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Laser Diagnostics in Combustion - Elastic Scattering and Picosecond Laser-Induced Fluorescence

Ossler, Frederik LU (1999)
Abstract (Swedish)
Popular Abstract in Swedish

Laserbaserd Förbränningsdiagnostik - Elastisk Spridning och Pikosekundlaserinducerad fluorescens



Elastisk spridning och Lorenz-Mie (LM) teorin används för att karakterisera droppar av organiskt bränlse med en diameter kring 1 mikrometer. Beräkningar baserade på LM-teorin visar att det spridda ljuset i sido- och bakåtrikningen kan användas för omisskänslig detektion av ensembler av homogena droppar av organiskt material med en diameter kring 1 mikrometer (storleksparameter mellan 2 och 6). En signatur framträder i polarisationskvoten (horisontal/vertikal) med ett värde klart större än ett i motsats till fallet med större droppar, som p.g.a "regnbågseffekten" har en kvot klart... (More)
Popular Abstract in Swedish

Laserbaserd Förbränningsdiagnostik - Elastisk Spridning och Pikosekundlaserinducerad fluorescens



Elastisk spridning och Lorenz-Mie (LM) teorin används för att karakterisera droppar av organiskt bränlse med en diameter kring 1 mikrometer. Beräkningar baserade på LM-teorin visar att det spridda ljuset i sido- och bakåtrikningen kan användas för omisskänslig detektion av ensembler av homogena droppar av organiskt material med en diameter kring 1 mikrometer (storleksparameter mellan 2 och 6). En signatur framträder i polarisationskvoten (horisontal/vertikal) med ett värde klart större än ett i motsats till fallet med större droppar, som p.g.a "regnbågseffekten" har en kvot klart mindre än ett. En jämförelse mellan mätningar och LM-beräknngar visade att ett stort antal droppar med diametern midre än en mikrometer fanns närvarande i aerosoler och välatomiserade sprejer.



En 3-D teknik baserad på pikosekundlaser och streak camera har demonstrerats för mätningar på snabba och turbulenta tvåfasflöden. Hela 3-D informationen erhölls på en tid mindre än 15 nanosekunder.



En 2-D teknik baserad på pikosekundlaser och streak camera har demonstrerats för livstidsmätningar på statiska objekt. En analys indikerar möjligheten för användandet av tekniken på livstider kring 1 pikosekund eller därunder vid utnyttjandet av femtosekundlaser och femtosekund streak camera. Tekniken kan i princip även användas på dynamiska förlopp när två detektorer används.



Mätningar av fluorescenslivstider för väte och syreatomer i flammor vid atmosfärstryck visar behovet av lasrar med passande spektrala egenskaper vad avser stabilitet och linjebredd. I fallet för syreatomer finns även behovet av detektorer med tillräcklig känslighet i det infraröda området.



Fluorescenslivstiderna för aceton och 3-pentanon har upmätts för gasformiga blandningar innehållande kvävgas och luft vid olika tryck (0.01-10 bar) och temperatur (323-723 K). Den effektiva livstiden ökar generellt med stigande gastryck och sjunker med stigande temperatur på olika sätt för de två ketonerna. Detta ger vissa implikationer för deras utnyttjande vid förbränningsrelaterade studier.



Fluorescensen från aromatiska kolväten i gasfas vid atmosförstryck har studerats vid höga temperaturer. Livstiderna minskade generellt sett mellan en och två storleksordningar då temperaturen höjdes från 400 till 1200 K. Beroendet av fluorescensen på temperaturen och syrehalten indikerar att den beror på sekvenser och tillståndtätheten hos vibrationstillstånden. Resultaten ger också vissa implikationer på utnyttjandet av fluorescensen vid förbränningsrelaterade studier. (Less)
Abstract
Elastic scattering and the Lorenz-Mie (LM) theory in particular is used for the characterization of sub-micron- and micron-sized droplets of organic fuels in sprays and aerosols. Calculations on the Lorenz- Mie theory show that backward-sideward scattered visible radiation can be used for unambiguous detection of ensembles of homogeneous droplets of organic substances with diameters around 1 micrometer (size parameter between 2 and 6). A backward feature in the polarization ratio appears with a value considerably higher than one, on the opposite to the case of the rainbow observed for larger droplets. A comparison between measurements and LM calculations showed that a large amount of droplets in aerosols and well-atomized sprays were... (More)
Elastic scattering and the Lorenz-Mie (LM) theory in particular is used for the characterization of sub-micron- and micron-sized droplets of organic fuels in sprays and aerosols. Calculations on the Lorenz- Mie theory show that backward-sideward scattered visible radiation can be used for unambiguous detection of ensembles of homogeneous droplets of organic substances with diameters around 1 micrometer (size parameter between 2 and 6). A backward feature in the polarization ratio appears with a value considerably higher than one, on the opposite to the case of the rainbow observed for larger droplets. A comparison between measurements and LM calculations showed that a large amount of droplets in aerosols and well-atomized sprays were smaller than one micrometer in diameter. The LM theory was also used to characterize different size groups in a burning spray.



A 3 – D technique based on a picosecond laser and a streak camera was demonstrated for measurements of fast and turbulent biphase flows. The entire 3 – D information was obtained within a time-span of less than 15 nanoseconds.



A 2 – D technique for lifetime measurements based on a picosecond laser and a streak camera has been demonstrated on static objects. An analysis indicates that the technique may be applied to measurements of lifetimes around or below one picosecond employing femtosecond lasers and femtosecond streak-cameras. The technique may in princple be used to study dynamic systems when two detectors are used.



