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As new passenger cars are constantly getting cleaner, their contribution to air pollution is in large part defined by the in-use emissions degradation. In this respect, malfunctions in emissions-related components may play an important role to the contribution of passenger cars in air pollution. This paper assesses the impact of malfunctions of selected emissions related components to the pollutant emissions and evaluates the response of the OBD system to these malfunctions, under legislated and non-legislated driving cycles. The emissions-related components subjected to malfunctions are, for gasoline fuelled cars oxygen sensor and catalytic converter, and for diesel cars Exhaust Gas Recirculation system (EGR) and diesel Particulate Filter (DPF). For gasoline cars, the results show that total malfunctions of the above components result in up to two orders of magnitude increase in pollutant emissions.

To meet future stringent emission regulations such as Euro6, the design and control of diesel exhaust after-treatment systems will become more complex in order to ensure their optimum operation over time. Moreover, because of the strong pressure for CO₂ emissions reduction, the average exhaust temperature is expected to decrease, posing significant challenges on exhaust after-treatment. Diesel Oxidation Catalysts (DOCs) are already widely used to reduce CO and hydrocarbons (HC) from diesel engine emissions. In addition, DOC is also used to control the NO₂/NOx ratio and to generate the exothermic reactions necessary for the thermal regeneration of Diesel Particulate Filter (DPF) and NOx Storage and Reduction catalysts (NSR). The expected temperature decrease of diesel exhaust will adversely affect the CO and unburned hydrocarbons (UHC) conversion efficiency of the catalysts. Therefore, the development cost for the design and control of new DOCs is increasing.

It is commonly accepted that future powertrains will be based to a large extent on hybrid architectures, in order to optimize fuel efficiency and reduce CO₂ emissions. Hybrid operation is typically achieved with frequent engine start-and-stops during real-world as well as during the legislated driving cycles. The cooling of the exhaust system during engine stop may pose problems if the substrate temperature drops below the light-off temperature. Therefore, the design and thermal management of after-treatment systems for hybrid applications should consider the 3-dimensional heat transfer problem carefully. On the other hand, the after-treatment system calculation in the concept design phase is closely linked with engine calibration, taking into account the hybridization strategy. Therefore, there is a strong need to couple engine simulation with 3d aftertreatment predictions.

This paper studies the effect of a Catalyzed Diesel Particle Filter (CDPF) on the emission profile of a Euro 4 diesel vehicle operated on low sulfur fuel and lubrication oil. The vehicle was tested in its original configuration and with the CDPF retrofitted in place of its main underbody catalyst. Experiments included steady state tests, the certification cycle and real-world high speed transient driving conditions. Measurements included total particle mass collected on Teflon-coated filters, total particle number measured by a condensation particle counter, size distributions determined by a Scanning Mobility Particle Sizer and chemical analysis of the mass collected for elemental and organic carbon, ions, PAHs, and trace elements. Results showed that the vehicle complies with the Euro 4 emission limits when tested over the type-approval NEDC, but it emits more nitrogen oxides and, in some cases, more particulate matter when tested over real-world test cycles.

A new metal foam material for diesel particulate filtration, trademarked as INCOFOAM® HighTemp, was recently presented. Extensive tests showed the potential of achieving filtration efficiencies of the order of 85% or more at low pressure drop using a radial flow design concept with graded foam porosity. By applying a catalytic washcoat, the foam exhibits enhanced gas mixing and thus higher conversion efficiencies at high space velocities. In addition, due to an excellent soot-catalyst contact, the washcoated foam exhibited high catalytic regeneration rates. The present paper focuses on a novel “cross-flow” design concept for a better filtration/pressure drop trade-off as well as application of the foam as an oxidation catalyst substrate. The experimental testing starts from small-scale reactors and proceeds to real exhaust testing on the engine bench as well as vehicle tests on the chassis dynamometer and on-road testing.

This work studies the formation of nucleation mode (NM) particles from a Euro 3 passenger car operating on 280 ppm wt. sulfur fuel, during on-road plume chasing and in the laboratory. The vehicle produced a distinct NM when its speed exceeded 100 km/h in both sampling environments. A higher particle number (up to 8 times) after 4 min at constant speed was measured when this speed was approached from a lower than from a higher speed. The variability in the measurement of NM particles was explained using literature information on sulfur-to-sulfate conversion over a catalyst and, in particular, on the extent and rate of sulfate storage and release mechanisms. All evidence led to the conclusion that storage and release processes take several minutes to conclude after a step-wise change in speed and have significant implications in the total particle number measurements during steady-speed testing.

