Modeling of a Partial-Flow, Diesel, Lean NOx Trap Systems

2005 ◽  
Author(s):  
Shawn Midlam-Mohler ◽  
Yann Guezennec
Keyword(s):  
Diesel Fuel ◽  
Control Strategies ◽  
Nox Reduction ◽  
Lean Nox Trap ◽  
Component Level ◽  
Lean Nox ◽  
Catalyst Temperature ◽  
The Rich ◽  
And Control ◽  
Regeneration Systems

Lean NOx Traps (LNTs) have shown promise for Diesel applications; however, production implementation in vehicles poses a number of challenges. Much of the literature reports on LNT systems in which the catalyst always receives the full flow of exhaust from the engine, referred here as full-flow regeneration systems. Another implementation of the LNT is one in which the exhaust can be partially or fully diverted from the catalyst to allow local introduction of the necessary reductants for regeneration. The physical aspects of one such system, as well as a control-oriented model are presented with experimental validation. In the system described here, the exhaust flow is diverted around the catalyst during regenerations. In the low exhaust flow through the catalyst, reductant is added (Diesel fuel typically) which provides the rich conditions for regenerating the trap. This allows the engine to continue to run in normal lean mode, which overcomes one of the major challenges for full-flow regeneration systems. Successful regeneration with liquid Diesel fuel is strongly dependent on catalyst temperature, which is addressed by proper thermal management of the system through the addition of fuel prior to regeneration. In this paper, both component level and vehicle level simulations are presented in terms of fuel economy versus NOx reduction. Several different system configurations and control strategies are compared.

Effect of Butanol on the Performance of DeNOx Aftertreatment Systems of a Diesel Vehicle Under WLTC Driving Conditions

2021 ◽  
Author(s):  
Alejandro Calle-Asensio ◽  
Juan José Hernández ◽  
José Rodríguez-Fernández ◽  
Víctor Domínguez-Pérez
Keyword(s):  
Catalytic Reduction ◽  
Nox Reduction ◽  
Climatic Conditions ◽  
Transport Sector ◽  
Lean Nox Trap ◽  
Diesel Vehicles ◽  
Medium Speed ◽  
Emission Regulations ◽  
Lean Nox ◽  
Light Duty Vehicles

Abstract Advanced biofuels and electrofuels, among which are medium-long chain alcohols, have gained importance in the transport sector with the enforcement of the EU Renewable Energy Directive (2018/2001). In parallel, last European emission regulations have become much more restrictive regarding NOx, so vehicle manufacturers have been forced to incorporate lean NOx trap (LNT) and/or selective catalytic reduction (SCR). Thus, the combination of modern DeNOx devices and the upcoming higher contribution of sustainable biofuels is a new challenge. In this work, two Euro 6 diesel vehicles, one equipped with LNT and the other with ammonia-SCR, have been tested following the Worldwide harmonized Light-duty vehicles Test Cycle (WLTC) at warm (24°C) and cold (−7°C) conditions using conventional diesel fuel and a diesel-butanol (90/10% vol.) blend. While the effect of butanol on the LNT efficiency was not significant, its influence on the SCR performance was notable during the low and medium-speed phases of the driving cycle, mainly under warm climatic conditions. Despite of the lower NOx concentration at the catalyst inlet, the worst efficiency of the SCR with butanol could be attributed to hydrocarbons deposition on the catalyst surface, which inhibits the NOx reduction reactions with ammonia. Moreover, the LNT was not sensitive to the ambient temperature while the SCR performance greatly depended on this parameter.

Monitoring, Diagnostics, and Prognostics for Robot Tool Center Accuracy Degradation

2018 ◽  
Author(s):  
Guixiu Qiao ◽  
Brian A. Weiss
Keyword(s):  
Health Management ◽  
Control Strategies ◽  
Test Methods ◽  
Component Level ◽  
Data Set ◽  
Root Cause ◽  
Robot Systems ◽  
Robot Performance ◽  
And Control ◽  
Constituent Elements

Over time, robots degrade because of age and wear, leading to decreased reliability and increasing potential for faults and failures; this negatively impacts robot availability. Economic factors motivate facilities and factories to improve maintenance operations to monitor robot degradation and detect faults and failures, especially to eliminate unexpected shutdowns. Since robot systems are complex, with sub-systems and components, it is challenging to determine these constituent elements’ specific influence on the overall system performance. The development of monitoring, diagnostic, and prognostic technologies (collectively known as Prognostics and Health Management (PHM)), can aid manufacturers in maintaining the performance of robot systems by providing intelligence to enhance maintenance and control strategies. This paper presents the strategy of integrating top level and component level PHM to detect robot performance degradation (including robot tool center accuracy degradation), supported by the development of a four-layer sensing and analysis structure. The top level PHM can quickly detect robot tool center accuracy degradation through advanced sensing and test methods developed at the National Institute of Standards and Technology (NIST). The component level PHM supports deep data analysis for root cause diagnostics and prognostics. A reference data set is collected and analyzed using the integration of top level PHM and component level PHM to understand the influence of temperature, speed, and payload on robot’s accuracy degradation.

