22 Université Laval’s Team Alerion Supermileage soars above the collegiate

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How to Design
a Hyper-Efficient Car
Université Laval’s Team Alerion
Supermileage soars above the collegiate
engineering competition with a radical
vehicle capable of better than 3,000 miles
per gallon.
By Jim Anderton
E
ach year, Transport Canada tallies the country’s most and
least economical vehicles. For 2011, the winner is the
Toyota Prius, which delivers excellent fuel consumption ratings of 3.7L/100 km in the city and 4.0L/100km on the highway. The Prius is an engineering achievement, but it’s not the
most fuel-efficient vehicle in Canada.
That title goes to an extraordinary machine created by
engineering students at the Université Laval’s Team Alerion
Supermileage.
How efficient is their vehicle? The team competes in the
SAE Supermileage and Shell Eco-Marathon hypermileage
events for student engineers. The Quebec-based team does
more than compete; they win, consistently, with an advanced
gasoline-powered vehicle that has recorded fuel consumption
figures better than 1,300 km/L.
That’s over 3,000 miles per gallon. The numbers seem
impossible: 100 kilometers on less than 3 ounces of gasoline,
burned in a single-cylinder reciprocating-piston internal
combustion engine.
Team Alerion’s monumental achievement has resulted in a
swelling trophy case with three consecutive overall victories in
the SAE Supermileage competition, despite the fact that the
group operates at funding levels that are easily surpassed by many
of the US-based teams.
This year, the team beat second-place University of Ottawa
and 21 other collegiate competitors from across North America.
On April 19th, the team won the gasoline/internal combustion
class of the Shell Eco-Marathon Americas 2011 competition, also
for the third consecutive time.
May/June | 2011
So, how do they do it? Many of the details are a closely
guarded secret. Suffice it to say, the project contends with
numerous trade-offs and variables between engine, tires,
weight and aerodynamics. The most important factor in
designing a hyper-efficient vehicle, says team captain Anthony
Bernier, is all of the above.
“[The vehicle] has to be as light, efficient and as aerodynamically perfect as possible,” he says. “Some teams have a
good engine, but a weaker car, some great aerodynamics but
a poor engine. To win, you have to do everything.”
Start Your Engines
Converting the energy locked in fuels like gasoline into
mechanical work isn’t new technology. Nickolas Otto’s 1876
engine was revolutionary enough to make his name synonymous with four-stoke spark ignition technology, but it was a
refinement of previous designs. What made Otto’s engine
historic was its relative efficiency. Today, a full-tilt racing
powerplant might be 35 percent thermally efficient, while the
engine that spins a lawn mower blade can achieve little better
than half that figure.
Like all heat engines, energy (and efficiency) leaks everywhere
there’s a thermal gradient to ambient. Losses through hot
exhaust gases, heat transfer to cooling systems and to the air
in general conspire against super-efficiency.
Even if zero heat transfer were possible, keeping the engine
from literally melting is a problem that has never been completely solved. Add friction, plus the complex chemistry of
burning liquid fuels under pressure and the efficiency problem
is far from trivial.
Surprisingly, the team’s base engine is a 3.5 HP Briggs &
Stratton air-cooled single cylinder unit displacing 148cc’s,
like millions of similar units powering lawn mowers everywhere. It’s mandated by the SAE’s Supermileage competition
regulations. At 29 pounds, it’s a lightweight engine, but the
venerable flathead design is decades old. It’s about as basic a
starting point for high-technology development as possible
and is highly inefficient for performance use.
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“It’s very primitive,” Bernier bluntly states about the “spec”
engine. “We use only the aluminum crankcase. The rest we
throw into the garbage.”
Naturally, Team Alerion has made significant changes. In
the hypermileage league in which Team Alerion Supermileage plays no one leaves anything on the table, efficiency-wise.
The exact engine specifications are a closely guarded secret,
but Bernier did reveal that the engine uses a modified head
derived from a motor scooter while the cylinder is liner-ed
down to reduce the bore diameter. There are few photos of
the engine. That’s intentional, says Bernier.
“Until last year, we didn’t let anybody photograph it,” he says,
citing competitive secrecy. The few images available of the engine
show aluminized insulation blankets suggesting that the Laval
student team is damming heat in every way possible to extract
the maximum out of the fuel’s energy content.
The team’s modified cylinder head is considerably freerbreathing than the stock piece while the weak magneto ignition and carburetor fuel metering have been replaced with
modern ignition and fuel injection systems. Both are controlled
by microprocessor.
The engine runs on regular fuel—in SAE competition, it’s
pure iso-octane—which is less of a handicap than is generally
believed, since the anti-knock additives present in “highoctane” fuels do nothing to increase energy density. Clever
engineering of the cylinder head, combined with carefully
controlled fuel injection event timing and spark can deal with
pre-ignition.
