Development of optimized exhaust gas heating strategies for passenger car Diesel engines by means of variable valve train applications

The cold start and heating phase of passenger car Diesel engines is essential to comply with the actual emission legislation targets. The HC and CO emissions that are produced immediately after a cold start contribute to more than 70 % of the total cycle results. The initially low temperature level of the exhaust gas aftertreatment system components results in a very low conversion efficiency. With a further strengthening of the emission legislation, the first phases of the emission test cycles will become even more important. It is aspired to achieve the required, even fast heat-up of the exhaust aftertreatment without fuel consumption penalties to reduce engine-out emissions efficiently. Application of a variable valve train system (VVT) can be an additional technology to address this challenge. The FVV research project No. 1171 “Potential of Valve Train Variabilities on Gas Exchange of Diesel Engines II” analyzes potential valve train variabilities systematically in terms of pollutants and CO2 emission reduction as well as to support the regeneration and heating behavior by experimental and computational investigations. Within the experimental investigations, an extended engine speed and load range is considered for a cycle relevant engine map. The impact of an exhaust cam phaser in combination with different intake cam lobe profiles is analyzed on a full-size engine by means of an extended DoE campaign. To identify the heating potentials of the VVT system the DoE model prediction results have been transferred to a mean value model and analyzed by cycle simulations. Combing the three different intake cam lobe profiles with an exhaust cam phasing, six promising heating strategies have been initiated.