Search Results

The effects of the directed port flow produced by a Charge-Motion-Control-Valve (CMCV) on mixture preparation in a Port-Fuel-Injection engine were assessed under conditions typical of fast idle in a cold start process. The port fuel was found to comprise two components: a “valve” puddle (at the vicinity of the valve) that built up quickly, and that was mainly responsible for the delivery of the fuel to the cylinder charge; a “port” puddle located significantly upstream. The latter was mainly created by the reverse back flow process and built up slowly. Although the fuel amounts in these two components were roughly the same, the latter did not significantly interact with the fuel transport to the cylinder charge. The CMCV only weakly affected the purging or filling time of the valve puddle, hence the dynamics of the fuel delivery process was not materially affected.

The interaction of intake port gas flow with the fuel spray in a port-fuel-injection engine is studied to see whether there are opportunities to facilitate the mixture preparation process and to improve the HC emissions through this interaction. The operating regime of interest is the fast idle period in a cold start. For single pulse injection, the HC emissions were not sensitive to injection details for closed-valve injection; emissions increased with open-valve injection. Then a split injection strategy was used in which the fuel was divided into two pulses. The first pulse was delivered during valve-closed; the second pulse was injected in the back flow period. Under cold-valve conditions, a small benefit (compared to close valve injection) was obtained with a second pulse fuel of 25%: 6% decrease in Specific HC emissions and 4.5% increase in the fuel delivery fraction.