• International Journal of Automotive Technology
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• 제8권6호
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• pp.697-704
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• 2007

Recently, a variable valve timing system has been widely adopted in internal combustion engine in order to improve the fuel economy and torque at low engine speed. In addition, it is known that varying valve timing according to the various engine operations could reduce exhaust gas, especially NOx, because of residual gas by valve overlap. In this study, to improve the low exhaust gas and fuel economy at part load condition, the residual gas and back flow of exhaust gas due to valve overlap were calculated computationally. Moreover, the characteristics of engine performances and NOx formations were investigated with the experiment of combination of intake and exhaust valve timing condition. Under these various valve operating conditions, the effects of both the positive valve overlap and negative valve overlap(valve underlap) were examined simultaneously. Finally, the characteristics of cyclic THC emission were analyzed by using Fast Response FID(FR-FID) in the cylinder, intake port and exhaust port positions. Besides, the effect of the different gradients of the valve timing change on engine performance was investigated and an optimum control strategy was suggested.

• 에너지공학
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• 제25권2호
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• pp.29-36
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• 2016

도시지역에서는 발전용 디젤엔진의 운영비를 절약하기 위해 천연가스와 디젤을 섞어서 쓰려는 노력을 하고 있다. 본 연구에서는 디젤 연료의 일부를 천연가스로 대체 하였을 때 엔진특성과 천연가스로 대체되는 양에 따라 최적의 밸브 타이밍을 찾아보았다. 1-D 엔진 해석프로그램을 사용하여 19.7리터 발전용 디젤 엔진을 대상으로 모델링하여 연구를 진행하였다. 연구 결과 엔진연료에서 천연가스 비율이 증가할수록 연료소비율(Brake Specific Fuel Consumption, BSFC)는 증가하였고 질소산화물(Brake Specific NOx)는 감소하였다. 추가적으로 흡기밸브 타이밍을 조절할 경우 BSFC가 최대 1%감소하였고 BSNOx의 경우 최대 36%감소하는 효과가 있었다.

• 한국자동차공학회논문집
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• 제15권6호
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• pp.87-93
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• 2007

It is complicate to analysis the systems, dual mode hybrid systems, because they are composed of many planetary gear sets. For the performance test, it needs to define the systems with representative parameters. In this paper, system parameters, $\alpha$, $\beta$, $\zeta$, are introduced to define the systems, and an arbitrary system like E-IVT developed by Renault Motors is converted to the general system having equivalent parameters, such as $\beta'$, $R'_b$. Pontryagin principle and Kuhn-Tucker condition method are applied to solve the constrained problems, by which the methodology for accelerating test is generalized, and the results of the simulation are reported. In addition, the effects of alternative strategies are mentioned. The method of fuel economy test at engine mode is also introduced. The results of test at engine mode is different from the results of optimal trajectory, but the fuel economy of the engine mode is related to the highway driving and optimized operating of the system.

• 한국분무공학회지
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• 제5권2호
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• pp.28-34
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• 2000

To reduce the soot and NOx simultaneously, a new system of stratified injection is developed. This system discharges stratified diesel-methanol in a D. I. Diesel Engine. Nozzle and delivery valve of conventional injection system were remodeled to inject diesel and methanol from one injector sequently. The quantity of diesel and methanol was controled precisely by micrometers mounted on the injection control lack. The real injection ratio of dual fuel was measured by volumetric ratio. We could confirm the capabilities that soot and NOx simultaneously were reduced by diesel-methanol stratified injection from the results of in-cylinder pressure data obtained from combustion experiment by stratified injection, heat release rate and mass fraction bumed.

• 한국대기환경학회지
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• 제26권5호
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• pp.469-474
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• 2010

Gasoline engines have proven their utility in light, medium and heavy duty vehicles. Concern about long term availability of petroleum and the environment norms by the increased vehicular emission have mandated the search for safe fuel. CNG is an environmentally clean alternative to the existing spark ignition engines with the advantages of minimum change. A higher octane number and a higher self ignition temperature make it an attractive gaseous fuel. The thermal efficiency is better than gasoline for the same engine. The reduced carbon mono oxide, carbon di-oxide, hydrocarbon emissions is a favorable outcome along with a slight increase in $NO_x$ emission when compared with gasoline fuel to a dual fuel mode in the existing spark ignition engines. The result from the experiment shows that CNG could be a potential substitute fuel that maintains performance and emissions characteristics in gasoline engines.

