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To meet increasingly stringent diesel engine emission regulations, diesel engines are required to use ultra-low sulfur diesel (ULSD) and are equipped with advanced aftertreatment systems. Cu-SSZ-13 zeolite catalysts are widely used as selective catalytic reduction (SCR) catalysts due to their high NOx reduction and excellent hydrothermal stability. However, active Cu sites of Cu-SSZ-13 catalysts can be poisoned by exposure to engine exhaust sulfur species. This poison effect can be mitigated with the use of ULSD and high temperature exposure from engine operation. On the other hand, ULSD is still not universally available where regulations require it, and vehicles may inadvertently operate with high sulfur diesel fuel (HSD) in some locations. The high concentration of exhaust sulfur species resulting from HSD combustion may rapidly poison the Cu-SSZ-13 SCR catalyst. In this study, the catalytic performance of a sulfur poisoned Cu-SSZ-13 SCR catalyst is analyzed.

This oil category was driven by two new cooled exhaust gas recirculation (EGR) engine tests operating with 15% EGR, with used oil soot levels at the end of the test ranging from 6 to 9%. These tests are the Mack T-10 and Cummins M11 EGR, which address ring, cylinder liner, bearing, and valve train wear; filter plugging, and sludge. In addition to these two new EGR tests, there is a Caterpillar single-cylinder test without EGR which measures piston deposits and oil consumption control using an articulated piston. This test is called the Caterpillar 1R and is included in the existing Global DHD-1 specification. In total, the API CI-4 category includes eight fired-engine tests and seven bench tests covering all the engine oil parameters. The new bench tests include a seal compatibility test for fresh oils and a low temperature pumpability test for used oils containing 5% soot. This paper provides a review of the all the tests, matrix results, and limits for this new oil category.

Future light duty vehicles in the United States are required to be certified on the FTP-75 cycle to meet Tier 3 or LEV III emission standards [1, 2]. The cold phase of this cycle is heavily weighted and mitigation of emissions during this phase is crucial to meet the low tail pipe emission targets [3, 4]. In this work, a novel aftertreatment architecture and controls to improve Nitrogen Oxides (NOx) and Hydrocarbon (HC) or Non Methane Organic gases (NMOG) conversion efficiencies at low temperatures is proposed. This includes a passive NOx & HC adsorber, termed the diesel Cold Start Concept (dCSC™) catalyst, followed by a Selective Catalytic Reduction catalyst on Filter (SCRF®) and an under-floor Selective Catalytic Reduction catalyst (SCR). The system utilizes a gaseous ammonia delivery system capable of dosing at two locations to maximize NOx conversion and minimize parasitic ammonia oxidation and ammonia slip.

In this study, the formation and decomposition of ammonium nitrate (AN) on a state-of-the-art extruded vanadium-based SCR catalyst (V-SCR) under simulated exhaust conditions has been evaluated. Results show that AN readily forms and accumulates at temperatures below 200°C when exposed to NH3 and NO2. The rate of AN accumulation increases with decreasing temperature. A new low temperature NH3 release peak (not present following NH3 storage conditions with NH3 only) becomes apparent after AN accumulation at 100 and 125°C. This new NH3 release, with a peak release temperature of approximately 180°C, is evaluated in detail to better determine its origin. BET surface area, and thermal gravimetric analysis/differential scanning calorimetry (TGA/DSC), and reactor-based experiments are all used to characterize AN formed on the V-SCR catalyst in comparison to pure AN.

Diesel emission aftertreatment system is usually designed to meet stringent packaging constraints, rendering a difficult situation to achieve perfect flow distribution inside the catalytic unit. The non-uniform flow pattern leads to a mal-distribution of flow velocity, temperature, and gas species in catalyst unit. Some catalysts are exposed to harsh working environment, while the rest catalysts are underutilized. This lowers the efficiency of overall catalyst unit and thus requires an oversized system to meet emission requirements. The flow mal-distribution also accelerates the uneven catalyst degradation, lowering the system durability. Hence, a quantitative description of packaging impact on catalyst performance is critical to assess the system efficiency and durability. In the present work, a mapping method is developed to combine catalyst performance with computational fluid dynamics (CFD) simulation.

Accurate estimation of catalyst bed temperatures is very crucial for effective control and diagnostics of aftertreatment systems. The architecture of most aftertreatment systems contains temperature sensors for measuring the exhaust gas temperatures at the inlet and outlet of the aftertreatment systems. However, the temperature that correctly reflects the temperature of the chemical reactions taking place on the catalyst surface is the catalyst bed temperature. From the Arrhenius relationship which governs the chemical reaction kinetics occurring in different aftertreatment systems, the rate of chemical reaction is very sensitive to the reaction temperature. Considerable changes in tailpipe emissions can result from small changes in the reaction temperature and robust emissions control systems should be able to compensate for these changes in reaction temperature to achieve the desired tailpipe emissions.

