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Conference report: US DOE Vehicle Technologies Annual Merit Review 2023

5 July 2023

The US DOE Vehicle technologies Office 2023 Annual Merit Review was held as a virtual event June 12-15, 2023. Program areas included Decarbonization of off-road, Rail, Marine and Aviation (DORMA), Energy Efficient Mobility Systems (EEMS), Technology Integration (TI), Batteries (BAT), Electrification (ELT) Materials (MAT) and Analysis (VAN). Projects previously in the Advanced Combustion Systems (ACE) program area are now in the DORMA program area.

Internal combustion engine projects fall mainly in the DORMA program area. Projects presented this year in this program area can be grouped into several categories: engines, aftertreatment systems, alternative fuels, electrification, development tools and sustainable aviation fuels (SAF). A few projects from other areas including electrification and materials will also be mentioned in this summary.


Cummins is developing and demonstrating a high efficiency, high power output 10 L natural gas engine capable of low NOx emissions [5828]. Performance targets include 400 hp peak power, 1350 lb-ft peak torque, 42% peak BTE, 36% cycle average BTE over the heavy-duty FTP, 39% cycle average BTE over the RMCSET and 0.02 g/hp-hr NOx while meeting all other criterial pollutant limits for 2027 EPA/CARB. Cost targets include 12-24% cost savings compared to the current production L9N and no increase in cost for the emissions control systems. Some challenges that need to be addressed include knock avoidance, high exhaust temperatures and misfire avoidance and accurate fueling control at low loads to improve TWC performance. Simulation work shows that EGR is not needed and that is the current direction of the project. The design incorporates high compression ratio, an exhaust system designed to minimize residual gas, a close coupled TWC, port fuel injection, pent roof combustion chamber, DOHC with both cams having lobe switching and phasing capability. Engine testing at steady state is planned to be completed by early 2024 and the demonstration against all project goals by early 2025.

Cummins along with Tula and Jacobs are applying dynamic skip fire (DSF) on a heavy-duty Otto-cycle natural gas engine that uses cooled EGR with the goal of overcoming the sharp drop in efficiency at part load [5829]. Deactivating a fixed number of cylinders can improve part load efficiency but is limited in applicability over a wide speed/load range. DSF provides flexibility over standard cylinder deactivation (CDA) solutions by allowing any of the engine cylinders to be deactivated without compromising NVH targets. Hardware and control system architecture have been defined and a 15% fuel economy benefit over the LLC is predicted by simulation. NVH considerations limit the number of deactivated cylinders at idle to three. Engine demonstration is expected to be completed by early 2024 and drive cycle and chassis dyno testing by early 2025. The new design uses a Type III valvetrain system (previously Type II) with dual overhead camshafts (DOHC) and independent cam phasing. The 2-stroke engine braking (“2SB”) is replaced with 1.5SB. CDA and 1.5SB operation modes are achieved with collapsing rocker technology incorporating a ‘Wedgelock’ capsule. Nine bi-state oil control valves (OCVs), one per cylinder to activate CDA and one per cylinder pair to activate the engine brake are used. Three identical manifolds per engine each house three OCVs.

Achates, along with Isuzu and some university partners is developing a hybrid variation of its 10.6 L opposed piston two-stroke engine for commercial vehicles [5830]. The target is to yield a 13% fuel savings over the non-hybrid version of the engine when installed in a vehicle. Series and P2 parallel hybrid options were simulated over heavy-duty drive cycles and the fuel economy (MPG) and freight efficiency (ton-mpg) compared against a conventional vehicle. The results for a vehicle with a nominal 15-ton freight capacity suggest a hybridized opposed piston 2-stroke can improve fuel economy by 40% to 140% and freight-efficiency from 37% to 70% depending on the drive cycle. While the series hybrid was superior to the parallel hybrid in terms of fuel economy, the parallel hybrid provided a 3-4% advantage in freight efficiency due to a smaller loss in freight capacity. Engine-in-the-loop testing is scheduled for later this year. In parallel, they are also defining the best approach to burn hydrogen in the opposed piston two-stroke engine.

A project by Cummins and ORNL developing a new piston crown alloy that will tolerate higher peak cylinder pressures and enable higher efficiency and power density is almost complete [5831]. The new material, called G3-5M, has survived a 500 h modified peak power output test with enhanced severity in an X15 X600 production engine. Compared to a commonly used commercial steel, 4140, the new medium carbon steel offers at least a 50°C increase in temperature capability.

Eaton is demonstrating a range of their technologies on an off-road engine that is targeting ≥10% GHG reduction and ≥90% NOx reduction over multiple duty cycles [5832]. Using a Tier 4 FPT 13 L engine as a baseline, the engine will be fitted with cylinder deactivation, a high efficiency turbocharger, an EGR pump and a modular aftertreatment system featuring a DPF. The baseline engine currently consists of a DOC and SCR. The project has recently started and is scheduled for completion in 2025.

A project focusing on ducted fuel injection (DFI) technology developed at Sandia showed > 90% soot reductions with oxygenated fuels containing up to 67% alkoxyalkanoate in a sustainable diesel base fuel [5833]. It was also demonstrated that heat transfer with DFI can increase by ~1% due to higher near-wall temperatures and higher convective heat transfer coefficients. A low-NOx mixing controlled combustion concept that does not use EGR was also proposed. In this concept, DFI with a highly oxygenated fuel could lower the equivalence ratio in the autoignition zone below unity and prevent a diffusion flame from forming that could slash NOx. The project is also developing a first-generation optical spray/duct alignment system.

