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A Modeling Study of an Advanced Ultra-low NOx Aftertreatment System

SAE International Journal of Fuels and Lubricants

Michigan Technological University, USA-Venkata Rajesh Chundru, John H. Johnson, Gordon G. Parker
  • Journal Article
  • 04-13-01-0003
Published 2020-01-09 by SAE International in United States
The 2010 Environmental Protection Agency (EPA) Emission Standard for heavy-duty engines required 0.2 g/bhp-hr over certification cycles (cold and hot Federal Test Procedure [FTP]), and the California Air Resources Board (CARB) standards require 0.02 g/bhp-hr for the same cycles leading to a 90% reduction of overall oxides of nitrogen (NOx) emissions. Similar reductions may be considered by the EPA through its Cleaner Trucks Initiative program. In this article, aftertreatment system components consisting of a diesel oxidation catalyst (DOC); a selective catalytic reduction (SCR) catalyst on a diesel particulate filter (DPF), or SCR-F; a second DOC (DOC2); and a SCR along with two urea injectors have been analyzed, which could be part of an aftertreatment system that can achieve the 0.02 g/bhp-hr standard. The system performance was evaluated using validated one-dimensional (1D) DOC, two-dimensional (2D) SCR-F, and 1D SCR models at various combinations of inlet ammonia (NH3)-to-NOx ratio (ANR) values for the SCR-F and the SCR to determine the injection rates required to achieve an optimum nitrogen dioxide (NO2)/NOx ratio at the inlets of both the…
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Advanced analytical methods for the study of lubricant-derived ash and associated impacts on engine aftertreatment components

Massachusetts Institute of Technology-Sujay Dilip Bagi
Massachusetts Institute of Technology Kymanetics, Inc.-Carl Justin Kamp
  • Technical Paper
  • 2019-01-2293
Published 2019-12-19 by SAE International in United States
Catalytic and non-catalytic engine aftertreatment components, such as the diesel oxidation catalyst (DOC), selective catalytic reduction on filter (SCRF), the gasoline particulate filter (GPF) and the diesel particulate filter (DPF) are complex, multifunctional emissions control technologies that are robustly designed for extended use in harsh automotive exhaust environments. Over the useful component lifetime, lubricant-derived inorganic and incombustible ash accumulates in and/or on the surface of the aforementioned aftertreatment components, resulting in degraded performance and other potential problems. In order to better understand effects of ash in such components, a multiscale analytical approach is necessary, requiring a variety of experimental tools. This paper will briefly present a decade of analytical experience at the Sloan Automotive Laboratory at the Massachusetts Institute of Technology and at Kymanetics, Inc., specific to the fundamental understanding of the accumulation of lubricant-derived ash in engine aftertreatment components. Several key experimental tools and techniques will be reviewed including focused ion beam milling (SEM), in-situ X- ray diffraction (XRD), atomic force microscopy (AFM), ultra-high resolution X-ray computed tomography (CT), X-ray fluorescence (XRF), environmental scanning…
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Analysis of NH3 Diffusion Phenomena in a Selective Catalytic Reduction Coated Diesel Particulate Filter Catalyst Using a Simple One-Dimensional Core Model

Waseda University-Ken Sahara, Yoshihisa Tsukamoto, Akihisa Ishimaru, Takao Fukuma, Jin Kusaka
  • Technical Paper
  • 2019-01-2236
Published 2019-12-19 by SAE International in United States
This paper describes a method for estimating constants related to NH3 gas diffusion phenomena to the active sites in a selective catalytic reduction diesel particulate filter (SCR/DPF) catalyst. A simple one-dimensional NH3 gas diffusion model based on the pore structure inside the catalyst was developed and used to estimate the intracrystalline diffusion coefficient. It was shown that the estimated value agreed well with experimental data.
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Direct Visualization of Soot and Ash Transport in Diesel Particulate Filters during Active Regeneration Process

Japan Automobile Research Institute-Mayumi Matsuno, Takaaki Kitamura
  • Technical Paper
  • 2019-01-2287
Published 2019-12-19 by SAE International in United States
This study employed a diesel particulate generator (DPG), with an installed engine oil injector for soot and ash accumulation in a diesel particulate filter (DPF). Ash was generated by engine oil injection into the diesel burner flame. The amount of soot accumulation per loading varied from 0.5 g/L to 8 g/L while ash accumulation amount per loading was maintained at 0.5 g/L.Initially, ash accumulation distribution in the DPF was visualized using X-ray computed tomography (CT). It was revealed that the form of ash accumulation changed depending on the amount of soot accumulation before active regeneration, i.e., a large amount of soot accumulation resulted in plug ash, whereas a small amount of soot accumulation resulted in wall ash.To clarify ash accumulation mechanisms, soot and ash transport behavior in DPF during active regeneration process was directly observed using a high-speed camera through an optically accessible D-shaped cut DPF covered with a quartz glass plate.From the results, it was found that for larger amounts of soot accumulation, the lump of soot in the soot cake layer was transported…
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Study for Effects of Bio-Diesel Fuel and After-Treatment Systems on Formation and Reduction of Particles from Diesel Engines

