Modeling of Close-Coupled SCR Concepts to Meet Future Cold Start Requirements for Heavy-Duty Engines

Harris, Tony; Pherson, Kristoffer Mc; Rezaei, Reza; Kovacs, David; Rauch, Hendrik; Huang, Yinyan

doi:10.4271/2019-01-0984

Cited by 17 publications

(6 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3,14 Certain modelling studies have attempted to examine the low exhaust temperatures during the FTP cycle in detail and suggested some possible solutions. [15][16][17] Retarding the diesel injection timing, throttling the intake and exhaust of the engine, elevated idle, late intake valve closing, and early exhaust valve opening may reduce NOx emissions and increase exhaust temperature simultaneously with varying impact on the fuel consumption. 15,17 A close-coupled or light-off SCR (ccSCR or LO-SCR) unit placed preferably immediately downstream of the turbocharger can heat up faster and be effective in minimizing NOx slip when the main SCR unit further downstream is not functional.…”

Section: Introductionmentioning

confidence: 99%

“…15,17 A close-coupled or light-off SCR (ccSCR or LO-SCR) unit placed preferably immediately downstream of the turbocharger can heat up faster and be effective in minimizing NOx slip when the main SCR unit further downstream is not functional. 16 Extensive evaluations by South-west Research Institute (SwRI) have led to the successful demonstration of 0.023 g/bhp-hr NOx emissions over the composite FTP cycle using aged catalysts with no change in the fuel consumption. [3][4][5][6][7]18 The SwRI EAT system also consists of a LO-SCR followed by a catalyzed soot filter (later updated with conventional diesel oxidation catalyst (DOC) and diesel particulate filter (DPF)) and downstream SCR units.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A study on effect of engine operating parameters on NOx emissions and exhaust temperatures of a heavy-duty diesel engine during idling

Dev

Lafrance

Liko

et al. 2022

International Journal of Engine Research

View full text Add to dashboard Cite

Though NOx emissions from on-road heavy duty vehicles (HDVs) have reduced drastically over the past three decades, upcoming North American regulations may call for further reductions. Lowering NOx emissions below current levels is challenging, especially at lower operating loads such as idling and/or colder climates when the exhaust gas temperature is insufficient for high NOx conversion in the HDV’s exhaust after treatment (EAT) system. This paper investigates the impact of various engine operating parameters on the three-way trade-off between NOx emissions, exhaust temperature, and fuel consumption using a single-cylinder, heavy-duty diesel engine outfitted with a conventional EAT system and diesel exhaust fluid (DEF) injection. The engine parameters investigated include exhaust gas recirculation (EGR) ratio, intake pressure, intake temperature, injection pressure, multiple injections, and engine fluid temperatures. In order to simulate cold climate operation, the baseline intake air, coolant, and lubricating oil temperatures are maintained at 10°C, 40°C, and 50°C, respectively. Results show that using a moderate level of EGR has the dual benefit of reducing the engine-out NOx and increasing the intake charge temperature. Increasing the intake or injection pressure does not result in significant benefit in improving the three-way trade-off. However, using double injection with the second injection at the start of the expansion stroke can help reduce NOx emissions and increase exhaust temperature with marginal impact on fuel efficiency. Based on the parametric study, three particular engine operating conditions are chosen for further investigation with the EAT online. At an identical DEF dosing rate, the rates of NOx reduction in the SCR are similar for the three conditions (∼96%), and the lowest tail-pipe NOx observed for this study is 0.032 g/kWh.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A study on effect of engine operating parameters on NOx emissions and exhaust temperatures of a heavy-duty diesel engine during idling

Dev

Lafrance

Liko

et al. 2022

International Journal of Engine Research

View full text Add to dashboard Cite

show abstract

“…For example SCR requires a 1:1 NO:NO2 ratio for optimum efficiency [6]. A Diesel Oxidation Catalyst (DOC) is often used upstream of an SCR to promote this 1:1 ratio, however as fast warm-up catalyst technologies (such as close-coupled SCR where an SCR is upstream of a DOC [7]) become necessary for increasingly stringent Real Driving Emissions (RDE) legislation [1], engine-out control of this ratio increases in importance.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Cycle-to-Cycle Hydrocarbon Emissions on Cyclic NO:NO2 Ratio From a HSDI Diesel Engine

