Detailed Emissions Characterization for Off-Road Applications: A DPF and non-DPF Engine Comparison 2022-01-0585

As agencies continue to focus on emissions compliance, low NO_X discussions have started to propagate beyond the on-highway market. Nonroad applications, which contribute to 29% of the PM emissions and 11% of the NO_X emissions in California, are being reviewed to understand the technological challenges and requirements for improved emissions performance. To help facilitate a nonroad low NO_X technology demonstration, information from current engine and aftertreatment technologies required a detailed assessment. The following work will discuss the emissions characterization results from two non-road engine platforms. The intention of this study was to compare the emissions species from different approaches designed to meet Tier 4 emissions regulations. The platforms reflect available technology for DPF and non-DPF aftertreatment architectures. A detailed emissions characterization included gaseous emissions, particulate matter, particle number, and an extensive list of non-regulated emission measurements (e.g. volatile organic compounds, polycyclic aromatic hydrocarbons, and water-soluble organic carbon). The engines were evaluated utilizing certification cycles, as well as, a low load application cycle developed from field applications. Results from this study indicate that while both applications meet Tier 4 regulations, each engine platform has associated challenges. For example, the non-DPF engine reduces PM by 40% to 50%, while the DPF engine can reduce PM by 95% or more. The non-DPF engine, however, had better low load NO_X reduction performance at 82% compared to the DPF engine at 67%. The tradeoff, though, was higher CO₂ emissions for the non-DPF engine. This work will provide valuable inputs to engine and aftertreatment simulation models, which will be utilized to evaluate candidate low NO_X aftertreatment architectures.