Effects of VGT/EGR on Emissions from Diesel Engine

Abstract:

The effects of variable geometry turbine(VGT)/ exhaust gas recirculation (EGR) on pressure ratio, airfuel ratio, specific fuel consumption, and emissions of NOx, CO, HC, CO2 and smoke from a heavy duty diesel engine have been investigated. The results show that pressure ratio and airfuel ratio decrease, and fuel economy deteriorates with the increase of the opening of the EGR valve. NOx emission can be strongly affected by the opening of the EGR valve and VGT valve. NOx emission can be greatly reduced by increasing the opening of the EGR valve and VGT valve, and there is good logarithmic relationship between decline of volume concentration of NOx and the opening of EGR valve. However, HC, CO, CO2 and smoke emissions are increased. In order to lower NOx emission, while effectively controlling fuel economy and smoke emission, 50% of the opening of the EGR valve combined with 45% of the opening of the VGT valve is suitable at medium load, and 75% of the opening of the EGR valve combined with 55% of the opening of the VGT valve is suitable at high load.

Key words:heavy duty diesel engine; exhaust gas recirculation; variable geometry turbine; emission characteristics