The ragged edge of pre-ignition is where the engine spends
most of its operating life, effectively lugging at weak fuel/air
ratios to extract the most from every drop of fuel. Currently,
the engine is strictly metal, but the team is open to alternate
materials. “There are no ceramics in the engine,” declares
Bernier. “We looked at cylinder coatings last year…maybe in
the future.”
One interesting SAE rule requires that batteries produce
Lacking a wind tunnel, Team Alerion optimized their vehicle’s
aerodynamic performance in ProEngineer Wildfire (Creo Elements/Pro).
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Non-structural covers
Firewall
Reinforcement for the firewall
Structural monocoque chassis
Front wheels fixation composite panels
Composite panels used as
reinforcement for the system
Team Alerion’s vehicle shell presents a scant 0.285 square meters of
frontal area, a fraction of the frontal area of a Formula One race car.
no greater than 1.4A/h, requiring strict energy management
of ignition and instrumentation to avoid the need for a powerrobbing on-board generator.
“For the SAE competition, we used two batteries,” says
Bernier. “One for the ECU and support systems and one for
the starter. The electric starter is important because the engine
doesn’t run 100 percent of the time. We get running and,
when we reach a pre-determined speed, we turn off the engine
and coast.” The engine power output is a secret, but the lightweight car can achieve over 50km/h.
Rolling Resistance
Building an efficient engine is only part of Team Alerion’s
winning formula. Rolling resistance represents up to five
percent of a street vehicle’s energy loss, so the competition
vehicle uses every strategy, from razor-thin, very high pressure
and low-hysteresis tires to a tricycle configuration to remove
the energy-sapping and superfluous fourth wheel. Even the
team’s driver, first year undergrad Audrey Laine, is decidedly
petite. To win, every gram counts.
There are two key components in the driveline: a centrifugal clutch that allows engine idling and a free-wheel
overrunning clutch built-in to the drive hub. Final drive is
by chain and the disk brake system is powerful enough to
flat-spot the high-pressure tires through the cords.
Steering is Ackerman type by yoke with lots of negative
camber in the front wheels to reduce frontal area of vehicle. Beyond that, Bernier is tight-lipped. Other than the
Michelin low-rolling resistance tires, he states simply, “I
can’t tell you.”
Engineering a slippery shape
Aerodynamic drag is a major efficiency issue for all hypermileage teams. Team Alerion used clever engineering and careful
workmanship to craft an aeroshell that’s strong, light and
very slippery.
The design evolved from the team’s winning 2006/2007
vehicle and reduces an already small frontal area by 25 percent
to 0.285 square meters. A Honda Civic, by comparison, has
a 1.9 square meter figure, which is good by automotive standards. A Formula One race car has a frontal area of approximately 1.1-1.3 square meters, so the team is nearing the
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theoretical limits for a driver-enclosed volume. Skin friction was addressed with a minimal wetted area design,
while form drag was managed with a super-smooth surface
finish to minimize boundary layer separation.
Remarkably, the multiple award-winning final shape
was designed and simulated entirely “on screen,” with no
wind tunnel testing. Instead, the team designed the shell
and simulated performance completely within ProEngineer
Wildfire (aka Creo Elements/Pro), which consumed more
Canoe manufacturer, Kayaks St-Laurent, helped
the team create moulds and a fiberglass display
shell. The final carbon-fibre body weighs 11 kg.
than 100 hours of processor time to iterate
the shape into the optimal design.
The verified data was then exported to
MasterCam to generate the CNC-required
G-code for fabrication using a five axis
machining centre. Three weeks of effort,
with the assistance of Laval’s Centre de
Recherche sur le Bois, resulted in a precise,
segmented 385-kilogram wooden buck.
The polished buck was used as a positive
for team partner Kayaks St-Laurent to
fabricate a fiberglass/polyester resin mold,
from which a fiberglass/gelcoat display
shell and finally a carbon-fibre race shell
were laid up. The final, highly polished and
painted composite body weighs a scant 11
kilograms.
How long did it take to design and build
the car? Development is continuous and
evolutionary, so there’s really no start or
endpoint. By print time, Team Alerion
Supermileage will have competed in the
Shell Eco-Marathon Europe competition
in Lausitz, Germany against Europe’s best
collegiate engineering teams.
However, only one week away from the
team’s departure for Germany, Bernier
continued to work on an improved carbon
fibre body for the upcoming SAE contest.
“I worked on it yesterday,” Bernier said.
“We’re laying up the prepreg now.” He predicts significant improvements in the already
low frontal area figures with the new shell.
According to medieval geographers, an
alerion was a mythical legless and beakless
bird, but Team Alerion Supermileage must
seem more like a bird of prey to the student
competition. They have reason to boast, but
Laval’s Bernier says simply, “We do a lot
with a little.”
DE
www.alerionsupermileage.ca
May/June | 2011
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