Effects and Models of Water Injection in an SI Engine
Downsizing and turbocharging is a popular combination nowadays in cars in
order to decrease the fuel consumption. However, the boost pressure increases
the risk of engine knock, limiting the engine in high-load operating points. In
the current engines, fuel is used to cool the engine in these operating points,
leading to a higher fuel consumption. Water injection is an effective method to
mitigate knock and enable a more aggressive ignition. It enables the engine to
produce more power and cools the exhaust, thereby protecting the turbocharger
and the catalyst from wear. In this thesis, the effects of injecting water in an
engine is investigated and a further development of a cylinder pressure model,
with a model that takes the water into account, is presented and validated. The
model can be used to estimate the cylinder pressure in several operating points.
Haris Subasic and Joel Westling
2018

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