Investigations of the influence of mixture preparation on cyclic variations in a si-engine, using laser induced fluorescence

Bengt Johansson*, Hans Neij, Marcus Aldn, Greger Juhlin

*Corresponding author for this work

Research output: Contribution to conferencePaperpeer-review

43 Scopus citations


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 vapour 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 shown 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-0.8 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.

Original languageEnglish (US)
StatePublished - Dec 1 1995
Event1995 SAE International Congress and Exposition - Detroit, MI, United States
Duration: Feb 27 1995Mar 2 1995


Other1995 SAE International Congress and Exposition
Country/TerritoryUnited States
CityDetroit, MI

ASJC Scopus subject areas

  • Automotive Engineering
  • Safety, Risk, Reliability and Quality
  • Pollution
  • Industrial and Manufacturing Engineering


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