Meeting Stringent 2025 Emissions and Fuel Efficiency Regulations with an Opposed-Piston, Light-Duty Diesel Engine

摘要

With current and pending regulations-including Corporate Average Fuel Economy (CAFE) 2025 and Tier 3 or LEV III-automakers are under tremendous pressure to reduce fuel consumption while meeting more stringent NO_x, PM, HC and CO standards. To meet these standards, many are investing in expensive technologies-to enhance conventional, four-stroke powertrains-and in significant vehicle improvements. However, others are evaluating alternative concepts like the opposed piston, two-stroke engine. First manufactured in the 1890s-and once widely used for ground, marine and aviation applications-the historic opposed piston, two-stroke (OP2S) engine suffered from poor emissions and oil control. This meant that its use in on-highway applications ceased with the passage of modern emissions standards. Since then, Achates Power has enhanced the opposed-piston engine and resolved its historic challenges: wrist pin and power cylinder durability, piston and cylinder thermal management, piston ring integrity and oil consumption [1]. An in-depth study on opposed-piston, two-stroke diesel engine performance and emissions in a light-duty truck application is presented here for the first time in a technical paper. The paper includes a: Brief review of the opposed-piston, two-stroke engine's architectural advantages (thermodynamics, pumping work and combustion); Comprehensive overview of the engine's performance and emissions results, including indicated thermal efficiency, fuel consumption and emissions; Comparison of fuel economy and emissions to the published benchmark, the Cummins 2.8L ATLAS Diesel Engine [2]; Discussion of an exhaust temperature control strategy that is used to meet the aggressive catalyst light-off requirements of light-duty applications by achieving rapid catalyst light-off after a cold start; Comparison of engine balance of the light-duty truck concept engine and a state-of-the-art gasoline V6 engine; Examination of the packaging options for an opposed piston, two-stroke engine in a light-duty truck application. The results of this study show that the Achates Power opposed-piston engine benefits-high efficiency, low emissions and reduced cost, mass and complexity-already demonstrated for medium-duty commercial vehicles [1] are also available for light-duty applications. In fact, to an even greater extent: over 30% fuel economy improvement when compared to an equivalent four-stroke diesel engine. Moreover, this study shows that the final 2025 light-truck CAFE fuel economy regulation not only has the potential to be met but also the potential to be exceeded with a full-size 5,500 lb. pick-up truck by simply applying the Achates Power technology without any hybridization or vehicle improvements.