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Optimization of the Exhaust Aftertreatment System of a Heavy Duty Engine by means of Variable Valve Timing

Technische Universität Braunschweig-Marius Betz, Peter Eilts
  • Technical Paper
  • 2019-24-0143
To be published on 2019-08-15 by SAE International in United States
In view of the current political debate, it can be assumed that the nitrogen oxide limits for commercial vehicles will be further reduced. This is also demonstrated by the currently voluntary certification of the CARB Optional Low NOX legislation, which requires nitrogen oxide emissions of 0.027 g / kWh. This corresponds to a reduction of 93% compared to the current EU VI standard. Therefore, the optimization of EAT systems represents an essential research focus for future commercial vehicle applications. One way to optimize the EAT system may be the usage of variable valve actuation. Existing investigations show an exhaust gas temperature increase with Miller timing, but the authors conclude that it cannot accelerate the heating process. With regard to the effects on the exhaust aftertreatment system and the resulting tailpipe emissions, only improved HC and CO oxidation could be identified so far. In addition, a potential for improved NOX reduction is expected in the exhaust gas temperature increase. Therefore, investigations are carried out at the Institute of Internal Combustion Engines of the Technical University of…
 

Diesel Vehicle with ultra-low NOx emissions in the city

AECC-Joachim Demuynck, Cecile Favre, Dirk Bosteels
IAV-Andreas Kuhrt, Joachim Spitta, Frank Bunar
  • Technical Paper
  • 2019-24-0145
To be published on 2019-08-15 by SAE International in United States
The paper discusses the technical approach to meet Euro 6d Real-Driving Emissions (RDE) requirements and beyond, with a particular focus on reducing diesel NOx emissions in urban driving situations. Novel technology aspects of the diesel powertrain are an RDE-optimized catalyst system layout to improve both low- and high-load DeNOx performance and a 48V P0-hybrid system. A key element of the powertrain concept is the advanced model based DeNOx control strategy. The optimized exhaust aftertreatment layout combines lean NOx Trap (LNT) and Selective Catalytic Reduction (SCR) technologies. For maximum low load DeNOx performance, the close-coupled SCR, consisting of an additional slice upstream of an SCR coated on filter, is assisted by an LNT. High load conditions are covered by a 2-stage SCR system with twin AdBlue® dosing. The P0 48V electric motor supports the NOx control in addition to ensuring good driving performance and fuel efficiency. A smart and advanced control strategy is implemented to ensure optimal interaction between all components. The first part of the proposed paper provides a brief summary of Euro 6d and…
 

Reactivity Analysis and Modeling of NOx purification Considering Reactions on Cu active sites and Brønsted acid sites in a Cu-chabazite SCR catalyst

Waseda Univ-TAKAO FUKUMA, Jin Kusaka
Waseda Univ.-Yoshihisa Tsukamoto
  • Technical Paper
  • 2019-24-0150
To be published on 2019-08-15 by SAE International in United States
In this study, the NOx purification reactivity of a Cu-chabazite SCR catalyst was analyzed over a wide temperature range based on the NH3-SCR mechanism considering Cu redox reactions and reactions on a Brønsted acid site. It was revealed that the De-NOx reactions on the active site of Cu proceeded in different paths at lower and higher temperatures. This means that the rate-limiting step of SCR reactions was changed as each temperature. The reaction rate of NOx purification on a Cu site less than 200 °C was determined by the reaction rate of oxidation of Cu sites. On the other hand, the NH3 adsorption on Cu sites played a dominant role in NOx purification at temperature range higher than 300°C. Moreover, it was also observed that the Cu reaction site took different states at low and high temperatures during the NOx purification and was estimated that the valence state of a Cu site was changed as the temperature increased. In order to analyze the reaction on a Brønsted acid site of chabazite structure, analysis using an…
 

Experimental and Numerical Analysis of Latest Generation Diesel Aftertreatment Systems

