• Title/Summary/Keyword: Residual EGR

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A Study on the Application of the Built-in EGR System for Diesel Engine (디젤기관의 내장형 EGR시스템 적용 가능성에 관한 연구)

  • 최재성
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.3
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    • pp.398-404
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    • 1999
  • The EGR is needed for one of various strategies to reduce NOx emission. But to get the proper EGR rate the intake and exhaust system become complicated. That is a reason why we consider using the built0in EGR system. The built-in EGR is a system which reduces Nox by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results the possibility of suing the built-in EGR system was confirmed.

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A Study on the Residual Gas Fraction in Cylinder by the Adjustment of Variable Valve Timing with Volumetric Efficiency (체적효율을 고려한 가변밸브 개폐시기의 조정에 의한 실린더내 잔류가스량에 관한 연구)

  • 남정길
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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    • pp.82-88
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    • 2001
  • The EGR is needed fur one of various strategies to reduce NOx emission. But to get the proper EGR rate, the intake and exhaust system become complicated. That is a reason why we consider using the internal EGR system. The internal EGR is a system which reduces NOx by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper, characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results, residual gas fraction and volumetric efficiency in cylinder by variable valve timing were visualized.

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A Study for Predictions of In-Cylinder Residual Gas Fraction in SI Engines (SI 엔진 내부의 잔류가스 추정 기법에 관한 연구)

  • Kim, Sung-Cheol;Lee, Sang-Jin;Kim, Duk-Sang;Ohm, In-Yong;Cho, Yong-Seok
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.903-908
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    • 2001
  • Residual gas acts as a diluent which results in reducing the in-cylinder temperature as well as the flame speed, significantly affecting fuel economy, NOx emissions and combustion stability. Therefore it is important to determine the residual gas fraction as a function of the engine operating parameters accurately. However, the determination of the residual gas fraction is very sophisticated due to the unsteady state of induction and exhaust process. There has been little work toward the development of a generally applicable model for quantitative predictions of residual gas fraction. In this paper, a simple model for calculating the residual gas fraction in SI engines was formulated. The effects of engine operating parameters on the residual gas were also investigated. The amount of fresh air was evaluated through AFR and fuel consumption. After this, from the intake temperature and pressure, the amount of total cylinder-charging gas was estimated. The residual fraction was derived by comparing the total charging and fresh air. This results coincide with measured value very well.

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Estimation of Exhaust Gas Recirculation using In-Cylinder Residual Gas Fraction in an SI Engine (잔류가스 추정 기법을 이용한 EGR율의 예측)

  • 김득상;김성철;황승환;조용석;엄인용
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.1
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    • pp.55-60
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    • 2004
  • Residual gas acts as a diluent which results in reducing the in-cylinder temperature as well as the flame speed, significantly affecting fuel economy, NOx emissions and combustion stability. Therefore it is important to determine the residual gas fraction as a function of the engine operating parameters accurately. However, the determination of the residual gas fraction is very sophisticated due to the unsteady state of induction and exhaust process. There has been little work toward the development of a generally applicable model for quantitative predictions of residual gas fraction. In this paper, a simple model for calculating the residual gas fraction in SI engines was suggested. The amount of fresh air was evaluated through AFR and fuel consumption. After this, from the intake temperature and pressure, the amount of total cylinder-charging gas was estimated. The residual gas fraction was derived by comparing the total charging and fresh air. This results coincide with measured EGR value very well.

An usefulness study on estimation and control method of EGR ratio using intake manifold pressure in an gasoline engine (가솔린엔진에서 흡기관 압력을 이용한 EGR율의 추정 및 제어 방법에 관한 유용성 연구)

  • Park, Hyeong-Seon;Yoon, Jun-Kyu
    • Journal of Advanced Marine Engineering and Technology
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    • v.38 no.7
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    • pp.806-813
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    • 2014
  • The EGR system being reburned the part of the exhaust gas through intake system indicates more favorable emission characteristics to reduce NOx in a gasoline engine, but the case of inappropriate exhaust gas quantity induced from engine is fallen engine power caused by unstable combustion. In this study, we examined a method to predict EGR ratio according to various engine operation condition based by intake manifold pressure and confirmed such a prediction data through an experimental method. And after having constituted feedback EGR control algorithm in a base with such a prediction data, we acquired qualitatively similar results by having compared data provided through an EGR feedback control experiment with the data which calculated quantity of residual gas for the engine operation condition. Therefore, the applied algorithm and the system for feedback EGR control showed feasibility applied to real electronic control EGR technology.

The Effect of Control of the VGT and EGR in a Turbocharged Common-Rail Diesel Engine on Emissions under Partial Loads Conditions (부분부하에서 커먼레일 과급 디젤엔진의 VGT와 EGR 제어가 배출물에 미치는 영향)

  • Jeong, Soo-Jin;Chung, Jae-Woo;Kang, Jeong-Ho;Kang, Woo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.6
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    • pp.151-158
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    • 2007
  • The static and dynamic behaviour of VGT and EGR systems has a significant impact on overall engine performance, fuel economy and exhaust emissions. This is because they define the state and composition of the air charge entering the engine. This work focused on the effect of the aperture ratio of VGT and EGR on the emission and flow characteristics under partial loads conditions. The investigation carried out using 2 liter PCCI 4 cylinder diesel engine with VGT and EGR. The result of this study shows that smoke increases with increasing EGR rate and NOx decreases with increasing EGR rate. It was also found that the residual gas contents greatly impact on soot emission under partial load condition. Finally, it can be concluded that VGT and EGR aperture ratio can greatly impact not only on soot and NOx but also air charging.

