GDCI Multi-Cylinder Engine for High Fuel Efficiency and Low Emissions

A 1.8L Gasoline Direct Injection Compression Ignition (GDCI) engine was tested over a wide range of engine speeds and loads using RON91 gasoline. The engine was operated with a new partially premixed combustion process without combustion mode switching. Injection parameters were used to control mixture stratification and combustion phasing using a multiple-late injection strategy with GDi-like injection pressures. At idle and low loads, rebreathing of hot exhaust gases provided stable compression ignition with very low engine-out NOx and PM emissions. Rebreathing enabled reduced boost pressure, while increasing exhaust temperatures greatly. Hydrocarbon and carbon monoxide emissions after the oxidation catalyst were very low. Brake specific fuel consumption (BSFC) of 267 g/kWh was measured at the 2000 rpm-2bar BMEP global test point. At medium load to maximum torque, rebreathing was not used and cooled EGR enabled low-temperature combustion with very low NOx and PM, while meeting combustion noise targets. MAP was reduced to minimize boost parasitics. Minimum BSFC was measured at 213 g/kWh at 1800 rpm - 12 bar IMEP. Full load torque characteristics of the engine were developed using alternative injection strategies. Maximum BMEP of 20.3 bar was measured at 2000 rpm, with 17.4 bar BMEP achieved at 1500 rpm. Torque objectives for this engine were met. Transient cosimulations demonstrated the potential for good combustion control during hard accelerations and gear shift transients.