Temperature, flow and eccentricity measurements in a journal bearing with a single axial groove at 90º to the load line

Parametric experiments have been conducted to analyse the influence of some supply conditions on the performance of a steadily loaded journal bearing. Temperature distribution on the internal surface, flowrate and bearing eccentricity were measured for different sets of operating conditions, at variable supply conditions. Quantitative information is provided which shows the effect of both shaft speed and applied load on maximum bush temperature and flowrate. It has been observed that flowrate was modestly affected by load and significantly affected by rotational speed, oil supply temperature and supply pressure. Maximum bush temperature was modestly affected by supply pressure, moderately affected by load and significantly affected by shaft speed. For low applied loads, the attitude angle was markedly affected by supply pressure. The experimental results also showed that for a small groove length there is a variation of bush temperature in axial direction in the groove region.Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI Programme/BD/13922/9

The work on hydrodynamic journal bearings carried out at Minho University in the last 30 years

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

Influence des conditions d’alimentation sur l’amélioration des performances et la réduction du frottement dans les paliers

The performance of hydrodynamic journal bearings is significantly affected by the conditions under which the lubricant is fed to the bearing. However, many conventional analyses are not prepared to suitably incorporate these parameters and their effect on bearing performance, due to the over-simplified way they treat them. A thermohydrodynamic analysis suitable for conveniently deal with lubricant feeding conditions is now presented. It couples the numerical solution of the generalized Reynolds equation, the energy equations within the lubricant film and the heat transfer within the bush body. Special attention has been given to the treatment of the phenomena taking place within the grooves and in their vicinity, as well as to the ruptured film region. The effect that lubricant feed pressure and temperature, groove length ratio, groove width ratio and groove number (single / twin) have on bearing performance has been analyzed for a broad range of conditions. The results were found to be in good agreement with experimental published results and the robustness of the model to suitably treat these phenomena has been confirmed. It was found that a careful tuning of the feeding conditions may indeed improve bearing performance.Les performances des paliers lisses hydrodynamiques sont significativement affectées par les conditions dans lesquelles le lubrifiant est introduit dans le palier. Cependant, de nombreuses analyses classiques ne sont pas prêtes à intégrer convenablement ces paramètres et leurs effets sur les performances des paliers, en raison de la façon trop simplifiée avec laquelle ils les traitent. Une analyse thermohydrodynamique appropriée pour traiter convenablement les conditions d'alimentation de lubrifiant est maintenant présenté. Elle intègre la solution numérique simultanée des équations de Reynolds généralisée, de l'énergie dans le film lubrifiant et de la de chaleur dans le coussinet. Une attention particulière a été portée pour le traitement des phénomènes se produisant dans les rainures et dans leur voisinage, ainsi que dans la région de rupture du film. L'influence de la pression et de la température d'alimentation en lubrifiant, de la longueur et largeur de la rainure et du nombre de rainures (simple ou double) sur les performances du palier a été analysée pour un large éventail de conditions. Les résultats numériques obtenus sont en bon accord avec ceux issus de la littérature expérimentale et la robustesse du modèle à traiter convenablement ces phénomènes a pu être confirmée. Il a été constaté qu'un réglage minutieux des conditions d'alimentation peut effectivement améliorer les performances.FCT - POCTI/EME/39202/2001 & Postdoctoral grant SFRH/BPD/89553/201

On the occurrence of negative groove flow rate in twin groove hydrodynamic journal bearings

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/22278/200

Mudas de Eucaliptus urophylla sob diferentes concentrações de Cr: sintomas de toxidez e efeitos no crescimento / Eucalyptus urophylla cuttings under different concentrations of Cr: toxicity symptoms and effects on growth

Com o objetivo de avaliar os efeitos da toxidez de cromo (Cr) sobre o crescimento e desenvolvimento de mudas de Eucaliptus urophylla, foi instalado um experimento em casa-de-vegetação no Departamento de Ciência do Solo da Universidade Federal de Lavras. Foram utilizadas diferentes concentrações de Cr (0,00; 0,04; 0,08; 0,16; 0,32 e 0,64 mM) fornecido como [Cr(NO3)3.9H2O], em solução nutritiva de Clark. Após cinco semanas de exposição aos tratamentos, as plantas exibiram sintomas de toxidez traduzidos em redução no crescimento, queda de folhas, encurtamento e escurecimento de raízes e com a elevação das concentrações estas se tornavam mais finas e quebradiças. A elevação nas concentrações de Cr na solução nutritiva exerceu efeitos significativos sobre diversos parâmetros vegetativos estudados: altura e incremento em altura, diâmetro e incremento em diâmetro, produção de matéria seca nos quais mostraram redução significativa com o aumento da dose do metal pesado a partir da concentração de 0,08 mM Cr. De maneira geral, a aplicação de Cr acima de 0,08 mM reduz o crescimento de todos os órgãos da planta

