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Theoretical and Experimental Studies of the Formation of Ionized Gases in Spark Ignition Engines

Reinmann, Raymond LU (1998)
Abstract (Swedish)
Popular Abstract in Swedish

Denna studie är ämnad åt att undersöka joniseringsprocessen i gaser, både teoretiskt och experimentellt. Arbetet är speciellt riktat mot att utöka förståelsen för detta fenomen i förbränningsrummet av en förbränningsmotor. Den intensiva joniseringsprocessen som uppstår till följd av den antändande gnistan har studerats såväl som den svagare joniseringsprocessen som är relaterad till det åtföljande förbränningsförloppet.



Studien av gnistan har omfattat modellering av de viktigaste fenomenen varefter verifikation med hjälp av experiment utförts. Arbetet har lett fram till en praktiskt användbar modell för beräkning av genombrottstid och spänning för ett givet tändsystem. Modellen... (More)
Popular Abstract in Swedish

Denna studie är ämnad åt att undersöka joniseringsprocessen i gaser, både teoretiskt och experimentellt. Arbetet är speciellt riktat mot att utöka förståelsen för detta fenomen i förbränningsrummet av en förbränningsmotor. Den intensiva joniseringsprocessen som uppstår till följd av den antändande gnistan har studerats såväl som den svagare joniseringsprocessen som är relaterad till det åtföljande förbränningsförloppet.



Studien av gnistan har omfattat modellering av de viktigaste fenomenen varefter verifikation med hjälp av experiment utförts. Arbetet har lett fram till en praktiskt användbar modell för beräkning av genombrottstid och spänning för ett givet tändsystem. Modellen kan även ge svar på hur mycket energi som deponerats i gasen mellan tändstiftets elektroder och således är tillgängligt som aktiveringsenergi vid antändning. Resultaten från modellerna överensstämmer i stor utsträckning med de mätningar som utförts. För att understödja såväl förståelsen av processen som helehet som utvecklingen av de enklare modellerna har mer fullständiga modeller utvecklats och använts för att trimma in de antaganden och approximationer som gjorts i de enklare modellerna.



När förbränningsprocessen startats fortgår en joniseringsprocess om än mycket svagare än den som sker under gnistans brinntid. Denna jonisering av gasen gör det möjligt att driva en ström genom densamma. Storleken på strömmen och dess variation med tiden kan då ge viktig information om förbränningens fortskridande. Det generella uppförandet hos denna jonström har framgångsrikt simulerats med hjälp av en modell som beaktar de båda processerna kemi-jonistaion och termisk jonisation. Dessutom har en rad statistiska utvärderingar utförts på experimentella data för att finna yttereligare viktig information i jonströmmen och på så vis även utökat den allmänna förståelsen for problemet. Syftet med denna del av arbetet har varit att förbättra styrningen av förbränningsmotorer, så att motorn kan gå mer optimalt och även klara de skärpta lagkraven för avgasemissioner. (Less)
Abstract
The processes that govern the formation, existence and consumption of ions in gases have been studied both experimentally and theoretically. The aim of the work is targeted at increasing the understanding of these phenomena in the working gases inside an engine. Both the cause and the application of ionized gases inside the cylinder of a spark ignited (SI) engine has been studied.



The spark discharge process that eventually leads to a favorable combustion has been studied in order to determine the total amount of energy that enters the gas. A simplified theoretical model has been developed that includes the most dominant effects. The model includes molecular and atomic processes such as ionization, dissociation and... (More)
The processes that govern the formation, existence and consumption of ions in gases have been studied both experimentally and theoretically. The aim of the work is targeted at increasing the understanding of these phenomena in the working gases inside an engine. Both the cause and the application of ionized gases inside the cylinder of a spark ignited (SI) engine has been studied.



The spark discharge process that eventually leads to a favorable combustion has been studied in order to determine the total amount of energy that enters the gas. A simplified theoretical model has been developed that includes the most dominant effects. The model includes molecular and atomic processes such as ionization, dissociation and thermal heating together with diffusion of cold gas molecules into the hot spark kernel. The energy input is then calculated from the electrical properties of the ignition system and the gas conditions between the electrodes. Electrode effects have not been included since the energy released close to the electrodes to a major extent is lost. In order to gain even more knowledge about the dynamic spark behavior, a hydrodynamic model for the description of the generated flow patterns emanating from a fast spark discharge was used. In addition, a detailed model for the generation of initial breakdown conditions was also used. The experimental techniques that have been used to support the model have been various, e.g. electrical power measurements, calorimetric measurements and interferometric measurements.



