Diesel Engine Aftertreatment Research Articles

Control-Oriented Modeling and Model-Based Estimation and Control for Diesel Engine Aftertreatment Systems

This article provides an overview of control-oriented modeling and model-based estimation and control for diesel engine aftertreatment systems. The chemical reactions and physical processes that occur in diesel engine after-treatment systems are quite complex. Computational models describing the chemical reaction kinetics, flow, and thermo-physical phenomena in engine exhaust aftertreatment systems have been coming forth since the 1960s when catalytic converters were introduced for vehicle applications {AQ: This word ‘catalystic’ is not found in standard dictionaries. Please check and correct if necessary.}. Such models can provide insightful understanding and mathematical descriptions on the chemical reactions, mass transfer, and heat transfer processes in one-dimensional and multi-dimensional fashions. The primary purpose of diesel engine aftertreatment system control-oriented models is to serve for the designs of real-time aftertreatment control and fault-diagnosis systems to reduce tailpipe emissions during real-world vehicle operations. Because such control-oriented models contain physically-meaningful parameters of the actual treatment systems, the model-based estimation and control algorithms can have excellent generalizability among different platforms.

Robust Nonlinear Disturbance Observer Design for Estimation of Ammonia Storage Ratio in Selective Catalytic Reduction Systems

Urea-based selective catalytic reduction (SCR) system is a promising way to obtain high NOx reduction and commonly adopted in diesel engine aftertreatment systems. The ammonia storage ratio is critical for SCR feedback control but it is difficult to be directly measured by sensors. This paper aims to effectively estimate the ammonia storage ratio on line and reduce the cost of using ammonia sensors. In the proposed method, the ammonia storage ratio is treated as an external disturbance in the NOx dynamic model and estimated by the nonlinear disturbance observer (NDO) methods. Furthermore, to reduce estimation errors of ammonia storage ratio caused by the high-frequency measurement noises, a novel robust nonlinear disturbance observer (robust NDO) is proposed and compared with a typical design method (regular NDO). Both the NDOs are developed based on part of the three-state SCR model and cost-effective, since NOx sensors are only used. The stability and noise attenuation properties of both estimations were also analyzed in the paper. The simulation results based on the full-vehicle simulator of FTP-75 test demonstrate that the regular NDO and the robust NDO can effectively estimate the ammonia storage ratio even in cases where ammonia cross-sensitivity affects the response. Among the two observers, the robust NDO has better noise attenuation properties.

Fuel efficient exhaust thermal management for compression ignition engines during idle via cylinder deactivation and flexible valve actuation

Fuel efficient thermal management of diesel engine aftertreatment is a significant challenge, particularly during cold start, extended idle, urban driving, and vehicle operation in cold ambient conditions. Aftertreatment systems incorporating NOx-mitigating selective catalytic reduction and diesel oxidation catalysts must reach ∼250 °C to be effective. The primary engine-out condition that affects the ability to keep the aftertreatment components hot is the turbine outlet temperature; however, it is a combination of exhaust flow rate and turbine outlet temperature that impact the warm-up of the aftertreatment components via convective heat transfer. This article demonstrates that cylinder deactivation improves exhaust thermal management during both loaded and lightly loaded idle conditions. Coupling cylinder deactivation with flexible valve motions results in additional benefits during lightly loaded idle operation. Specifically, this article illustrates that at loaded idle, valve motion and fuel injection deactivation in three of the six cylinders enables the following: (1) a turbine outlet temperature increases from ∼190 °C to 310 °C with only a 2% fuel economy penalty compared to the most efficient six-cylinder operation and (2) a 39% reduction in fuel consumption compared to six-cylinder operation achieving the same ∼310 °C turbine out temperature. Similarly, at lightly loaded idle, the combination of valve motion and fuel injection deactivation in three of the six cylinders, intake/exhaust valve throttling, and intake valve closure modulation enables the following: (1) a turbine outlet temperature increases from ∼120 °C to 200 °C with no fuel consumption penalty compared to the most efficient six-cylinder operation and (2) turbine outlet temperatures in excess of 250 °C when internal exhaust gas recirculation is also implemented. These variable valve actuation-based strategies also outperform six-cylinder operation for aftertreatment warm-up at all catalyst bed temperatures. These benefits are primarily realized by reducing the air flow through the engine, directly resulting in higher exhaust temperatures and lower pumping penalties compared to conventional six-cylinder operation. The elevated exhaust temperatures offset exhaust flow reductions, increasing exhaust gas-to-catalyst heat transfer rates, resulting in superior aftertreatment thermal management performance.

