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An advanced exhaust aftertreatment system is characterized following end-of-life catalyst aging to meet final Tier 4 off-highway emission requirements. This system consists of a fuel dosing system, mixing elements, fuel reformer, lean NOx trap (LNT), diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst. The fuel reformer is used to generate hydrogen (H2) and carbon monoxide (CO) from injected diesel fuel. These reductants are used to regenerate and desulfate the LNT catalyst. NOx emissions are reduced using the combination of the LNT and SCR catalysts. During LNT regeneration, ammonia (NH3) is intentionally released from the LNT and stored on the downstream SCR catalyst to further reduce NOx that passed through the LNT catalyst. This paper addresses system durability as the catalysts were aged to 500 desulfation events using an off-highway diesel engine.

Diesel exhaust aftertreatment systems are required for meeting both EPA 2010 and final Tier 4 emission regulations. This paper addresses aftertreatment system performance of a fuel reformer, lean NOx trap (LNT) and selective catalytic reduction (SCR) system designed to meet the EPA 2010 emission standards for an on-highway heavy-duty vehicle. The aftertreatment system consists of a fuel dosing system, mixing elements, fuel reformer, LNT, diesel particulate filter (DPF), and SCR for meeting NOx and particulate emissions. System performance was characterized in an engine dynamometer test cell, using a development, 13L, heavy-duty engine. The catalyst performance was evaluated using degreened catalysts. Test results show that system performance met the EPA 2010 emission standards under a range of test conditions that were reflective of actual vehicle operation.

An LNT + SCR diesel aftertreatment system was developed in order to meet the 2010 US HD EPA on-road, and tier 4 US HD EPA off-road emission standards. This system consists of a fuel reformer (REF), lean NOx trap (LNT), catalyzed diesel particulate filter (DPF), and selective catalytic reduction (SCR) catalyst arranged in series to reduce tailpipe nitrogen oxides (NOx) and particulate matter (PM). This system utilizes a REF to produce hydrogen (H2), carbon monoxide (CO) and heat to regenerate the LNT, desulfate the LNT, and actively regenerate the DPF. The NOx stored on the LNT is reduced by the H2 and CO generated in the REF converting it to nitrogen (N2) and ammonia (NH3). NH3, which is normally an undesired byproduct of LNT regeneration, is stored in the downstream SCR which is utilized to further reduce NOx that passes through the LNT. Engine exhaust PM is filtered and trapped by the DPF reducing the tailpipe PM emissions.

The paper covers the NOx performance evaluation of an LNT + SCR system designed to meet the 2010 on-highway heavy-duty (HD) US EPA emission standards. The system combines a fuel reformer catalyst (REF), lean NOx trap (LNT), diesel particulate filter (DPF), and selective catalytic reduction (SCR) in series, to reduce engine-out NOx and PM. System NOx reduction performance was verified in an engine dynamometer test cell, using a 2007 7.6L medium-duty engine. System NOx performance was characterized using fresh LNT and SCR along with hydrothermal aged LNT and fresh SCR. Test results show levels consistent with EPA 2010 limits under various test conditions. Catalysts performance was characterized at eight steady engine-operating conditions (A100, B50, B75, A75, B100, C100, C75, C50, across a 13-mode Supplemental Emission Test (SET), and an on-highway Heavy Duty Federal Test Procedure (HD-FTP).

The firing frequency components of the dynamic diesel particulate filter pressure signals carry significant information about the particulate load. Specifically, the normalized magnitude and relative phase of the firing frequency components exhibit clear dependence on the particulate load in a filter. Further, the test-to-test variation and back-to-back repeatability in this work was better for the dynamic pressure signal features than for the mean value pressure drop. This work provides a promising extension or alternative to the mean value pressure drop correlation to particulate load through Darcy's Law. The results may be particularly useful for filter monitoring and control.

A fast time-scale 1-D dynamic diesel particulate filter model capable of resolving the pressure pulsations due to individual cylinder firing events is presented. The purpose of this model is to investigate changes in the firing frequency component of the pulsating exhaust flow at different particulate loadings. Experimental validation data and simulation results clearly show that the magnitude and phase of the firing frequency components are directly correlated to the mass of particulate stored in a diesel particulate filter. This dynamic pressure signal information may prove particularly useful for monitoring particulate load during vehicle operation.

An advanced exhaust aftertreatment system is being developed using a fuel dosing system, mixing elements, fuel reformer, lean NOx trap (LNT), diesel particulate filter (DPF) and a selective catalytic reduction (SCR) catalyst arranged in series for both on- and off- highway diesel engines to meet the upcoming emissions regulations. This system utilizes a fuel reformer to generate hydrogen (H2) and carbon monoxide (CO) from injected diesel fuel. These reductants are used to regenerate and desulfate the LNT catalyst. NOx emissions are reduced using the combination of the LNT and SCR catalysts. During LNT regeneration, ammonia is intentionally released from the LNT and stored on the downstream SCR catalyst to further reduce NOx that passed through the LNT catalyst. This paper addresses LNT and SCR catalyst degradation as these were subjected to 150 desulfation events using a pre-production 2007 medium heavy-duty, on-highway diesel engine.

