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  • Hot-Wire Measurements in a Low Pressure Turbine Linear Cascade
    Publication . Lousada, Mariana Caetano; Bousson, Kouamana; Brojo, Francisco Miguel Ribeiro Proença; Lavagnoli, Sergio
    Numerical simulations are an important analysis and design tool in the turbomachinery industry. The ambition to improve the performance and sustainability of modern aero­engines, combined with the extensive use of numerical simulation, has created new challenges in the development of accurate CFD tools. The turbulence modelling and the lack of well defined boundary conditions are two of the most significant limitations in the application of CFD in turbomachinery flows, with the characteristics of the inlet turbulent flow being usually the biggest unknown. The presented study addresses the application of Hot­Wire Anemometry in a low­density and high­speed flow, at the inlet of a linear cascade representative of a transonic low pressure turbine. In this context, the main objective of this research is the turbulence characterization of the inlet section of the cascade, in terms of turbulence intensity and integral length scales. The Hot­Wire Anemometry is a well known technique for measuring velocity fluctuations. However, measurements in the present conditions feature an increased degree of complexity, due to the compressibility of the flow and the effect of the gas rarefaction. Moreover, few investigations were conducted in such conditions, highlighting a lack of a solid methodology for this kind of application. In the frame of a large EU­funded project, the test campaign took place in the high­speed and low­density wind tunnel S­1/C, located at the von Karman Institute for Fluid Dynamics. A single hot­wire was employed and a recently developed non­dimensional calibration was implemented. The measurements were performed upstream of the cascade with the presence of a passive and an active turbulence generator. For time­average measurements the inlet endwall boundary layer was characterized in terms of mean velocity, integral parameters and wall units. In the first case of the campaign regarding only the passive turbulence generator, three methodologies were compared for the time­resolved measurements. Once the methodology was selected the inlet turbulence intensity, integral length scales and energy spectra were computed. In the second phase of the campaign with both active and passive turbulence generators, a phase locked averaging had to be applied to remove the periodic components of the signal. Eventually, the obtained dataset can be used to define high­order boundary conditions for the validation of high­fidelity numerical tools for turbomachinery applications.
    2022-03-15Master thesis Open access Show more