Fluorescence lifetime measurements on hydrogen and oxygen atoms in flames at atmospheric pressure demonstrate the need of lasers with suiting spectral properties such as jitter and linewidth and the need of detectors with high sensitivity in the near IR in the case of oxygen atoms.



The fluorescence lifetimes of gas phase acetone and 3-pentanone at 266 nm excitation wavelength have been measured for mixtures with nitrogen and air at temperatures between 323 and 723 K and pressures between 0.01 and 10 bar. The effective lifetimes generally decrease with temperature and increase with pressure and in different ways for the two substances which gives implications of their use to combustion related studies.



The fluorescence emission from gas phase aromatic hydrocarbons has been studied at elevated temperatures and at atmospheric pressure for different concentrations of oxygen (0-10%). Picosecond laser radiation at 266 nm was used for the excitation. The lifetimes for most of the substances decreased between one and two orders of magnitude when the temperature was increased between 400 and 1200 K. The dependence of the lifetimes on temperature and oxygen concentration indicate that the relaxation dynamics is determined by sequences and the density of vibrational states. The results give also some implications to combustion related diagnostics. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Linne, Mark A., Colorado School of Mines, Div. of Mech. Engineering, GOLDEN, CO 80401, U.S.A
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Spray, Picosecond laser, Streak camera, Time resolved, Fluorescence lifetimes, 3 – D flow imaging, 2 - D lifetime imaging, Pressure, Temperature, Hydrogen atoms, Oxygen atoms, 3-pentanone, Acetone, Lorenz-Mie theory, Aerosol, Fysicumarkivet A:1999:Ossler, Scattering, Fysik, Physics, Polycyclic aromatic hydrocarbons.
pages
167 pages
publisher
Division of Combustion Physics, Department of Physics, Lund University
defense location
Hörsal B, Department of Physics
defense date
1999-06-04 10:15
external identifiers
  • other:LUTFD2"/TFCP -- 47 -- SE
ISBN
91-628-3628-5
language
English
LU publication?
yes
id
98209d0f-f898-4e5e-99e8-b9686fc12203 (old id 39745)
date added to LUP
2007-09-28 13:39:38
date last changed
2016-09-19 08:45:12
@phdthesis{98209d0f-f898-4e5e-99e8-b9686fc12203,
  abstract     = {Elastic scattering and the Lorenz-Mie (LM) theory in particular is used for the characterization of sub-micron- and micron-sized droplets of organic fuels in sprays and aerosols. Calculations on the Lorenz- Mie theory show that backward-sideward scattered visible radiation can be used for unambiguous detection of ensembles of homogeneous droplets of organic substances with diameters around 1 micrometer (size parameter between 2 and 6). A backward feature in the polarization ratio appears with a value considerably higher than one, on the opposite to the case of the rainbow observed for larger droplets. A comparison between measurements and LM calculations showed that a large amount of droplets in aerosols and well-atomized sprays were smaller than one micrometer in diameter. The LM theory was also used to characterize different size groups in a burning spray.<br/><br>
<br/><br>
A 3 – D technique based on a picosecond laser and a streak camera was demonstrated for measurements of fast and turbulent biphase flows. The entire 3 – D information was obtained within a time-span of less than 15 nanoseconds.<br/><br>
<br/><br>
A 2 – D technique for lifetime measurements based on a picosecond laser and a streak camera has been demonstrated on static objects. An analysis indicates that the technique may be applied to measurements of lifetimes around or below one picosecond employing femtosecond lasers and femtosecond streak-cameras. The technique may in princple be used to study dynamic systems when two detectors are used.<br/><br>
<br/><br>
Fluorescence lifetime measurements on hydrogen and oxygen atoms in flames at atmospheric pressure demonstrate the need of lasers with suiting spectral properties such as jitter and linewidth and the need of detectors with high sensitivity in the near IR in the case of oxygen atoms.<br/><br>
<br/><br>
The fluorescence lifetimes of gas phase acetone and 3-pentanone at 266 nm excitation wavelength have been measured for mixtures with nitrogen and air at temperatures between 323 and 723 K and pressures between 0.01 and 10 bar. The effective lifetimes generally decrease with temperature and increase with pressure and in different ways for the two substances which gives implications of their use to combustion related studies.<br/><br>
<br/><br>
The fluorescence emission from gas phase aromatic hydrocarbons has been studied at elevated temperatures and at atmospheric pressure for different concentrations of oxygen (0-10%). Picosecond laser radiation at 266 nm was used for the excitation. The lifetimes for most of the substances decreased between one and two orders of magnitude when the temperature was increased between 400 and 1200 K. The dependence of the lifetimes on temperature and oxygen concentration indicate that the relaxation dynamics is determined by sequences and the density of vibrational states. The results give also some implications to combustion related diagnostics.},
  author       = {Ossler, Frederik},
  isbn         = {91-628-3628-5},
  keyword      = {Spray,Picosecond laser,Streak camera,Time resolved,Fluorescence lifetimes,3 – D flow imaging,2 - D lifetime imaging,Pressure,Temperature,Hydrogen atoms,Oxygen atoms,3-pentanone,Acetone,Lorenz-Mie theory,Aerosol,Fysicumarkivet A:1999:Ossler,Scattering,Fysik,Physics,Polycyclic aromatic hydrocarbons.},
  language     = {eng},
  pages        = {167},
  publisher    = {Division of Combustion Physics, Department of Physics, Lund University},
  school       = {Lund University},
  title        = {Laser Diagnostics in Combustion - Elastic Scattering and Picosecond Laser-Induced Fluorescence},
  year         = {1999},
}