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전산유체역학을 이용한 LNG 엔진용 가스진입밸브의 3차원 맥동 유동해석
정수진(Soo Jin Jeong),서석판(Seokpan Seo) 한국자동차공학회 2021 한국자동차공학회 지부 학술대회 논문집 Vol.2021 No.5
Gas admission valve shaped flow obstructing flow devices are widely used to supply flow rates of natural gas to intake manifold in LNG fuelled engine. Inside gas admission valve, highly pulsating flow is found due to moving plate axially vibrating with frequencies ranging from 5 to 9Hz. However, previous numerical investigations of gas admission valve based on steady non-pulsating flows were widely reported in literature because of its simplicity. In this paper, three-dimensional CFD modeling approach is presented to predict the performance of the gas admission valve system of a LNG fuelled engine, including the ability to predict the influence of pressure wave propagation on the outlet flows and performance. To achieve this goal, unsteady compressible turbulent flow was considered coupled with moving grid technique for representing axial vibration of moving plate. Another objective of this work was to understand the effect of frequency of moving plate on temporal variations of outlet mass flow rate and turbulent flow characteristics.
예연소실의 형상이 대형 천연가스 엔진의 연소 및 배출가스에 미치는 영향에 관한 수치적 연구
정수진(Soo-Jin Jeong),서석판(Seokpan Seo),문성준(Seong-Joon Moon),설동일(Dong-Il Seol) 한국자동차공학회 2022 한국자동차공학회 부문종합 학술대회 Vol.2022 No.6
Due to the environmental pressure and the prevailing political and economic situation in the world, alternatives to traditional fossil fuels are being sought. The use of natural gas may reduce the emission of pollutants and green house gas present in the ground vehicle and marine exhausts. Therefore, in this study, three-dimensional CFD model for PCSI fueled with LNG for eco-friendly marine engine has been developed by using various sub-models such as k-zeta-f turbulence model, ECFM-3z combustion model and hybrid-wall treatment. A research was undertaken into the effect of changing the orifice diameter and angle of orifice axis, which are key pre-chamber specifications. The results show that the smaller the orifice diameter, the earlier heat release begins. Particularly, this CFD model was used to optimize in-cylinder flow to generate high level of turbulence intensity near spark plug for very fast combustion speed, which results in reducing knocking. The results of this study show that reducing orifice diameter speeds jet flow, and it is likely that reducing the diameter of orifices causes the jets to reach further and the increase in heat release rate. It is also found that NOx emissions increase with an increase in pre-chamber volume and reduction in nozzle diameter.