| 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
(författare)
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Automatic characterization of ignition processes with machine learning clustering techniques
- 2006
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Ingår i: International Journal of Chemical Kinetics. - : Wiley. - 0538-8066. ; 38:10, s. 621-633
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Tidskriftsartikel (refereegranskat)abstract
- Machine learning clustering techniques are used to characterize and, after the training phase, to identify phases within an ignition process. Forth e ethanol mechanism used in this paper, four physically identifiable phases were found and characterized: the initiation phase, preignition phase, ignition phase, and the postignition phase. The clustering is done with respect to fuzzy logic predicates identifying the maxima, minima, and inflection points of the species profiles. The cluster descriptions characterize the phases found and are in human interpretable form. in addition, these descriptions are powerful enough to be used to predict the phase structure under new conditions. Cluster phases were calculated for the ethanol mechanism at an equivalence ratio of 0.5, a pressure of 3.3 bar, and the temperatures 1200, 1300, 1400, and 1500 K. The resulting cluster phase descriptions were then successfully used to predict the phase structure and ignition delay times for other temperatures in the range from 1200 to 1500 K. The effect of different fuzzy logic predicate profile descriptions is studied to emphasize that the boundaries of some phases, specifically that between the preignition and the ignition phase, are a matter of what the modeler considers important. The end of the ignition phase corresponds to the ignition delay time and was relatively independent of the predicate descriptions used to determine the phases. (c) 2006 Wiley Periodicals, Inc.
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| 3. |
- Blurock, Edward
(författare)
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Characterizing complex reaction mechanisms using machine learning clustering techniques
- 2004
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Ingår i: International Journal of Chemical Kinetics. - : Wiley. - 0538-8066 .- 1097-4601. ; 36:2, s. 107-118
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Tidskriftsartikel (refereegranskat)abstract
- A machine learning conceptual clustering method applied to reaction mechanisms provides an automatic and, hence, unbiased means to differentiate between reactive phases within a total reactive process. Similar reactive phases were defined by means of local reaction sensitivity values. The method was applied to the Hochgreb and Dryer aldehyde combustion mechanism of 36 reactions. Three major time ranges were found and characterized: an initial phase of aldehyde reaction, an intermediate phase where only a small amount of aldehyde is left, and an end phase of reactions to final products. Further refinements of these phases into subtime intervals were found. All ranges found could be chemically justified. This method is meant as a supplement to existing methods of mechanism analysis and its main purpose is the automatic characterization of existing mechanisms and can potentially be used for mechanism reduction.
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| 4. |
- Blurock, Edward
(författare)
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Detailed mechanism generation. 1. Generalized reactive properties as reaction class substructures
- 2004
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Ingår i: Journal of Chemical Information and Computer Sciences. - : American Chemical Society (ACS). - 0095-2338 .- 1520-5142. ; 44:4, s. 1336-1347
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Tidskriftsartikel (refereegranskat)abstract
- This paper, the first in a series on the automatic generation of detailed hydrocarbon mechanisms for hydrocarbons, describes how generalized reaction types, specifically the 25 types outlined by Curran et al. for heptane and isooctane combustion, can be translated into general reaction classes. Each type description from Curran et al. ranges from specific, such as differentiating among 1degrees, 2degrees, and 3degrees centers, to nonspecific such as specifying intermediate specific as "products". In the latter case, additional interpretation of the reaction type must be extrapolated from other sources. The types are translated to the substructure "patterns" representing reaction classes. The success of fully translating all the rate and structural information described in these reaction types as they are defined in the literature demonstrates the power of the approach used here. A comparison of the generated reactions using these 25 types with that of a hand-produced heptane mechanism showed that, aside from well-defined exceptions, the set of reactions were almost identical. Often just the elimination of selected species (and sometimes reactions) was enough to make them identical. A notable exception was the use of lumped species in the hand-produced mechanism. The purpose of this paper is to show that an established set of reaction type descriptions can be translated to reaction classes suitable for automatic mechanism generation. A further goal of this paper is to show that these classes can be used to generate a detailed mechanism that mimics a hand produced one.
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| 5. |
- Blurock, Edward
(författare)
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Detailed mechanism generation. 2. Aldehydes, ketones, and olefins
- 2004
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Ingår i: Journal of Chemical Information and Computer Sciences. - : American Chemical Society (ACS). - 0095-2338 .- 1520-5142. ; 44:4, s. 1348-1357
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Tidskriftsartikel (refereegranskat)abstract
- Generalized reaction classes for the consumption and decomposition of aldehydes, ketones, and olefins are described. These classes are important for generating not only reactions for the consumption of the branching agents of low-temperature hydrocarbon combustion but also reactions of the oxidation of alkenes and the decomposition of cyclic ethers. These reaction classes have been extrapolated from specific reactions of existing validated mechanisms. The reaction patterns making up the class were derived by identifying the reactive center of the specific reactions and the important surrounding functional groups. The rates used currently are definitely "first guesses" based on these specific reactions. The reaction classes in this paper supplement the reaction classes derived from accepted reaction types in the previous paper in this series. The purpose of this paper is to outline a complete (with very few exceptions) set of reaction classes which describe the C-5 and C-6 products of the low-temperature and cyclic ether path in the heptane and isooctane mechanisms.
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| 6. |
- 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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| 7. |
- Lövås, Terese, et al.
(författare)
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Towards dynamically reduced mechanisms based on domain splitting
- 2003
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Ingår i: Computational Fluid and Solid Mechanics 2003, vols 1 and 2, Proceedings. - 9780080440460 ; , s. 1430-1433
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Konferensbidrag (refereegranskat)abstract
- We present a method for developing dynamically reduced chemical mechanisms based on the quasi steady state assumption and a domain splitting procedure. This procedure carries out the reduction within each domain separately according to a steady state selection parameter valid for the corresponding domain. The domains are defined according to a clustering algorithm. The method is applied to calculations of ethene diffusion flamelets.
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| 8. |
- 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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| 9. |
- Moréac, Gladys, et al.
(författare)
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Automatic generation of a detailed mechanism for the oxidation of n-decane
- 2006
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 1563-521X .- 0010-2202. ; 178:10-11, s. 2025-2038
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Tidskriftsartikel (refereegranskat)abstract
- A single detailed kinetic mechanism for the oxidation and combustion of n-decane and n-heptane has been written by means of an automatic mechanism generator ( REACTION) developed in our laboratory. It shows a good prediction of the ignition delay time versus temperature for the oxidation of n-decane at 13 and 50 bar and n-heptane at 13 and 40 bar for different equivalence ratios. The n-decane/n-heptane mechanism consists of a validated and recently published O-2=H-2=C-1-C-4 mechanism produced manually and a generated C-5-C-10 set of sub-mechanisms. The mechanism includes a complete description of both n-decane and n-heptane chemistry. This mechanism has a reasonable size, 506 species and 3684 reactions, but nevertheless it has an extensive range of chemistry. This paper represents not only the validation of a specific mechanism but also a validation of the rate constants of the reaction classes used to model the oxidation of alkanes at low and high temperature.
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