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<div class="section abstract"><div class="htmlview paragraph">Despite considerable progress over the last several decades, California continues to face some of the most significant air quality problems in the United States. These continued issues highlight the need for further mobile source NO_X reductions to help California and other areas meet ambient air quality targets mandated by the U.S. EPA. Beginning in 2014, the California Air Resources Board (CARB) launched a program aimed at demonstrating technologies that could enable heavy-duty on-highway engines to reach tailpipe NO_X levels up to 90% below the current standards, which were implemented in 2010. At the same time, mandated improvements to greenhouse gas emissions (GHG) require that these NO_X reductions be achieved without sacrificing fuel consumption and increasing GHG emissions. The CARB demonstration program has progressed through several stages since it was initiated, and the Stage 3 Low NO_X program completed in 2020 represents the culmination of these technology demonstration efforts. This effort, using a 2017 production diesel engine as a baseline, demonstrated a combination of technologies that enabled Low NO_X emission levels near the 90% reduction target, while at the same time maintaining GHG emission rates at the same levels as the base engine.</div><div class="htmlview paragraph">Previous publications have gone into detail regarding individual elements of the Stage 3 technology package. This paper will present a summary of the final configuration and final results of the Stage 3 program, including results for the fully aged aftertreatment system after the equivalent of 435,000 miles of operation. The performance of the final test article will be shown over a variety of both regulatory duty cycles and other off-cycle operations. The final fuel consumption and GHG performance of the system will also be described based on the benchmarking methods specified by EPA in the Phase 2 GHG standards.</div></div>

Commercial vehicles require fast aftertreatment heat-up in order to move the selective catalytic reduction catalyst into the most efficient temperature range to meet upcoming NOX regulations while minimizing CO2. This study is a follow-up study using an electric heater upstream of a LO-SCR followed by a primary aftertreatment system having an engine equipped with cylinder deactivation. The focus of this study is to minimize the maximum power input to the e-heater without compromising tailpipe NOX and CO2. A system solution is demonstrated using a heavy-duty diesel engine with an end-of-life aged aftertreatment system targeted for 2027 emission levels using various levels of controls. The baseline layer of controls includes cylinder deactivation to raise the exhaust temperature more than 100°C in combination with elevated idle speed to increase the exhaust mass flow rate through the aftertreatment system. The engine load is adjusted to compensate for generating electrical power on the engine. The combination of electrical heat, added load, cylinder deactivation, and elevated idle speed allows the aftertreatment system to heat up in a small fraction of the time required by today’s systems. This work was quantified over the cold federal test procedure, hot FTP, low load cycle (LLC), and the U.S. beverage cycle showing improved NOX and CO2 emissions. The improvement in NOX reduction and the CO2 savings over these cycles are highlighted.

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<div class="section abstract"><div class="htmlview paragraph">The commercial vehicle industry continues to move in the direction of improving brake thermal efficiency while meeting more stringent diesel engine emission requirements. This study focused on demonstrating future emissions by using an exhaust burner upstream of a conventional aftertreatment system. This work highlights system results over the low load cycle (LLC) and many other pertinent cycles (Beverage Cycle, and Stay Hot Cycle, New York Bus Cycle). These efforts complement previous works showing system performance over the Heavy-Duty FTP and World Harmonized Transient Cycle (WHTC). The exhaust burner is used to raise and maintain the Selective Catalytic Reduction (SCR) catalyst at its optimal temperature over these cycles for efficient NO_X reduction. This work showed that tailpipe NO_X is significantly improved over these cycles with the exhaust burner. In certain cases, the improvements resulted in tailpipe NO_X values well below the adopted 2027 LLC NO_X standard of 0.05 g/hp-hr, providing significant margin. In fact, near zero NO_X was measured on some of these cycles, which goes beyond future regulation requirements. However, burner operation on the tested cycles also resulted in a CO₂ increase, indicating that a different burner calibration strategy, or possibly an additional technology, will be needed to achieve lower CO₂ emissions.</div></div>