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Journal Article

Why Cu- and Fe-Zeolite SCR Catalysts Behave Differently At Low Temperatures

2010-04-12
2010-01-1182
Cu- and Fe-zeolite SCR catalysts emerged in recent years as the primary candidates for meeting the increasingly stringent lean exhaust emission regulations, due to their outstanding activity and durability characteristics. It is commonly known that Cu-zeolite catalysts possess superior activity to Fe-zeolites, in particular at low temperatures and sub-optimal NO₂/NOx ratios. In this work, we elucidate some underlying mechanistic differences between these two classes of catalysts, first based on their NO oxidation abilities, and then based on the relative properties of the two types of exchanged metal sites. Finally, by using the ammonia coverage-dependent NOx performance, we illustrate that state-of-the-art Fe-zeolites can perform better under certain transient conditions than in steady-state.
Journal Article

Powertrain Cycle for Emission Certification

2012-09-24
2012-01-2059
In August of 2011, the US Environmental Protection Agency issued new Green House Gas (GHG) emissions regulations for heavy duty vehicles. These regulations included new procedures for the evaluation of hybrid powertrains and vehicles. One of the hybrid options allows for the evaluation of an engine plus a hybrid transmission (a powertrain). For this type of testing, EPA has proposed simulating a vehicle following the hybrid vehicle test procedures, including the use of the vehicle cycles and the A to B comparison testing - as required for the full vehicle evaluation option. This paper proposes an alternative approach by defining a powertrain cycle. The powertrain cycle is based on the heavy duty engine emissions cycle - the transient FTP cycle. Simulation and test results are presented showing similar performance over the engine and vehicle cycles. This approach offers several advantages as compared to the procedure described in EPA's GHG rule.
Technical Paper

Particulate Characteristics for Varying Engine Operation in a Gasoline Spark Ignited, Direct Injection Engine

2011-04-12
2011-01-1220
The objective of this research is a detailed investigation of particulate sizing and number count from a spark-ignited, direct-injection (SIDI) engine at different operating conditions. The engine is a 549 [cc] single-cylinder, four-valve engine with a flat-top piston, fueled by Tier II EEE. A baseline engine operating condition, with a low number of particulates, was established and repeatability at this condition was ascertained. This baseline condition is specified as 2000 rpm, 320 kPa IMEP, 280 [°bTDC] end of injection (EOI), and 25 [°bTDC] ignition timing. The particle size distributions were recorded for particle sizes between 7 and 289 [nm]. The baseline particle size distribution was relatively flat, around 1E6 [dN/dlogDp], for particle diameters between 7 and 100 [nm], before dropping off to decreasing numbers at larger diameters. Distributions resulting from a matrix of different engine conditions were recorded.
Journal Article

Characteristics of Ion Current Signals in Compression Ignition and Spark Ignition Engines

2010-04-12
2010-01-0567
Ion current sensors have been considered for the feedback electronic control of gasoline and diesel engines and for onboard vehicles powered by both engines, while operating on their conventional cycles or on the HCCI mode. The characteristics of the ion current signal depend on the progression of the combustion process and the properties of the combustion products in each engine. There are large differences in the properties of the combustible mixture, ignition process and combustion in both engines, when they operate on their conventional cycles. In SI engines, the charge is homogeneous with an equivalence ratio close to unity, ignition is initiated by an electric spark and combustion is through a flame propagating from the spark plug into the rest of the charge.
Technical Paper

Axial NO2 Utilization Measurements within a Partial Flow Filter during Passive Regeneration

2017-03-28
2017-01-0988
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.
Technical Paper

Future Challenges for Engine Manufacturers in View of Future Emissions Legislation

