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Riffel, Andreas [Verfasser], and Manfred [Akademischer Betreuer] Berg. "Greasers, Gringos und Gräueltaten im mexikanisch-amerikanischen Krieg 1846–1848 / Andreas Riffel ; Betreuer: Manfred Berg." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/1180617061/34.
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Zakani, Behzad. "Rheological characterization of fumed silica lubricating greases." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63863.
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Lubricating greases have been widely used for rail lubrication systems. For an efficient grease pump design, it is important to study grease shear viscosity and it is also crucial to analyze grease yielding behavior to determine its consistency on rail surface. Among all rheological properties measured through experiments, yield stress is an ill-defined property, which investigation of a reproducible method for its determination can be invaluable. As the flow properties of a material will be usually influenced by the changes in environment temperature, studying the effects of temperature on the rheological properties of grease are important.
In this study, different rheological measurements and visualization techniques, previously developed to study a wide range of materials, have been performed to characterize fumed silica based lubricating greases manufactured by L.B. Foster Rail Technologies Corp. Using commercial rheometers and different approaches to determine the yield points of these materials, it was revealed that the values obtained by curve fitting on steady-state flow curves, creep, amplitude sweep crossover and stress ramp-up were roughly similar. The microstructure of this grease was analyzed using Scanning Electron Microscope (SEM) on Cryo and non-Cryo modes. Besides visualizing a new thickener microstructure, it was shown that the heterogeneous structures developed by small fumed silica agglomerates lead to the formation of greases with higher shear viscosities. Finally, thermo-rheological analysis of these samples revealed that these materials follow neither Arrhenius equation nor time-temperature superposition principle.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Gasperi, Renata de Lima Pereira de. "Caracterização de resíduos de caixas de gordura e avaliação da flotação como alternativa para o pré-tratamento." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-12062013-145456/.
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Caixas de gordura são dispositivos para retenção de material gorduroso, de origem animal e vegetal, proveniente de pias de cozinha. Sua instalação é exigida por muitos municípios para liberação de ligações de esgoto, visando reduzir as concentrações de óleos e graxas (OG) lançadas no sistema público de coleta e tratamento. Um fator primordial para que estas caixas cumpram suas funções é o estabelecimento de rotinas de manutenção envolvendo inspeção e limpeza periódica. A instalação de locais para recebimento e pré-tratamento dos resíduos retirados das caixas de gordura pode incentivar boas práticas de operação e manutenção destes dispositivos. Diante disso, os objetivos desta pesquisa contemplam a caracterização de resíduos acumulados em caixas de gordura e a avaliação da flotação como alternativa para o seu pré- tratamento, seguido de caracterização do óleo extraído da escuma produzida no flotador. Para tanto, materiais acumulados em caixas de gorduras de fontes distintas foram caracterizados, possibilitando observar grande variação em sua composição, e elevadas concentrações de DBO, DQO, SST e OG. Para verificar o desempenho da flotação visando à redução de OG no efluente pré-tratado, foram realizados ensaios em bancadas e testados quatro produtos químicos coagulantes, sendo eles o PAC, o cloreto férrico, o tanino e o polímero catiônico. Todos apresentaram eficiências elevadas na remoção de OG, porém o produto que apresentou mais vantagens na aplicação foi o polímero. Utilizando o polímero, foram realizados ensaios para verificação do desempenho de várias dosagens associadas a três pH de coagulação diferentes e o melhor desempenho se deu com a aplicação de 30 mg/L de polímero combinada ao pH 4,3, natural da amostra. Foram também realizados ensaios utilizando diferentes relações A/S (7,5/1000, 15/1000 e 22/1000 gar/gsólidos),obtendo-se melhores remoções de OG com a utilização da relação 22/1000 gar/gsólidos. Os materiais flotados obtidos nos ensaios de avaliação da relação A/S foram caracterizados e apresentaram concentrações de ST entre 9,7 e 10,6% e de OG entre 6,1 e 6,7%. Baseado nos resultados obtidos a