Unregulated Emissions Characterization and Comparison for Two Off-Road Applications: A DPF and Non-DPF Engine

As governmental agencies focus on low levels of the oxides of nitrogen (NOx) emissions compliance, new off-road applications are being reviewed for both regulated and unregulated emissions to understand the technological challenges and requirements for improved emissions performance. The California Air Resources Board (CARB) has declared its intention to pursue more stringent NOX standards for the off-road market. As part of this effort, CARB initiated a program to provide a detailed characterization of emissions meeting the current Tier 4 off-road standards [1]. This work focused on understanding the off-road market, establishing a current technology emissions baseline, and performing initial modeling on potential low NOx solutions. This paper discusses a part of this effort, focuses on the emissions characterization from two non-road engine platforms, and compares the emissions species from different approaches designed to meet Tier 4 emissions regulations. The engine platforms reflected the available technology for diesel particulate filter (DPF) and non-DPF aftertreatment architectures. A detailed emissions characterization of the gaseous and particulate emissions was performed to measure an extensive list of non-regulated emission measurements. These measurements included volatile organic compounds (VOC), aldehydes and ketones, polycyclic aromatic hydrocarbons (PAH), elemental carbon and organic carbon (EC/OC), intermediate soluble organic compounds (IVOC), and semi-volatile organic compounds (SVOC). State-of-the-art analytical sampling and analysis methods were employed for the determination of the various exhaust species. The engines were evaluated using certification cycles (Non-Road Transient Cycle - NRTC and two Ramped Modal Cycles - RMC) and a low load application cycle (LLAC) developed from field applications. Results from this study indicated that both applications met Tier 4 regulations, and the aftertreatment produced unregulated emissions which were consistent with the type of aftertreatment employed. This work provided valuable data regarding engine and aftertreatment simulation models used to evaluate candidate current-technology, low NOX aftertreatment architectures.