Truck & Off-Highway Engineering - August 2024 - 29

Q&
Detailing Kenworth's sleek SuperTruck 2
The Kenworth booth at the 2024 Advanced Clean
Transportation (ACT) Expo in Las Vegas garnered much interest
thanks to the reveal of its futuristic-looking
SuperTruck 2. Developed over a six-year period as part of
the DOE's SuperTruck program, the demonstrator vehicle
improved freight efficiency by up to 136% compared to the
2009 T660 model. The team improved fuel efficiency up to
12.8 mpg and reduced the combination weight by about
7,100 lb (3,220 kg) - 4,150 lb (1,880 kg) from the tractor and
2,950 lb (1,340 kg) from the trailer. The design led to a 48%
reduction in drag compared to
Kenworth's baseline vehicle.
A Paccar MX-11 diesel engine, rated at
455 hp (339 kW), is paired with a
Paccar TX-12 automated transmission
and a 48-volt electric generator, creating
a mild hybrid system to operate accessories
and provide engine-off " hoteling. "
The 48V generator also powers the
exhaust heater in an in-house-developed
close coupled aftertreatment system
that demonstrated CARB 2027
ultra-low NOx compliancy. TOHE interviewed
Joe Adams, Kenworth's chief
engineer, at ACT Expo to discuss the
SuperTruck 2 in more detail.
Can you break down the weight savings?
Chassis, front end and cab were the
three areas that we got the most weight
out. A fully composite cab, so we're not
using a metal structure there. That's a
significant part of the weight reduction.
And then redesigning that front end, we
were able to take hundreds of pounds
out of the design by narrowing the
overall axle so that we get enough
wheel cut [with the enclosed front
tires]. We spent a lot of time with that.
The way that we've designed our actual
frame structure also is a little bit unique
with the geometry that we have [reverse
splayed frame rails], and that was
a big part of the lightweighting. This new, creative front end
[allows] the engine to sit lower and behind the front axle, and
that also gives us a center drive position.
On the trailer, it really comes down to two main areas. The
side panels are all designed specifically in a lightweight
composite, and secondly, the kingpin area, which generally
has a large amount of mass there. We were able to redesign
that with lightweighting [in mind]. That's sizeable - the
whole combination tractor-trailer is about 26,100 pounds,
which is impressive.
TRUCK & OFF-HIGHWAY ENGINEERING
Are there any technologies developed for this truck that are
in production now or will be soon?
There are two key things. One is the digital vision mirror system.
We put that into production last year. The idea of that really
started out of the research here. It's not legal in the U.S. to take
the mirrors off the truck; the OEM can't sell it to you [that way].
There is a provision after I sell it to you that you then can take the
mirrors off as an operator with an exemption. In Europe you can,
so we introduced it there with our partners; DAF has the same
system in Europe without mirrors. Having no mirrors is probably
about a 4% aero improvement.
The second thing, it's not in production
today, but I can easily see the 48-volt system
that we have here being a big part of
the strategy needed for CARB and for
2027 EPA [NOx emissions] standards in
order to preheat the aftertreatment so that
it stays compliant either to 50-milligram or
35-milligram solutions, depending on the
year. It used to be that we had some minor
periods that we could exceed those limits
in a transient situation. The regulations no
longer allow those transient periods like at
startup when you have the cold aftertreatment.
So now we have to put a massive
amount of energy into the aftertreatment
at start so that we can stay compliant. So,
the 48-volt power generation system as
well as distribution on the vehicle is something
that we will see in future products.
Joe Adams, Kenworth's chief engineer.
" I can easily see the
48V system being
a big part of the
strategy needed for
[NOx] standards. "
What role will diesel electric hybrid
powertrains play in the future?
The EPA just came out with their Phase 3
greenhouse gas standards, which talk
about a pretty sizable reduction that we
have to introduce into the equation in
2027, 2028, 2029. As we look toward
that, hybrid powertrains I think will be
another option because there's a fairly
sizable savings in the fuel you're burning
by pulling the parasitic loads off.
We're looking at heavy hybrid applications
as well - something that you can drive 75 miles [with] zero
emissions. Some regions in the world, that makes a lot of sense.
For example, cities like Paris have said by 2035, zero emissions. So
you can drive diesel on the road, then click a switch and run zero
emissions in the city, drop your load, come back out of the city,
then run diesel to get to the next city. If we see that kind of duty
cycle needed [in the U.S.], the heavy hybrid is more suited for that.
Ryan Gehm
Go to www.sae.org/news to read more and see images.
August 2024 29
A
SAE/RYAN GEHM
http://www.sae.org/news
Truck & Off-Highway Engineering - August 2024

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