|Homogeneous Charge Compression Ignition (HCCI) engines combine the advantages of both SI and CI engines. The direct injection used in HCCI engines allows higher compression ratios to be used than in conventional SI engines, which improves efficiency to levels comparable to CI engines. The very lean homogeneous air/fuel charge in the HCCI engine is burned volumetrically, which greatly reduces the in-cylinder temperature and in turn greatly reducing the production of NOx. The charge is also sufficiently well-mixed to reduce the production of soot (PM). A difficulty with HCCI engines is controlling the combustion process to allow HCCI operation over a wide range of speeds and loads.
In a series hybrid powertrain, the internal combustion engine is typically run at a constant speed to drive the generator. This makes it is possible to utilize HCCI engine in series hybrid powertrain, because it is difficult to control the torque and speed of an HCCI engine simultaneously. While integrating the HCCI engine into a serial hybrid powertrain, in order to increase the electrical power generated, the state engine speed and load should be increased. Thus in this research, several methodology are developed. According to the burning characteristics of HCCI engine, utilization of mixed fuel and external Exhaust Gas Recirculation (EGR) are realized, then the HCCI state speed and torque can be increased to 3000-4000 rpm and 5 Nm respectively, which upgrades the possibility of utilizing HCCI engine in serial hybrid powertrain.