Unsteady Work Processes Within a Low Pressure Turbine Vane Passage

A two-stage low pressure turbine is tested within the co-operation project between the Institute of Aircraft Propulsion Systems (ILA) and MTU Aero Engines GmbH. With experimental data taken in the altitude test facility this study aims to analyze the origin and effect of unsteady pressure fluctuations causing unsteady work in the second stator vane. Measurements at aerodynamic design conditions cover steady and unsteady surface pressure data on the mid span streamline position. Unsteady pressure fluctuations are identified close to the throat plane area, which are influenced by both upstream and downstream events such as wake and potential field interaction. Upstream moving static pressure waves can be identified. To support the experimental results, URANS CFD predictions of the whole turbine configuration were performed. The numerical approach is suitable to reproduce the observed phenomena and allows a deeper investigation. The observed pressure pulsations influence the local unsteady work done to and by the fluid. An evaluation of particle paths in the second stator vane indicates an isentropic energy transfer from free stream to wake fluid. Due to this unsteady energy exchange the momentum deficit of the wake gets reduced, resulting in a potential benefit on the mixing loss.Copyright © 2013 by ASME