2017-05-10
2017-01-1923
Countries around the world are expected to continue to adopt more stringent emissions standards for heavy-duty markets for both oxides of nitrogen (NOx) and greenhouse gases (GHG). While there is uncertainty about the timing and extent of these regulations, it is clear that significant reductions will be required to address urban air pollution and climate change concerns. The rate and pace of technology evolution and how it will affect the energy pathways for commercial transportation and industrial use are dependent on multiple variables such as national energy and environmental policies and public-private partnerships. Although it adds complexity, the engine system has great potential to evolve as it continues to be highly integrated into the super system for which it is producing power. This paper examines the potential opportunities and challenges for engine manufacturers to continue to be the supplier of power to vehicles and equipment of the future.
Technical Paper

Reactor System with Diesel Injection Capability for DOC Evaluations

2018-04-03
2018-01-0647
Plug flow reactors, simulating engine exhaust gas, are widely used in emissions control research to gain insight into the reaction mechanisms and engineering aspects that controls activity, selectivity, and durability of catalyst components. The choice of relevant hydrocarbon (HC) species is one of the most challenging factor in such laboratory studies, given the variety of compositions that can be encountered in different application scenarios. Furthermore, this challenge is amplified by the experimental difficulties related to introducing heavier and multi-component HCs and analyzing the reaction products.
Technical Paper

The Role of Second Phase Hard Particles on Hole Stretchability of Two AA6xxx Alloys

2017-03-28
2017-01-0307
The hole stretchability of two Aluminum Alloys (AA6111 and AA6022) are studied by using a two stages integrated finite element framework where the edge geometry and edge damages from the hole piercing processes were considered in the subsequent hole expansion processes. Experimentally it has been found that AA6022 has higher hole expansion ratios than those of AA6111. This observation has been nicely captured by finite element simulations. The main cause of differences have been identified to the volume fractions of the random distributed second phase hard particles which play a critical role in determining the fracture strains of the materials.
Technical Paper

Phenomenological Investigations of Mid-Channel Ash Deposit Formation and Characteristics in Diesel Particulate Filters

2019-04-02
2019-01-0973
Accumulation of lubricant and fuel derived ash in the diesel particulate filter (DPF) during vehicle operation results in a significant increase of pressure drop across the after-treatment system leading to loss of fuel economy and reduced soot storage capacity over time. Under certain operating conditions, the accumulated ash and/or soot cake layer can collapse resulting in ash deposits upstream from the typical ash plug section, henceforth termed mid-channel ash deposits. In addition, ash particles can bond (either physically or chemically) with neighboring particles resulting in formation of bridges across the channels that effectively block access to the remainder of the channel for the incoming exhaust gas stream. This phenomenon creates serious long-term durability issues for the DPF, which often must be replaced. Mid-channel deposits and ash bridges are extremely difficult to remove from the channels as they often sinter to the substrate.
Technical Paper

Modeling of Friction Stir Welding (FSW) Process with Smooth Particle Hydrodynamics (SPH)

2006-04-03
2006-01-1394
Since its invention fifteen years ago, Friction Stir Welding (FSW) has found commercial applications in marine, aerospace, rail, and now automotive industries. Development of the FSW process for each new application, however, has remained largely empirical. Few detailed numerical modeling techniques have been developed that can explain and predict important features of the process physics. This is particularly true in the areas of material flow, mixing mechanisms, and void prediction. In this paper we present a novel modeling approach to simulate FSW processes that may have significant advantages over current traditional finite element or finite difference based methods. The proposed model is based on the Smoothed Particle Hydrodynamics (SPH) method.
Technical Paper

A Feasibility Evaluation of a Thermal Plasma Fuel Reformer for Supplemental Hydrogen Addition to Internal Combustion Engines

1999-04-26
1999-01-2239
One scenario for reducing engine out NOx in a spark ignition engine is to introduce small amounts of supplemental hydrogen to the combustion process. The supplemental hydrogen enables a gasoline engine to run lean where NOx emissions are significantly reduced and engine efficiency is increased relative to stoichiometric operation. This paper reports on a mass and energy balance model that has been developed to evaluate the overall system efficiencies of a thermal reformer-heat exchanger system capable of delivering hydrogen to the air intake of a gasoline engine. The mass and energy balance model is utilized to evaluate the conditions where energy losses associated with fuel reformation may be offset by increases in engine efficiencies.
Technical Paper

