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.