Measuring axial exhaust species concentration distributions within a wall-flow aftertreatment device provides unique and significant insights regarding the performance of complex devices like the SCR-on-filter. In this particular study, a less complex aftertreatment configuration which includes a DOC followed by two uncoated partial flow filters (PFF) was used to demonstrate the potential and challenges. The PFF design in this study was a particulate filter with alternating open and plugged channels. A SpaciMS [1] instrument was used to measure the axial NO2 profiles within adjacent open and plugged channels of each filter element during an extended passive regeneration event using a full-scale engine and catalyst system. By estimating the mass flow through the open and plugged channels, the axial soot load profile history could be assessed.

The majority of commercial diesel engines rely on EGR to meet increasingly stringent emissions standards, creating a potential issue for military applications that use JP-8 as a fuel. EGR components would be susceptible to corrosion from sulfur in JP-8, which can reach levels of 3000 ppm. Starting with a Cummins 2007 ISL 8.9L production engine, modifications to remove EGR and operate on JP-8 fuel are investigated with a key goal of demonstrating 48% brake thermal efficiency (BTE) at an emissions level consistent with 1998 EPA standards. The effects of injector cup flow, improved turbo match, increased compression ratio with revised piston bowl geometry, increased cylinder pressure, and revised intake manifold for improved breathing, are all investigated. Testing focused on a single operating point, full load at 1600 RPM. This engine uses a variable geometry turbo and high pressure common rail fuel system, allowing control over air fuel ratio, rail pressure, and start of injection.

Advanced emission control systems for diesel engines usually include a combination of Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), Selective Catalytic Reduction (SCR), and Ammonia Slip Catalyst (ASC). The performance of these catalysts individually, and of the aftertreatment system overall, is negatively affected by the presence of oxides of sulfur, originating from fuel and lubricant. In this paper, we illustrated some key aspects of sulfur interactions with the most commonly used types of catalysts in advanced aftertreatment systems. In particular, DOC can oxidize SO2 to SO3, collectively referred to as SOx, and store these sulfur containing species. The key functions of a DOC, such as the ability to oxidize NO and HC, are degraded upon SOx poisoning. The impact of sulfur poisoning on the catalytic functions of a DPF is qualitatively similar to DOC.

Government agencies like EPA play an important role through regulation to reduce emissions and fuel consumption and to drive technological developments to reduce the environmental impact of burning petroleum fuels. Emissions testing and control is one of the leading and growing fields in the development of modern vehicles. Recently, Cummins Emissions Solutions (CES) and Southwest Research Institute (SwRI) worked jointly in order to achieve a method to conduct emissions testing efficiently and effectively. The collaborative work between the two organizations led to the usage of FOCAS HGTR™ (a diesel-based burner test rig at SwRI) to simulate the exhaust conditions generated by a 2010 ISX Cummins production engine operating over an EPA standard Ramped Modal Cycle Supplemental Emissions Test (RMC SET) cycle.

The oxidation of short-chain alkanes, such as methane, ethane, and propane, from the exhaust of lean-burn natural gas and lean-burn dual-fuel (natural gas and diesel) engines poses a unique challenge to the exhaust aftertreatment community. Emissions of these species are currently regulated by the US Environmental Protection Agency (EPA) as either methane (Greenhouse Gas Emissions Standards) or non-methane hydrocarbon (NMHC). However, the complete catalytic oxidation of short-chain alkanes is challenging due to their thermodynamic stability. The present study focuses on the oxidation of short-chain alkanes by vanadium-based and Cu/zeolite selective catalytic reduction (SCR) catalysts, generally utilized to control NOx emissions from lean-burn engines. Results reveal that these catalysts are active for short-chain alkane oxidation, albeit, at conversions lower than those generally reported in the literature for Pd-based catalysts, typically used for short-chain alkane conversion.

Oxidation of NO to NO₂ over a Diesel Oxidation Catalyst (DOC) plays an important role in different types of aftertreatment systems, by enhancing NOx storage on adsorber catalysts, improving the NOx reduction efficiency of SCR catalysts, and enabling the passive regeneration of Diesel Particulate Filters (DPF). The presence of hydrocarbon (HC) species in the exhaust is known to affect the NO oxidation performance over a DOC; however, specific details of this effect, including its underlying mechanism, remain poorly understood. Two major pathways are commonly considered to be responsible for the overall effect: NO oxidation inhibition, due to the presence of HC, and the consumption of the NO₂ produced by reaction with hydrocarbons. In this work we have attempted to decouple these two pathways, by adjusting the catalyst inlet concentrations of NO and NO₂ to the thermodynamic equilibrium levels and measuring the composition changes over the catalyst in the presence of HC species.

Lean-burn natural gas (NG) engines are used world-wide for both stationary power generation and mobile applications ranging from passenger cars to Class 8 line-haul trucks. With the recent introduction of hydraulic fracturing gas extraction technology and increasing availability of natural gas, these engines are receiving more attention. However, the reduction of unburned hydrocarbon emissions from lean-burn NG and dual-fuel (diesel and natural gas) engines is particularly challenging due to the stability of the predominant short-chain alkane species released (e.g., methane, ethane, and propane). Supported Pd-based oxidation catalysts are generally considered the most active materials for the complete oxidation of low molecular weight alkanes at temperatures typical of lean-burn NG exhaust. However, these catalysts rapidly degrade under realistic exhaust conditions with high water vapor concentrations and traces of sulfur.

