Influence of Injection Timing for Split-Injection Strategies on Well-Mixed High-Load Combustion Performance in an Optically Accessible Spark-Ignition Direct-Injection (SIDI) Engine

• DOI: 10.4271/2017-01-0657
• Publication Date: 2017-03-28T10:52:54Z
• Authors: Lewis Gene Clark; Sanghoon Kook; Qing Nian Chan; Evatt R. Hawkes
• Keywords: SPARK (programming language); Engine knocking; Ignition timing

One major drawback of spark-ignition direct-injection (SIDI) engines is increased particulate matter (PM) emissions at high load, due to wall wetting and a reduction in available mixture preparation time when compared port-fuel injection (PFI).It therefore necessary understand the mechanics behind strategies which are capable reducing these while also maintaining performance efficiency engine.Splitting fuel delivery into two or more injections proven way working towards this goal, however, many different permutations possible as such there no clear consensus on what constitutes an ideal strategy for any given objective.In study, effect timing first second evenly split dual investigated optical SIDI engine running 1200 RPM with unthrottled intake.Performance parameters derived from in-cylinder pressure data analysed alongside high-speed natural flame luminescence images order obtain relationships between output physical properties associated propagation.It was found that best performing consisted one relatively early intake stroke middle compression stroke, likely combination both ample formation level spray induced turbulence.Interestingly trends results significantly non-monotonic, series peaks troughs indicated mean effective (IMEP) combustion phasing (CA50) timings varied.The propagation were analysed, where it discovered speed very closely correlated CA50, regardless value IMEP.Additionally, elliptical approximation calculated each attempt establish link shape.It retarded lead less circular flame, potentially result decreased charge homogeneity causing local regions varied laminar throughout chamber.Furthermore, analysis eccentricity CA50 graphs suggest non-circular fronts.