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온도 성층화를 갖는 예혼합압축자기착화엔진에서 Booster 효과에 관한 수치해석
정동원(Dongwon Jeong),권오석(Oseock Kwon),임옥택(Ocktaeck Lim),박규열(Kyuyeol Park) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
The method of thermal stratification in cylinder is known for reducing rate of pressure rise, but which has its limit to extend the higher-load operating region of HCCI engines, giving an output of insufficient IMEP. High fueling rate could be one way to get the enough IMEP but it could be occurring engine knock. This work investigates the potential of in-cylinder thermal stratification for reducing the rate of pressure rise in DME HCCI engines, and the coupling between thermal stratification and booster effect to get reduced rate of pressure rise as well as high IMEP. The computations were conducted using Senkin application of the CHEMKINll kinetics rate code, and kinetic mechanism for Di-Methyl Ether (DME). DME has unique 2 stage reaction called Low Temperature Reaction (LTR) and High Temperature Reaction (HTR). Due to the heat release from LTR, the thermal stratification of in-cylinder would be formed just before HTR with large temperature difference so the heat release from oxidation reaction dispersed through combustion process. Intensity of intake pressure is closely concerned in input calorie which means a higher IMEP would be appeared without high fueling rate. The study also shows that increasing the in-cylinder thermal width of the charge between each zone would allow the booster pressure to be raised from 0.1㎫ to 0.18㎫ to get the higher IMEP as well as high thermal efficiency with low emissions.
Cooled EGR이 농도성층화가 존재하는 DME HCCI 엔진 연소에 미치는 영향에 관한 수치해석 연구
Soyol-Erdene,정동원(Dongwon Jeong),권오석(Oseock Kwon),임옥택(Ocktaeck Lim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Homogeneous charge compression ignition (HCCI) engines have the potential to provide both diesel-like efficiency and very low emissions of nitrogen oxides (NOx) and particulates. Before this potential can be realized, however, extending HCCI operation to high loads must be resolved by lowering the pressure-rise rate. For lowering the steep pressure rise rate occurred in high load, cooled exhaust-gas recirculation (Cooled EGR) and fuel stratification of pre-mixture in cylinder are recommended as one of the effective ways. Conduct numerical analysis to combination of cooled EGR and fuel stratification for confirming enhanced effect to lowering pressure rise rate, after indentifying each effect on extending HCCI operating ranges. Fuelling width in cylinder is φ=0.15 and CO₂ is used as a simulated cooled EGR. DME which has a characteristic of two-stage ignition is used as a fuel.
예혼합기의 성층화 상태가 DME HCCI 연소에 미치는 영향에 관한 수치해석 연구
정동원(Dongwon Jeong),Soyol-Erdene,권오석(Oseock Kwon),임옥택(Ockteack Lim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
It has been known from numerical analysis that HCCI combustion can be significantly affected by thermal and fuel stratification of the in-cylinder gas. With the same combustion timing (CA50), large thermal and fuel stratification tends to prolong the combustion duration and lower down the in-cylinder pressure-rise rate that make HCCI engines be operated at high load. Numerical analysis on pre-mixture having 40K thermal width with 0.15 fuelling width is presented for predicting the change of Pressure-rise rate and IMEP in four cases. Furthermore, comparing pressure traces of four cases with those of thermal stratification and fuel stratification. The fuel used, Di-Methyl-Ether (DME) which indicates two-stage auto-ignition has less cycle-to-cycle variation so that potentially can help effects of thermal and fuel stratification to expand operating range in DME HCCI engine.