A Temperature-Based Analysis Technique and Distributed Model Lean NOx Trap Catalyst

2006 ◽  
Author(s):  
Shawn Midlam-Mohler ◽  
Yann Guezennec
Keyword(s):  
Chemical Reactions ◽  
Measurement Technique ◽  
Spatial Information ◽  
Sulfur Poisoning ◽  
Distributed Model ◽  
Practical Reasons ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Lean Nox ◽  
The Rich

The management of an automotive Lean NOx Trap (LNT) catalyst requires periodic, brief periods of net rich exhaust to regenerate the catalyst by reducing the stored NOx. During the regeneration event, the fuel rich gas first affects the front of the catalyst then, as reductants are available, reach the downstream sections of the catalyst. In a typical engine test cell, it is not feasible to witness these distributed effects by simultaneously measuring multiple points in a catalyst bed due for a number of practical reasons. This is inconvenient because it is often desired to have a continuous or distributed lump model of the catalyst, which is difficult to calibrate without spatially and temporally resolved measurements. A novel measurement technique is presented which uses internal catalyst temperature measurements to detect the gross chemical reactions occurring in the catalyst during the rich reduction phase. The magnitude of the temperature change is shown to correlate with the mass of NOx and O2 reduced from the catalyst substrate. This information is available at each temperature measurement location, allowing spatial information to be collected non-intrusively. Furthermore, the technique contains temporal information regarding the key reactions. The type of information made available, as well as the convenience of the measurement system, makes the technique useful for a number of applications. The basis of the measurement technique is first presented from a theoretical basis, relating the temperature rise of the substrate to the various gross chemical reactions. Experimental validation of the method is then provided, illustrating the good correlation between the mass of stored NOx and O2 estimated by the method and the mass of stored NOx calculated from traditional gas analyzer measurements during the NOx storage phase. After demonstrating the applicability of the method, several applications are suggested including use of the technique for LNT modeling, LNT regeneration control, and sulfur poisoning detection.

Long breathing lean NOx trap regeneration with supplemental n-butanol

2018 ◽  
Vol 233 (3) ◽  
pp. 661-670 ◽  
Author(s):  
Christopher Aversa ◽  
Shui Yu ◽  
Marko Jeftić ◽  
Geraint Bryden ◽  
Ming Zheng
Keyword(s):  
Particulate Matter ◽  
Diesel Fuel ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Storage Efficiency ◽  
Combustion Modes ◽  
Particulate Matter Emissions ◽  
Lean Nox ◽  
Low Nitrogen ◽  
Penalty Analysis

This paper evaluates a long breathing strategy of lean NO x trap for achieving ultra-low nitrogen oxide (NO x) emissions, with an aim to reduce the associated fuel penalty. The fuel impacts on the long breathing strategy of lean NO x trap operation are examined on a heated flow bench with diesel and n-butanol as the reductants. Engine tests are performed to identify suitable working regions for the lean NO x trap strategies. For a very low engine-out NO x emission level of ~30 ppm, the long breathing adsorption of the lean NO x trap shows a significant improvement in NO x storage efficiency compared to a conventional lean NO x trap operational strategy for a moderate level of NO x emissions. The use of n-butanol fuel in diesel engines produces much lower NO x and particulate matter emissions, which is deemed advantageous for operating the long breathing lean NO x trap strategy. As a reductant for lean NO x trap regeneration, n-butanol is found to be more effective in terms of regeneration effectiveness, NO x conversion efficiency, and potential hydrogen (H2) yield compared to using diesel fuel in the after-treatment. A fuel penalty analysis is conducted for the selected cases with combinations of different combustion modes and lean NO x trap strategies. Given a low level of NO x emissions from n-butanol combustion, the long breathing lean NO x trap strategy can potentially achieve ultra-low NO x emissions with a minimum fuel penalty.

Natural Gas Partial Oxidation and Reforming for Lean NOx Trap Catalysis Regeneration

2005 ◽  
Author(s):  
James E. Parks ◽  
Jim Tassitano
Keyword(s):  
Natural Gas ◽  
Nox Reduction ◽  
Department Of Energy ◽  
Regeneration Process ◽  
Cyclic Process ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Lean Combustion ◽  
Lean Nox ◽  
Environmental Goals

