Giovanni D'Urbano’s scientific contributions

Diesel exhaust gas aftertreatment systems, which include the selective catalytic reduction (SCR)) for reduction of NOx are necessary to fulfil the latest legal requirements and are extensively used in the heavy duty (HD) sector. The present paper informs about some results obtained with SCR and with SDPF (a DPF with SCR-coating) on a medium duty research engine Iveco F1C. Beside the limited gaseous emission components NH3, NO2 and N2O were measured. The analysis of nanoparticle emissions was performed with SMPS and CPC. The integration of functions of filtration and NOx-reduction in one element of exhaust aftertreatment system offers several advantages and is widely investigated and considered as a market solution. Some most important technical statements of the research are: the emissions behavior of SDPF after urea switch-on (SWON) concerning NOx reduction speed and NH3-peak is always fluctuating, due to inhomogeneous distribution of urea, urea products and soot in the filter volume, this even with a carefully conducted conditionings,the active urea injection with fully loaded SDPF causes a lower level of passive regeneration efficiency by mass and a slower backpressure drop in the last, highest step of the regeneration attempt,the loaded SDPF, compared with empty one shows: slower NOx- reduction and higher NH3 after SWON because of use of part of NO2 for soot oxidation and consequently less NO2-availability for the deNOx-reactions; the secondary NP penetration after SWON is clearly lower with the loaded trap,both investigated systems: SDPF and 2 x SCR attain nearly the same deNOx-efficiency,in WHTC with a lower level of exhaust gas temperature SDPF causes lower deNOx-values (40-45% against 75% in ETC), but also lower NH3-emissions. Further developments of those aftertreatment systems, concerning substrates, coatings and reduction agent control, open further potentials of improvements.

The combined exhaust gas aftertreatment systems (DPF+SCR) are the most efficient way and the best available technology (BAT) to radically reduce the critical Diesel emission components particles (PM&NP) and nitric oxides (NOx). SCR (selective catalytic reduction) is regarded as the most efficient deNOx-system, diesel particle filters are most efficient for soot abatement. Today, several suppliers offer combined systems for retrofitting of HD vehicles. Quality standards for those quite complex systems and especially for retrofit systems are needed to enable decisions of several authorities and to estimate the potentials of improvements of the air quality in highly populated agglomerations. The present paper informs about the VERTdePN) quality test procedures, which were developed in an international network project with the same name 2007-2011 (VERT. Verification of Emission Reduction Technologies; dePN. decontamination, disposal of PM / NP and of NOx). Some interesting results of research on the engine dynamometer from the last test period 2011-2013 are given as a complement of the already published results. The most important statements are: the procedures for the quality verification of SCR-, or (DPF+SCR) - systems are developed and confirmed,engine dynamometer testing enables the deepest insight in the investigated system concerning: secondary- and non- legislated emissions, variations of feed factor, analysis on different sampling positions and at specific engine operating conditions (like legal test procedures),testing of SCR-systems on vehicle (chassis dynamometer, or road) is important, because of urea dosing, urea mixing and electronic control,the filtration efficiency of a DPF is independent of the operating condition (except of regeneration period, or passing over the maximum space velocity),the NOx reduction efficiency of SCR-systems is dependent on the operating conditions, because of the optimal temperature window of the SCR-catalysis; at the conditions with exhaust temperature below 200°C the urea dosing is stopped. There is an intense further development of those aftertreatment systems and their electronic control, which opens further potentials of improvements.

