• 한국분무공학회지
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• 제24권4호
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• pp.171-177
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• 2019

This paper describes numerical study of combustion characteristics in CNG(compressed natural gas) DI(direct injection) engine using gaseous sphere injection model. Simulations were conducted using KIVA-3V Release 2 code. Gaseous sphere injection model, which is modified model of liquid fuel injection, was used to simulate the CNG direct injection. Until now, a very fine mesh smaller than the injector nozzle has been required to resolve the gas-jet inflow boundary. However, the gaseous sphere injection model simulates gaseous fuel injection using a coarse mesh. This model injects gaseous spheres as in liquid fuel injection and the gaseous spheres evaporate together without the latent heat of evaporation. Therefore, it does not require a very fine mesh and reduce calculation time. Combustion simulation were performed under various injection timings and injection pressures.

• 한국수소및신에너지학회논문집
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• 제15권4호
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• pp.348-354
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• 2004

Hydrogen gas has several merits such as lower ignition energy, wide flammability and shorter quenching distance. It leads to high thermal efficiency but backfire occurrence. In this study, feasibility of expansion of BFL(Back-Fire Limit) equivalence ratio and combustion characteristics by a dilution of hydrogen fuel are experimently examined by using experimental heavy duty single cylinder hydrogen fueled engine. As results, it is found that BFL equivalence ratio is expanded to rich range and torque is increased.

• 한국수소및신에너지학회논문집
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• 제28권2호
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• pp.174-180
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• 2017

Recently, the world faces the environmental problem such as air pollution due to harmful gas discharged from car and abnormal climate due to the green-house gases increased by the discharge of $CO_2$. Compressed Natural Gas (CNG), one of alternative for this problem, is less harmful, compared to the existing fossil fuel, as gaseous fuel, and less carbon in fuel ingredients and carbon dioxide generation rate relatively favorable more than the existing fuel. However, CNG fuel has the weakness of slow flame propagation speed and difficult fast burn. On the other hand, hydrogen does not include carbon in fuel ingredients, and does not discharge harmful gas such as CO and HC. Moreover, it has strength of quick burning velocity and ignition is possible with small ignition energy source and it's has wide Lean Flammability Limit. If using this hydrogen with CNG fuel, the characteristics of output and discharge gas is improved by the mixer's burning velocity improved, and, at the same time, is possible to have stable lean combustion with the reduction of $CO_2$ expected. Therefore, this research tries to identify the characteristics of engine and emission gas when mixing CNG fuel and hydrogen in each portion and burning them in spark igniting engine, and grasp the lean combustion limit and emission gas characteristics according and use it as the basic data of hydrogen-CNG premixed engine.

• 한국수소및신에너지학회논문집
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• 제27권4호
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• pp.357-364
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• 2016

Recently, the world faces the environmental problem such as air pollution due to harmful gas discharged from car and abnormal climate due to the green-house gases increased by the discharge of $CO_2$. Compressed Natural Gas (CNG), one of alternative for this problem, is less harmful, compared to the existing fossil fuel, as gaseous fuel, and less carbon in fuel ingredients and carbon dioxide generation rate relatively favorable more than the existing fuel. However, CNG fuel has the weakness of slow flame propagation speed and difficult fast burn. On the other hand, hydrogen does not include carbon in fuel ingredients, and does not discharge harmful gas such as CO and HC. Moreover, it has strength of quick burning velocity and ignition is possible with small ignition energy source and it's has wide Lean Flammability Limit. If using this hydrogen with CNG fuel, the characteristics of output and discharge gas is improved by the mixer's burning velocity improved, and, at the same time, is possible to have stable lean combustion with the reduction of $CO_2$ expected. Therefore, this research tries to identify the characteristics of engine and emission gas when mixing CNG fuel and hydrogen in each portion and burning them in spark igniting engine, and grasp the combustion stability and emission gas characteristics according and use it as the basic data of hydrogen-CNG premixed engine.

• 한국가스학회지
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• 제19권5호
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• pp.7-12
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• 2015

현재까지 수소는 주로 천연가스의 연료 개질에 의해 발생된 합성가스를 이용해 생산된다. 합성가스 내의 수소 수율을 높이기 위해선 추가적인 공정이 필요하다. 하지만, 수소의 수율 향상을 위한 공정에는 별도의 에너지원과 경제적 비용이 수반된다. 그러므로 보다 효율적으로 합성가스를 활용하기 위해 그 자체로 혼합물로 이용하는 방법에 관한 관련 연구들이 이루어지고 있다. 본 연구에서는 30kW급 발전용 스파크 점화 가스엔진에서 메탄/합성가스 혼합물이 엔진의 주요 성능에 미치는 영향을 조사하였다. 그 결과 메탄/합성가스 혼합물에 의해서 최대 실린더 내부 압력과 그 때의 크랭크 각도와 같은 엔진 내 연소 현상은 개선되는 것으로 나타났다. 이를 통해 메탄-합성가스 혼합물의 연료 전환 효율은 메탄-수소 혼합물의 약 98% 수준으로 향상시킬 수 있고 질소산화물 배출량은 메탄-수소 혼합물의 약 12%만큼 감소시킬 수 있다.