Exhaust Aftertreatment Research for Heavy Vehicles

2001-05-14
2001-01-2064
The Office of Heavy Vehicle Technologies supports research to enable high-efficiency diesel engines to meet future emissions regulations, thus clearing the way for their use in light trucks as well as continuing as the most efficient powerplant for freight-haulers. Compliance with Tier 2 emission regulations for light-duty vehicles will require effective exhaust emission controls (aftertreatment) for diesels in these applications. Diesel-powered heavy trucks face a similar situation for the 2007 regulations announced by EPA in December 2000. DOE laboratories are working with industry to improve emission control technologies in projects ranging from application of new diagnostics for elucidating key mechanisms, to development and evaluation of prototype devices. This paper provides an overview of these R&D efforts, with examples of key findings and developments.
Technical Paper

An Emission and Performance Comparison of the Natural Gas Cummins Westport Inc. C-Gas Plus Versus Diesel in Heavy-Duty Trucks

2002-10-21
2002-01-2737
Cummins Westport Inc. (CWI) released for production the latest version of its C8.3G natural gas engine, the C Gas Plus, in July 2001. This engine has increased ratings for horsepower and torque, a full-authority engine controller, wide tolerance to natural gas fuel (the minimum methane number is 65), and improved diagnostics capability. The C Gas Plus also meets the California Air Resources Board optional low-NOx (2.0 g/bhp-h) emission standard for automotive and urban buses. Two pre-production C Gas Plus engines were operated in a Viking Freight fleet for 12 months as part of the U.S. Department of Energy's Fuels Utilization Program. In-use exhaust emissions, fuel economy, and fuel cost were collected and compared with similar 1997 Cummins C8.3 diesel tractors. CWI and the West Virginia University developed an ad-hoc test cycle to simulate the Viking Freight fleet duty cycle from in-service data collected with data loggers.
Technical Paper

Plasma-Enhanced Catalytic Reduction of NOx in Simulated Lean Exhaust

2000-10-16
2000-01-2961
NOx reduction efficiency in simulated lean exhaust conditions has been examined for three proprietary catalyst materials using a non-thermal plasma discharge as a pretreatment stage to the catalyst. Using propene as the reducing agent for selective catalytic reduction, 74% reduction of NOx has been observed in the presence of 20 ppm SO2. For sulfur-free simulated exhaust, 84% NOx reduction has been obtained. Results show that the impact of sulfur on the samples examined can vary widely from virtually no effect (< 5%) to more than 20% loss in activity depending on the catalyst. Any loss due to sulfur poisoning appears to be irreversible according to limited measurements on poisoned catalysts exposed to sulfur-free exhaust streams. Catalysts were tested over a temperature range of 473-773K, with the highest activity observed at 773K. Examination of this large temperature window has shown that the optimum C1:NOx ratio changes with temperature.
Technical Paper

Effect of Simulated Diesel Exhaust Gas Composition and Temperature on NOx Reduction Behavior of Alumina and Zeolite Catalysts in Combination With Non-Thermal Plasma

2000-10-16
2000-01-2964
NOx reduction under simulated lean burn conditions was studied using a non-thermal plasma in combination with zeolite and alumina catalysts. The influence of temperature and plasma treatment on the catalytic performance was investigated. Zeolite catalyst B showed high activity in the 150-300°C temperature region. Alumina Catalyst D was most active at temperatures higher than 250°C. In addition, the alumina catalyst was effective in oxidation of aldehydes formed during plasma treatment of the reaction mixture. When the reaction was carried out over a catalyst bed consisting of separate layers of the zeolite and alumina catalysts, the catalyst temperature range for significant NOx reduction was expanded to 150-500°C.
Technical Paper

Effect of Windshield Design on High Speed Impact Resistance

2000-10-03
2000-01-2723
An axisymmetric finite element model is generated to simulate the windshield glass damage propagation subjected to impact loading of a flying object. The windshield glass consists of two glass outer layers laminated by a thin poly-vinyl butyral (PVB) layer. The constitutive behavior of the glass layers is simulated using brittle damage mechanics model with linear damage evolution. The PVB layer is modeled with linear viscoelastic solid. The model is used to predict and examine through-thickness damage evolution patterns on different glass surfaces and cracking patterns for different windshield designs such as variations in thickness and curvatures.
Technical Paper

Evaluation of Corona Reactors of Several Geometries for a Plasma Assisted Nitrogen Oxide Emission Reduction Device

2000-10-16
2000-01-2899
Proposed vehicle emissions regulations for the near future have prompted automotive manufactures and component suppliers to focus heavily on developing more efficient exhaust aftertreatment devices to lower emissions from spark and compression ignition engines. One of the primary pollutants from lean-burn engines, especially from diesels, are oxides of nitrogen (NOx). Current three-way catalytic converters will not have adequate performance to meet future emission reduction requirements. Therefore, there is a need for researchers and engineers to develop efficient exhaust aftertreatment devices that will reduce NOx emissions from lean-burn engines. These devices must have very high conversion of NOx gases, be unaffected by exhaust-gas impurity such as sulfur, and have minimal impact on vehicle operations and fuel economy. An effective technology for NOx control that is currently receiving a lot of attention is a non-thermal plasma system.
Technical Paper

Lean NOx Reduction in Two Stages: Non-thermal Plasma Followed by Heterogeneous Catalysis

2000-10-16
2000-01-2896
We present data in this paper showing that non-thermal plasma in combination with heterogeneous catalysis is a promising technique for the treatment of NOx in diesel exhaust. Using a commonly available zeolite catalyst, sodium Y, to treat synthetic diesel exhaust we report approximately 50% chemical reduction of NOx over a broad, representative temperature range. We have measured the overall efficiency as a function of the temperature and hydrocarbon concentration. The direct detection of N2 and N2O when the background gas is replaced by helium confirms that true chemical reduction is occurring.
Technical Paper

Comparison of Plasma-Catalyst and Lean NOx Catalyst for Diesel NOx Reduction

2000-10-16
2000-01-2895
Projected NOx and fuel costs are compared for a plasma-catalyst system and an active lean NOx catalyst system. Comparisons are based on modeling of FTP cycle performance. The model uses steady state laboratory device characteristics, combined with measured vehicle exhaust data to predict NOx conversion efficiency and fuel economy penalties. The plasma system uses a proprietary catalyst downstream of a plasma discharge. The active lean NOx catalyst uses a catalyst along with addition of hydrocarbons to the exhaust. For the plasma catalyst system, NOx conversion is available over a wide temperature range. Increased electrical power improves conversion but degrades vehicle fuel economy; 10 J/L energy deposition costs roughly 3% fuel economy. Improved efficiency is also available with larger catalyst size or increased exhaust hydrocarbon content. For the active lean NOx system, NOx conversion is available only in a narrow temperature range.
Technical Paper

Development of a Non-Thermal Plasma Reactor Electrical Model for Optimum NOx Removal Performance

2000-10-16
2000-01-2893
A double dielectric barrier discharge reactor driven by an alternating voltage is a relatively simple approach to promote oxidation of NO to NO2 for subsequent reduction in a catalyst bed. The chemical performance of such a non-thermal plasma reactor is determined by its current and electric field behavior in the gap, and by the fraction of the current carried by electrons, because the key reactants which initiate the NO oxidation and accompanying chemical changes are produced there, mostly by electron impact. We have tried to determine by models and experiments the bounds on performance of double dielectric barrier reactors and guidelines for optimization. Models reported here predict chemical results from time-resolved applied voltage and series sense capacitor data.
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