The use of alternative fuels and among them the biofuels of 1st generation - fatty acid methyl esters FAME's*) and pure plants oils - for propulsion of IC engines is an important objective in several countries in order to save the fossil fuels and to limit the CO2-production. The properties of bio-fuels and bio-blend-fuels can vary and this has an impact on the operation and emissions of Diesel engines and on the modern exhaust aftertreatment systems. The present paper represents the most important results obtained with RME at AFHB, EMPA and EC-JRC. Most of the activities were performed in the network project BioExDi (Biofuels, Exhaust Systems Diesel) in collaboration between industry and research institutes. Following most important statements can be given about the treated subjects: emissions (engine-out) are influenced by RME in the sense less CO, HC & PM, more NOx and more SOF,there are positive influences of RME on the functionality of DOC and DPF due to higher reactivity of RME, no influence on SCR,the long term functionality of exhaust aftertreatment systems with RME can be influenced by the potential higher availability of elements, like Ca, Mg, Zn, P, S, K,regarding particle mass PM: without DPF there are slight tendencies of lowering TEQ at low load with RME and increasing TEQ at high load of the engine; with DPF there is a strong reduction of all toxic substances and there are no effects of RME on PAH & TEQ. Some practical recommendations for the users of biofuels of the 1st generation are given at the end of the paper. Generally there is a necessity of higher costs and efforts for more frequent service and maintenance and for the quality controls of fuel and fuel supply chain.

The fatty acid methyl esters (FAME's)-in Europe mostly RME (Rapeseed methyl ester)-are used in several countries as alternative biogene Diesel fuels in various blending ratios with fossil fuels (Bxx). Questions often arise about the influences of these biocomponents on the modern exhaust aftertreatment systems and especially on the regeneration of Diesel particle filters (DPF). In the present work different regeneration procedures of DPF systems were investigated with biofuels B0, B20 & B100. The tested regeneration procedures were: passive regenerations: DOC + CSF; CSF alone,active regenerations: standstill burner; fuel injections & DOC. During each regeneration on-line measurements of regulated and unregulated emission components (nanoparticles & FTIR) were conducted. It can be stated that the increased portion of RME in fuel provokes longer time periods to charge the filter with soot. This is due to the lower PM-emissions of the engine, as well as to the higher reactivity and higher SOF-portion of the particle mass from RME. With the passive regeneration system with stronger catalytic activity (DOC + CSF) there is a stronger NO 2-production with B100 and due to the NO2-supported oxidation of PM the balance point temperature is approx. 20°C lower, than with B0. For the active regenerations the time histories of emissions and temperatures are closely connected with the chosen regeneration strategy-switching, timing and intensity (of burner, or fuel aerosol generator). A higher portion of biocomponent usually causes a stronger break-down of the instantaneous DPF filtration efficiency during the regeneration procedure-this is an effect of stronger artefact of spontaneous condensation after DPF. In summary there is no negative short term effect of bio-blend-fuels on the investigated regeneration procedures. Some recommendations for a successful long term operation, basing on other works and literature are given at the end of the paper.

The most efficient way and the best available technology (BAT) to radically reduce the critical Diesel emission components particles (PM&NP) and nitric oxides (NO x) are combined exhaust gas aftertreatment systems (DPF+SCR). SCR (selective catalytic reduction) is regarded as the most efficient deNO x -system, diesel particle filters are most efficient for soot abatement. Today, several suppliers offer combined systems for retrofitting of HD vehicles. The presented results are part of the work in the international network project VERT *) dePN (de-activation, de-contamination, disposal of particles and NO x), which has the objectives to establish test procedures and quality standards and to introduce the SCR-, or combined DPF+SCR-systems in the VERT verification procedure. Examples of results for some of the investigated systems are given and the most important findings are: the average NO x conversion rate at transient operation strongly depends on the operation load profile, on the exhaust gas temperature and the resulting urea dosing control, the particle number filtration efficiency, which is verified at stationary engine operation, is valid also at the transient operation,secondary nanoparticles are produced due to urea injection, they nevertheless do not impact significantly the overall filtration efficiency of the system (here: DPF upstream & SCR downstream, differences of PCFE in the range of 0.1%), the OEM NO x -sensors of the investigated systems are appropriate tools for the in-use control, the system with catalyzed DPF (upstream) attains higher overall deNO x -efficiencies due to NO 2 -production in the DPF, for the investigated systems there are no critical emissions of unregulated components, NH 3 & N 2 O.