Control-oriented modelling and diagnostics of diesel after-treatment catalysts

International Journal of Engine Research

Sanchis

et al. 2020

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.

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Section: Methodsmentioning

confidence: 99%

Ammonia injection optimization for selective catalytic reduction aftertreatment systems

International Journal of Engine Research

Sanchis

et al. 2020

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“…Aiming to assess the level of improvement of the proposed model, the EKF was compared with another methodology (0D model) already used and addressed by several authors in the literature. 34,44,45 The 0D model has three states: N O x and N H 3 gas phase concentrations and catalyst surface coverage fraction. The model has as input signals: catalyst temperature, exhaust mass flow, N O x concentration before the catalyst and the amount of urea injected, and as output signals, N O x and N H 3 slip.…”

Section: Resultsmentioning

confidence: 99%

“…(ii) The dynamics of N H 3 emissions is much slower than that of N O x . 16,34 In fact, as the ammonia coverage varies slowly, the N H 3 slip which is dependent on it, will also vary slowly.…”

Section: Methodsmentioning

confidence: 99%

Simultaneous NOx and NH3 slip prediction in a SCR catalyst under real driving conditions including potential urea injection failures

Piqueras

International Journal of Engine Research

et al. 2021

To reach the emission limits imposed by governments and reduce the negative impact on the environment, the use of aftertreatment systems has become essential for internal combustion engine (ICE) based powertrains. In particular, the selective catalytic reduction (SCR) system is a widespread aftertreatment technology with high efficiency for [Formula: see text] abatement which shows complex dynamics and requires urea injection as reducing agent. Current urea injection strategies usually rely on the [Formula: see text] emissions feedback. This work presents a model for the on-line simultaneous prediction of [Formula: see text] and [Formula: see text] emissions after the SCR catalyst, allowing the emissions estimation even in conditions of urea injector failure, when it is not possible to rely on the injector feedback signal. The proposed model is based on state of the art on-board after-treatment instrumentation and proposes an extended Kalman filter (EKF) to combine a data-based model and the analysis of sensor signals to provide a reliable estimation of [Formula: see text] and [Formula: see text] slip. The proposed strategy is experimentally assessed in dynamic driving cycles, such as Worldwide harmonised Light vehicles Test Cycle (WLTC) and Standardised Random Test (RTS). The proposed method is evaluated in standard conditions (without failures) and with urea injection failures of 25% and 120% of the nominal injection amount. As a result, the prediction on [Formula: see text] and [Formula: see text] slip has been improved in all injection failure conditions, by an overall average of 47.8% and 61.8%, respectively, when compared to state-of-the-art control oriented models (physically based zero dimensional model or data-based).

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“…Therefore, NOx dynamics after the catalyst is mainly dependent on NOx dynamics before catalyst, since the SCR is always working with high NOx conversion efficiency rates [25]. (ii) The NH3 emissions dynamics are considerably slower than NOx [25,26]. Since the ammonia coverage varies slowly, the NH3 slip that depends on it will also vary slowly.…”

Section: Observer and Model Designmentioning

confidence: 99%

Ammonia injection failure diagnostic and correction in engine after-treatment system by NOx and NH3 emissions observation

Sanchis

et al. 2022

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