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On-Board Diagnostics for emissions-related components require the monitoring of the catalytic converter performance. Currently, the dual Exhaust Gas Oxygen (EGO) sensor method is the only proven method for monitoring the catalyst performance for hydrocarbons (HC). The premise for using the dual oxygen sensor method is that a catalyst with good oxygen storage capacity (OSC) will perform better than a catalyst with lower OSC. A statistical relationship has been developed to correlate HC performance with changes in OSC. The current algorithms are susceptible to false illumination of the Malfunction Indication Light (MIL) due to: 1. The accuracy with which the diagnostic algorithm can predict a catalyst malfunction condition, and 2. The precision with which the algorithm can consistently predict a malfunction. A new algorithm has been developed that provides a significant improvement in correlation between the EGO sensor signals and hydrocarbon emissions.

An overview is given on the state of the art of a new catalytic exhaust gas aftertreatment device for diesel engines. The function of a precious metal based, flow-through type diesel oxidation catalyst is explained. Much attention is paid to the durability of the diesel oxidation catalyst and especially to the influence of poisoning elements on the catalytic activity. Detailed data on the interaction of poisoning elements such as sulfur, zinc and phosphorus with the catalytic active sites are given. Finally it is demonstrated that it is possible to meet the stringent emission standards for diesel passenger cars in Europe with a new catalyst generation over 80.000 km AMA aging.

Three-way catalysts (TWC) to remove the HC, CO, and NOx pollutants from the exhaust of gasoline powered vehicles employ rhodium in combination with platinum and palladium. Of these precious metals, rhodium is by far the most expensive. Since it is so heavily used for its NOx reduction capabilities, the amount per vehicle approaches and sometimes exceeds the naturally occurring mine ratio. A program was conducted to determine the feasibility of a non-rhodium TWC catalyst. It showed that Pt and Pd in conjunction with other washcoat support materials exhibited relatively good TWC characteristics compared to a Pt/Rh catalyst after engine dynamometer aging. In FTP evaluations this new REDOX type catalyst gave comparable HC and CO efficiency and 85% of the NOx efficiency of a Pt/Rh-containing catalyst. Presently the operating window is being defined but comparisons to conventional Pt/Pd and Pt/Rh catalysts have been made under a number of conditions.

A new technique has been developed to assess the deterioration of hydrocarbon lightoff during FTP Phase 1. This method maps the dynamic real time data onto the hydrocarbon conversion/gas phase temperature plane to show the instantaneous hydrocarbon activity as a function of the exhaust temperature. Clearly, the map exhibits an apparent hysteresis bifurcation. The bifurcation is thought to be predominantly related to catalyst surface temperature. The hysteresis envelope of the map expands with aging severity. Therefore, the map can be used as a measure of catalyst deactivation.

In one-dimensional engine simulation programs the simulation of engine performance is mostly done by parameter fitting in order to match simulations with experimental data. The extensive fitting procedure is especially needed for emissions formation - CO, HC, NO, soot - simulations. An alternative to this approach is, to calculate the emissions based on detailed kinetic models. This however demands that the in-cylinder combustion-flow interaction can be modeled accurately, and that the CPU time needed for the model is still acceptable. PDF based stochastic reactor models offer one possible solution. They usually introduce only one (time dependent) parameter - the mixing time - to model the influence of flow on the chemistry. They offer the prediction of the heat release, together with all emission formation, if the optimum mixing time is given.

The California LEV1 II program will be introduced in the year 2003 and requires a further reduction of the exhaust emissions of passenger cars. The cold start emissions represent the main part of the total emissions of the FTP2-Cycle. Cold start emissions can be efficiently reduced by injecting secondary air (SA) in the exhaust port making compliance with the most stringent standards possible. The thermochemical conditions (mixing rate and temperature of secondary air and exhaust gas, exhaust gas composition, etc) prevailing in the exhaust system are described in this paper. This provides knowledge of the conditions for auto ignition of the mixture within the exhaust manifold. The thus established exothermal reaction (exhaust gas post-combustion) results in a shorter time to light-off temperature of the catalyst. The mechanisms of this combustion are studied at different engine idle conditions.

The technical issues related to NOx abatement for diesel applications are summarized. Data on improved catalysts and a novel approach which involves temporarily trapping of NOx before reduction are presented. New high temperature lean NOx materials have been identified which have better hydrothermal stability than the state of the art Cu/ZSM-5. One of these materials, Catalyst A, was shown to reduce the NOx emitted from a 2.5 L diesel engine at temperatures ≥ 350°C using injected diesel fuel as a reductant. Catalyst A also showed reasonably good durability after aging for 500 h at ca. 500°C on a 14 L diesel truck engine. Pt/Al2O3, a low temperature lean NOx reduction catalyst (200-300°C), demonstrated fairly good performance after 125 h of aging on a 4 L diesel truck engine, however sulfate make and N2O formation are high on this material. New low temperature NOx traps show promise for transient removal of NOx below 200-400°C.

