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Johnson, John H.
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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 upto 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 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 SCR-F and the SCR. A strategy was developed that…
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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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Extended Kalman Filter to Estimate NO, NO2, Hydrocarbon and Temperatures in a DOC during Active Regeneration and Under Steady State Conditions

Michigan Technological Univ-Harsha Shankar Surenahalli, Gordon Parker, John H. Johnson
Published 2015-04-14 by SAE International in United States
Diesel Oxidation Catalysts (DOC) are used on heavy duty diesel engine applications and experience large internal temperature variations from 150 to 600°C. The DOC oxidizes the CO and HC in the exhaust to CO2 and H2O and oxidizes NO to NO2. The oxidation reactions are functions of its internal temperatures. Hence, accurate estimation of internal temperatures is important both for onboard diagnostic and aftertreatment closed loop control strategies. This paper focuses on the development of a reduced order model and an Extended Kalman Filter (EKF) state estimator for a DOC. The reduced order model simulation results are compared to experimental data. This is important since the reduced order model is used in the EKF estimator to predict the CO, NO, NO2 and HC concentrations in the DOC and at the outlet. The estimator was exercised using transient drive cycle engine data. The closed loop EKF improves the temperature estimate inside the DOC compared to the open loop estimator. This is supported by the lower error in the estimated NO2 concentrations at the DOC outlet. The…
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A Modeling Study of the Exhaust Flow Rate and Temperature Effects on the Particulate Matter Thermal Oxidation Occurring during the Active Regeneration of a Diesel Particulate Filter

Michigan Technological Univ-Kiran C. Premchand, Krishnan Raghavan, John H. Johnson
Published 2015-04-14 by SAE International in United States
Numerical models of aftertreatment devices are increasingly becoming indispensable tools in the development of aftertreatment systems that enable modern diesel engines to comply with exhaust emissions regulations while minimizing the cost and development time involved. Such a numerical model was developed at Michigan Technological University (MTU) [1] and demonstrated to be able to simulate the experimental data [2] in predicting the characteristic pressure drop and PM mass retained during passive oxidation [3] and active regeneration [4] of a catalyzed diesel particulate filter (CPF) on a Cummins ISL engine.One of the critical aspects of a calibrated numerical model is its usability - in other words, how useful is the model in predicting the pressure drop and the PM mass retained in another particulate filter on a different engine without the need for extensive recalibration. Towards this objective, data acquired during the active regeneration of a CPF on a John Deere (JD) engine at 2200 and 1500 RPM, each at CPF inlet temperatures of 550, 575, 600 and 625 °C was used to develop calibration parameters for…
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Nonuniformity and NO2/NOx Ratio Effects on the SCR Performance under Transient Engine Conditions

Michigan Technological Univiersity-Xiaobo Song, Jeffrey Naber, John H. Johnson
Published 2014-04-01 by SAE International in United States
Selective catalytic reduction (SCR) systems are in use on heavy duty diesel engines for NOx control. An SCR NOx reduction efficiency of higher than 95% is required to meet the proposed increasingly stringent NOx emission standards and the 2014-2018 fuel consumption regulations. The complex engine exhaust conditions including the nonuniformity of temperature, flow, and maldistribution of NH3 present at the catalyst inlet need to be considered for improved performance of the SCR system. These factors cause the SCR to underperform negatively impacting the NOx reduction efficiency as well as the NH3 slip.In this study, the effects of the nonuniformity of temperature, flow velocity and maldistribution of NH3 on the SCR performance were investigated using 1-dimensional (1D) model simulations for a Cu-zeolite SCR. The model was previously calibrated and validated to reactor and steady-state and transient engine experimental data. The SCR engine experimental measurements collected from a transient cycle were used as the baseline for the simulations. The model was configured to include multiple axial channels running in parallel. Different inputs were assigned to the channels…
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Particulate Matter and Nitrogen Oxides Kinetics Based on Engine Experimental Data for a Catalyzed Diesel Particulate Filter

Michigan Technological University-Kiran C. Premchand, Harsha Surenahalli, John H. Johnson
Published 2014-04-01 by SAE International in United States
A numerical model to simulate the filtration and oxidation of PM as well as the oxidation of NO, CO and HC in a CPF was developed in reference [1]. The model consists of parameters related to filtration and oxidation of PM and oxidation of NO, CO and HC. One of the goals of this paper is to use the model to determine the PM and gaseous species kinetics for ULSD, B10 and B20 fuels using data from passive oxidation and active regeneration engine experimental studies.A calibration procedure to identify the PM cake and wall filtration parameters and kinetic parameters for the PM oxidation and NO, CO and HC oxidation was developed. The procedure was then used with the passive oxidation [2] and active regeneration [3] engine data. The tests were conducted on a 2007 Cummins ISL engine with a DOC and CPF aftertreatment system. The simulation results show good agreement with the experimental CPF pressure drop, PM mass retained measurements and the outlet NO, NO2, CO and HC concentrations. The results show that for both…
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Development of the Methodology for Quantifying the 3D PM Distribution in a Catalyzed Particulate Filter with a Terahertz Wave Scanner

