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Hierarchical Predictive Control of a Combined Engine/SCR System with Limited Model Knowledge

SAE International Journal of Engines

Friedrich-Alexander University Erlangen Nuremberg, Germany-Knut Graichen
MTU Friedrichshafen, Germany-Jens Niemeyer, Jörg Remele
  • Journal Article
  • 03-13-02-0015
Published 2020-01-16 by SAE International in United States
In this article, the problem of minimizing the overall operational cost of a heavy-duty off-highway diesel engine combined with a selective catalytic reduction (SCR) catalyst is considered. Here, we propose a hierarchical model-based scheme described as an optimal control problem. The sequence of resulting optimal control values are setpoints for the underlying engine controller, applied in a model predictive control (MPC) fashion. The presented scheme meets several demands. While minimizing the overall costs, it handles box constraints for the control variables as well as a nonlinear NOx-conversion rate constraint ensuring that a given emission target is met. The approach makes use of Gaussian process models for the input-output behavior of the underlying components and a technique for online adaptation. Thus, the presented hierarchical scheme is able to compensate model uncertainties and aging effects of engine, air path, and SCR catalyst. Moreover, in comparison to the literature, our approach doesn’t require detailed models of the underlying components, and the hierarchical, modular design allows the applicability to different engines and SCR controllers. We illustrate the proposed approach…
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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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A Study on the Performance Deterioration of SCR for Heavy-Duty Diesel Vehicles

Department of Automotive Engineering, Kookmin University-Seangwock Lee
Graduate School of Automotive Engineering, Kookmin Universit-Manjae Kwon, Giyoung Park, Hyunjae Lim, Jungjun Kim
  • Technical Paper
  • 2019-01-2235
Published 2019-12-19 by SAE International in United States
In this study, a six litres displacement, commercial vehicle engine that meets the EURO-5 regulation was used to evaluate the durability and performance deterioration of the SCR system mounted on a heavy-duty diesel vehicle. ESC and ETC modes were used for emission test. Characteristics of emissions by SCR catalyst deterioration were investigated using mileage vehicles of 0 km, 120,000 km, and 360,000 km. EDS (Energy Dispersive X-Ray Spectroscopy) analysis on PM filters and CT scan to catalyst substrate were carried out in order to investigate the status of catalyst by each mileage. As a result, it was found that NOX, slipped NH3 as well as PM due to unreacted ammonia and urea increased as the mileage of the catalyst increased.
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Design, Development and Analysis of Mullite Catalytic Converter for CI Engines

Kongu Engineering College-Selvakumar Pandiaraj, Dhamotharan Subbaiyan, Tamilvanan Ayyasamy, Sathishkumar Nagarajan
Published 2019-10-11 by SAE International in United States
Emissions of Hydrocarbon (HC), Carbon Monoxide (CO) and Oxides of Nitrogen (NOx) are the largest concerns for fossil fuel driven automotive vehicles. Catalytic converter is an important component in the selective catalytic reduction process. It oxidizes harmful CO and HC emission to CO2 and H2O in the exhaust system and thus the emission is controlled. Different kinds of problems are associated with noble metal based catalytic converter. A catalytic converter with a new catalyst for compression ignition engine is considered in this study. The catalytic converter is designed and developed with a new catalyst. Due to better durable characteristics and poison resistant nature, non-noble metal based material limestone (mullite) is selected as a catalyst for catalytic convertor and the emission characteristics are studied on four stroke single cylinder CI engine by using mullite based catalytic converter. The results are compared without catalytic converter in the same engine. In the design stage, the back pressure analysis is performed on perforated mullite plate with ANSYS software. After arriving satisfactory results, the design is taken for development. The…
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Study of NOx Reduction Efficiency in NSR and NSR-SCR Combined Systems

