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Influence of Combined Inflow Distortions on a Low Pressure Turbine at Low Reynolds Numbers
von Christian SchulzeThe design process of modern low pressure turbines strongly relies on data gathered in highly sophisticated experimental setups. To achieve the best results, effort is put into using high accuracy measurement equipment as well as into the operation of the turbine at realistic cruise conditions with low Reynolds numbers. Thus, realistic flow phenomena can be investigated.
However, in most cases the turbine is investigated using a clean inlet with perfect inflow conditions. In real engine applications the flow field prior to the turbine is affected by upstream components, such as the combustion chamber, the high pressure turbine or the turbine centre frame. Their influences lead to distinct total pressure distortions, higher levels of free-stream turbulence intensity and a decrease in endwall boundary layer thickness. These so-called inflow distortions have previously only been investigated separately in more simple experimental setups. A deeper understanding of their influence on a low pressure turbine at cruise conditions is lacking.
In the present work the influence of combined inflow distortions on a low pressure turbine at low Reynolds numbers is investigated. The turbine rig is operated in an altitude test facility to achieve Reynolds and Mach similarity. Experimental data is gathered with steady and time-resolved measurement equipment throughout the two-stage turbine. The effects on efficiency and the main loss mechanisms are analysed. Furthermore, the analysis of the experimental data is compared to numerical data gained from unsteady CFD calculations.
However, in most cases the turbine is investigated using a clean inlet with perfect inflow conditions. In real engine applications the flow field prior to the turbine is affected by upstream components, such as the combustion chamber, the high pressure turbine or the turbine centre frame. Their influences lead to distinct total pressure distortions, higher levels of free-stream turbulence intensity and a decrease in endwall boundary layer thickness. These so-called inflow distortions have previously only been investigated separately in more simple experimental setups. A deeper understanding of their influence on a low pressure turbine at cruise conditions is lacking.
In the present work the influence of combined inflow distortions on a low pressure turbine at low Reynolds numbers is investigated. The turbine rig is operated in an altitude test facility to achieve Reynolds and Mach similarity. Experimental data is gathered with steady and time-resolved measurement equipment throughout the two-stage turbine. The effects on efficiency and the main loss mechanisms are analysed. Furthermore, the analysis of the experimental data is compared to numerical data gained from unsteady CFD calculations.