2-Stroke Externally Scavenged Engines for Range Extender Applications 2012-01-1022

In this work, the authors assess the potential of the 2-stroke concept applied to Range Extender engines, proposing 3 different configurations: 1) Supercharged, Compression Ignition; 2) Turbocharged, Compression Ignition; 3) Supercharged, Gasoline Direct Injection. All the engines feature a single power cylinder of 0.49l, external air feed by piston pump and an innovative induction system. The scavenging is of the Loop type, without poppet valves, and with a 4-stroke like lubrication system (no crankcase pump).

Engine design has been supported by CFD simulations, both 1D (engine cycle analysis) and 3D (scavenging, injection and combustion calculations). All the numerical models used in the study are calibrated against experiments, carried out on engines as similar as possible to the proposed ones.

The strong points found for this family of engines are: high power density (up to 122 kW/l) and power-to-weight ratio; low raw emissions; compactness (design integrated with the electric motor); low production costs (no valve train, no EGR system); excellent balance of inertia forces (thanks to the piston pump installed on the same crankshaft, at 90° from the power cylinder); mechanical reliability (no exotic solutions, effective lubrication system); low noise (low engine speeds thanks to the double frequency of the cycle); low specific fuel consumption.