A novel NH 3 slip control for diesel engine selective catalytic reduction aftertreatment system

This work presents an optimized ammonia injection strategy for the Worldwide Harmonized Light Vehicles Test Cycle and its potential benefits in terms of NO x emissions and ammonia consumption in selective catalytic reduction. An optimization tool based on optimal control was used to improve the ammonia injection in the selective catalytic reduction with different NO x emission limits. This optimal control can be used in two ways: one to minimize NO x emission and another to reduce the ammonia consumption in the selective catalytic reduction. The optimized strategy and the standard ammonia injection strategy were tested and compared on a fully instrumented engine test bench when applied in a Worldwide Harmonized Light Vehicles Test Cycle. The results showed a considerable improvement in the use of the optimization tool. When compared to the standard calibration, the new injection strategy for the same amount of ammonia injection reduced NO x emissions by 13.7%, and for the same NO x concentration emissions 33.5% of ammonia consumption was saved.

Section: Introductionmentioning

confidence: 99%

Ammonia injection optimization for selective catalytic reduction aftertreatment systems

Plá

Bares

Sanchis

et al. 2020

“…where F in and F out are the molar flow rates of the species in and out of the reactor, respectively, V is the reactor volume, and v i and r i are the stoichiometric coefficient and reaction rate of species i , respectively. Since reaction rates are functions of the monolith temperature T mon , whereas only the upstream exhaust temperature T exh , in is measured, as in Hu et al 2 and Yuan et al 3 a simple first order thermal model is utilised, which is…”

Section: Control Oriented Scr Modellingmentioning

confidence: 99%

“…The most promising aftertreatment technologies for removal of NO x in heavy duty applications is selective catalytic reduction (SCR) and Lean NOx Trap (LNT). 2–4 In this article, we focus on the SCR technology. This chemical system operates by injection of a urea solution before a catalyst, which is hydrolysed into gaseous ammonia.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear model predictive control applied to multivariable thermal and chemical control of selective catalytic reduction aftertreatment

Sowman¹,

Laila

Fussey

et al. 2019

Manufacturers of diesel engines are under increasing pressure to meet progressively stricter NO x emission limits. A key NO x abatement technology is selective catalytic reduction in which ammonia, aided by a catalyst, reacts with NO x in the exhaust stream to produce nitrogen and water. The conversion efficiency is temperature dependent: at low temperature, reaction rates are temperature limited, resulting in suboptimal NO x removal, whereas at high temperatures, they are mass transfer limited. Maintaining sufficiently high temperature to allow maximal conversion is a challenge, particularly after cold start, as well as during conditions in which exhaust heat is insufficient, such as periods of low load or idling. In this work, a nonlinear model predictive controller simultaneously manages urea injection and power to an electric catalyst heater, in the presence of constraints.

“…7 SCR catalyst reduces N O x emissions through the injection of ammonia ( N H 3 ) as a reductant agent, with the objective of transforming N O x emissions into diatomic nitrogen ( N 2 ) and water ( H 2 O ). 8 EURO VI for heavy duty engines limits N H 3 emissions to 10 ppm 9 and it is expected that future regulations will extend N H 3 limits to light duty vehicles, considering that the SCR is a complex dynamic system that interacts with other systems and phenomena in the engine, it is necessary to control it accurately. 10 In particular, ammonia injection for the SCR operation is controlled with the help of a N O x sensor feedback.…”

Section: Introductionmentioning

confidence: 99%

NOx sensor cross sensitivity model and simultaneous prediction of NOx and NH3 slip from automotive catalytic converters under real driving conditions

Plá

Piqueras

Bares

et al. 2020

This work presents the development of a model to capture the NOx sensors cross sensitivity behavior based on [Formula: see text] sensor cell temperature, as well as a model do predict the slip of the NOx and NH3 after the SCR catalyst, as a way to reduce the error in the exhaust emissions estimation needed for feedback SCR control strategies. The emissions prediction model is based on the different cross sensitivity behavior of two distinct NOx sensors. The proposed models were tested and compared on a fully instrumented engine test bench when applied in a Worldwide harmonized Light vehicles Test Cycle (WLTC) and a full map cycle. As a result, the proposed model showed for NOx sensors cross sensitivity estimation an overall improvement of 34.8% for sensor 1 and 31.0% for sensor 2, and in terms of emissions prediction an overall improvement of 36.3% for NOx and 45.5% for NH3 slip.