Passive Ammonia SCR System for Lean-burn SIDI Engines

Li, Wei; Perry, Kevin L.; Narayanaswamy, Kushal; Kim, Chang Hwan; Najt, Paul

doi:10.4271/2010-01-0366

Cited by 41 publications

(18 citation statements)

References 6 publications

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“…In contrast, it has been shown that the dispersion of small and nonspherical particles in the aerodynamic lens inlet of the SP-AMS may cause particles to miss the laser vaporizer (Onasch et al, 2012). Also, based on previous studies, it is known that the black carbon particles emitted by engines are typically agglomerates with irregular shapes and diameters of 10-90 nm (Happonen et al, 2010;Lähde et al, 2010;Karjalainen et al, 2014;Liati et al, 2016), which also might have decreased the detection efficiency of the primary black carbon (soot) particles in this study. We also note that the losses for PM in the PAM chamber are dependent on particle size.…”

Section: Refractive Black Carbonmentioning

confidence: 72%

Influence of fuel ethanol content on primary emissions and secondary aerosol formation potential for a modern flex-fuel gasoline vehicle

et al. 2017

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Abstract. The effect of fuel ethanol content (10, 85 and 100 %) on primary emissions and on subsequent secondary aerosol formation was investigated for a Euro 5 flex-fuel gasoline vehicle. Emissions were characterized during a New European Driving Cycle (NEDC) using a comprehensive set-up of high time-resolution instruments. A detailed chemical composition of the exhaust particulate matter (PM) was studied using a soot particle aerosol mass spectrometer (SP-AMS), and secondary aerosol formation was studied using a potential aerosol mass (PAM) chamber. For the primary gaseous compounds, an increase in total hydrocarbon emissions and a decrease in aromatic BTEX (benzene, toluene, ethylbenzene and xylenes) compounds was observed when the amount of ethanol in the fuel increased. In regard to particles, the largest primary particulate matter concentrations and potential for secondary particle formation was measured for the E10 fuel (10 % ethanol). As the ethanol content of the fuel increased, a significant decrease in the average primary particulate matter concentrations over the NEDC was found. The PM emissions were 0.45, 0.25 and 0.15 mg m−3 for E10, E85 and E100, respectively. Similarly, a clear decrease in secondary aerosol formation potential was observed with a larger contribution of ethanol in the fuel. The secondary-to-primary PM ratios were 13.4 and 1.5 for E10 and E85, respectively. For E100, a slight decrease in PM mass was observed after the PAM chamber, indicating that the PM produced by secondary aerosol formation was less than the PM lost through wall losses or the degradation of the primary organic aerosol (POA) in the chamber. For all fuel blends, the formed secondary aerosol consisted mostly of organic compounds. For E10, the contribution of organic compounds containing oxygen increased from 35 %, measured for primary organics, to 62 % after the PAM chamber. For E85, the contribution of organic compounds containing oxygen increased from 42 % (primary) to 57 % (after the PAM chamber), whereas for E100 the amount of oxidized organics remained the same (approximately 62 %) with the PAM chamber when compared to the primary emissions.

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Section: Refractive Black Carbonmentioning

confidence: 72%

Influence of fuel ethanol content on primary emissions and secondary aerosol formation potential for a modern flex-fuel gasoline vehicle

et al. 2017

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“…14 A rate mapping approach that can predict ammonia oxidation reactions has also been presented. 20 However, our interest in this work is to have a global kinetic model for NH 3 formation/oxidation on a Three-Way Catalyst. There are global kinetic models for LNT which include NH 3 formation/oxidation reactions but the reaction parameters are not mentioned 16,21,22 and the actual kinetic parameters are likely to be different between a commercial LNT catalyst and a commercial TWC.…”

Section: ' Modification In Twc Kinetics Modelmentioning

confidence: 99%

“…Additionally, including all the possible reactions for NH 3 formation/consumption will increase the number of parameters to be estimated and since these parameters are being estimated for the first time, it is better to include the "most dominant reactions" that can capture the observed trends and then expand the reaction mechanism further]. The kinetic parameters for NH 3 formation and oxidation reactions are estimated through optimization techniques by minimizing the error between predicted and measured post-front brick NH 3 .The details of the formulation of objective functions, data points included for the parameter estimation process and the optimization strategy are given in the Appendix.…”

Section: ' Modification In Twc Kinetics Modelmentioning

confidence: 99%

“…Generating ammonia over the TWC consumes fuel (because of the rich operation) and affects the overall efficiency for other regulated emissions such as CO and HC. The NH 3 formed during the rich operation in TWC has to be carefully tuned so that there is enough NH 3 for NO x reduction in SCR during the lean operation and at the same time there is no NH 3 slip in the tailpipe. Therefore, it requires a rational design of the close-coupled TWC catalyst.…”

Section: ' Introductionmentioning

confidence: 99%

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Global Kinetics for Ammonia Formation and Oxidation Reactions in a Commercial Three-Way Catalyst

Ramanathan

Sharma

Kim

2012

Ind. Eng. Chem. Res.

