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ISBN 9783843927123

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978-3-8439-2712-3, Reihe Strömungsmechanik

Michael Keller
Numerical Investigation of Gaseous Film and Effusion Cooling in Supersonic Boundary-Layer Flows

143 Seiten, Dissertation Universität Stuttgart (2016), Softcover, A5

Zusammenfassung / Abstract

The hot combustion gases of next-generation rocket engines generate heat loads that significantly exceed the temperature limits of today's available materials. A promising approach to protect the thermally stressed nozzle liner is the blowing of a coolant into the hot main flow. In order to improve the understanding of the highly complex mixing phenomena, cooling-gas blowing into generic supersonic boundary-layer flows is investigated numerically. Binary gas-mixture flows neglecting chemical reactions are considered in this work and the governing equations of the flow are solved with an in-house high-order finite-difference code. The numerical procedure - direct numerical simulation - is verified with air-in-air film-cooling results obtained by the proven single-species code version and validated with external foreign-gas film-cooling experiments and simulations.

The gaseous cooling film is generated by blowing into the boundary layer through a single discrete spanwise slit or row of holes (film cooling), or by blowing through multiple rows of closely spaced slits or holes (effusion cooling). The blowing is realized either by prescribing a fixed distribution of the cooling-gas mass flux, mass fraction, and temperature at the orifice location (modeled blowing), or by including the blowing channel/pipe with a constant plenum pressure, mass fraction, and temperature at its lower end (simulated blowing). For surface cooling, an enhanced mixing of the coolant and the main flow is disadvantageous. Various influencing parameters are studied. Here, the strongest impact on the cooling effectiveness show the cooling-gas type and the boundary-layer state - laminar or turbulent. Other important parameters are the inclination angle, the blowing-jet spacing, and the blowing modeling.