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Development of Multi-Dimensional Laser Techniques for In-situ Combustion Diagnostics

Nygren, Jenny LU (2003)
Abstract (Swedish)
Popular Abstract in Swedish

Det har traditionellt sett varit mycket svårt att genomföra förbränningsstudier i motorer, men i och med laserns introduktion har nya möjligheter öppnats. Under de senaste 20 åren har lasern blivit ett allt viktigare hjälpmedel, och ett stort antal laser baserade mätmetoder har utvecklats. Det är nu möjligt att mäta temperaturer, ämneskoncentrationer, hastighetsfält och partikelstorlekar, som tillsammans ger en utförlig bild av förbränningen. Fordonstrafiken ger upphov till en stor del av de miljö- och hälsofarliga ämnen som vi släpper ut i vår omgivning. Därför är det viktigt att satsa på forskning och utveckling inom motorområdet. För att förbättra dagens motorkonstruktioner måste vi förstå vad... (More)
Popular Abstract in Swedish

Det har traditionellt sett varit mycket svårt att genomföra förbränningsstudier i motorer, men i och med laserns introduktion har nya möjligheter öppnats. Under de senaste 20 åren har lasern blivit ett allt viktigare hjälpmedel, och ett stort antal laser baserade mätmetoder har utvecklats. Det är nu möjligt att mäta temperaturer, ämneskoncentrationer, hastighetsfält och partikelstorlekar, som tillsammans ger en utförlig bild av förbränningen. Fordonstrafiken ger upphov till en stor del av de miljö- och hälsofarliga ämnen som vi släpper ut i vår omgivning. Därför är det viktigt att satsa på forskning och utveckling inom motorområdet. För att förbättra dagens motorkonstruktioner måste vi förstå vad som sker under förbränningen. För att förstå och kunna förutse vad som händer finns det idag en mängd modeller för förbränning i bland annat motorer. Det är viktigt att kontrollera om dessa modeller ger korrekta resultat. Därför är kunskapen om hur man mäter temperaturer och koncentrationer av olika ämnen som bildas i själva förbränningsögonblicket viktig. Den mätdata som erhålls vid experimenten jämförs med de resultat som modellerna ger, och är överensstämmelsen god vet man att modellen som byggts upp är en bra beskrivning av det undersökta förbränningsförloppet. Det finns ett flertal anledningar till att mätmetoder med hjälp av laser har blivit så framgångsrika. Först och främst är det för att man kan göra så kallade beröringsfria undersökningar, vilket innebär att förbrännings-förloppet studeras utan att de kemiska och fysikaliska processerna påverkas av mätutrustningen. Sådana mätningar är mycket svåra att göra med konventionella mättekniker, som till exempel temperaturmätning med termoelement. Andra fördelar med laserbaserade tekniker är hög känslighet samt möjligheten att mäta i snabba och turbulenta förlopp. Det finns ett flertal olika sätt att mäta temperatur och koncentration med laserljus. Alla har sina för- och nackdelar: Vissa tekniker är bättre vid högre temperaturer och andra vid lägre, med en del metoder kan man dessutom mäta i flera punkter samtidigt. Gemensamt för alla lasertekniker är dock att man måste nå mätområdet med sin laserstråle. I en öppen flamma är detta enkelt, men när det gäller mätningar inuti motorer innebär det att motortillverkaren måste konstruera en så kallad optisk motor. En sådan motor har fönster så att man både kan skicka in laserstrålarna i cylindern samt få ut mätsignalen som innehåller temperatur- och/eller koncentrations-informationen. För att resultaten från mätningar i en sådan motor ska vara jämförbara med den ursprungliga motorn är det viktigt att den optiska motorn har samma inre geometri (utseende) som den som håller på att utvecklas. Avhandlingen behandlar en grundläggande studie av en laser-baserad teknik för temperaturmätning samt en studie om bränslets fördelning i olika typer av motorer. I delen om temperaturmätning undersöks möjligheten att använda en två-linje fluorescensteknik för att mäta temperaturen i ett område där sotpartiklar är närvarande. Syftet är att undersöka potentialen för att använda tekniken för framtida temperaturmätningar i dieselmotorer. Sotiga områden är ofta problematiska för många lasertekniker, eftersom laserstrålen absorberas av sotet som i sin tur hettas upp, vilket ytterligare stör temperatursignalen. Uppgiften har således varit att undersöka om två-linje fluorescenstekniken påverkas i sotiga områden. Resultatet från undersökningen är att tekniken har god potential för att mäta temperaturer i till exempel dieselmotorer, som producerar mycket sot. Lasermätningarna i olika motorkoncept har också utförts. I dessa har vi studerat hur bränslet transporteras till tändstiftet, bränslets läge i antändningsögonblicket och bränslets konsumtion under själva förbränningen. För att undersöka hur förbränningen i motorn utbreder sig har vi valt att studera en radikal, OH, som bildas i flamfronten. Med hjälp av dessa mätningar fick vi dessutom uppfattning om graden av turbulens under förbränningen; om flamfronten är mycket skrynklig tyder detta på att det har varit mycket turbulens. Mätningarna gav information som leder till ökad förståelse av förbränningsprocessen i motorn. I förlängningen leder detta till en förbättrad motordesign med högre effektivitet och mindre utsläpp som resultat. (Less)
Abstract
