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Diagnostics of turbine blades, based on estimation of frequency response function

Kotkowski Jerzy, Rokicki Edward, Lindstedt Paweł, Spychała Jarosław, Perczyński Jerzy, Karbowiak Hieronim

Journal of KONBiN

2021

Vol. 51, iss. 2

63--78

The aim of the study is to propose a diagnostics method based on blade’s vibration model in frequency domain. Amplitude spectrum A(ω) and phase spectrum φ(ω) have been experimentally identified which define transfer function G(jω) = P(ω) + jQ(ω) and their real P(ω) and imaginary Q(ω) parts. Transfer function G(jω) and resulting frequency, amplitude, phase characteristics and real P(ω) and imaginary Q(ω) parts are parts of blade’s diagnostics model. Changes in those characteristics are directly related to changes in the technical condition of the blades. It has been noticed that small changes in the technical condition cause large changes in frequency characteristics, which proves their usefulness in the diagnosis process.

Celem badania jest zaproponowanie metody diagnostycznej opartej na modelu drgań łopatek w dziedzinie częstotliwości. Zidentyfikowano eksperymentalnie widma ampli-tudowe A(ω) i fazowe φ(ω), które definiują transmitancję operatorową G(jω) = P(ω) + jQ(ω) oraz jej rzeczywiste P(ω) oraz urojone Q(ω) części. Transmitancja operatorowa G(jω) i wynikająca z niej częstotliwość, amplituda, charakterystyka fazowa oraz rzeczywiste P(ω) i urojone Q(ω) części są częściami modelu diagnostycznego łopatki. Zmiany w tych charakterystykach są bezpośrednio związane ze zmianami w stanie technicznym łopatek. Zauważono, że małe zmiany w stanie technicznym powodują duże zmiany w charakterystykach częstotliwościowych, co świadczy o ich przydatności w procesie diagnostycznym.

Resonance tests - vibration mode shapes from the wing torsion group

Wiśniewski W.

Journal of KONES

2009

Vol. 16, No. 4

557-561

Resonances of the „ wings torsion " mode shapes to a large extent depend on the structural parameters of the wing, and more specifically to the existence or not of fuel tanks at the wings ends, munitions hard points or engines mounted on the wings. In the paper the group of resonances is presented with mode shapes in which the one, two or three node aircraft wing torsion is present. It is shown in the paper, that these vibration mode shapes consist both of fuselage bending or torsion. Resonance frequencies with mode shapes in which one, two or three node wing torsion occurs depend fundamentally on existence of wing hardpoints. If hardpoints are occupied by fuel tanks, these frequencies are varying continuously in wide range. The various interesting from cognitive point of view combinations have place then, including variable frequencies and variable mode shapes as a function of fuel consumption. The aim for the analysis of 3 cases of resonance a wing torsion mode shapes of airplanes and gliders was to investigate the relationships and mechanisms that are taking place and operate between the torsioningl vibration of the wings and bending or torsion vibrations of the fuselage. Recognition of these phenomena should facilitate the researcher to understand and search effectively and explore the resonances of„ wing torsion " mode shapes.