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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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Experimental and Numerical Prediction of the Pressure Drop Reduction of Catalytic Converter under Various Mass Flow Rate of Exhaust Gas for a Naturally Aspirated Diesel Engine

Prince Shri Venkateshwara Engg. College-Edison Rajasingh
SRM Institute of Science and Technology-Sundararaj Senthilkumar
Published 2019-10-11 by SAE International in United States
Nowadays, Diesel emission control strategies are stringent across the globe which caused the rise in need of diesel after treat treatment devices that are more reliable and efficient. The optimized design of the catalytic converter aids in the durability of the product as well as the improvement in efficient operation of the Indian driving cycle. By changing the convergent and divergent cone angles of the catalytic converter, the consequential decrease in pressure drop leads to efficient flow of exhaust gases.The purpose of this study is to design, test, and analyse the catalytic converter in order to reduce the pressure drop in the exhaust system of a naturally aspirated diesel engine using both experimental and CFD techniques. In this study, a Diesel Oxidation Catalyst Catalytic Converter is investigated. For numerical analysis, ANSYS Fluent is used. Validation is done on baseline Catalytic converter pressure drop results obtained both numerically and experimentally for various speeds conditions and it is found that a reasonably good agreement exists. From the analytical calculations, Catalytic converter diameter, length and Cone angle are…
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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 the Emission Conversion Performance of Gasoline Particulate Filters Over Lifetime

Corning GmbH-Dominik Rose, Thorsten Boger
FEV Europe GmbH-Christof Schernus, Michael Görgen, Jim Cox, Martin Nijs, Johannes Scharf
Published 2019-09-09 by SAE International in United States
Gasoline particulate filters (GPF) recently entered the market, and are already regarded a state-of-the-art solution for gasoline exhaust aftertreatment systems to enable EU6d-TEMP fulfilment and beyond. Especially for coated GPF applications, the prognosis of the emission conversion performance over lifetime poses an ambitious challenge, which significantly influences future catalyst diagnosis calibrations. The paper presents key-findings for the different GPF application variants. In the first part, experimental GPF ash loading results are presented. Ash accumulates as thin wall layers and short plugs, but does not penetrate into the wall. However, it suppresses deep bed filtration of soot, initially decreasing the soot-loaded backpressure. For the emission calibration, the non-linear backpressure development complicates the soot load monitoring, eventually leading to compromises between high safety against soot overloading and a low number of active regenerations. In the second part, a relevant share of ash deposits inside three-way catalysts (TWC) is depicted. In an experiment, the oxygen storage capacity (OSC) of a three-way catalyst was significantly lowered by ash, while a coated GPF showed little effects. A subsequent OSC regeneration…
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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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One-Dimensional Modeling of a Thermochemical Recuperation Scheme for Improving Spark-Ignition Range Extender Engine Efficiency

Univ of Minnesota-Twin Cities-William F. Northrop, Darrick Zarling
  • Technical Paper
  • 2019-24-0066
Published 2019-09-09 by SAE International in United States
Range extender (REx) engines have promise for providing low-cost energy for future battery electric vehicles. Due to their restricted operation range, REx engines provide an opportunity to implement system-level schemes that are less attractive for engines designed for highly transient operation. This paper explores a thermochemical recuperation (TCR) scheme for a 2-cylinder BMW spark-ignition REx engine using a 1-D model implemented in GT-Power™. The TCR reactor employs a unique catalytic heat exchange configuration that enables efficient transfer of exhaust sensible and chemical enthalpy to steam reform the incoming fuel. The engine model without the TCR reactor was validated using experimental emissions and performance data from a BMW engine operating on a test stand. A custom integrated heat exchanger and catalyst model was created and integrated with the validated engine. A parametric modeling sweep was conducted with iso-octane as fuel over a range of reformed fuel fraction. With the TCR reactor operating at a molar steam to carbon ratio of 1.0, engine efficiency was increased by 2.9% over the baseline REx engine within the most efficient…
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Development of a Dedicated CNG Three-Way Catalyst Model in 1-D Simulation Platforms

