Investigate the effect of EGR stratergies on the HCCI engine's performance with N-heptane fuel injection

In this study, the effect of EGR strategies on the HCCI engine's performance is studied. A program was established to control the injection fuel and amount of exhaust gas recirculation on the HCCI engine. The results of the research show that when the EGR rate is greater than 30%, the engine operates stably according to the HCCI combustion characteristic at speeds lower than 2400 rpm. But when engine speeds are higher than 2400 rpm, the HCCI combustion characteristic is unstable; the torque and the indicator efficiency decrease rapidly. When the HCCI engine increases the EGR rate, the start of combustion is gradually later, the coefficient gradually decreases to close to the black smoke characteristic curve, the CO, HC, and CO2 emissions increase. The NOx emissions tend to increase when the EGR ratio increases from 0–25%, but the NOx decreases when the EGR rate is greater than 25%.