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Experimental Investigation of Flame-Wall Interaction by Laser-based Diagnostics

Kosaka, Hidemasa (2018):
Experimental Investigation of Flame-Wall Interaction by Laser-based Diagnostics.
Darmstadt, Technische Universität, [Online-Edition: https://tuprints.ulb.tu-darmstadt.de/8409],
[Ph.D. Thesis]

Abstract

Flame quenching resulting from flame-wall interactions (FWIs) is important in several thermochemical processes of practical relevance, such as internal combustion engines. Even though FWIs are restricted to regions close to walls of a combustion chamber, they are crucial for wall heat fluxes and unburned hydrocarbon emissions. This experimental work is intended to investigate parametric sensitivities that influence flame quenching at walls and to better understand the influence of non-adiabaticity upon the flame structure. This work uses quantitative and semi-quantitative laser-based diagnostics with high temporal and spatial resolution simultaneously. Experiments are performed on a generic burner with side-wall quenching configurations, where a branch of a V-flame interacts with a laterally oriented wall. Laminar and turbulent boundary conditions are generated for various wall temperatures and two different fuels (methane and dimethyl ether). To investigate the influence of wall heat flux on flame quenching, coherent anti-Stokes Raman spectroscopy (CARS) and phosphor thermometry are combined. From the measurements, gas and wall temperature profiles, wall heat fluxes and quenching distances are deduced and correlated. A further measurement of thermochemical states that provide the opportunity to look at the flame dynamics with flame chemistry. The simultaneous measurement of CARS (for the gas temperature) and laser-induced fluorescence (LIF) of carbon monoxide (CO) (for the CO concentration) are applied. Above all, an influence of the time scales of heat transfer on CO chemistry is shown. Furthermore, simultaneous planar LIF of the formaldehyde molecule and the hydroxyl radical are used to image local heat release rate (HRR) distributions. In the turbulent case, flame fluctuations prevail in the FWI zone and are analyzed statistically regarding flame curvature. The correlation of heat release rate, flame curvature and wall-normal distance is investigated using the instantaneous HRR images for different wall temperatures and equivalence ratios. Finally, the feasibility study of the near-wall Raman spectroscopy is carried out. Raman spectroscopy is a promising technique to quantify combustion-related species simultaneously. However, especially near the wall, scattering and reflections from the wall are even higher than that of the other measurement techniques. The purpose of this feasibility study is to characterize the Raman signal quality near the wall. The resulting signal-to-noise ratio is found to be suitable for further measurements.

Item Type: Ph.D. Thesis
Erschienen: 2018
Creators: Kosaka, Hidemasa
Title: Experimental Investigation of Flame-Wall Interaction by Laser-based Diagnostics
Language: English
Abstract:

Flame quenching resulting from flame-wall interactions (FWIs) is important in several thermochemical processes of practical relevance, such as internal combustion engines. Even though FWIs are restricted to regions close to walls of a combustion chamber, they are crucial for wall heat fluxes and unburned hydrocarbon emissions. This experimental work is intended to investigate parametric sensitivities that influence flame quenching at walls and to better understand the influence of non-adiabaticity upon the flame structure. This work uses quantitative and semi-quantitative laser-based diagnostics with high temporal and spatial resolution simultaneously. Experiments are performed on a generic burner with side-wall quenching configurations, where a branch of a V-flame interacts with a laterally oriented wall. Laminar and turbulent boundary conditions are generated for various wall temperatures and two different fuels (methane and dimethyl ether). To investigate the influence of wall heat flux on flame quenching, coherent anti-Stokes Raman spectroscopy (CARS) and phosphor thermometry are combined. From the measurements, gas and wall temperature profiles, wall heat fluxes and quenching distances are deduced and correlated. A further measurement of thermochemical states that provide the opportunity to look at the flame dynamics with flame chemistry. The simultaneous measurement of CARS (for the gas temperature) and laser-induced fluorescence (LIF) of carbon monoxide (CO) (for the CO concentration) are applied. Above all, an influence of the time scales of heat transfer on CO chemistry is shown. Furthermore, simultaneous planar LIF of the formaldehyde molecule and the hydroxyl radical are used to image local heat release rate (HRR) distributions. In the turbulent case, flame fluctuations prevail in the FWI zone and are analyzed statistically regarding flame curvature. The correlation of heat release rate, flame curvature and wall-normal distance is investigated using the instantaneous HRR images for different wall temperatures and equivalence ratios. Finally, the feasibility study of the near-wall Raman spectroscopy is carried out. Raman spectroscopy is a promising technique to quantify combustion-related species simultaneously. However, especially near the wall, scattering and reflections from the wall are even higher than that of the other measurement techniques. The purpose of this feasibility study is to characterize the Raman signal quality near the wall. The resulting signal-to-noise ratio is found to be suitable for further measurements.

