• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.242-245
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• 2009

The effect of fuel composition on flame length was studied in a non-premixed turbulent diluted hydrogen jet with coaxial air. The observed flame length was expressed as a function of the ratio of coaxial air to fuel jet velocity and compared with a theoretical prediction based on the velocity ratio. Four cases of fuel mixed by volume were determined. In the present study, we derived a scaling correlation for predicting the flame length in a simple jet with coaxial air using the effective jet diameter in the near-field concept. The experimental results showed that visible flame length had a good relation with the theoretical prediction. The scaling analysis is also valid for diluted hydrogen jet flames with varied fuel composition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.208-212
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• 1995

공기 압축기는 건설 및 토목공사 현장 등의 산업현장을 비롯하여 각종 공장에서 광범위하게 사용되고 있다. 공기 압축기에 공급하는 동력은 전기를 사용한 모터와 연료를 사용한 엔진으로 구분할 수 있으며 전기가 공급되지 않는 사용현장에서는 엔진 구동형 공기 압축기가 선택될 수 밖에 없다. 엔진 구동형 공기 압축기는 발생소음도가 모터 구동형보다 훨씬 높음으로 인하여 주변환경에의 소음으로 인한 피해를 줄이기 위하여 방음형의 개발이 절실하게 요구되고 있다. 따라서 본 연구는 기존의 비방음형 공기 압축기에 대하여 방음형을 개발하여 시제품을 제작하고 평가하는데 그 목적이 있다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.41-49
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• 2004

The porous media of a proton exchange membrane fuel cell (PEMFC) is made of deformable materials. The shape of cross sectional area in air plate channels has been changed by structural deformation of the porous media. The uniform mass flow rate and pressure are major factors for safe and efficient operation in the PEMFC. Two kinds of models are provided for the flow analyses. Deformable and undeformable porous media are considered for numerical analysis and experiment of the air plate model. The numerical flow analysis results with deformable and undeformable porous media has some discrepancy in pressure distribution. The pressure differences are measured in order to compare with numerical analysis results. Pressures are measured between inlet and outlet of the air plate. The numerical analysis and experimental results show similar pressure distribution. It is shown that the pressure drops in the two approaches are well matched each other. It is proven that the consideration of structural deformation is required in the numerical analysis/experiment for the PEMFC design.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.05a
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• pp.173-177
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• 2002

두 개의 유동층 사이를 순환하는 금속매체(Metal or Metal oxide)를 이용하여 공기에 의한 금속매체의 산화와 기체연료(H$_2$, CO, CH$_4$등)에 의한 금속산화물의 환원반응이 별개의 반응기에서 일어나게 하는 새로운 개념의 연소기술인 매체순환식 가스연소기술은 공기와 기체연료를 직접 접촉시켜 반응하는 기존의 가스연소기에 비해 많은 장점을 가지고 있다.(중략)

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.106-114
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• 2002

In this study, the air-fuel ratio(A/F) control characteristics of a liquid and a gaseous fueled engine are investigated. Engine models far both the liquid and the gaseous fueled engine are developed to compare the characteristics of fuel delivery into the cylinder, and the performances of the models are evaluated using the simulation and experiment. The simulation and experimental results show that the gaseous fueled engine has better control performance than that of the liquid fueled engine in terms of the air-fuel ratio control. This study could be used to develop air-fuel ratio control schemes for both the liquid and the gaseous fueled engine.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.4
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• pp.9-15
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• 2009

The flow of combustor in scramjet engine has supersonic speed so that the residence time and mixing ratio are very important factors for the efficient combustion. This study used open cavity(L/D=4.8) as a fuel/air mixing model. Laser schlieren visualization and pressure measurement were carried out to observe the flow characteristics around a jet orifice and a cavity at the time of fuel injection. As a result of 10ns laser schlieren, unsteady flow which was around the cavity could be observed effectively. Pressure was measured that momentum flux ratio(J) was changed. And the change of critical ignition point could be observed by the momentum flux ratio changed.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.587-592
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• 2010

A numerical analysis of reactive flow in a MILD(Moderate and Intense Low oxygen Dilution) combustor is accomplished to elucidate the characteristics of combustion phenomena in the furnace with the variation of air fuel ratio. For the smaller magnitude of air injection velocity(10 m/s), the air flow could not penetrate toward upper part of furnace. On the other hand, the air flow suppresses the fuel flow for the case of air injection velocity 30 m/s. The air velocity 18 m/s is corresponding to the stoichiometric air flow velocity, and for that case, the air flows to relatively more upper part of the furnace when compared with the case of air injection velocity 10 m/s. The reaction zone is produced with the previous flow pattern, so that the reaction zone of the air injection velocity 10 m/s is biased to the air nozzle side and for the case of air injection velocity 30 m/s, the reaction zone is inclined to the fuel nozzle side. For the cases with the air injection velocities 16, 18, 20 m/s, the reaction zone is nearly located at the center between air nozzle and fuel nozzle. The maximum temperatures and NOx concentrations for the cases of air injection velocity 16, 18, 20 m/s are lower than the cases with air injection velocity 10, 30 m/s. From the present study, the stoichiometric air fuel ratio is considered as the most optimal operating condition for the NOx reduction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.473-479
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• 2013

This study focused on a heavy-duty natural gas engine fuelled with HCNG (CNG: 70 vol%, hydrogen: 30 vol%) and CNG. To study the emission characteristics of an HCNG engine with high compression ratio, the exhaust gas of CNG and HCNG fuel were analyzed in relation to the change in the compression ratio at the half load condition. The results showed that the thermal efficiency improved with an increase in the compression ratio. Consequently, $CO_2$ emission decreased. CO emission increased with inefficient oxidation due to the low exhaust gas temperature. $NO_x$ emission with high compression ratio was increased at the same excess air ratio condition. However, $NO_x$ emission was not affected by a compression ratio exceeding ${\lambda}$ = 1.9 because of the same MBT timing.

• Journal of the KSME
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• v.28 no.5
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• pp.469-475
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• 1988

연료소비율의 향상은 점차 감소되어 가는 경향에 있다. 그 원인은 3원촉매변환기 채용에 의한 이론공기연료비의 사용, 기관의 연소개선이 발전하여 고압축비화에 의한 연료소비율 향상이 더 이상 어렵게 되었다는 점을 들 수 있다. 한편, 고압축비화의 역효과로는 연소실내 최고압력이 증가하여 각부의 강도나 기관 소음의 문제가 대두된다. 이들 역효과를 타파하여 충분한 연료 소비 향상을 얻을 수 있는 수단이 단기적인 과제가 될 것이다. 전자제어, 희박연소, 마찰저감 등 통상의 엔진의 개량에 대한 노력이 계속될 것이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.76-81
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• 2006

This paper deals with a fuel metering unit (referred to as FMU) for air breathing engine. The proposed FMU consists of a constant pressure drop valve and a metering valve, both of which are controlled by servovalve. Linear analysis derived from a nonlinear mathematical model of FMU is carried out to find major parameters on the system performance. Numerical results using established model of FMU were in good agreement with the experimental results. It is also shown that the system stability is improved by reducing the constant pressure drop at metering valve and applying the triangular orifice to constant-pressure-drop valve through the simulation and experiments.