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Search results for: HYDRODYNAMIC BEARING, STATIC CHARACTERISTICS, REYNOLDS EQUATION, CALCULATION PROCEDURES
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Experimental comparison of the transition speed of a hydrodynamic journal bearing lubricated with oil and magnetorheological fluid
PublicationA journal bearing test bench is used to find the transition speed between the hydrodynamic and mixed lubrication regimes for a modified magnetorheological (MR) fluid. It is shown that the transition speed of the bearing can be reduced by applying a local magnetic field near minimum film when it is lubricated with the MR fluid, and that this will only marginally increase friction. The lubricating performance of the MR fluid is compared...
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Improvement of Thrust Bearing Calculation Considering the Convectional Heating within the Space between the Pads
PublicationA modern thrust bearing tool is used to estimate the behavior of tilting pad thrust bearings not only in the oil film between pad and rotating collar, but also in the space between the pads. The oil flow in the space significantly influences the oil film inlet temperature and the heating of pad and collar. For that reason, it is necessary to define an oil mixing model for the space between the pads. In the bearing tool, the solutions...
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Improvement of the thrust bearing calculation considering the convectional heating within the space between the pads
PublicationA modern thrust bearing calculation tool should consider not only the oil film between pad and rotating collar but also the space between the pads. The oil flow in the space has a significant influence on the oil film inlet temperature, the convectional cooling of pad and collar and should be included in the bearing calculation methods. The authors use a tool developed at Clausthal University of Technology in cooperation with the...
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Application of the Optimization Methods to the Search of Marine Propulsion Shafting Global Equilibrium in Running Condition
PublicationFull film hydrodynamic lubrication of marine propulsion shafting journal bearings in running condition is discussed. Considerable computational difficulties in non-linear determining the quasi-static equilibrium of the shafting are highlighted. The approach using two optimization methods (the particle swarm method and the interior point method) in combination with the specially developed relaxation technique is proposed to overcome...
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Numerical analysis of pile installation effects in cohesive soils
PublicationIn this thesis the empirical equation for radial effective stress calculation after displacement pile installation and following consolidation phase has been proposed. The equation is based on the numerical studies performed with Updated Lagrangian, Arbitrary Lagrangian-Eulerian and Coupled Eulerian-Lagrangian formulations as well as the calibration procedure with database containing world-wide 30 pile static loading tests in cohesive...
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Considerations about the applicability of the Reynolds equation for analyzing high-speed near field levitation phenomena
Publicationequation for analyzing near field levitation (NFL) phenomena. Two separate approaches were developed, experimentally verified, and applied to meet the research objective. One was based on the Reynolds equation and the other was based on general conservation equations for fluid flow solved using computational fluid dynamic (CFD). Comparing the calculation results revealed that, for certain operating conditions, differences in the...
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Large hydrodynamic thrust bearing: Comparison of the calculations and measurements
PublicationHydrodynamic thrust bearings, used to carry axial loads in heavily loaded shafts of water power plants hydro turbines, can reach outer diameters even exceeding 5 m. In such large objects scale effect could be observed. According to this, allowable bearing specific load assuring safe operation of the bearings has to be decreased, which increases thrust bearing dimensions. This effect is caused by excessive thermal deflections of...
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ANALYSIS OF BEARING CLEARANCE AND WIDTH OF OIL GROOVE ON CHARACTERISTIC OF FLUID FILM IN HYDRODYNAMIC MAIN CRANKSHAFT BEARINGS
PublicationAbstract Paper represents analysis of influence of oil groove width and bearing clearance on characteristics of oil film in hydrodynamic journal main crankshaft bearing. Analysis was performed in purpose to define influence of bearing clearance and dimensions of oil groove on static characteristics and manufacturability of half shelf bearings in industrial high-volume production. Computer simulations was made using ARTbear program...
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Displacement piles - classification and methods for the calculation of bearing capacity.
PublicationDisplacement piles belong to a group of technologies whose main idea is to install or make a pile without extracting ground material. According to definition, contained in PN-EN:1997-1:2008, displacement piles should be considered as driven, pressed in using vibrators and made with the use of spread augers. The classification of piles used so far with regard to the technology of execution is modified. An additional element is the...