flotação mostra-se como alternativa com bom desempenho para o pré- tratamento dos resíduos estudados. Para avaliar a dificuldade do manuseio dos resíduos provenientes de caixas de gordura, uma planta piloto foi operada, e entre as principias dificuldades observadas estão o odor intenso, a necessidade de remoção de sólidos grosseiros e de homogeneização do resíduo no tanque de equalização. Visando reaproveitamento do resíduo flotado, foi realizada a extração do óleo com solvente de uma amostra deste material (com teor de sólidos de 8,86%), obtendo a recuperação de 30g óleo/L resíduo com acidez de 13,76 mg KOH/L. A elevada acidez indica a necessidade de purificação, se o objetivo for a produção de biodiesel.Grease traps are devices that retain animal and vegetal fatty material from kitchen sinks. Many municipalities demand its installation in order to connect house wastewater to the public network, aiming to reduce fat, oil and grease concentration in the collecting and treatment systems. The establishment of maintenance schedule involving inspection and periodic cleaning is a key factor to the right functioning of the device. The existence of appropriated sites to receive and pretreat grease trap wastes may stimulate good practices on maintenance and operation of these devices. In this direction, the objectives of this research are the characterization of grease trap wastes and the evaluation of flotation as an alternative for its pretreatment, followed by characterization of the oil extracted from the scum formed at flotator. Therefore, grease trap wastes from different sources were collected and characterized. It could be observed a wide variation on its composition and high concentrations of BOD, COD, TSS and FOG. Lab scale tests were performed to assess flotation performance to reduce pretreated effluent FOG using four chemical coagulants: PAC, ferric chloride, tannin and cationic polymer. All of them achieved high efficiency on FOG removal, however the product that presented more advantages on application was polymer. More tests were performed using several dosages of polymer associated to three pH coagulation conditions. The combination that resulted in the best efficiency was 30 mg/L of polymer combined to pH 4.3, samples natural pH. Different A/S ratios were also tested (7.5/1000, 15/1000, 22/1000 gair/gsolids), the ratio 22/1000 gair/gsolids presented the best FOG removal efficiencies. Floated material from A/S ratio tests were characterized and presented TS concentrations between 9.7% and 10.6% and FOG was from 6.1% to 6.7%. Based on the obtained results, flotation appears as a high performance alternative for the pretreatment of studied wastes. A pilot plant was operated to evaluate problems related to grease trap waste handling. The main problems were: bad odor, the need of screening and waste homogenization in equalization tank. Aiming to reuse the floated waste, oil was extracted from a sample (8.86% solid content) using solvent, achieving the recovery of 30g oil/L waste with 13.76 mgKOH/L acidity. The high acidity points to the need of purification if biodiesel production is intended.
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Tu, Qingshi. "Fats, Oils and Greases to Biodiesel: Technology Development and Sustainability Assessment." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037796.
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Hill, Desiree. "Twitter: Journalism Chases the Greased Pig." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc30464/.
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The study seeks to find a baseline of Twitter usage of traditional media. Findings suggest that traditional media are using Twitter (a non-traditional medium) in a traditional way. The study explores why a tool like Twitter needs to be approached by journalists in ways to which they may not be accustomed. The study additionally finds that newsrooms are underutilizing Twitter's potential for audience interactivity and have not established guidelines for journalists in the use of Twitter for work purposes. Conclusions include the need for more understanding of Twitter on the part of managers, a usage of Twitter that fits the medium, rather than traditional journalism models and more study in the future so that the journalism business can stay ahead of the curve when new communication technologies are introduced.
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Calderon, Salmeron Gabriel Benjamin. "Enabling More Efficient E-Mobility : Grease Development by a Novel Bearing-Grease Test Machine." Thesis, KTH, Maskinkonstruktion (Avd.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259672.