TOKYO DYLEC Corp., and Pollars Laboratory Co., Ltd.-Jun Kawase, Ryuichi Suzuki
Teikyo University-Kazutoshi Mori
  • Technical Paper
  • 2019-01-2290
Published 2019-12-19 by SAE International in United States
Diesel engines are highly potential for better fuel economy due to a high thermal efficiency and fuel diversity. They are largely expected to contribute to a low carbon society in the future. Diesel engines have been developed for the purpose of controlling global warming and improving the air quality and health effects in the world. Although particles produced by combustion in cylinders of the diesel engines are emitted to the air, they are dramatically reduced by beyond 99.9% after being trapped by a diesel particulate filter (DPF) and a diesel oxidation catalyst (DOC) of the after-treatment systems. However phenomena of the formation of the particles in the cylinders and exhaust behaviors of the particles after being trapped by the DPF are not clearly explained yet (1)-(6) and effects of the DOC on the formation and the reduction of the particles are still not clarified (7)(8). This study analyzed particle distributions, particle number (PN) and particle components with diesel and bio-diesel fuel (BDF). First, this paper describes that the BDF more reduced the engine out PN…
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Prediction of Oil Dilution by Post-injection in DPF Regeneration Mode

Japan Automobile Research Institute-Takayuki Ito, Takaaki Kitamura
Kyoto University-Hiroshi Kawanabe
  • Technical Paper
  • 2019-01-2354
Published 2019-12-19 by SAE International in United States
This work investigated the mechanism of oil dilution by post injection to remove accumulated particulate matter on the diesel particulate filter of diesel engines. We developed a model to simulate post injection spray under low ambient gas pressure conditions. The model can predict the quantity of fuel mass adhered on the cylinder wall. The adhered fuel enters oil sump through the piston ring and cause oil dilution. The fuel in diluted oil evaporates during normal engine operations. We focus on the mechanism of fuel evaporation from diluted oil. The effects of engine speed and oil temperature on the evaporation were investigated. The results showed that the fuel evaporation rate increases with increasing engine speed and oil temperature. Furthermore, we developed an empirical model to predict the fuel evaporation rate of diluted oil through regression analysis with measured data. The model was validated using two test engines at three constant speed conditions and two transient cycles. Oil dilution predicted by the model showed good agreements with measured data from gas chromatography. The effects of piston ring…
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Phenomena of PM Deposition and Oxidation in the Diesel Particulate Filter

Nagoya University-Maki Nakamura, Masakuni Ozawa
  • Technical Paper
  • 2019-01-2288
Published 2019-12-19 by SAE International in United States
The diesel particulate filter (DPF) has attracted strong attention as a desirable after-treatment device for the particulate matter (PM) contained in exhaust gas of diesel engine. When particulate matter was deposited on a DPF, the pressure drop increases due to the PM trapping in the surface cavities of the DPF. After that, an active regeneration is required. Since more fuel is required for the regeneration in addition to the normal driving (passive regeneration), the fuel economy deteriorates. In order to improve the performance, a passive regeneration is necessary. In this study, we compared the dependence of the shape and depth of the cavity of the DPF on the PM trapping process by a comprehensive overall model and numerical calculation. We found that the pressure drop and elapsed time of the PM trapping varied, strongly depending on the cavity shape of the DPF surface. Further we examined the relative importance of the amount of PM deposit and the surface cavity shape of the DPF. We discovered that the pressure drop was lower when the shape of…
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Experimental Test on the Feasibility of Passive Regeneration in a Catalytic DPF at the Exhaust of a Light-Duty Diesel Engine

Universita Degli Studi Di Salerno-Bruno Rossomando, Ivan Arsie, Eugenio Meloni, Vincenzo Palma, Cesare Pianese
  • Technical Paper
  • 2019-24-0045
Published 2019-09-09 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 structure.…
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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, Enrico Sartoretti
Published 2019-09-09 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 or SCRF). 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 physical-chemical properties of the catalysts, 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 significant 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…
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Experimental and Computational Investigation of Particle Filtration Mechanisms in Partially Damaged DPFs

University of Thessaly-Onoufrios Haralampous, Marios Mastrokalos, Fotini Tzorbatzoglou, Chris Dritselis
Published 2019-09-09 by SAE International in United States
Understanding the filtration mechanisms in partially damaged Diesel Particulate Filters is very important for the design of exhaust systems with efficient On-Board Diagnosis functionality, especially as new threshold limits have been recently applied for particulate mass leakage. Two common types of DPF failure are included in this study, namely rear plug removal and internal failure due to uncontrolled regeneration with excessive deposit loading. Initially, the two respective filters were loaded on the engine bench with particle measurement upstream and downstream, and then they were disassembled and sectioned to study the deposit distribution. The analysis of the second filter revealed several modes of failure that should be expected under real-life conditions such as material accumulation in the inlet channels, substrate melting, and crosswise and diagonal crack development. Moreover, a computational model with the necessary adjustments is used to simulate the loading experiments and interpret the underlying filtration mechanisms. The processed results reveal small effects of temperature and mass flow rate on the filtration efficiency and a comparatively stronger impact of the total deposit loading. The local…
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