• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1009-1015
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• 2011

In this study, in the high expansion cycle was conduced by variable valve timing system composition to close intake valve late, and in the intake air reduction on the low compression was solved by supercharging pressure. In this wise, by constituting Diesel-Atkinson cycle, this study looked into a possibility of thermal efficiency improvement. As a result, there was improvement in thermal efficiency and output in a whole range of closing timing from ABDC $40^{\circ}$ to ABDC $80^{\circ}$. However, after ABDC $70^{\circ}$ of closing timing, the thermal efficiency increase was getting smaller. As the result of the study, the optimum intake valve closing timing was about ABDC $70^{\circ}$, high loading territory of engine was more effective than low loading territory, and engine operation in middle loading territory was stable. At this time, brake thermal efficiency was 12.5% higher than ordinary engine on average.

• 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.