• Title/Summary/Keyword: 밀러사이클

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Study on the Performance Factors of Two Stage Turbo-Charging System and Maximization of the Miller Cycle (2단 과급시스템의 성능 인자 영향과 밀러 효과 극대화에 관한 연구)

  • Beak, Hyun-min;Seo, Jung-hoon;Lee, Won-ju;Lee, Ji-woong
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.7
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    • pp.953-960
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    • 2019
  • The Miller cycle is a diesel engine that has been developed in recent years that it can reduce NOx and improve fuel consumption by reducing the compression ratio through intake valve closing (IVC) time control. The Miller cycle can be divided into the early Miller method of closing the intake valve before the bottom dead center (BDC) and the late Miller method of closing the intake valve after the BDC. At low speeds, the late Miller method is advantageous as it can increase the volumetric efficiency; while at medium and high speeds, the early Miller method is advantageous because of the high internal temperature reduction effect due to the expansion of the intake air during the piston lowering from IVC to BDC. Therefore, in consideration of the ef ects of the early and late Miller methods, it is necessary to adopt the most suitable Miller method for the operating conditions. In this study, a two-stage turbo charge system was applied to four-stroke engines and the process of enhancing the Miller effect through a reduction of the intake and exhaust valve overlap as well as the valve change adjustment mechanism were considered. As a result, the ef ects of fuel consumption and Tmax reduction were confirmed by adopting the Miller cycle with a two-stage supercharge, a reduction of valve overlap, and an increase of suction valve lift.

A Study on Flow Characteristics of Spark-Ignited Engine with Variable Intake Valve Closing Timing for Miller Cycle (LIVC 적용 밀러사이클 스파크점화기관의 유동특성 연구)

  • Chung, J.H.;Kang, S.J.;Kim, J.S.;Jeong, S.C.;Lee, J.W.
    • Journal of ILASS-Korea
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    • v.21 no.1
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    • pp.7-12
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    • 2016
  • In this study, to research in-cylinder flow characteristics of spark-ignited engine with intake valve closing timing change for Miller cycle. 3D simulation study were used 6 different intake valve profile with $CAD10^{\circ}$ gap for retard intake valve closing timing. Comparison of In-cylinder flow pattern characteristic were accompanied between Base and LIVC. And the efficiency of volume and the work of compression were analyzed with simulation study. When intake valve closing angle was retarded in $CAD50^{\circ}$, the pressure in cylinder was decreased about 12~13 bar and volume efficiency was reduced about 16%. The efficiency of volume and the work of compression were reduced on LIVC.

Analysis of In-cylinder Flow in a Miller Cycle Engine with Variable IVC for HEV (밀러사이클 적용 HEV 엔진 실린더의 가변흡기밸브 닫힘각에 따른 실린더내 유동해석)

  • Kim, Sangmyeong;Sung, Gisu;Lee, Jinwook
    • Journal of ILASS-Korea
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    • v.19 no.1
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    • pp.25-32
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    • 2014
  • For reduction of $CO_2$ emission emitted from combustion engine, the developed nations have been focused on R&D of hybrid electric vehicle. Further more, many automobile companies are researching on various techniques related to engine used in HEV to enhance fuel economy. One of key techniques is miller cycle that control a valve timing to reduce compression stroke for saving energy and increase expansion stroke for high power. In this study, it was investigated the in-cylinder flow characteristics of miller cycle with variable intake valve timing by using the ANSYS simulation code. For simulation, the key analytic parameter defined as intake valve closing timing and cam profile. As main results, it was shown that LIVC cause a lower pressure inside cylinder and had better control turbulence intensity.

A Study on Combustion Characteristics of Spark-Ignited Engine with Different Late Intake Valve Closing for Miller Cycle (밀러사이클 적용 스파크점화기관의 후기 흡기밸브 닫힘각 변화에 따른 연소성능 연구)

  • Chung, J.H.;Kang, S.J.;Kim, J.S.;Jeong, S.C.;Lee, J.W.
    • Journal of ILASS-Korea
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    • v.20 no.3
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    • pp.141-148
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    • 2015
  • In order to research engine characteristics of spark-ignited engine with intake valve closing timing change for Miller cycle, two cam for LIVC(Late Intake Valve Closing) were designed and fabricated an prototype valvetrain. And intake valve closing timing were adjusted to build low compressing and high expansion cycle for HEV. In experimental study, it were investigated with different engine speed, spark timing and air-fuel ratio to compare base cam and LIVC cam type. It was found that the volumetry efficiency and effective work of compression process were decreased in case of LIVC cam. When compared with the existing results, the maximum pressure in the cylinder was reduced about 12~13 bar and the volumetric efficiency was reduced about 16%.

A Thermodynamic Analysis on the Performance with turning Diesel Cycle into Diesel-Atkinson Cycle (디젤기관의 아트킨슨 사이클화에 따른 제반성능의 열역학적 해석)

  • 노기철;정양주;이종태
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.5
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    • pp.1-11
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    • 2004
  • In order to recognize thermal efficiency and power improvement in case that diesel cycle is turned into diesel-atkinson cycle, the fuel-air diesel-atkinson cycle considered gas exchange process is analyzed non-dimensionally and thermodynamically. As a result, in case of diesel-atkinson cycle, as expansion ratio is increased, thermal efficiency and mean effective pressure is increased and it has maximum value at Rec=1. When diesel cycle is turned into diesel-atkinson cycle by late intake valve closing timing, thermal efficiency and power is decreased because of the decline of effective compression ratio and intake airflow, but it could be compensated by increase of compression ratio or super-charged. In case compression ratio is compensated, Rec appears 1 around 100$^{\circ}$ ABDC, and it is expected that thermal efficiency is enhanced by 14.3% compared with conventional diesel cycle. In case compression ratio and intake airflow are compensated simultaneously, super-charged pressure is demanded 2.06bar at Rec=1 and it is more efficient when only compression ratio is compensated in the view point of thermal efficiency.

