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This summary covers representative developments from 2008 in diesel regulations, engine technology, and NOx, particulate matter (PM), and hydrocarbon (HC) control. Europe is finalizing the Euro VI heavy-duty (HD) regulations for 2013 with the intent of technologically harmonizing with the US. A new particle number standard will be adopted. California is considering tightening the light-duty fleet average to US Tier 2 Bin 2 levels, and CO2 mandates are emerging in Europe for LD, and in the US for all vehicles. LD engine technology is focused on downsizing to deliver lower CO2 emissions, enabled by advances in boost and EGR (exhaust gas recirculation). Emerging concepts are shown for attaining Bin 2 emission levels. HD engines will make deNOx systems optional for even the tightest NOx standards, but deNOx systems enable much lower fuel consumption levels and will likely be used. NOx control is centered on SCR (selective catalytic reduction) for diverse applications.

This summary covers the developments from 2007 in diesel regulations, engine technology, and NOx and PM control. Regulatory developments are now focused on Europe, where heavy-duty regulations have been proposed for 2013. The regulations are similar in technology needs to US2010. Also, the European Commission proposed the first CO2 emission limits of 130 g/km, which are nearly at parity to the Japanese fuel economy standards. Engines are making very impressive progress, with clean combustion strategies in active development mainly for US light-duty application. Heavy-duty research engines are more focused on traditional approaches, and will provide numerous engine/aftertreatment options for hitting the tight US 2010 regulations. NOx control is centered on SCR (selective catalytic reduction) for diverse applications. Focus is on cold operation and system optimization. LNT (lean NOx traps) durability is quantified, and performance enhanced with a sulfur trap.

Diesel particulate filters are expected to be used on most passenger car applications designed to meet coming European emission standards, EU5 and EU6. Similar expectations hold for systems designed to meet US Tier 2 Bin 5 standards. Among the various products oxide filter materials, such as cordierite and aluminum titanate, are gaining growing interest due to their unique properties. Besides the intrinsic robustness of the filter products a well designed operating strategy is required for the successful use of filters. The operating strategy is comprised of two elements: the soot estimation and the regeneration strategy. In this paper the second element is discussed in detail by means of theoretical considerations as well as dedicated engine bench experiments. The impact the key operating variables, soot load, exhaust mass flow, oxygen content and temperature, have on the conditions inside the filter are discussed.

Diesel particulate filters are becoming a standard for most light duty diesel applications designed for European EU5 and EU6 regulations. Oxide based filter materials are continuing to gain significant interest and have been in high volume serial application since 2005. Compared to carbide materials they show some unique properties. With respect to the design, the length of a filter is a key variable. Usually the prime design consideration is the desired filter volume. The diameter or frontal area is then usually defined by packaging constraints. Finally, the length is adapted. The paper provides experimental data on the impact this key design parameter has on the pressure drop and the thermal behavior under “worst case” regeneration conditions. A wide range of soot loads (from 4 g/dm3 to 9 g/dm3) as well as filter lengths from 6″ to 12″ is considered and evaluated under comparable experimental conditions.

This review paper summarizes major developments in vehicular emissions regulations and technologies (light-duty, heavy-duty, gasoline, diesel) in 2012. First, the paper covers the key regulatory developments in the field, including finalized criteria pollutant tightening in California; and in Europe, the development of real-world driving emissions (RDE) standards. The US finalized LD (light-duty) greenhouse gas (GHG) regulation for 2017-25. The paper then gives a brief, high-level overview of key developments in LD and HD engine technology, covering both gasoline and diesel. Marked improvements in engine efficiency are summarized for gasoline and diesel engines to meet both the emerging NOx and GHG regulations. HD engines are just starting to demonstrate 50% brake thermal efficiency. NOx control technologies are then summarized, including SCR (selective catalytic reduction) with ammonia, and hydrocarbon-based approaches.

This summary covers the developments from 2006 in diesel regulations, engine combustion, and NOx and PM remediation. Regulatory developments are now focused on Europe, where light-duty Euro 5 and 6 regulations have been proposed for 2009 and 2014, respectively. The regulations are lass stringent than those in the US, but options exist for adopting European vehicles for the US market. Europe is just beginning to look at heavy-duty regulations for 2012 and beyond. Engines are making very impressive progress, with clean combustion strategies in active development mainly for US light-duty application. Heavy-duty research engines are more focused on traditional approaches, and will provide numerous engine/aftertreatment options for hitting the tight US 2010 regulations. NOx control is focusing on SCR (selective catalytic reduction) for diverse applications. Focus is on cold operation, durability, secondary emissions, and system optimization.