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The inclusion of electric vehicles in the automotive industry represents an opportunity for lubricating grease producers. Different speed, loads, and electric conditions are present in the bearings of the electric vehicles when compared with the conditions in a traditional internal combustion engine vehicle. Therefore, the development of new grease formulations is desired to overcome these, and other challenges introduced by this new technology. This project aims to compare two grease-thickener technologies through the installation, development, and validation of a novel high-speed bearing-grease test HSBT machine. This rig allows emulating the conditions present in the bearings of an electric vehicle. In this thesis, 6208 deep groove ball bearings were used to compare the mechanical performance of the greases. The comparative study of lithium complex and polypropylene greases was performed through the analysis of the frictional moment and self-induced temperature of the tested grease-bearing combinations. The results present the energy-saving potential of both greases and show the feasibility of using the HSBT machine as a grease testing machine. This project is the first step in an ambitious plan of enhancing e-mobility through grease research. It gives the input for future development of the machine and the creation of new standards for testing electric vehicle greases.Införandet av elfordon i bilindustrin utgör en möjlighet för smörjfettproducenter. Olika hastigheter, belastningar och elektriska förhållanden är närvarande i de elektriska fordonens kullager i jämförelse med förhållandena i ett traditionellt förbränningsmotorfordon. Detta kräver utveckling av nya fetter som kan hantera de utmaningar som uppkommer med denna nya teknik. Detta projekt ämnar jämföra två fettförtjockningstekniker genom att installera, utveckla och validera en ny höghastighetslagermaskin (HSBT-maskin) för smörjfettstestning. Denna maskin möjliggör att förhållanden som finns i lagren hos ett elektriskt fordon kan efterliknas. I denna masteruppsats användes spårkullager med beteckningen 6208 för att jämföra smörjfettens mekaniska prestanda. I denna studie jämfördes litiumkomplex- och polypropenfetter genom att analysera friktionsmomentet och den självinducerade temperaturen för de testade kullagersmörjfettskombinationerna. Resultatet av studien visar energibesparingspotentialen för båda smörjfetterna och visar möjligheten att använda HSBT-maskinen för att testa smörjfetter. Detta projekt är det första steget i en ambitiös plan att förbättra e-mobilitet genom smörjfettsforskning. Studien ger indata för framtida utveckling av elektriska maskiner och bidrar till skapandet av nya standarder för testning av fetter för elektriska fordon.
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Yeong, Shoot Klan. "Rheological properties of lubricating grease." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251581.
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Acharya, Ashwini. "Characterization of spherical boron nitride-filled greases for thermal interface material applications." Diss., Online access via UMI:, 2006.
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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Sciences, Systems Science and Industrial Engineering Department, 2006.Includes bibliographical references.
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Barton, Paul. "Enhancing separation of fats, oils and greases (FOGs) from catering establishment wastewater." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/8052.
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Removal of fats, oils and greases (FOG) from commercial food premises prior to discharge of wash waters into the sewer is critical in restricting blockage events. The FOG droplets that form are commonly removed in passive gravity separators. Enhanced separation through design modification, would allow a reduction in size required to achieve target removal. The aim of the project was to determine the feasibility of enhancing removal of FOGs in gravity separation devices and or in post treatment units. The thesis work examined the effect characteristics of oil droplet size and density had on FOG removal with a view to increasing droplet rise rates and hence separation. Examination of kitchen wastewater from a number of restaurants established that droplet sizes were typically in the mechanically emulsified oil size range, often with high zeta potential indicating electrostatic stabilisation of suspensions. Oil removal rates were examined using different oils typical of food preparations in laboratory scale experiments. Under a fixed energy input the different oils produced different droplet size distributions such that very different separation efficiencies were observed. The removal rates obtained allowed the prediction of oil removal from a sample in a given time when the median droplet size and density of the oil were known. For effective understanding of separator design and testing, droplet densities and sizes must be adequately measured and replicated. In addition, the light fuel oil used in the certification test produced very unstable suspensions, easily separable in the standard testing conditions, proving it a poor surrogate test material. Pre-formed droplets of sunflower oil were treated in a vertically aligned reaction chamber with an ultrasonic transducer fitted at the base. FOG removal, measured as HEM removal, was monitored as a function of power input, frequency, reactor size and residence time, the incoming flow entered counter currently to the ultrasonic wave propagation. The ultrasound treatment procedure removed 80% of oil from a suspension of droplets in the mechanically emulsified oil size range during the course of a 54 minute continuous experiment compared to 20-30% removal in the case of an equivalent separated without ultrasonic enhancement. The enhanced separation was found to be dependent on the power input and the reactor size. Application of ultrasound energy in modified grease separators to remove short-circuiting droplets would allow a reduction in overall size of units through reduced residence time requirement.
