Daimler Trucks NA SuperTruck achieves 115% freight efficiency improvement over 2009 baseline; 50.2% engine BTE
|DTNA’s SuperTruck was unveiled at the 2015 Mid-America Trucking Show. Click to enlarge.|
Daimler Trucks North America’s (DTNA) SuperTruck program has achieved 115% freight efficiency improvement (gallons of fuel consumed per ton of goods moved per mile traveled)—surpassing the Department of Energy (DOE) program’s goal of 50% improvement and exhibiting the best results of all reporting OEMs. (Earlier post.) DTNA unveiled its SuperTruck at the 2015 Mid-America Trucking Show (MATS) in the Freightliner Trucks booth.
To measure freight efficiency, DTNA ran vehicle testing on highway routes in Oregon and Texas; one city route in Portland, Ore.; and anti-idle testing in both a cold chamber and hot chamber. These tests resulted in the combined 115% freight efficiency improvement over a 2009 baseline truck. Testing was also conducted at the DTNA Detroit engineering facility to demonstrate engine efficiency by achieving 50.2% engine brake thermal efficiency.
The final SuperTruck demonstrator ran a five-day, 312-mile (502-kilometer) roundtrip route on Texas Interstate 35 between San Antonio and Dallas, at a weight of 65,000 lbs (29,484 kg) GVWR at a speed of 65 mph (105 km/h), where it achieved an average result of 12.2 mpg (19.26 l/100 km).
We are thrilled with the positive results, and are honored to have been part of the program. It is our expectation that we will continue to review and refine what we’ve learned and achieved over the course of the SuperTruck initiative, and use that knowledge to bolster our leadership in fuel efficiency.—Derek Rotz, principal investigator for SuperTruck, Daimler Trucks North America
|DTNA SuperTruck technology elements. Click to enlarge.|
Powertrain. The Freightliner SuperTruck uses a downsized and downsped 10.7-liter engine, a hybrid system, a Waste Heat Recovery (WHR) system, along with a number of other upgrades.
The 390 hp/1400 lb-ft torque (291 kW/1,898 N·m) engine features a revamped combustion system. To achieve the highest efficiency possible, engineers increased the compression ratio, ran extensive tests on piston and injector combinations, and pushed each engine component to its limit.
Friction-reducing measures include a variable speed water pump, a clutched air compressor, low-viscosity oil and an improved cylinder kit. To further reduce friction, the cylinder liners were optimized to reduce drag in the mid-stroke, where piston speeds are highest.
The SuperTruck uses a unique prototype control system, capable of optimizing engine performance in real time for maximum fuel efficiency. The controller continuously monitors the engine’s operating conditions as well as the external environment, and uses an on-board computer to determine the most efficient course of action during real-world operation.
The Freightliner SuperTruck features a low-back-pressure, next-generation aftertreatment system that efficiently removes NOx from the exhaust stream. This ensures the air coming out the tailpipe stays clean, while freeing up the engine to run more efficiently at higher temperatures and pressures.
Working in conjunction with Daimler Advanced Engineering, the team developed an innovative organic Rankine cycle (ORC) waste heat recovery (WHR) system that converts a portion of the exhaust heat into usable energy.
The aftertreatment system features additional insulation to retain maximum heat energy in the exhaust. These exhaust gases pass through a boiler which transfers heat to the working fluid, which vaporizes to high-temperature steam and builds up pressure. High-temperature, high-pressure steam then passes through an expansion machine, which recovers the usable energy.
After expansion, the medium-temperature, low-pressure steam circulates to the condenser, where it liquefies. The liquid is then pumped back into the boiler to recover more heat.
DTNA notes that while Waste Heat Recovery is an innovative SuperTruck technology, challenges remain in the areas of vehicle and engine integration tradeoffs, working fluids, and cost and maturity.
A hydraulic fan eliminates frictional losses generated even when the fan is off by belts, pulley, bearing and seals and spins the fan at precisely the speed needed to cool the engine.
Using GPS and 3D digital maps, the Integrated Powertrain Management System controls the SuperTruck’s vehicle speed, shifting and eCoast. The SuperTruck also incorporates Predictive Hybrid Control, which optimizes hybrid battery-charging strategies to the terrain of the road ahead.
The SuperTruck’s hybrid system takes kinetic energy generated from downhill braking to charge its battery. Making the system even more efficient, eCoast technology senses downgrades or when the truck is about to crest a hill, and automatically shifts the drivetrain into neutral. This reduces friction, and increases efficiency and fuel economy.
The SuperTruck’s AC system runs entirely off the electricity powered by the hybrid system. Drivers can run the AC for more than an hour without turning the engine on, resulting in significant reductions in fuel consumption.
