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Experimental tests on the feasibility of passive regeneration in a catalytic DPF at the exhaust of a light-duty Diesel engine

Univ. Of Salerno-Eugenio Meloni
Universita Degli Studi Di Salerno-Bruno Rossomando
  • Technical Paper
  • 2019-24-0045
To be published on 2019-08-15 by SAE International in United States
Diesel engines are attractive thanks to good performance in terms of fuel consumption, drivability, power output and efficiency. Nevertheless in the last years, increasing restrictions have been imposed to particulate emissions, concerning both mass (PM) and number (PN). Different technologies have been proposed to meet emissions standards and the wall-flow Diesel Particulate Filter (DPF) is currently the most common after-treatment system used to trap PM from the exhaust gases. This technology exhibits good features such that it can be regenerated to remove any accumulation of PM. However, this process involves oxidation of the filtered PM at a high temperature through after and post fuel injection strategies, which results in an increase of fuel consumption and may lead to physical damages of the filter in the long term. This work deals with the experimental testing of a catalytic silicon carbide (SiC) wall flow DPF, aiming at decreasing the soot oxidation temperature. The catalyst (CuFe2O4) was deposited on the filter by means of an optimized procedure based on a preliminary controlled chemical erosion of the SiC porous…
 

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…
 

Experimental and Computational Investigation of Particle Filtration Mechanisms in Partially Damaged DPFs

University of Thessaly-Onoufrios Haralampous, Marios Mastrokalos, Foteini Tzorbatzoglou, Chris Dritselis
  • Technical Paper
  • 2019-24-0149
To be published on 2019-08-15 by SAE International in United States
Since September 2018 new threshold limits are applied in the European Union for On-Board Diagnosis (OBD) of particulate mass (PM) leakage. OBD systems are obliged to detect exhaust system malfunctions that account to 2.5 times higher PM emissions compared to the type approval limit. Often the malfunction is located in the Diesel Particulate Filter (DPF), which might suffer substrate crack or melting during harsh regeneration events. In addition, DPF systems have become a tampering target, usually to avoid the high cost of replacement or lower fuel consumption. In this context, understanding the filtration mechanisms in partially damaged DPFs can facilitate the assessment of their environmental effects and the design of exhaust systems with efficient OBD functionality. Two common types of DPF failure are included in this study, namely partial rear plug removal and internal crack development due to uncontrolled regeneration with excessive soot loading. Two respectively damaged SiC filters were loaded with soot on the engine bench applying a specially designed protocol to access the effect of mass flow rate, temperature and deposit loading on…
 
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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 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 test conditions, the…
 

Phenomenological Investigations of Mid-Channel Ash Deposit Formation and Characteristics in Diesel Particulate Filters

Cummins Inc.-Yujun Wang
Massachusetts Institute of Technology-Carl Justin Kamp, Sujay Bagi
Published 2019-04-02 by SAE International in United States
Accumulation of lubricant and fuel derived ash in the diesel particulate filter (DPF) during vehicle operation results in a significant increase of pressure drop across the after-treatment system leading to loss of fuel economy and reduced soot storage capacity over time. Under certain operating conditions, the accumulated ash and/or soot cake layer can collapse resulting in ash deposits upstream from the typical ash plug section, henceforth termed mid-channel ash deposits. In addition, ash particles can bond (either physically or chemically) with neighboring particles resulting in formation of bridges across the channels that effectively block access to the remainder of the channel for the incoming exhaust gas stream. This phenomenon creates serious long-term durability issues for the DPF, which often must be replaced. Mid-channel deposits and ash bridges are extremely difficult to remove from the channels as they often sinter to the substrate.The current study is comprised of analyzing field-return/field-aged DPF units exhibiting variations in ash bridging, characterized by high resolution X-ray CT, XRD, XRF and SEM-EDS. X-ray CT with a transmission X-ray source (voxel size…
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Quantitative Analysis of Ash Density and Ash Distribution inside DPF Honeycomb Channels Based on X-ray Computed Tomography

MIT-Yuesen Wang, Victor Wong
Published 2019-04-02 by SAE International in United States
Simulation of soot and ash deposits in diesel particulate filters (DPF) often assumes uniform distributed cake-layer and/or plug accumulation at the very end section of the inlet channels, which may not reflect some conditions in the field. For example, cake-layer thickness changes along the filter length, and plugs show up not only at the end section but also at the middle section or even near the inlet section. This paper presents detailed microscopic analytical techniques which have been developed and applied to quantitatively derive the density and distribution of ash deposits inside DPF honeycomb monoliths. The ash loading experiments were done in a combined engine/burner test facility. Specifically, X-Ray tomography (X-Ray CT) was used extensively, which has the advantage of non-contaminating the ash deposits. A unique 2D and 3D data processing procedure was developed so that quantitative and statistical analyses could be done to extract ash layer/end-plug deposition information. With the technique, the quantitative ash distribution information will be useful as inputs to theoretical model for better and more accurate analysis and prediction. The key…
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Experimental and Computational Study of DOC on CSF for Heavy Duty Diesel Applications

