• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.632-637
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• 2010

Natural gas, a fossil fuel contained mostly of methane, is one of the cleanest alternative fuels. It can be used in the form of compressed gas(CNG) or liquefied natural gas(LNG) to cars and trucks. And, dedicated natural gas vehicles are designed to run on natural gas only, while Bi-fuel vehicles can also run on gasoline or CNG, especially, bi-fuel can be defined as the simultaneous combustion of two fuels. In this study, converted gasoline marine system to CNG Bi-fuel system which is made up of injector, regulator, tank and ECU is converted. And estimated the fuel system and engine power compared the result with gasoline engine is estimated. As a result, CNG engine shows low exhaust emissions but maxium power is 7% reduced compared to gasoline engine.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.387-394
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• 2013

Hydrogen-compressed natural gas (HCNG) blend has attracted attention as a fuel that can reduce $CO_2$ emissions because it has low carbon content and burns efficiently. An increase in the compression ratio of HCNG engines was considered as one of the methods to improve their efficiency and reduce $CO_2$ emissions. However, a high combustion rate and flame temperature cause abnormal combustion such as pre-ignition or knocks, which in turn can cause damage to the engine components and decrease the engine power. In this study, the performance and knock characteristics with a change in the compression ratio of an HCNG engine were analyzed. The combustion characteristics of HCNG fuel were evaluated as a function of the excess air ratio using a conventional CNG engine. The effects of the compression ratio on the engine performance were evaluated through the same experimental procedures.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.5-12
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• 2012

희박예혼합기의 급속연소에 관한 연구를 위하여 2-실린더 가솔린 엔진을 부실 타입의 압축천연가스(CNG) 분사 엔진으로 개조하였다. 본 연구에서는 부실의 최적설계에 관심을 두고 두 종류의 부실을 적용하여 실험을 실시하였고, 부실의 체적과 홀 개수는 1.5cc와 6개로 각각 동일하게 하고, 홀 직경을 0.8mm 및 1.1mm로 달리하였다. CNG연료는 포트연료분사(Port fuel injection; PFI)와 부실분사(Sub-chamber injection; SCI)에 의해 엔진에 독립적으로 공급되고, 그 실험결과로 구한 연소압력, 평균유효압력(IMEP), 질량연소분율과 사이클변동계수(COV) 등을 서로 비교하였다. 본 연구의 대표적 실험연구결과로서 PFI 타입의 엔진연소특성은 희박예혼합기의 경우를 제외하고 모든 조건에 있어서 기존의 가솔린 엔진과 비슷하였고, SCI 타입의 엔진연소특성으로 평균유효압력은 부실 내에 불완전 예혼합기형성으로 PFI 타입보다 낮았으며, COV는 SCI 타입이 희박가연한계가 확대됨으로 인하여, 특히 높은 공기과잉률 범위에서 PFI 타입과 비교해 보다 좋은 결과를 나타내었다.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.12-17
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• 2000

In this study a heavy duty diesel engine was modified into a 11-liter 6-cylinder SPI CNG dedicated engine, which was tested to investigate the performance and exhaust emission under the maximum load condition as the engine speed was increased in the range of 1,000∼2,200 rpm. The exhaust emission was also measured at D-13 mode as well as AVL-8 mode.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.16-21
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• 2003

Natural gas is one of the promising alternative fuels because of the abundant deposits and the cleanness of emission gas. It can be used in conventional gasoline engine without major modification. Natural gas has some advantages than gasoline i.e. the high octane number, good mixing condition because of gas and wide inflamable limit. In the present study, a $1.8{\ell}$ conventional gasoline engine is modified for using the CNG as a fuel instead of gasoline. Performance and emission characteristics are compared between gasoline and CNG with 4 cylinder SI Engine which is controlled by programable ECU. Parameters of experimentation are equivalence ratio, spark timing and fuels. We analyzed the combustion characteristics of the engine using the cylinder pressure i.e. ignition delay, combustion duration and cycle variation. As a result, CNG engine shows lower exhaust emissions but brake torque is slightly reduced compared to gasoline engine. Overall combustion duration is longer than that of gasoline because of lower burning speed.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.7-12
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• 2013

As emission regulation for vehicle has been reinforced, many researches carried out for HCNG(hydrogen-natural gas blends) fuel to the conventional compressed natural gas (CNG) engine. However, abnormal combustion such as backfire, pre-ignition or knocking can be caused due to high combustion speed of hydrogen and it can result in over heating of engine or reduction of thermal efficiency and power output. In the present study, improvement of combustion performance was observed with HCNG fuel since it can extend a flammability limit. Knocking characteristics for CNG and HCNG fuel were investigated. Feasibility of HCNG fuel was evaluated by checking the knock margin according to excess air ratio. The operation of engine with HCNG was stable at minimum advance for best torque(MBT) spark timing and knock phenomena were not detected. However, it is necessary to prepare higher knock tendency since possibility of knock is higher with HCNG fuel.

• LP가스
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• s.105
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• pp.43-50
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• 2006

연료로서의 DME 디메틸에테르(화학식 CH -O-CH ,DME)는 당초 가정용 캔 스프레이 등 분사 약제인 프레온의 대체 물질로 사용되기 시작했다. 그 후 양호한 압축 착화성이나 무연 연소하는 성질을 가지는 등 디젤 엔진의 연로로서 LP 가스와 동등한 증기압을 가져 LP가스의 대체연료로서 현재 전 세계에서 활발히 연구개발이 이뤄지고 있다. DME의 재료는 천연가스, 석탄, 바이오매스 등 다양한 자원에서 제조가 가능한데 이들로부터 합성가스(CO,H )를 추출.합성해 제조한다. 이것은 경제규모에 미달하는 부존자원의 유효한 이용이나 자원의 다양화에도 연결되기 때문에 차세대 연료로서 주목받고 있다. 천연가스로부터 저가로 대량 생산이 가능한 직적법이나 메탄올을 탈수해 제조하는 간접법 등 제조 기술도 확립되어 있다.

• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.8-14
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• 2015

Synthetic natural gas(SNG), acquired from coal, is regarded as an alternative to natural gas since a rise in natural gas due to high oil price can be coped with it. In the present study, 11-liter heavy duty compressed natural gas(CNG) engine was employed in order to examine the combustion and emission characteristics of SNG. The simulated SNG, made up 90.95% of methane, 6.05% propane and 3% hydrogen was used in the experiment. Power output, thermal efficiency, combustion stability and emission characteristics were compared to those with CNG at the same engine operating conditions. Knocking phenomenon was also analyzed at 1260 rpm, full load condition. Combustion with SNG was more stable than CNG. Nitrogen oxides emissions increased while Carbon dioxides emissions decreased. Anti-knocking characteristics were improved with SNG.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.7-17
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• 2003

Highly accurate control of an air-fuel ratio is very important to reduce exhaust gas emissions of gaseous-fuel engines. In order to achieve this purpose, a precise engine model is required to estimate engine performance from the engine design process which is applied to the design of an engine controller. Engine dynamics are considered to develop a dynamic engine model of a gaseous-fuel engine. An effective air mass ratio is proposed to study variations of the engine dynamics according to the water vapor and the gaseous-fuel in the mixture. The dynamic engine model is validated with the LPG engine under steady and transient operating conditions. The experimental results in the LPG gaseous-fuel engine show that the estimation of the air flow and the air-fuel ratio based upon the effective air mass ratio is more accurate than that of a normal engine model.