Cornaglia SpA-Alessio Tarabocchia
Politecnico di Torino-Francesco Sapio, Federico Millo, Debora Fino, Alessandro Monteverde
  • Technical Paper
  • 2019-24-0142
To be published on 2019-08-15 by SAE International in United States
A comprehensive experimental and numerical analysis of two state-of-the-art diesel AfterTreatment Systems (ATS) for automotive applications is presented in this work. Both systems, designed to fulfill Euro 6 emissions regulations standards, consist of a closed-coupled Diesel Oxidation Catalyst (DOC) followed by a Selective Catalytic Reduction (SCR) catalyst coated on a Diesel Particulate Filter (DPF), also known as SCR on Filter (SCRoF). While the two systems feature the same Urea Water Solution (UWS) injector, major differences could be observed in the UWS mixing device, which is placed upstream of the SCRoF, whose design represents a crucial challenge due to the severe flow uniformity and compact packaging requirements. First, both the ATS were experimentally characterized to determine the UWS spray characteristics (i.e. liquid penetration, droplets size) and to evaluate the NOx conversion efficiency under steady state flow conditions, representative of type-approval operating conditions. The experiments highlighted relevant differences in terms of NOx conversion efficiency between the two ATS, especially at low temperature operation. In order to highlight the root causes of these differences, a numerical analysis was…
 

Selection of Three Way Catalyst Converter for CNG engine to meet BSVI Emission Norms

VE Commercial Vehicles, Ltd.-Himanshu Gambhir
  • Technical Paper
  • 2019-24-0044
To be published on 2019-08-15 by SAE International in United States
Compressed natural gas (CNG) is a substitution of alternative fuel for automotive application with significant environmental advantages as it is the only fuel cheaper than gasoline or diesel, comparatively lower air pollution emissions, lesser CO2 emissions. Stringent regulations have been adopted to curb the menace of vehicular pollution. In order to meet the stringent regulations catalytic convertor using noble metals proved to a boon in vehicular industry. Noble metals are highly active for removal of methane as a pollutant. However, their expensiveness, deterioration with time can generate even more toxic volatile pollutants. The paper related to developing of a new gas engines with high energy efficiency and meeting future emission standards. It is necessary to develop complex exhaust gas after treatment systems to treat the toxic components efficiently when the engine runs on stoichiometric and lean mixtures. It is proposed to use new combination of three-way catalyst for working on stoichiometric mixtures and a selective catalytic reduction system for NOx after treatment on lean mixtures. This paper deals with the optimization of the catalytic convertor…
 

Multidimensional Modeling of SCR Systems via the Lattice Boltzmann Method

Tuscia University-Stefano Ubertini
Univ of Roma Tor Vergata-Giovanni Di Ilio
  • Technical Paper
  • 2019-24-0048
To be published on 2019-08-15 by SAE International in United States
In this paper, we deploy a novel, multidimensional approach to simulate SCR reactors across physical scales. For the first time, a full 3D Lattice Boltzmann (LB) solver is developed, able to accurately capture the fluid dynamic phenomena taking place inside SCR reactors, as well as the catalytic conversion of NOx. The influence of engine load on exhaust gas mass flow rate and catalytic converter activity is taken into account. The proposed approach is computationally light and the results prove the reliability and versatility of the LB Method for the simulation of the complex phenomena that take place inside the aftertreatment devices.
 

Chemical and Physical Characterization of Organic Particulate Matter from Last Generation Exhaust Aftertreatment System of Medium Duty Diesel Engine

Istituto Motori CNR-Ezio Mancaruso
Istituto Ricerche sulla Combustione-CNR-Barbara Apicella
  • Technical Paper
  • 2019-24-0053
To be published on 2019-08-15 by SAE International in United States
Particulate Matter from Euro 6 Medium Duty diesel engine was analyzed from engine-out, downstream of particulate filter (DPF), and up to the exit of a selective catalytic reactor (SCR) to characterize its chemical and physical nature. Particular attention was devoted to the analysis of particles down to 23 nm. An array of chemical, physical and spectroscopic techniques (Gas chromatography coupled with mass spectrometry (GC-MS), mobility analyzer, UV-visible absorption and fluorescence spectroscopy) was applied for characterizing the organic particulate matter (PM, constituted of polycyclic aromatic hydrocarbons (PAH), heavy aromatic compounds, soot) in the exhaust. The engine was operated at “full-load” (100% of the total power, representing the best performance of the engine operation) condition, and at different engine speeds. Results showed that the DPF efficiency was greater than 96% in the reduction of the sub 23 nm particles across the speeds range. Soot concentration in the exhaust after the DPF did not undergo any significant further concentration decrease after SCR. By contrast, PAH concentration was found decreasing of about 30 % after the SCR. Also, the…
 
