Estimation of Nitrogen Oxide Emission Reduction in a Boosted Truck Diesel Engine with Two-Stage Charging and Miller Cycle

Power augmentation and reduction of toxic emissions, especially of nitrogen oxide (NOx), is a permanent challenge for internal combustion engines. Modern Euro-6 ecological standards for truck diesel engines have a very severe limitation of NOx emissions. To comply with it, a complicated and expensive SCR catalyst should be mounted. Using the Miller cycle may reduce considerably NOx emissions though in this case, the filling of engine cylinders with air drops dramatically which results in its power loss. Traditional charging systems with one turbocharger may not compensate for the cylinder filling degradation, therefore, two-stage charging systems are often used jointly with the Miller cycle which makes it possible to compensate for filling losses and obtain higher engine power. Operating parameters of a highly boosted truck diesel engine having a two-stage charging system with and without Miller cycle were forecasted using the AVL BOOST simulation complex. Turbochargers for the 1^st and 2^nd stages of the charging system were selected for the engine with and without the Miller cycle. Operation parameters of the diesel engine and its charging system were calculated. In case of the Miller cycle, the boost pressure was increased by 40% and emissions of NOx dropped by 50%. Power and fuel efficiency of the engine with and without the Miller cycle were close.