Modern SI engines focusing on CO2 emission reduction has been
applying flex fuel technology to enable burning biomass fuels. The
prime route is the use of ethanol fuel on these engines. The action
of designing an engine to run with ethanol and gasoline
(Flex-Fueled Engines) affects powercell components in different
ways. The mechanical loads are higher to ethanol fuel. The
combustion pressure can be increased without the risk of knocking
for ethanol while for gasoline the compression rate of the piston
is limited due to knocking occurrence. The spark time also occurs
earlier which impacts components lubrication once the maximum load
happens near the top dead center (TDC) where the sliding speed is
lower and consequently there is lower oil film thickness. Such
combination of spark time and sliding speed may also affect
dynamics which can affect inertia and load composition of engine
components. The power density of engines running with ethanol is
also higher, which can impact on temperature, which also influences
the tribology of engine components. Another subject on ethanol is
its high corrosive characteristic, which is presenting flaking
mechanisms on components, rings for example, not existent on
gasoline engine.
In this way, this paper compares the effects of such different
engine characteristics given by ethanol fuel on engine components.
These effects are presented in a powercell approach evaluating the
interactions between piston, ring and cylinder. Microwelding and/or
abnormal groove wear on being dependent on the gas pressure, top
land height and ring material is also discussed. Ring and cylinder
wear are also affected by the gas pressure but even more on
lubrication effects. It is also evaluated the low friction trends
on powercell and its adaptations needed on Flex-Fueled Engines. And
it is discussed the harsher environmental effects given by
ethanol.
In this paper also presents the main recommendations on
powercell to best fit on current and future Flex-Fueled Engines
based on numerical simulation, bench tests and engine tests.