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Friday, September 10 |
| CLEERS Home >Workshops >Workshop 1 > Abstracts > | Workshop 1: Abstracts |
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Cross-Cut Lean Exhaust Emissions Reduction Simulations First Crosscut Workshop on Lean Emissions Reduction Simulation Agenda | Summary | Abstracts | Presentations | Attendees A new mechanism for prompt NO formation:
The Spin-Allowed CH + N2 --> HNCN --> H+ NCN Reaction The result of our recent high-level ab initio molecular orbital calculation reveals that the CH + N2 reaction occurs primarily over the spin-allowed doublet ground electonic potential energy surface producing H + NCN, instead of the commonly assumed spin-forbiddened HCN + N products proposed by Fenimore in 1971. In this talk, the detailed PES of the HCN2 system will be discussed and the predicted rate constant for NCN formation from CH + N2 will be presented.
Recent experimental results with NOx adsorber catalysts
NOx control via carbon sorbents and selective NOx recirculation NOx Control via Carbon Sorbents and Selective NOx Recirculation Treatment of NOx in lean exhausts has focused on either catalytic reduction or trapping combined with reduction. Some previous work by Daimler Benz has considered the possibility of trapping NOx and destroying it through recirculation of a concentrated NOx stream into the combustion chamber. However, trap materials they considered were not effective in exhausts containing sulfur. Recent developments in carbon sorbents have provided materials that can adsorb both NO and NO2, and competitively adsorb SO2 without adverse impact on NOx sorption capacity. Present work is focusing on incorporation of the carbon based sorbent in an on-engine NOx control system in combination with selective NOx recirculation in a diesel engine. Both the dynamics of sorption and desorption and the physical and chemical processes affecting the recirculated NOx are important topics for simulation. The dynamics of sorption and desorption may have a significant impact on the required carbon trap size and its on-vehicle collection efficiency. Modeling of the fate of recirculated NOx through the premixed and mixing controlled phases of combustion is important in understanding how to maximize the NOx destruction efficiency, and to develop injection strategies for the recirculated NOx.
Modeling and simulation of three-way catalysts The pollutant conversion performance of a converter is influenced by a number of physical and chemical processes that take place in gaseous and solid phases as the exhaust gases flow through the catalyst. A quantitative predictive understanding of these complex catalyst processes involving flow dynamics, heterogeneous surface reactions, and heat and mass transport mechanisms is important in accurate modeling of catalyst operation. This talk presents the results of a computational investigation on the role of chemical kinetics and convective heat and mass transport mechanisms. The study assessed the performance of various chemical kinetic schemes by comparing the results of numerical model with the experimental measurements. By showing significant differences in catalyst behavior during steady state and transient conditions, the talk also emphasizes the importance of studying the catalyst dynamic behavior. It discusses the effect of fluctuation in air-fuel ratio, which is a major contributor to transient operating conditions of catalysts. The talk elucidates the coupled response of transients and chemical kinetics on the catalyst HC, CO, and NO conversion efficiencies.
System Emission Reduction Analysis The mission of the Department of Energy's (DOE's) Advanced Petroleum-Based Fuels (APBF) Program is to explore and define the role of advanced petroleum and non-petroleum fuel constituents to enable light-duty vehicles and heavy-duty engines to maintain continuous improvement in engine efficiency and durability while meeting current and planned emission standards and additional potential constraints (e.g. toxins, ultrafine particulate matter (PM), greenhouse gases). DOE's Offices of Advanced Automotive Technologies (OAAT) and Heavy Vehicle Technologies (OHVT) have developed the APBF Program Multi-Year Program Plan (MYPP) to guide research and development towards accomplishing this mission. The MYPP outlines research and development needs for advanced petroleum-based fuels for compression-ignition, direct-injection (CIDI) engines for on-road vehicles. The MYPP calls for the development and validation of predictive models that would be used to set emissions targets for the program, and to develop pathways for realizing those targets. The National Renewable Energy Laboratory (NREL) has worked with the Department of Energy to launch a Systems Emissions Reduction (SER) analysis activity. The purpose of this project is to develop and use systems analysis tools that will support execution of the APBF MYPP. NREL is evaluating the effects of fuel properties on engine emissions and emission control system performance for three vehicle platforms.
Turbulence and knock prediction in IC engines
Using SURFACE CHEMKIN to facilitate the solution of problems involving complex heterogeneous reactions The incorporation of detailed surface chemistry into numerical routines for simulating a complex reacting-flow environment is a challenging endeavor. Beside the issue of generating a complete chemical-kinetic description of the process, is the management and manipulation of species, rates, and other pertinent process variables at the code level. SURFACE CHEMKIN was developed to address such issues, and has evolved into a comprehensive tool that facilitates the integration of elementary heterogeneous chemical kinetics into problems involving gas-solid interfaces. SURFACE CHEMKIN is a collection of approximately 70 modular Fortran subroutines that may be called from a user's application code to return information on chemical production rates and thermodynamic properties. The discussion will include a description of the code-level interface, as well as construction formalisms native to SURFACE CHEMKIN that allow for the treatment of a wide variety of heterogeneous reactions. The utility of this software will be demonstrated via application to two reacting flow problems, the first involving partial oxidation of methane and ethane over platinum in stagnation flow, and the second, low temperature reactions of hydrogen in the presence of carbon monoxide on the surface of a palladium chemresistor in a transient perfectly-stirred reactor.
Microkinetics of catalytic processes Microkinetics of Catalytic Processes Robert S. Weber Arthur D. Little, Inc., 20 Acorn Park, Cambridge, Massachusetts 02140, USA Microkinetic models are those in which the reaction network is written in terms of elementary steps (reactions that proceed molecularly as written), whose rates are expressed as coupled differential equations. The parameters that appear in such models can, in principle, be related, by quantum chemistry, spectroscopy, thermochemistry and statistical mechanics, to the reaction chemistry of the species. Thus, a microkinetics description of the activity, selectivity and longevity of a catalyst would for a natural bridge between the analysis and synthesis of engineered catalysts. In this talk I will describe our use of microkinetics models in the description of automotive aftertreatment and introduce the software that we have developed to facilitate the manipulations of reaction sets and parameters. We have employed this package, called Bistro?, to model the performance of 3-way catalysts and NOx storage and reduction catalysts. Bistro links to GT-Power and the combination permits the incorporation of detailed catalyst models in the emulation of a complete powetrain.
Computational chemistry applied to DeNOx and DeSOx catalysts
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