Vellore Institute of Technology-Saravanan Supramani, Ramesh Kumar Chidambaram
Published 2019-10-11 by SAE International in United States
The present study was carried out to analyze the catalytic action of K2O-Al2O3 in NOx Storage and Reduction (NSR) monolith catalyst and Fe2O3-TiO2 in Selective Catalytic Reduction (SCR) monolith catalyst. The core objective of this investigation is to determine the maximum percentage of Oxides of Nitrogen (NOx) reduction in NSR and NSR-SCR combined system with respect to engine exhaust gas temperature and compares the results with the results of the conventional mode of operation. To accomplish this task monolith ceramic bricks were coated with K2O-Al2O3 (NSR) and Fe2O3-TiO2 (SCR) catalyst and were placed in different configurations inside the catalytic chamber. Several trials were attempted to get the optimal operating temperature that has a maximum NOx removal efficiency when successively connecting a single NSR catalyst and the combined NSR-SCR double bed catalyst. Single NSR monolith at 320 °C, showed the best NOx conversion rate of 74%. The double NSR-SCR configuration permitted the SCR catalyst storing ammonia to respond with NOx leaving from the NSR. The SCR reaction between ammonia which leaves from NSR, later adsorbed by…
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A Novel 1D Co-Simulation Framework for the Prediction of Tailpipe Emissions under Different IC Engine Operating Conditions

Aristotle University of Thessaloniki-Grigorios Koltsakis, Zissis Samaras
EMPA-Panayotis Dimopoulos Eggenschwiler, Viola Papetti, Jakub Rojewski, Patrik Soltic
Published 2019-09-09 by SAE International in United States
The accurate prediction of pollutant emissions generated by IC engines is a key aspect to guarantee the respect of the emission regulation legislation. This paper describes the approach followed by the authors to achieve a strict numerical coupling of two different 1D modeling tools in a co-simulation environment, aiming at a reliable calculation of engine-out and tailpipe emissions. The main idea is to allow an accurate 1D simulation of the unsteady flows and wave motion inside the intake and exhaust systems, without resorting to an over-simplified geometrical discretization, and to rely on advanced thermodynamic combustion models and kinetic sub-models for the calculation of cylinder-out emissions. A specific fluid dynamic approach is then used to track the chemical composition along the exhaust duct-system, in order to evaluate the conversion efficiency of after-treatment devices, such as TWC, GPF, DPF, DOC, SCR and so on. This co-simulation environment is validated against a real engine configuration which was instrumented and tested at EMPA labs. A 4-cylinder SI, turbocharged, CNG engine is investigated at different loads and revolution speeds, to…
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Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Waseda Univ-Yoshihisa Tsukamoto, Takao Fukuma, Jin Kusaka
Published 2019-09-09 by SAE International in United States
The NOx-reducing activity of a Cu-chabazite selective catalytic reduction (SCR) catalyst was analyzed over a wide temperature range. The analysis was based on the ammonia SCR (NH3-SCR) mechanism and accounted for Cu redox chemistry and reactions at Brønsted acid sites. The reduction of NOx to N2 (De-NOx) at Cu sites was found to proceed via different paths at low and high temperatures. Consequently, the rate-limiting step of the SCR reaction at Cu sites varied with the temperature. The rate of NOx reduction at Cu sites below 200°C was determined by the rate of Cu oxidation. Conversely, the rate of NOx reduction above 300°C was determined by the rate of NH3 adsorption on Cu sites. Moreover, the redox state of the active Cu sites differed at low and high temperatures. To clarify the role of the chabazite Brønsted acid sites, experiments were also performed using a H-chabazite catalyst that lacks Cu sites. NOx reduction via the NO2-NH3 reaction was found to occur at Brønsted acid sites at high temperatures (up to 600°C). We also analyzed the…
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Analysis of TWC Characteristics in a Euro6 Gasoline Light Duty Vehicle

Aristotle University Thessaloniki-Grigorios Koltsakis
Empa-Viola Papetti, Panayotis Dimopoulos Eggenschwiler
Published 2019-09-09 by SAE International in United States
A Euro6 gasoline light duty vehicle has been tested at the engine dynamometer and the emissions have been analyzed upstream and downstream the Three-Way-Catalyst (TWC) during a WLTC cycle. Catalyst simulations have been used for assessing the processes inside the catalytic converter using a reaction scheme based on 19 brutto reactions (direct oxidation and reduction, selective catalytic reductions with CO, C3H6 and H2, steam reforming, water-gas shift and bulk ceria as well as surface ceria reactions). The reactions have been parameterized in order to best approximate the measurements.Based on the reactions taken into account, the real vehicle emissions can be predicted with good accuracy. The simulations show that the cycle emissions comprise mainly the cold start contribution as well as discrete emission break-through events during transients. During cold start no reactions are evident in the catalyst before the temperature of the gas entering the catalyst reaches 270°C. Following the light-off, prevailing reactions are direct oxidation as well as surface ceria reactions for CO and THC. NO reduction during cold start is due to reaction with…
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