Fuel and time optimized driving of heavy trucks with respect to Euro VI legislations

Abstract:   Saving fuel for heavy trucks travelling on a highway is possible by using the vechicles' weight and the knowledge about the road topography ahead. This can be done by a Look Ahead Cruise Controller. Such a controller can calculate an optimal driving strategy for the road segment ahead. The Look Ahead Cruise Controller is mostly used on an undulating road with a lot of up-and downhill slopes. Then the controller could increase the vehicle speed before an uphill or select the neutral gear and let the vehicle roll in a downhill slope in order to save fuel. Particle and nitrogen oxides can have a harmful effect on humans and since these are created in the combustion process of an engine, it is important to limit their presence in the exhaust gas. Therefore the Euro VI legislations are now in effect. They limit the number of particles and amount of nitrogen oxides that can be released from the vehicle. In order to meet these legislation demands the exhaust gas needs to be cleaned. Selective catalytic reduction (SCR) can be used to reduce the emission of nitrogen oxides. In order for the reduction to work as efficient as possible the catalytic substrate needs to have a high temperature. When the engine of a vehicle is working on a low engine speed and with a low torque demand, the exhaust gas temperature becomes low. This typically occurs when the vehicle is travelling in a downhill slope, either by rolling on neutral gear or rolling using engine brake. Thus the catalytic substrate is cooled, causing the catalytic process to slow down. A common way to avoid this is to let the engine work in a warming mode. However, this mode uses more fuel in order to heat the exhaust gas. The aim of this thesis is to find out if the cooling of the SCR substrate could have an affect on the optimal driving strategy found by the Look Ahead Cruise Controller.