DTNA’s SuperTruck II Separates the Sensible from the Doable – Gasoline Smarts
Daimler Truck North America revealed its SuperTruck II undertaking at Manifest 2023 in Las Vegas in early February. The main focus was on promising new applied sciences that might enhance real-world operational effectivity.
Photograph: DTNA
Daimler Truck North America unveiled its SuperTruck II undertaking in Las Vegas earlier this month. It doubles the freight effectivity of the baseline truck, a 2009 Freightliner Cascadia with a DD15 engine.
SuperTruck II builds on the learnings of SuperTruck 1, which wrapped up in 2015. DTNA’s SuperTruck 1 effort was a moon-shot of types, integrating some extremely superior know-how. SuperTruck II was a bit of extra grounded. It centered on extra promising core parts and techniques with real-world applicability — know-how that may very well be extra simply built-in in near-future generations of an over-the-road truck.
Chatting with reporters gathered for the reveal in the course of the Manifest Vegas 2023 present in Las Vegas, Derek Rotz, DTNA’s director of superior engineering, mentioned the group didn’t set out with a clear sheet to analyze each final nook of the car.
“We discovered on SuperTruck I which applied sciences confirmed promise for manufacturing and what didn’t,” he mentioned. “On SuperTruck II, we centered on what we imagine stands the most effective probability for manufacturing.”
Amongst these left within the basement this time round had been the waste warmth restoration system, the hybrid electrical drive, and vast use of carbon-fiber composite supplies for lightweighting.
Rotz mentioned the waste warmth restoration system proved to be too advanced and too heavy to offer tangible advantages, and it was tough to bundle on the chassis. The identical utilized to the high-voltage hybrid drive. And composites corresponding to carbon fiber are just too costly to offer a viable return on the fee.
“That’s a few of what we discovered from SuperTruck I,” mentioned Rotz. “This time, we determined to deal with different core areas as an alternative, like optimized aerodynamics, vitality administration, and powertrain effectivity.”
Optimized Aerodynamics
Daimler mentioned it achieved a 12% enchancment in aerodynamic effectivity with a redesigned hood, bumper and chassis fairings. The truck options energetic cab side-extenders and a roof spoiler system in addition to a digicam/mirror system. An energetic ride-height management system lowers the journey top by a few inches to shut the hole with the street floor and to decrease the general frontal profile of the truck.
Aerodynamic designers left no stone unturned in carving out an addition 12% drag discount. Even the doorways had been handled, on this case with skirts that stretch to the highest of the entry steps.
Photograph: Jim Park
“As a result of we dwell within the Pacific Northwest, there’s mountains throughout us, and we had been very a lot impressed by the best way the wind blows throughout surfaces like snow and sand really creating the right form,” mentioned the truck designer with the soul of a poet, Jeff Cotner. He’s the design growth supervisor at DTNA. “The wind will let you know the form that it desires the shape to be.”
The hood, bumper and chassis fairings on this truck had been designed to enhance the present cab construction and to permit air to stream undisturbed across the truck. The grille, air intakes and doorways had been redesigned to be as seamless and clear as attainable, with no sharp edges to compromise the aerodynamics.
The doorways bought a redesign, too. A skirt of types was added to the underside of the door that closes the hole between the door sill and the highest step. Darek Villaneuve, DTNA’s supervisor of superior car techniques, mentioned that addition considerably lowered noise contained in the cab, which is one other manner of claiming it lowered lots of air turbulence in that space.
Daimler’s Supertruck II additionally options energetic cab aspect extenders and a roof spoiler system that deploys at freeway speeds. These shut the hole between the cab and trailer to only 4 inches. “Aerodynamic Top Management” lowers the truck to only inches off the bottom for extra aerodynamic enhancements.
Gone from SuperTruck II are conventional mirrors. They’re changed by the MirrorEye digicam system with a proprietary digicam arm, once more, engineered with aero in thoughts.
Enhanced tractor aerodynamics, low-rolling resistance tires, powertrain enhancements and superior vitality administration had been recognized by DTNA’s designers and engineers as areas for innovation with quick pathways to commercialization.
Photograph: Jim Park
Powertrain Effectivity
Below the newly sculpted hood is a prototype Detroit 13L engine. It’s not licensed to any explicit emissions customary, as a result of that wasn’t among the many goals of this undertaking. The engine bought lots of consideration this time round, particularly with air dealing with and thermal administration.
