An Innovative Hybrid Powertrain for Small and Medium Boats

Hybridization is a mainstream technology for automobiles, and its application is rapidly expanding in other fields. Marine propulsion is one such field that could benefit from electrification of the powertrain. In particular, for boats to sail in enclosed waterways, such as harbors, channels, lagoons, a pure electric mode would be highly desirable. The main challenge to accomplish hybridization is the additional weight of the electric components, in particular the batteries. The goal of this project is to replace a conventional 4-stroke turbocharged Diesel engine with a hybrid powertrain, without any penalty in terms of weight, overall dimensions, fuel efficiency, and pollutant emissions. This can be achieved by developing a new generation of 2-Stroke Diesel engines, and coupling them to a state-of-the art electric system. For the thermal units, two alternative designs without active valve train are considered: opposed piston and loop scavenged engines. The design of the alternative engines is carried out through CFD simulations. The CFD has been calibrated and validated using experimental data from single-cylinder loop scavenged engine. The study demonstrates that the new Loop scavenged engine with a 23 kWh battery pack and an Opposed Piston design with a 15 kWh battery pack can meet the goals of the project while providing 5% and 10% fuel efficiency improvement at cruise conditions respectively, in comparison to the reference 4-stroke engine.