Spark Assisted Gasoline Compression Ignition (SAGCI) Engine Strategies

Abstract

Gasoline Compression Ignition (GCI) is an engine-fuel technology which incorporates a combustion process using gasoline fuels in a compression ignition (CI) mode. GCI has the potential to offer high fuel efficiency while achieving ultra-low emissions. The objectives of the GCI engine development are to improve the fuel economy, meet the peak torque capabilities and comply with light duty emission regulations. The other key objective is to provide cost effective GCI engine design solution to automakers by minimizing the hardware complexity and maximizing compatibility with existing engine components. While GCI is under development for several years, there are several key technology risks (KTR’s) that need to be addressed. During cold start, the criteria pollutant emission is a challenge when the catalyst is not effectively warmed up. At low loads, misfires and partial burns lead to excessive HC and CO emissions. The increased pressure rise rate and particulate emissions are challenges at high load. The control challenges include transient Exhaust Gas Recirculation (EGR) control and combustion robustness control due to cycle to cycle stability needs. Furthermore, the fuel injection system durability and boosting system capabilities are required to be demonstrated. This book chapter presents strategies to address those KTR’s at different engine operating conditions. The engine is based on a gasoline engine architecture with a spark plug and high pressure gasoline fuel injection system, termed as spark assisted gasoline compression ignition (SAGCI) engine. The results reported in this chapter are specific this particular hardware configuration of GCI engine fueled by RON 91 gasoline. During cold start, a split fuel injection strategy with extremely retarded spark timing is proposed to rapidly warm up the catalyst and minimize the criteria emissions. At low loads, typical spark ignited (SI) combustion and spark assisted GCI strategies are preferred. During GCI operation at low loads, spark is enabled as a supplemental means for robust combustion control. GCI based on partially premixed compression ignition (PPCI) strategy is preferred at medium loads to meet the emission targets. Cold EGR, re-breathing and different fuel injection strategies are used as control variables to ensure better combustion control. The high load GCI is based on diffusion combustion with optimum fuel injection strategy that targets to reduce the pressure rise rate and soot emissions.KeywordsTransportFuel economyRegulationsGasoline Compression Ignition (GCI)Spark assisted GCICold startLow load stability and high load combustion noise