Diesel Engine Aftertreatment Systems Research Articles

Control-Oriented Modeling and Observer-Based Estimation of Solid and Gas Temperatures for a Diesel Engine Aftertreatment System

Diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) have become standard components in diesel engine aftertreatment systems to remove carbon monoxide (CO), unburned hydrocarbon (HC), and particulate matter (PM) emissions. Many studies have been focused on improving the performances of DOCs and DPFs, which have been found to be influenced significantly by their respective thermal behaviors. The objective of this research is to develop a control-oriented thermal model for a DOC + DPF aftertreatment system. The control-oriented model is established by considering both thermal inertia of each component and chemical reactions inside it. Engine-out, DOC-out, and DPF-out emissions have been analyzed before simplified empirical models are proposed for the prediction of cared emission species. Experimental validation results show that the control-oriented models are capable of capturing both the gas phase and the solid phase thermal dynamics of a DOC and a DPF. An observer, designed based on the control-oriented solid temperature model and exhaust gas temperature model, can estimate the DOC and DPF gas and solid temperatures accurately in comparison with the measurements. The control-oriented thermal models and observer will be beneficial in the integrated engine and aftertreatment system control.

The effect of a H2/CO mixture at varying ratios on the diesel particulate filter regeneration process: Towards an optimised fuel reformer design – Diesel engine aftertreatment system

The work described in this paper aims to assist in the development of an exhaust gas fuel reformer for the enhancement of diesel particulate filter (DPF) aftertreatment performance. This was achieved by introducing H2 and CO at various mixture ratios at a concentration of 6% (v/v) to a standardised DPF regeneration process in order to identify an optimised mixture ratio. In addition to this, emission measurements were performed pre and post filter to identify the impact of the additional mixtures on various emission components. A mixture ratio of 60% H2 balanced with CO was identified as the optimised mixture ratio. This was due to this configuration demonstrating one of the most proficient regeneration profiles at a relatively low mean filter temperature of approximately 630 °C. Further to this, it was also noted that the addition of H2 or H2 and CO to the regeneration process resulted in an increase in NOx post filter while total hydrocarbons were reduced. Furthermore, the H2/CO mixture addition resulted in an increase in CO2 post filter, the levels of which were proportional to the volume of CO contained within the introduced mixture.

Oxygen Concentration Dynamic Model and Observer-Based Estimation Through a Diesel Engine Aftertreatment System

Due to the chemical reactions occurring inside the diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) that are commonly equipped on diesel engines, the exhaust gas oxygen concentrations considerably vary through the aftertreatment systems. Oxygen concentration in exhaust gas is important for the performance of catalysts such as the NOx conversion efficiencies of the selective catalytic reduction systems and lean NOx traps. Moreover, in the presence of a low-pressure loop exhaust gas recirculation, the exhaust gas oxygen concentration after DPF also influences the in-cylinder combustion. From system control, estimation, and analysis viewpoints, it is thus imperative to have a control-oriented model to describe the oxygen concentration dynamics across the DOC and DPF. In this paper, a physics-based, lumped-parameter, control-oriented DOC–DPF oxygen concentration dynamic model was developed with a multi-objective optimization method and validated with the experimental data obtained on a medium-duty diesel engine equipped with a full suite of aftertreatment systems. Experimental results show that the model can well capture the oxygen dynamics across the diesel engine aftertreatment systems. As an application of the experimentally validated model, an observer was designed to estimate the DOC-out and DPF-out oxygen concentrations in real time. Experimental results show that the estimated states from the proposed observer can converge to the measured signals fastly and accurately.

NO and NO2 Concentration Modeling and Observer-Based Estimation Across a Diesel Engine Aftertreatment System

This paper presents an experimentally validated control-oriented model and an observer for diesel oxidation catalyst (DOC)-diesel particulate filter (DPF) system in the context of exhaust gas NO and NO2 concentration estimations. NO and NO2 have different reaction characteristics within DPF and selective catalytic reduction (SCR) systems, two most promising diesel engine aftertreatment systems. Although the majority of diesel engine-out NOx emissions is NO, the commonly used DOC located upstream of a DPF and a SCR can convert a considerable amount of NO to NO2. Knowledge of the NO/NO2 ratio in exhaust gas is thus meaningful for the control and diagnosis of DPF and SCR systems. Existing onboard NOx sensors cannot differentiate NO and NO2, and such a sensory deficiency makes separate considerations of NO and NO2 in SCR control design challenging. To tackle this problem, a control-oriented dynamic model, which can capture the main NO and NO2 dynamics from engine-out, through DOC, and to DPF, was developed. Due to the computational limitation concerns, DOC and DPF are assumed to be standard continuously stirred tank reactors in order to obtain a 0D ordinary differential equation model. Based on the model, an observer, with the measurement from a commercially available NOx sensor, was designed to estimate the NO and NO2 concentrations in the exhaust gas along the aftertreatment systems. The stability of the observer was shown through a Lyapunov analysis assisted by insight into the system characteristics. The control-oriented model and the observer were validated with engine experimental data and the measured NO/NO2 concentrations by a Horiba gas analyzer. Experimental results show that the model can accurately predict the main engine-out/DOC/DPF NO/NO2 dynamics very well in semisteady-state tests. For the proposed observer, the predictions converge to the model values and estimate the NO and NO2 concentrations in the aftertreatment system well.

CO Emission Model for an Integrated Diesel Engine, Emissions, and Exhaust Aftertreatment System Level Model

CO Emission Model for an Integrated Diesel Engine, Emissions, and Exhaust Aftertreatment System Level Model

04/00406 A new optimizing technique of a diesel engine aftertreatment system using HC DeNO x catalyst : Ueda, M. et al. JSAE Review, 2003, 24, (1), 47–51

04/00406 A new optimizing technique of a diesel engine aftertreatment system using HC DeNO x catalyst : Ueda, M. et al. JSAE Review, 2003, 24, (1), 47–51

A new optimizing technique of a diesel engine aftertreatment system using HC DeNo x catalyst : Ueda, O. et al. JSAE Review, 2003, 24, (1), 47–51

A new optimizing technique of a diesel engine aftertreatment system using HC DeNo x catalyst : Ueda, O. et al. JSAE Review, 2003, 24, (1), 47–51

A new optimizing technique of a diesel engine aftertreatment system using HC DeNo x catalyst

A new method that optimizes a control map of hydrocarbon (HC) addition to diesel exhaust gas for HC type Selective Catalytic Reduction DeNO x catalyst system has been developed. This method comprises a numerical model and a new optimization technique. The numerical model is capable of predicting performance of HC DeNO x with diesel fuel as a supplemental reductant. The control map of HC addition was optimized with the evolutionary programming based on the evolution of living things. As a result, NO x conversion with the optimized control map was found to be greater by 21% than that with the conventional control on Japanese 10–15 mode.