Study on the Optimized Matching of VNT and EGR Systems in a Diesel Engine

An experimental investigation of the coupling relationship between the VNT (Variable Nozzle Turbine) and EGR (Exhaust Gas Recirculation) systems was carried out in this study on a four-valve common-rail diesel engine in bench tests, as well as a transient optimization of the VNT and EGR control strategies. It was found that the overall level of NO X and flue gas emissions decreased with decreasing VNT opening. When the opening of the EGR valve was in the range of 5%-10%, the NO X and soot emissions could be reduced simultaneously by decreasing the VNT opening; the response of the intake volume was greatly improved by modifying the coordinated control strategy by boosting the control strategy under the acute load step condition; the NO X emission was significantly reduced by 6% overall, and the soot was reduced by 22.8% and the CO 2 emission was improved in the transient-optimized WLTC test cycle. Therefore, by coupling the VNT and EGR systems and optimizing them transiently, emissions of pollutants during rapid engine acceleration can be decreased.