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BlueBellMouse. A Tool for Kinetic Model Development

Bellanca, Raffaella LU (2004)
Abstract (Swedish)
Popular Abstract in Swedish

För att kunna simulera de fysikaliska fenomen som pågår i förbränning, krävs även en beskrivning av den kinetik som ingår i förbränningsprocessen. För detta ändamål utvecklas kinetiska modeller. En kinetisk modell är en lista med kemiska reaktioner och reaktionshastighetsparametrar. Modellernas tillämpningsområde begränsas av de valideringsfall och de fysikaliska parametrar, som beaktades då modellen sammanställdes. Ofta erfordras en ny optimering av modellen om den används under andra betingelser. Optimering av kinetiska modeller har tidigare automatiserats, till exempel då en referensmekanism för naturgas, GRI-mech, utvecklades. Med optimering justeras reaktionshastighetsparametrarna i... (More)
Popular Abstract in Swedish

För att kunna simulera de fysikaliska fenomen som pågår i förbränning, krävs även en beskrivning av den kinetik som ingår i förbränningsprocessen. För detta ändamål utvecklas kinetiska modeller. En kinetisk modell är en lista med kemiska reaktioner och reaktionshastighetsparametrar. Modellernas tillämpningsområde begränsas av de valideringsfall och de fysikaliska parametrar, som beaktades då modellen sammanställdes. Ofta erfordras en ny optimering av modellen om den används under andra betingelser. Optimering av kinetiska modeller har tidigare automatiserats, till exempel då en referensmekanism för naturgas, GRI-mech, utvecklades. Med optimering justeras reaktionshastighetsparametrarna i stringent matematisk mening genom att använda experimentella data som bivillkor.



Detta tillvägagångssätt, som hitintills har använts för att sammanställa allmänna detaljerade kinetiska modeller, är tillämpbart även vid utveckling av kemiska mekanismer för specifika ändamål, till exempel för användning i motorsimuleringar.



Homogena kompressionsantändningsmotorer, s.k. HCCI-motorer, har under de senaste åren uppmärksammats av forskare verksamma på universiteten och inom industrin, för deras höga termiska verkningsgrad och låga kväveoxid- och partikelemissioner. Svårigheterna att reglera HCCI-motorn, och de höga kolväte- och kolmonoxidutsläppen, är stora problem, som fortfarande återstår att lösa för att dessa motorer skall kunna användas kommersiellt.



Nästa steg i HCCI-forskningen är att föra över den ackumulerade kunskapsmängden till industriella tillämpingar. Forslening inom styr och reglerområdet pågår emellertid fortforande. Behovet av att ändra bränslekarakteristika erfordrar att kontinuerligt uppdaterade kinetiska modeller optimerade för motortillämpningar är tillgängliga.



I industriella tillämpningar är även beräkningstiden en viktig aspekt. En nyckelfaktor för beräkningstiden är den kinetiska modellens storlek. En rimlig storlek på den kinetiska modellen kan uppnås genom att starkt reducera den detaljerade mekanismen. Med optimeringsteknik är det möjligt att överreducera den ursprungliga mekanismen och därefter återoptimera koefficitenterna a posteriori för att återigen erhålla noggrannhet.



Genom att automatisera och förenkla handhavandet av de verktyg som krävs för simulering, reducering och optimering, kan forskning inom detta område göras mera tillgängligt för forskare verksamma utanför den akademiska världen. I föreliggande arbete har ett mjukvarupaket, BlueBellMouse, utvecklats för denna tillämpning.