This paper addresses Hardware-In-the-Loop modeling and simulation for Diesel aftertreatment controls system development. Lean NOx Trap (LNT) based aftertreatment system is an efficient way to reduce NOx emission from diesel engines. From control system perspective, the main challenge in aftertreatment system is to predict temperature at various locations and estimate the stored NOx in LNT. Accurate estimation of temperatures and NOx stored in the LNT will result in an efficient system control with less fuel penalty while still maintaining the emission requirements. The optimization of the controls will prolong the lifespan of the system by avoiding overheating the catalysts, and slow the progressive process of component aging. Under real world conditions, it is quite difficult and costly to test the performance of a such complex controller by using only vehicle tests and engine cells.

The diesel particulate filter (DPF), in conjunction with fuel reformulation technologies such as ultralow sulfur fuel or Fischer-Tropsch diesel, represents a promising solution for reducing particulate emissions. In this work, membrane-coated and conventional uncoated SiC diesel particulate filters were tested on a 4-cylinder Volkswagen TDI diesel engine under four different engine load conditions at constant engine speed. Di-tert-butyl-sulfide was added to the base fuel to increase the sulfur content from 39 ppm to approximately 300 PPM. Gaseous and particulate mass emission measurements, as well as, PM morphology and composition have been used to address how engine-out and post-DPF emissions and post-oxidation catalyst emissions change with increasing fuel sulfur content. The influence of fuel sulfur on emissions was compared for the membrane coated and uncoated SiC filter using the same diesel oxidation catalyst (DOC) located downstream of the DPF.

The 2002 Pennsylvania State University FutureTruck Team has converted a stock 2002 Ford Explorer sport utility vehicle into a post-transmission, pre-transfer case parallel hybrid electric vehicle, dubbed the Wattmuncher. The stock 4.0L, V-6 spark ignition engine was replaced with a more efficient 2.5L direct-injection, common-rail, turbocharged diesel engine that meets Euro 3 emission standards. A diesel particulate filter was implemented for additional emission reductions. ADVISOR simulation results predict 23.5 mpg city and 31.9 mpg highway fuel economy while maintaining stock acceleration and towing capacity. The vehicle was designed for manufacturability, and a complete cost analysis for mass production results in an expected $4,050 added cost for this hybridized Explorer.

Diesel exhaust aftertreatment systems are required for meeting Final Tier 4 emission regulations. This paper addresses an aftertreatment system designed to meet the Final Tier 4 emission standards for nonroad vehicle markets. The aftertreatment system consists of a fuel dosing system, mixing elements, fuel vaporizer, fuel reformer, lean NOx trap (LNT), diesel particulate filter (DPF), and an optional selective catalytic reduction (SCR) catalyst. Aftertreatment system performance, both with and without the SCR, was characterized in an engine dynamometer test cell, using a 4.5 liter, pre-production diesel engine. The engine out NOx nominally ranged between 1.6 and 2.0 g/kW-hr while all operating modes ranged between 1.2 and 2.8 g/kW-hr. The engine out particulate matter was calibrated to approximately 0.1 g/kW-hr for various power ratings. Three engine power ratings of 104 kW, 85 kW and 78 kW were evaluated.

Diesel engine cylinder deactivation (CDA) can be used to reduce petroleum consumption and greenhouse gas (GHG) emissions of the global freight transportation system. Heavy duty trucks require complex exhaust aftertreatment (A/T) in order to meet stringent emission regulations. Efficient reduction of engine-out emissions require a certain A/T system temperature range, which is achieved by thermal management via control of engine exhaust flow and temperature. Fuel efficient thermal management is a significant challenge, particularly during cold start, extended idle, urban driving, and vehicle operation in cold ambient conditions. CDA results in airflow reductions at low loads. Airflow reductions generally result in higher exhaust gas temperatures and lower exhaust flow rates, which are beneficial for maintaining already elevated component temperatures. Airflow reductions also reduce pumping work, which improves fuel efficiency.

The latest US emission regulations require dramatic reductions in Nitrogen Oxide (NOx) emissions from vehicular diesel engines. Selective Catalytic Reduction (SCR) is the current technology that achieves NOx reductions of up to 90%. It is typically mounted downstream of the existing after-treatment system, i.e., after the Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). Accurate prediction of input NO₂:NO ratio is useful for control of SCR urea injection to reduce NOx output and NH₃ slippage downstream of the SCR catalyst. Most oxidation of NO to NO₂ occurs in the DOC since its main function is to oxidize emission constituents. The DOC thus determines the NO₂:NO ratio as feedgas to the SCR catalyst. The prediction of NO₂:NO ratio varies as the catalyst in the DOC ages or deteriorates due to poisoning. Thus, the DOC prediction model has to take into account the correlation of DOC conversion effectiveness and the aging of the catalyst.

A gravimetric particulate measurement system, which extracts samples isokinetically from raw exhaust, is presented to quantify the particulate mass stored in diesel particulate filters. The purpose of this measurement system is to facilitate the study of wall-flow filter behavior at different particulate load levels. Within this paper, the design considerations for the particulate measurement system are detailed and its operation is described. The accuracy of the measurement is examined through a theoretical error analysis and direct experimental comparison to the differential weight of a diesel particulate filter. Experimental results are also presented to validate the ability of the system to maintain the isokinetic sampling condition.