Pathway to 50 % Brake Thermal Efficiency Using Gasoline Direct Injection Compression Ignition (GDCI)

Authors

Mark Sellnau, Kukwon Cho, Yu Zhang, Dave Cleary, Aramco Research Center, Novi, MI, USA

Summary

Significant challenges face the powertrain market worldwide with the decline of lightduty diesel, the limited efficiency of spark-ignited engines, and the high cost of hybridelectric powertrains. Gasoline Direct-injection Compression Ignition (GDCI) has been developed over 8 years and has evolved into a practical powertrain with ultra-high efficiency and low emissions for stringent US and European RDE regulations.

In this paper, test results for the third generation Gasoline Direct Injection Compression Ignition (GDCI) engine are presented. The engine is a 2.2 L, four-cylinder, doubleoverhead-cam engine with compression ratio of 17:1 and features a wetless combustion system with a high-pressure injection fuel system. At low load, exhaust rebreathing was used to promote autoignition and elevate exhaust temperatures to maintain high catalyst conversion efficiency. For higher loads, a new PPCI-diffusion combustion strategy was combined with advanced single-stage turbocharging to produce excellent low-speed torque and power.

Dynamometer tests indicated unprecedented levels of fuel efficiency with minimum BSFC of 194 g/kWh (BTE 43.5 %) and BSFC less than 210 (BTE 40 %) over a very wide operating region. Vehicle simulation results for a midsize sedan indicated a 26.4 % reduction in fuel consumption on the US FTP drive cycle over a competitive 2015 1.6 L turbocharged GDi engine equipped with cam phasing and variable valve lift. For the Gen4X concept engine with 48 V mild hybridization, vehicle simulation results indicated potential for a 43.8 % reduction in fuel consumption over the sparkignited baseline. A life cycle analysis was conducted for a variety of fifty 2019 production
vehicles sold in the US market. Results indicated that life cycle CO₂ emissions for the Gen3X and 4X concept engines are comparable to the best battery electric and hybrid electric vehicles in the study.

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