The modern diesel engine is used around the world to power applications as diverse as passenger cars, heavy-duty trucks, electrical power generators, ships, locomotives, agricultural and industrial equipment. The success of the diesel engine results from its unique combination of fuel economy, durability, reliability and affordability - which drive the lowest total cost of ownership. The diesel engine has been developed to meet the most demanding on-highway emission standards, through the introduction of advanced technologies such as: electronic controls, high pressure fuel injection, and cooled exhaust gas recirculation. The standards to be introduced in the U.S. in 2007 will see the introduction of the Clean Diesel which will achieve near-zero NOx and particulate emissions, while retaining the customer values outlined above.

Range-extended hybrids are an attractive option for medium- and heavy-duty commercial vehicle fleets because they offer the efficiency of an electrified powertrain with the driving range of a conventional diesel powertrain. The vehicle essentially operates as if it was purely electric for most trips, while ensuring that all commercial routes can be completed in any weather conditions or geographic terrain. Fuel use and point-source emissions can be significantly reduced, and in some cases eliminated, as many shorter routes can be fully electrified with this architecture. Under a U.S. Department of Energy (DOE)-funded project for Medium- and Heavy-Duty Vehicle Powertrain Electrification, Cummins has developed a plug-in hybrid electric Class 6 truck with a range-extending engine designed for pickup and delivery application.

A heavy-duty compression ignition engine using EGR and pilot-ignited directly injected natural gas fueling was calibrated for low NOx emissions. A Cummins ISX engine using cooled EGR was fitted with a Westport HPDI™ fuel system and an oxidation catalyst. The base engine hardware was modified to increase EGR rates (up to 40%). The engine, rated at 336 kW (450 hp) and 2236Nm (1650 ft-lbs), was calibrated and tested over steady state and transient test cycles. Steady state testing over the ESC 13-mode test cycle resulted in weighted composite NOx emissions of 0.36 g/bhp-hr and particulate matter emissions of 0.04 g/bhp-hr. Transient testing over the US EPA specified FTP cycle resulted in average NOx emissions of 0.6 g/bhp-hr and PM emissions of 0.03 g/bhp-hr.

Commercial Cu-Zeolite SCR catalyst can store and subsequently release significant amount of H2O. The process is accompanied by large heat effects. It is critical to model this phenomenon to design aftertreatment systems and to provide robust tuning strategies to meet cold start emissions and low temperature operation. The complex reaction mechanism of water adsorption and desorption over a Cu-exchanged SAPO-34 catalyst at low temperature was studied through steady state and transient experiments. Steady state isotherms were generated using a gravimetric method and then utilized to predict water storage interactions with respect to feed concentration and catalyst temperature. Transient temperature programmed desorption (TPD) experiments provided the kinetic information required to develop a global kinetic model from the experimental data. The model captures fundamental characteristics of water adsorption and desorption accompanied by the heat effects.

Natural gas powered vehicles are attractive in certain applications due to their lower emissions in general than conventional diesel engines and the low cost of natural gas. For stoichiometric natural gas engines, the aftertreatment system typically consists only of a three-way catalyst (TWC). However, increasingly stringent NOx and methane regulations challenge current TWC technologies. In this work, a catalyst reactor system with variable lean/rich switching capability was developed for evaluating TWCs for stoichiometric natural gas engines. The effect of varying frequency and duty-cycle during lean/rich gas switching experiments was measured with a hot-wire anemometer (HWA) due to its high sensitivity to gas thermal properties. A theoretical reactor gas dispersion model was then developed and validated with the HWA measurements. The model is capable of predicting the actual lean/rich gas exposure to the TWC under different testing conditions.

SCR on Filter (SCRoF) is an efficient and compact NOX and PM reduction technology already used in series production for light-duty applications. The technology is now finding its way into the medium duty and heavy duty market. One of the key challenges for successful application is the robustness to real world variations. The solution to this challenge can be found by using model-based control algorithms, utilizing state estimation by physics-based catalyst models. This paper focuses on the development, validation and real time implementation of a physics-based control oriented SCRoF model. An overview of the developed model will be presented, together with a brief description of the model parameter identification and validation process using engine test bench measurement data. The model parameters are identified following a streamlined approach, focusing on decoupling the effects of deNOx and soot phenomena.

Three-way catalysts have been used in a variety of stoichiometric natural gas engines for emission control. During real-world operation, these catalysts have experienced a large number of temporary and permanent deactivations including thermal aging and chemical contamination. Thermal aging is typically induced either by high engine-out exhaust temperatures or the reaction exotherm generated on the catalysts. Chemical contamination originates from various inorganic species such as Phosphorous (P) and Sulfur (S) that contain in engine fluids, which can poison and/or mask the catalyst active components. Such deactivations are quite difficult to simulate under laboratory conditions, due to the fact that multiple deactivation modes may occur at the same time in the real-world operations. In this work, a set of field-aged TWCs has been analyzed through detailed laboratory research in order to identify and quantify the real-world aging mechanisms.