ISBN 978-3-8439-5430-3

978-3-8439-5430-3, Reihe Thermodynamik

Florian Seibold
Experimental and Numerical Investigation of the Flow and Heat Transfer in Convergent Swirl Chambers

202 Seiten, Dissertation Universität Stuttgart (2024), Softcover, A5

Zusammenfassung / Abstract

Gas turbines used for aircraft propulsion or power generation require efficient cooling, especially of the turbine components. One promising technique for internal cooling of turbine blade leading edges is the use of swirl flows in cyclone systems. Real turbine blades mostly feature a decreasing cross-section from hub to tip, making convergent swirl chambers necessary. Based on this premise, the current thesis presents an extensive parameter study to analyze the effect of swirl chamber convergence. For this purpose, a reference chamber with constant diameter was compared to three swirl chambers with linearly decreasing diameters and convergence angles of 0.42 deg, 0.61 deg and 0.72 deg. Additionally, one swirl tube with a non-linear, hyperbolic diameter decrease was considered. Numerical studies were conducted as Delayed Detached Eddy Simulations and the heat transfer was measured in the experiment using the transient liquid crystal thermography.

Convergent swirl chambers provoked a flow acceleration both in the axial direction and in the circumferential direction. Within the circumferential flow field, a characteristic pattern developed that proved to be largely independent of tube convergence and consisted of a Rankine vortex. The axial flow field was categorized into three different regimes depending on the presence and the shape of an axial backflow. Convergent swirl chambers suppressed this axial backflow such that a robust flow was achieved. However, particularly high friction factors were found. The heat transfer showed overall high magnitudes, but Nusselt numbers dropped with swirl chamber convergence. In addition, the stability of swirl chamber flows was analyzed based on the Second Law of Thermodynamics. Accordingly, instabilities were detected in the axial and circumferential flow fields and were associated with variations in the Rankine vortex and axial flow regime.