Realization of HCCI Combustion by Internal EGR using CI Engine with Variable Valve Timing System (First Report)

The purpose of this study is to cool the internal EGR (Exhaust Gas Recirculation) gas and form a uniform mixture by the injection of fuel into internal EGR gas. In previous studies, the internal EGR has a problem that high-temperature and low-density EGR gas flows into the cylinder and these causes the deterioration of fuel economy and exhaust emission performances [1]. In addition, internal EGR gas collides with fresh air tumble from the intake valves and, distribution of the in-cylinder oxygen concentration becomes heterogeneous. Additionally, the poor volatility of diesel fuel makes it difficult to achieve HCCI combustion in CI (Compression Ignition) engines. In order to resolve these problems, Fuel is injected into the internal EGR gas during the intake stroke. This injection cools the internal EGR gas by high latent heat derived from the promotion of fuel evaporation and equalizes the distribution of oxygen concentration in the cylinder. However, there are few studies on spray characteristics of diesel fuel at low pressure and high temperature conditions during intake stroke of fresh air and internal EGR. In this paper, the spray characteristics of diesel fuel at low pressure and high temperature conditions and the characteristics of in- cylinder inflow of premixed gas were investigated using numerical simulation.