Två studier har utförts med detta mjukvarupaket. I den första studien optimerades en referensmodell för naturgas, utvecklad av Warnatz et al. för ett antal HCCI-motorexperiment. Modellen reducerades därefter genom att eliminera redundanta kemiska komponenter och reaktioner tills endast de viktigaste återstod, vilket ledde till hög diskrepans mellan simuleringar och experiment. Slutligen återoptimerades den s.k. skelettmekanismen, och god överensstämmelse mellan simuleringar och experiment uppnåddes. Den andra studien omfattade optimering av en n-heptan/iso-oktan referensmekansim för bensin mot ett antal shock tube-experiment. (Less)
Abstract
The simulation of physical phenomena occurring in chemical reactors requires the description of the kinetics involved in the underlying combustion process. Kinetic models are developed for this purpose. A software package, BlueBellMouse, has been developed to facilitate a deeper automatization and ease of simulation, reduction and optimization of kinetic models. A kinetic model is made of a list of chemical reactions and their reaction rate parameters. The range of application of these models is limited by the set of validation cases and physical parameters that have been taken into account during the compilation. Often, their use under different conditions demands a re-optimization. A systematic optimization technique has been developed... (More)
The simulation of physical phenomena occurring in chemical reactors requires the description of the kinetics involved in the underlying combustion process. Kinetic models are developed for this purpose. A software package, BlueBellMouse, has been developed to facilitate a deeper automatization and ease of simulation, reduction and optimization of kinetic models. A kinetic model is made of a list of chemical reactions and their reaction rate parameters. The range of application of these models is limited by the set of validation cases and physical parameters that have been taken into account during the compilation. Often, their use under different conditions demands a re-optimization. A systematic optimization technique has been developed in the past that consists in adjusting the reaction rate parameters in a mathematically rigorous way using a set of experimental data as constraints. This approach, used so far for the compilation of “general purpose” detailed kinetic models, applies as well to the development of chemical mechanisms for specific tasks, like for example engine simulations. Homogeneous Charge Compression Ignition (HCCI) engine has found in recent years the interest of the scientific community and automotive industry for their ability to provide high thermal efficiencies and low NOx and particulate emissions. The next step in HCCI engine research is to transfer the accumulated knowledge to industrial applications. Some shortcomings are still to be solved to make these engines suitable for commercialization like, for example, the difficulty in control. Various techniques have been investigated in order to overcome those problems; from variation of the fuel composition to exhaust gas recirculation. The need to change fuel characteristics requires the availability of continuously updated kinetic models optimized under engine conditions. In an operative environment, the calculation speed becomes an essential feature. A key factor for the computational time is the dimension of the kinetic model. One way to achieve reasonable dimensions is to strongly reduce the detailed mechanism. Through the optimization techniques, it is feasible to over reduce the original mechanism and re-optimize the coefficients a posteriori to regain accuracy in the model predictions. Using BlueBellMouse a natural gas fuel reference model as developed by Warnatz et al. has been optimized for a set of HCCI engine experimental cases. The model has then been reduced eliminating redundant species and the corresponding reactions until just the most essential components were left and the model predictions showed high discrepancy with respect to the experimental data. The so obtained skeleton mechanism has then been re-optimized to regain the required accuracy. In addition the optimization of a gasoline fuel reference mechanism containing mixture of n-heptane and iso-octane, toward a set of shock tube experimental cases. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Angelberger, Christian, Frankrike.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
combustion, HCCI, reduction, engine, kinetic, simulation, graphical user interface, GUI, optimization, chemical mechanism, Physics, Fysik, Fysicumarkivet A:2004:Bellanca
pages
117 pages
publisher
Combustion Physics, Lund Institute of Technology
defense location
Dept of Physics, room B, Professorsgatan 1, Lund Institute of Technology.
defense date
2004-06-04 10:15
ISSN
1102-8718
language
English
LU publication?
yes
id
ce04a0bc-b77b-497e-97eb-0f97aeaa4494 (old id 21806)
date added to LUP
2007-05-28 14:46:33
date last changed
2016-09-19 08:44:52
@phdthesis{ce04a0bc-b77b-497e-97eb-0f97aeaa4494,
  abstract     = {The simulation of physical phenomena occurring in chemical reactors requires the description of the kinetics involved in the underlying combustion process. Kinetic models are developed for this purpose. A software package, BlueBellMouse, has been developed to facilitate a deeper automatization and ease of simulation, reduction and optimization of kinetic models. A kinetic model is made of a list of chemical reactions and their reaction rate parameters. The range of application of these models is limited by the set of validation cases and physical parameters that have been taken into account during the compilation. Often, their use under different conditions demands a re-optimization. A systematic optimization technique has been developed in the past that consists in adjusting the reaction rate parameters in a mathematically rigorous way using a set of experimental data as constraints. This approach, used so far for the compilation of “general purpose” detailed kinetic models, applies as well to the development of chemical mechanisms for specific tasks, like for example engine simulations. Homogeneous Charge Compression Ignition (HCCI) engine has found in recent years the interest of the scientific community and automotive industry for their ability to provide high thermal efficiencies and low NOx and particulate emissions. The next step in HCCI engine research is to transfer the accumulated knowledge to industrial applications. Some shortcomings are still to be solved to make these engines suitable for commercialization like, for example, the difficulty in control. Various techniques have been investigated in order to overcome those problems; from variation of the fuel composition to exhaust gas recirculation. The need to change fuel characteristics requires the availability of continuously updated kinetic models optimized under engine conditions. In an operative environment, the calculation speed becomes an essential feature. A key factor for the computational time is the dimension of the kinetic model. One way to achieve reasonable dimensions is to strongly reduce the detailed mechanism. Through the optimization techniques, it is feasible to over reduce the original mechanism and re-optimize the coefficients a posteriori to regain accuracy in the model predictions. Using BlueBellMouse a natural gas fuel reference model as developed by Warnatz et al. has been optimized for a set of HCCI engine experimental cases. The model has then been reduced eliminating redundant species and the corresponding reactions until just the most essential components were left and the model predictions showed high discrepancy with respect to the experimental data. The so obtained skeleton mechanism has then been re-optimized to regain the required accuracy. In addition the optimization of a gasoline fuel reference mechanism containing mixture of n-heptane and iso-octane, toward a set of shock tube experimental cases.},
  author       = {Bellanca, Raffaella},
  issn         = {1102-8718},
  keyword      = {combustion,HCCI,reduction,engine,kinetic,simulation,graphical user interface,GUI,optimization,chemical mechanism,Physics,Fysik,Fysicumarkivet A:2004:Bellanca},
  language     = {eng},
  pages        = {117},
  publisher    = {Combustion Physics, Lund Institute of Technology},
  school       = {Lund University},
  title        = {BlueBellMouse. A Tool for Kinetic Model Development},
  year         = {2004},
}