The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing.
Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions.
As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.
Tests focusing on chemical effects with fuel blends having different aromatic and olefin contents were also conducted. The test results obtained under a completely vaporized condition showed that a test fuel with a high aromatic content displayed higher PN emissions under rich conditions than one with an increased olefin content.
Based on all the test results, it was concluded that in-cylinder behavior, such as the fuel film and a rich mixture, plays an important role related to the effects of fuel properties on PN emissions. The results suggest it is imperative to take into account not only the fuel chemical impact, but also the fuel physical effects associated with key in-cylinder behavior in order to simulate engine-out particulate emissions accurately.