• Journal of Power System Engineering
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• v.12 no.5
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• pp.27-33
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• 2008

Natural gas has been considered one of the most promising alternative fuels for transportation because of its abundance as well as its ability to reduce regulated pollutants. We measured emission characteristics of nanoparticles from lean burn H/D(Heavy-Duty) CNG (Compressed Natural Gas) engine equipped with oxidation catalysts. The experiments were carried out to measure the emission and engine performance according to the ESC test cycle. The CO and THC conversion efficiencies on the best catalyst in the ESC test cycle achieved about 91 % and 83 %, respectively. From the measurement by the SMPS, the number of nanoparticles emitted from H/D CNG engine is reduced by about 99 % which is more than that of 2.5 L diesel engine. The particle number concentrations of H/D CNG engine were almost nanoparticles. Nanoparticles smaller than 30 nm emitted from the H/D CNG engine and diesel engine equipped with a CDPF(Catalyzed Diesel Particulate Filter) were quite similar. However, the particles bigger than 30nm from the CNG engine were smaller than the particles from diesel engine equipped with a CDPF. The higher the CNG engine load, the lower the particle number from engine-out, but it increased slightly at full load.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.21-26
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• 2011

Emissoin of heavy duty vehicle have much positioned in air pollution although its limited number of vehicles. CNG vehicles are coming to the fore as one of the solution of diesel vehicles. CNG vehicles exhaust smaller emission than diesel vehicles on PM and NOx. In this study, aftertreatment technologies are introduced on vehicles which use CNG and hydrogenmixed fuel. Withmixing hydrogen with CNG, combustion efficiency is enhanced, and harmful emission might be decreased, but methane that is main component of CNG brings green house effect. In order to remove methane and NOx in exhaust gas of CNG engine, methane oxidation catalyst and SCR technologies were respectively analyzed.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.164-169
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• 2015

Recent research has focused on alternative fuel to improve engine performance and to comply with emission regulation. Finding an alternative fuel and reducing environment pollution are the main goals for future internal combustion engines. The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched CNG fuel in SI engine and is to clarify the effects of hydrogen enrichment in CNG fuelled engine on exhaust emission and performance. An experimental study was carried out to obtain fundamental data for performance and emission characteristics of hydrogen enrichment in SI engine. The experiment was conducted at 2500 rpm, bmep 2 bar, 4 bar conditions while CNG fuel was mixed with 10, 20 and 30% hydrogen blends. From the experimental results, combustion duration was shortened due to rapid flame propagation velocity of hydrogen and these were attributed to the burning velocity increasing exponentially with increasing hydrogen blending ratio. Hydrogen has much wider flammable limit than methane, gasoline and the minimum ignition energy is about an order of magnitude lower than for other combustion. By adding hydrogen, $CO_2$ and HC were reduced. However, $NO_X$ was increased dut to high rate of heat release for hydrogen substitutions.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.2
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• pp.89-97
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• 2004

A heavy duty hydrogen enriched CNG engine has the possibility to obtain stable operation at ultra lean condition and to reduce emission extremely. And it can also serve as a so called bridge technology between the current fossil fueled engine and the future hydrogen power system. The emission, torque and brake thermal efficiency characteristics of a heavy-duty hydrogen-CNG engine were investigated to determine the proper mixing rate of hydrogen and CNG. It was found that the proper mixing rates at ${\lambda}=1.4$ and ${\lambda}=1.6$ were around 20% and 30% for hydrogen addition rate respectively.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.9-14
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• 2011

A set of test was conducted on a SA-372 steel for CNG storage tank to study the effect of hydrogen embrittlement. Tensile tests were carried out several conditions such as CNG, HCNG and H2 gas environment including air and Ar under the 35 MPa. Also, the test speed was set at 4*10^-4/s and 4*10^-5/s respectively. To maintain the high pressure for environmental gas during test process, we chose MTS which was installed autoclave. Test results showed that tensile stress, elongation rate and cross sectional contraction under Ar and CNG charging condition were similar to that of reference of air. And there was little bit change with test speed variations. However, hydrogen added conditions such as HCNG and H2 were revealed noticeable change in elongation rate and cross sectional contraction. Tensile stress was still uniform for all conditions. From the results, the effect of hydrogen embrittlement was confirmed on the hydrogen enriched conditions. Also its effect was showed more strong with much hydrogen concentration and slower test speed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.829-833
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• 2012

SNG (synthetic natural gas or substitute natural gas) could contribute greatly toward energy security. In addition, HCNG (or $H_2CNG$) is expected to be used as a fuel gas for internal combustion engines and home appliances because it has extremely low emissions and high thermal efficiency. However, the hydrogen contained in SNG or HCNG can deteriorate the mechanical properties of the materials used in existing natural gas infrastructure. Therefore, it is necessary to investigate the effect of hydrogen on the mechanical properties of such materials so that SNG or HCNG can be transported and distributed safely and reliably. In this study, the effect of highly pressurized hydrogen gas on the tensile properties of a low-alloy steel used for manufacturing CNG storage vessels was investigated using the so-called hollow tensile specimen technique.

• Transactions of Materials Processing
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• v.17 no.4
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• pp.292-301
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• 2008

Type 2 compressed natural gas(CNG) storage vessels for automobiles are becoming widely used. They are not only supplied to automakers in Korea, such as Hyundai Motors, but increasingly, they are being exported overseas. Autofrettage is a process that produces beneficial residual stresses in a vessel by subjecting it to excessive internal pressure. This strengthens the vessel and improves its fatigue resistance. This paper presents research investigating the autoftettage process and residual stresses it produces in type 2 CNG storage vessels. A finite element analysis technique and a closed form equation are used. Then, fatigue resistance is analyzed through a fatigue evaluation performed according to ASME section VIII.

• 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.

• Journal of the Korean Institute of Gas
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• v.17 no.5
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• pp.22-27
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• 2013

HCNG engine is performed as a future engine because of high combustion efficiency and eco-friendly property, and is predicted to a brdge of hydrogen vehicles. As EURO-6 regulagion is due to be applied in 2014, consolidated regulations of methane gas that is exhausted from CNG and HCNG vehicles will come into effect. In this studies, methane oxidation catalyst is introduced to remove methane gas from HCNG emissions. Methane oxidation efficiency on catalyst was studied when it is driven long time. And characterization like metal dispersion, surface area was performed to investigate the correlation of catalyst efficiency and characteristics.

• International Journal of Automotive Technology
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• v.2 no.3
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• pp.93-101
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• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.