Christopher Sharp’s research while affiliated with Southwest Research Institute and other places

div>Commercial vehicles require advanced engine and aftertreatment (AT) systems to meet upcoming nitrogen oxides (NO_x) and carbon dioxide (CO₂) regulations. This article focuses on the development and calibration of a model-based controller (MBC) for an advanced diesel AT system. The MBC was first applied to a standard AT system including a diesel particulate filter (DPF) and selective catalytic reduction (SCR) catalyst. Next, a light-off SCR (LO-SCR) was added upstream of the standard AT system. The MBC was optimized for both catalysts for a production engine where the diesel exhaust fluid (DEF) was unheated for both SCRs. This research shows that the tailpipe (TP) NO_x could be reduced by using MBC on both catalysts. The net result was increased NO_x conversion efficiency by one percentage point on both the LO-SCR and the primary SCR. The CO₂ emissions were slightly reduced, but this effect was not significant. Finally, the MBC was used with a final setup representative of future AT systems which included standard insulation on the catalysts and optimal DEF dosing controls. This final configuration resulted in an improved NO_x and CO₂ such that the composite Federal Test Procedure (FTP) NO_x was 0.060 g/hp-hr and the composite FTP CO₂ was 508.5 g/hp-hr. The article details this cycle along with the low-load cycle (LLC) and beverage cycle. More technologies are required to meet the future California Air Resources Board (CARB) 2027 standard, which will be shown in future work.</div

New regulations by the California Air Resources Board (CARB) demand a stringent 0.02 g/hp-hr tailpipe NO x limit by the year 2027, requiring Selective Catalytic Reduction (SCR) catalysts to provide high NO x conversions even at low (below 200°C) exhaust temperatures. This work describes utilizing an Electrically Heated Mixer System (EHM system) upstream of a Light-Off Selective Catalytic Reduction (LO-SCR) catalyst followed by a conventional aftertreatment (AT) system containing DOC, DPF, and SCR, enabling high NO x conversions meeting CARB’s NO x emission target. The AT catalysts were hydrothermally aged to Full Useful Life. Conventional unheated Diesel Exhaust Fluid (DEF) was injected upstream of both the LO-SCR and primary downstream SCR. The EHM system allowed for DEF to be injected as low as 130°C upstream of the LO-SCR, whereas, in previous studies, unheated DEF was injected at 180°C or dosed at 130°C with heated DEF. The combination of unheated DEF, EHM system, LO-SCR, and downstream SCR enabled the needed increase in NO x efficiency in low exhaust temperatures, which was observed in drive cycles such as in cold-FTP, LLC, and World Harmonized Transient Cycle (WHTC). There were several-fold reductions in tailpipe NO x using this configuration compared to its baseline: 3.3-fold reduction in FTP, 22-fold in Low Load Cycle (LLC), 38-fold in Beverage Cycle, 8-fold in “Stay Hot” Cycle, and 10-fold in WHTC. Finally, it is shown that the EHM system can heat the exhaust gas, such as during a cold start, without needing additional heating hardware integrated into the system. These results were observed without performing changes in the engine base calibration.

Engine and aftertreatment solutions are being identified to meet the upcoming ultra-low NO x regulations on heavy duty vehicles as published by the California Air Resources Board (CARB) and proposed by the United States Environmental Protection Agency (US EPA) for the year 2027 and beyond. These standards will require changes to current conventional aftertreatment systems for dealing with low exhaust temperature scenarios. One approach to meeting this challenge is to supply additional heat from the engine; however, this comes with a fuel penalty which is not attractive and encourages other options. Another method is to supply external generated heat directly to the aftertreatment system. The following work focuses on the later approach by maintaining the production engine calibration and coupling this with an Electric Heater (EH) upstream of a Light-Off Selective Catalytic Reduction (LO-SCR) followed by a primary aftertreatment system containing a downstream Selective Catalytic Reduction (SCR). External heat is supplied to the aftertreatment system using an EH to reduce the Tailpipe (TP) NO x emissions with minimal fuel penalty. Two configurations have been implemented, the first is a Close Coupled (CC) LO-SCR configuration and the second is an Underfloor (UF) LO-SCR configuration. The CC LO-SCR configuration shows the best outcome as it is closer to the engine, helping it achieve the required temperature with lower EH power while the UF LO-SCR configurations addresses the real-world packaging options for the LO-SCR. This work shows that a 7 kW EH upstream of a LO-SCR, in the absence of heated Diesel Exhaust Fluid (DEF), followed by a primary aftertreatment system met the 2027 NO x regulatory limit. It also shows that the sub-6-inch diameter EH with negligible pressure drop can be easily packaged into the future aftertreatment system.

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.

div class="section abstract"> 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 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