Catalyzed wall-flow particulate filters are increasingly applied in diesel exhaust after-treatment for multiple purposes, including low-temperature catalytic regeneration, CO and hydrocarbon conversion, as well as exothermic heat generation during forced regeneration. In order to optimize Precious Metals usage, it may be advantageous to apply the catalytic coating non-uniformly in the DPF, a technology referred to as “catalyst zoning”. In order to simulate the behavior of such a filter, one has to consider coupled transport-reaction modeling. In this work, a previously developed model is calibrated versus experimental data obtained with full-scale catalyzed filters on the engine dynamometer. In a next step, the model is validated under a variety of operating conditions using engine experiments with zoned filters. The performance of the zoned catalyst is analyzed by examining the transient temperature and species profiles in the inlet and outlet channels.

An alternative metal foam substrate for exhaust aftertreatment applications has been recently presented and characterized. The present paper focuses on the potential of the metal foam technology as an efficient DOC and CDPF substrates on real-world conditions. The target platform is a mid-size passenger car and the methodology includes both modeling and experiments. The experimental testing starts from small-scale reactor characterization of the basic heat/mass transfer properties and chemical kinetics. The results show that the foam structure exhibits excellent mass-transport properties offering possibilities for precious metal and catalyst volume savings for oxidation catalyst applications. These results are also used to calibrate an advanced 2-dimensional model which is able to predict the transient filtration and reaction phenomena in axial and radial flow systems.

As the Diesel Particulate Filter (DPF) technology is nowadays established, research is currently focusing on meeting the emission and durability requirements by proper system design. This paper focuses on the optimum combination between the catalytic coating and substrate structural properties using experimental and simulation methodologies. The application of these methodologies will be illustrated for the case of SiC substrates coated with innovative sol-gel coatings. Coated samples are characterized versus their uncoated counterparts. Multi-dimensional DOC and DPF simulation models are used to study several effects parametrically and increase our understanding on the governing phenomena. The comparative analysis of DOC/DPF systems covers filtration – pressure drop characteristics, CO/HC/NO oxidation performance, effect of washcoat amount and catalyst dispersion on oxidation activity and finally passive regeneration performance.

XP-SiC is an innovative type of a porous substrate material on the basis of a reaction formed SiC for DPF applications. The high porosity, large pore size inside the cell wall and low specific weight are the special characteristics of this substrate. The aim of the current paper is to present an investigation based on the experimental and modeling approaches to evaluate the back pressure, filtration efficiency and the thermal durability. The latter one was assessed by measuring and predicting the temperature field, as well as calculating the thermal stresses. For this purpose the filter was modeled in the commercial computational code axitrap as a stand-alone tool, in which the conservation equations of mass continuity, momentum, energy and species were solved. The soot filtrations, loading as well as the regeneration by fuel-borne catalyst were modeled.

The objective of this paper is to study the parameters affecting the evolution of “uncontrolled” regeneration in diesel particulate filters with fuel-borne catalyst (FBC) support with emphasis on the development of thermal stresses critical for filter durability. The study is based on experiments performed on engine dynamometer, corresponding to “worst-case” scenario, as well as on advanced, multi-dimensional mathematical modeling. A new 2-dimensional mathematical model is presented which introduces an additional dimension across the soot layer and wall. With this dimension it is possible to take into account the variability of catalyst/soot ratio in the layer and to compute intra-layer composition gradients. The latter are important since they induce interesting O2 diffusion phenomena, which affect the regeneration evolution.

A novel method for the evaluation of fuel-borne catalysts effect on DPF regeneration temperature is presented. The method is simple and allows for the in-situ determination of the regeneration temperature. It consists of the engine and trap preconditioning, the trap loading cycle and the regeneration phase. The repeatability of the method is better than ±1% of average value measured. The method is capable of distinguishing very low concentrations of the metal catalyst. The application of the method with different concentrations of the same catalyst does not require the use of fresh traps. For the evaluation of different catalysts however it is recommended to use a fresh trap, since the prescribed preconditioning is not capable of eliminating the effects of the previous additive.

The pressure for compact and efficient deNO systems has led to increased interest of incorporating SCR coatings in the DPF walls. This technology could be very attractive especially if high amounts of washcoat loadings could be impregnated in the DPF porous walls, which is only possible with high porosity filters. To counterbalance the filtration and backpressure drawbacks from such high porosity applications, the layered wall technology has already been proposed towards minimizing soot penetration in the wall and maximizing filtration efficiency. In order to deal with the understanding of the complex interactions in such advanced systems and assist their design optimization, this paper presents an advanced modeling framework and selected results from simulation studies trying to illustrate the governing phenomena affecting deNO performance and passive DPF regeneration in the above combined systems.

