INVESTIGATION ON THE INFLUENCE OF EXHAUST GAS RECIRCULATION ON PERFORMANCE OF HOMOGENEOUS CHARGE COMPRESSION IGNITION (HCCI)

Environmental pollution and energy constraints have made engineers research a new method of ignition in the internal combustion engines. Also, the automotive industries are searching to replace SI and CI engines due to the strict regulations of international organizations actives in the eld of environment. (HCCI) is a suitable method for combustion in SI and CI engines. The HCCI engine uses a premixed air/fuel mixture that is pressed with high compression ratio. In the research, a CFD model has been used for the analysis of HCCI engine. In order to validate the model, we used the experimental results obtained from Dutez engines with Methane fuel and a secondary fuel injection diesel in 270oCAD position. Investigation showed that concordance between the model and experimental results is acceptable. Maximum cylinder pressure decreases with the increase of EGR. With an increase in EGR percentage, the rate of carbon black increases which it results from the incomplete combustion. Therefore, performance of EGR is acceptable within a certain range. Also, an increase of EGR reduces cylinder temperatures. Incomplete combustion causes a part of the air/fuel mixtures to leave the cylinder without participating in the combustion process. As a result, those parts of the air/fuel mixtures leave the cylinder without producing thermal energy. Increase of EGR rate reduces the amount of heat release due to incomplete combustion, but heat release increases even despite non-combustion. This performance is due to the increase of temperature which, in turn, causes the increase of cylinder density. As a result, heat release is produced even despite non-combustion. It is noteworthy that maximum heat releases occur under non-EGR condition. Change in the heat release rate regarding dierent EGR rates shows that the combustion occurs in dierent positions. The increase of EGR greatly reduces NOX emissions. So, EGR system can provide adequate eect on reducing NOX emissions.