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Multistage coupling - free vibration of mistuned bladed discs

Rządkowski R., Maurin A.

Prace Naukowe Politechniki Warszawskiej. Transport

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2013

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z. 98

565--573

EN

Considered here was the effect of multistage coupling on the dynamics of an aircraft rotor consisting of eight mistuned bladed discs on a drum-disc shaft. Each bladed disc had a different number of rotor blades. Free vibrations were examined using finite element representations of rotating single blades, bladed discs, and the entire rotor. In this study the global rotating mode shapes of eight flexible mistuned bladed discs on shaft assemblies were calculated, taking into account rotational effects such as centrifugal stiffening. The thus obtained natural frequencies of the blade, shaft, bladed disc and entire shaft with discs were carefully examined to discover resonance conditions and coupling effects. This study found that mistuned system has far more intensive multistage coupling than tuned one.

PL

Artykuł stanowi wprowadzenie do analizy dynamiki wirnika silnika odrzutowego zawierającego osiem rozstrojonych, ułopatkowanych tarcz. Każda ułopatkowana tarcza posiadała różną, rzeczywistą liczbę łopatek. W celu wyjaśnienia wpływu wprowadzonego na poszczególnych stopniach turbiny rozstrojenia na powstawanie rezonansów w badanym układzie, obliczono drgania własne wirujących pojedynczych łopatek, ułopatkowanych tarcz oraz całego wirnika wykorzystując metodę elementów skończonych. Zbadane zostały postacie drgań własnych poszczególnych elementów jak i całego modelu biorąc pod uwagę wpływ prędkości obrotowej taki jak usztywnienie pod działaniem siły odśrodkowej. Otrzymane wartości częstotliwości drgań własnych poszczególnych łopatek, ułopatkowanych tarcz, wału oraz całego układu zostały uważnie przebadane pod kątem wykrycia warunków rezonansowych oraz dodatkowych sprzężeń. Stwierdzono, iż rozstrojenie w układzie powoduje zdecydowanie intensywniejsze występowanie sprzężeń w porównaniu z układami nastrojonymi.

2

Multistage coupling of eight mistuned bladed discs on a solid shaft with 1% mistuning

Maurin A., Rządkowski R., Drewczyński M.

Mechanics and Mechanical Engineering

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2011

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Vol. 15, nr 3

309-317

EN

Considered here was the effect of multistage coupling on the dynamics of a rotor consisting of eight mistuned bladed discs on a solid shaft. Free and forced vibrations were examined. In this study, the global rotating mode shapes of flexible mistuned bladed discs-shaft assemblies were calculated, taking into account rotational effects, such as centrifugal stiffening. The thus obtained natural frequencies of the blade, the shaft, the bladed disc, and the entire shaft with discs were carefully examined to discover resonance conditions and coupling effects.

3

Natural frequencies of tuned and mistuned bladed discs on a shaft

Rządkowski R., Drewczyński M., Kubitz L.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2006

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Vol. 10, No 3

275-289

EN

The dynamic behaviour of a rotor consisting of two tuned and mistuned bladed discs on a solid shaft is considered. The effect of the shaft's flexibility on the dynamic characteristics of the bladed discs and the coupling effects between the shaft and bladed disc modes are investigated. Results show clearly the coupling effects in a bladed disc-shaft system. Interference diagrams are developed, from which the dynamic behaviour of a bladed disc can be predicted for varying flexibility relationships between solid shafts and bladed discs. The global rotating mode shapes of flexible tuned and mistuned bladed disc-shaft assemblies are calculated. Rotational effects, such as centrifugal stiffening, are accounted for and all the possible couplings between the flexible parts are allowed. Calculated natural frequencies obtained from the blade, the bladed disc and the shaft with two discs are checked to discover resonance conditions and coupling effects. It is shown that blade mistuning strongly affects the interaction between flexible bladed discs and a flexible shaft. This interaction affects the flexible bladed disc modes and is not restricted to the modes with zero, one and two nodal diameters. The torsional frequency of the shaft with two bladed discs is coupled with the zero nodal diameter modes of the single bladed discs. It is shown that including the shaft in the bladed discs model is important from the designer's point of view and may alter the spectrum of frequencies considerably.

4

Natural Frequencies of Several Bladed Discs on the Shaft

Rządkowski R., Drewczyński M.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2005

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nr 128, vol. 2

457-470

EN

The effect of multistage coupling on the dynamics of a rotor consisting of eight bladed discs on a solid shaft is considered. Free vibrations are examined using finite element representations of rotating single blades, bladed discs, and the complete rotor. In this study, the global rotating mode shapes of flexible tuned bladed discs-shaft assemblies are calculated. Rotational effects, such as centrifugal stiffening are accounted for, and all the possible couplings between the flexible parts are allowed. The gyroscopic effects are included. The calculated natural frequencies obtained from the blade, the shaft, the bladed disc, and the complete shaft with discs are carefully examined to discover resonance conditions and the coupling effects. It was found that the flexible modes of the tuned bladed discs affected by shaft motion are those with zero, one and two nodal diameters. In these modes the shaft deflection is clearly visible. The findings of this paper suggest that multistage analysis may be required for proper calculations of free vibration of bladed discs.