Leach

Shankar

Davy

et al. 2021

Journal of Engineering for Gas Turbines and Power

View full text Add to dashboard Cite

Knowledge of the NO:NO2 ratio emitted from a diesel engine is particularly important for ensuring the highest performance of SCR NOx aftertreatment systems. As real driving emissions from vehicles increase in importance, the need to understand the NO:NO2 ratio emitted from a diesel engine during transient operation similarly increases. In this study, crank-angle resolved NO and NO2 measurements using fast response CLD (for NO) and a new fast LIF instrument (for NO2) have been taken from a single cylinder diesel engine at three different speed and load points including a point with and without EGR. In addition, crank-angle resolved unburned hydrocarbon (UHC) measurements have been taken simultaneously using a fast FID. A variation of the NO:NO2 ratio through the engine's exhaust stroke is also observed indicative of in-cylinder stratification of NO and NO2. A new link between the NO:NO2 ratio and the UHC emissions from an individual engine cycle is observed - the results show that where there are higher levels of UHC emissions in the first part of the exhaust stroke (blowdown), the proportion of NO2 emitted from that cycle is increased. This effect is observed and analysed across all test points and with and without EGR. The performance of the new fast LIF analyser has also been evaluated, in comparison with the previous state-of-the-art and standard "slow" emissions measurement apparatus showing a reduction in the noise of the measurement by an order of magnitude.

show abstract

“…Considering the temperature impact on SCR performance, thermal management was applied in the aftertreatment system [6]. A modeling method was applied for analyzing NOx conversion efficiency impact aspects by considering the NH 3 storage capability in a DOC+DPF+SCR aftertreatment system [7]. Computational fluid dynamics (CFD) analysis was used to optimize aftertreatment packaging design for better SCR performance and higher NOx conversion efficiency [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Experimental Research on Aftertreatment SCR Sizing Strategy for a Nonroad Mid–Range Diesel Engine

2020

View full text Add to dashboard Cite

Urea-Selective Catalytic Reduction (SCR) is widely used to reduce nitrogen oxide (NOx) emissions. This paper presents a comprehensive experimental research work on aftertreatment emissions of NOx and ammonia (NH3) slip for three aftertreatment concepts by introducing the SCR sizing strategy on a 6-cylinder mid-range non-exhaust gas recirculation (EGR) diesel engine to meet China non-road Stage IV regulation limits. It can be observed that the three concepts could meet the regulation limits for NOx emissions and NH3 slip by selecting the appropriate length. There is little effect on emission results during a non-road transient cycle (NRTC) when the aftertreatment inlet/outlet with insulation and without insulation and the emission results on both strategies could meet non-road China Stage IV regulation limits. It is recommended to select Concept 2 which could meet regulation requirements considering multiple factors in the SCR sizing strategy. Substrate impact and NH3/NOx molar ratio (ANR) impact are investigated based on Concept 2. The results show that by applying the SCR substrate aftertreatment with a cell density of 600 cpsi, NOx conversion capability is stronger than that with cell density 400 cpsi for the same SCR size. Current dosing strategy is capable and recommended ANR is 0.9–1.1 if considering dosing strategy optimization. The methodology in this study provides an effective guidance and reference for future aftertreatment SCR sizing strategies in real applications.

show abstract

Modeling of Close-Coupled SCR Concepts to Meet Future Cold Start Requirements for Heavy-Duty Engines

Cited by 17 publications

References 7 publications

A study on effect of engine operating parameters on NOx emissions and exhaust temperatures of a heavy-duty diesel engine during idling

A study on effect of engine operating parameters on NOx emissions and exhaust temperatures of a heavy-duty diesel engine during idling

The Influence of Cycle-to-Cycle Hydrocarbon Emissions on Cyclic NO:NO2 Ratio From a HSDI Diesel Engine

Experimental Research on Aftertreatment SCR Sizing Strategy for a Nonroad Mid–Range Diesel Engine

Contact Info

Product

Resources

About