinction equivalence ratio limit. Eventually, the $H_2$ addition case showed almost same or lower NO emission than no addictive $CH_4$ case in the extinction condition.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.3270-3275
• /
• 2007

DME (Dimethyl Ether, $CH_3OCH_3$) has highly attracted attention as an alternative fuel for transportation, power generation and LPG substitute owing to its easy transportation and cleanliness. This study was conducted to verify the combustion performance and to identify potential problems when DME is fuelled to a gas turbine. GE7EA gas turbine of Pyong-Tak power plant was selected as a target to apply the DME. Combustion tests were conducted by comparing DME with methane, which is a major component of natural gas, in terms of combustion instability, $NO_X$ and CO emissions, and the outlet temperature of the combustion chamber. The results of the performance tests show that DME is very clean but has a low combustion efficiency in low load condition. From the results of the fuel nozzle temperature we have ascertained that DME is easy to flash back, and this property should be considered when operating a gas turbine and retrofitting a burner.

• 에너지공학
• /
• 제13권4호
• /
• pp.311-318
• /
• 2004

본 연구에서는 정적연소실을 이용하여 차량용 대체연료로써 메란 및 수소첨가 메탄의 연소특성을 수소첨가율, 점화위치 및 점화방법에 따라 고찰하였다. 그 결과, 중심점화이고 수소를 첨가하지 많은 순수 메탄의 화염전파과정은 타원형으로 전파하나 수소첨가율이 증가함에 따라 화염면상에 매우 규칙적인 세포구조를 가진 불안정한 타원형화염으로 천이되었고 연소속도도 증가하였다. 또한, 벽면 및 0.5R 점화이고 수소를 첨가하지 않은 순수 메탄의 화염전파과정은 불안정한 타원형으로 전파하고 있었지만, 수소첨가율이 증가함에 따라 연소중기에 불안정한 타원형에서 평면형으로 천이 됐다가 연소말기에는 화염면 선단이 움푹 패인 매우 불규칙한 세포구조를 갖는 패기형으로 변화되었으며 연소속도도 증가하였다 한편, 세 가지 점화위치 모두에 있어서 MSCDI와 CDI사용에 따른 화염전파형태는 외견상 큰 차이는 없었지만, 동일시간에 MSCDI장치의 화염면적은 CDI의 화염면적보다 약간 더 크게 나타났다.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
• /
• pp.153-156
• /
• 2014

This study was aimed to assess combustion stability for coaxial swirl injector and FOOF impinging injector which would be candidates in liquid rocket engine combustors. Simulating combustion tests under atmospheric condition have been conducted by gaseous oxygen and the mixture of methane and propane, using two actual injectors. By analyzing the measured dynamic pressure signals, we have evaluated the combustion stability margin of both injectors by drawing a stability map.