Compound Control Strategy Based on Active Disturbance Rejection for Selected Catalytic Reduction systems

Urea-based selected catalytic reduction (SCR) systems are effective ways in diesel engine after-treatment systems to meet increasingly stringent emission regulations. To achieve high NOx reduction efficiency and low NH3 slip, the control of the SCR system becomes more challenging, especially in transient operating conditions with model uncertainties. To effectively address this issue, this paper proposed a compound control strategy with a switching mechanism between an active disturbance rejection (ADR) controller and a zero-input controller. The ADR controller estimates and rejects the total (internal and external) disturbances from the SCR system when the exhaust gas temperature is high and its variation is small. The zero-input controller is used to lower ammonia surface coverage ratio to avoid high ammonia slip when exhaust gas temperature suddenly rises. The proposed control strategy is validated through a high-fidelity GT-Power simulation for a light-duty diesel engine over steady states and federal test procedure (FTP-75) test cycle. Its effectiveness is demonstrated especially in rapidly transient conditions with model uncertainties.

Simulation of oxidation catalyst converter for after-treatment in diesel engines

In the diesel engine after-treatment system of motor vehicles, Diesel Oxidation Catalytic (DOC) converter is used to purify hydrocarbons (HCs) consisting of oil and fuel residue, and Carbon Monoxide (CO) from the exhaust gas. The exhaust gas flowing through DOC converter experiences chemical reactions that oxidize CO and HCs which are formed by incomplete combustion. Reactive properties, geometric features and thermal properties are fundamental design elements of a DOC converter. Flow of the exhaust gas through the converter with these properties can be described using a mathematical model given by Partial Differential Equations (PDEs). In this work, a simulation program for solving these PDEs describing the mathematical model of DOC converter was developed. PDEs were solved by Finite Volume Method (FVM) for volume elements and an implicit method for time steps. Using the solution of PDEs, reduction of CO and HCs at the outlet of the converter was computed. Thus, our model can be used to simulate, or design DOC converters and to predict the reduction of CO and HCs from DOC converters.

Application of Reference Governor Using Soft Constraints and Steepest Descent Method to Diesel Engine Aftertreatment Temperature Control

Application of Reference Governor Using Soft Constraints and Steepest Descent Method to Diesel Engine Aftertreatment Temperature Control

Modeling of Urea-Water Solution Injection Spray in SCR System

To control the emissions from the diesel engines of modern automobiles, it requires the development of adequate and advanced exhaust gas aftertreatment devices. Selective Catalytic Reduction (SCR) is a method that can be used in mobile diesel engine aftertreatment systems to reduce harmful NOx emissions. Due to the toxicity and handling problems of ammonia, currently injection of a liquid Urea-Water Solution (UWS) into the exhaust stream approach is used. The water evaporates and the urea undergoes thermal decomposition producing ammonia that reacts with the NOx in the exhaust gas inside a SCR catalyst to produce nitrogen and water vapor. This work presents the study of UWS injection spray using commercial available CFD code, Fire v8.3. The evaporation of water from a single droplet of UWS is investigated theoretically and droplets are treated with Lagrangian particle tracking. Simulation study at different exhaust gas temperatures and injector locations is carried out and compared with experimental values. Thus, the present study results predict the local distribution and the conversion of the reducing agent.

Control-Oriented Modeling and Observer-Based Estimation of Solid and Gas Temperatures for a Diesel Engine Aftertreatment System

Diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) have become standard components in diesel engine aftertreatment systems to remove carbon monoxide (CO), unburned hydrocarbon (HC), and particulate matter (PM) emissions. Many studies have been focused on improving the performances of DOCs and DPFs, which have been found to be influenced significantly by their respective thermal behaviors. The objective of this research is to develop a control-oriented thermal model for a DOC + DPF aftertreatment system. The control-oriented model is established by considering both thermal inertia of each component and chemical reactions inside it. Engine-out, DOC-out, and DPF-out emissions have been analyzed before simplified empirical models are proposed for the prediction of cared emission species. Experimental validation results show that the control-oriented models are capable of capturing both the gas phase and the solid phase thermal dynamics of a DOC and a DPF. An observer, designed based on the control-oriented solid temperature model and exhaust gas temperature model, can estimate the DOC and DPF gas and solid temperatures accurately in comparison with the measurements. The control-oriented thermal models and observer will be beneficial in the integrated engine and aftertreatment system control.

