Reduction of NOX emissions and fuel consumption are the main topics in engine\ndevelopment, forcing the adoption of complex techniques and components, whose interactions\nhave to be clearly understood for proper and reliable operations and management of the whole\nsystem. The investigation presented in this paper aimed at the development of integrated control\nstrategies of turbocharging, high pressure (HP) and low pressure (LP) exhaust gas recirculation (EGR)\nsystems for better NOX emissions and fuel consumption, while analyzing their reciprocal influence\nand the resulting variations of engine quantities. The study was based on an extended experimental\nprogram in three part load engine operating conditions. In the paper a comparison of the behavior of\nthe main engine sub-systems (intake and exhaust circuits, turbocharger turbine and compressor, HP\nand LP EGR loops) in a wide range of operating modes is presented and discussed, considering open\nand closed loop approaches for variable nozzle turbine (VNT) control, and showing how these affect\nengine performance and emissions. The potential of significant decrease in NOX emissions through\nthe integration of HP and LP EGR was confirmed, while a proper VNT management allowed for\nimproved fuel consumption level, if an open loop control scheme is followed. At higher engine speed\nand load, further actions have to be applied to compensate for observed soot emissions increase.
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