Przeglądaj {{ collection }} wg Autor "Łagodziński, Jakub"

Teraz wyświetlane 1 - 5 z 5

Determination of global damping and stiffness coefficients of journal foil bearing
(Wydawnictwo Politechniki Łódzkiej, 2021) Łagodziński, Jakub; Tkacz, Eliza; Kozanecki, Zbigniew
For the few last years, in modern low-power generation systems, a demand for oilfree compressors has appeared. The development of reliable bearing technology for this relatively high-speed small turbomachinery could be crucial. In order to implement this technology more widely, a selection of the optimal design from the viewpoint of machine reliability must be conducted. A high speed turbomachinery with nominal speed of tens of thousands rpm strongly depends on the proper rotordynamic design. This is especially important when the foil bearings are taken to consideration. These compliant surface gas bearings are a class of hydrodynamic bearings that use the ambient gas as their working fluid and, thus, require no dedicated lubrication system. On the other hand, due to their relatively low damping, a designer should analyze thoroughly the dynamics of the rotor-bearing-casing system in the whole operating rpm range. A correctly operating rotor supported in foil bearings is a design solution that have wide possibilities of applications, unavailable for conventionally supported one. In the turbomachinery, a dynamic behaviour of the machine is related mostly to the stiffness and damping coefficients of system components like rotor, bearings and casing. The foil bearings, although simple in design, indicate complex behaviour resulting from Coulomb friction between their elements. This Coulomb friction affects the damping and stiffness of a given bearing support. Gas film, as a bearing part with relatively high stiffness, plays less role in the rotordynamics than the elastic structure of corrugated foils. So far, many more or less reliable numerical models of this phenomenon have been built and their experimental verification results have been described in literature. The research approach presented in this paper is different. The authors suggested obtaining the data experimentally from the bearing isolated on a test bench, where, the shaft is stationary (fixed), and the gas film is not present. The shaker excites the bearing sleeve while the damping and stiffness are provided to the system by the foil structure. The test bench can be described mathematically as system with single degree of freedom with damping and external forcing. The information collected about the bearing’s global coefficients can be implemented afterwards to the rotordynamic software as a tabular data. This will allow to prepare reliable models that will shorten the design process of newly developed compressors with these oilfree supports.
Influence of intermediate foil on air-foil bearings performance and exploitation properties.
(Politechnika Łódzka. Wydział Mechaniczny. Katedra Automatyki, Biomechaniki i Mechatroniki., 2015) Łagodziński, Jakub; Miazga, Kacper
Air-foil technology is an interesting alternative for classic rolling or oil bearings in turbomachinery. It ensures low power losses, do not require external lubrication or pressurization and is capable of working with high rotational speeds. Numerous studies brought significant improvement in materials and design solutions for the aerodynamic shaft support system. The paper presents effects of modification performed by adding intermediate foil to typical structure of air-foil bearing. The main aim of the investigation was focused on analyze of its influence on characteristic parameters and exploitation properties of operating bearing, i.e. bearing load capacity and bearing resistance to thermal runaway phenomenon [4]. The thermal runaway is also known as foil bearing thermal instability. The tests confirmed proper behavior of the modified device and brought new knowledge in air-foil technology field.
Model of the gas journal bearing dynamics with a exibly supported foil.
(Politechnika Łódzka. Wydział Mechaniczny. Katedra Automatyki, Biomechaniki i Mechatroniki., 2015) Tkacz, Eliza; Kozanecki, Zbigniew; Kozanecka, Dorota; Łagodziński, Jakub
The work is devoted to an analysis of the journal bearing dynamics employing a numerical model which takes into account factors related to motion and friction of non{rotating elements of the sleeve. This model yields the basis for simulations carried out in order to determine correctly dynamic characteristics of an oil{free machine rotating system at the early stage of its design and during its operation. On the basis of those simulations, the thickness of gas lm was determined as well as the pressure distribution in the bearing and its lift capacity. Moreover, the numerical program led to an analysis of proper vibrations and forced vibrations of the system under consideration. It was possible to obtain attenuation of the force and to visualize a journal trajectory for the dynamic harmonic input function. The FFT (Fast Fourier Transform) analysis of vibrations was implemented. In the spectrum, only a frequency of the input function was observed, whereas and a lack of subsynchronous frequencies pointed to the stable operation of the bearing.
Niekonwencjonalne bezolejowe łożyska wysokoobrotowe turbogeneratora dla obiegu ORC.
(Wydawnictwo Politechniki Łódzkiej. Instytut Maszyn Przepływowych, 2013) Kozanecki, Zbigniew; Kozanecka, Dorota; Łagodziński, Jakub; Tkacz, Eliza
Obecnie w małych nowoczesnych systemach produkcji energii najczęściej stosowane są mikroturbiny o mocy rzędu od 1 do 20 kW. Niezwykle istotny jest rozwój niezawodnej technologii łożyskowania wirników tych miniaturowych maszyn przepływowych. Prezentowany w artykule układ wirujący turbogeneratora podparto w bezolejowych łożyskach foliowych. Podatne łożyska foliowe są rodzajem łożysk hydrodynamicznych, które wykorzystują gaz z otoczenia jako czynnik smarujący, co znacząco upraszcza ich konstrukcję.
Theoretical analysis of the foil bearings dynamic characteristics.
(Politechnika Łódzka. Wydział Mechaniczny. Katedra Automatyki, Biomechaniki i Mechatroniki., 2015) Tkacz, Eliza; Kozanecki, Zbigniew; Kozanecka, Dorota; Łagodziński, Jakub
In the theoretical analysis, three systems were identified: a rotor, a gas film and a exible structure. The mathematical analysis involves formulation of analytical equations for each of these elements and determination of their interactions. It was found that the rotor dynamics was subject to Newton's second law of motion, the gas flow in the bearing could be described by the Reynolds equation, whereas a spring-damper model was selected for the structural analysis. The Reynolds equation is a differential equation the exact solution to which is unknown. The work describes the finite difference method in detail, where the partial derivatives in the Reynolds equation are replaced by a system of algebraic equations. In order to solve the resulting system, the Alternating Direction Implicit method (ADI) was used. Thanks to those calculations, it was possible to determine the bearing dynamic characteristics using both the linear and non-linear method.