Place of Publication: Darmstadt
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Institute of Reactive Flows and Diagnostics (RSM)
Date Deposited: 10 Mar 2019 20:55
Official URL: https://tuprints.ulb.tu-darmstadt.de/8409
URN: urn:nbn:de:tuda-tuprints-84092
Referees: Dreizler, Prof. Dr. Andreas and Hasse, Prof. Dr. Christian
Refereed / Verteidigung / mdl. Prüfung: 23 January 2019
Alternative Abstract:
Alternative abstract Language
Flammenverlöschen, das aus Flamme-Wand-Interaktionen (FWI) resultiert, ist in einer Vielzahl von technischen Prozessen wie z.B. in Verbrennungsmotoren, von praktischer Relevanz. Obwohl FWI auf Bereiche in der Nähe von Wänden einer Brennkammer beschränkt sind, sind sie entscheidend für die Wandwärmflüsse und die Bildung unverbrannter Kohlenwasserstoffe. Diese experimentelle Studie soll parametrische Sensitivitäten untersuchen, die das Flammenverlöschen an Wänden beeinflussen, und den Einfluss der Nichtadiabatizität auf die Flammenstruktur besser verstehen. Diese Arbeit beinhaltet quantitative und semiquantitative Messungen mit gleichzeitig hoher zeitlicher und räumlicher Auflösung. Die Experimente werden an einem generischen Brenner durchgeführt, bei dem ein Zweig einer V-Flamme mit einer seitlich orientierten Wand interagiert. Laminare und turbulente Randbedingungen werden für verschiedene Wandtemperaturen und zwei unterschiedliche Brennstoffe (Methan und Dimethylether) erzeugt. Um den Einfluss des Wandwärmestroms auf das Flammenverlöschen zu untersuchen, werden kohärente Anti-Stokes-Raman-Spektroskopie (CARS) und Phosphorthermometrie kombiniert. Aus den Messungen werden Wandwärmeströme und Verlöschabstände abgeleitet und korreliert. Die weitere Messung thermochemischer Zustände bietet die Möglichkeit, die Flammendynamik mit der Flammenchemie zu untersuchen. Dazu wird die gleichzeitige Messung der Gastemperatur mittels CARS und der CO-Konzentration mittels laserinduzierte Fluoreszenz (LIF) von CO genuzt. Es zeigt sich ein Einfluss der Zeitskalen der Wärmeübertragung auf die COChemie. Außerdem werden simultane planare LIF-Messungen des Formaldehyd und des Hydroxyl-Radikals verwendet, um Verteilungen der lokalen Wärmefreisetzungsrate (HRR) abzubilden. Im turbulenten Fall sind Flammenschwankungen in der FWI-Zone vorherrschend und werden hinsichtlich die Korrelation von HRR, Flammenkrümmung und Wandnormalenabstand statistisch analysiert. Schließlich wird die Machbarkeitsstudie der wandnahen Raman-Spektroskopie vorgestellt. Die Raman-Spektroskopie ist eine vielversprechende Methode zur gleichzeitigen Quantifizierung verbrennungsrelevante Spezies. Verglichen mit der Signalstärke sind jedoch insbesondere in Wandnähe die Streuungen und Reflexionen an der Wand stärker als bei den anderen Messtechniken. Ziel dieser Machbarkeitsstudie ist es, die Raman-Signalqualität in Wandnähe zu charakterisieren. Das resultierende Signal-Rausch-Verhältnis erscheint für weitere Messungen als geeignet.German
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