Potential of additional mechanical supercharging for commercial vehicle engines

摘要

Modern commercial vehicle engines are equipped with turbocharging and intercooling. This results in low emissions and fuel consumption. In the lower speed and load range and under transient conditions, these engines have disadvantages, as the fuel injection rate has to be limited to avoid excessive smoke emission. Also, the engine braking performance of highly charged, small displacement engines is also lower than that of large displacement engines. Mercedes-Benz decided to develop a combination of turbocharger and mechanical supercharger. In the lower speed range higher torque levels are possible and maximum torque is available without any lag especially in the transient mode with low smoke emission and fuel consumption. Vehicle performance during acceleration can be improved by up to 30%. During engine braking operation, the mechanical supercharge is activated throughout the whole engine speed range which results is a distinctive increase in braking power. Possible vehicle performance with and without additional supercharging is discussed under fired and braking operation.