| 1. |
- Battin-Leclerc, Frederique, et al.
(författare)
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Towards cleaner combustion engines through groundbreaking detailed chemical kinetic models
- 2011
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Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry (RSC). - 0306-0012 .- 1460-4744. ; 40:9, s. 4762-4782
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Forskningsöversikt (refereegranskat)abstract
- In the context of limiting the environmental impact of transportation, this critical review discusses new directions which are being followed in the development of more predictive and more accurate detailed chemical kinetic models for the combustion of fuels. In the first part, the performance of current models, especially in terms of the prediction of pollutant formation, is evaluated. In the next parts, recent methods and ways to improve these models are described. An emphasis is given on the development of detailed models based on elementary reactions, on the production of the related thermochemical and kinetic parameters, and on the experimental techniques available to produce the data necessary to evaluate model predictions under well defined conditions (212 references).
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| 2. |
- Blurock, Edward, et al.
(författare)
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Phase optimized skeletal mechanisms for engine simulations
- 2010
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Ingår i: Combustion Theory and Modelling. - : Informa UK Limited. - 1364-7830 .- 1741-3559. ; 14:3, s. 295-313
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Tidskriftsartikel (refereegranskat)abstract
- Adaptive chemistry is based on the principle that instead of having one comprehensive model describing the entire range of chemical source term space (typically parameters related to temperature, pressure and species concentrations), a set of computationally simpler models are used, each describing a local region (in multidimensional space) or phases (in zero-dimensional space). In this work, an adaptive chemistry method based on phase optimized skeletal mechanisms (POSM) is applied to a 96 species n-heptane-isooctane mechanism within a two-zone zero-dimensional stochastic reactor model (SRM) for an spark-ignition (SI) Engine. Two models differing only in the extent of reduction in the phase mechanism, gave speed-up factors of 2.7 and 10. The novelty and emphasis of this study is the use of machine learning techniques to decide where the phases are and to produce a usable phase recognition. The combustion process is automatically divided up into an 'optimal' set of phases through machine learning clustering based on fuzzy logic predicates involving a necessity parameter (a measure giving an indication whether a species should be included in the mechanism or not). The mechanism of each phase is reduced from the full mechanism based on this necessity parameter with respect to the conditions of that phase. The algorithm to decide which phase the process is in is automatically determined by another machine learning method that produces decision trees. The decision tree is made up of asking whether the mass fraction values were above or below given values. Two POSM studies were done, a conservative POSM where the species in each phase are eliminated based on a necessity parameter threshold (speed-up 2.7) and a further reduced POSM where each phase was further reduced by hand (speed-up 10). The automated techniques of determining the phases and for creating the decision tree are very general and are not limited to the parameter choices of this paper. There is also no fundamental limit as to the size of the original detailed mechanism. The interfacing to include POSM in an application does not differ significantly from using the original detailed mechanism.
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| 3. |
- Mersin, Ismail Emre, et al.
(författare)
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Hexadecane mechanisms: Comparison of hand-generated and automatically generated with pathways
- 2014
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Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 115, s. 132-144
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the automatically generated mechanism for hexadecane with both high and low temperature chemistry included is compared to a systematically generated mechanism by hand. In contrast to other systems for automatic generation, the REACTION system uses pathways to organize the application of reaction classes. A pathway is a sequence of reaction classes where only those species produced by the previous step of the pathway are used in the current step of the pathway. This "controlled" generation process not only mimics what is done by hand, but also helps to limit the size of the generated mechanisms. Both systematic reaction by reaction comparisons and numerical simulation (zero-dimensional constant volume) comparisons were done and the mechanisms were found to have minor differences. Both mechanisms used the same set of reaction classes to model the high and low temperature combustion chemistry of all n-alkanes up to hexadecane. In addition, a sensitivity analysis of all the reaction classes was performed. The generated mechanism has 2176 species and 7269 (reversible) reactions. (C) 2013 Elsevier Ltd. All rights reserved.
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