2-Stroke Externally Scavenged Engines for Range Extender Applications

In this work, the authors assess the potential of the 2-Strokeconcept applied to Range Extender engines, proposing 3different configurations: 1) Supercharged, CompressionIgnition; 2) Turbocharged, Compression Ignition; 3)Supercharged, Gasoline Direct Injection. All the enginesfeature a single power cylinder of 0.49l, external air feed bypiston pump and an innovative induction system. Thescavenging is of the Loop type, without poppet valves, andwith a 4-Stroke like lubrication system (no crankcase pump).Engine design has been supported by CFD simulations, both1D (engine cycle analysis) and 3D (scavenging, injection andcombustion calculations). All the numerical models used inthe study are calibrated against experiments, carried out onengines as similar as possible to the proposed ones.The strong points found for this family of engines are: highpower density (up to 122 kW/l) and power to weight ratio;low raw emissions; compactness (design integrated with theelectric motor); low production costs (no valvetrain, no EGRsystem); excellent balance of inertia forces (thanks to thepiston pump installed on the same crankshaft, at 90° from thepower cylinder); mechanical reliability (no exotic solutions,effective lubrication system); low noise (low engine speedsthanks to the double frequency of the cycle); low specific fuelconsumption.