Analytical Approach to Characterize the Effect of Engine Control Parameters and Fuel Properties on ACI Operation in a GDI Engine

Advanced compression ignition (ACI) operation in gasoline direct injection (GDI) engines is a promising concept to reduce fuel consumption and emissions at part load conditions. However, combustion phasing control and the limited operating range in ACI mode are a perennial challenge. In this study the combined impact of fuel properties and engine control strategies in ACI operation are investigated. A design of experiments method was implemented using a three level orthogonal array to determine the sensitivity of engine control parameters on the engine load, combustion noise and stability under low load ACI operation for three RON 98 gasoline fuels, each exhibiting disparate chemical composition. Furthermore, the thermodynamic state of the compression histories was studied with the aid of the pressure-temperature framework. Due to the compression ratio constraints imposed by knock limited SI operation, considerable intake temperature heating was required and ACI operation resulted in the intermediate to high temperature autoignition regime. The olefin containing fuel was found to be most sensitive to intake air heating, thereby enhancing its potential suitability for ACI operation, while still enabling high load SI operation.