Program goals for the Advanced Reciprocating Engine Systems (ARES) program of the Department of Energy include efficiency and environmental goals. Lean-burn natural gas engines offer higher efficiency than engines that operate with Stoichiometric air-to-fuel mixtures; however, the excess oxygen in the exhaust of lean engines makes NOx reduction with catalytic aftertreatment difficult. Thus, advancing efficiency via lean combustion results in challenges to meet environmental goals. The lean NOx trap catalyst technology is capable of reducing NOx in lean exhaust and, thereby, enables the potential for lean combustion to meet both efficiency and environmental goals. During lean NOx trap catalysis, NOx in oxygen-rich exhaust is trapped on the catalyst by alkali or alkaline earth-based sorbate materials; then, upon exposure to oxygen-depleted exhaust, the NOx is released and reduced to nitrogen in a process called regeneration. The regeneration process renews the catalyst for more NOx trapping; the cyclic process repeats at periods on the order of a minute. Oxygen depletion during regeneration is accomplished by temporarily operating the catalyst at rich air-to-fuel ratios; traditionally, a variety of methods have been utilized to achieve rich conditions for the catalyst. In this presentation, research of a lean NOx trap on a lean natural gas engine will be presented. Natural gas from the engine supply was used to provide the reductant for the lean NOx trap regeneration process. The natural gas is injected into the exhaust system where oxidation and reforming catalysts partially oxidize and/or reform the natural gas into reductants suitable for lean NOx trap regeneration. Studies of the natural gas oxidation and reforming processes and their relation to NOx reduction performance will be presented.

The Effect of Sulfur on Methane Partial Oxidation and Reforming Processes for Lean NOx Trap Catalysis

2006 ◽  
Author(s):  
James E. Parks ◽  
Senthil Ponnusamy
Keyword(s):  
Partial Oxidation ◽  
Exhaust System ◽  
Catalytic Efficiency ◽  
Methane Partial Oxidation ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Oxidation Of Methane ◽  
Lean Nox ◽  
The Rich ◽  
Catalyst Poisons

Lean NOx trap catalysts have demonstrated the ability to reduce NOx emissions from lean natural gas reciprocating engines by >90%. The technology operates in a cyclic fashion where NOx is trapped on the catalyst during lean operation and released and reduced to N2 under rich exhaust conditions; the rich cleansing operation of the cycle is referred to as “regeneration” since the catalyst is reactivated for more NOx trapping after NOx purge. Creating the rich exhaust conditions for regeneration can be accomplished by catalytic partial oxidation of methane in the exhaust system. Furthermore, catalytic reforming of partial oxidation exhaust can enable increased quantities of H2 which is an excellent reductant for lean NOx trap regeneration. It is critical to maintain clean and efficient partial oxidation and reforming processes to keep the lean NOx trap functioning properly and to reduce extra fuel consumption from the regeneration process. Although most exhaust constituents do not impede partial oxidation and reforming, some exhaust constituents may negatively affect the catalysts and result in loss of catalytic efficiency. Of particular concern are common catalyst poisons sulfur, zinc, and phosphorous. These poisons form in the exhaust through combustion of fuel and oil, and although they are present at low concentrations, they can accumulate to significant levels over the life of an engine system. In the work presented here, the effects of sulfur on the partial oxidation and reforming catalytic processes were studied to determine any durability limitations on the production of reductants for lean NOx trap catalyst regeneration.

Impact of Rh Oxidation State on NOx Reduction Performance of Multi-Component Lean NOx Trap (LNT) Catalyst

2016 ◽  
Vol 9 (3) ◽  
pp. 1615-1622 ◽  
Author(s):  
Junhui Li ◽  
Neal Currier ◽  
Aleksey Yezerets ◽  
Hai-Ying Chen ◽  
Howard Hess ◽  
...  
Keyword(s):  
Oxidation State ◽  
Nox Reduction ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Lean Nox

scholarly journals Optimization of the Washcoat Slurry for Hydrotalcite-Based LNT Catalyst

Catalysts ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 696
Author(s):  
Yue Zhu ◽  
Gang Lv ◽  
Chonglin Song ◽  
Bo Li ◽  
Yantao Zhu ◽  
...  
Keyword(s):  
Nox Reduction ◽  
Solid Content ◽  
Nox Storage ◽  
Lean Nox Trap ◽  
X Ray Diffraction ◽  
Storage Test ◽  
Lean Nox ◽  
Temperature Programmed ◽  
Al2o3 Catalyst ◽  
Slurry Viscosity

This work aimed to optimize the washcoat slurry for hydrotalcite-based lean NOx trap (LNT) catalyst. The effects of the slurry properties including pH, solid content, binder and additive on the hydrotalcite-based slurry viscosity were investigated. The particle size distribution of the optimal hydrotalcite-based slurry was measured. A cordierite material was used to coat the optimal slurry, and the washcoat was characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption. The optimal slurry containing Pt and Ba was coated on the cordierite for the preparation of hydrotalcite-based LNT catalyst, and the performances of this catalyst were evaluated by NOx storage test, temperature programmed desorption and NOx reduction. For comparison, the performance of the commercial LNT catalyst with Pt/BaO/Al2O3 was analyzed. After coating, the hydrotalcite-based washcoat was closely contacted with the support, being the main phase MgO and presenting a specific surface area of 86.3 m2/g. The hydrotalcite-based LNT catalyst had better NOx storage and desorption ability, selectivity to N2 and LNT efficiency than the Pt/BaO/Al2O3 catalyst.

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