Unsteady Flow Evolution Through a Turning Midturbine Frame Part 2: Spectral Analysis

This paper analyzes the propagation of the aerodynamic deterministic stresses through a two-spool counter-rotating transonic turbine at Graz University of Technology. The test setup consists of a high-pressure stage, a diffusing midturbine frame with turning struts and a counter-rotating low-pressur...

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Bibliographic Details
Published in:Journal of propulsion and power 2015-11, Vol.31 (6), p.1597-1606
Main Authors: Lengani, D, Spataro, R, Peterleithner, J, Göttlich, E
Format: Article
Language:English
Subjects:
Aerodynamics
Computational fluid dynamics
Decomposition
Ducts
Low pressure
Pressure probes
Pressure sensors
Reference signals
Rotation
Rotor blades
Rotor blades (turbomachinery)
Rotors
Spectrum analysis
Stress propagation
Stresses
Struts
Turbines
Turning
Unsteady flow
Vibration meters
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Summary:This paper analyzes the propagation of the aerodynamic deterministic stresses through a two-spool counter-rotating transonic turbine at Graz University of Technology. The test setup consists of a high-pressure stage, a diffusing midturbine frame with turning struts and a counter-rotating low-pressure rotor. The discussion of the data is carried out in this second part paper on the basis of spectral analysis. The theoretical framework for a double Fourier decomposition, in time and space, is introduced and discussed. The aim of the paper is the identification of the sources of deterministic stresses that propagate through the turbine. A fast-response aerodynamic pressure probe has been employed to provide time-resolved data downstream of the high-pressure rotor and of the turning strut. The fast-response aerodynamic pressure probe measurements were acquired together with a reference signal (a laser vibrometer) downstream of the high-pressure rotor to identify different sources of deterministic fluctuations. The discussion is completed by fast-response pressure measurements on the strut surface and computational fluid dynamics computation to detail which deterministic stress related to the high-pressure stage propagates through the duct. The double Fourier decomposition shows that structures at the periodicity of the rotor blade number decay, whereas the unsteadiness at the outlet of the duct is the result of vane–rotor–vane interaction.
ISSN:0748-4658
1533-3876
DOI:10.2514/1.B35487