Multi-dimensional, laser-based measurements of quantities important for obtaining a better understanding of combustion processes, particularly of temperature and of species distributions, were performed using laser-induced fluorescence (LIF). The main purpose of the temperature experiments was to investigate the potential of employing a two-line atomic fluorescence technique (TLAF), using indium as the tracer species, in sooting environments such as in diesel engines. The initial studies were performed in a laboratory flame in which the amount of soot was varied for investigating whether the technique suffers from strong background radiation due to heated soot particles, absorption of laser wavelengths or interference caused by... (More)
Multi-dimensional, laser-based measurements of quantities important for obtaining a better understanding of combustion processes, particularly of temperature and of species distributions, were performed using laser-induced fluorescence (LIF). The main purpose of the temperature experiments was to investigate the potential of employing a two-line atomic fluorescence technique (TLAF), using indium as the tracer species, in sooting environments such as in diesel engines. The initial studies were performed in a laboratory flame in which the amount of soot was varied for investigating whether the technique suffers from strong background radiation due to heated soot particles, absorption of laser wavelengths or interference caused by poly-aromatic hydrocarbons (PAH). The results indicate In-TLAF thermometry to perform well over a large range of -values. Indium is an attractive tracer candidate since both its excitation and detection wavelengths are in the visible range (410 nm and 451 nm), where absorption by hydrocarbons and other native combustion species was found to be negligible. Because of the oscillator strength of indium being high, the laser energy required is very low. This is an advantage since lasers of high power give rise either to laser-induced incandescence (LII) from soot particles or to strong LIF from PAH. The broad temperature sensitivity range, some 700–3000 K, of the technique when indium atoms are employed allows measurements to be performed in most practical combustion environments. In fuel-rich flames the seeding efficiency also increases, since the loss of active species due to oxidation there plays only a subordinate role. This is an advantage, since it permits sufficient signal-to-noise ratios to be achieved with use of a lower seeding concentration minimising the effects of the seeded species on the combustion chemistry. This makes In-TLAF highly attractive for thermometry applications in fuel-rich and turbulent combustion processes. In-TLAF may well prove to be a good candidate for future measurements in diesel engines, where temperature information is of crucial importance for further development of engine design.



Engine measurements were performed using a high-speed laser and camera system. The laser cluster and the framing camera employed are able to capture eight images within 50 , making studies of time and spatially resolved combustion events possible. Concentration measurements were performed in engines of three types; a spark-ignition (SI) engine, a gasoline-direct-injection (GDI) engine and a homogeneous-charge- compression-ignition (HCCI) engine. The high-speed system was used so as to be able to perform true single-cycle-resolved measurements in the engines, all the data being recorded in a single engine cycle without any averaging effects caused by cycle-to-cycle variations. Studies of the sort are impossible to perform using a system that captures only single-shot images from subsequent cycles. The detection of single-cycle-resolved images of fuel and OH distributions was performed initially in a lab-top SI-engine with the aim of investigating the applicability of the technique. The same technique was then applied to a GDI engine at the Volvo Car Corporation. In that engine, fuel transport from the start of injection to the time of ignition was studied, along with flame propagation using both OH and fuel-tracer PLIF. The onset and development of combustion was also studied in the HCCI engine located at the Division of Combustion Engines in Lund, using fuel-tracer PLIF. The main goal there being to capture the appearance and growth of auto-ignition kernels for investigating whether any flame propagation occurs in a combustion process of this type. Cycle-to-cycle variations were also studied by comparing different cycles. To investigate whether a fuel island in a two-dimensional image is isolated or simply looks like an island due to wrinkling effects in and out the laser sheet, an experiment was performed in which 3D data was recorded. The topology of the fuel distribution can also be studied by obtaining measurements in three dimensions. From such experimental data, spatial gradients in all three directions can be calculated, providing information of interesting to modellers. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Ph. D O Keller, Jay, Sandia National Laboratories
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Laser Diagnsotics, Visualisation, Laser technology, Laserteknik, Motors and propulsion systems, Motorer, framdrivningssystem, Combustion, Temperature, Fysicumarkivet A:2003:Nygren
pages
191 pages
publisher
KFS AB
defense location
Department of Physics, B hall
defense date
2003-02-21 10:15
ISSN
1102-8718
ISBN
91-628-5506-9
language
English
LU publication?
