Refine Your Search

Topic

Search Results

Viewing 1 to 20 of 20
Technical Paper

The Prediction of Connecting Rod Fretting and Fretting Initiated Fatigue Fracture

2004-10-25
2004-01-3015
The influence of big-end bore fretting on connecting rod fatigue fracture is investigated. A finite element model, including rod-bearing contact interaction, is developed to simulate a fatigue test rig where the connecting rod is subjected to an alternating uniaxial load. Comparison of the model results with a rod fracture from the fatigue rig shows good correlation between the fracture location and the peak ‘Ruiz’ criterion, rather than the peak tensile stress location, indicating the potential of fretting to initiate a fatigue fracture and the usefulness of the ‘Ruiz’ criterion as a measure of location and severity. The model is extended to simulate a full engine cycle using pressure loads from a bearing EHL analysis. A fretting map and a ‘Ruiz’ criterion map are developed for the full engine cycle, giving an indication of a safe ‘Ruiz’ level from an existing engine which has been in service for more than 5 years.
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

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

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

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

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.
Journal Article

Modeling Approach to Estimate EGR Cooler Thermal Fatigue Life

2015-04-14
2015-01-1654
Cooled EGR continues to be a key technology to meet emission regulations, with EGR coolers performing a critical role in the EGR system. Designing EGR coolers that reliably manage thermal loads is a challenge with thermal fatigue being a top concern. The ability to estimate EGR cooler thermal fatigue life early in the product design and validation cycle allows for robust designs that meet engine component reliability requirements and customer expectations. This paper describes a process to create an EGR cooler thermal fatigue life model. Components which make up the EGR cooler have differing thermal responses, consequently conjugate transient CFD must be used to accurately model metal temperatures during heating and cooling cycles. Those metal temperatures are then imported into FEA software for structural analysis. Results from both the CFD and FEA are then used in a simplified numerical model to estimate the virtual strain of the EGR cooler.
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.
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

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

Interaction Between Fuel Additive and Oil Contaminant: (II) Its Impact on Fuel Stability and Filter Plugging Mechanism

2003-10-27
2003-01-3140
Sulfur containing species as well as other polar molecules provide lubricity and thermal stability to diesel fuels. During the refining process to produce low and ultra-low sulfur diesel fuels, these components are removed. As a result, fuel additives such as lubricity agents and antioxidant may be added to protect fuel stability and prevent fuel pump wear. Some lubricity additives, such as dimer acids, resulted in fuel filter plugging. The plugging mechanism was related to the capability of aliphatic acids to form agglomeration by interactions with the overbased detergents, delivered into the fuel as oil contaminants. Other sources of acids, derived from thermal degradation, can lead to the same problem. In this study, individual lubricant additives were mixed in the fuel to form single- and dual-component systems. Levels of compatibility and amounts of interaction products were evaluated for individual solutions.
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

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

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

Finite Element Method Based Fatigue Analysis of a Gray Cast Iron Component

2013-04-08
2013-01-1205
Good understanding and accurate prediction of component fatigue strength is crucial in the development of modern engine. In this paper a detail analysis was conducted on an engine component made of gray cast iron with finite element method to evaluate the fatigue strength. This component has notches that cause local stress concentration. It is well known that fatigue behavior of a notch is not uniquely defined by the local maximum stress but depends on other factors determined by notch geometry and local stress distribution. The component fatigue strength was underestimated by only considering the stresses on the notch surface for fatigue life prediction. The critical distance approach was adopted to predict the fatigue behavior of this component. Good agreements are observed between predicted life by the critical distance method and actual field data.
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

EGR Cooler Field Return Rate Evaluation Based on Product and Application Variation

2019-04-02
2019-01-0915
The automotive industry drives some of the most stringent product requirements to ensure long product life and customer satisfaction. To demonstrate compliance with these requirements new and more accurate evaluation methods are needed. Thermal fatigue life in EGR coolers for heavy duty diesel applications have historically been a critical focus for engine OEMs. Being able to accurately evaluate product return rates due to thermal fatigue failures gives the OEM confidence that all end users will be satisfied, and allows program management to properly make fiscal decisions. Additionally, weight and cost optimization can be conducted with greater confidence. This is accomplished by accounting for product variation and application variation in thermal fatigue life evaluations. Including these variations requires a simplified numerical method to calculate product life, as tens of thousands of samples will be run through the analysis to represent real life random variation.
Technical Paper

Durability Test Suite Optimization Based on Physics of Failure

2018-04-03
2018-01-0792
Dynamometer (dyno) durability testing plays a significant role in reliability and durability assessment of commercial engines. Frequently, durability test procedures are based on warranty history and corresponding component failure modes. Evolution of engine designs, operating conditions, electronic control features, and diagnostic limits have created challenges to historical-based testing approaches. A physics-based methodology, known as Load Matrix, is described to counteract these challenges. The technique, developed by AVL, is based on damage factor models for subsystem and component failure modes (e.g. fatigue, wear, degradation, deposits) and knowledge of customer duty cycles. By correlating dyno test to field conditions in quantifiable terms, such as customer equivalent miles, more effective and efficient durability test suites and test procedures can be utilized. To this end, application of Load Matrix to a heavy-duty diesel engine is presented.
Journal Article

Durability Study of a High Pressure Common Rail Fuel Injection System Using Lubricity Additive Dosed Gasoline-Like Fuel - Additional Cycle Runtime and Teardown Analysis

2019-04-02
2019-01-0263
This study is a continuation of previous work assessing the robustness of a Cummins XPI common rail injection system operating with gasoline-like fuel. All the hardware from the original study was retained except for the high pressure pump head and check valves which were replaced due to cavitation damage. An additional 400 hour NATO cycle was run on the refurbished fuel system to achieve a total exposure time of 800 hours and detect any other significant failure modes. As in the initial investigation, fuel system parameters including pressures, temperatures and flow rates were logged on a test bench to monitor performance over time. Fuel and lubricant samples were taken every 50 hours to assess fuel consistency, metallic wear, and interaction between fuel and oil. High fidelity driving torque and flow measurements were made to compare overall system performance when operating with both diesel and light distillate fuel.
Technical Paper

Development and Demonstration of a Soot Generator Integrated Bench Reactor

2014-04-01
2014-01-1589
Experimental evaluation of soot trapping and oxidation behaviors of various diesel particulate filters (DPF) has been traditionally hampered by several experimental difficulties, such as the deposition of soot particles with well-characterized and consistent properties, and the tracking of the soot oxidation rate in real time. In the present study, an integrated bench flow-reactor system with a soot generator has been developed and its capabilities were demonstrated with regards to: Consistently and controllably loading soot on DPF samples; Monitoring the exhaust gas composition by FTIR, including quantification of the soot oxidation rate using CO and CO2; Measuring soot oxidation characteristics of various DPF samples. Soot particles were produced from a laminar propane co-flow diffusion flame.
X