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Pathway to 50% Brake Thermal Efficiency Using Gasoline Direct Injection Compression Ignition
Abstract:
Continued improvement in the combustion process of internal combustion engines is necessary to reduce fuel consumption, CO2 emissions, and criteria emissions for automotive transportation around the world. In this paper, test results for the Gen3X Gasoline Direct Injection Compression Ignition (GDCI) engine are presented. The engine is a 2.2L, four-cylinder, double overhead cam engine with compression ratio ~17. It features a “wetless” combustion system with a high-pressure direct injection fuel system. At low load, exhaust rebreathing and increased intake air temperature were used to promote autoignition and elevate exhaust temperatures to maintain high catalyst conversion efficiency. For medium-to-high loads, a new GDCI-diffusion combustion strategy was combined with advanced single-stage turbocharging to produce excellent low-end torque and power. Time-to-torque (TT) simulations indicated 90% load response in less than 1.5 seconds without a supercharger. For cold starts, the engine is equipped with a fast 2.5kW electric air heater positioned upstream of the intake valves. No spark plugs are used.
Dynamometer tests indicated excellent fuel efficiency over the operating map. Minimum BSFC of 194 g/kWh (BTE 43%) was measured at 1750rpm- 12bar IMEP with BSFC less than 210 (40% BTE) over a very wide operating region. The GDCI engine operates on US pump gasoline (RON91) and is ideal for down speeding and uploading for improved vehicle fuel economy. New simulations showed that potentially 48% BTE could be achieved through use of thermal barrier coatings and other improvements to the engine (Gen4X engine).
Vehicle simulations were performed at Argonne using the Gen3X engine map for a midsize sedan, SUVs, and a pickup truck. Results indicated a 36 to 51% improvement in combined FTP fuel economy over a competitive 2015 1.6L turbocharged GDi engine equipped with intake variable valve lift. The simulations showed that the Gen3X engine with 12V start/stop or mild hybridization can compete with full hybrid powertrains in various vehicle segments.