The effect of a H2/CO mixture at varying ratios on the diesel particulate filter regeneration process: Towards an optimised fuel reformer design – Diesel engine aftertreatment system

The work described in this paper aims to assist in the development of an exhaust gas fuel reformer for the enhancement of diesel particulate filter (DPF) aftertreatment performance. This was achieved by introducing H2 and CO at various mixture ratios at a concentration of 6% (v/v) to a standardised DPF regeneration process in order to identify an optimised mixture ratio. In addition to this, emission measurements were performed pre and post filter to identify the impact of the additional mixtures on various emission components. A mixture ratio of 60% H2 balanced with CO was identified as the optimised mixture ratio. This was due to this configuration demonstrating one of the most proficient regeneration profiles at a relatively low mean filter temperature of approximately 630 °C. Further to this, it was also noted that the addition of H2 or H2 and CO to the regeneration process resulted in an increase in NOx post filter while total hydrocarbons were reduced. Furthermore, the H2/CO mixture addition resulted in an increase in CO2 post filter, the levels of which were proportional to the volume of CO contained within the introduced mixture.

US Patent Reform 2011: A Few Things to Remember

Pharmaceutical Patent AnalystVol. 1, No. 2 Hot TopicUS patent reform 2011: a few things to rememberSmitha B Uthaman, Deborah L Lu & Thomas J KowalskiSmitha B Uthaman* Author for correspondenceVedder Price PC, 1633 Broadway, 47th Floor, New York, NY 10019, USA. Search for more papers by this authorEmail the corresponding author at suthaman@vedderprice.com, Deborah L LuVedder Price PC, 1633 Broadway, 47th Floor, New York, NY 10019, USASearch for more papers by this author & Thomas J KowalskiVedder Price PC, 1633 Broadway, 47th Floor, New York, NY 10019, USASearch for more papers by this authorPublished Online:10 May 2012https://doi.org/10.4155/ppa.12.11AboutSectionsView ArticleView Full TextPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinkedInRedditEmail View articleReferences1 The US Constitution. Article 1 – Section 8 (1787).Google Scholar2 Leahy–Smith America Invents Act. H.R. 1249 (2011).Google Scholar3 Microsoft Corp. v. i4i Ltd. Partnership, 564 US _ (2011).Google Scholar101 NY Times. Senate passes bill to change patent system and pricing by Edward Wyatt. www.nytimes.com/2011/03/09/business/09patent.html (Accessed 18 January 2012)Google ScholarFiguresReferencesRelatedDetailsCited ByBiofuel Impact on Diesel Engine After-Treatment: Deactivation Mechanisms and Soot Reactivity18 December 2017 | Emission Control Science and Technology, Vol. 4, No. 1Vanadia-Based Catalysts for Mobile SCR15 March 2014 Vol. 1, No. 2 Follow us on social media for the latest updates Metrics Downloaded 260 times History Published online 10 May 2012 Published in print May 2012 Information© Future Science LtdFinancial & competing interests disclosureThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.PDF download

Oxygen Concentration Dynamic Model and Observer-Based Estimation Through a Diesel Engine Aftertreatment System

Due to the chemical reactions occurring inside the diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) that are commonly equipped on diesel engines, the exhaust gas oxygen concentrations considerably vary through the aftertreatment systems. Oxygen concentration in exhaust gas is important for the performance of catalysts such as the NOx conversion efficiencies of the selective catalytic reduction systems and lean NOx traps. Moreover, in the presence of a low-pressure loop exhaust gas recirculation, the exhaust gas oxygen concentration after DPF also influences the in-cylinder combustion. From system control, estimation, and analysis viewpoints, it is thus imperative to have a control-oriented model to describe the oxygen concentration dynamics across the DOC and DPF. In this paper, a physics-based, lumped-parameter, control-oriented DOC–DPF oxygen concentration dynamic model was developed with a multi-objective optimization method and validated with the experimental data obtained on a medium-duty diesel engine equipped with a full suite of aftertreatment systems. Experimental results show that the model can well capture the oxygen dynamics across the diesel engine aftertreatment systems. As an application of the experimentally validated model, an observer was designed to estimate the DOC-out and DPF-out oxygen concentrations in real time. Experimental results show that the estimated states from the proposed observer can converge to the measured signals fastly and accurately.

NO and NO2 Concentration Modeling and Observer-Based Estimation Across a Diesel Engine Aftertreatment System

This paper presents an experimentally validated control-oriented model and an observer for diesel oxidation catalyst (DOC)-diesel particulate filter (DPF) system in the context of exhaust gas NO and NO2 concentration estimations. NO and NO2 have different reaction characteristics within DPF and selective catalytic reduction (SCR) systems, two most promising diesel engine aftertreatment systems. Although the majority of diesel engine-out NOx emissions is NO, the commonly used DOC located upstream of a DPF and a SCR can convert a considerable amount of NO to NO2. Knowledge of the NO/NO2 ratio in exhaust gas is thus meaningful for the control and diagnosis of DPF and SCR systems. Existing onboard NOx sensors cannot differentiate NO and NO2, and such a sensory deficiency makes separate considerations of NO and NO2 in SCR control design challenging. To tackle this problem, a control-oriented dynamic model, which can capture the main NO and NO2 dynamics from engine-out, through DOC, and to DPF, was developed. Due to the computational limitation concerns, DOC and DPF are assumed to be standard continuously stirred tank reactors in order to obtain a 0D ordinary differential equation model. Based on the model, an observer, with the measurement from a commercially available NOx sensor, was designed to estimate the NO and NO2 concentrations in the exhaust gas along the aftertreatment systems. The stability of the observer was shown through a Lyapunov analysis assisted by insight into the system characteristics. The control-oriented model and the observer were validated with engine experimental data and the measured NO/NO2 concentrations by a Horiba gas analyzer. Experimental results show that the model can accurately predict the main engine-out/DOC/DPF NO/NO2 dynamics very well in semisteady-state tests. For the proposed observer, the predictions converge to the model values and estimate the NO and NO2 concentrations in the aftertreatment system well.

