Fuel Consumption and Emissions Effects in Passenger Car Diesel Engines through the Use of a Belt Starter Generator

Modern vehicles need to fulfil challenging requirements with respect to emissions, noise and fuel consumption. Up to the EU5 legislation a sound steady state application was sufficient for passenger car Diesel engines to meet these requirements, and fuel consumption was less in the focus than the emissions of nitrous oxides and soot, hydrocarbons and carbon monoxide. Future legislation will require not only tighter limits in emissions but additionally will set fuel consumption targets. More demanding drive cycles will make it even more difficult to achieve these targets. Additional to measures on the combustion engine, moderate electrification for energy recuperation as well as the supply of electrical generated torque to the drive train will increasingly find its way into modern passenger cars. The presence of an electric machine can be used not only to reduce the fuel consumption but also the emissions of the combustion engine. One such method may be the reduction of load peak of the combustion engine, the so-called “phlegmatisation”, especially during acceleration. Phlegmatisation means the replacement of torque from the combustion engine by torque from the electric machine during transients. It not only reduces the peak load but also decreases the dynamic demands on the “slower” engine controls, namely the air path, which cannot respond to changes in demand cycle by cycle like for example the fuel path or the ignition. The current paper reports on the application of this method. A 1.6 litre 4 cylinder engine was tested on an engine dynamometer, where the test bed brake was used to simulate the presence of an electric machine. Automated cycle driving was used at the Continental Regensburg Test Centre, to run various strategies in the World Harmonised Light Duty Test Cycle, WLTC, as well as in the New European Drive Cycle, NEDC. These results will be presented.