• Journal of Electrical Engineering and Technology
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• 제3권4호
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• pp.593-598
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• 2008

The power distribution is proposed to determine the target operating points of the system components as the basis for maximal the efficiency of the overall system for a power split dual electric machine hybrid electric bus. The coordinated control is constructed on the basis of the power distribution. The basic coordinated control is implemented to satisfy the driver's power demand, in which both the dynamic characteristics of the engine and the dual electric machine are explicitly taken into account. Moreover, the improved coordinated control is suggested to suppress engine dynamic operation and rich fuel injection.

• 한국항공운항학회지
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• 제14권1호
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• pp.15-21
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• 2006

Parametric cycle analysis of a dual-spool, mixed exhaust turbofan engine with turbine blade cooling were described to investigate the effect of turbine blade cooling on the engine performance such as specific thrust and thrust specific fuel consumption. Coolant of low pressure turbine triggers high engine performance loss and cooling effect loss in high pressure turbine. Therefore low pressure turbine coolant should be much more considered for effective design.

• Journal of Advanced Marine Engineering and Technology
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• 제40권6호
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• pp.499-503
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• 2016

배기가스의 배출을 현저하게 저감시켜 강화된 환경규제에 적합한 DF 엔진의 고압 가연성 가스를 공급하기 위한 이중관 가스 벨로우즈의 연구개발에 대한 필요성이 대두되고 있다. 본 연구에서는 최적화된 이중관 벨로우즈의 개발을 위한 것으로, 내식성재료인 오스테나이트계 스테인리스강에 대하여 이중관으로 벨로우즈화하는 성형방법과 최적화된 용접 조건을 도출하여 다양한 성능평가를 통해 생산된 시제품의 신뢰성을 확보하기 위한 연구를 수행하였다. 본 연구의 제1보에서는 최적화된 벨로우즈를 설계하기 위하여 구조설계, 좌굴해석 및 응력해석을 통해 좌굴 발생 하중 및 벨로우즈 응력을 해석하였다. 그 결과 엠보싱 형상을 가진 벨로우즈의 경우 좌굴 발생 하중이 약 1.6배 증가하였으며, 최대 설계압력보다 2배인 30.0 bar에서 어떠한 좌굴 및 스컴이 발생하지 않는다는 것을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제24권3호
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• pp.242-248
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• 2013

The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched LPG fuel in LPG engine and is to clarify the effects of hydrogen enrichment in LPG 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 LPG engine. The research was held by changing the hydrogen ratio to 0, 5, 10, 20% in 1500rpm, bmep 2 and 4bar. The result turned out that the combustion duration was shortened due to fast flame propagation of hydrogen. And the amount of Carbon dioxide and Hydrocarbon decreased. However, the amount of NOX increased, which is thought to be the result of high adiabatic flame temperature of hydrogen. It has been confirmed that this phenomenon has changed by the Hydrogen mixing ratio.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.155-165
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• 2013

The effect of gaseous ammonia direct injection on the engine performance and exhaust emissions in gasoline-ammonia dual fueled spark-ignition engine was investigated in this study. Results show that based on the gasoline contribution engine power increases as the ammonia injection timing and duration is advanced and increased, respectively. However, as the initial amount of gasoline is increased the maximum power output contribution from ammonia is reduced. For gasoline-ammonia, the appropriate injection timing is found to range from 320 BTDC at low loads to 370 BTDC at high loads and the peak pressures are slightly lower than that for gasoline due to the slow flame speed of ammonia, resulting in the reduction of combustion efficiency. The brake specific energy consumption (BSEC) for gasoline-ammonia has little difference compared to the BSEC for gasoline only. Ammonia direct injection causes slight reduction of $CO_2$ and CO for all presented loads but significantly increases HC due to the low combustion efficiency of ammonia. Also, ammonia direct injection results in both increased ammonia and NOx in the exhaust due to formation of fuel NOx and ammonia slip.