Design and Durability of Vanadium-SCR Catalytic Aftertreatment System to Meet Tier 4 Emission Regulations in a Locomotive Application 2019-01-5015

An advanced exhaust aftertreatment system (ATS) for Tier 4 compliant locomotive applications was successfully designed and developed for use on Cummins QSK95 engines. The engine and ATS were introduced in late 2016. This system provided nitrogen oxides (NO_x) reduction capability in excess of 95%. Vanadia-based selective catalytic reduction (V-SCR) extruded catalyst technology was chosen over other readily available component technologies such as diesel oxidation catalyst (DOC) or a combination of DOC and SCR systems to address the stringent Tier 4 standards. In addition to NO_x reduction, substantial oxidation of gaseous hydrocarbons (HCs) from unburnt fuel and lubricating oil soluble organic fraction (SOF) was also achieved. This dual functionality (oxidation and reduction capability) was one of the key factors in adopting this technology as the prime path and rendering it suitable for the harsh locomotive application environment. The properties and performance of the chosen Johnson Matthey Inc. (JMI) extruded V-SCR catalyst are described in this article. In-house developed analysis led design (ALD) and computational fluid dynamics (CFD) tools were utilized to design the ATS package and adhere to the space claim requirement. These tools were also used to support the flow distribution index (FDI), uniformity index (UI) flow, and thermal management strategy approaches, as well as to estimate the total catalyst volume and subsequently the simulated end of useful life (EUL) catalyst performance. Additionally, ATS architecture and subsystem components including controls, dosing, and decomposition reactor pipe (DRP) are discussed in this article. Behind-engine performance testing demonstration following the 10-mode locomotive line-haul test cycle along with the locomotive notch performance curve results provided evidence of system robustness meeting Tier 4 requirements for both newly integrated ATS as well as EUL systems.