Johnson Matthey Inc.-Sharan Sethuraman, Siddarth Sitamraju, Yaritza M Lopez-De Jesus, Penelope Markatou
Published 2019-04-02 by SAE International in United States
For diesel exhaust aftertreatment applications with space limitations, as well as to move the selective catalytic reduction system (SCR) to a warmer location closer to the engine, DOC on CSF technology can be used. This technology combines the diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF) functionalities in one component, thereby enabling volume reduction. DOC on CSF maintains the abatement of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM), and the oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) for passive soot oxidation and fast SCR reaction of NOx on a downstream SCR catalyst. In this study, the performance of DOC on CSF was compared to a DOC + bare diesel particulate filter (DPF) and a DOC + CSF system, to understand the performance benefits and challenges.All the components were optimized individually for their respective functions. The DOC on CSF was optimized for NO oxidation and passive soot oxidation performance. Experimental data and simulations were used to understand the underlying mechanisms in the DOC on CSF technology. Steady state HC oxidation under…
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Development and Experimental Validation of a Control Oriented Model of a Catalytic DPF

Università di Salerno-Federica D'Aniello, Bruno Rossomando, Ivan Arsie, Cesare Pianese
Published 2019-04-02 by SAE International in United States
1The wall-flow Diesel Particulate Filter (DPF) is currently the most common after-treatment system used to meet the particulate emissions regulations for automotive engines. Today’s technology shows the best balance between filtration efficiency and back-pressure in the engine exhaust pipe. During the accumulation phase the pressure drop across the filter increases, thus requiring periodic regeneration of the DPF through after and post fuel injection strategies. This paper deals with the development of a control oriented model of a catalytic silicon carbide (SiC) wall flow DPFs with CuFe2O4 loading for automotive Diesel engines. The model is intended to be used for the real-time management of the regeneration process, depending on back-pressure and thermal state. In order to ensure suitable computational demand and to realize emissions control and fuel economy objectives, the 0-D model has been developed with the aim of investigating the essential behavior of the system, such as the chemical kinetic of filtered soot oxidation, the thermal and backpressure dynamics along accumulation and regeneration processes. Parameters identification and model validation have been performed vs. experimental data…
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NOx Performance Degradation of Aftertreatment Architectures Containing DOC with SCR on Filter or Uncatalyzed DPF Downstream of DEF Injection

Deere & Company-Eric Hruby, Shyan Huang, Ramesh Duddukuri, Danan Dou
Published 2019-04-02 by SAE International in United States
SCR on filter, also known as SCRoF, SCRF, SDPF, has been utilized to meet the stringent light duty Euro 6 emission regulations. Close-coupled DOC-DEF-SCR on filter with underfloor SCR architectures, offer a balance of NOx performance at cold start and highway driving conditions. In contrast, the DOC-DPF-DEF-SCR architecture has been most commonly selected to meet the on-road and non-road heavy duty emission regulations worldwide.Diesel engines applied to off road vehicles can operate under higher loads for extended times, producing higher exhaust temperatures and engine out NOx emissions. New European Stage V emission regulations will mandate diesel particulate filter (DPF) adoption because of particulate number and more stringent particulate mass requirements. Three aftertreatment architecture choices with diesel particulate filters (DPF) were evaluated as candidates to fulfill the Stage V emission regulations. The studied architectures were: DOC-uncatalyzed DPF-DEF-SCR, DOC-DEF-SCR on filter-SCR and DOC-DEF-uncatalyzed DPF-SCR, respectively.During steady state operations, an unexpected continuous and repeatable NOx performance degradation occurred at inlet temperatures exceeding 450 °C on systems containing either SCR on filter or uncatalyzed DPF located downstream of the…
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Estimation of Soot and Fuel Invasion in Diesel Engine Oils through a Combination of Dielectric Constant Sensor and Viscosity Sensor

Harbin Institute of Technology (Weihai)-Yitao Shen, Ting Hu, Yanyan Wang
Published 2019-04-02 by SAE International in United States
To satisfy the latest emission standards, the use of advanced technologies such as exhaust gas recirculation, diesel particulate filter, and complicated injection strategies are increasing in modern diesel engines. However, some of these complicated technologies may cause soot and diesel fuel to enter the engine oil during engine operation and ultimately affect oil performance. Once the soot and diesel fuel content is beyond a certain level, the engine oil should be changed to guarantee adequate lubrication. Thus, a proper method of monitoring oil condition is required. It is well known that soot and diesel fuel affect oil permittivity and viscosity significantly. Thus, in this study, a new method to monitor oil quality is proposed by measuring the dielectric constant and oil viscosity. Carbon black was used as the substitute for soot and was mixed with diesel fuel at different ratios. Both the dielectric constant and oil viscosity increase as soot content increases. Diesel fuel content affects the viscosity and slightly affects the dielectric constant. Multivariable linear regression and an artificial neural network were used to…
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