The successful design and especially the control of the SCR system is a challenging process that can be supported by the application of simulation tools. As a first step, we employ physico-chemically informed ‘off-line’ models that are calibrated with the help of targeted small- and full-scale tests. Despite their high level of sophistication, this SCR model is able to be integrated in a control-oriented simulation software platform and connected to other powertrain simulation blocks. The target is to use this simulation platform as a virtual environment for the development and optimization of SCR control strategies. The above process is demonstrated in the case of a passenger car SCR. The model is calibrated at both fresh and aged catalyst condition and validated using experimental data from the engine bench under a wide variety of operating conditions. Next, the calibrated model was coupled with embedded control models, developed for Euro 6 passenger car powertrains.

The objective of this study is to present a particulate filter concept, based on a new porous material: INCOFOAM® HighTemp, a Ni-based superalloy foam. The paper examines the filtration and pressure drop characteristics as well as the regeneration performance of different filter configurations, based on experimental data and modeling. A number of different foam structures with variable pore characteristics are studied. The experimental testing covers flow and pressure drop behavior with air and exhaust gas, filtration efficiency measurements as function of particle size and regeneration rate measurements. The testing starts from mini-scale reactors and proceeds to real exhaust testing on the engine bench as well as vehicle tests on the chassis dynamometer and on-road. In parallel, a previously developed mathematical model is applied to study and understand the filtration and pressure drop mechanisms in the case of clean and soot loaded filters.

Diesel engines are widespread in both passenger car and heavy duty truck applications. However, despite that the combustion concepts are similar in the two cases, the engine calibration required for compliance with the different emission standards leads to distinct particle emission behavior from the two categories. This paper compares the exhaust particle emissions from heavy duty engines with typical diesel passenger cars of similar emission standard and/or emission control technology. Measurements were conducted with the same sampling system and sampling protocol to avoid interferences induced by the sampling methodology. A range of particle properties were studied, including mass, number of solid and total particles and total particle surface. For comparability, the results are expressed per unit of exhaust volume, per unit of fuel consumed and per unit of distance driven.

Diesel particulate filters are today widely accepted as a viable technology for drastically reducing particulate emissions from diesel engines. Current applications are based on some form of catalytic assistance for the filter regeneration purposes, either in the form of a fuel borne catalyst or by employing catalyzed filters. This paper presents an experimental and computational study of the prevailing reaction mechanisms in the catalyst supported DPF systems. The knowledge of the soot reaction kinetics in uncatalyzed filters with O2 and NO2 is a prerequisite in this respect. Next, the reaction rates in the case of using a Ce-based fuel-borne catalyst are evaluated. Emphasis is given on the importance of oxygen diffusion effects during uncontrolled regeneration. Finally, the regeneration mechanisms in a catalyst coated filter are studied.

This paper presents a mathematical model for the simulation of NOx traps during the storage and the regeneration phases. The objective is to validate the model under realistic exhaust gas conditions during NOx storage and release phases. The model is based on a previous modeling platform developed by Aristotle University which simulates the behavior of 3-way catalysts. The previous model is extended to include the additional reactions taking place on a NOx trap, with particular emphasis on the calculation of thermodynamic equilibrium effects. Moreover, the model includes the necessary reactions to simulate catalyst sulfation and de-sulfation processes. In parallel, a set of measurements are conducted under well controlled conditions with real diesel exhaust to study the storage and release phenomena under various operating conditions. The experimental data are used to calibrate the reaction kinetics and validate the model.

The possibility to employ a single-brick system with a catalyzed filter (CDPF) for the after-treatment of diesel engines is potentially a promising and cost-effective solution. In the first part of this paper, the effectiveness of a single brick CDPF system towards reducing the gaseous CO and HC emissions is investigated experimentally and computationally. The second part of the paper deals with the behavior of single brick catalyzed filters compared with two brick systems comprising an upstream oxidation catalyst. The main differences of the two systems are highlighted in terms of regeneration efficiency and thermal loading, based on simulation results. The modeling work is based on a 3-dimensional model of the catalyzed filter and an axi-symmetric model of the oxidation catalyst. Model validations are presented based on engine bench testing.

In Plug in hybrid electric vehicles (PHEVs), the management of the main drivetrain components and the shift between pure electric and hybrid propulsion is decided by the on-board energy management system (EMS). The EMS decisions have a direct impact on CO2 emissions and need to be optimized to achieve as low emissions as possible. This paper presents optimization methods for EMS algorithms of a parallel P2 PHEV. Two different supervisory control algorithms are examined, employing simulations on a validated PHEV platform. An Equivalent Consumption Minimization Strategy (ECMS) algorithm is implemented and compared to a rule-based one, the latter derived by back-engineering of available experimental data. The different EMS algorithms are analyzed and compared on an equal basis in terms of distance, demanded energy and state of charge levels over different driving cycles.