HD diesel engine – exhaust gas temperature management and advanced exhaust gas aftertreatment technology for ultra-low NOx emission legislation

Upcoming ultra-low NOx emission legislations in the USA and Europe will require the fulfilment of very low emission limits. Therefore, a highly efficient exhaust aftertreatment system in combination with a suitable control architecture, low NOx engine out emissions and rapid heat-up measures becomes mandatory. Using a 2-stage SCR system with a close coupled SCR as a first catalyst in the aftertreatment system combined with enhanced thermal management measures allows high NOx conversion immediately after cold start and in low load operation. The 2nd SCR also supports NOx conversion in high load and high temperature operation. Additionally, a smart NOx conversion balancing over the two SCR stages leads to benefits in terms of passive DPF regeneration associated with high PN filtration efficiency. In the hot FTP cycle, NOx conversion above 99.5% is obtained confirming the high potential of the engine and EAS concept to achieve ultra-low NOx emissions.