CO Emission Model for an Integrated Diesel Engine, Emissions, and Exhaust Aftertreatment System Level Model

CO Emission Model for an Integrated Diesel Engine, Emissions, and Exhaust Aftertreatment System Level Model

Investigation of Active Flow Control on Diesel Engine Aftertreatment

Theoretical studies are performed with one-dimensional transient modeling techniques to analyze the thermal behavior of the diesel aftertreatment systems when active flow control schemes are applied. The combined use of activegas flowandactivefueling-controlschemesareidentifiedtobecapableofshiftingtheexhaustgastemperature, flow rate, and oxygen concentration to more favorable windows for the filtration, conversion, and regeneration processes. Several external fuel-supplying techniques are applied and analyzed with various heat distribution patterns and exhaust flow control parameters. The analysis indicates that the active flow control schemes have fundamental advantages in optimizing the converter thermal management that includes supplemental heating, thermal retention, thermal recuperation, and overheating protection. Modeling validation analyses with selected experiments are also reported.

Lean Nox Trap Storage Model for Diesel Engine Aftertreatment Control and Diagnosis

NOx emissions are a great concern to the environment. One major NOx emission source is from off-road and highway vehicles powered with diesel engines. Diesel engines offer significant benefits in fuel economy and low-speed torque performance. However, these benefits come at the expense of increased aftertreatment complexity. A lean NOx trap (LNT) is one effective way to reduce emissions to meet strict EPA regulations. Based on the chemical kinetics analysis of the LNT adsorption mechanism and mass transfer process, a storage model was proposed to estimate the mass of NOx adsorbed inside an LNT during lean periods based on other available signals. The model includes exhaust gas mass flow rate, in-bed temperature, inflow NOx concentrations, and NOx adsorption capacity of the LNT. Model validation shows close agreement between predictions and experimental data. This storage model can be used for LNT regeneration control and fault detection.

04/00406 A new optimizing technique of a diesel engine aftertreatment system using HC DeNO x catalyst : Ueda, M. et al. JSAE Review, 2003, 24, (1), 47–51

04/00406 A new optimizing technique of a diesel engine aftertreatment system using HC DeNO x catalyst : Ueda, M. et al. JSAE Review, 2003, 24, (1), 47–51

A new optimizing technique of a diesel engine aftertreatment system using HC DeNo x catalyst : Ueda, O. et al. JSAE Review, 2003, 24, (1), 47–51

A new optimizing technique of a diesel engine aftertreatment system using HC DeNo x catalyst : Ueda, O. et al. JSAE Review, 2003, 24, (1), 47–51

A new optimizing technique of a diesel engine aftertreatment system using HC DeNo x catalyst

A new method that optimizes a control map of hydrocarbon (HC) addition to diesel exhaust gas for HC type Selective Catalytic Reduction DeNO x catalyst system has been developed. This method comprises a numerical model and a new optimization technique. The numerical model is capable of predicting performance of HC DeNO x with diesel fuel as a supplemental reductant. The control map of HC addition was optimized with the evolutionary programming based on the evolution of living things. As a result, NO x conversion with the optimized control map was found to be greater by 21% than that with the conventional control on Japanese 10–15 mode.

Plasmatron fuel converter-catalyst systems for aftertreatment of diesel vehicle emissions

Improvements in diesel engine aftertreatment technology are needed to meet future environmental quality goals. Systems using recently developed compact plasmatron fuel converters in conjunction with aftertreatment catalysts could provide new opportunities for obtaining significant pollution reductions. Use of compact plasmatron reformers to produce hydrogen-rich gas for the regeneration of NOx absorber/absorbers and particulate traps could provide significant advantages. Catalyst requirements are determined and overall system characteristics are evaluated. The options made possible by use of onboard hydrogen generation for regeneration of catalysts are briefly described. Recent tests of conversion of diesel fuel to hydrogen-rich gas using a low current plasmatron fuel converter with non-equilibrium plasma features are described.