15권 1호 193-200 2007 [한국자동차공학회 논문집 ]
| 제목 | 직분식 CNG 엔진에서 연료 분사시기의 변화가 연소 및 출력 특성에 미치는 영향 |
|---|---|
| 분야 | 전기동력자동차 |
| 언어 | Korean |
| 저자 | 강정호(쿄토대학), 이중순(동명대학교), 박종상(교토대학), 하종률(동아대학교), 윤수한(동명대학교) |
| Key Words | Key words:직접분사(Direct Injection), 압축천연가스(CNG), 균질혼합기(Homogeneous Mixture), 성층급기(Stratified Charge), 배기배출물(Emission), 분사시기(Injection Timing) |
| 초록 |
Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including CO2, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, CO2 and NOx. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the DI CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the DI CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition. |
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