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ANALYSIS OF THE LOAD-CARRYING CAPACITY OF A HYDRODYNAMIC WATER-LUBRICATED BEARING IN A HYDROELECTRIC POwER PLANT
PublicationThe paper presents an analysis of the load-carrying capacity of a historic hydrodynamic water-lubricated radial bearing of an unconventional segment design installed in the Braniewo Hydroelectric Power Plant. The aim of the calculations was to determine whether the bearing operates in the conditions of hydrodynamic or mixed lubrication, as well as to establish the optimal geometry of the axial grooves allowing for the highest load-carrying...
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Experimental research on a hydrodynamic thrust bearing with hydrostatic lift pockets: Influence of lubrication modes on bearing performance
PublicationThe aim of the study is to investigate the performance of a thrust bearing equipped with hydrostatic lift pockets under different lubrication modes. Three types of flat land bearing lubrication modes are studied experimentally: hydrostatic lubrication (HS; forced oil injection to the pockets), hybrid lubrication (HS + HD; hydrostatic lubrication combined with the external forced bearing oil supply) and hydrodynamic lubrication...
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Compliance tests of the polymer layers used as hydrodynamic bearing coatings
PublicationOperational experience and scientific investigations results showed that polymer lined hydrodynamic bearings can withstand more severe operating conditions compared than white metal bearings. PTFE and PEEK-based coatings are the most frequently used as Babbitt alternatives. Both polymers differ significantly from the each other in material properties. According to catalogue data compression modulus of PTFE, it is about an order...
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A comparative performance assessment of a hydrodynamic journal bearing lubricated with oil and magnetorheological fluid
PublicationThis work presents the investigation results of a journal bearing lubricated with magnetorheological fluid that is activated by a local constant magnetic field to vary both the local flow resistance and pressure. The bearing performance is assessed via Finite Element Modelling (FEM) and results are corroborated by experiments. The FEM model uses the Bingham model to describe the fluid film. A dedicated test rig is used to assess...
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Emotion Monitoring – Verification of Physiological Characteristics Measurement Procedures
PublicationThis paper concerns measurement procedures on an emotion monitoring stand designed for tracking human emotions in the Human-Computer Interaction with physiological characteristics. The paper addresses the key problem of physiological measurements being disturbed by a motion typical for human-computer interaction such as keyboard typing or mouse movements. An original experiment...
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Field Tests on Hydrodynamic and Hybrid Operation of a Bidirectional Thrust Bearing of a Pump-Turbine
PublicationIn vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Due to the bidirectional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from the point of view of their performance. Large thrust bearings have to be carefully designed so as to minimise excessive thermo-elastic pad deformations. The...
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Bearing capacity of piles based on static load tests and calculation principles provided by EN 1997-1
PublicationW artykule scharakteryzowano i przeanalizowano ogólne zalecenia Eurokodu 7 dotyczące wyznaczania nośności pali na podstawie próbnych obciążeń statycznych. Porównano je z zaleceniami dotychczasowej polskiej normy PN-83/B-02482. Przedstawiono kilka przykładów interpretacji rzeczywistych wyników próbnych obciążeń pali według zaleceń wyżej wymienionych dwóch norm wraz z analizą porównawczą.
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Running characteristics of aerodynamic bearing with self-lifting capability at low rotational speed
PublicationAn aerodynamic journal bearing that is capable of self-generating squeeze-film pressure is presented and its dynamic characteristics investigated numerically and experimentally. A numerical method based on a time marching static model was applied to assess the orbit trajectory path of the rotor upon a perturbation. Experimental results were obtained to validate the effect of the self- generated squeeze-film pressure on the stability...
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Field tests on hydrodynamic and hybrid operation of a bi-directional thrust bearing of a pump-turbine
PublicationIn vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Because of bi-directional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from the point of view of their performance. Large thrust bearings have to be carefully designed so as to minimise excessive thermo-elastic pad deformations. The...
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Disinfection characteristics of an advanced rotational hydrodynamic cavitation reactor in pilot scale
PublicationHydrodynamic cavitation is a promising technique for water disinfection. In the present paper, the disinfection characteristics of an advanced hydrodynamic cavitation reactor (ARHCR) in pilot scale were studied. The effects of various flow rates (1.4–2.6 m3/h) and rotational speeds (2600–4200 rpm) on the removal of Escherichia coli (E. coli) were revealed and analyzed. The variation regularities of the log reduction and reaction...
