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978-3-8439-4215-7, Reihe Luftfahrt
Investigation of Turbulent Intra-Fluid Heat Transfer in a Low-Pressure Turbine with Hot-Streak Injection
143 Seiten, Dissertation Universität Stuttgart (2019), Softcover, A5
As a result of the annular combustor design in modern aircraft engines, the temperature field entering the turbine features individual hot streaks which have been shown to adversely affect the aerodynamic performance of the turbine. Simultaneously, the gradient diffusion model for turbulent heat transfer, that is commonly used in practically all commercial CFD codes, is reported to be in many ways deficient. Especially the assumption of a constant turbulent Prandtl number is seen as a potential source of error in many publications. Regarding the phenomenon of hot streaks the influence of turbulent heat transfer could however be essential for the accurate prediction of the hot streak’s attenuation and migration within the turbine, and consequently its adverse effects on the performance of the machine.
In this thesis a state-of-the-art CFD setup is evaluated for a turbine flow featuring hot streaks and the influence of turbulent heat transfer on the results is investigated. To this end, a combined experimental and numerical study is conducted. The experimental part of the study comprises of measurements in a rotating, two-stage, low pressure turbine test rig under realistic high-altitude flight conditions with and without hot streak injection. Measurements include steady-state and time-resolved total temperature area traverses at different positions of the turbine. Additionally, a tracer gas experiment is conducted where the injected hot air is seeded with carbon monoxide resulting in a tracer gas streak. This is done on the basis of the heat and mass transfer analogy, connecting heat and mass transfer due to the similarity of their underlying processes. The numerical part of the study includes in total three URANS simulations. For two simulations of the isothermal and the hot streak case a state-of-the-art setup is used. An additional simulation of the hot streak case is performed with an advanced setup.