Effect of VGT/EGR system on performances and emissions of heavy-duty diesel engine

A HOLSET 400 VGT turbocharger was applied on the CA6DL2-35E3 type heavy-duty common-rail diesel engine and a high-pressure-loop EGR system was set up.The performance tests of the engine with the VGT alone and the EGR/VGT respectively were carried out under the ESC test cycle.It is found that in the engine with VGT,there are always specific inflexions in the test objective parameter versus turbocharger control pressure(VGT vane position or opening) curves,and the VGT vane positions corresponding to the best engine performance all are in the nearby of the inflexion.So,it is possible to bring the potential of VGT into full play by the inflexion control to cut the emissions except NOx and improve the fuel economy.Using the strategy of EGR driven by VGT,an EGR rate as high as 28% can be achieved at 1330 r/min and 25% load.There are also inflexions in the test objective parameters(except NOx)versus EGR rate curves,and within the EGR rate corresponding to the inflexion,it is possible to cut the NOx emission by EGR without or with only a little penalty on other engine parameters,demonstrating a comprehensive potential to optimize the emission and economy performances of the diesel engine.