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The hydrodynamic journal bearing is still one of the most geometrically simple mechanical components, yet highly reliable and efficient and, above all, unique in what concerns to heavy duty – high load, high speed – support of rotating shafts. Analytical studies, not only to understand the physical basis of its performance, but also to develop practical tools for an expedite design, as well as to assure its reliability and improved efficiency, were object of the early developments in fluids’ hydrodynamic sciences, since the late XIX century, and are still been refined and improved on the XXI century. Historical marks can be flagged as (i) simplified analytical resolutions of the hydrodynamic pressure distribution; (ii) computerized iterative resolution of the full pressure development equations; (iii) introduction of the lubricant feeding conditions; (iv) analysis of the thermal aspects and its influence on viscosity; (v) localized aspects of fluid flow, due to thermal/viscous phenomena and geometrical particularities. This evolution led to increased accuracy on the performance predictions and to safer and higher efficiency of the designed components. On the other hand, analysis became more specific in use and, particularly with the introduction of the thermo-hydrodynamic analysis, led to the need of ‘tailored’ solutions to a given set of specific conditions. As a consequence, methods lost much of their ‘universality’ and ease of use to the common and sporadic designer. This work intents to make a first evaluation of the response of three prediction methods – a commercial and widely used isothermal approach and an isothermal and a thermohydrodynamic procedures, these former developed at UMinho over the last years – in an attempt to highlight the variability of the predictions of the main performance parameters by the use of simpler and rapid methods, when compared with those based on more complex and accurate analysis, and their eventual influence on an efficient and reliable design solution.

This paper describes the phenomenon of negative flow rate (hot oil reflux) occurring in one of the grooves of twin axial groove hydrodynamic journal bearings. This rarely described phenomenon, which can occur under severe operating conditions, increases the risk of bearing seizure. Existing codes for predicting bearing behaviour do not seem to be suitably incorporating this phenomenon into the analysis. The present work reports some experimental observations of the phenomenon and the way it can be taken into account in theoretical modelling., FCT - POCTI/39202/EME/2001 & PhD grant SFRH/BD/22278/2005

Laboratory tests have been carried out in order to investigate the influence of small changes in load direction on the performance of a steadily loaded hydrodynamic crown journal bearing. Hydrodynamic pressures, temperature distribution in the bush internal surface, shaft temperature, oil flow rate and bush torque were measured for fixed sets of operating conditions, at three different groove locations with respect to load line (0º, -30º, +30º). For each groove location quantitative information is provided concerning the influence of applied load and shaft rotational speed on the performance characteristics. Changing the location of the groove around load line did affect flow rate and bush torque, but had only a slight or moderate effect on bush maximum temperature., Fundação para a Ciência e a Tecnologia (FCT) Bolsa PRAXIS XXI Programme/BD/13922/97

Foi estudada experimentalmente a influência de alguns parâmetros de alimentação no desempenho de uma chumaceira radial hidrodinâmica com sulco de alimentação na linha de carga, carregada estaticamente. Os resultados obtidos mostram que a temperatura de alimentação condiciona fortemente todos os parâmetros de desempenho, enquanto que a pressão de alimentação afecta significativamente o caudal e ligeiramente a temperatura máxima do casquilho, tendo uma influência moderada sobre a excentricidade, sobretudo a baixa carga específica., Fundação para a Ciência e a Tecnologia (FCT) - bolsa PRAXIS XXI/BD/13922/97

Les performances des paliers hydrodynamiques peuvent être affectées de manière significative par les conditions d'alimentation du lubrifiant, par exemple, la position et les dimensions de la rainure ou la pression d'alimentation. Le but de ce travail est d'étudier les effects de ces paramètres d'alimentation sur les performances d'un palier lisse. A telle fin, un modèle numérique a été développé et des essais ont permis de recueillir des donnés expérimentales: la comparaison théorie-expérimentation est présentée., Hydrodynamic journal bearing performance can be significantly affected by lubricant supply conditions, namely, groove geometry and location and supply pressure. The aim of this work is to study the effect of these supply parameters on the bearing performance characteristics. For this purpose, a numerical model has been developed and experiments carried out: a comparison between theoretical predictions and experimental results is presented

Na presente comunicação é apresentada uma análise teórica do comportamento termohidrodinâmico de chumaceiras radiais dotadas de um sulco de alimentação radial. O modelo numérico desenvolvido para o efeito baseia-se no algoritmo de Elrod e permite obter uma solução para a distribuição de pressões hidrodinâmicas na chumaceira. Esta solução é obtida em simultaneidade com a distribuição de temperaturas no fluido, no veio e no casquilho. O procedimento computacional permite simular convenientemente a cavitação, a regeneração e a transferência de calor na chumaceira. As previsões teóricas obtidas são comparadas com resultados experimentais disponíveis na literatura. É discutida a influência de alguns parâmetros de alimentação nas características de desempenho da chumaceira, nomeadamente no caudal e na temperatura máxima., Fundação para a Ciência e a Tecnologia (FCT) - bolsa PRAXIS XXI/BD/13922/97

An experimental study of the influence of applied load and oil supply temperature on the performance of a 100mm plain journal bearing with two axial grooves located at ±90º to the load line has been carried out. Hydrodynamic pressure at the mid-plane of the bearing, temperature profiles at the oil-bush and oil-shaft interfaces, bush torque, oil flow rate and shaft position were measured for variable operating conditions. The applied load varied from 2 to 10kN, whereas the supply temperature ranged from 35 to 50ºC. Bearing performance is strongly dependent on these parameters. It was found that the cooling effect of the downstream groove increases when the applied load increases. The opposite occurs with the upstream groove. Shaft temperature was found to be close to the maximum bearing temperature for low applied loads, but was significantly lower than this value for high loads. The increase in maximum bearing temperature was between 30 and 50% of the corresponding increase in supply temperature., (undefined)