http://lat.motorsport.com/f1/news/analis...i=43&tii=1
De Autosport,
F1 ENGINE TECHNOLOGY
Truck tech in F1’s V6s
SINCE THE INTRODUCTION OF THE
current engine formula in 2014, it has been
a challenge for engine designers to extract
power from limited fuel and fuel flow. But
a truck technology known as ‘pre-chamber
ignition’ is able to create power with a fuel/air
mixture inside the cylinder that is at an
almost-incombustible level. It is believed
to be at the heart of both the Mercedes
and Ferrari power units.
Inside a normal spark-ignition engine,
the fuel is injected into the space inside
the cylinder. When the fuel and air inside
the cylinder are compressed and ignited,
the mixture burns and expands to create
the power stroke of the four-stroke engine.
This works well until the fuel available
is limited, creating a lean fuel/air mixture.
This is hard to ignite with a single spark
plug, so the engine loses power.
With the current regulations, the fuel flow
is limited to 100kg/hour and fuel pressure to
500 Bar. With the high boost pressure and
rpm in an F1 engine, there isn’t the time to
get enough fuel in and mixed to get the right
fuel/air mixture for efficient combustion
This has limited the power output of the
generation of F1 engines, and what is needed
is a way to burn a leaner fuel/air mix, within
the regulations, which also demand a single
injector and spark plug.
Pre-chamber ignition occurs on large capacity
diesel engines. Efficiently filling
large cylinders for combustion of fuel and
air is difficult, so the problem gets divided.
A small chamber in the cylinder head is
created (the pre-chamber), which contains the
fuel injector and the spark plug. This is linked
through tiny connections to the cylinder below.
During the induction stroke, hot fuel
passes from the injector in the pre-chamber
into the cylinder. The cylinder is filled with
a lean fuel/air mix that forms a weak vapour
rather than a rich mixture.
The pre-chamber is then filled with a
richer fuel/air mixture just before the
compression stroke and ignition.
Combustion then occurs inside the
pre-chamber with the spark plug. This
mix ignites easily due to its rich nature,
the flame from this combustion then passes
into the cylinder and the multiple jets of
flame ignite the weaker mixture within.
As a result, the weak mixture is efficiently
burned, almost as though there are multiple
spark plugs inside the cylinder. More
importantly, the weak main-cylinder mix
burns faster, creating more power.
This design allows the engineers to run
very lean mixtures and still create power
within the tight combustion regulations, and
still using one single injector and spark plug.
Considering that this is a well-known
technology, it’s strange how F1’s cloak of
secrecy means this achievement is not
boasted about. F1 has reduced fuel
consumption by well over 30 per cent since
2013, yet the technological story is not told.
While engineers on the power-unit side are
all convinced that this technology is being
used, no team has openly admitted it.
Ferrari is known to have partnered with
Mahle to adopt its version of the prechamber
ignition, which is named ‘Jet’.
It is believed that the jump in engine
performance of the Italian organsation
this year is largely down to this.
Mercedes has experience of large
commercial engines, so its knowledge could
easily have come from within the group. At
last September’s Italian Grand Prix, Mercedes
made a well-publicised step in combustion
technology on its V6 engine and it is believed
by other F1 engine designers that prechamber
ignition was the step in question.
CRAIG SCARBOROUGH
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Un saludo