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Lunnbäck, Johan. "Hydrodynamic cavitation applied to anaerobic degradation of fats, oils and greases (FOGs)." Thesis, Linköpings universitet, Tema Miljöförändring, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-140685.
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To increase profitability for biogas production, new innovative substrates and condition of operations needs to be implemented. At the current state, fats, oils and greases (FOGs) represent a promising substrate even though it brings operational challenges to the anaerobic digestion process. By utilizing hydrodynamic cavitation (HC) as a pre-treatment of the FOGs, the efficiency of FOGs’ co-digestion with wastewater sludge can be significantly improved. Preliminary experiments conducted on oil and water demonstrates that the HC pre-treatment improves the oil solubilisation as well as forms stable oil and water emulsion that last for several hours. The pre-treatment also improved the soluble chemical oxygen demand (COD) of biosludge (BiSl) by up to 115% and the initial degradation rate by up to 35%. In a semi-continues system, this allowed a significant increment in the specific methane yield depending on the organic loading rate (OLR) applied1. With sufficient process optimization, the HC-pre-treatment may prove to be an energy efficient and effective pre-treatment of FOGs.
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Baart, Pieter. "Grease lubrication mechanisms in bearing seals." Doctoral thesis, Luleå, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26652.
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Rolling bearings contain seals to keep lubricant inside and contaminants outside the bearing system. These systems are often lubricated with grease; the grease acts as a lubricant for the bearing and seal and improves the sealing efficiency. In this thesis, the influence of lubricating grease on bearing seal performance is studied. Rheological properties of the grease, i.e. shear stress and normal stress difference, are evaluated and related to the lubricating and sealing performance of the sealing system. This includes the seal, grease and counterface. The grease velocity profile in the seal pocket in-between two sealing lips is dependent on the rheological properties of the grease. The velocity profile in a wide pocket is evaluated using a 1-dimensional model based on the Herschel-Bulkley model. The velocity profile in a narrow pocket, where the influence of the side walls on the velocity profile is significant, is measured using micro particle image velocimetry. Subsequently, the radial migration of contaminants into the seal pocket is modelled and related to the sealing function of the grease. Additionally, also migration in the axial direction is found in the vicinity of the sealing contact. Experimental results show that contaminant particles in different greases consistently migrate either away from the sealing contact or towards the sealing contact, also when the pumping rate of the seal can be neglected. Lubrication of the seal lip contact is dependent on several grease properties. A lubricant film in the sealing contact may be built up as in oil lubricated seals but normal stress differences in the grease within the vicinity of the contact may result in an additional lift force. The grease, which is being sheared in the vicinity of the contact, will also contribute to the frictional torque. It is important to maintain a lubricant film in the sealing contact to minimize friction and wear. Here the replenishment of oil separated from the grease, also referred to as oil bleed, is of crucial importance. A model is presented to predict this oil bleed based on oil flow through the porous grease thickener microstructure. The model is applied to an axial sealing contact and a prediction of the film thickness as a function of time is made. The work presented in the thesis gives a significant contribution to a better understanding of the influence of lubricating grease on the sealing system performance and seal lubrication conditions.Godkänd; 2011; 20110824 (andbra); DISPUTATION Ämnesområde: Maskinelement/Machine Elements Opponent: Georgia Power Distinguished Professor Richard F Salant, Georgia Institute of Technology, Atlanta, USA Ordförande: Professor Braham Prakash, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå Tid: Torsdag den 22 september 2011, kl 09.30 Plats: E231, Luleå tekniska universitet
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Li, Jinxia. "µPIV Measurement of Grease Velocity Profiles." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17504.
