Experimental and Numerical Analysis of Latest Generation Diesel Aftertreatment Systems

Sapio, Francesco; Millo, Federico; Fino, Debora; Monteverde, Alessandro; Sartoretti, Enrico; Bianco, Andrea; Postrioti, Lucio; Tarabocchia, A.; Buitoni, Giacomo; Brizi, Gabriele

doi:10.4271/2019-24-0142

Cited by 6 publications

(5 citation statements)

References 22 publications

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“…Lopez et al [84] determined the NOx conversion efficiency of a V-zeolite SCR-DPF monolith to be~70% for engine-bench tests, while Aryan et al [94] installed a Cu-zeolite SCR-DPF on a vehicle and determined the NOx conversion efficiency to be~60%. Sapio et al [95] evaluated an ATS composed of a closed-coupled DOC followed by a DEF injector and an SCR-DPF with SiC substrate with synthetic gases. They found a maximum NOx conversion of 99% at 350 • C, 86% at 250 • C, and more than 40% at 180 • C. The possibility to use the SCR-DPF in a hybrid aftertreatment system has been investigated by several authors.…”

Section: Scr On Filtersmentioning

confidence: 99%

An Overview of Lean Exhaust deNOx Aftertreatment Technologies and NOx Emission Regulations in the European Union

et al. 2021

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This paper reviews the recent advances in the management of nitrogen oxide (NOx) emissions from the internal combustion engine of light-duty and heavy-duty vehicles, addressing both technical and legal aspects. Particular focus is devoted to the often-virtuous interaction between new legislation imposing more restrictions on the permitted pollutant emission levels and new technologies developed in order to meet these restrictions. The review begins first with the American and then European directives promulgated in the 1970s, aimed at limiting emissions of pollutants from road transport vehicles. Particular attention is paid to the introduction of the Euro standards in the European Union for light- and heavy-duty vehicles, used as a legal and time frame reference for the evolution of emission aftertreatment systems (ATSs). The paper also describes governmental approaches implemented for the control of pollutant emissions in circulating vehicles, such as market surveillance and in-service conformity. In parallel, it is explained how the gradual introduction of small-scale devices aimed at the NOx control, such as lean NOx traps (LNTs) systems, and, most of all, the selective catalytic reduction (SCR) of NOx, permitted the application to road-transport vehicles of this ATS, originally designed in larger sizes for industrial usage. The paper reviews chemical processes occurring in SCR systems and their advantages and drawbacks with respect to the pollutant emission limits imposed by the legislation. Their potential side effects are also addressed, such as the emission of extra, not-yet regulated pollutants such as, for example, NH3 and N2O. The NOx, N2O, and NH3 emission level evolution with the various Euro standards for both light- and heavy-duty vehicles are reported in the light of experimental data obtained at the European Commission’s Joint Research Centre. It is observed that the new technologies, boosted by increasingly stricter legal limits, have led in the last two decades to a clear decrease of over one order of magnitude of NOx emissions in Diesel light-duty vehicles, bringing them to the same level as Euro 6 gasoline vehicles (10 mg/km to 20 mg/km in average). On the other hand, an obvious increase in the emissions of both NH3 and N2O is observed in both Diesel and gasoline light-duty vehicles, whereby NH3 emissions in spark-ignition vehicles are mainly linked to two-reaction mechanisms occurring in three-way catalysts after the catalyst light-off and during engine rich-operation. NH3 emissions measured in recent Euro 6 light-duty vehicles amount to a few mg/km for both gasoline and Diesel engines, whereby N2O emissions exceeding a dozen mg/km have been observed in Diesel vehicles only. The present paper can be regarded as part of a general assessment in view of the next EU emission standards, and a discussion on the role the SCR technology may serve as a NOx emission control strategy from lean-burn vehicles.

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Section: Scr On Filtersmentioning

confidence: 99%

An Overview of Lean Exhaust deNOx Aftertreatment Technologies and NOx Emission Regulations in the European Union

et al. 2021

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“…In the recent years, several strategies have been implemented by automotive manufacturers in order to comply with the CO 2 emission targets imposed by many nations (e.g., 95 g/km in the European Union by 2021) [1]. Diesel engines provide a good efficiency, but they require a complex after-treatment apparatus [2] and they have encountered a decline in popularity in recent years; hence, many efforts have been devoted to improving the overall fuel economy of gasoline engines. Among the different solutions developed, the Gasoline Direct Injection (GDI) technology presents several advantages with respect to Port Fuel Injection (PFI), since a GDI engine can work with higher efficiency and lower fuel consumption [3].…”

