Evaluation of an alternative Diesel combustion system for engine-out nitric oxide reduction

摘要

Engine-out NO{sub}x emission reduction potential of an alternative Diesel combustion system has been evaluated. Concept is based on reduced injector spray cone angle compared to conventional combustion systems in order to allow early injection timings for homogeneous combustion at low engine loads. Combustion system has to be optimized to provide convenient behavior from mid to high load in conventional combustion mode. Piston bowl, injector nozzle geometries and swirl level were optimized with help of 3D CFD simulation tools and engine test bench investigations. Near zero No{sub}x emissions were obtained up to 7 bars IMEP with adapted injection strategy without pilot injection and high EGR rate. Main drawbacks of such settings and combustion mode were quantified: combustion noise, hydrocarbon and carbon monoxide emissions, combustion control. Full load results show that the concept is able to reach performance level similar to current conventional combustion system.