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염기태(Kitae Yeom),장진영(Jinyoung Jang),배충식(Choongsik Bae) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_1
Homogeneous charge compression ignition (HCCI) combustion is an attractive way to lower carbon dioxide (CO₂), nitrogen oxides (NOx) emission and to allow higher fuel conversion efficiency. However, HCCI engine has inherent problem of narrow operating range at high load due to high in-cylinder peak pressure and consequent noise. To overcome this problem, the control of combustion start and heat release rate is required. It is difficult to control the start of combustion because HCCI combustion phase is closely linked to chemical reaction during a compression stroke. The combination of variable valve timing (VVT) and gas fuel injection of high cetane number was chosen as the most promising strategy to control the HCCI combustion phase in this study. Regular gasoline was injected at intake port as main fuel, while small amount of di-methyl ether (DME) was also injected directly into the cylinder as an ignition promoter for the control of ignition timing. Different intake valve timings were tested for combustion phase control. Regular gasoline was tested for HCCI operation and emission characteristics with various engine conditions. This paper investigates the steady-state combustion characteristics of the HCCI engine with VVT, to find out its benefits in exhaust gas emissions. With HCCI operation, higher internal exhaust gas recirculation (EGR) rate and the longer combustion duration, reduced NOx emissions. However, hydrocarbon (HC) emission is relatively higher than that under sparkignition combustion.
예혼합 압축 착화 엔진에서 노킹 예측 및 배기 배출물 저감
염기태(Kitae Yeom),배충식(Choongsik Bae) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The knock characteristic and estimation in an engine were investigated under homogeneous charge compression ignition (HCCI) operation. Liquefied petroleum gas (LPG) and gasoline were used as fuels and injected at the intake port using port fuel injection equipment. Di-methyl ether (DME) was used as an ignition promoter and was injected directly into the cylinder during the intake stroke. A commercial variable valve timing device was used to control the volumetric efficiency and the amount of internal residual gas. Different intake valve timings and fuel injection amounts were tested to verify the knock characteristics of the HCCI engine. The ringing intensity (RI) was used to define the intensity of knock according to the operating conditions. The RI of the LPG HCCI engine was lower than that of the gasoline HCCI engine at every experimental condition. The indicated mean effective pressure (IMEP) dropped when the RI was over 0.5 ㎿/㎡ and the maximum combustion pressure was over 6.5 ㎫. There was no significant relationship between RI and fuel type. The RI can be predicted by the crank angle degree (CAD) at 50 CA. Carbon monoxide (CO) and hydrocarbon (HC) emissions were minimized at high RI conditions. The shortest burn duration under low RI was effective in achieving low HC and CO emissions.
Top-Feed Type 인젝터의 LPG 액상분사 적용성
염기태(Kitae Yeom),박정서(Jungseo Park),장진영(Jinyoung Jang),문석수(Seoksu Moon),배충식(Choongsik Bae),박정남(Jeongnam Park),김성근(Sungkun Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The injection and spray characteristics of Top-feed type injector was investigated under liquid phase injection fueled with liquefied petroleum gas (LPG). Different pressures and temperatures of fuel injection system were tested to identify the injection characteristics after hot soaking. MIE-scattering technique was used for verification of successful liquid phase injection after hot soaking. In case of Bottom-feed type injector, the injection was accomplished at every experimental condition. In case of Top-feed type injector, when the pressure of LPG was over 12 bars, the injection was not executed. The effects of temperature of fuel on fuel injector were little. However, under the pressure were 12 bars, the liquid phase injection after hot soaking was accomplished.
LPG 예혼합 압축 착화 엔진의 배기가스 및 연소 특성
염기태(Kitae Yeom),장진영(Jinyoung Jang),배충식(Choongsik Bae) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.4
This paper investigates the steady state combustion characteristics of LPG homogeneous charge compression ignition (HCCI) engine with variable valve timing (VVT) and di-methyl ether (DME) direct injection, to find out the benefits in exhaust gas emissions. VVT is one of the attractive ways to control HCCI engine. Hot internal residual gas which is controlled by VVT device, makes fuel is evaporated easily, and ignition timing is advanced. Regular gasoline and liquefied petroleum gas (LPG) were used as main fuel and di-methyl ether (DME) was used as ignition promoter in this research. Operating range and exhaust emissions were compared LPG HCCI engine with gasoline HCCI engine. Operating range of LPG HCCI engine was wider than that of gasoline HCCI engine. The start of combustion was affected by the intake valve open (IVO) timing and the λTOTAL due to the latent heat of vaporization, not like gasoline HCCI engine. At rich operation conditions, the burn duration of the LPG HCCI engine was longer than that of the gasoline HCCI engine. CAD at 20% and 90% of the mass fraction burned were also more retarded than that of the gasoline HCCI engine. And carbon dioxide (CO2) emission of LPG HCCI engine was lower than that of gasoline HCCI engine. However, carbon oxide (CO) and hydro carbon (HC) emission of LPG HCCI engine were higher than that of gasoline HCCI engine.