In this paper, we report the modeling of the selective catalytic reduction (SCR) of NOx using ammonia on a commercial vanadia-titania based catalyst. The model combines a steady-state two-dimensional channel model with a transient two- or three-dimensional monolith model of the whole catalytic monolith converter. The reaction mechanism includes the standard and fast SCR reactions and also the high-temperature oxidation of ammonia to model the decrease in conversion observed at higher temperatures. We used in-house experimental data spanning a wide range of inlet compositions and temperatures to validate the model. The model was found to be in excellent quantitative agreement with the experimental data.

Engine laboratory tests were conducted to assess the impact of B20 biodiesel on the performance of cordierite diesel particulate filters (DPFs). Test fuels included 20% soy based methyl ester blended into ultra low sulfur diesel fuel, and two ULSD on-road market fuels. B20 has a higher cetane number, boiling point and oxygen content than typical on-road diesel fuels. A comparative study was performed using a model year 2007 medium duty diesel truck engine. The aftertreatment system included a diesel oxidation catalyst (DOC) followed by a cordierite wall flow DPF. A laboratory-grade supplemental fuel doser was used in the exhaust stream for precise regeneration of the DPF. Tests revealed that the fuel dosing rate was higher and DOC fuel conversion efficiency was poorer for the B20 fuel during low exhaust temperature regenerations. The slip of B20 fuel past the DOC was shown to produce significantly higher exotherms in the DPF during regeneration.

This paper will review the field of diesel emission control with the intent of highlighting representative studies that illustrate the state-of-the-art. First, the author reviews general technology approaches for heavy and light duty applications. Given the emerging significance of ultrafines to health, and to emission control technologies, an overview of the significant developments in ultrafine particulate science is provided, followed by an assessment of filter technology. Regarding NOx control, SCR (selective catalytic reduction) and LNT (lean NOx traps) progress is described. Finally, system integration examples are provided. In general, progress is impressive and studies demonstrate that high-efficiency systems are within reach in all highway vehicle sectors. Engines are making impressive gains, and will increase the options for emission control.

The characterization of the thermal and vibration environment of the exhaust systems of three modern day diesel engines, with displacements ranging from 1.9 liter to 12.7 liter, was carried out to support the development of exhaust after treatment components. Tri-axial accelerometer and in pipe thermocouple measurements were recorded at several locations along the exhaust systems during vehicle acceleration and steady driving conditions up to 70 mph. The vehicles were loaded to various gross weight configurations to provide a wide range of engine load conditions. Narrow band and octave band vibration power spectral densities are presented and conclusions are drawn as to the spectral content of the exhaust vibration environment and its distribution along the exhaust system. Temperature time histories during vehicle acceleration runs are likewise presented to indicate expected peak exhaust temperatures.

A family of cordierite DPF filters were developed and studied for their efficacy for catalyzed soot filter applications. In addition to porosity and median pore size of DPF filters, breadth of pore size distribution, microstructure, and pore connectivity have a profound influence not only in filter performance (pressure drop, catalyst coatability, and filtration efficiency) but also on mechanical and physical properties. Through filter material composition development, optimum values for the %porosity, median pore diameter, and breadth of the pore size distribution for minimizing pressure drop have been identified, leading to the development of a new family of high-porosity cordierite diesel particulate filters that possess a unique combination of high filtration efficiency, high strength, and very low clean and soot-loaded pressure drop in both the catalyzed and non-catalyzed states. By controlling the microstructure, the impact of the catalyst on pressure drop has been minimized.

Wall-flow filter technology has been used for many years to remove particulate emissions from a select number of diesel engine exhaust systems. Significant implementation of diesel particulate filters will require the definition of regeneration strategies that permit the filters to be regularly and durably purged of accumulated non-volatile particulates. This paper will examine the laboratory-bench characterization of filter responses to the wide variety of input conditions to which they may be exposed in practice. The lab-bench filter characterization will be done as a function of generic independent variables such as flow rate, inlet temperature, oxygen content and soot loading. The testing will be conducted on uncatalyzed filters for this preliminary study. The characterization approach will examine such dependent variables as completeness of regeneration and maximum exotherm temperatures.

Diesel Oxidation Catalyst in conjunction with large frontal area substrates is a key element in HDV Diesel emission control systems. This paper describes and reviews tests on a set of various Diesel Oxidation Catalyst configurations (for example cell densities), all with the same catalyst coating. The Diesel Oxidation Catalyst specimens were subjected to the European Stationary Cycle (ESC), the European Transient Cycle (ETC), and the US heavy duty Federal Test Procedure (US FTP). The focus was to study relative emissions, pressure drop, and light-off performance. All tests were conducted using the same Detroit Diesel Series 60 engine operating on ultra low sulfur diesel fuel. In addition to this, the exhaust was regulated so that the backpressure on the engine, upstream of the catalyst was also the same for all catalysts.

