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In this paper the performance of a new EGR cooler with double efficiency capabilities is presented. This device allows for temperature modulation between the actual cooled and non-cooled EGR temperature. The cooler has a double circuit in its interior controlled by a valve. The outer dimensions of the cooler remain the same as current fixed geometry coolers. The prototype has been characterized on test flow and thermal efficiency rigs and also tested on the engine test bed. Tests show that for steady partial load conditions little benefits may be achieved in CO and HC emissions with a small increase of NOx emissions. More promising results have been obtained during engine warm-up tests in which significant reductions of HC and CO are attained with low increases of NOx emissions. This shows a potential to reduce CO and HC emissions which are mostly generated during the first stages in the emission certification test in Europe.

Degradation of anti-pollutant devices must be taken into account in design so durability of the function is guaranteed over the vehicle lifetime. As for NOx reduction of diesel engines, Exhaust Gas Recirculation (EGR) systems are a well-known and robust solution. However, exposure of the EGR cooler inside this system to the exhaust gas conditions leads to a degradation of its function, affecting to the EGR rate and therefore to potential for NOx reduction. So, sizing and technology of these heat exchangers must be selected to avoid malfunction during vehicle operation. Current scenario in Europe with new homologation cycles and focus on NOx emissions of diesel vehicles under real driving conditions is challenging for the design of EGR systems. This leads to the increase of the areas of the engine map using EGR. Moreover new homologation includes also the use of low ambient temperature.