抄録
In order to realize a low compression ratio diesel engine, the problematic points, for example the engine noise resulting from the maximum rate of pressure rise and exhaust emission (NOx), have to be improved. In this paper, the auxiliary fuel injection was tried using a direct injection type engine for improving the problematic points stated above, and further some factors which affected the effects of the auxiliary fuel injection, for instance the combustion chamber configuration and the compression ratio, were discussed. As a result of our experiments, the auxiliary fuel injection in a low compression ratio engine was found a favorable means of suppressing the emission of noise and NOx, and in this case the optimum timing of auxiliary fuel injection was near the top dead center of exhaust stroke, i.e. Vigom injection, with respect to specific fuel consumption and noise emission. On the effects of auxiliary fuel injection, especially with respect to improving the maximum rate of pressure rise, the extent of the effects of auxiliary fuel injection was intensive, as the injection rate of the main injection was large and the turbulence in combustion chamber was strong. Besides, on the relationships between the compression ratio and the effects of auxiliary fuel injection, the efects of auxiliary fuel injection were intensitve at lower compression ratio with respect to the maximum rate of pressure rise and noise emission. Consequently, the adoption of auxiliary fuel injection in a low compression ratio engine might be very effective.
