Evaluation and Demonstration of Ultra Low NOx Technologies for an On-Highway Diesel Engine

Authors

C. A. Sharp, Dr. C. Henry, G. Neely, S. Rengarajan, J. Sarlashkar, Southwest Research Institute, San Antonio, USA; C. C. Webb, Low Emission Technology Solutions, San Antonio, USA; Dr. S. Yoon, California Air Resources Board, Sacramento, USA

Year

2017

Print Info

Fortschritt-Berichte VDI, Series 12, No 802

Summary

Recently introduced 2010 emission standards for heavy-duty engines in the U.S. have established a limit for oxides of nitrogen (NO_x) emissions of 0.20 g/bhp-hr, a 90% reduction from the previous emission standards. However, it has been projected that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with the 2010 emission standards, the upcoming National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter and ozone will not be achieved in California without further significant reductions in NO_x emissions from the heavy duty vehicle fleet. There is currently little incentive for manufacturers to pursue emission reductions beyond the current standards, and so the potential for further reductions is unclear. To address this lack of information, the California Air Resources Board (CARB) commissioned a study to evaluate and demonstrate technologies with the potential of achieving NO_x emissions significantly lower than the current engine standard. The target NO_x emission rate for this project over the heavy-duty Federal Test Procedure (FTP) is 0.02 g/bhp-hr. This study involved evaluating improved engine emission control calibration, enhanced aftertreatment technology choices and configurations, improved and more efficient catalyst, improved aftertreatment thermal management, urea dosing strategies, and engine management practices for two heavy-duty engines: one natural gas engine with a three-way catalyst (TWC); and one diesel engine with a diesel particulate filter (DPF) and selective catalytic reduction (SCR). This discussion is concerned only with the diesel engine platform. A wide variety of technologies were initially evaluated using a novel burner-based approach to simulate the transient exhaust conditions of the engine. This was accomplished using SwRI’s proprietary Hot Gas Transient Reactor (HGTR) system. The use of the HGTR allowed for the rapid evaluation of a wide variety of technologies in a more efficient and repeatable fashion. Technologies were evaluated using an exhaust profile that was based on a modified engine calibration that was intended to achieve more rapid catalyst lightoff, and reduced engine-out NO_x emissions during the period prior to catalyst light-off. A subset of these technologies were down-selected for evaluation on the engine based on potential for NO_x reduction, impact on GHG emissions, and other factors such as cost and complexity. Based on the engine evaluations, a final configuration was developed to reach the target emission level. The final aftertreatment hardware was tested, and then aged on engine over an accelerated protocol designed to simulate full useful life. This final aged system was then tested to indicate fully aged performance levels. This paper presents the technology screening process, details of the final configuration and controls, and documented emission levels. At the time this paper was drafted, Final Aged results were not yet released for distribution, therefore the details of Final Aging and the Final Aged system performance will be summarized at a later date. System performance was evaluated of both regulatory cycles (FTP, RMC-SET, WHTC) and several vocational field cycles.