ISBN 978-3-8439-4059-7

978-3-8439-4059-7, Reihe Thermodynamik

Steffen Baab
Quantitative Diagnostics and Thermodynamic Modelling of Fluid Jets with Reservoir States at Supercritical Pressure

167 Seiten, Dissertation Universität Stuttgart (2019), Softcover, A5

Zusammenfassung / Abstract

The present thesis investigates the disintegration and mixing process of fluid jets under near-critical thermodynamic conditions. Systematic experimental analysis and thermodynamic modelling were performed for a wide range of fluid injections with reservoir states at supercritical pressure with respect to the injectant. The observed disintegration phenomena comprise both single- and two-phase jet breakup being relevant for a variety of future engine concepts. Three fundamentally different measurement techniques were applied to create a comprehensive experimental database. A simultaneous shadowgraphy and light scattering technique was developed that allowed to characterise two-phase regions embedded in the near-critical fluid jets. Furthermore, comprehensive measurements with laser-induced thermal acoustics (LITA), a four wave mixing technique, were firstly realised for non-isothermal jet mixing zones. As a result, quantitative speed of sound data were acquired for single-phase mixing zones at various conditions. In combination with thermodynamic models, this provided a quantitative characterisation of the flow field quantities. This thesis contributes to the fundamental understanding of jet disintegration and mixture preparation under near-critical thermodynamic conditions – a promising improvement to combustion-based propulsion engines. The presented data are particularly suitable for the validation of numerical simulations. Ultimately, the outcomes of this work facilitate the choice of proper numerical simulation approaches for both single- and two-phase mixing close to the critical point. This will support the development and design of existing and future combustion-based propulsion engine concepts.