New 1.5-Liter Hybrid Engine Development with High Brake Thermal Efficiency

<div class="section abstract"><div class="htmlview paragraph">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.</div></div>