Improving Combustion Performance of a Dedicated Range-Extender Engine with Refined Intake-Charging Characteristics and Cooled EGR

Studies were carried out for improvement of combustion performance of an 1.2 L dedicated range-extender gasoline engine which uses a high compression ratio, cooled exhaust-gas-recirculation (EGR) and Atkinson cycle. The intake-charging characteristics were investigated both computationally and experimentally in order to compensate the torque reduction mainly due to the charge pushback in the Atkinson cycle. The design parameters of the intake manifold were refined to increase the intake air charges. 1D simulations were carried out to investigate the effect of the runner lengths and diameters. The results indicated that the increased length and reduced diameter could improve the volumetric efficiency in the most used engine speed range. Furthermore, computational fluid dynamics (CFD) simulations were employed to evaluate the cylinder-to-cylinder charging variations of the proposed manifold and reduced variations were obtained. Engine dyno experiments indicated that the engine volumetric efficiency was improved by 9.26% and 10.16%, and the corresponding power was raised by 1.40% and 3.05% under the engine conditions of full-load at 3200 rpm and 3600 rpm, respectively, which are consistent with the simulations. The effects of EGR on the engine fuel consumption were also evaluated. The experiments showed that the fuel consumption was improved at the most used operating conditions because EGR advanced the spark timings by mitigating knocking at the full engine loads. The improvements by EGR at the full loads range from 1.51% to 5.66%, and the maximum reduction of the brake specific fuel consumption (BSFC) is 14.8 g/kWh at 2000 rpm.

• Dedicated range-extender engine
• Charging characteristics
• Volumetric efficiency
• EGR
• Fuel consumption