Cummins Inc.-Leigh Rogoski
Michigan Technological University-Ryan Foley, Jeffrey Naber, John H. Johnson
Published 2014-04-01 by SAE International in United States
Optimizing the performance of the aftertreatment system used on heavy duty diesel engines requires a thorough understanding of the operational characteristics of the individual components. Within this, understanding the performance of the catalyzed particulate filter (CPF), and the development of an accurate CPF model, requires knowledge of the particulate matter (PM) distribution throughout the substrate. Experimental measurements of the PM distribution provide the detailed interactions of PM loading, passive oxidation, and active regeneration. Recently, a terahertz wave scanner has been developed that can non-destructively measure the three dimensional (3D) PM distribution. To enable quantitative comparisons of the PM distributions collected under different operational conditions, it is beneficial if the results can be discussed in terms of the axial, radial, and angular directions. This paper focuses on the development of an analysis method and metrics that quantitatively describe the PM distribution in the aforementioned directions. The metrics are a uniformity index (UI) and the 95th percentile range (PR). A uniformity index (UI) metric is further employed to qualify the 3D distribution as uniform or not. The…
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A Modeling Study of SCR Reaction Kinetics from Reactor Experiments

Michigan Technological University-Xiaobo Song, Gordon Parker, John H. Johnson, Jeffrey Naber
Oak Ridge National Laboratory-Josh Pihl
Published 2013-04-08 by SAE International in United States
In order to further characterize and optimize the performance of Selective Catalytic Reduction (SCR) aftertreatment systems used on heavy-duty diesel engines, an accurately calibrated high-fidelity multi-step global kinetic SCR model and a reduced order estimator for on-board diagnostic (OBD) and control are desirable. In this study, a Cu-zeolite SCR catalyst from a 2010 Cummins ISB engine was experimentally studied in a flow reactor using carefully designed protocols. A 2-site SCR model describing mass transfer and the SCR chemical reaction mechanisms is described in the paper. The model was calibrated to the reactor test data sets collected under temperatures from 200 to 425 °C and SCR space velocities of 60000, 90000, and 120000 hr-1. The model parameters were calibrated using an optimization code to minimize the error between measured and simulated NO, NO₂, N₂O, and NH₃ gas concentration time histories. The calibrated SCR model is able to predict the effect of temperature and flow rate on SCR kinetics and is capable of predicting gaseous NO, NO₂, NH₃, N₂O, and NH₃ storage on the catalyst. The SCR…
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An Experimental Investigation into Particulate Matter Oxidation in a Catalyzed Particulate Filter with Biodiesel Blends on an Engine during Active Regeneration

Michigan Technological University-James Pidgeon, John H. Johnson, Jeffrey Naber
Published 2013-04-08 by SAE International in United States
Active regeneration experiments were carried out on a production 2007 Cummins 8.9L ISL engine and associated diesel oxidation catalyst (DOC) and catalyzed particulate filter (CPF) aftertreatment system. The effects of SME biodiesel blends were investigated to determine the particulate matter (PM) oxidation reaction rates for active regeneration. The experimental data from this study will also be used to calibrate the MTU-1D CPF model [1].The experiments covered a range of CPF inlet temperatures using ULSD, B10, and B20 blends of biodiesel. The majority of the tests were performed at a CPF PM loading of 2.2 g/L with in-cylinder dosing, although 4.1 g/L and a post-turbo dosing injector were also investigated. The PM reaction rate was shown to increase with increasing percent biodiesel in the test fuel as well as increasing CPF temperature. Additionally, the effectiveness of PM oxidation at a constant CPF temperature (grams of PM oxidized per gallon of dosing fuel) increased with increasing percent biodiesel.In an analysis of the CPF wall, cake, and channel resistance, it was determined that a correction factor was needed.…
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Development of a 1-D Catalyzed Diesel Particulate Filter Model for Simulation of the Oxidation of Particulate Matter and Gaseous Species During Passive Oxidation and Active Regeneration

Michigan Technological Univ.-Kiran C. Premchand, John H. Johnson, Song-Lin Yang
Published 2013-04-08 by SAE International in United States
Numerical modeling of aftertreatment systems has been proven to reduce development time as well as to facilitate understanding of the internal physical and chemical processes occurring during different operating conditions. Such a numerical model for a catalyzed diesel particulate filter (CPF) was developed in this research work which has been improved from an existing numerical model briefly described in reference.The focus of this CPF model was to predict the effect of the catalyst on the gaseous species concentrations and to develop particulate matter (PM) filtration and oxidation models for the PM cake layer and substrate wall so as to develop an overall model that accurately predicts the pressure drop and PM oxidized during passive oxidation and active regeneration. Descriptions of the governing equations and corresponding numerical methods used with relevant boundary conditions are presented.Calibration of the model was carried out using data obtained from passive oxidation as well as active regeneration experiments conducted on a Cummins ISL diesel engine using ultra-low sulfur diesel (ULSD) fuel with 10% (B10) and 20% (B20) bio-diesel blends and equipped…
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