Investigations of the Influence of Mixture Preparation on Cyclic Variations in a SI-Engine, Using Laser Induced Fluorescence
Författare
Summary, in English
To study the effect of different injection timings on the charge inhomogeneity, planar laser-induced fluorescence (PLIF) was applied to an operating engine. Quantitative images of the fuel distribution within the engine were obtained. Since the fuel used, iso-octane, does not fluoresce, a dopant was required. Three pentanone was found to have vapor pressure characteristics similar to those of iso-octane as well as low absorption and suitable spectral properties.
A worst case estimation of the total accuracy from the PLIF images gives a maximum error of 0.03 in equivalence ratio. The results show that an early injection timing gives a higher degree of charge inhomogeneity close to the spark plug. It is also known that charge inhomogeneity gives a more unstable engine operation. A correlation was noted between the combustion on a cycle to cycle basis and the average fuel concentration within a circular area close to the spark plug center. The correlation coefficient when a second order polynomial was fitted reached a value of mA0.8 when the engine operated with a high degree of inhomogeneity. The highest correlation coefficient between the duration of 0-0.5% heat released and the average fuel concentration was obtained within a radius of approximately 5-10 mm from the spark plug. When the standard disc-shaped combustion chamber was replaced with a turbulence generating geometry, the inhomogeneity of the charge became very low, independent of injection timing. No cycle to cycle correlations between fuel/air equivalence ratio and combustion were then noted.
A worst case estimation of the total accuracy from the PLIF images gives a maximum error of 0.03 in equivalence ratio. The results show that an early injection timing gives a higher degree of charge inhomogeneity close to the spark plug. It is also known that charge inhomogeneity gives a more unstable engine operation. A correlation was noted between the combustion on a cycle to cycle basis and the average fuel concentration within a circular area close to the spark plug center. The correlation coefficient when a second order polynomial was fitted reached a value of mA0.8 when the engine operated with a high degree of inhomogeneity. The highest correlation coefficient between the duration of 0-0.5% heat released and the average fuel concentration was obtained within a radius of approximately 5-10 mm from the spark plug. When the standard disc-shaped combustion chamber was replaced with a turbulence generating geometry, the inhomogeneity of the charge became very low, independent of injection timing. No cycle to cycle correlations between fuel/air equivalence ratio and combustion were then noted.
Avdelning/ar
Publiceringsår
1995
Språk
Engelska
Publikation/Tidskrift/Serie
SAE Technical Paper Series
Fulltext
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Dokumenttyp
Konferensbidrag
Förlag
Society of Automotive Engineers
Ämne
- Atom and Molecular Physics and Optics
- Other Mechanical Engineering
Nyckelord
- Mixture Preparation
- LIF
- Laser Induced Fluorescence
- Cycle-Cycle Variation
Conference name
SAE International Congress and Exposition, 1995
Conference date
1995-02-27 - 1995-03-02
Conference place
Detroit Michigan, United States
Status
Published
ISBN/ISSN/Övrigt
- ISSN: 0148-7191