yes
id
6a9d4b40-da7a-4bd8-9282-fbc4e880a770 (old id 465417)
date added to LUP
2007-09-28 13:07:50
date last changed
2016-09-19 08:44:53
@phdthesis{6a9d4b40-da7a-4bd8-9282-fbc4e880a770,
  abstract     = {Multi-dimensional, laser-based measurements of quantities important for obtaining a better understanding of combustion processes, particularly of temperature and of species distributions, were performed using laser-induced fluorescence (LIF). The main purpose of the temperature experiments was to investigate the potential of employing a two-line atomic fluorescence technique (TLAF), using indium as the tracer species, in sooting environments such as in diesel engines. The initial studies were performed in a laboratory flame in which the amount of soot was varied for investigating whether the technique suffers from strong background radiation due to heated soot particles, absorption of laser wavelengths or interference caused by poly-aromatic hydrocarbons (PAH). The results indicate In-TLAF thermometry to perform well over a large range of -values. Indium is an attractive tracer candidate since both its excitation and detection wavelengths are in the visible range (410 nm and 451 nm), where absorption by hydrocarbons and other native combustion species was found to be negligible. Because of the oscillator strength of indium being high, the laser energy required is very low. This is an advantage since lasers of high power give rise either to laser-induced incandescence (LII) from soot particles or to strong LIF from PAH. The broad temperature sensitivity range, some 700–3000 K, of the technique when indium atoms are employed allows measurements to be performed in most practical combustion environments. In fuel-rich flames the seeding efficiency also increases, since the loss of active species due to oxidation there plays only a subordinate role. This is an advantage, since it permits sufficient signal-to-noise ratios to be achieved with use of a lower seeding concentration minimising the effects of the seeded species on the combustion chemistry. This makes In-TLAF highly attractive for thermometry applications in fuel-rich and turbulent combustion processes. In-TLAF may well prove to be a good candidate for future measurements in diesel engines, where temperature information is of crucial importance for further development of engine design.<br/><br>
<br/><br>
Engine measurements were performed using a high-speed laser and camera system. The laser cluster and the framing camera employed are able to capture eight images within 50 , making studies of time and spatially resolved combustion events possible. Concentration measurements were performed in engines of three types; a spark-ignition (SI) engine, a gasoline-direct-injection (GDI) engine and a homogeneous-charge- compression-ignition (HCCI) engine. The high-speed system was used so as to be able to perform true single-cycle-resolved measurements in the engines, all the data being recorded in a single engine cycle without any averaging effects caused by cycle-to-cycle variations. Studies of the sort are impossible to perform using a system that captures only single-shot images from subsequent cycles. The detection of single-cycle-resolved images of fuel and OH distributions was performed initially in a lab-top SI-engine with the aim of investigating the applicability of the technique. The same technique was then applied to a GDI engine at the Volvo Car Corporation. In that engine, fuel transport from the start of injection to the time of ignition was studied, along with flame propagation using both OH and fuel-tracer PLIF. The onset and development of combustion was also studied in the HCCI engine located at the Division of Combustion Engines in Lund, using fuel-tracer PLIF. The main goal there being to capture the appearance and growth of auto-ignition kernels for investigating whether any flame propagation occurs in a combustion process of this type. Cycle-to-cycle variations were also studied by comparing different cycles. To investigate whether a fuel island in a two-dimensional image is isolated or simply looks like an island due to wrinkling effects in and out the laser sheet, an experiment was performed in which 3D data was recorded. The topology of the fuel distribution can also be studied by obtaining measurements in three dimensions. From such experimental data, spatial gradients in all three directions can be calculated, providing information of interesting to modellers.},
  author       = {Nygren, Jenny},
  isbn         = {91-628-5506-9},
  issn         = {1102-8718},
  keyword      = {Laser Diagnsotics,Visualisation,Laser technology,Laserteknik,Motors and propulsion systems,Motorer,framdrivningssystem,Combustion,Temperature,Fysicumarkivet A:2003:Nygren},
  language     = {eng},
  pages        = {191},
  publisher    = {KFS AB},
  school       = {Lund University},
  title        = {Development of Multi-Dimensional Laser Techniques for In-situ Combustion Diagnostics},
  year         = {2003},
}