It options two sequence turbochargers with an intercooler between them to chill the air exiting the primary turbo within the pursuits of accelerating volumetric density of the air coming into the second turbocharger. The intercooler is looped into what Daimler calls a cut up cooling circuit with excessive and low temperature loops. The low-temperature cooling circuit helps dissipate warmth from the exhaust fuel restoration (EGR) cooler and a few accent drives, whereas the high-temp aspect handles primary engine cooling.
Internally, a lot work was accomplished to cut back parasitic friction by means of using lighter-viscosity oil and friction-reducing coatings on varied surfaces.
“We had been making an attempt to make use of as little oil as attainable and use as little vitality as attainable to flow into the oil by means of the engine whereas sustaining its mechanical integrity,” mentioned Villaneuve. “We additionally went with a thermal barrier coating inside the combustion system, in piston heads, the hearth deck and the valves — completely different applied sciences on these issues, however we noticed fairly vital enhancements.”
The gasoline injection system was overhauled to get rid of mechanical losses whereas the injection strain was elevated to 2500 bar (36,000 psi).
Out again, Daimler is utilizing “adaptive tandem axles” that, with a clutch bundle positioned on the ahead differential housing, routinely shift from 6×4 to 6×2 at freeway speeds. This additionally permits for load biasing between the driving axle (entrance) and the would-be tag axle (rear) at freeway velocity. Coupled with a contemporary tire design from Michelin, Villaneuve mentioned the rolling resistance on the high-torque driving tires is lowered by shifting some weight to the extra-low-rolling-resistance tires on the tag axle.
DTNA’s SuperTruck II has a downsped driveline with a 1.75:1 ratio for an engine velocity of 950 rpm at freeway cruise velocity.
“We have now an enormous distinction in rolling resistance between the tag axle and the drive axle,” he defined. “With these applied sciences working collectively, we discovered there’s lots of synergistic results that actually have made an enormous, large enchancment.”
Additionally new on SuperTruck II is a prototype 13-speed transmission. Total, Daimler claims a 5.7% enchancment in gasoline consumption over SuperTruck I.
DTNA collaborated with Michelin on the event of latest tires particularly designed for adaptive tandem axles. The mannequin X M 586 tires scale back car vitality consumption and are mentioned to have distinctive put on traits.
Photograph: Jim Park
Vitality Administration
SuperTruck II includes a 48-volt electrical system with lithium-ion batteries, enabling electrical “energy” steering that adjusts demand as wanted at low or excessive speeds. The oil pump and starter motor are additionally 48 volts, as is the all-electric HVAC system. It’s a single-circuit AC system somewhat than the two-circuit system in use as we speak. This, Daimler claims, consumes 50% much less vitality than standard AC techniques.
Powering a few of these techniques electrically opens the door to true engine-off operation, which Daimler is looking EcoSail. If the truck is coasting down a hill whereas the engine is off, options corresponding to air con stay in operation. As quickly as energy is required, the engine will restart routinely.
“In testing EcoSail, on sure routes, we noticed a 30% working time when it was engaged and the engine was off,” mentioned Samantha Parlier, Freightliner model supervisor. “So, if I used to be making a 400-mile journey, over 100 miles of that may be going with none vitality.”
The 48-volt electrical system shouldn’t be with out its challenges, Rotz instructed HDT. Energy demand is barely rising, and there are a selection of apparent functions for 48 volts, however the design and engineering challenges might maintain it simply outdoors our grasp.
“There’s fairly a bit you are able to do electrically, however you must design for security, too,” he defined. “You need to think about the dangers for open circuits, quick circuits, and the chance of the 48-volt traces contacting with 12-volt traces.
“We didn’t discover the killer app for 48 volts on this undertaking. We discovered lots of minor advantages, like controlling the oil pump a bit of bit higher, and extra environment friendly operation of the AC system. They’re all little tiny bits and advantages. They only did not add collectively to get the financial savings that you must justify the fee.”
And he famous 48 volts will possible have a 5- to 10-year commercialization window, at which period demand may have shifted considerably towards totally electrical vehicles.
However that’s precisely what SuperTruck is all about. It’s a science undertaking on a grand scale. There are functions for all of the know-how right here, however a few of it may not pencil out right into a commercially viable product.
The SuperTruck program, co-funded by the Division of Vitality, goals to cut back emissions from on-road freight transportation by investigating next-generation applied sciences with attainable industrial functions. Doable is the operative phrase right here.
