Title: Passive SCR Performance Under Pseudo-Transient Cycle: Challenges and Opportunities for Meeting Tier 3 Emissions

Abstract

We report that the passive ammonia (NH₃) selective catalytic reduction (SCR) system is a potential approach for controlling nitrogen oxide (NOx) emissions from lean-burn gasoline engines based on utilizing NH₃ generated by a three-way catalyst (TWC) during brief periods of fuel-rich engine operation. NH₃ generated by the TWC is stored and available to reduce NOx on a downstream SCR catalyst during subsequent periods of lean engine operation. Control of the overall passive SCR process can be more challenging than current urea-based approach because it depends explicitly on fuel-rich engine operation, which must be implemented in the context of transient engine operation. Under transient engine operation, significant variation in SCR temperatures is also to be expected. With NH₃ storage capacity highly dependent on exhaust temperatures, proper system architecture and engine operating strategy are needed for effective NH₃ utilization over the SCR catalyst. In this study, the performance of a passive SCR system was evaluated on a 2.0-l BMW lean-burn gasoline direct injection engine under 6-mode pseudo-transient cycle. The aim of this work is to understand how various engine operating strategies change the dynamics of NH₃ generation and utilization, and NOx reduction in the passive SCR system. A 5.9% fuel economy improvementmore » relative to stoichiometric-only operation with 0.018 g/mi of NOx + NMHC emissions were demonstrated over 6-mode pseudo-transient cycle; however, CO emissions were twice the emission standard. In conclusion, the results of this work reveal challenges and opportunities for meeting Tier 3 emissions and improving fuel savings benefits.« less

Authors:

Prikhodko, Vitaly Y.  ^[1];

• Search DOE PAGES for author "Prikhodko, Vitaly Y."
• Search DOE PAGES for ORCID "0000-0002-4468-5836"

Pihl, Josh A.  ^[1];

• Search DOE PAGES for author "Pihl, Josh A."
• Search DOE PAGES for ORCID "0000-0002-9798-4012"

Toops, Todd J.  ^[1];

• Search DOE PAGES for author "Toops, Todd J."
• Search DOE PAGES for ORCID "0000-0002-3163-8539"

Parks, II, James E.  ^[1]

• Search DOE PAGES for author "Parks, II, James E."
• Search DOE PAGES for ORCID "0000-0003-3160-7385"

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Wed Jul 17 00:00:00 EDT 2019

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)

OSTI Identifier:

1550752

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Emission Control Science & Technology

Additional Journal Information:

Journal Volume: 5; Journal Issue: 3; Journal ID: ISSN 2199-3629

Publisher:

Springer

Country of Publication:

United States

Language:

English

Subject:

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 54 ENVIRONMENTAL SCIENCES; Passive SCR; TWC; Lean NOx; NH3 formation; Lean gasoline