Solar panels run the length of the top of the SuperTruck’s trailer, helping to charge the hybrid battery, which in turn powers the eHVAC system. On a sunny day, the panels can provide enough energy to run the AC system continuously without the engine running.
|Phase 2 standards for medium- and heavy-duty GHG emission standards|
|Staffs of the US Environmental Protection Agency (EPA), National Highway Traffic Safety Administration (NHTSA), and California Air Resources Board (ARB) are working on the next phase of greenhouse gas emission standards for medium- and heavy-duty vehicles, referred to as Phase 2.|
|These standards are expected to build on the improvements in engine and vehicle efficiency required by the Phase 1 greenhouse gas emission standards, and provide an opportunity to achieve further greenhouse gas reductions for 2018 and later model-year heavy-duty vehicles, including trailers.|
|US EPA and NHTSA are planning to issue a Notice of Proposed Rulemaking for the Phase 2 standards in the spring of 2015 and a final rule in the spring of 2016. Upon federal adoption of the Phase 2 standards, ARB staff plans to present a proposed California Phase 2 program to the Board, most likely in late 2016 or 2017.|
Chassis. The truck chassis was redesigned as well. The frame rails uses fewer crossmembers, thereby delivering added weight savings, simplified crossmember construction and better use of lighter-weight materials. This, combined with the lightweight rear suspension, reduces frame weight by 700 pounds (318 kg).
The AccuSteer power steering and air system with a hydraulic accumulator reduce overall energy consumption by more than 1%. On standard systems, the air compressor and power steering pump run continuously, whether they’re needed or not. The SuperTruck incorporates a clutch to switch these parasitic loads off when not needed, which, according to testing, is more than 90% of the time.
Detroit rear axles were upgraded for the Freightliner SuperTruck. In addition to using lighter-weight components where possible, the axle configuration, oil level management system and even the oil formulation itself are optimized to reduce friction and increase efficiency.
Aerodynamics. The basic shape originated as a 3D computer model, which was carefully honed by aerodynamicists using digital wind. Together, the optimized tractor and trailer design achieved a 54% reduction in aerodynamic drag.
The overall ride height can be adjusted, raising the chassis for extra ground clearance at low speed for maneuverability and lowering it at highway speeds to reduce drag.
An active grille stays open in low-speed, high-torque situations to maximize cooling flow. At highway speeds, it automatically closes, improving aerodynamic efficiency.
The windshield is raked backward to guide air more efficiently over the hood and cab, moving over the truck with less drag.
Optimized side extenders shield cab components as air glides from tractor to trailer.
The SuperTruck’s wheel fairings divert air past the rear wheels and tires, and articulate for easy serviceability.
Several commercially viable technologies developed in conjunction with the SuperTruck program have been introduced in DTNA production vehicles, including 6x2 optimization and the aerodynamic components found on the Freightliner Cascadia Evolution and the integrated Detroit Powertrain. Other components, due to regulatory or economic barriers, may not be commercially viable in the near future.
By incorporating a mix of available technologies with future innovations, we were able to use the SuperTruck program to take the first steps in seeing what may be technically possible and commercially viable. We still have a long road ahead to determine ultimately what will be successful and what will achieve the greatest efficiencies.—Derek Rotz
Sponsored by the US Department of Energy (DOE), the SuperTruck program was a five-year research and development initiative to improve freight efficiency by at least 50%, brake thermal efficiency by 50%, and reduce fuel consumption and greenhouse gas emissions of Class 8 trucks. DTNA and three other major truck OEMs were awarded multi-million dollar grants by the DOE and each matched the DOE funding dollar for dollar.
SuperTruck is supported by the US DOE under the American Recovery and Reinvestment Act of 2009. DTNA began work on the SuperTruck program in 2010 together with Detroit and other partners, including national labs, universities and suppliers. Partners included:
Aftertreatment: Corning, Eberspacher, Johnson Matthey.
Aero/cooling: Auto Research Center, CD-adapco, Freight Wing, Lang Mekra, Modine, TitanX, Truck-Lite.
Engine: Air Squared, Aradex, Atkinson LLC, Bowman, Daimler, Gigatronik, Massachusetts Institute of Technology, Oak Ridge National Laboratory, Obrist.
Powertrain: Accuride, Ashland, Bendix, ConMet, Detroit, Michelin, Parker, Sheppard.
Hybrid: A123 Systems, Eaton, FUSO, ITK Engineering, Mercedes-Benz, MiaSole, US Hybrid.
Energy Management: Delphi, Denso, Grakon, Guardian, National Renewable Energy Laboratory, Oregon State University, Telogis, US Department of Energy.
Fleet: Schneider, Walmart
Lightweighting: MSI-ACPT, Maxion Inmagusa, Oregon State University, Strick, Toray.
Marc Allain, David Atherton, Igor Gruden, Sandeep Singh, Kevin Sisken, “Daimler’s Super Truck Program; 50% Brake Thermal Efficiency” (DEER 2012)