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Lean-burn spark ignition direct injection (SIDI) engines offer significant potential for improving engine efficiency and reducing greenhouse gas emissions. However, NO x reduction in lean-burn SIDI engines presents significant challenges. One of the exhaust architectures that is currently being investigated and developed for lean-gasoline applications is the passive ammonia-SCR (three-way catalystÀselective catalyst reduction) system. It involves the use of the closed-coupled three-way catalyst (TWC) to generate NH 3 (during fuel-rich conditions) for use by the downstream NH 3 ÀSCR for NO x reduction. However, the NH 3 formed in TWC has to be controlled so that there is enough NH 3 for NO x reduction in SCR, and at the same time, there is no NH 3 slip in the tailpipe. A mathematical model for the TWC, which can predict the net NH 3 coming out of the TWC, will be very useful for control algorithm development and for understanding and optimizing the exhaust architecture. The focus of this work is on the kinetic modeling of NH 3 formation and oxidation reactions in a three way catalyst (TWC). Controlled steady-state and transient test cell experiments were performed at different air-to-fuel ratios and different engine conditions. This data was used to expand the existing TWC global reaction to include three additional global reactions that can account for NH 3 formation and oxidation. A part of the experimental data was used to estimate the kinetic parameters of the above reactions (using a one-dimensional mathematical model for the TWC) through optimization techniques. The estimated kinetic parameters are able to predict the rest of the steady-state and controlled transient experimental data reasonably well. ' INTRODUCTIONLean-burn spark ignition direct injection (SIDI) engines offer significant benefit in improving fuel economy and reducing greenhouse gas emissions. 1,2 However, NO x reduction in leanburn SIDI engines presents significant challenges. Active NO x abatement systems include selective catalytic reduction for NO x by unburnt hydrocarbons (HC) present in engine exhaust (HC-SCR) or externally injected ammonia (urea) in the engine exhaust (NH 3 ÀSCR), and storing of NO x in the catalyst during lean engine operation and reducing it during short duration rich excursions (LNT, that is, lean NO x trap). Urea-based SCR systems require a secondary fluid tank with an injection system resulting in added cost and complexity. LNT catalysts suffer from higher platinum group metal (PGM) costs and also from sulfur poisoning. At General Motors (GM), one of the exhaust architectures that are currently being investigated and developed for lean-gasoline applications is the urea-less passive ammonia-SCR (three-way catalystÀselective catalytic reduction catalyst) system. 3,4 It involves the use of the closed-coupled three-way catalyst (TWC), which apart from oxidizing the carbon monoxides, unburnt and partially burnt hydrocarbons, is used to generate NH 3 periodically (during fuel-rich conditions) 5 for use by the downstrea...

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“…A promising low-cost alternative for lean NO x aftertreatment in SIDI engines is the passive ammonia (NH 3 )SCR system (PASS) [9,10]. A schematic of the passive NH 3 SCR system is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Modelling of passive ammonia selective catalytic reduction system for lean-burn spark ignition direct injection engines

Narayanaswamy

Najt

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part D:

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Lean-burn spark ignition direct injection (SIDI) engines offer potential fuel economy savings; however, the lack of simple and cost-effective lean nitrogen oxide (NO x ) aftertreatment systems hinder their broad application. Lean NO x traps (LNT) and urea selective catalytic reduction (SCR) catalysts have been widely investigated as possible lean gasoline aftertreatment technologies, but with limited acceptance.Passive ammonia SCR operation is a promising low-cost alternative for lean NO x aftertreatment with SIDI engines. The aftertreatment system includes close-coupled three-way catalyst (TWC) converters and one or more under-floor SCR catalysts. Ammonia (NH 3 ) is formed on the TWC with short pulses of rich engine operations and the generated NH 3 is then stored on the under-floor SCR catalysts. During subsequent lean operations, the NO x that breaks through the TWC converters is reduced to nitrogen by NH 3 stored on the SCR catalysts.This paper provides an overview of system level analysis as a complement to experimental testing in the development of a passive NH 3 SCR-based aftertreatment system. Various aftertreatment architectures (SCR type, the order, and location of the catalysts) were efficiently evaluated and screened, to achieve the best trade-off between engine back-pressure, catalyst warm-up, emission constraints, and acceptable thermal ageing under high-speed/load conditions.

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Passive Ammonia SCR System for Lean-burn SIDI Engines

Cited by 41 publications

References 6 publications

Influence of fuel ethanol content on primary emissions and secondary aerosol formation potential for a modern flex-fuel gasoline vehicle

Influence of fuel ethanol content on primary emissions and secondary aerosol formation potential for a modern flex-fuel gasoline vehicle

Global Kinetics for Ammonia Formation and Oxidation Reactions in a Commercial Three-Way Catalyst

Modelling of passive ammonia selective catalytic reduction system for lean-burn spark ignition direct injection engines

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