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

Abstract

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 NOX and flue gas emissions decreased with decreasing VNT opening. When the opening of the EGR valve was in the range of 5%-10%, the NOX 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 NOX emission was significantly reduced by 6% overall, and the soot was reduced by 22.8% and the CO2 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.