Potential of High Load Extension for Gasoline HCCI Engine Using Boosting and Exhaust Gas Recirculation

Homogeneous charge compression ignition (HCCI) still faces challenges in high load extension. In this paper, HCCI high load operation range was extended and combustion phasing was controlled by boosting combined with internal EGR and external EGR in a gasoline HCCI engine. Internal EGR was obtained by negative valve overlap (NVO) and used to achieve gasoline HCCI at ambient temperature without intake heating. Combustion phasing was optimized by adjusting the external EGR inducted into the intake system. The experimental results show that both boosting and EGR are effective means for HCCI high load extension but with limitations of peak pressure (Pmax), maximum rate of pressure rise (Rmax), combustion efficiency (ηc), and NOx emissions. Under the acceptable Pmax, Rmax, ηc, and NOx levels of a production gasoline engine, the achievable maximum IMEP is in the following order: external EGR, boosting, boosting combined with EGR. With increasing boost pressure, NOx emissions are significantly reduced. But with ...