The spark, that has been intensively studied, inflames a small region of gas in the vicinity of the electrode gap. This flame kernel will then develop into a propagating flame. While growing, the high gas temperature close to the spark gap reflects the progress of the combustion process. This fact has been used for engine diagnostics by measuring the current flowing through the spark plug gap. The phenomenon has been described in a model for flame ionization in order to deduce the cylinder pressure and the air/fuel ratio in vicinity of spark plug. There are mainly three contributing parameters, which are required for a correct description of the current namely; the ion/electron concentrations, the electric field distribution in space and the drift velocity of the electrons. It has been shown that the current is carried by the electrons to a higher extent than the ions although the electrons are easily attached to electronegative species, such as oxygen (O) and the hydroxyl radical (OH). A detailed chemical kinetic code has been used in order to calculate the concentrations of the most significant species in both the reaction zone and the postflame region. In addition to the theoretical work a large amount of experimental data has been collected for the purpose of model validation and obtaining a deeper understanding. Statistical treatment of the experimental data has also been performed. By this method the influence from some additional parameters such as the amount of EGR and variable fuels have been investigated. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Maly, Rudolf R., Dr. Daimler Benz Research and Technology, Stuttgart
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Thermal Ionization, Calorimetry, Interferometry, Spark Ignition Engine, Current and Voltage Measurements, Engine Control., fluid dynamics, Gases, plasmas, Gaser, plasma, fluiddynamik, Breakdown, Arc, Glow, Flame Ionization, Chemi-Ionization, Spark, Townsend, Fysicumarkivet A:1998:Reinmann
pages
235 pages
publisher
Lund Institute of Technology
defense location
Sal B, Department of Physics
defense date
1998-05-15 13:15
external identifiers
  • other:LUTFD2/TFCP--37--SE/1-71/(1998)
ISSN
1102-8718
ISBN
91-628-2985-8
language
English
LU publication?
yes
id
852521cc-6353-47b5-8bde-989b270c576c (old id 38687)
date added to LUP
2007-10-01 09:22:42
date last changed
2016-09-19 08:44:59
@phdthesis{852521cc-6353-47b5-8bde-989b270c576c,
  abstract     = {The processes that govern the formation, existence and consumption of ions in gases have been studied both experimentally and theoretically. The aim of the work is targeted at increasing the understanding of these phenomena in the working gases inside an engine. Both the cause and the application of ionized gases inside the cylinder of a spark ignited (SI) engine has been studied.<br/><br>
<br/><br>
The spark discharge process that eventually leads to a favorable combustion has been studied in order to determine the total amount of energy that enters the gas. A simplified theoretical model has been developed that includes the most dominant effects. The model includes molecular and atomic processes such as ionization, dissociation and thermal heating together with diffusion of cold gas molecules into the hot spark kernel. The energy input is then calculated from the electrical properties of the ignition system and the gas conditions between the electrodes. Electrode effects have not been included since the energy released close to the electrodes to a major extent is lost. In order to gain even more knowledge about the dynamic spark behavior, a hydrodynamic model for the description of the generated flow patterns emanating from a fast spark discharge was used. In addition, a detailed model for the generation of initial breakdown conditions was also used. The experimental techniques that have been used to support the model have been various, e.g. electrical power measurements, calorimetric measurements and interferometric measurements.<br/><br>
<br/><br>
The spark, that has been intensively studied, inflames a small region of gas in the vicinity of the electrode gap. This flame kernel will then develop into a propagating flame. While growing, the high gas temperature close to the spark gap reflects the progress of the combustion process. This fact has been used for engine diagnostics by measuring the current flowing through the spark plug gap. The phenomenon has been described in a model for flame ionization in order to deduce the cylinder pressure and the air/fuel ratio in vicinity of spark plug. There are mainly three contributing parameters, which are required for a correct description of the current namely; the ion/electron concentrations, the electric field distribution in space and the drift velocity of the electrons. It has been shown that the current is carried by the electrons to a higher extent than the ions although the electrons are easily attached to electronegative species, such as oxygen (O) and the hydroxyl radical (OH). A detailed chemical kinetic code has been used in order to calculate the concentrations of the most significant species in both the reaction zone and the postflame region. In addition to the theoretical work a large amount of experimental data has been collected for the purpose of model validation and obtaining a deeper understanding. Statistical treatment of the experimental data has also been performed. By this method the influence from some additional parameters such as the amount of EGR and variable fuels have been investigated.},
  author       = {Reinmann, Raymond},
  isbn         = {91-628-2985-8},
  issn         = {1102-8718},
  keyword      = {Thermal Ionization,Calorimetry,Interferometry,Spark Ignition Engine,Current and Voltage Measurements,Engine Control.,fluid dynamics,Gases,plasmas,Gaser,plasma,fluiddynamik,Breakdown,Arc,Glow,Flame Ionization,Chemi-Ionization,Spark,Townsend,Fysicumarkivet A:1998:Reinmann},
  language     = {eng},
  pages        = {235},
  publisher    = {Lund Institute of Technology},
  school       = {Lund University},
  title        = {Theoretical and Experimental Studies of the Formation of Ionized Gases in Spark Ignition Engines},
  year         = {1998},
}