• 한국자동차공학회논문집
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• 제20권4호
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• pp.150-155
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• 2012

Lean NOx Trap (LNT) catalysts are capable of reducing exhaust NOx emissions from diesel engines. LNT stores NOx in lean condition and exhausts N2 by reducing NOx in rich condition. NOx reduction characteristic of LNT catalysts using throttle position sensor and fuel injection timing control for light-duty diesel engine was investigated. In contrast to SCR system, LNT catalyst uses diesel fuel in resuctant. Also if the concentration of reductant is exceeded, excessive amount of reductant will slip throughout LNT and cause another emission problem. Thus LNT regeneration with precise engine control established that can make higher NOx conversion efficiency and lower fuel penalty, prevent another emission problem. NOx and reductant concentration were measured by the NOx sensor and Mexa7100D equipped inlet and outlet of catalyst. As a result of engine test, regeneration strategy has reached high of 77.8% NOx conversion efficiency according to engine operation condition. Moreover, we have proved that it is possible to use regeneration strategy of LNT within 5% fuel penalty.

• 대한기계학회논문집B
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• 제34권7호
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• pp.689-696
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• 2010

디젤엔진은 높은 열효율과 우수한 연비 성능 등의 장점을 가지고 있으나, 기화된 연료와 주변 공기가 혼합된 후 착화되는 과정을 거치기 때문에 이론 공연비 영역에서는 질소산화물(NOx) 배출이 증가되는 문제점을 가지고 있다. 최근 활발히 연구되고 있는 높은 정화 효율을 가진 LNT 촉매는 희박 분위기 조건에서는 NOx를 흡장하게 되고 과농한 분위기에서는 환원 분위기 형성을 통하여 NOx를 저감시키게 된다. 희박 공연비에서 동작하는 디젤 엔진에서는 이러한 환원 과정을 이루기 위해 주기적으로 과농한 분위기를 형성해주어야만 하는데, 이러한 연구는 NOx 저감을 위해 HC를 포함한 환원제의 농도를 제어하는 기술로서 본 연구에서는 디젤을 연료로 하는 수소농후가스 발생장치를 이용하여 LNT 촉매에 환원제로서 수소농후가스를 직접 공급하는 방식으로 LNT 촉매의 NOx 저감 특성을 파악하였다.

• 한국연소학회지
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• 제20권1호
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• pp.6-14
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• 2015

Numerical study was conducted to clarify effects of added $H_2O$ for the downstream interaction between $H_2$-air and CO-air premixed flames in counterflow configuration. The reaction mechanism adopted was Davis model which had been known to be well in agreement with reliable experimental data. The results showed that both lean and rich flammable limits were reduced in increase of strain rate. The most discernible difference between the two with and without having $H_2O$ and/or $H_2$ addition into $H_2$-air and CO-air premixtures was two flammable islands for the former and one island for the latter at high strain flame conditions. Even a small amount of $H_2$, in which $H_2$-air premixed flame cannot be sustained by itself, participates in CO oxidation, thereby altering the CO-oxidation reaction path from the main reaction route $CO+O_2{\rightarrow}CO_2+O$ with a very long chemical time in CO-air flame to the OH-related reaction routes including $CO+OH{\rightarrow}CO_2+H$ with very short chemical times. This intrinsic nature alters flame stability maps appreciably. The results also showed that chemical effects of added $H_2O$ help lean flames at relatively low strain rate be sustained, and suppress the flame stabilization at high strain rates.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2181-2185
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• 2008

Fuel processing systems which convert HC fuel into $H_2$ rich gas (such as stream reforming, partial oxidation, auto-thermal reforming) need high temperature environment($600-1000^{\circ}C$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1-5kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural & anode off gas as reformer fuel. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity.

• Asian-Australasian Journal of Animal Sciences
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• 제31권5호
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• pp.712-720
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• 2018

Objective: The aim of this experiment was to evaluate the effect of dietary supplementation with the docosahexaenoic acid (DHA)-rich microalgae, Aurantiochytrium limacinum (AURA) on pig performance, carcass traits, and the fatty acid composition of pork Longissimus lumborum (LL) and backfat. Methods: A total of 144 Pig Improvement Company (PIC)${\times}$Goland finishing pigs (72 females and 72 castrated males) of mean weight 117.1 (${\pm}13.1$) kg were blocked by sex and body weight and provided with 0% or 1% AURA in isonutritive and isocaloric diets. A total of 24 pens provided 12 replicates per treatment. Animals were weighed on day 0 and 28 with feed and water intake recorded per pen. After 31 days supplementation (28 days of study and 3 days until the slaughtering date) three animals per pen (n = 72) were slaughtered and the LL and backfat thickness, lean meat content and dressing percentage were recorded for the carcasses. The fatty acid (FA) profile of the LL and backfat was established by direct FA methyl ester synthesis. Results: No differences were observed for any performance parameters or carcass traits. Supplementation with AURA resulted in significant changes to the FA profiles of both the LL and backfat with male and female pigs responding differently to supplementation in terms of particular FAs. Overall, pork LL samples had significantly higher eicosapentaenoic acid (p<0.001) and DHA concentrations (p<0.001), and higher omega-3 (n-3) FAs (p<0.001), as well as an increased omega3:omega6 (n-3:n-6) ratio (p = 0.001). For backfat, supplementation resulted in significantly higher amounts of DHA (p<0.001) and n-3 FAs (p<0.001). Conclusion: These results indicate that dietary supplementation with 1% AURA over a 31 day period can increase the FA composition of pork LL and backfat, specifically the DHA, with no major impact on growth performance and carcass traits.

