Control-Oriented Model of an SCR Catalytic Converter System

Schär, C. M.; Onder, Christopher H.; Geering, Hans P.; Elsener, Martin

doi:10.4271/2004-01-0153

Cited by 51 publications

(35 citation statements)

References 7 publications

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“…This result confirms the theoretical result, which showed that the optimal equivalence factor of the cumulated pollutant emissions is always constant (15). Both causal EEMS approaches maintain the correct NO x emission level by following the reference value for the NO x emissions using feedback control.…”

Section: Simulation Resultssupporting

confidence: 89%

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An Equivalent Emission Minimization Strategy for Causal Optimal Control of Diesel Engines

et al. 2014

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One of the main challenges during the development of operating strategies for modern diesel engines is the reduction of the CO 2 emissions, while complying with ever more stringent limits for the pollutant emissions. The inherent trade-off between the emissions of CO 2 and pollutants renders a simultaneous reduction difficult. Therefore, an optimal operating strategy is sought that yields minimal CO 2 emissions, while holding the cumulative pollutant emissions at the allowed level. Such an operating strategy can be obtained offline by solving a constrained optimal control problem. However, the final-value constraint on the cumulated pollutant emissions prevents this approach from being adopted for causal control. This paper proposes a framework for causal optimal control of diesel engines. The optimization problem can be solved online when the constrained minimization of the CO 2 emissions is reformulated as an unconstrained minimization of the CO 2 emissions and the weighted pollutant emissions (i.e., equivalent emissions). However, the weighting factors are not known a priori. A method for the online calculation of these weighting factors is proposed. It is based on the Hamilton-Jacobi-Bellman (HJB) equation and a physically motivated approximation of the optimal cost-to-go. A case study shows that the causal control strategy defined by the online calculation of the equivalence factor and the minimization of the equivalent emissions is only slightly inferior to the non-causal offline optimization, while being applicable to online control.Energies 2014, 7 1231

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Section: Simulation Resultssupporting

confidence: 89%

“…However, the EGA can be discretized spatially into a finite number of cells in order to obtain a set of ordinary differential equations. For example, in [15,16], this technique is used to obtain a control-oriented model of an SCR.…”

Section: System Descriptionmentioning

confidence: 99%

An Equivalent Emission Minimization Strategy for Causal Optimal Control of Diesel Engines

et al. 2014

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“…A lot of kinetic studies and meanwhile kinetic models have been published for several catalysts: Tronconi and Chatterjee et al [9][10][11] and Schär et al for a vanadia-based catalysts [12], we [13,14] as well as Chatterjee et al [11] for Fe zeolite catalysts and Olsson et al [15] for copper exchanged zeolites.…”

Section: Introductionmentioning

confidence: 98%

NH3-SCR on Fe zeolite catalysts – From model setup to NH3 dosing

Schuler

Votsmeier

Kiwic

et al. 2009

Chemical Engineering Journal

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“…NO x sensors are used to measure the NO x concentration downstream from the SCR system and feed it back to the SCR controller. However, research results have showed that NO x sensors have an enhanced cross sensitivity to NH 3 [17][18][19]. According to the structural characteristics of NO x sensors, the NH 3 inside the sensor is easily oxidized to NO x .…”

Section: Introductionmentioning

confidence: 99%

A New Dynamic Injection System of Urea-Water Solution for a Vehicular Select Catalyst Reduction System

Lin

Zhang

2016

Energies

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Abstract:Since the Euro-III standard was adopted, the main methods to inhibit NO x production in diesel engines are exhaust gas recirculation (EGR) and select catalyst reduction (SCR). On these methods SCR offers great fuel economy, so it has received wide attention. However, there also exists a trade-off law between NO x conversion efficiency and NH 3 slip under dynamic conditions. To inhibit NH 3 slip with high NO x conversion efficiency, a dynamic control method for a urea water solution (UWS) injection was investigated. The variation phenomena of SCR conversion efficiency with respect to the cross-sensitivity characteristics of the NO x sensor to NH 3 have been thoroughly analyzed. The methodology of "uncertain conversion efficiency curve tangent analysis" has been applied to estimate the concentration of the slipped NH 3 . The correction factor "ϕ" of UWS injection is obtained by a comparative calculation of the NO x conversion ability and subsequent NH 3 slip. It also includes methods of flow compensation and flow reduction. The proposed control method has been authenticated under dynamic conditions. In low frequency dynamic experiments, this control method has accurately justified the NH 3 slip process and inhibits the NH 3 emission to a lower level thereby improving the conversion efficiency to a value closer to the target value. The results of European transient cycle (ETC) experiments indicate that NH 3 emissions are reduced by 90.8% and the emission level of NO x is close to the Euro-V standard.

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Control-Oriented Model of an SCR Catalytic Converter System

Cited by 51 publications

References 7 publications

An Equivalent Emission Minimization Strategy for Causal Optimal Control of Diesel Engines

An Equivalent Emission Minimization Strategy for Causal Optimal Control of Diesel Engines

NH3-SCR on Fe zeolite catalysts – From model setup to NH3 dosing

A New Dynamic Injection System of Urea-Water Solution for a Vehicular Select Catalyst Reduction System

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