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! 2
743
KERO
Rotary engine technology takes off in general aviation
The EUREKA E! 2743 KERO project is driv-ing key Federal Aviation Authority (FAA) certification for Wankel rotary engines in general aviation. Swiss project leader Mistral Engines plans to supply a range of such engines for original equipment and retrofitting in all types of light airplanes and helicopters. Advantages include excellent reliability as there are few moving parts, a high power-to-weight ratio, compactness and smooth running compared with conventional piston engines. Moreover, the engine will run on widely available jet fuel. Oth-er potential applications include marine engines as well as light industrial ap-plications such as portable generators, compressors and pumps.
The four-stroke piston engine
technology used in the majority of light
airplanes involved in general aviation
dates back 60 years to the Second World
War. So, while designs are well proven,
motors require some 70 or 80 moving
parts and still run on 100-octane low-
leaded (100 LL) avgas fuel that has long
been displaced by heavier kerosene-
based jet fuel for commercial aircraft.
Moreover, 100 LL fuel is mostly limited
to North America and Europe; even
there it is becoming increasingly scarce
– and is soon to be banned completely
for environmental reasons.
Mistral Engines therefore saw a major
market for a safer, more reliable motor
that could be easily adapted to any
model of light aircraft and able to run
on industry standard jet fuel. The design
is based on the Wankel rotary engine
pioneered originally in Germany in
the 1930s but which emerged at the
wrong time. So far, it has only really
been developed and commercialised by
Japanese car maker Mazda in its RX-8
models and previous models.
Few moving parts
Safety and reliability are key factors in
aviation. The Wankel engine has a rotor
instead of reciprocating pistons, doing
away with any need for crankshafts,
pistons, valves and springs and reducing
the number of moving parts to only two
or three very robust ones. With so few
moving parts, the engine is extremely
reliable and safe. However, the rotary
engine is difficult to run in a fuel efficient
manner. Recently, the availability of
modern automotive electronics has
made it possible to overcome timing
and injection control complications,
resulting in fuel consumption similar to
that of piston engines.
Rotary engines for small planes are not
completely new. Many amateurs in the
USA have adapted car engines for this
purpose. It is actually a technology
particularly well fitted to aviation
applications. “We therefore decided
to take the Mazda rotary engine block
and to build an aero engine around it
that could be retrofitted to all aircraft,
explains Claude Geles, one of Mistral
Engines co-founders.
“Mounting an engine in an aircraft is a
delicate process and very expensive. We
also had to design a suitable gearbox.
Modern electronics now make it possible
to have exact timing for fuel injection
and ignition. The resulting engine looks
like a turbine; it is not really a turbine but
EUREKA labelling enabled us to find the 10 million euro in private equity financing that we needed to see the project safely through to a fully certified product ready for manufacture.
Claude Geles - Mistral Engines, Switzerland
Advances in combustion chamber design and electronic management systems are making it possible to develop a reliable rotary engine for small planes running on standard kerosene jet fuel
Shaping tomorrow’s innovations today
has many of its advantages, including a
very low level of vibration, it is light-
weight, compact and it is water cooled
– making it possible to change power
output very quickly without thermally
stressing the engine.”
Several partners involved
Several partners are involved in
the EUREKA project. The Ecole
Polytechnique Fédérale de Lausanne
(EPFL), where research was funded by
the Swiss Innovation Promotion Agency,
CTI, is studying the best combustion
conditions for the kerosene in terms
of combustion-chamber design,
injection and ignition. “We are also now
developing a special exhaust silencer
with the EPFL to limit the noise, using
active and passive noise- reduction
technologies able to work at very high
temperatures,” adds Geles. “This has
not been done before.”
The necessary electronic management
system was developed with French
partner DEM Electronique. The resulting
digital engine-control system features
full redundancy – essential for aircraft.
The heart of the system consists of
two separate computers which check
each other’s operations continuously.
In the unlikely event of one failing, the
remaining calculator immediately takes
over the entire engine management.
Full system redundancy extends to fuel
injectors and spark plugs.
Mistral Engines has been collaborating
with the Embry-Riddle Aeronautical
University in Florida, USA for flight
testing. The university will also help
in introducing the engine to the US
market. “We have had lot of discussions
with the FAA and we are certain that our
engines can be certified,” says Geles.
General aviation is presently in a high-
growth phase and is desperately looking
for new aircraft engine technologies.
About 65% of this market is in the USA
and the Americans are not developing
suitable new engines. The results
of KERO are expected to be already
marketable in 2010, as soon as FAA
certification is available. Petrol-fuelled
versions are already in production and
the kerosene version will use many of
the same parts. Parts are manufactured
by a range of companies, mostly in
Europe.
Labelling key to funding
EUREKA labelling played a key role
in obtaining funding for the Mistral
Engines’ development. “While we
managed to start the work with ‘pocket
money’,” explains Geles. “EUREKA
labelling enabled us to find the 10
million euro in private equity financing
that we needed to see the project safely
through to a fully certified product
ready for manufacture.” Most of the
technical problems have already been
overcome – one problem still being
tackled is pushing away the detonation,
or pre-ignition, limit. Nevertheless,
Geles predicts full FAA certification
within 18 months of the project ending.
The sky is then literally the limit!
We decided to take the Mazda rotary engine block and build an aero engine around it that could be retrofitted to all aircraft.
Project participants:Switzerland, France
Budget: 3.8 MEuro
Duration: 85 months
ContactMistral Engines S.AChemin Jacques-Philibert De Sauvage, 371219 Geneva, SwitzerlandClaude GelesTel.: +41 (22) 920 03 58 Fax: +41 (22) 920 04 09Email: [email protected]
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KERO
www.eureka.be