• 연구논문집
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• 통권27호
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• pp.101-108
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• 1997

The characteristics of combustion and emissions in multi-staged oil burner have been experimentally studied for the various range of equivalence ratios, drop sizes and fuel formulations. Malvern system was used to measure droplet size of fuel. Light fuel oil and light fuel oil doped with pyridine($C_5H _5N$) were used to investigate the effects on fuel NOx emission. The emissions of NO and CO in exhaust gas and the flame temperatures were measured by the gas analyzer and thennocouples. NOx emissions were increased by increasing the excess air ratio (range:$lambda=1.1-1.4$) or decreasing the SMD of droplet in single-staged burner. In comparison with the single-staged burner, the emission of NOx in multi-staged burner was reduced by 50% but CO emission was slightly increased. It is found that multi-staged burner has a good capability in reducing thermal NOx resulting from the distributed heat release rate and lower flame temperature in fuel-rich and fuel-lean combustion zone. Moreover, the fuel NOx emission of the multi-staged burner is lower than that of single-staged burner, because multi-staged burner has fuel rich zone where fuel N is converted to $N_2$ more than NO. In 3-staged burner, the percentage of each stage combustion air have strong influence on emission characteristics. It is also found that NOx emission can be reduced by decreasing inner and outer air percentage or increasing middle air flow rate and CO emission is vice versa.

• 한국가스학회지
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• 제19권4호
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• pp.22-28
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• 2015

LPG가 수송용 연료로서 경쟁력을 유지하기 위해서는 지속적인 기술개발을 통해 휘발유와의 연비격차를 감소시키고 후처리시스템 등에 의한 가격 부담을 낮추어야 한다. 이에 본 연구에서는 안정적인 희박연소 구현을 통한 연비개선을 얻기 위해 실린더 중앙에 점화플러그와 연료분사기가 인접해 있고, 연료가 분사된 후 바로 점화가 이루어지도록 하는 분무유도방식의 LPG 직접분사엔진을 개발의 일환으로 연소제어인자의 변화에 따른 연소 특성을 분석하였다. 안정적인 연소를 위해 국부적으로 농후한 혼합기를 형성하는 성층희박연소의 특성상 일정 수준이상의 질소산화물이 배출되는 문제점을 갖고 있다. 질소산화물 저감을 위해 EGR을 적용한 결과 연료소비율과 THC의 배출은 약간 증가하지만 $NO_x$배출은 약 15% 저감되었다. EGR 적용에 의한 연소속도의 감소는 초기 화염발달 시기에 집중되어 나타났으며 흡입공기의 희석효과에 의해 EGR율이 증가할수록 최대 열방출율 및 열방출율 증가 기울기가 감소하였다.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.1-8
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the exhaust emission characteristics of homogeneous charge, stratified pattern and inhomogeneous charge under various conditions using gas chromatography. In the case of homogeneous charge condition, the $CO_2$ concentration is proportional to excess air ratio and overall charge pressure, the $CO_2$ concentration is proportional to excess air ratio and the UHC concentration is inversely proportional to ignition time and overall charge pressure. In the case of stratified pattern, the RI(rich injection) condition shows better exhaust emission characteristics, especially $CO_2$, than that of HI (homogeneous injection) or LI (lean injection) conditions. In inhomogeneous charge conditions, when initial charge pressure is increased, $CO_2$ and UHC concentration is reduced but $O_2$ concentration is increased. And when the excess air ratio of initial charge mixture is 3.0, UHC and $CO_2$concentration show lowest values.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.27-32
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• 2003

Diesel-Fueled HCCI(Homogeneous Charge Compression Ignition) Engine is an advanced combustion process explained as a premixed charge of diesel fuel and air is admitted into the cylinder and compression ignited. It has possibility to reduce NOx by spontaneous auto-ignition at multiple points that allows very lean combustion resulting in low combustion temperatures. Also PM could be reduced by the premixed combustion and no fuel-rich zones. But HCCI couldn't be realized because of the difficulties in vaporizing the diesel, control of combustion phase directly. To solve these problems, new fuel injection strategy, explained as the pilot fuel injection to promote ignition near TDC following the main fuel injection at the extremely advanced timing, is applied during the compression ratio is varied from 18.9:1 to 27.7:1 This is not a pilot fuel to promote the ignition but also the direct control method of the combustion phase. Experimental result shows the pilot fuel injection promote the ignition and the compression ignition of the HCCI engine is achieved as compression ratio becomes higher. Also there is an optimal pilot fuel injection timing for the HCCI combustion. NOx is reduced more than 90% compared to DI-Diesel case but PM and THC emission needs more investigation.

• 대한기계학회논문집B
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• 제21권3호
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• pp.358-370
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• 1997

In the present study, investigations were carried out to obtain data on combustion characteristics of methane gas and hydrogen supplemented methane gas in a constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The maximum combustion pressure increases as the initial pressure and hydrogen supplement rate increase, the total burning time is shorten by lowering the initial pressure and by increasing the hydrogen supplement rate. The maximum flame temperature and NO concentration increase by the initial pressure and hydrogen supplement rate increase. The flame propagation processes in near stoichiometric mixture are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate.