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Journal Article

Model-Based Approaches in Developing an Advanced Aftertreatment System: An Overview

2019-01-15
2019-01-0026
Cummins has recently launched next-generation aftertreatment technology, the Single ModuleTM aftertreatment system, for medium-duty and heavy-duty engines used in on-highway and off-highway applications. Besides meeting EPA 2010+ and Euro VI regulations, the Single ModuleTM aftertreatment system offers 60% volume and 40% weight reductions compared to current aftertreatment systems. In this work, we present model-based approaches that were systematically adopted in the design and development of the Cummins Single ModuleTM aftertreatment system. Particularly, a variety of analytical and experimental component-level and system-level validation tools have been used to optimize DOC, DPF, SCR/ASC, as well as the DEF decomposition device.
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

Experimental and Kinetic Modeling of Degreened and Aged Three-way Catalysts: Aging Impact on Oxygen Storage Capacity and Catalyst Performance

2018-04-03
2018-01-0950
The aging impact on oxygen storage capacity (OSC) and catalyst performance was investigated on one degreened and one aged (hydrothermally aged at 955 °C for 50 h) commercial three-way catalyst (TWC) by experiments and modeling. The difference of OSC between the degreened and aged TWCs was dependent on catalyst temperature. The largest difference was found at 600 °C, at which the amount of OSC decreased by 45.5%. Catalyst performance was evaluated through lightoff tests at two simulated engine exhaust conditions (lean and rich) on a micro-reactor. The aging impact on the catalyst performance was different under lean and rich environments and investigated separately. At the lean condition, oxidation of CO and C3H6 was significantly suppressed while oxidation of C3H8 was relatively less degraded. At the rich condition, the inhibition effect was more pronounced on the aged TWC and inhibiting hydrocarbon species from C3H6 partial oxidation can survive at temperatures up to 450 °C.
Technical Paper

Comparison of Hydrocarbon Measurement with FTIR and FID in a Dual Fuel Locomotive Engine

2016-04-05
2016-01-0978
Exhaust emissions of non-methane hydrocarbon (NMHC) and methane were measured from a Tier 3 dual-fuel demonstration locomotive running diesel-natural gas blend. Measurements were performed with the typical flame ionization detector (FID) method in accordance with EPA CFR Title 40 Part 1065 and with an alternative Fourier-Transform Infrared (FTIR) Spectroscopy method. Measurements were performed with and without oxidation catalyst exhaust aftertreatment. FTIR may have potential for improved accuracy over the FID when NMHC is dominated by light hydrocarbons. In the dual fuel tests, the FTIR measurement was 1-4% higher than the FID measurement of. NMHC results between the two methods differed considerably, in some cases reporting concentrations as much as four times those of the FID. However, in comparing these data it is important to note that the FTIR method has several advantages over the FID method, so the differences do not necessarily represent error in the FTIR.
Journal Article

Impact of Carbonaceous Compounds Present in Real-World Diesel Exhaust on NOx Conversion over Vanadia-SCR Catalyst

2016-04-05
2016-01-0921
Exposure of hydrocarbons (HCs) and particulate matter (PM) under certain real-world operating conditions leads to carbonaceous deposit formation on V-SCR catalysts and causes reversible degradation of its NOx conversion. In addition, uncontrolled oxidation of such carbonaceous deposits can also cause the exotherm that can irreversibly degrade V-SCR catalyst performance. Therefore carbonaceous deposit mitigation strategies, based on their characterization, are needed to minimize their impact on performance. The nature and the amount of the deposits, formed upon exposure to real-world conditions, were primarily carried out by the controlled oxidation of the deposits to classify these carbonaceous deposits into three major classes of species: i) HCs, ii) coke, and iii) soot. The reversible NOx conversion degradation can be largely correlated to coke, a major constituent of the deposit, and to soot which causes face-plugging that leads to decreased catalyst accessibility.
Technical Paper

Development of Chrysler Oxidation and Deposit Engine Oil Certification Test

2015-09-01
2015-01-2045
With the impending development of GF-6, the newest generation of engine oil, a new standardized oil oxidation and piston deposit test was developed using Chrysler 3.6 L Pentastar engine. The performance requirements and approval for passenger car light duty gasoline engine oil categories are set by the International Lubricants Standardization and Approval committee (ILSAC) and the American Petroleum Institute (API) using standardized testing protocols developed under the guidance of ASTM, the American Society for Testing and Materials. This paper describes the development of a new ASTM Chrysler oxidation and deposit test that will be used to evaluate lubricants performance for oil thickening and viscosity increase, and piston deposits.
Technical Paper

Impact of Sulfur-Oxides on the Ammonia Slip Catalyst Performance

2014-04-01
2014-01-1545
The ammonia slip catalyst (ASC), typically composed of Pt oxidation catalyst overlaid with SCR catalyst, is employed for the mitigation of NH3 slip originating from SCR catalysts. Oxidation and SCR functionalities in an ASC can degrade through two key mechanisms i) irreversible degradation due to thermal aging and ii) reversible degradation caused by sulfur-oxides. The impact of thermal aging is well understood and it mainly degrades the SCR function of the ASC and increases the NH3 conversion to undesired products [1]. This paper describes the impact of sulfur-oxides on critical functions of ASC and on NH3 oxidation activity and selectivity towards N2, NOx and N2O. Furthermore impact of desulfation under selected conditions and its extent of ASC performance recovery is explained.
Technical Paper

New Insights into the Unique Operation of Small Pore Cu-Zeolite SCR Catalyst: Overlapping NH3 Desorption and Oxidation Characteristics for Minimizing Undesired Products

2014-04-01
2014-01-1542
An operational challenge associated with SCR catalysts is the NH3 slip control, particularly for commercial small pore Cu-zeolite formulations as a consequence of their significant ammonia storage capacity. The desorption of NH3 during increasing temperature transients is one example of this challenge. Ammonia slipping from SCR catalyst typically passes through a platinum based ammonia oxidation catalyst (AMOx), leading to the formation of the undesired byproducts NOx and N2O. We have discovered a distinctive characteristic, an overlapping NH3 desorption and oxidation, in a state-of-the-art Cu-zeolite SCR catalyst that can minimize NH3 slip during temperature transients encountered in real-world operation of a vehicle.
Journal Article

Internal Diesel Injector Deposits: Theory and Investigations into Organic and Inorganic Based Deposits

2013-10-14
2013-01-2670
Over the last two decades, global emission regulations have become more stringent and have required the use of more advanced fuel injection systems. This includes the use of tighter tolerances, more rapid injections and internal components actuated by weaker injection forces. Unfortunately, these design features make the entire system more susceptible to fuel contaminants. Over the last six years, the composition of these contaminants has evolved from hard insoluble debris, such as dust and rocks, to soluble chemical contaminants. Recent research by the diesel engine manufacturers, fuel injection equipment suppliers and the fuel and fuel additive industry has discovered a major source of the soluble chemical contaminant that leads to injector deposits to be derived from cost effective and commonly used additives used to protect against pipeline corrosion.
Technical Paper

Numerical and Experimental Characterization of the Dual-Fuel Combustion Process in an Optically Accessible Engine

2013-04-08
2013-01-1670
The dual-fuel combustion process of ethanol and n-heptane was characterized experimentally in an optically accessible engine and numerically through a chemical kinetic 3D-CFD investigation. Previously reported formaldehyde PLIF distributions were used as a tracer of low-temperature oxidation of straight-chained hydrocarbons and the numerical results were observed to be in agreement with the experimental data. The numerical and experimental evidence suggests that a change in the speed of flame propagation is responsible for the observed behavior of the dual-fuel combustion, where the energy release duration is increased and the maximum rate of pressure rise is decreased. Further, an explanation is provided for the asymmetrical energy release profile reported in literature which has been previously attributed to an increase in the diffusion-controlled combustion phase.
Technical Paper

Impact of Different Forms of Sulfur Poisoning on Diesel Oxidation Catalyst Performance

2013-04-08
2013-01-0514
Despite drastic reduction of sulfur content in diesel fuel in the recent years, especially with the introduction of Ultra-Low Sulfur Diesel (ULSD), sulfur poisoning remains one of the most significant factors impacting performance of various catalysts in diesel aftertreatment systems. This is because even with ULSD, cumulative exposure of a catalyst over its lifetime in a heavy-duty diesel system may amount to kilograms of sulfur. In this study, we have found that the impact of sulfur poisoning on the performance of various diesel oxidation catalysts (DOC) strongly depends on the catalyst's operation history. For example, exposing a DOC to limited amounts of freshly deposited sulfur in bench reactor testing was shown to have a substantial detrimental effect. On the other hand, several samples which returned from vehicle or test-cell aging with high sulfur loading, have shown no signs of poisoning.
Journal Article

Investigation of the Impact of Real-World Aging on Diesel Oxidation Catalysts

2012-04-16
2012-01-1094
Real-world operation of diesel oxidation catalysts (DOCs), used in a variety of aftertreatment systems, subjects these catalysts to a large number of permanent and temporary deactivation mechanisms. These include thermal damage, induced by generating exotherm on the catalyst; exposure to various inorganic species contained in engine fluids; and the effects of soot and hydrocarbons, which can mask the catalyst in certain operating modes. While some of these deactivation mechanisms can be accurately simulated in the lab, others are specific to particular engine operation regimes. In this work, a set of DOCs, removed from prolonged service in the field, has been subjected to a detailed laboratory study. Samples obtained from various locations in these catalysts were used to characterize the extent and distribution of deactivation.
Journal Article

New Insights into Reaction Mechanism of Selective Catalytic Ammonia Oxidation Technology for Diesel Aftertreatment Applications

2011-04-12
2011-01-1314
Mitigation of ammonia slip from SCR system is critical to meeting the evolving NH₃ emission standards, while achieving maximum NOx conversion efficiency. Ammonia slip catalysts (ASC) are expected to balance high activity, required to oxidize ammonia across a broad range of operating conditions, with high selectivity of converting NH₃ to N₂, thus avoiding such undesirable byproducts as NOx or N₂O. In this work, new insights into the behavior of an advanced ammonia slip catalyst have been developed by using accelerated progressive catalyst aging as a tool for catalyst property interrogation. The overall behavior was deconstructed to several underlying functions, and referenced to an active but non-selective NH₃ oxidation function of a diesel oxidation catalyst (DOC) and to the highly selective but minimally active NH₃ oxidation function of an SCR catalyst.
Technical Paper

The Effects of Thermal Degradation on the Performance of a NOX Storage/Reduction Catalyst

2009-04-20
2009-01-0631
The performance characteristics of a commercial lean-NOX trap catalyst were evaluated between 200 and 500°C, using H2, CO, and a mixture of both H2 and CO as reductants before and after different high-temperature aging steps, from 600 to 750°C. Tests included NOX reduction efficiency during cycling, NOX storage capacity (NSC), oxygen storage capacity (OSC), and water-gas-shift (WGS) and NO oxidation reaction extents. The WGS reaction extent at 200 and 300°C was negatively affected by thermal degradation, but at 400 and 500°C no significant change was observed. Changes in the extent of NO oxidation did not show a consistent trend as a function of thermal degradation. The total NSC was tested at 200, 350 and 500°C. Little change was observed at 500°C with thermal degradation but a steady decrease was observed at 350°C as the thermal degradation temperature was increased.
Technical Paper

Quantitative Flow-Reactor Study of Diesel Soot Oxidation Process

2002-05-06
2002-01-1684
Advanced flow-reactor capabilities created at Cummins were applied to the study of the diesel particulate matter (soot) oxidation process. This approach complemented the on-engine studies with a number of important features, including accurate control of gas composition and soot layer temperature. Using the developed methodology for quantitative soot oxidation studies in a broad range of temperatures (200-700°C), an initial set of experiments was performed to compare the behavior of the real and model soot samples under the identical conditions (10%vol. of O2, 0-15%vol. of H2O). It was found that presence of H2O vapor synergistically enhances the rate of oxidation by O2 of the diesel soot sample. However, the behavior of the model soot sample (carbon black) was virtually not affected by H2O. Kinetic analysis of the obtained results revealed an unusual type of behavior, with the activation energy of soot oxidation increasing in the course of the experiment.
Technical Paper

Paint Integrity and Corrosion Sensor

2002-03-04
2002-01-0205
Atmospheric corrosion of steels, aluminum alloys, and Al-clad aluminum alloys is a problem for many civil engineering structures, commercial and military vehicles, and aircraft. Paint is usually the primary means to prevent the corrosion of steel bridge components, automobiles, trucks, and aircraft. Under ideal conditions, the coating provides a continuous layer that is impervious to moisture. At present, maintenance cycles for commercial and military aircraft and ground vehicles, as well as engineered structures, is based on experience and appearance rather than a quantitative determination of coating integrity. To improve the maintenance process and reduce costs, sensors are often used to monitor corrosion. The present suite of sensors designed to detect corrosion and marketed to predict the lifetime of the engineered components, however, are not useful for determining the condition of the protective paint coatings.
Technical Paper

Predicting Sequence VI, VIA, and VIB Engine Tests Using Laboratory Methods

2001-05-07
2001-01-1904
Engine tests are widely used to measure the ability of lubricating oils to reduce fuel consumption through improved mechanical efficiency. Previous publications have correlated laboratory-scale tests with the well-established Sequence VI and VIA engine methods. The present paper uses a matrix of 66 oils to produce an empirical model for the recently developed Sequence VIB engine test. A smaller matrix of oils was available for correlation with Sequence VI and VIA results. The models combine a purposely-designed friction test with conventional measures of kinematic and high-temperature high-shear viscosity. Good correlation was obtained with the Sequence VI, VIA and VIB results, as well as each of the five stages in the Sequence VIB test. The effects of lubricant oxidation in the 96-hour FEI-2 portion of the Sequence VIB test were similar for each of the oils. As a result, good correlation was observed between FEI-1 and FEI-2 results from the VIB test.
Technical Paper

Development of a Lean-NOx Catalyst Containing Metal-Ligand Complex Impregnated Molecular Sieves

1996-10-01
962050
This paper describes the development and evaluation of an operative catalyst for the reduction of NOx in lean exhaust. A catalyst that incorporates iron (II)-complex impregnated modified mesoporous molecular sieves (MCM-41) has been synthesized and further treated with [pd(NH3)4]Cl2 [1]. Experimental results suggest a hydrocarbon-independent reduction of NOx takes place on the iron center, and oxidation of CO is assisted by the palladium ion. The catalytic activity toward HC CO, and NOx removal was studied with simulated and real engine exhaust in the laboratory and on an engine, respectively. Engine test results demonstrate a reduction of NOx of up to 10 percent at catalyst inlet temperatures in the range of 260°C to 280°C. In this paper, possible NOx reduction pathways are also discussed.
Technical Paper

Evaluation of Possible Methanol Fuel Additives for Reducing Engine Wear and/or Corrosion

1990-10-01
902153
The use of fuel additives is one possible approach to reduce wear and corrosion in methanol fueled automobile engines. One hundred and six compounds added to M100 fuel in modest concentrations (1%) were tested in a Ball on Cylinder Machine (BOCM) for their ability to improve lubricity. The most promising candidates were then tested in an engine using a modified ASTM Sequence V-D wear screening test. Additive performance was measured by comparing the buildup of wear metals in the oil to that obtained from an engine fueled with neat M100. The BOCM method of evaluating the additive candidates proved inadequate in predicting abrasive engine wear under the test conditions utilized for this research program.
Technical Paper

Shale-Derived Diesel Test Fuels for Utilization Studies

1988-10-01
881627
An untreated heavy distillate fraction from a mixture of Geokinetics and Occidental shale oils was hydrogenated at three levels of severity. The three products showed good ignition quality and met most of the current specifications for No. 2-D diesel fuel. Nitrogen contents ranged from 250 to 1890 parts per million. Good oxidation stability was obtained in the product with lowest nitrogen content. Stability of the other two products was marginal but would be improved by use of an antioxidant additive. The test fuels will be used in engine and combustion studies.
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