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Lubricating grease is commonly applied to lubricate e.g. rolling bearings, seals and gears. Grease has some clear advantages over lubricating oil. It is a semi-solid material, which prevents it from flowing/leaking out from the lubricated system and gives it sealing properties, protecting the system against contaminants. Unlike oil, grease has a much more complicated rheology, which makes it more difficult to model and understand grease flow. Grease acts as a lubricant reservoir, and understanding grease flow is essential in order to model and predict how grease is transported within e.g., a rolling element bearing housing, a sealing arrangement or replenishment of a gear mesh. Three greases with different rheological behaviors (NLGI 2 grease, NLGI1 grease and NLGI00 grease) have been used in two kinds of test rigs: a straight channel with different restrictions and a rotating shaft with two narrow gap sealing-like restrictions.In the first test rig two types of flow restrictions were applied into a straight channel in order to simulate flow of grease near a sealing pocket. In the case of a single restriction, the distance required for the velocity profile to fully develop when going from a wide to a narrow gap is approximately the same as the initial height of the channel. In the corner pocket before and after the restriction, the velocity is very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving since the yield stress of the grease is not exceeded. This condition particularly applies to the cases with a low-pressure gradient and where high consistency grease is used. In practice this means that grease is not replaced in such “pockets” and that some aged/contaminated grease will remain there. A test rig comprising of a rotating shaft with two narrow gap sealing-like restrictions (a so called Double Restriction Seal, DRS) was designed to simulate the a labyrinth type of seal. Two different gap heights in the DRS have been designed to compare grease flow. It is shown that partially yielded grease is detected in the large gap geometry and fully yielded grease in the small gap geometry. Grease shear thinning behavior and wall slip effects have been detected and discussed. For the small gap geometry, it is shown that three distinct grease flow regions are present: a slip layer close to the stationary wall, a bulk flow layer, and a slip layer near the rotating shaft.Godkänd; 2013; 20130219 (jinlit); Tillkännagivande licentiatseminarium 2013-03-08 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Jinxia Li Ämne: Maskinelement/Machine Elements Uppsats: µPIV Measurement of Grease Velocity Profiles Examinator: Professor Erik Höglund, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Teknologie doktor Henrik Åström, SCANIA, Södertälje Tid: Måndag den 25 mars 2013 kl 10.00 Plats: E231, Luleå tekniska universitet
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Nagata, Yuichiro. "EHD phenomena in grease lubricated contacts." Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6314/.
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This thesis examines the rheological behaviour and film formation of greases and oils under elastohydrodynamic (EHD) conditions. It approaches the lubrication of non-conforming contacts from tribological as well as from dielectric point of view. The experimental work was carried out on a point contact formed between a ball and the flat of a disc, which was either transparent, for optical interferometry study or steel in order to evaluate the conditions in real-life machine components. In the second case electrical capacitance method has been employed to study film formation. The experimental equipment has also been adapted to study the starvation behaviour of grease lubricants in point EHD contacts under vibrations. Dielectric properties of lubricants have been studied in static conditions and correlated to their performance in EHD conditions. The dielectric constant of greases indicates in general higher value than corresponding base oils and the dielectric relaxation time of greases is proved to be shorter. It has been found that in EHD conditions higher-polar greases show higher shear stress, while the dielectric constant of the lubricating film decreases with increasing contact pressure. The effect of three parameters upon grease EHD films was evaluated: operating speed, load and vibration of the contact. The results showed that greases possess an intrinsic time to starvation related to the operating speed but independent of the exerted load. The results also showed that a high speed was not necessarily associated with the high likelihood of occurrence of starvation. The vibration tests revealed that the lateral motion perpendicular to the rotating direction helped maintain the inlet region flooded and, under oscillations, starvation of the contact seems to never occur. This would suggest that machine elements such as rolling element bearings could operate under the fully flooded conditions as vibrations are almost inevitable in any machinery. Finally, the cavitation phenomenon was also investigated and found that the rheological model of greases could be predicted from the observation of the cavity pattern.
