EFFECTS OF COMBUSTION CHAMBER GEOMETRY IN A DIRECT-INJECTION DIESEL ENGINE (COMPARISON OF RE-ENTRANT AND CONVENTIONAL CHAMBERS).

Two conventional combustion chamber types and a re-entrant type of direct-injection diesel engine were compared in order to investigate the effects of heat transfer and in-cyliner flow associated with the combustion chamber geometry on combustion itself, engine performance and exhaust gas emissions. Heat transfer calculation and heat release analysis have shown that the re-entrant chamber tends to reduce ignition lag due to the higher chamber wall temperatures. In-cylinder flow measurements using hot wire anemometry have indicated that the re-entrant chamber generates a higher turbulence level, particularly around the top dead center, causing an increase in the rate of heat release. Thus, the re-entrant chamber can favorably improve both fuel economy and smoke, even though fuel injection timing is retarded to reduce NOx emission.