Future of Combustion Engines Promises Efficiency, Green Fuels

Researchers and manufacturers believe that the internal combustion engine (ICE) can extend its relevance through improved efficiency and alternative fuel use. Innovations such as advanced mechanical designs and emission systems are anticipated to significantly lower CO2 emissions, potentially by 85%. Volvo's 2024 VNL model showcases a redesigned D13 engine with modifications aimed at favoring efficiency. The engine features a new piston design that improves combustion efficiency, which helps in reducing emissions and prolonging engine life. The introduction of a seven-wave piston structure and an advanced fuel injection system exemplifies this shift towards more effective combustion processes. Meanwhile, new regulations requiring lower nitrogen oxides (NOx) emissions by 2027 pose challenges, especially since NOx forms at high temperatures typical of diesel engines. However, selective catalytic reduction (SCR) systems can mitigate NOx emissions, allowing engineers to focus on enhancing diesel performance. Innovations from Cummins, including a larger aftertreatment system with electric heaters, aim to maintain efficiency even during low-speed or cold-start conditions. The interest in alternative fuels like dimethyl ether (DME) and hydrogen for ICE reflects a broader trend towards reducing dependence on traditional diesel fuels. DME, noted for its smokeless combustion characteristics, faces challenges like lubricity while hydrogen shows promise, especially for high-load applications such as long-haul trucking. In expert opinion, while ICE technologies evolve, they should not be discounted in the transition towards sustainable transportation. The enhancements being integrated into diesel engines can not only satisfy regulatory demands but also prolong the life and efficiency of existing technologies, ultimately playing a complementary role alongside emerging alternative fuel vehicles in the logistics sector. The focus should remain on cross-industry collaboration to unlock the potential of these technologies while exploring new fuel sources that can meet environmental goals without sacrificing operational efficiency. Cummins Inc. is addressing the challenges posed by the 2027 NOx emissions regulations through advancements in their HELM X15 diesel engine. This engine utilizes selective catalytic reduction (SCR) technology enhanced by a new aftertreatment system designed to maintain efficiency even in low-speed traffic conditions, crucial for urban areas like California. The new design includes electric heaters powered by a 48-volt alternator to ensure timely catalyst warm-up and effective NOx reduction at low engine loads. The HELM X15 will retain a similar architecture to current models, featuring enhancements such as dual overhead camshafts for improved valve action, reduced emissions, and better fuel economy. Cummins has emphasized that despite incorporating a more complex emission system, the overall weight of the engine will not increase due to advanced engineering techniques. The engine's performance is enhanced with a higher injection pressure and an optimized combustion system, offering improvements in both fuel efficiency and emission control. In the context of alternative fuels, research on dimethyl ether (DME) is being explored as a green alternative fuel, promising less particulate emission and easier handling compared to natural gas. However, its lack of lubricity poses a challenge for existing diesel injection systems. Current projects are focused on creating durable DME-compatible systems, which could allow for a significant reduction in engine-out NOx emissions. Additionally, another innovative approach is the development of a hydrogen-powered opposed-piston engine by Achates Power, seeking to exploit hydrogen combustion benefits while maintaining the efficiency characteristics typical of traditional internal combustion engines. Expert opinion suggests that the trucking industry is likely to adapt its reliance on internal combustion engines in the coming years while also gradually integrating alternative fuels such as hydrogen and DME. This adaptation will be essential to meet stringent emissions targets while maintaining operational efficiency and cost-effectiveness, indicating a transitional phase where both traditional and alternative powertrains coexist. Volvo has introduced enhancements to its D13 engine for the 2024 VNL model, featuring a rear camshaft drive that reduces vibration and improves engine efficiency. The engine incorporates dual overhead camshafts, optimizing valve action for better performance and lower emissions. The XPI fuel system has been upgraded with increased operating pressure, contributing to greater fuel economy. The new selective catalytic reduction (SCR) system will ensure compliance with 2027 NOx standards while minimizing diesel exhaust fluid consumption. In parallel, researchers are exploring alternative fuels such as dimethyl ether (DME) and hydrogen. DME offers smokeless combustion and high tolerance to exhaust gas recirculation but lacks lubricity compared to diesel. Researchers at Sandia National Laboratories aim to develop durable injection systems for DME and investigate ducted fuel injection to improve mixing and emissions. Achates Power is testing a hydrogen-fueled opposed-piston engine, which could provide high efficiency for heavy-duty applications without the need for spark plugs. These developments suggest a sustained evolution of internal combustion engines in the trucking sector, adapting to emission regulations and exploring greener alternatives. In the field of transportation, such advancements underscore the industry's potential for innovation in response to environmental challenges. As regulations tighten, the focus on alternative fuels and enhanced engine efficiencies indicates a transformative period for commercial vehicles, possibly prolonging the relevance of internal combustion engines while paving the way for cleaner alternatives. This approach may be critical for meeting both regulatory objectives and fleet performance demands in a rapidly changing landscape. Laurence Fromm, the executive vice president of business development at Achates Power, announced promising research at Argonne National Laboratory aimed at modifying the Achates opposed-piston, two-stroke engine for hydrogen fuel use. Led by principal mechanical engineer Essam El-Hannouny, the team successfully demonstrated that their engine could operate on hydrogen, marking a significant step in the adaptation process. The unique architecture of this engine design eliminates cylinder heads, a major source of heat loss in traditional engines, and allows it to efficiently retain exhaust gases at lower loads to enable compression ignition throughout its operating range, potentially allowing for hydrogen combustion without spark plugs. Fromm emphasized various advantages of hydrogen combustion over fuel cells, particularly in applications like long-haul transportation where fuel cells struggle with efficiency at high loads. He noted that the Achates engine, designed primarily for medium- to large-size commercial trucks, may present a more efficient solution for these demanding applications. The ongoing research also includes developing advanced injection systems for green fuels like DME and experimenting with valve actuation systems to enhance engine efficiency further. The expectation is that promising developments could emerge by mid-2025. This innovation suggests a transformative potential for the internal combustion engine in the face of environmental challenges. As transportation continues to push for emission reductions, technologies that allow existing engine architectures to adapt could ensure their relevance in a market increasingly focused on sustainability. This could preserve investment in current logistics infrastructures while offering a transitional solution as the industry gradually shifts towards fully hydrogen-powered or electric platforms.