The plasma assisted catalytic reactor (PACR) approach to lean NOx abatement is a two step process. The non-thermal plasma oxidizes the engine out NO to NO2, which is then reduced to N2 over a catalyst using a hydrocarbon reductant. Whereas it was once believed that the plasma itself directly reduces NOx to N2, it has been shown that the plasma's principle function is to oxidize NO to NO2. This is accomplished without oxidizing SO2 to SO3, resulting in lower sulfate particulate when compared to standard lean NOx catalysis using platinum or reducible oxide catalysts. We have performed reactor studies comparing the relative reducibility of NO2 and NO in a synthetic diesel exhaust using diesel fuel as the hydrocarbon reductant, with attention to time-on stream behavior and determination of NOx reversibly adsorbed on the catalyst. We find that at 200°C, 50% of the NO2 disappearance over Na-ZSM5 is attributable to reversible adsorption on the catalyst.

Synthetic fuels are expected to play an important role for future mobility, because they can be introduced seamlessly alongside conventional fuels without the need for new infrastructure. Thus, understanding the interaction of GTL fuels with modern engines, and aftertreatment systems, is important. The current study investigates potential benefits of GTL fuel in respect of diesel particulate filters (DPF). Experiments were conducted on a Euro 4 TDI engine, comparing the DPF response to two different fuels, normal diesel and GTL fuel. The investigation focused on the accumulation and regeneration behavior of the DPF. Results indicated that GTL fuel reduced particulate formation to such an extent that the regeneration cycle was significantly elongated, by ∼70% compared with conventional diesel. Thus, the engine could operate for this increased time before the DPF reached maximum load and regeneration was needed.

The desire for improved fuel economy, and lower emissions of green house gases, such as CO2, is projected to increase the demand for diesel and lean-burn gasoline engines throughout the world. Several commercial diesel oxidation catalysts (DOCs) were developed in the last 3-4 years to reduce hydrocarbon, CO, and particulates emitted from the exhaust of diesel passenger cars and trucks. To meet future U.S. and European NOx standards, it is essential to develop catalyst technology that will allow NOx reduction in addition to the other three pollutants. Two materials that attracted great attention as lean NOx catalysts are the Cu/ZSM-5 and Pt based. Cu containing ZSM-5 are active for lean-NOx reduction at temperatures above 350°C, provided sufficient hydrocarbons are present as reductants.

Several different possibilities will be described and discussed on the processes of reducing NOx in lean-burn gasoline and diesel engines. In-company studies were conducted on zeolitic catalysts. With lean-burn spark-ignition engines, hydrocarbons in the exhaust gas act as a reducing agent. In stationary conditions at λ = 1.2, NOx conversion rates of approx. 45 % were achieved. With diesel engines, the only promising variant is SCR technology using urea as a reducing agent. The remaining problems are still the low space velocity and the narrow temperature window of the catalyst. The production of reaction products and secondary reactions of urea with other components in the diesel exhaust gas are still unclarified.

Close coupled catalysts represent a solution being pursued by automotive engineers to meet stringent LEV and ULEV emission standards. Close coupled systems provide fast light-off by utilizing the energy in the exhaust gas rather than energy supplied by an auxiliary source such as an electrically heated catalyst or a burner in the exhaust. Previous close coupled catalyst designs were limited by the temperature capability of the catalyst coatings. A successful close coupled catalyst technology has been developed 'that is resistant to higher temperature deactivation. This technology is able to function well at low temperature during the vehicle cold start when light-off is critical. The close coupled catalyst technology has approached ULEV emission levels after aging at 1050°C for 24 hours. This study will present experimental results for a close coupled catalyst including the selection of catalyst volume, cross sectional area and combination of catalyst technologies.

The revisions in the United States Clean Air Act of 1990 and recent regulatory actions taken by the California Air Resources Board and European Economic Community require the development of automobiles with much lower tailpipe emissions. A significant portion of the total pollutants emitted to the atmosphere by motor vehicles occurs immediately following the startup of the engine when the engine block and exhaust manifold are cold, and the catalytic converter has not yet reached high conversion efficiencies. An effective, energy efficient strategy for dealing with cold start hydrocarbon using carbon-free hydrocarbon traps and heat exchange related TWC catalyst beds has been successfully tested on a wide variety of current model vehicles. In each case U.S. FTP 75 total hydrocarbon emissions were reduced between 45 - 75% versus the vehicle's stock exhaust system.

