Gary D. Neely’s research while affiliated with Southwest Research Institute and other places

Multiple areas in the U.S. continue to struggle with achieving National Ambient Air Quality Standards for ozone. These continued issues highlight the need for further reductions in NO X emission standards in multiple industry sectors, with heavy-duty on-highway engines being one of the most important areas to be addressed. Starting in 2014, CARB initiated a series of technical demonstration programs aimed at examining the feasibility of achieving up to a 90% reduction in tailpipe NO X , while at the same time maintaining a path towards GHG reductions that will be required as part of the Heavy-Duty Phase 2 GHG program. These programs culminated in the Stage 3 Low NO X program, which demonstrated low NO X emissions while maintaining GHG emissions at levels comparable to the baseline engine. Building on that prior program effort, EPA continued to support further Low NO X demonstration efforts in support of the development of new Federal Emissions Standards for heavy-duty highway vehicles and engines as part of the Clean Trucks Plan. Some of these efforts have been reported in previous publications, which focused on the evaluation of a modified Stage 3 architecture to extended useful life, as well as examination of various challenges related to field duty cycles, in-use measurements, sensors, and fuel. Beyond these efforts, EPA also undertook a redesign effort to produce an updated Low NO X aftertreatment system. The updated system incorporated many lessons learned from previous efforts, as well as recent catalyst process and formulation updates to improve performance and durability in key areas. This updated system was evaluated for emission control performance and durability using the Stage 3 Low NO X test engine. The updated system was aged to 800,000 equivalent miles using DAAAC accelerated aging techniques, and it was evaluated over both regulatory and field duty cycles. The results of these evaluations are presented within this paper.

div class="section abstract"> Despite considerable progress towards clean air in previous decades, parts of the United States continue to struggle with the challenge of meeting the ambient air quality targets for smog-forming ozone mandated by the U.S. EPA, with some of the most significant challenges being seen in California. These continuing issues have highlighted the need for further reductions in emissions of NO_X, which is a precursor for ozone formation, from a number of key sectors including the commercial vehicle sector. In response, the California Air Resources Board (CARB) embarked on a regulatory effort culminating in the adoption of the California Heavy-Duty Low NO_X Omnibus regulation.[ 1 ] This regulatory effort was supported by a series of technical programs conducted at Southwest Research Institute (SwRI). These programs were 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, while maintaining a path towards compliance with current heavy-duty Phase 2 GHG standards. These efforts culminated in the Stage 3 Low NO_X program, the results of which have been documented in previous publications. In parallel with the completion of the Stage 3 technical effort, EPA began an effort to promulgate a national heavy-duty low NO_X regulation, with the goal of completing the regulation in 2022 to support a 2027 model year implementation.[ 2 , 3 ] As part of that regulatory effort, EPA leveraged the test platform that was developed under the Stage 3 program to continue investigation of Low NO_X technology capabilities and limitations. The emission control system was upgraded in several ways, and a number of topics were examined that expanded the scope of the evaluation. These included investigation of system performance under a variety of field duty cycles, examination of extended useful life out to 800,000 miles, the impact of low ambient temperatures on performance, and others. The performance of the updated system, and the results of the wider system investigations are summarized in this paper. </div

div class="section abstract"> 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. 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

Recent 2010 emissions standards for heavy-duty engines have established a limit of oxides of nitrogen (NOX) emissions of 0.20 g/bhp-hr. However, CARB has projected that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with 2010 emission standards, the National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter and Ozone will not be achieved without further reduction in NOX emissions. The California Air Resources Board (ARB) funded a research program to explore the feasibility of achieving 0.02 g/bhp-hr NOX emissions. This paper details engine and aftertreatment NOX management requirements and model based control considerations for achieving Ultra-Low NOX (ULN) levels with a heavy-duty diesel engine. Data are presented for several Advanced Technology aftertreatment solutions and the integration of these solutions with the engine calibration. Further development is necessary for optimizing vocational test cycle emissions, but the results presented here demonstrate a potential pathway to achieving ultra-low NOX emissions on future heavy duty vehicles.