Potential for Reduction in NRMM Real-World Emissions

<div class="section abstract"><div class="htmlview paragraph">The pollutant emission regulation for Non-Road Mobile Machinery (NRMM) is currently under consideration, both in the European Union (EU) and the United States (US). In Europe a Stage V review is expected within 2025 and in the US, the California Air Resource Board (CARB) has released their Tier 5 proposal in late 2024. It is expected that there will be further focus on covering a wide variety of operation conditions in actual use cases, including continuous low load scenarios. In addition, CO<sub>2</sub>-neutral fuels are being investigated to reduce the carbon footprint of NRMM Internal Combustion Engines (ICE), which remains an important powertrain for the sector. The objective of the work presented is to assess the potential for emissions reductions in the future, both NOx and CO<sub>2</sub>. A simulation study is conducted, modelling a 9l class engine with 8-10 g/kWh engine-out NOx emission level. Three different emission control systems are investigated: an enhanced stage V system with single SCR, a system with dual-SCR and a system with an Exhaust Gas Heater (EGH). Results are simulated for a range of type approval test cycles such as the non-road transient cycle (NRTC), the non-road stationary cycles (NRSC), the low-load cycle (LLC) and in-use cycles (bulldozer, wheel loader and hay mover). NOx results show all 3 variants are within CARB Tier 5 and Euro 7 limits on NRTC. Furthermore, consistent low emissions are observed over the range of in-use cycles. Variants 2 and 3 show lower cold-start emissions, but this benefit is not visible after regulatory cold/hot weighing. Variant 2 shows lower N<sub>2</sub>O emissions. Tailpipe CO<sub>2</sub> emissions are similar for all 3 variants on most of the tests, except for continuous low-load conditions due to variations in engine mode switching. Overall, the work shows it is possible to develop a future-proof ICE concept for NRMM towards zero-impact pollutant emissions.</div></div>