Reduction of smoke and NOx emissions by active turbulence generated in the late combustion stage in D.I. diesel engine.

Abstract

The purpose of this study is to achieve simultaneous reduction in smoke and NOx emitted from diesel engines. Generally, there is a trade-off between smoke and NOx emissions, and a simultaneous reduction in both is difficult to realize. Generating strong turbulence late in the combustion period was attempted, to enhance smoke oxidation without disturbing the initial combustion stage where NOx formation is dominant. The turbulence was generated by jets of burned gas from an auxiliary chamber installed in a direct injection diesel engine. For the reduction of NOx, exhaust has recirculation (EGR) was combined with strong turbulence in the combustion chamber at a slightly retarded fuel injection timing. The experiments were very successful in reducing smoke in paticuler, as well as NOx. Thermal efficiency was improved at full loads. The paper describes the effect of various operating conditions and combustion chamber configurations.