The effect of the variable geometry turbocharger(VGT) on fuel economy

emissions and combustion characteristics of a high pressure common rail diesel engine using straight diesel and biodiesel-ethanol-diesel (BED) fuel at different altitudes was investigated by an atmospheric pressure simulation system. Results show that the elevation of altitude leads to a deterioration

of fuel economy coupled to the reduction of nitrogen oxide(NOx) emissions and hence the increase of carbon monoxide(CO)

hydrocarbon(HC) and soot emissions. With the increase of the opening area of the turbocharger nozzle ring

the specific fuel consumption goes up. While the emissions of CO

HC and soot increase to varying degrees when using straight diesel and oxygenated fuel separately. In the high altitude area

the fuel economy of the straight diesel operation is better than that of the oxygenated fuel operation

but using oxygenated fuel can help apparently improve the emissions of CO

HC and soot. Under medium load conditions

the NOx emissions decreases first and then increase with the rise of the opening area of turbocharger nozzle ring. However

under high load conditions

the heat release rate and maximum cylinder pressure will fall with the increase of the opening area of nozzle ring

thus reducing the NOx emissions.