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Microscopic calculation of the static electric susceptibility of polyethylene
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Hydrodynamic pressure in micro-and nano bearing gap
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Straightened characteristics of McKendrick-von Foerster equation
PublicationWe study the McKendrick-von Foerster equation with renewal (that is the age-structured model, with total population dependent coefficient and nonlinearity). By using a change of variables, the model is then transformed to a standard age-structured model in which the total population dependent coefficient of the transport term reduces to a constant 1. We use this transformation to get existence, uniqueness of solutions of the problem...
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Influence of Collar Deformations on Hydrodynamic Thrust Bearing Performance
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Hydrodynamic journal bearing - ''Y'' particularly for steam turbines.
PublicationW artykule przedstawiono koncepcję i zasadę działania nowego, ślizgoweo łożyska poprzecznego typu ''Y''. Przedstawiono wady i zalety nowego rozwiązania. Porównano charakterystyki dynamiczne i statyczne klasycznego łożyska cytrynowego (soczewkowego) z nowym łożyskiem ''Y''.Podano przykładowe wdrożenia i ich efekty.
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Model of the reciprocating engine using iterative procedures of the transient torque calculation
PublicationPrzedstawiony w pracy model silnika spalinowego uzależnia wartość dynamicznego momentu od sygnału sterowania po skokowej zmianie nastawy oraz od historii dynamicznej silnika i czasu jaki upłynął od tej zmiany. Przedstawione wyniki badań potwierdzają zasadność takiego opisu modelowanego zjawiska. Można również zauważyć, że po pewnym czasie od chwili rozpoczęcia procesu rozpędzania przebieg momentu dynamicznego będzie przebiegał...
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Estimation of pile bearing capacity by dynamic and static tests
PublicationBadania dynamiczne, szczególnie dla pali wbijanych, w budownictwie hydrotechnicznym stają się coraz bardziej popularne. Badania, poparte formalnie zapisami zawartymi w Eurokodzie 7, wykorzystywane w badaniach ''na wodzie'' i ''na lądzie'' są szybkie i ekonomiczne. Przedstawiono serię badań dla gruntów uwarstwionych dla pali prefabrykowanych żelbetowych, wbijanych stalowych pali rurowych oraz pali Vibro-Fundex. Badania dynamiczne...
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Experimental measurements of the hydrodynamic characteristics of the pod propulsor models
PublicationPraca przedstawia wyniki pomiarów charakterystyk hydrodymicznych trzech wariantów modelu pędnika azymutalnego. Charakterystyki obejmują napór pędnika, siłę boczną i moment względem osi pionowej w zależności od współczynnika posuwu i kąta dryfu.
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A stochastic approach to the problem of bearing capacity by the method of characteristics
PublicationW pracy omówiono zagadnienie nośności granicznej podłoża o własnościach losowych, przy obciążeniu od spoczywającego na nim fundamentu. Zaproponowano stochastyczną modyfikację metody charakterystyk bazującej na metodzie różnic skończonych. Analizowano zagadnienia związane z dyskretyzacją losowego ośrodka gruntowego, symulacją pola losowego oraz ze zbieżnością i stabilnością rozwiązania. Przedstawione podejście umożliwiło uwzględnienie...
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Numerical Simulations of Hydrodynamic Open-Water Characteristics of a Ship Propeller
PublicationThe paper presents the results of numerical simulations of ship propeller operation bearing the name of Propeller Open Water (POW) Tests. The object of tests was a sample ship propeller (PPTC1), the geometrical and kinematic data of which are available, along with the results of model tests, on the official page of the research centre involved in the measurements. The research aimed at verifying the correctness of results of numerical...
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Effect of manufacturing errors of the pad sliding surface on the performance of the hydrodynamic thrust bearing
PublicationIn the present study, investigation of the effect of manufacturing errors on the performance of large tilting pad thrust bearings has been performed, following a CFD-based Thermohydrodynamic analysis of a single pad. A 3D model has been generated, including the pad, the lubricant film and the corresponding part of the collar. The pad has been assumed to be deformed about the pivot point, due to thrust loading. Manufacturing errors...
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Mesh dependence study for numerical assessment of hydrodynamic characteristics of windsurfing fin
PublicationThe presented research aims to assess the drag coefficient and lift coefficient versus angle of attack curves for windsurfing fin. Special attention in the research was being paid to the evaluation of the stall angle value. The angle of incidence for which the stall occurs was searched, and the sensitivity of the solution for the mesh resolution was studied. The mesh resolution sensitivity analysis was done by systematically decreasing...
