Commercial Vehicles: New Diesel Engine Concepts for Euro VI and beyond

The paper presents a numerical investigation, aimed to explore the potential of 2-stroke Diesel engines, able to meet Euro VI requirements, for application to medium size commercial vehicles (power rate: 80 kW at 2600 rpm, max. torque 420 Nm from 1200 to 1400 rpm). The study is based on experimental performance of a highly developed 4-stroke engine. Two different designs are considered: Loop and Uniflow scavenging, the latter obtained through an opposed piston configuration. In both cases, no poppet valves are used, and the lubrication is provided by a 4-stroke-like oil sump. The study started with the development of a 4-stroke EURO VI engine, on the basis of a previous EURO IV version. A prototype of the new engine (named 430) was built and tested. The second phase of the study consisted in the comparison to the 2-stroke configurations, considering the same performance and emissions targets, as well as the same constraints Engine outputs are calculated by using GT-Power models: while for the 4-stroke unit these results are fully supported by experimental data, the 2-strokes are just "paper" engines. However, the CFD-1D modeling was supported by other detailed numerical simulations, including both scavenging and combustion analyses. The two stroke concepts analyzed in the paper appear to yield several advantages, in comparison to their 4-stroke counterpart: reduced fuel consumption, cleaner combustion conditions, more compact dimensions, higher flexibility of the EGR control. On the other hand, they require a strong effort for the development of a specific combustion system.