抄録
Diesel engines have high thermal efficiency, but suffer from the problem of relatively high emissions of NOx and particulate matter. The authors have shown that NOx is mostly generated at the flame tip region where mixing strength decrease significantly and maintains high temperatures for longer times than other regions. Based on this assumption, the authors proposed a combustion concept to reduce NOx by introducing high turbulence in the combustion chamber during the combustion period. The present paper reports simulations of the turbulence intensity and NOx reduction for an engine, which is designed to generate a strong jet from a special cell. The cell, which is termed CCD in the paper, is added to a direct injection diesel engine, and a small amount of fuel is injected into the cell to create the strong jet entering the main chamber. The numerical simulations showed that NOx increased significantly by the jet from the cell, the opposite of the expected result. However it was shown that a significant NOx reduction was obtained when the jet was injected in the same direction as the fuel injection, showing the viability of the concept.