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Evaluation of water turbine hydrodynamic thrust bearing performance on the basis of thermoelastohydrodynamic calculations and operational data
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Evaluation of water turbine hydrodynamic thrust bearing performance on the basis of thermoelastohydrodynamic calculations and operational data.
PublicationW pracy przedstawiono analizę konstrukcji łożyska wzdłużnego turbiny wodnej. Łożysko zostało skonstruowane około 50 lat temu, a jego konstrukcja przewiduje kompensację termicznych odkształceń klocków. W analizie uwzględniono odkształcenia łożyska i wymianę ciepła w filmie smarowym i klockach łożyskowych. Poza obecną konstrukcją łożyska przeprowadzono również studium wpływu podstawowych parametrów konstrukcyjnych: grubości klocka...
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Comparison of the characteristics of journal bearings determined according to ISO 7902:2020 and obtained by other methods
PublicationThe article presents selected characteristics of journal bearings calculated with the use of various methods and compared to the results obtained with application of the basic bearing characteristics calculation procedure, as described in the ISO 7902:2020 standard. Additionally, the presented calculation results were compared with the parameters measured during experimental tests of the sliding bearings, working under loads and...
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Effects of loading pattern and lubricant pressure influence on bearing alloy fatigue characteristics
PublicationOpisano wyniki testów zmęczeniowych przeprowadzonych dla stopu łożyskowego AlSn (11,3 Cu 1,2) osadzonego na taśmie stalowej. Doświadczalnie określono wartości obciążeń niszczących dla różnych warunków obciążenia: dla obciążeń zginających wahadłowych, dla obciążeń zginających wahadłowych przy równoczesnym działaniu słabego lub zmiennego ciśnienia w komorze olejowej.
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Extended duration running and impulse loading characteristics of an acoustic bearing with enhanced geometry
PublicationThis paper presents performance during prolonged running of the acoustic bearing when PZTs are switched off and when they are switched on. The effect of active PZT on shaft’s displacements in X and Y directions is clearly demonstrated. Performance of the acoustic bearing was also assessed when an impulse force was applied to the running shaft at speed. Once again the benefits of having PZTs active are beyond doubt. The instability...
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Thermal and Hydrodynamic Phenomena in the Stagnation Zone — Impact of the Inlet Turbulence Characteristics on the Numerical Analyses
PublicationOne of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unanswered. In general, the wall-jet interaction and the near-wall turbulence are supposed to be its main reason, but their accurate numerical...
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Badania teoretyczne łożysk ślizgowych podpartych na czaszy kulistej = Theoretical tests of hydrodynamic journal bearing with self-aligning spherical support
PublicationPrzedstawiono metodykę badań teoretycznych i doświadczalnych łożysk ślizgowych podpartych na czaszy kulistej. Badania teoretyczne prowadzono z wykorzystaniem programu komputerowego MES oraz programu wyznaczającego charakterystyki filmu olejowego. W celu opisu systemu tribologicznego łożysko-podpora stworzono trójwymiarowy model MES łożyska i gniazda. W czasie badań analizowano wpływ wielu czynników mogących ułatwiać lub utrudniać...
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Wpływ odkształceń tarczy oporowej wału na właściwości hydrodynamicznego łożyska wzdłużnego = Influence collar deformations of hydrodynamic thrust bearing performance
PublicationPodjęto próbę określenia możliwego wpływu deformacji termosprężystej tarczy oporowej łożyska na jego cechy. Porównano wyniki trzech wariantów obliczeń TEHD: bez uwzględniania deformacji tarczy, z uwzględnieniem deformacji tylko sprężystych oraz z uwzględnieniem deformacji termosprężystych tarczy oporowej.
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Ocena wybranych własności materiałowych polimerowej warstwy ślizgowej hydrodynamicznego łożyska wzdłużnego = An estimation of selected material properties of the hydrodynamic thrust bearing polymer lining
PublicationZaprezentowano metody pomiaru najważniejszych własności mechanicznych i cieplnych polimerowego pokrycia segmentowego łożyska wzdłużnego, do których zaliczyć należy moduł sprężystości wzdłużnej oraz współczynnik przewodności cieplnej materiału dodatkowym utrudnieniem planowanego zadania jest fakt, że próbka do badań dostępna będzie jedynie w formie wycinka z segmentu łożyskowego, z tego powodu nie jest możliwe zastosowanie ogólnie...
