Future emission regulations (Euro VII, LEV IV, Tier V, China VII, etc.) will impose more stringent requirements both in terms of regulated pollutants emissions and CO2 for On-Road and Off-Road Diesel applications. The higher regulatory stringency will require more complex Aftertreatment Systems (ATS) architectures. Among the innovative technologies that will be introduced, the Diesel Dosing Unit (DDU) in the exhaust is emerging as one of the enablers for overall compliance. Currently available DDUs work at low pressure (LP) fuel supply around 5 bar and often require a mixer downstream in the exhaust line to ensure the right level of fuel atomization, evaporation and mixing. The usage of high pressure (HP) fuel supply at around 200 bar, together with component design enhancement and dedicated spray targeting generates advantages in terms of CO2 both during Diesel Particulate Filter (DPF) regeneration and normal modes and on pollutant emissions in regeneration mode.
To quantify the advantages, steady state and transient tests were executed on a state of the art 6.6 L Diesel engine where the HP-DDU was assessed in comparison with LP-DDU which was part of the baseline ATS. The comparison between the two technologies was made by installing the HP-DDU in two ATS layouts: nominal mixing length (as baseline) and reduced mixing length. For both HP-DDU ATS layouts, the mixers present in the baseline LP-DDU were removed.
During DPF regeneration, both layouts assessed showed benefit in THC (up to 20%), CO (up to 95% at low flow, 50% at medium flow), and BSFC (up to 1.5-2.0%). Additionally, DPF regeneration tests in transient conditions highlighted better temperature control and higher residual O2 (after fuel oxidation over the DOC), leading to shorter DPF regeneration duration. In normal mode, a reduced back pressure due to the mixer removal resulted in an estimated CO2 saving up to 10% at rated power. Considering all the measured benefits, the Dumarey developed HP-DDU technology is considered promising for compliance with upcoming CO2 and emission regulations worldwide.