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    Wyświetlanie 1-4 z 4
    Tytuł:
    Numerical simulation of feedback controlled fluid-induced instabilities in rotor system supported by hydrodynamic bearings
    Autorzy:
    Ferfecki, P.
    Sikora, R.
    Poruba, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/229847.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    rotor system
    hydrodynamic bearing instability
    kinematic excitation
    Opis:
    In certain operating conditions, the oil-film forces, by which the hydrodynamic bearings act on the rotor, destabilize and induce a self-excited vibration. There are many solution based on modifications of the bearing geometry to enlarge the operational range of the hydrodynamic bearing as a tilting pad bearing, lemon bore, etc. or usage of the dampers whose operation is based only on the dissipation of mechanical energy. In this paper several concepts based on controlled kinematic excitation of the bearing shells is investigated by computer simulation and by experimental test. The mathematical model of the uncontrolled and controlled rotor system contains the nonlinear hydrodynamic forces determined by the solution of the Reynolds equation assuming short case of bearing. To solve the equation of motion the Runge-Kutta method of the 4th order with Dormand-Prince modification and variable length of the integration step is used. The computer simulations were performed for rotor system without feedback control and with feedback controller. The main objectives of the numerical analysis were determination of the stability regions of the vibration excited by the imbalance forces. Results of the computer simulations proved that the analyzed approaches reduce amplitude of the rotor vibration caused by the imbalance forces. Experimental test and computer simulations demonstrate that the active vibration control increases considerably the rotation speed when the self-excited vibration of the oil-film occurred.
    Źródło:
    Archives of Control Sciences; 2010, 20, 3; 287-301
    1230-2384
    Pojawia się w:
    Archives of Control Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hydrodynamic tilting pad journal bearing with automatic control
    Łożysko hydrodynamiczne z panewką z ruchomymi płytkami ze sterowaniem automatycznym
    Autorzy:
    Marcinkevičius, A. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/140110.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    łożysko hydrodynamiczne
    sterowanie automatyczne
    zużycie
    temperatura
    obciążenie
    hydrodynamic bearing
    automatic control
    wear
    temperature
    load
    Opis:
    Hydrodynamic three tilting-pad journal bearing is analyzed in the paper. It is shown that, when assembling that type of not controlled bearing, it is impossible to obtain a small clearance between the pad and the journal at high frequency of journal rotation. In a static state, i.e. when the journal is immobile, such a bearing should be assembled with a large interference between the pads and the journal in order to guarantee the small clearance at rotation. At start, when the hydrodynamic lubricating wedges between the pads and journal are absent, the bearing would work with dry friction, resulting in quick wear of pads and high load of the drive motor. Apart of that, it is impossible to control the power consumption and temperature regime neither for idle nor for working rotation of the journal. The proposed automatic control gives a possibility to regulate the clearance between the pads and the journal by measuring and controlling the axial force of the pad load, and in such a way to improve work conditions of the bearing.
    Praca dotyczy analizy warunków pracy łożyska hydrodynamicznego z panewką z ruchomymi płytkami ze sterowaniem automatycznym. Pokazano, że bez sterowania nie jest możliwe zapewnienie małej szczeliny pomiędzy płytką a czopem przy obrotach wału z dużymi prędkościami. W warunkach statyki, gdy wał pozostaje w spoczynku, łożysko takie powinno być montowane z dużym luzem ujemnym pomiędzy płytkami i czopem aby zagwarantować małą szczelinę przy obrotach wału. W początkowym okresie pracy łożyska, przy braku klina smarnego, łożysko mogłoby pracować w warunkach tarcia suchego co prowadzi do szybkiego zużycia płytek i dużego obciążenia napędu. Ponadto nie jest możliwe sterowanie zużyciem energii ani warunkami temperatury w której pracuje łożysko zarówno bez jak i pod obciążeniem. Zaproponowane sterowanie daje możliwość regulacji szczeliny pomiędzy płytkami i czopem poprzez pomiar i sterowanie siłą osiową obciążającą płytkę, co prowadzi do polepszenia warunków pracy łożyska.
    Źródło:
    Archive of Mechanical Engineering; 2010, LVII, 4; 343-354
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An experimental investigation conducted in order to determine bearing dynamic coefficients of two hydrodynamic bearings using impulse responses
    Autorzy:
    Breńkacz, Ł.
    Żywica, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/175435.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    hydrodynamic bearings
    bearing dynamic coefficients
    experimental study
    Opis:
    The paper presents the experimental investigation carried out in order to identify bearing dynamic coefficients of two hydrodynamic bearings from impulse responses. In this method the stiffness, damping and mass coefficients of two hydrodynamic bearings were calculated in a single algorithm. For each rotational speed, were obtained 12 dynamic coefficients which enable to fully describe the dynamic state of the rotor. Exciting force signals, applied using an impact hammer were shown. Displacements of the shaft were measured by eddy current sensors. The measurements were carried out at various rotational speeds, including resonance speeds. The vibration amplitude in a resonance case increases significantly with time after the excitation was induced by an impact hammer. Excitations of the rotor with an impact hammer were recorded using a high-speed camera. These unique recordings and simultaneous analysis of the trajectory of the bearing journals depict the contact phenomena that occur during impulse excitation of the rotor.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2016, 133; 39-54
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of lubricant compressibility and variable viscosity on the performance of three-lobe journal bearing
    Autorzy:
    Mahdi, Mushrek A.
    Abass, Basim Ajeel
    Powiązania:
    https://bibliotekanauki.pl/articles/2172770.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    hydrodynamic lubrication
    journal bearing
    compressibility effect
    variable viscosity
    smarowanie hydrodynamiczne
    łożysko
    zmienna lepkość
    Opis:
    Different configurations of journal bearings have been extensively used in turbo- machinery and power generating equipment. Three-lobe bearing is used due to its lower film temperature and stable operation. In this study, static performance of such a bearing has been investigated at different eccentricity ratios considering lubricant compressibility and variable viscosity. The effect of variable viscosity was considered by taking the viscosity as a function of the oil film thickness while Dowson model is used to consider the effect of lubricant compressibility. The effect of such parameters was considered to compute the oil film pressure, load-carrying capacity, attitude an- gle and oil side leakage for a bearing working at (ε from 0.6 to 0.8) and (viscosity coefficient from 0 to 1). The mathematical model as well as the computer program prepared to solve the governing equations were validated by comparing the pressure distribution obtained in the present work with that obtained by EL-Said et al. A good agreement between the results has been observed with maximum deviation of 3%. The obtained results indicate a decrease in oil film pressure and load-carrying capacity with the higher values of viscosity coefficient while the oil compressibility has a little effect on such parameters.
    Źródło:
    Archive of Mechanical Engineering; 2022, LXIX, 2; 203--219
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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