This paper describes a study of ternary V2O5/WO3/TiO2 SCR catalysts coated on standard Celcor® and new highly porous cordierite substrates. At temperatures below 275°C, where NOx conversion is kinetically limited, high catalyst loadings are required to achieve high conversion efficiencies. In principle there are two ways to achieve high catalyst loadings: 1. On standard Celcor® substrates the washcoat thickness can be increased. 2. With new highly porous substrates a high amount of washcoat can be deposited in the walls. Various catalyst loadings varying from 120g/l to 540 g/l were washcoated on both standard Celcor® and new high porosity cordierite substrates with standard coating techniques. Simulated laboratory testing of these samples showed that high catalyst loadings improved both low temperature conversion efficiency and high temperature ammonia storage capacity and consequently increased the overall conversion efficiency.

The diesel oxidation catalyst is required to remove hydrocarbons and carbon monoxide from the diesel engine exhaust stream while minimizing the impact of all other features such as cost, space, pressure drop, weight, fuel consumption, etc. The challenge of designing a catalytic converter for a particular application then becomes to: first, understand the emissions and other performance targets and requirements for the engine; second, understand the influence each of the converter parameters has on the overall system performance and; third, optimize the system using these relationships. This paper will explore some of the considerations with respect to the second of the above challenges.

Recently, SiC has been investigated and pursued as an alternative material for diesel particulate filter (DPF) applications. SiC has acceptable physical properties such as good thermal conductivity, refractoriness, and chemical durability. Materials for DPF applications require a particular mean pore size, porosity, and permeability. In addition, these material attributes must be coupled to an appropriate thermal design so that the filter can survive the extreme temperature gradients generated during the regeneration process. In this report several approaches to making porous SiC will be discussed and performance data based on material properties and thermal design will be presented.

The control of NOx emissions is the greatest technical challenge in meeting future emission regulations for diesel engines. In this work, a modal analysis was performed for developing an engine control strategy to take advantage of fuel properties to minimize engine-out NOx emissions. This work focused on the use of EGR to reduce NOx while counteracting anticipated PM increases by using oxygenated fuels. A DaimlerChrysler OM611 CIDI engine for light-duty vehicles was controlled with a SwRI Rapid Prototyping Electronic Control System. Engine mapping consisted of sweeping parameters of greatest NOx impact, starting with OEM injection timing (including pilot injection) and EGR. The engine control strategy consisted of increased EGR and simultaneous modulation of both main and pilot injection timing to minimize NOx and PM emission indexes with constraints based on the impact of the modulation on BSFC, Smoke, Boost and BSHC.

There is currently a need for a practical solution for NOx abatement in automotive diesel engines. Technologies developed thus far suffer from inherent technical limitations. The selective catalytic reduction (SCR) of NOx under lean conditions has been proven to be successful for stationary applications. A new approach is described to efficiently remove NOx from the exhaust of a diesel engine powered vehicle and convert it to nitrogen and oxygen. The key to the approach is the development of an on board (in-situ) ammonia generating catalyst. The ammonia is then used as a reagent to react with exhaust NO over a secondary SCR catalyst downstream. The system can remove over 85% of the exhaust NO under achievable diesel engine operating conditions, while eliminating the potential for ammonia slip with a minimal system of sensors and feedback controls.

As demand for wall-flow Diesel particulate filters (DPF) increases, accurate predictions of DPF behavior, and in particular of the accumulated soot mass, under a wide range of operating conditions become important. This effort is currently hampered by a lack of a systematic knowledge of the accumulated particulate deposit microstructural properties. In this work, an experimental and theoretical study of the growth process of soot cakes in honeycomb ceramic filters is presented. Particular features of the present work are the application of first- principles measurement and simulation methodology for accurate determination of soot cake packing density and permeability, and their systematic dependence on the filter operating conditions represented by the Peclet number for mass transfer. The proposed measurement methodology has been also validated using various filters on different Diesel engines.

The present work intends to examine the selective NOx reduction efficiency of a current commercial Titanium-Vanadium washcoated catalyst and to develop a transient numerical model capable of describing the SCR process while using a wide range of inlet conditions such as space velocity, oxygen concentrations, water concentration and NO2/NO ratio. The concentrations of different components (NO, NO2, N2O, NH3, H2O and HNO3) were analyzed continuously by a FT-IR spectrometer. A temperature range from 150°C up to 650°C was examined and tests were carried out using a model exhaust gas comparable to the real diesel exhaust gas composition. There is a very good correlation between experimental and calculated results with the given chemical kinetics.