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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.

Artificial intelligence-based modeling for the estimation of Q-Factor and elastic young’s modulus of sandstones deteriorated by a wetting-drying cyclic process

Rashid Hafiz Muhammad Awais, Ghazzali Muhammad, Waqas Umer, Malik Adnan Anwar, Abubakar Muhammad Zubair

Archives of Mining Sciences

2021

Vol. 66, no. 4

635--658

In this study, a series of destructive and non-destructive tests were performed on sandstone samples subjected to wetting-drying cycles. A total of 25 Wet-Dry cycles were provided to investigate any significant change in the engineering properties of sandstones in terms of their porosity, permeability, water absorption, density, Q-factor, elastic modulus (E), and unconfined compressive strength (UCS). The overall reduction in the values of density, E, Q-factor, and UCS was noted as 3-4%, 42-71%, 34-62%, and 26-70% respectively. Whereas, the overall appreciation in the values of porosity, permeability, and water absorption was recorded as 24-50%, 31-64%, and 25-50% respectively. The bivariate analysis showed that the physical parameters had a strong relationship with one another and their Pearson’s correlation value (R) ranged from 0.87-0.99. In prediction modeling, Q-factor and E were regressed with the contemplated physical properties. The linear regression models did not provide satisfactory results due to their multicollinearity problem. Their VIF (variance inflation factor) value was found much greater than the threshold limit of 10. To overcome this problem, the cascade-forward neural network technique was used to develop significant prediction models. In the case of a neural network modeling, the goodness of fit between estimated and predicted values of the Q-factor (R2 = 0.86) and E (R2 = 0.91) was found much better than those calculated for the Q-factor (R2 = 0.30) and E (R2 = 0.36) in the regression analysis.

Electrically driven thermal annealing set-up dedicated to high quality factor optical resonator fabrication

Salzenstein P., Diallo S., Zarubin M.

Journal of Power Technologies

2018

Vol. 98, nr 2

198--201

This paper reports on the development of an oven with a special purpose electronic board and specialist materials such as basalt fiber and nichrome. It is designed for optical resonators which are temperature controlled during their annealing process to increase their quality factor for the purpose of photonics applications.