Heavy Duty FTP Results on Multi-Cylinder Opposed-Piston Engine Demonstrating Rapid Exhaust Enthalpy Rise to Achieve Ultra Low NO_x CO_2

摘要

The 2027 Phase2 GHG emissions standard, and the proposed 2024 ultra-low NO_x emission standard posed a significant challenge to achieve due the trade-off of NO_x emission and fuel consumption. To achieve ultra-low NO_x emission levels over the composite heavy-duty FTP cycle, the engine must provide rapid heat energy to the exhaust after-treatment system, whiling limiting NO_x emissions during cold start portion of the cycle. And the after-treatment system must maintain peak NO_x reduction during the hot-start portion of cycle. Delivering this has been the challenge for conventional four-stroke heavy duty diesel engines as these are competing demands. Ultra-low NO_x system solutions [ 1] involving the implementation of supplemental heat sources downstream in the exhaust system comes at CO_2 penalty and adds significant cost and complexity. The Achates Power Opposed-Piston (OP) Engine design provides an ideal solution to this challenge. This is because the OP engine design has several inherent advantages over conventional four-stroke engines, like higher brake thermal efficiency (BTE) and low BMEP, that provide fuel consumption or CO_2 advantage. Additionally, the ability of OP engines to control internal EGR facilitating low NO_x emissions and, to convert fuel to exhaust enthalpy providing rapid exhaust temperature rise can be leveraged during the cold-start portion of the HD FTP cycle. This paper highlights the results from cold-start HD FTP testing on the 4.9L OP engine. The goal of this testing was to evaluate the ability of the Achates Power OP engine to provide rapid exhaust temperature rise by operating the engine in the mode designed to deliver rapid exhaust enthalpy during cold-starts, while maintaining low NO_x emissions from the engine. This enables fast SCR catalyst light-off resulting in early and peak NO_x reduction. The engine out data of exhaust constituents were used as inputs for aftertreatment system simulations to evaluate if potential tailpipe NO_x and CO_2 performance can meet the planned GHG and proposed ULNO_x standard.