Thomas Harris’s scientific contributions

Commercial vehicles require fast aftertreatment heat-up to move the SCR catalyst into the most efficient temperature range to meet upcoming NOX regulations while minimizing CO2. One solution to this challenge is to add a fuel burner upstream of the con`ventional heavy-duty diesel aftertreatment system. The focus of this paper is to optimize a burner based thermal management approach. The objective included complying with CARB’s 2027 low NOX emissions standards for on-road heavy duty diesel engines. This was accomplished by pairing the burner system with cylinder de-activation on the engine and/or a light-off SCR sub-system. A system solution is demonstrated using a heavy-duty diesel engine with an 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 mass flowrate through the aftertreatment system. The combination of operating the fuel burner, cylinder deactivation and elevated idle speed (during cold start) allows the aftertreatment system to heat up in a small fraction of the time demonstrated by today’s systems. Performance was quantified over the cold FTP, hot FTP, low load cycle (LLC) and the U.S. beverage cycle. The improvement in NOX reduction and the CO2 savings over these cycles are highlighted.

The commercial vehicle industry continues to move in the direction of improving brake thermal efficiency while meeting more stringent diesel engine emissions requirements. This study focused on fuel efficiency when using an exhaust burner during cold starts. Selective catalyst reduction (SCR) systems are very efficient at eliminating NOx from the exhaust once its temperature has been raised to 250 °C. The exhaust burner is used during a cold start to raise the temperature of the SCR system quickly, and then it is turned off once thermal preparation of the SCR is complete. The exhaust burner converts fuel energy to exhaust heat directly, and thus more efficiently, in comparison to engine measures such as intake/exhaust throttling or elevating the idle speed. Therefore, if engine measures are scaled back because the burner is responsible for SCR system heating, total fuel efficiency should be improved.This hypothesis was tested at Southwest Research Institute (SwRI), making use of engine testing capabilities that allowed the results to be compared with those generated in the low-NOx technology demonstration funded by the California Air Resources Board (CARB). In addition to an exhaust burner, this testing made use of a conventional aftertreatment system (i.e. not a 2-stage SCR or “dual-dosing” system) that had been hydrothermally aged to end of useful life. FTP and WHTC cycles were run with the burner being responsible for more and more of the warm-up, allowing the tailpipe NOx vs. CO2 trade-off curve to be defined for this technology package.KeywordsEmissionsNOxCO2BurnerEfficiency

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