Section: Introductionmentioning

confidence: 99%

Nanostructured Equimolar Ceria-Praseodymia for Total Oxidations in Low-O2 Conditions

et al. 2020

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A Gasoline Particulate Filter (GPF) can be an effective solution to abate the particulate matter produced in modern direct injection gasoline engines. The regeneration of this system is critical, since it occurs in oxygen deficiency, but it can be promoted by placing an appropriate catalyst on the filter walls. In this paper, a nanostructured equimolar ceria-praseodymia catalyst, obtained via hydrothermal synthesis, was characterized with complementary techniques (XRD, N2-physisorption, FESEM, XPS, Temperature Programmed Reduction, etc.) and its catalytic performances were investigated in low oxygen availability. Pr-doping significantly affected ceria structure and morphology, and the weakening of the cerium–oxygen bond associated to Pr insertion resulted in a high reducibility. The catalytic activity was explored considering different reactions, namely CO oxidation, ethylene and propylene total oxidation, and soot combustion. Thanks to its capability of releasing active oxygen species, ceria-praseodymia exhibited a remarkable activity and CO2-selectivity at low oxygen concentrations, proving to be a promising catalyst for coated GPFs.

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“…Liquid AdBlue was simulated, with water and urea physical properties modeled as a function of temperature, using a specific size distribution for droplet initialization which was derived from the injector's manufacturer datasheet. A trapezoidal injection rate profile has been considered for UWS injection, with an injection frequency of 4 Hz, and each injection duration is of about 24 ms. A Kelvin-Helmholtz model [21] which was calibrated in a previous activity for a similar injector [22] has been adopted to account for droplets breakup. Other relevant settings adopted in 3D-CFD simulations were derived from [22] and are reported in Table 2.…”

Section: Numerical Analysismentioning

confidence: 99%

“…A trapezoidal injection rate profile has been considered for UWS injection, with an injection frequency of 4 Hz, and each injection duration is of about 24 ms. A Kelvin-Helmholtz model [21] which was calibrated in a previous activity for a similar injector [22] has been adopted to account for droplets breakup. Other relevant settings adopted in 3D-CFD simulations were derived from [22] and are reported in Table 2.…”

Section: Numerical Analysismentioning

confidence: 99%

“…To overcome this issue, the super-cycling approach [17] has been used, which iterates between fullycoupled gas-solid transient and solid-only steady-state solvers, to speed up simulation convergence towards steady-state system thermal conditions. Further details concerning the super-cycling modeling strategy can be found in [17,22].…”

Section: Thermal Boundary Conditions and Conjugate Heat Transfermentioning

confidence: 99%

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Experimental and Numerical Analysis of an Innovative Mixer Geometry for Urea Injection in SCR Applications

Millo

Sapio

Paradisi

et al. 2022

Emiss. Control Sci. Technol.

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Selective catalytic reduction (SCR), based on the injection of urea-water-solution (UWS), is one of the prevailing and more effective approaches to reduce NOx emissions in diesel engines. To improve the performance and durability of the system, it is crucial to develop reliable simulation tools able to correctly describe not only the urea conversion into ammonia and the mixing with exhaust gases but also the possible formation of solid deposits along with the engine’s exhaust line.In the present paper, two different exhaust systems for off-road applications are analyzed, both of them consisting of a diesel oxidation catalyst (DOC) followed by a diesel particulate filter (DPF), a UWS injection and a mixing device, and an SCR catalyst. Two alternative UWS mixing subsystems are evaluated, including a newly developed design. A 3D-CFD numerical analysis is carried out to assess the performance of both systems in terms of pressure drop, UWS spray, and liquid film development, in addition to flow velocities and species concentration uniformities at SCR catalyst inlet. A detailed analysis of droplet impingement on walls and liquid film development is enabled, thanks to a conjugate heat transfer (CHT) approach. Moreover, a deposit risk index is used to identify the areas of the systems where urea deposit formation is expected.Eventually, numerical results are compared with experiments on one operating condition chosen as the most challenging in terms of exhaust temperature and flow rate, both in terms of systems NOx conversion efficiency and deposit formation, showing a satisfactory agreement, thus paving the way to use the proposed synergetic numerical and experimental approach to further optimize the design and the system’s performance.

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Experimental and Numerical Analysis of Latest Generation Diesel Aftertreatment Systems

Cited by 6 publications

References 22 publications

An Overview of Lean Exhaust deNOx Aftertreatment Technologies and NOx Emission Regulations in the European Union

An Overview of Lean Exhaust deNOx Aftertreatment Technologies and NOx Emission Regulations in the European Union

Nanostructured Equimolar Ceria-Praseodymia for Total Oxidations in Low-O2 Conditions

Experimental and Numerical Analysis of an Innovative Mixer Geometry for Urea Injection in SCR Applications

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