SI Engine Control in the Cold-Fast-Idle Period for Low HC Emissions and Fast Catalyst Light Off

Abstract

The engine and its exhaust flow behaviors are investigated in a turbo-charged gasoline direct injection engine under simulated cold-fast-idle condition. The metrics of interest are the exhaust sensible and chemical enthalpy flows, and the exhaust temperature, all of which affect catalyst light off time. The exhaust sensible enthalpy flow is mainly a function of combustion phasing; the exhaust chemical enthalpy flow is mainly a function of equivalence ratio. High sensible and chemical enthalpy flow with acceptable engine stability could be obtained with retarded combustion and enrichment. When split injection is employed with one early and one later and smaller fuel pulse, combustion retards with early secondary injection in the compression stroke but advances with late secondary injection. Comparing gasoline to E85, the latter produces a lower exhaust temperature because of charge cooling effect and because of a faster combustion.

Effect of Operation Strategy on First Cycle CO, HC, and PM/PN Emissions in a GDI Engine

“…A well-known strategy for the reduction of engine-out HC emissions and fast catalyst warm-up during steady state operation consists of retarding of the spark timing [23,24,25]. Given the unique characteristics of the first combustion cycle, there was interest to examine whether this strategy was also applicable.…”

Reduction of Cold-Start Emissions through Valve Timing in a GDI Engine

“…This paper builds upon the findings and methodology of two previous studies on the 1 st cycle emissions and fuel pathway during cold cranking [5,6]. Additionally, it complements previous studies on emissions control through valve overlap [7], and through injection strategy [8,9].…”

“…The PM/PN data correspond to a 2.4 liters naturally aspirated GDI engine without a GPF [4]. The HC limit of T3B50 assumes the same HC/NOx ratio as the T2B5 standard This study is part of a wider effort undertaken at MIT to understand and mitigate the engine-out HC and PM/PN emissions during the coldstart phase [5,6,7,8,9]. This paper builds upon the findings and methodology of two previous studies on the 1 st cycle emissions and fuel pathway during cold cranking [5,6].…”

Cycle-by-Cycle Analysis of Cold Crank-Start in a GDI Engine

“…The effect of SOI on the mixture formation process and engine out emission has been studied in the past for the 1 st combustion cycle [9] and for the cold fast-idle period [22,23]. In this section the analysis is extended to the 2 nd and 3 rd cycles.…”