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ISBN 9783843922500

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978-3-8439-2250-0, Reihe Raumfahrt

Thomas Fiala
Radiation from High Pressure Hydrogen-Oxygen Flames and its Use in Assessing Rocket Combustion Instability

151 Seiten, Dissertation Technische Universität München (2015), Softcover, A5

Zusammenfassung / Abstract

Visible and ultraviolet radiation is a readily measurable property of a flame. This study investigates the radiation of non-premixed hydrogen-oxygen flames at elevated pressure, which often power liquid rocket engines. Such flames mainly emit UV radiation from excited OH* radicals and exhibit a broad-band radiation peaking in the blue spectrum. Both types of radiation are examined experimentally and numerically in a laminar jet flame at pressures ranging from 1 bar to 40 bar. Emission and absorption are measured spectrally and spatially. Physical models for numerically simulating either radiation are summarized and extended by new methods. Their practical use and limitations are assessed by comparison with experimental data. Especially the difference between chemical an thermal excitation of OH* as well as its self-absorption are scrutinized. Additionally, the radiation is compared to the volumetric heat release rate, which is an important parameter in studying combustion instabilities. Generally, both quantities are found to be quantitatively uncorrelated for non-premixed flames. Studies of counterflow flame ensembles reveal that in coarsely resolved turbulent flames with low optical density, a qualitative relation between line-of-sight integrated radiation and heat release rate exists. To quantitatively measure heat release rate, radiation measurements must be corrected for the influence of flame straining. Due to this fact, alternate methods are presented to assess combustion instabilities by radiation data.