Impact of US02 and Euro4 Emission Legislation on Power Train Cooling Challenges and Solutions for Heavy Duty Trucks

Step by step US and European legislation are defining more stringent emission limits for diesel engines. Depending on these limits for NO_x and particulate emissions different emission reduction concepts including or excluding cooled exhaust gas recirculation (EGR) appear over time. Most probable cooled EGR will be the solution for US02 and, in combination with particulate traps, for many Euro4 applications. Competitive aftertreatment solutions like selective catalytic reduction (SCR) may need cooled EGR in addition to meet even tougher emission targets. Therefore cooled EGR can be assumed to be a long term task.

The impacts on the power train cooling system arise from the need of high performance EGR systems. This results in increased heat rejection from the EGR cooler and increased pressure and temperature loads on the charge air cooling system. At the same time overall fuel efficiency is becoming more important giving additional attention on the parasitic losses of the cooling system.

The paper presents the solution finding process beginning with maximizing the overall efficiency of the cooling system. So, the increase of the cooling air flow which must be reached with improved fan design and underhood air flow and which is connected with parasitic losses can be limited.

The investigations show that conceptional changes are needed to cope with these demands. Hereby, the most suitable cooling concept depends strongly on the truck manufacturers' targets.