Sustainable integration of biofuel generation and domestic wastewater treatment by chlorella vulgaris: Integração sustentável da geração de biocombustíveis e do tratamento de águas residuais domésticas pela chlorella vulgaris

The production of microalgae biofuels has become promising because it is a renewable, non-polluting and non-competitive source such as food growing areas. This work has the objective of using the effluents generated by the Lorena Engineering School - EEL / USP as a growth medium for microalgae of the Chlorella vulgaris species, aiming at lipid production and treatment of effluents. The laps were completed in photobioreactor with effluent from the collection on alternate days. C. vulgaris showed good adaptation to the effluent, reaching a cell density of 1.92x107 cells.mL-1 and a dry biomass concentration of 1.74 g.L-1. The lipid content per gram of biomass was 0.095 to 0.164 mg.g-1. Concomitantly, between 54% and 78.74% of nitrate was dismissed and the chemical oxygen demand (COD) fell between 17.73% and 36.13%. With the results of statistical analysis (ANOVA and Tukey's test). Although lipid has been lower, the success of the microalga Chlorella vulgaris in this sense must have been similar to that of the same

Morphologic and agronomic characterization of basil accessions

O manjericão (Ocimum basilicum L.) pode ser considerado cultura anual ou perene, conforme o local de cultivo. Existem diversas finalidades para seu uso na culinária, como planta ornamental, medicinal e aromática, sendo o seu oleo essencial valorizado no mercado internacional pelo teor de linalol. Caracterizou-se morfológica e agronômicamente, acessos de Ocimum sp. visando a seleção de genótipos com alto rendimento de óleo essencial rico em linalol. O delineamento experimental foi de blocos casualizados, com duas repetições, avaliando 55 genótipos do Banco de Germoplasma de Ocimum da UFS. Avaliou-se a altura de plantas, peso da matéria seca da parte aérea, teor e rendimento de óleo essencial. Observou-se grande diversidade entre os genótipos para todas as variáveis morfológicas e agronômicas avaliadas. Houve grande amplitude entre os genótipos quanto ao teor de óleo essencial, variando de 0,202 a 2,536 ml/100g e para o rendimento de óleo essencial, variando de 1,103 a 21,817 l/ha. Avaliando as variáveis teor e rendimento de óleo essencial de O. basilicum pode-se selecionar os genótipos NSL6421, PI197442, PI358464, PI414194, PI531396 e 'Fino Verde' para o programa de melhoramento genético que visa a obtenção de novas cultivares de manjericão com alto rendimento de óleo essencial rico em linalol. _________________________________________________________________________________________ ABSTRACT: The sweet basil (Ocimum basilicum L.), can be an annual or a perennial plant depending on the place where it is grown. This plant has several culinary, ornamental, medicinal and aromatic uses. The value of its essential oil in the international market depends on the percentage of linalool. We characterized the morphologic and agronomic qualities of the Ocimum accessions, to select genotypes with higher yield of essential oil rich in linalool. Experiment design consisted of randomized blocks with two replications, evaluating 55 genotypes of the Germplasm Bank of Ocimum from the Universidade Federal do Sergipe, Brazil. The plant height, dry matter of the aerial plant parts, essential oil content and yield were evaluated. A wide diversity among the genotypes was observed for all morphological and agronomical traits evaluated. A large amplitude occurred among genotypes regarding the content of essential oil from 0,202 to 2,536 ml/100g. For the essential oil yield an amplitude from 1,103 to 21,817 l/ha was observed. Evaluating the traits content and yield of O. basilicum essential oil the genotypes NSL6421, PI197442, PI358464, PI414194, PI531396 and 'Fino Verde' can be selected for breeding programs to obtain cultivars with a high yield of essential oil rich in linalool

Sorção e lixiviação de tiametoxam em solos tratados com lodo de esgoto e cultivados com cafeeiro

The objective of this study was to evaluate the sorption and leaching of thiamethoxam in dystrophic Red-Yellow Latosol (LVAd), dystroferric Red Latosol (LVdf) and Red-Yellow Argisol (PVAd) with coffee under the effect of sewage sludge doses. There was thiamethoxam sorption decreasing at higher doses of sewage sludge in LVAd and LVdf. In the PVAd, sorption was higher in samples that received the highest dose of sewage sludge. At 150 days after the application of thiamethoxam, the compound began to be detected in the effluent, in all soils. Dissolved organic carbon had no influence on the thiamethoxam leaching

Experimental study of the influence of changes in load direction on the performance of a crown bearing

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 on 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 (4>) with respect to the line of load (4> = 0, -30, and +30 degrees). For each groove location quantitative information is provided concerning to the influence of applied load and shaft rotational speed on the performance characteristics. Changing the location of the groove around theload line did affect flow rate, bush torque and maximum hydrodynamic pressure, but only had a slight effect on bush maximum temperature