This paper compares 4 different EGR systems by means of simulation in GT-Power. The demands of optimum massive EGR and fresh air rates were based on experimental results. The experimental data were used to calibrate the model and ROHR, in particular. The main aim was to investigate the influence of pumping work on engine and vehicle fuel consumption (thus CO2 production) in different EGR layouts using optimum VG turbine control. These EGR systems differ in the source of pressure drop between the exhaust and intake pipes. Firstly, the engine settings were optimized under steady operation - BSFC was minimized while taking into account both the required EGR rate and fresh air mass flow. Secondly, transient simulations (NEDC cycle) were carried out - a full engine model was used to obtain detailed information on important parameters. The study shows the necessity to use natural pressure differences or renewable pressure losses if reasonable fuel consumption is to be achieved.

The regulations for mobile applications will become stricter in Euro 6 and further emission levels and require the use of active aftertreatment methods for NOX and particulate matter. SCR and LNT have been both used commercially for mobile NOX removal. An alternative system is based on the combination of these two technologies. Developments of catalysts and whole systems as well as final vehicle demonstrations are discussed in this study. The small and full-size catalyst development experiments resulted in PtRh/LNT with optimized noble metal loadings and Cu-SCR catalyst having a high durability and ammonia adsorption capacity. For this study, an aftertreatment system consisting of LNT plus exhaust bypass, passive SCR and engine independent reductant supply by on-board exhaust fuel reforming was developed and investigated. The concept definition considers NOX conversion, CO2 drawback and system complexity.

Motorcycle exhaust emission standards throughout the world are becoming more stringent. Emission control systems utilizing the catalytic converter are already in production in Taiwan for 2-stroke engine motorcycles. Catalysts designed for 2-stroke engines encounter a more severe exhaust environment than do those designed for 4-stroke engines. The two aspects of increased severity are the higher temperatures and higher stresses due to engine vibrations. Precious metal catalysts have been designed to operate in the thermal environment of 2-stroke engines and such catalysts have been successfully applied to both metal and ceramic substrates. However, until now, only the metal substrate catalysts have been utilized in motorcycle application. Ceramic based catalysts have not been considered because the mounting material that holds the catalyst substrate in place did not have enough durability to withstand the thermal/vibrational forces encountered in 2-stroke engine exhaust.

More stringent emissions regulations, space limitations for catalytic converters in modern automotive applications, and new engine technologies constitute design challenges for today's engineers. In that context high cell density thinwall and ultrathinwall ceramic substrates have been designed into advanced catalytic converters. Whereas the majority of these substrates have a square cell geometry, a potential for further emissions improvement has been predicted for hexagonal cell structures. In order to verify these predictions, a ceramic substrate has been developed combining the features of high cell density, ultrathin cell walls, and hexagonal cell structure. Based on modeling data, the actual cell density and wall thickness of the hexagonal cell substrate will be defined. The performance of that substrate will be assessed by comparing experimental emissions results using two modern Volkswagen engines.

The spray development, combustion and emissions in a 1.9L optical, four-cylinder, direct-injection diesel engine were investigated by means of pressure analysis, high-speed cinematography, the two-colour method and exhaust gas analysis for various levels of exhaust gas recirculation (EGR), three EGR temperatures (uncontrolled, hot and cold) and three fuels (diesel, n-heptane and a two-component fuel 7D3N). Engine operating conditions included 1000 rpm/idle and 2000 rpm/2bar with EGR-rates ranging from 0 to 70%. Independent of rate, EGR was found to have a very small effect on spray angle and spray tip penetration but the auto-ignition sites seemed to increase in size and number at higher EGR-rates with associated reduction in the flame luminosity and flame temperature, by, say, 100K at 50% EGR.

A common practice to improve vehicle fuel economy is to employ a fuel cut-off strategy on deceleration. This practice exposes the TWC exhaust catalyst to varying concentrations of oxygen depending on the vehicle control strategy. Since it is well known that exposure to oxygen at high temperature is deleterious to long term catalyst durability, it is important to understand the impact of oxygen concentration and temperature on catalyst performance. Simulated fuel cut agings at about 1%, 3%, and 9% oxygen concentration were compared to a full fuel cut aging (21% oxygen concentration). It was found that even small concentrations of oxygen at high temperature damaged catalyst performance. Deactivation increased with increasing oxygen concentration and increasing temperature.