Combustion engine concepts with extended expansion in hybrid powertrains

This work describes Gasoline engine concepts designed for the use within hybrid powertrains. By utilizing 0D/1D-simulations, three Extended Expansion engine concepts are investigated. With this alternative process, a significant increase in the expansion ratio while retaining the compression ratio is achieved, resulting in an increase in engine efficiency.The concepts are being derived from conventional turbocharged four-cylinder engines. The Atkinson concept has a Multi-Link cranktrain to provide an asymmetric piston motion. The Miller concept uses a valve train strategy with early inlet valve closure combined with a high stroke/bore ratio. In the 5-Stroke concept, the two inner cylinders are replaced by a large expansion cylinder. A post-expansion takes place in the expansion cylinder, thus extending the expansion phase.All concept-specific effects that influence fuel consumption are taken into account in the simulation. The simulated fuel consumption maps are subsequently used in a simulation of hybrid powertrains. A Mild-Hybrid with P2 topology and a Plug-In Hybrid with P2/4 topology are examined. The calculation of fuel consumption is based on driving cycles. The influence of the hybrid topology on the utilization of the engine’s sweet spot range is illustrated. It is shown that the P2/4 topology enables a significant increase of the mean effective engine efficiency during the driving cycle.