End wall and cavity interactions effects on aerodynamic probes for turbine aero testing

This master’s thesis presents an investigation of end wall and cavity effect on probes reading in a turbine rig environment. Probe measurements in aeronautical engine can be challenging due to potential errors, which may affect the accuracy of crucial data used to evaluate engine performance. This could lead to misinterpretations that compromise operational efficiency and aerodynamic projects. Firstly, a CAD model of five-hole probe was developed with Siemens- NX following the real probe used by Avio Aero GE in the test rig. Since experimental calibration, applied to data reduction of CAD probe, leads to deviation; a numerical calibration was carried out. Through CFDpost and python scripts a data reduction was performed by making an area average of the total pressure on different holes, and get interpolated α,ϕ,P0,Ps,M from each numerical calibration map. The impact of end wall on the probe measurements was studied through CFD models: a first one with uniform boundary conditions, with the fivehole probe at different distances from the wall, seeing that the gradients near wall have a non-negligible effect. Then, a second model with rotor exit radial distribution as inlet boundary condition shows the impact of using different boundary conditions. By adding a cavity purge and turbine rear frame (TRF), errors on probe measurement increase more: mainly on yaw and pitch angles, due to an additional flow directly on probe and the back-pressuring of TRF that impact the flow. Finally, a model with cavity purge, TRF, and traverse slot was carried out by moving the probe at different distances from the wall, finding, in addition to the significant impact on measurements, that the slot creates wakes that disturb the flow and cause leakage. This study highlights how the measurements of a probe, mainly of yaw and pitch angles, are impacted by the wall and cavities, so the errors should be taken into account during testing.