GM’s project developing a spark ignition medium-duty truck engine capable of providing a minimum 10% fuel economy improvement and 15% engine weight reduction relative to a 2015 L96 VORTEC 6.0 L V8 engine is nearing completion [5834]. The measured fuel economy improvement with the Phase 1 engine was reported at 9.1% with the effect of a passive pre-chamber spark plug still undetermined. Key features of the Phase 2 engine include: 2 spark plugs/cylinder, an ultra-high pressure DI fuel system, active charge motion control, HP EGR, an aluminum block, fabricated tubular exhaust manifolds, plastic rocker covers and valley tray and a split cooling with valve bridge drilling. The weight reduction of the Phase 2 engine was reported as 15.4%.

Ford’s spark-ignited light-duty engine program targeting a 23% fuel economy improvement and 15% weight reduction relative to a 2016 3.5L V6 EcoBoost F150 baseline is also nearing completion [5835]. The reported fuel consumption reduction at 1500 rpm and 5 bar BMEP is about 13% using an active prechamber and 27% EGR. A further reduction is expected after resolving a fuel pressure limit for the prechamber. This, combined with increasing EGR to 40% and reducing engine friction is expected to deliver a 17 % reduction at this operating condition. The target fuel economy improvement for the vehicle is expected to be demonstrated later this year.

Other engine related projects included the development of a high-pressure fuel injection system for liquified gases by WM International Engineering [5836] and the development of a mixing controlled combustion system for gasoline/ethanol blends based on an active prechamber [5837].


PNNL along with several partners including John Deere are working to integrate a DOC and DPF into a single substrate (DOCF) for simultaneous CO, HC and PM control [5839]. The technology is intended to enable both passive and active soot oxidation without a separate upstream DOC while reducing overall PGM requirements. The project is about 60% complete and remaining challenges include optimization of soot management and understanding the interaction between catalyst and ash.

A project by PNNL is attempting to better understand N2O formation over SCR catalysts [5840]. Over 50 unique Cu-exchanged small pore zeolite catalysts have been studied during low-temperature standard SCR. Possible N2O formation mechanisms that have been identified include indirect nitrate formation involving in situ NO2 and direct nitrate formation where NO2 is not involved. Unfortunately, SCR catalysts that are naturally less selective to N2O also tend to lack stability or low-temperature SCR activity.

PNNL and Stellantis are developing a passive NOx adsorber (PNA) material and found that a thermally stable 0.5wt% Ru1/ceria single atom catalyst prepared by atom trapping shows surprisingly high PNA performance and NO oxidation that is superior to Pd/zeolites [5841]. Large amounts of NOx are stored on ceria via spillover as nitrites due to a reaction with ceria oxygens.

GM is developing catalyst technologies to reduce PGM content in three-way catalysts [5842]. While details were sparse, they have developed a catalyst that uses a metal oxide coating over alumina that keeps PGM dispersed. A 60% Pd/Rh reduction at the powder level has been achieved and a 0.8 wt.% Pd catalyst was shown to have equivalent performance with baseline 2 wt.% Pd and a 0.2 wt.% Rh catalyst had equivalent performance with baseline 0.5 wt.% Rh. Outstanding work includes transforming the powder and core samples to full-size, fully formulated catalysts and demonstrating a 50% PGM cost savings on an engine dynamometer or vehicle.

ORNL is working with Caterpillar to understand aldehyde formation over DOCs when the engine is fueled with alcohol [5843]. While alcohols have low light-off temperatures, they can form significant levels of aldehydes over a DOC. Methanol is highly reactive on the DOC but forms formaldehyde while ethanol forms significant levels of acetaldehyde. Aldehydes can be less reactive than their corresponding alcohols over the DOC. PGM composition does not significantly impact alcohol and aldehyde reactivity trends. Further work to identify DOC formulations that may be more reactive to aldehydes as well as the reactivities of other low carbon fuels such as biodiesel and renewable diesel over a DOC is planned.


While most Supertruck 2 programs wrapped up last year, PACCAR’s is scheduled to be completed by the end of 2023 due to a later starting date [5844]. A 55.7% engine BTE has been demonstrated that includes a 4.7% BTE contribution from WHR. In addition to features previously noted, the engine includes a 48 V EGR pump, a long stroke, Miller cam timing, an exhaust manifold and cylinder head optimized for pulse energy capture, two-stage turbocharging, and high and low pressure charge air cooling. The expected freight efficiency improvement has been updated to 150%.

Supertruck 3 will focus on electrification and includes projects with PACCAR and Volvo. PACCAR is targeting ≥ 75% CO2 reduction, at a fleet level, compared to a diesel baseline and ≥ 30% total cost of ownership reduction compared to the current BEV portfolio [5845]. Volvo’s objectives include the development and demonstration of a Class 8 battery electric vehicle (BEV) capable of a 400-mile range on a single charge [5846].


Projects focusing on hybridization of off-road vehicles included those by Deere, Michigan Tech (MTU) and the University of Minnesota. Deere is hybridizing an articulated dump truck to achieve over 20% reduction in fuel consumption and will feature a downsized engine (6.8 L) and a 700 V battery pack [5847]. Michigan Tech (MTU) has almost completed a project hybridizing an off-road material handler that is expected to provide a 46% reduction in fuel consumption compared to the base machine even in charge sustaining mode [5848]. The University of Minnesota is demonstrating an electric/hydraulic hybrid compact track loader that is intended to reduce battery electricity consumption by 40% compared to a pure electric version of the machine [5850].

Alternative Fuels

Projects examining details of combustion and spray formation of a variety of alternative fuels including hydrogen, methanol, ethanol and sustainable aviation fuels included:

2023 AMR presentations | AMR presentations database (2009-2023)