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Baart, Pieter. "Grease lubrication in radial lip seals." Licentiate thesis, Luleå : Luleå University of Technology, 2009. http://pure.ltu.se/ws/fbspretrieve/2760890.
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TORRES, NATALIA. "Graxa de poliuréia- estudo da compatibilidae da poliuréia, polialfaolefina e politetrafluoretileno irradiado para melhoria da lubricidade e estabilidade." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10609.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Hurley, Susan Rebecca. "Fundamental studies of grease lubrication in elastohydrodynamic contacts." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342330.
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Rincon, Guillermo. "Kinetics of the electrocoagulation of oil and grease." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/131.
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Research on the electrocoagulation (EC) of hexane extractable materials (HEM) has been conducted at the University of New Orleans using a proprietary bench-scale EC reactor. The original reactor configuration forced the fluid to follow a vertical upward-downward path. An alternate electrode arrangement was introduced so that the path of flow became horizontal. Both configurations were evaluated by comparing the residence time distribution (RTD) data generated in each case. These data produced indication of internal recirculation and stagnant water when the fluid followed a vertical path. These anomalies were attenuated when the fluid flowed horizontally and at a velocity higher than 0.032 m s-1 . A series of EC experiments were performed using a synthetic emulsion with a HEM concentration of approximately 700 mg l-1. It was confirmed that EC of HEM follows first-order kinetics, and kinetic constants of 0.0441 s-1 and 0.0443 s-1 were obtained from applying both the dispersion and tanks-in-series (TIS) models, respectively. In both cases R2 was 0.97. Also, the TIS model indicated that each cell of the EC behaves as an independent continuous-stirred-tank reactor.
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Mass, Igor, Andreas Hoppermann, and Hubertus Murrenhoff. "Control concept for a grease lubricated hydrostatic bearing." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71086.
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In industrial practice greases are mainly used as lubricants in hydrodynamic plain bearings and roller bearings. The use in hydrostatic bearings is avoided due to the difficult controllability. One reason is the complex non-Newtonian flow behavior of greases. The motivation for this paper is the use of greases to increase the efficiency of hydrostatic bearings. The assumption is that the so-called yield stress of consistent greases can lead to self-sealing behavior in the bearing under stationary operation conditions. Assuming a volume-flow-free operation of the bearing, a concept for the active control of the sealing gap height and thus the bearing stiffness was developed. The concept idea is the use of a second medium with Newtonian characteristic for pressure transfer. The grease and the pressure control fluid are structurally separated. The grease is induced in the shortest possible way into the bearing pocket to keep the pressure losses as low as possible. The results of test bench investigations indicate the feasibility of a gap height control with very high bearing stiffness under use of highly consistent greases and initiate further investigation on non-stationary operation.
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Saatchi, Alireza. "The Effect of Grease Composition on Fretting Wear." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1533075463914892.
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Zhang, Junsong. "Utilization of Fats, Oils and Greases in Biodiesel Production: From to Market Study to Technical Feasibility." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1511801164066707.
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Wang, Jingjing. "Feasibility Study for a Community Scale Conversion of Trap Grease to Biodiesel." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1330024170.
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Lu, Xue Fen. "Wool scouring and sludge incineration." Thesis, University of Huddersfield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368210.
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Sahin, Huseyin. "Theoretical and experimental studies of magnetorheological (MR) fluids and MR greases/gels from rheology to system application /." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3339143.
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Houara, Komba Eymard. "Reconstitution of tribological accommodation mechanisms for greased high loaded oscillating bearings." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI018.
