Brake Configurations Impact on Particle Emissions for Heavy-Duty Vehicles with a Combustion Engine or Electric Drive trains

Sammanfattning

This thesis compares and highlights the different auxiliary brake systems present in heavy-duty vehicles and quantifies their respective effect on particle emissions. Exhaust emissions have been regulated in the EU for many years, thus today non-exhaust emissions have become the primary source related to road transport. By the first of January 2030, all new heavy-duty vehicles will have to be EURO-7 compliant. For the first time ever, emissions from other sources then exhaust will be regulated in EURO-7. These emissions are referred to as non-exhaust emissions and are; brakes, tires and road emissions. To achieve a strict but fair regulation, data need to be collected on the amount of particles that each use case produces. The complexity resides in the amount of brake configurations and use cases. In the first step of this study, the main heavy-duty vehicle brake systems and different auxiliary brake configurations are presented. The systems are explained and generic values for brake power are presented. Four use cases are evaluated, refuse collector and long-hauler with both ICE and BEV drivetrain, respectively. In the second step, the total brake energy and the auxiliary braking energy are determined for each use case. This results in a direct relation between auxiliary braking efficiency and airborne particles emitted. This is done for the different use cases to compare the different brake configurations. In doing this, a correlation between the use case and the auxiliary brake setup can be determined, as well as the efficiency of each setup. The conclusion is that for a single brake event that is considered representative for each application, the energy needed for the brake event is much higher for the long-hauler than for the refuse collector. When the mass of the particle emissions is calculated and the number of brake events is taken into account, it shows that the long-hauler emits less PM10 per km than the refuse collector, regardless of ICE or BEV. The auxiliary brakes of the BEV trucks are noticeably better at reducing particle emissions compared to ICE alternatives. This is mainly due to the fast response time of regenerative braking. However, if the battery is not in the right operating window, i.e. temperature and state of charge, the regenerative braking performance will be limited. The auxiliary brakes of an ICE truck are more dependent on the speed of the vehicle, which favors the long-hauler equipped with the retarder. The maximum brake power is also higher on the ICE alternatives, with the hydraulic retarder being the most powerful.