• 대한기계학회논문집B
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• 제31권4호
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• pp.384-391
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• 2007

Hydrogen-blending effects in flame structure and NO emission behavior are numerically studied with detailed chemistry in methane-air counterflow diffusion flames. The composition of fuel is systematically changed from pure methane to the blending fuel of methane-hydrogen through $H_2$ molar addition up to 30%. Flame structure, which can be described representatively as a fuel consumption layer and a $H_2$-CO consumption layer, is shown to be changed considerably in hydrogen-blending methane flames, compared to pure methane flames. The differences are displayed through maximum flame temperature, the overlap of fuel and oxygen, and the behaviors of the production rates of major species. Hydrogen-blending into hydrocarbon fuel can be a promising technology to reduce both the CO and $CO_2$ emissions supposing that NOx emission should be reduced through some technologies in industrial burners. These drastic changes of flame structure affect NO emission behavior considerably. The changes of thermal NO and prompt NO are also provided according to hydrogen-blending. Importantly contributing reaction steps to prompt NO are addressed in pure methane and hydrogen-blending methane flames.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.171-181
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• 2007

Blending effects of hydrogen and water vapor on flame structure and NOx emission behavior are numerically studied with detailed chemistry in methane-air counterflow diffusion flames. The composition of fuel is systematically changed from pure methane and pure hydrogen to the blending fuels of methane-hydrogen-water vapor through the molar addition of $H_2O$. Flame structure is changed considerably for hydrogen-blending methane flames and hydrogen-blending methane flames diluted with water vapor in comparison to pure methane flame. These complicated changes of flame structures also affect NOx emission behavior considerably. The changes of thermal NO and Fenimore NO are analyzed for various combinations of the fuel composition. Importantly contributing reaction steps to thermal NO and Fenimore NO are addressed in pure methane, hydrogen-blending methane flames, and hydrogen-blending methane flames diluted with water vapor.

• Transactions on Electrical and Electronic Materials
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• 제13권2호
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• pp.106-109
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• 2012

A low power methane gas sensor with microheater was fabricated by silicon bulk micromachining technology. In order to heat up the sensing layer to operating temperature, a platinum (Pt) micro heater was embedded in the gas sensor. The line width and gap of the microheater was 20 ${\mu}m$ and 4.5 ${\mu}m$, respectively. Zinc oxide (ZnO) nanowhisker arrays were grown on a sensor from a ZnO seed layer using a hydrothermal method. A 200 ml aqueous solution of 0.1 mol zinc nitrate hexahydrate, 0.1 mol hexamethylenetetramine, and 0.02 mol polyethylenimine was used for growing ZnO nanowhiskers. Temperature distribution of the sensor was analyzed by infrared thermal camera. The optimum temperature for highest sensitivity was found to be $250^{\circ}C$ although relatively high (64%) sensitivity was obtained even at as low a temperature as $150^{\circ}C$. The power consumption was 72 mW at $250^{\circ}C$, and only 25 mW at $150^{\circ}C$.

• 한국습지학회지
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• 제21권2호
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• pp.95-101
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• 2019

식생이 없는 갯벌에서 메탄($CH_4$) 플럭스는 배출과 흡수 양상을 보인다. 특히 메탄영양세균 개체군은 메탄 흡수에 상당한 영향을 준다. 본 예비연구는 거대 무척추 동물의 서식활동(bioturbation) 영향을 이해하기 위해 원형 밀폐 챔버 방법을 사용하여 갯벌에서 메탄 플럭스를 조사하였다. 챔버는 십각목(decapoda)의 mud shrimp(Laomedia astacina)와 crab(Macrophthalmus japonicas) 서식굴에 약 2시간 동안 배치되었고, 메탄과 이산화탄소($CO_2$) 농도는 밀폐된 $CH_4/CO_2$ 확산 플럭스 관측 장비를 사용하여 지속적으로 모니터링 되었다. 서식굴 길이가 긴 Laomedia astacina 위치에서는 깊은 퇴적층의 메탄 방출 때문에 상대적인 높은 수준의 메탄 발생을 일으킨 것으로 나타났다. 또한, 서식굴 퇴적물에서 발견되는 메탄영양세균 개체군은 메탄 산화(oxidation) 잠재력을 나타냈다. 특히 서식굴 내 아질산염 관련 혐기성 산화(anaerobic oxidation of methane, AOM)가 확인되었다. 이러한 메탄 산화 발생은 챔버 실험 동안 이산화탄소의 탄소 안정동위원소비(${\delta}^{13}C$) 감소로 뒷받침되었다. 따라서 갯벌에서 무척추 동물의 서식활동은 대기 중 메탄 농도를 제어할 수 있는 중요한 생태계 환경으로 보인다.

• 센서학회지
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• 제5권1호
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• pp.23-29
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• 1996

본 연구에서는 스크린 프린팅 기술을 이용한 병렬저항열원을 갖는 후막형 가연성 가스센서를 제조하고, 메탄 가스에 대한 감도특성을 조사하였다. 알루미나 기판의 양면 위에 제조된 병렬형 백금 후막발열체는 후막형백금 저항체의 온도 감지 특성과 표면 특성을 조사하여 백금페이스트 TR7905 제품을 선정하였다. 제조된 백금 후막 발열체는 평균저항같이 $1.8{\Omega}$이고, TCR값은 $3685\;ppm/^{\circ}C$이었다. 제조된 백금 발열체상에 Pt과 Pd이 첨가된 촉매 페이스트를 제조하고 감지부는 Pt과 Pd가 첨가된 촉매를 스크린 프린팅하여 후막을 형성하고 열처리하여 제조하였다. 제조된 후막형 센서는 메탄 가스에 대해 4.3mV/1000ppm의 감도를 보였으며, 소비전력은 2.12W이었다.

• 한국지열·수열에너지학회논문집
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• 제18권4호
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• pp.12-21
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• 2022

Steam assisted gravity drainage(SAGD) is a process that drills well in the underground oil sands layer, injects hightemperature steam, lowers the viscosity of buried bitumen, and recovers it to the ground. Recently, direct contact steam generator(DCSG) is being developed to maximize steam efficiency for SAGD process. The DCSG requires high technology to achieve pressurized combustion and steam generation in accordance with underground pressurized conditions. Therefore, it is necessary to develop a combustion technology that can control the heat load and exhaust gas composition. In this study, process analysis of high-pressurized DCSG was conducted to apply oxygen enrichment technology in which nitrogen of the air was partially removed for increasing steam production and reducing fuel consumption. As the process analysis conditions, methane as the fuel and normal air or oxygen enriched air as the oxidizing agent were applied to high-pressurized DCSG process model. A simple combustion reaction program was used to calculate the property variations for combustion temperature, steam ratio and residual heat in exhaust gas. As a major results, the steam production efficiency of DCSG using the pure oxygen was about 6% higher than that of the normal air due to the reducing nitrogen in the air. The results of this study will be used as operating data to test the demonstration device.