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The Effect of NO2/NOx Ratio on the Performance of a SCR Downstream of a SCR Catalyst on a DPF

SAE International Journal of Fuels and Lubricants

Michigan Technological University, USA-Venkata Rajesh Chundru, Gordon G. Parker, John H. Johnson
  • Journal Article
  • 04-12-02-0008
Published 2019-06-14 by SAE International in United States
Different aftertreatment systems consisting of a combination of selective catalytic reduction (SCR) and SCR catalyst on a diesel particulate filter (DPF) (SCR-F) are being developed to meet future oxides of nitrogen (NOx) emissions standards being set by the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB). One such system consisting of a SCRF® with a downstream SCR was used in this research to determine the system NOx reduction performance using experimental data from a 2013 Cummins 6.7L ISB (Interact System B) diesel engine and model data. The contribution of the three SCR reactions on NOx reduction performance in the SCR-F and the SCR was determined based on the modeling work. The performance of a SCR was simulated with a one-dimensional (1D) SCR model. A NO2/NOx ratio of 0.5 was found to be optimum for maximizing the NOx reduction and minimizing NH3 slip for the SCR for a given value of ammonia-to-NOx ratio (ANR). The SCRF® + SCR system was simulated using the 2D SCR-F + 1D SCR system model. For all the…
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Experimental Analysis of SCR Spray Evolution and Sizing in High-Temperature and Flash Boiling Conditions

SAE International Journal of Fuels and Lubricants

Continental Automotive Systems US Inc., USA-Nic van
Universita degli Studi di Perugia, Italy-Gabriele Brizi, Lucio Postrioti
  • Journal Article
  • 04-12-02-0006
Published 2019-05-16 by SAE International in United States
In the last years, new stringent emission legislation in terms of nitrogen oxides (NOx) has been leading to a massive development of advanced after-treatment systems for diesel engines. Among them, selective catalytic reduction (SCR) technology has proved to be an effective approach for NOx reduction in a wide range of engine operating conditions. In SCR systems, the interaction between diesel exhaust fluid (DEF) and hot exhaust gas is crucial to promote the chemical reactions through which ammonia is produced. Hence, a proper matching between the exhaust pipe architecture and the DEF spray is mandatory for obtaining an adequate SCR efficiency, especially in close-coupled configurations and moderate exhaust gas temperature conditions. To this end, significant benefits could be derived via appropriate SCR injector thermal management, as the spray structure is significantly influenced by the DEF temperature upstream of the injector nozzle. In this article, the results of a spray analysis campaign carried out on a prototype DEF dosing system are presented. The goal of this research is to investigate the influence of both air and DEF…
 

Deposit Reduction in SCR Aftertreatment Systems by Addition of Ti-Based Coordination Complex to UWS

Southwest Research Institute-Cary Henry, Scott Eakle
University of Texas-San Antonio-Ryan Hartley, Zachary Tonzetich
Published 2019-04-02 by SAE International in United States
Formation of urea-derived deposits in selective catalytic reduction (SCR) aftertreatment systems continues to be problematic at temperatures at and below 215 °C. Several consequences of deposit formation include: NOx and NH3 slip, exhaust flow maldistribution, increased engine backpressure, and corrosion of aftertreatment components. Numerous methods have been developed to reduce deposit formation, but to date, there has been no solution for continuous low-temperature dosing of Urea-Water Solution (UWS). This manuscript presents a novel methodology for reducing low-temperature deposit formation in SCR aftertreatment systems. The methodology described herein involves incorporation and dissolution of an HNCO hydrolysis catalyst directly into the UWS. HNCO is a transient species formed by the thermolysis of urea upon injection of UWS into the aftertreatment system. Ideally HNCO undergoes hydrolysis to form NH3 and CO2, but under certain conditions HNCO may polymerize or react with other constituents in the exhaust. Reaction of HNCO with species other than water generally results in the formation of deposits in the aftertreatment system. Addition of an HNCO hydrolysis catalyst directly into the UWS provides maximum contact…
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