• 대한기계학회논문집B
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• 제37권5호
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• pp.473-479
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• 2013

본 연구에서는 천연가스 70%, 수소 30%의 조성비를 가진 HCNG연료와 천연가스를 각각 대형천연가스엔진에 공급하여 실험을 수행하였다. 고압축비의 수소-천연가스(HCNG)엔진의 배기특성을 살펴보기 위하여 부분부하조건에서 공기과잉률 변화에 따른 각 연료의 배출가스를 분석하였다. 실험결과 압축비가 증가함에 따라 열효율이 향상되었으며 그로인해 $CO_2$ 배출량은 감소하였다. 낮은 배기가스온도에 의하여 산화가 활발히 이루어지 못해 CO의 배출량이 증가하였다. 동일한 공기과잉률에서 압축비가 증가하면 $NO_x$의 배출량이 증가하였다. 하지만 ${\lambda}$=1.9이상의 영역에서는 MBT 점화시기가 동일해지기 때문에 압축비의 영향을 받지 않았다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2011년도 전기공동학술대회 논문집
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• pp.7-10
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• 2011

According to the requirement of Res.MSC.285(86) for natural gas-fueled engine installations in ships, pump and compressor rooms should be fitted with effective mechanical ventilation system of the under pressure type, providing a ventilation capacity of at least 30 air changes per hour. It generally considered that gas leakage is more likely from a Fueled Gas Supply System(FGS) room as compared to other places, where installed in many kind of machinery or equipments like gas supply high-pressure pipes, valves, flanges and etc. Furthermore, leaked gas may be dispersed in a short time in an enclosed space, especially a FGS room, due to high pressure. However, the present requirement in Res.MSC.285(86) just considers the ventilating capacity of air changes per hour but the capacity of leaked gas. Hence, the current requirements may not meet effectively when enforcing the new propulsion systems as marine fuel. This study is conducted for the purpose of safety evaluation about the dispersion and ventilation efficiency with estimated leakage scenario. Numerical analysis predictions as the result of this paper are explained to know the features of flow pattern and the diffusion of natural gas concentration.

• 한국수소및신에너지학회논문집
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• 제26권2호
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• pp.89-95
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• 2015

Pollution emission control of the 20th century, for transportation energy, are being enhanced, and then as alternative to this, because hydrogen emit only water gas emissions to be environmentally friendly energy, so hydrogen as a sustainable clean energy is in the limelight. Used in compressed natural gas engines to mix hydrogen and natural gas in both domestic and international technology development and demonstration is being carried out. The hydrogen-compressed natural gas(HCNG) charging infrastructure can be used to build a hydrogen infrastructure in the transitional aspects of a future hydrogen economy society. In this paper, for a demonstration of HCNG charging infrastructure we made and operated a $30Nm^3/h$ hydrogen generating unit and analyzed the result of the operation. We was identified the operating conditions of a reforming reactor and water gas shift reactor from an analysis result, the thermal efficiency was calculated according to the operating conditions of the total hydrogen production process.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.940-945
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• 2005

In recent years, the LNGC fleet is expanded unprecedentedly. Ship's owners and shipbuilders are focusing on technology and reliability of new propulsion system from economical, environmental and safety angles. This paper give describes the new trend of propulsion system and boil off gas handling system from LNG carriers.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.421-428
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• 2007

This paper investigates the combustion and emission characteristics of a compression ignition engine fueled with neat and blended Shell's gas-to-liquid (GTL) fuel, which was derived from natural gas through the Fischer-Tropsch process. The experiments were conducted in a 6-cylinder DI diesel engine with pump timing settings of $6^{\circ},\;9^{\circ}\;and\;12^{\circ}$crank angle before TDC over ECE R49 and US 13-mode cycles separately and compared to a conventional diesel fuel. The results show that GTL exhibited almost the same power and torque output, improved fuel economy and effective thermal efficiency. It was found that GTL displayed lower peak in-cylinder combustion pressure and maximum heat release rate (HRR), the timings of the peak pressure and the maximum HRR were generally delayed, and the combustion durations were almost equivalent for diesel and GTL under the same speed-load condition. The results also indicate that, compared to diesel fuel, GTL blends showed a trend forward decreasing four regulated emissions simultaneously and a higher GTL fraction in blends contributing to further reductions in the emissions. In particular and on average, neat GTL significantly reduced HC, CO, NOx and PM by 16.4%, 17.8%, 18.3% and 32.4%, respectively, for all cases.