Development of a promising lambda=1 Two-Stroke scavenging concept

Nowadays, electric passenger cars are promoted to be the gamechanger for the existing climate crisis. But this not always corresponds to the expected CO2 reduction impact and especially not to the customers’ requirements and wishes.
One bridge technology to make electric vehicles more acceptable and usable for customers is the combination with a combustion engine. The hybrid technology is able to combine the advantages of an electrical drivetrain by reducing pollutant emissions in congested areas with the advantages of a combustion engine with high ranges and keeping the partly heavy and probably eco-unfriendly battery in an optimal size.
The technical demands lead to the use of a small, light and cost-effective internal combustion engine. One possible concept is the two-stroke engine, whereas the fulfilment of low emission requirements is one major challenge. As the exhaust aftertreatment system with a three-way catalyst needs a lambda 1 combustion concept, a two-stroke scavenging process with high trapping efficiency is required.
Different two-stroke scavenging concepts were studied with a focus on the above-mentioned boundary conditions using 1-D and 3-D CFD simulation. The most promising longitudinal scavenging concept was realized in 3D CAD and manufactured as prototype. As reference engine a classic loop scavenging principle was built with the same geometrical dimensions. Both engine types used the same crankshaft, conrod, piston and crankcase with the same oil, fuel and blower periphery system. Intense experimental investigations showed the potential of the novel engine concept both for low emission and low fuel consumption.
In this presentation the background and the decision process are explained together with the development of the prototype. Simulation and test bench results of the longitudinal scavenging engine are compared to the reference engine and an outlook about the next steps is given.