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Numerical modelling and experimental verification of compressible squeeze film pressure
PublicationThe validity of using the Reynolds equation for compressible squeeze film pressure was tested with computational fluid dynamics (CFD). A squeeze film air bearing was instrumented with pressure sensors and non-contacting displacement probes to provide transient measurements of film thickness and pressure. The film thickness measurements also provided input parameters to the numerical prediction. However, numerical results showed...
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Fundamenty palowe, obliczenia z zastosowaniem zasad Eurokodu 7 i doświadczeń krajowych
PublicationPrzedstawiono zagadnienia obliczania fundamentów palowych w nawiązaniu do zaleceń Eurokodu 7. Zwrócono uwagę, że zgodnie z założeniami Eurokodu 7, projektant i inżynier ma swobodę w wyborze metod obliczeniowych.Przytoczono i zarekomendowano metody i propozycje miedzy innymi obliczania statycznego układów palowych, określania nośności pali, prognozowania osiadań fundamentów palowych oraz charakterystyk obciążenie-osiadanie pali...
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Structural properties of foil bearings: a closed-form solution validated with finite element analysis
PublicationFluid film thickness in a compliant foil bearing is greatly influenced by the deflection of the bearing structure. Therefore, in order to properly model performance of a foil bearing, it is mandatory that the deflection of the compliant bearing structure due to the generated hydrodynamic pressure is determined accurately. This article proposes an easy-to-use two-dimensional model, which takes into account detailed geometry of the...
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New Generation of Water lubricated Foil bearing - Numerical Models and Experimental Verification
PublicationIn the paper a new idea of foil water lubricated bearing and methodology of hydrodynamic characteristics calculations is presented. To assesses the theoretical characteristics of these bearings two different computer models were built. First is structural model coupled with fluid model. It takes into account: fluid flow in the deformed fluid gap, specific design of bearing support and friction in bearing support. The second is...
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Environmentally acceptable lubricants (EAL) compared with a reference mineral oil as marine stern tube bearing lubricant – Experimental and theoretical investigations
PublicationThe purpose of this research is to indicate the potential differences in bearing characteristics resulting from the application of different lubricant types with the same viscosity grade. The effect of different environmentally acceptable lubricants (EALs) on hydrodynamic journal bearing properties is studied experimentally and compared to the properties obtained after lubrication with a reference mineral oil. The results of the...
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Influence of bush wear in water lubricated marine stern tube bearings with shaft misalignment
PublicationWater lubricated propeller shaft bearings are frequently employed on modern ships due to their advantages such as durability, simplicity and low price. Specific working conditions on ships cause shaft misalignment which often results in rapid wearing of bush and shaft. Shaft misalignment could be an effect of manufacturing or assembly faults but sometimes it appears due to hull or shaft deformation. The wearing process has influence...
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Simulation of large thrust-bearing performance at transient states, warm and cold start-up
PublicationThe start-up of a large hydrodynamic thrust bearing of a vertical hydrogenerator is one of the most critical situations during the lifetime of a bearing. Hydrodynamic load capacity is low due to low speed and higher thermal deformations of the pad. A new approach to the simulation of a hydrodynamic bearing is shown in this article. A combination of finite elements method and computational fluid dynamics is used to perform the transient...
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Study of the Influence of Heat Convection Coefficient on Predicted Performance of a Large Tilting-Pad Thrust Bearing
PublicationPart of the heat generated by the shearing of the lubricating film during operation of a hydrodynamic bearing is transferred to the bearing components. In the case of the pad, which is usually fully submerged in the lubricating oil, heat is further transferred at the pad free walls to the oil by convection. This mechanism causes a thermal gradient in a pad and, consequently, its thermal deflection. In large hydrodynamic thrust...
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RESEARCH ON HYDRODYNAMIC PEEK JOURNAL BEARINGS LUBRICATED WITH WATER AND OIL
PublicationThe main purpose of the research was to determine the possibilities and experimentally test the benefits of replacing conventional oil lubrication with ecological water lubrication. Tests were carried out on a test rig for hydrodynamic radial bearings under conditions representative of the expected applications for the bearing in water turbines. Bearings made from the polymer material PEEK (polyether ether ketone) were tested under static...
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Design of horizontal axis wind and water turbines
PublicationThe basic hydrodynamic principles of horizontal axis turbines are presented. Computational methods based on vortex theory for design of such turbines and for calculation of their hydro or aerodynamic characteristics are described in detail. These methods are applicable both to wind and water turbines. The influence of detailed turbine geometry on its characteristics is presented. Several practical computational examples of different...