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Wyświetlanie 1-4 z 4
Tytuł:
Vibration control of rotors mounted in hydrodynamic bearings lubricated with magnetically sensitive oil by changing their load capacity
Autorzy:
Zapoměl, Jaroslav
Ferfecki, Petr
Powiązania:
https://bibliotekanauki.pl/articles/2086880.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
magnetically sensitive lubricant
controllable hydrodynamic bearings
controllable load capacity
rigid rotor
smar magnetycznie wrażliwy
kontrolowana pojemność
wirnik sztywny
Opis:
Rotors of rotating machines are often mounted in hydrodynamic bearings. Loading alternating between the idling and full load magnitudes leads to the rotor journal eccentricity variation in the bearing gap. To avoid taking undesirable operating regimes, its magnitude must be kept in a certain interval. This is offered by the hydrodynamic bearings lubricated with smart oils, the viscosity of which can be changed by the action of a magnetic field. A new design of a hydrodynamic bearing lubricated with magnetically sensitive composite fluid is presented in this paper. Generated in the electric coil, the magnetic flux passes through the bearing housing and the lubricant layer and then returns to the coil core. The action of the magnetic field on the lubricant affects the apparent fluid viscosity and thus the position of the rotor journal in the bearing gap. The developed mathematical model of the bearing is based on applying the Reynolds equation adapted for the case of lubricants exhibiting the yielding shear stress. The results of the performed simulations confirmed that the change of magnetic induction makes it possible to change the bearing load capacity and thus to keep the rotor journal eccentricity in the required range. The extent of control has its limitations. A high increase in the loading capacity can arrive at the rotor forced vibration’s loss of stability and induce large amplitude oscillation.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 6; e137988, 1--8
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Model-based initial residual unbalance identification for rotating machines in one and two planes using an iterative inverse approach
Autorzy:
Bastakoti, Satish
Choudhury, Tuhin
Viitala, Risto
Kurvinen, Emil
Sopanen, Jussi
Powiązania:
https://bibliotekanauki.pl/articles/2090689.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
flexible rotor
inverse approach
onsite-balancing
residual unbalance
single plane
double plane
wirnik elastyczny
metoda odwrotna
płaszczyzna pojedyńcza
płaszczyzna podwójna
Opis:
To achieve acceptable dynamical behavior for large rotating machines operating at subcritical speeds, the balancing quality check at the planned service speed in the installation location is often demanded for machines such as turbo-generators or high-speed machines. While most studies investigate the balancing quality at critical speeds, only a few studies have investigated this aspect using numerical methods at operational speed. This study proposes a novel, model-based method for inversely estimating initial residual unbalance in one and two planes after initial grade balancing for large flexible rotors operating at the service speeds. The method utilizes vibration measurements from two planes in any single direction, combined with a finite element model of the rotor to inversely determine the residual unbalance in one and two planes. This method can be practically used to determine the initial and residual unbalance after the balancing process, and further it can be used for condition-based monitoring of the unbalance state of the rotor.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 6; e139790, 1--12
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of parameters for a design of the stable electro-dynamic passive magnetic support of a high-speed flexible rotor
Autorzy:
Szolc, T.
Falkowski, F.
Henzel, M.
Kurnyta-Mazurek, P.
Powiązania:
https://bibliotekanauki.pl/articles/201250.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
rotor dynamics
electrodynamic passive magnetic bearings
active magnetic damper
stability analysis
rotor- shaft system
dynamika rotora
wirnik
amortyzator magnetyczny
analiza stabilności
pasywne łożysko magnetyczne
Opis:
Electro-dynamic passive magnetic bearings are now viewed as a feasible option when looking for support for high-speed rotors. Nevertheless, because of the skew-symmetrical visco-elastic properties of such bearings, they are prone to operational instability. In order to avoid this, the paper proposes the addition of external damping into the newly designed vibrating laboratory rotor-shaft system. This may be achieved by means of using simple passive dampers that would be found among the components of the electro-dynamic bearing housings along with magnetic dampers, which satisfy the operational principles of active magnetic bearings. Theoretical investigations are going to be conducted by means of a structural computer model of the rotor-shaft under construction, which will take into consideration its actual dimensions and material properties. The additional damping magnitudes required to stabilize the most sensitive lateral eigenmodes of the object under consideration have been determined by means of the Routh-Hurwitz stability criterion.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2019, 67, 1; 91-105
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polynomial chaos expansion method in estimating probability distribution of rotor-shaft dynamic responses
Autorzy:
Lasota, R.
Stocki, R.
Tauzowski, P.
Szolc, T.
Powiązania:
https://bibliotekanauki.pl/articles/200053.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
stochastic moment estimation
sparse polynomial chaos expansion
maximum entropy principle
rotor
uncertainties
hybrid mechanical model
random unbalance distribution
zasada maksymalnej entropii
wirnik
niepewności
model hybrydowy
losowy rozkład asymetrii
Opis:
The main purpose of the study is an assessment of computational efficiency of selected numerical methods for estimation of vibrational response statistics of a large multi-bearing turbo-generator rotor-shaft system. The effective estimation of the probability distribution of structural responses is essential for robust design optimization and reliability analysis of such systems. The analyzed scatter of responses is caused by random residual unbalances as well as random stiffness and damping parameters of the journal bearings. A proper representation of these uncertain parameters leads to multidimensional stochastic models. Three estimation techniques are compared: Monte Carlo sampling, Latin hypercube sampling and the sparse polynomial chaos expansion method. Based on the estimated values of the first four statistical moments the probability density function of the maximal vibration amplitude is evaluated by the maximal entropy principle method. The method is inherently suited for an accurate representation of the probability density functions with an exponential behavior, which appears to be characteristic for the investigated rotor-shaft responses. Performing multiple numerical tests for a range of sample sizes it was found that the sparse polynomial chaos method provides the best balance between the accuracy and computational effectiveness in estimating the unknown probability distribution of the maximal vibration amplitude.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2015, 63, 2; 413-422
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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