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Optimization of Combustion Mode Duration for Lean Gasoline Engine with NOxStorage-Capable Passive Selective Catalytic Reduction System | IEEE Conference Publication | IEEE Xplore

Optimization of Combustion Mode Duration for Lean Gasoline Engine with NOxStorage-Capable Passive Selective Catalytic Reduction System


Abstract:

Lean-burn gasoline engines have demonstrated promising potentials to achieve higher fuel efficiency than stoichiometric gasoline engines. However, severe concerns arise i...Show More

Abstract:

Lean-burn gasoline engines have demonstrated promising potentials to achieve higher fuel efficiency than stoichiometric gasoline engines. However, severe concerns arise in lean NOx emission control. Three-way catalysts (TWCs), which are broadly applied in stoichiometric gasoline engines, fail to achieve high NOx conversion efficiency in the presence of excessive oxygen. Emerging passive selective catalytic reduction (SCR) systems with NOx storage capability on TWC, offer great potential in NOx emission reduction for lean-burn gasoline engines at low fuel penalty due to on-board ammonia generation in periodic rich operation. The purpose of this paper is to derive local and global optimization algorithms for optimizing lean and rich operation times in each lean-rich period for lean-burn gasoline engines by considering not only fuel penalty associated with NH3 production but also lean/rich switching frequency. Optimization results demonstrate that both local and optimal optimization strategies result in comparable fuel penalties at the same level of mode-switching frequency. However, the genetic algorithm-based global optimization method requires much higher computational load than the local optimization method and thus is less preferred for real-time applications.
Date of Conference: 10-12 July 2019
Date Added to IEEE Xplore: 29 August 2019
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ISSN Information:

Conference Location: Philadelphia, PA, USA

I. Introduction

With fuel consumption and emission standards becoming more tightly regulated, lean-burn gasoline direct injection (GDI) engines are capturing the interests from the automotive industry due to 10-15% fuel saving benefits over stoichiometric gasoline engines [1]. However, cost-effective and efficient removal of NOx in lean exhaust condition remains a significant challenge to overcome. Low-cost three-way catalysts (TWCs), which are capable of reducing hydrocarbon (HC), CO and NOx emission from stoichiometric gasoline engines at high efficiencies, demonstrated limited deNOx capabilities in the presence of excess oxygen. The Diesel engine industry has adopted lean NOx traps (LNTs) and selective catalytic reduction (SCR) systems for NOx reduction. However, LNTs contain precious group metals (PGMs), leading to a high cost. In addition, LNT are subject to sulfur poisoning, which leads to reduced emission control performance. Urea-based SCR systems have become standard for medium-to-heavy duty applications but are less accepted for passenger car applications due to the requirements of the consumable urea solution and complex dosing systems.

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