A Study on the Kernel Formation & Development for Lean Burn and EGR Engine (희박연소 및 EGR 엔진에서 초기 화염액 생성 및 성장에 관한 연구)

  • 송정훈;선우명호
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.8
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    • pp.24-33
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    • 1999
  • This paper investigate the effects of the variations of engine operation condition in the flame kernel formation and developmnet . A model for calculating the initial kernel development in spark ignition engines is formualted. It considered input of electrical energy, combustion energy release and heat transfer to the spark plyg, cylinder head, and unburned mixture. The model also takes into accounts strain rate of initial kernel and residual gas fraction. The breakdown process and the subsequent electrical power input initially control the kernel growth while intermediate growth is mainly dominated by diffusion or conduction. Then, the flame propagates by the chemical energy and turbulent flame expansion. Flame kernel development also influenced by engine operating conditions, for example, EGR rate, air-fuel ration and intake manifold pressure.

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An Experimental Study on the Combustion and Emission Characteristics of the Early Injection in a Gasoline Direct Injection Engine Using Controlled Auto Ignition Combustion Method (CAI 연소 방법을 이용한 직분식 가솔린 엔진내의 조기 분사시 연소 및 배기 특성에 관한 실험적 연구)

  • Choi Young-Jong;Lee Ki-Hyung;Lee Chang-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.5 s.248
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    • pp.457-464
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    • 2006
  • Controlled auto ignition (CAI) combustion, also known as HCCI (homogeneous charge compression ignition), offers the potential to simultaneously improve fuel economy and reduce emission. CAI-combustion was achieved in a single cylinder gasoline DI engine, with a cylinder running in a CAI mode. Standard components were used the camshafts which had been modified in order to restrict the gas exchange process. The effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region were investigated. The effect that injection timings on factor such as start of combustion, combustion duration and heat release rate was also investigated. From results early injection caused the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gave rise to good mixing of the fuel-air.

An Experimental Study on the Extend of the Operating Region and Emission Characteristics Through Ohe Stratined Combustion Using Controlled Auto-Ignition Method (CAI 연소 방법을 이용한 성층 연소를 통한 운전 영역 확대, 연소 및 배기 특성에 관한 실험적 연구)

  • Jeoung Hae-Young;Lee Ki-Hyung;Lee Chang-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.5 s.248
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    • pp.465-471
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    • 2006
  • Controlled auto-ignition(CAI) combustion, offers the potential to improve fuel economy and reduce emission simultaneously. In this study, CAI-combustion was achieved in a single cylinder gasoline DI engine with modified camshafts in order to restrict the gas exchange process. We investigated the effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region. The effect of injection timings on combustion characteristic such as start of combustion, combustion duration and heat release rate was also investigated. From the result early injection causes the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gives rise to good mixing of the fuel/air. On the other hand, late injection extended the operation region more than early injection but the emissions of HC and NOx were more or less increased than early injection.

ANALYSIS OF HCCI COMBUSTION CHARACTERISTICS BASED ON EXPERIMENTATION AND SIMULATIONS-INFLUENCE OF FUEL OCTANE NUMBER AND INTERNAL EGR ON COMBUSTION

  • Iijima, A.;Yoshida, K.;Shoji, H.;Lee, J.T.
    • International Journal of Automotive Technology
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    • v.8 no.2
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    • pp.137-147
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    • 2007
  • Homogenous Charge Compression Ignition (HCCI) combustion systems can be broadly divided for the process applied to 4-stroke and 2-stroke engines. The former process is often referred to as simply HCCI combustion and the latter process as Active Thermo-Atmosphere Combustion (ATAC). The region of stable engine operation tends to differ greatly between the two processes. In this study, it was shown that the HCCI combustion process of a 4-stroke engine, characterized by the occurrence of autoignition under a high compression ratio, a lean mixture and wide open throttle operation, could be simulated by operating a 2-stroke engine at a higher compression ratio. On that basis, a comparison was made of the combustion characteristics of high-compression-ratio HCCI combustion and ATAC, characterized as autoignited combustion in the presence of a large quantity of residual gas at a low compression ratio and part throttle. The results showed that one major difference between these two combustion processes was their different degrees of susceptibility to the occurrence of cool flame reactions. Compared with high-compression-ratio HCCI combustion, the ignition timing of ATAC tended not to change in relation to different fuel octane numbers. Furthermore, when internal EGR was applied to high-compression-ratio HCCI combustion, it resulted in combustion characteristics resembling ATAC. Specifically, as the internal EGR rate was increased, the ignition timing showed less change in relation to changes in the octane number and the region of stable engine operation also approached that of ATAC.