The hybrid engines produced by most original equipment manufacturers (OEMs) have
been modified to fit within the framework of conventional engine designs.
Recently, Geely has introduced a new 1.5-liter (1.5L) inline four-cylinder (I4)
TGDI engine, specifically designed to meet the requirements of its innovative,
efficient, and intelligent hybrid powertrain architecture. This engine achieves
an impressive brake thermal efficiency (BTE) of 44%, as well as high specific
torque at 153 Nm/L and high specific power at 67 kW/L. To attain this superior
performance, the following technical strategies were implemented: a high
compression ratio, the robust Miller cycle, an extended piston stroke-to-bore
ratio, an intake port optimized for high tumble, cooled exhaust gas
recirculation (EGR), and an advanced high-energy ignition system. Among these,
the middle four strategies, in conjunction with piston cooling jets and enhanced
exhaust-side cooling, all contribute to improved in-cylinder combustion. This,
in turn, effectively mitigates the potential for severe knock and pre-ignition
issues that can arise from the high compression ratio. Moreover, reducing
friction is a key factor in achieving the 44% BTE. When integrated into Geely’s
plug-in hybrid system, this new engine results in a 5.1% decrease in fuel
consumption under charge-sustaining conditions, as measured in the WLTC cycle,
when compared to the previous-generation engine.