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Preliminary Design of a Two-Stroke Uniflow Diesel Engine for Passenger Car
Abstract:
The target of substantial CO₂ reductions in the spirit of the
Kyoto Protocol as well as higher engine efficiency requirements has
increased research efforts into hybridization of passenger cars. In
the frame of this hybridization, there is a real need to develop
small Internal Combustion Engines (ICE) with high power density.
The two-stroke cycle can be a solution to reach these goals,
allowing reductions of engine displacement, size and weight while
maintaining good NVH, power and consumption levels. Reducing the
number of cylinders, could also help reduce engine cost.
Taking advantage of a strong interaction between the design
office, 0D system simulations and 3D CFD computations, a specific
methodology was set up in order to define a first optimized version
of a two-stroke uniflow diesel engine. The main geometrical
specifications (displacement, architecture) were chosen at the
beginning of the study based on a bibliographic pre-study and the
power target in terms. Using 3D CFD, the
expansion/scavenging/compression phases were computed in order to
evaluate the scavenging characteristic and the in-cylinder
aerodynamics level which mainly depend on the combustion chamber
geometry and on the intake and the exhaust manifolds and
strategies. The scavenging characteristic was then used in 0D
computations in order to evaluate each engine configuration in
terms of power and consumption on the entire engine map.
Indications were then deduced in order to guide the design office
for the engine optimization.
One configuration was chosen to be built and tested on the
test-bench. In the present paper the specific methodology is
described and several indications are given for the preliminary
design of such a two-stroke diesel engine.