Analysis tools for the unsteady interactions in a counter-rotating two-spool turbine rig

Experimental Thermal and Fluid Science, Volume 42, October 2012, Pages 248-257
Davide Lengani, Cornelia Santner, Rosario Spataro, Emil Gottlich

Inst. f. Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Inffeldgasse 25/A, A-8010 Graz, Austria

Abstract

Counter-rotating turbines represent the state of the art of actual and future aero-engines, built for a considerable reduction of weight and fuel consumption. However, in the open literature there is a limited number of experimental and computational research about the unsteady interactions in such complex configurations. The paper presents an experimental investigation on the two-spool counter-rotating transonic turbine at Graz University of Technology. The rig was designed in cooperation with MTU Aero Engines and Volvo Aero and considerable efforts were put on the adjustment of all relevant model parameters. The test setup consists of a high pressure (HP) stage, a diffusing mid turbine frame with turning struts and a shrouded low pressure (LP) rotor.

A two-sensor fast response aerodynamic pressure probe (2S-FRAPP) has been employed to provide time-resolved aerodynamic area traverses downstream of the LP turbine. Structures at the blade passing frequency of each rotor are resolved by the use of the shaft encoders. Furthermore, a newly developed phase averaging procedure is introduced to take into account the combined rotor–rotor interactions. Different reconstructions of the time resolved flow field are then presented in the paper, where a detailed description of the post-processing tools and their interpretation is provided.

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Additional Information

The analysis method discussed in the paper is aimed at the interpretation of unsteady data in multi-spool turbomachinery. The discussion is focused on the aerodynamic measurements performed in the two-spool counter-rotating turbine rig of the Graz University of Technology. Furthermore, the post-processing tools presented in the paper may be applied to both numerical simulations and measurements and they may be also used for the quantification of acoustic emissions and mechanical stresses. In fact, these tools help isolating the unsteadiness induced by the two rotors and by their interactions. Therefore, they make clear which aerodynamic interaction may cause excessive vibration or high noise.

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