FPT Industrial SpA-Stefano Golini, Francesco Giovanni Rutigliano
Istituto Motori CNR-Carlo Beatrice, Valentina Fraioli
Published 2019-09-09 by SAE International in United States
A growing interest towards heavy-duty engines powered with NG, dictated by stringent regulations in terms of emissions, has made it essential to study a specific Three-Way Catalyst (TWC). Oxygen storage phenomena characterize the catalytic converter efficiency under real world driving operating conditions and, consequently, during strong dynamics in Air-to-Fuel ratio (AFR).A numerical “quasi-steady” model has been set-up to simulate the chemical process inside the reactor. A dedicated experimental campaign has been performed in order to evaluate the catalyst response to a defined λ variation, thus providing the data necessary for the numerical model validation. In fact, goal of the present research activity was to investigate the effect of very fast composition transitions of the engine exhaust typical of the mentioned driving conditions (including fuel cutoffs etc.) on the catalyst performance and on related emissions.A surface reactions kinetic mechanism, representing CH4, CO, H2 oxidation and NO reduction, has been appropriately calibrated in steady-state operation, using a step-by-step procedure all over the engine operating conditions at different AFRs. Then transient conditions were numerically reproduced, through cyclical and…
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Exhaust Purification Performance Enhancement by Early Activation of Three Way Catalysts for Gasoline Engines Used in Hybrid Electric Vehicles

NE Chemcat Corporation-Makoto Nagata
Waseda Univesity-Toshinori Okajima, Ryota Sone, Xieyang Yan, Ryoya Inoue, Suchitra Sivakumar, Hajime Shingyouchi, Jin Kusaka, Kyohei Yamaguchi
Published 2019-09-09 by SAE International in United States
Three-way catalyst (TWC) converters are used to remove harmful substances (e.g., carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC)) emitted from gasoline engines. However, a large amount of emissions could be emitted before the TWC reaches its light-off temperature during a cold start. For hybrid electric vehicles (HEVs) powered by gasoline engines, the emission purification performance by TWC converters unfortunately deteriorates because of mode switching from engine to battery and vice versa, which can repeatedly generate cold start conditions for the TWCs. In this study, aiming to reduce emissions from series HEVs by early activation of TWCs, numerical simulations and experiments are carried out. An HEV is tested on a chassis dynamometer in the Worldwide Light-duty Test Cycle (WLTC) mode. The upstream and downstream gas conditions of the close-coupled catalyst converter are measured. A test piece is taken from the same catalyst and used in model gas experiments to decide the chemical reaction scheme and each corresponding reaction rate parameter. A 1-D numerical simulation TWC model, which includes 13 chemical species with 22 global…
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A New Take on Porous Medium Approach for Modelling Monoliths and Other Multiple Channel Devices

Coventry University-Gianluca Padula, Jonathan Saul, Svetlana Aleksandrova, Humberto Medina, Stephen Benjamin
  • Technical Paper
  • 2019-24-0049
Published 2019-09-09 by SAE International in United States
The porous medium approach is widely used to represent high-resistance devices, such as catalysts, filters or heat exchangers. Because of its computational efficiency, it is invaluable when flow losses need to be predicted on a system level. One drawback of using the porous medium approach is the loss of detailed information downstream of the device. Correct evaluation of the turbulence downstream affects the calculation of the related properties, e.g. heat and mass transfer.The novel approach proposed in the current study is based on a modified distribution of the resistance across the porous medium, which allows to account for the single jets developing in the small channels, showing an improved prediction of the turbulence at the exit of the device, while keeping the low computational demand of the porous medium approach.The benefits and limitations of the current approach are discussed and presented by comparing the results with different numerical approaches and experiments. The flexibility of the proposed approach in terms of describing the device geometry is demonstrated via an optimisation study where the size of the…
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Heat Transfer Analysis of Catalytic Converters during Cold Starts

Aristotle University Thessaloniki-Grigorios Koltsakis
Empa-Viola Papetti, Panayotis Dimopoulos Eggenschwiler
Published 2019-09-09 by SAE International in United States
The transient heat transfer behavior of an automotive catalytic converter has been simulated with OpenFOAM in 1D. The model takes into consideration the gas-solid convective heat transfer, axial wall conduction and heat capacity effects in the solid phase, but also the chemical reactions of CO oxidation, based on simplified Arrhenius and Langmuir-Hinshelwood approaches. The associated parameters are the results of data in literature tuned by experiments. Simplified cases of constant flow rates and gas temperatures in the catalyst inflow have been chosen for a comprehensive analysis of the heat and mass transfer phenomena. The impact of inlet flow temperatures and inlet flow rates on the heat up characteristics as well as in the CO emissions have been quantified. A dimensional analysis is proposed and dimensionless temperature difference and space-time coordinates are introduced. Using this suitably modified coordinates, for the case of negligible axial solid conduction, computed solid temperature at the reactor outlet lay on a typical S-curve, allowing the introduction of an analytical function. A series of variations in the inlet exhaust temperature and mass…
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