A Study on the Cycle Analyzing and Intake Valve Control by the Miller Method with a High Expansion into Low-Speed Diesel Engine (저속 디젤기관에서 고팽창의 밀러방식에 의한 사이클 해석 및 흡기밸브제어에 대한 연구)

  • Jag, Tae-Ik
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.8
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    • pp.1100-1106
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    • 2009
  • Recently, there are quite a lot of attention is drown on the researches related to of Miller method applied high expansion cycle. For this study, high expansion cycles are formed and analyzed with the base view point of thermodynamics, and the features of each factors are also investigated. As a result of analysis, the expansion-compression ratio is expected with a decrease of effective compression ratio as intake valve closing time retarded, however, the decrease of mean effective pressure and its output is accompanied with the counterflow of intake air. Accordingly, as the consequence of such failure, it is expected that an alternative is needed for the realization of high expansion cycles, and the improvement over thermal efficiency. To materialize such cycle, the control system to delay the closing time of intake valve was designed and VVT, the 3 S/B low speed diesel engine, is applied to evaluate the efficiency. The result of the trial shows that there was no significant errors.

Prediction of Matching Performance of Two-Stage Turbo-charging System Design for Marine Diesel Engine (선박용 디젤엔진의 2단과급 시스템설계를 위한 매칭성능 예측)

  • Bae, Jin-woo;Lee, Ji-woong;Jung, Kyun-sik;Choi, Jae-sung
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.6
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    • pp.626-632
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    • 2015
  • The International Maritime Organization (IMO) has adopted several regulations for the prevention of air pollution from ships. In addition, there is a requirement for shipping liners to reduce greenhouse gas emissions. Accordingly, we need to take measurements to ensure that the steps taken are both efficient and environmentally friendly. It has been determined that the application of the Miller cycle in diesel engines has the effect of both reducing the amount of NOx and improving thermal efficiency. However, this method requires a considerably larger charge air pressure. Therefore, we consider a two-stage turbo-charging system, which not only results in a high charging pressure, but also improves the part load performance with an exhaust-gas bypass system or the application of the Miller cycle. Because of complications associated with the two-stage turbo-charging system, it is complex and difficult to realize a design that optimizes matching between diesel engine and turbo-chargers. Accordingly, it is necessary to perform a quantitative analysis to determine the effects and optimal conditions of these different systems in the early stage of system design. In this paper, we develop a simulation program to model these systems, and we verify that the results of this program are reliable. Further, we discuss methods that can be employed to improve its efficiency.

An Experimental Study on Measurement of Flow Coefficient Using the Steady-Flow Test Rig (정상유동장치를 이용한 유량계수 측정에 관한 실험적 연구)

  • Park, Sang-Wook;Choi, Ik-Soo;Noh, Ki-Chol;Ryu, Soon-Pil;Yoon, Keon-Sik
    • Journal of Advanced Marine Engineering and Technology
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    • v.36 no.4
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    • pp.423-429
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    • 2012
  • Miller cycle is considered as an effective means to meet the regulation on Tier II and to reduce $CO_2$ emission. For this cycle, the amount of intake air supplied should be enough increased. Therefore, the intake system with minimized resistance for air flow is under consideration. In this study, the flow coefficients of intake valves were measured in order to obtain the basic data for the cycle simulation and intake port design. The flow coefficients were measured using the steady-flow test rig. As a test result for the poppet valve used the marine engine with medium speed, the flow coefficients are increased to about 0.62 with the valve lift. In addition it is confirmed that the flow coefficients have the characteristic value irrelevant to the S/B ratio.

Development and Performance Evaluation for 1.6MW Gas Engine (1.6MW급 가스엔진의 개발 및 엔진성능평가)

  • Noh, Ki-Chol;Seol, Dong-Il;Hu, Kyoung-Me;Kim, Se-Hun
    • Journal of Advanced Marine Engineering and Technology
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    • v.36 no.2
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    • pp.230-237
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    • 2012
  • Engine makers are lately interested in the gas engine development as the alternative for diesel engine in order to cope the rise of oil price and the environmental regulation. So, STX has developed the 1.6MW gas engine which was converted from 22HLX diesel engine. The gas engine developed with precombustion chamber, which has good performance of 21bar BMEP at engine speed 1000rpm and low $NO_X$ emission of 50ppm at 15% oxygen composition, has been developed recently. Especially, it has a good thermal efficiency of 45% and a reduction efficiency of green house gas($CO_2$) emission of 25% than a conventional diesel engine.

Evaluation on a Miller Cam for Improving the Fuel Consumption of a Large Diesel Engine (대형 디젤 엔진의 연비 향상을 위한 Miller Cam 평가)

  • Song, Changhoon;Wang, Tae Joong;Im, Heejun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.1
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    • pp.47-52
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    • 2016
  • Miller timing is one of the promising ways which can improve the fuel consumption of internal combustion engines. Indeed, Miller timing employing an early intake valve close is widely applied to large diesel and gas engines to enhance performance and reduce NOx emissions. In this study, performance evaluation is carried out by 1-D cycle simulation in order to estimate the effect of Miller CAM timing before BDC for a 32 L turbocharged diesel engine. To optimize Miller CAM timing, a single stage turbocharger is matched with an early intake valve close since boost pressure is a significant parameter that can control compression work in a turbocharged engine. The engine simulation result shows that there is enough potential to improve fuel consumption rate and also reduce NOx emissions at the same time.Abstract here.