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소형 디젤 엔진에서의 250 MPa 고압 분사의 분무 특성 이해
배충식 ( Choongsik Bae ),조원규 ( Wonkyu Cho ),강승우 ( Seungwoo Kang ),김영호 ( Youngho Kim ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-
An experimental study was conducted to investigate the effects of ultra-high injection pressure on spray characteristics under light duty diesel engine operating conditions. An electronically-controlled ultra-high pressure fuel injection system was used to inject the diesel fuel. Six injection pressures were applied from 40 MPa to 250 MPa. The injection rate was measured by an injection rate meter using the Bosch tube method. Mie scattering and shadowgraph were performed to visualize the liquid and vapor phases of the diesel spray in a constant volume combustion chamber (CVCC) under evaporating conditions. The experimental results showed that the injection rate under high injection pressure of 250 MPa increased greater than 80%, compared to injection pressure of 80 MPa. Therefore, a large amount of fuel was able to be injected in a shorter time with higher injection pressure for high load operations. In the evaporating condition, liquid penetration and liquid spray area slightly decreased with higher injection pressures. It can be estimated that additional piston wetting would not occur at high injection pressure over 200MPa. Moreover, it seemed to increase the margin that can retard the injection timing for NOx reduction at higher injection pressure, because the time required to evaporate the liquid phase of the fuel and form a homogeneous mixture is shortened. At a higher injection pressure, vapor penetration increased sharply. At the same time (after the start of energizing), vapor/liquid area ratio increased with higher injection pressure. Based on these results, it is clear that high injection pressure can produce a more homogeneous air-fuel mixture in a shorter time. Further, this study also revealed correlations between spray development in a CVCC and the combustion process in a single-cylinder diesel engine.