To meet future CO₂ emissions limits and satisfy the bounds set
by exhaust gas legislation reducing the engine displacement while
maintaining the power output ("Downsizing") becomes of
more and more importance to the SI-engine development process. The
total number of cylinders per engine has to be reduced to keep the
thermodynamic disadvantages of a small combustion chamber layout as
small as possible. Doing so leads to new challenges concerning the
mechanical design, the design of the combustion system concept as
well as strategies maintaining a satisfying transient torque
behavior. To address these challenges a turbocharged 2-cylinder SI
engine with gasoline direct injection was designed for research
purposes by Weber Motor and Bosch.
This paper wants to offer an insight in the design process. The
mechanical design as well as the combustion system concept process
will be discussed. First of all results of 1d simulations of the
engine are presented, which allow the choice of the optimal
combustion chamber geometry. Subsequently, the spray targeting of
the solenoid multihole high pressure injector as well as the design
of the intake runner geometry by means of 3d CFD tools is
presented. Further, the design of the optimal intake manifold setup
and gas exchange strategy will be described. The incorporation of
the results of this process and its impact on the design of the new
research engine is shown. Additionally, a special emphasis was set
on creating a very modular engine design, e.g., allowing a switch
between direct and port fuel injection and the implementation of
different boosting systems. DOHC was also implemented as an option
for an optimized gas exchange.
For analysis purposes the engine is operated at an engine test
bed using the standard measurement equipment including high and low
pressure indication. Additionally, an optical access to the
combustion chamber was realized which allows for high-speed color
recording of the working cycle.
First measurement results addressing the changes made to the
engine and combustion system concept design and their impact on
fuel consumption and the transient torque behavior will be
shown.