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Les roulements soumis à des mouvements oscillatoires et des charges élevées sont nécessaires pour le fonctionnement de nombreux mécanismes industriels (actionneurs, commandes d’avions, machines pour l’usinage, robots, chaînes d’assemblages, …). Ces roulements sont soumis à des pressions de contact locales extrêmement élevées avec des vitesses de roulement faibles qui ne permettent pas une lubrification adéquate des interfaces des premiers corps avec de l’huile. Les essais d’endurance sur les roulements ont permis la reconstitution des courbes de dégradation pendant la vie du roulement. Des analyses des surfaces, effectués à chaque phase de la vie du roulement ont permis aussi bien de suivre l’évolution de la topographie à l’interface entre les pistes et les éléments roulants. D’autre parte, des analyses numériques par éléments finis ont permis d’obtenir des informations sur les distributions des contraintes et des déformations. Le croisement des résultats expérimentaux et numériques a donc permis la reconstruction des mécanismes locaux d’accommodation. Dans le cas d’un roulement oscillant non graissé, les déplacements relatifs et les contraintes sont principalement accommodés aux interfaces des premiers corps en contact, ce qui accélère l’endommagement final du roulement. Dans le cas d’un roulement oscillant graissé, une partie des déplacements relatifs et contraintes est accommodée dans une sous couche qui se forme dans la peau des éléments roulants. Cette accommodation se manifeste par l’accumulation de déformations plastiques qui s’avèrent être aussi à l’origine de l’endommagement final du roulement. L’analyse des surfaces de contact des roulements oscillants graissés montre qu’il se forme, en présence de la graisse et très tôt dans la vie du roulement, une couche (troisième corps graisse/particule et TTS en surface de la piste) qui protège les surfaces en contact. D’autre part, une expertise de roulement ayant fonctionné sur un avion de de type A340 révèle une forte similarité entre ses faciès d’usure et ceux obtenus lors des essais d’endurance, et valide ainsi les mécanismes d’accommodation reconstitués. Enfin, des questions portant sur les effets de la quantité de graisse, du glissement des éléments roulants, et des pauses sur un essai donné sont aussi traitéesBearings subjected to oscillatory motions and high loads are necessary for the operation of several industrial mechanisms (actuators, aircraft controls, machining, robots, assembly lines, ...). These bearings are subjected to extremely high local contact pressures with low running speeds, which do not permit adequate lubrication of the interfaces of the first bodies with oil. Endurance tests perfomed on commercial bearings allowed at reconstructing the evolution of the degradation curves during the bearing life. Surface analyses carried out at each phase of the bearing life also allowed at following the evolution of the topography at the interface between the bearing raceways and the rolling elements. On the other hand, numerical analyses, by finite element method, have led to obtain information on the distributions of stresses and deformations. The dialogue between experimental and numerical results allowed the reconstruction of the local accomodation mechanisms. In the case of ungreased oscillating bearings, the relative displacements are mainly accommodated at the surfaces of the first bodies in contact, which accelerates the damage of the bearing. In the case of greased oscillating bearings, part of the relative displacements and stresses are accommodated at the subsurface of the rolling elements. This accommodation mechanism is manifested by the accumulation of plastic deformations which are at the origin of the final degradation of the bearing. The analysis of the contact surfaces of the raceways of the greased oscillating bearings shows as well that, in the presence of grease, a layer (third body mixture of grease and particles, and TTS on the track surface) protects the surfaces of the raceway and thus accommodates the other part of the displacements and stresses. On the other hand, the analysis of an airelon bearing, dismounted from an A340 type aircraft, revealed a strong similarity between its topographies and those obtained during the performed endurance tests, validateing the reconstructed accommodation mechanisms. Finally, questions about the effects of the amount of grease, sliding of the rolling elements, and pauses on a given test heve been discussed too
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Ripard, Valentin. "Tribological characterization of greased drive-shaft : Evaluation of constant velocity joint durability." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI083.
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La modification des besoins clients amène les constructeurs automobiles vers de nouveaux challenges. En effet, en Europe notamment, les véhicules rehaussés type SUV (Sport Utility Vehicle) sont de plus en plus populaires. Or, ces véhicules impliquent une modification de l’implantation des transmissions mécaniques. Ces dernières possèdent alors une angularité plus élevée que pour des berlines par exemple. Cette modification a alors 2 impacts : l’augmentation du glissement dans la transmission mais aussi son influence sur la durabilité des composants. La modification de l’angularité est un des enjeux majeurs de ces dernières années pour les constructeurs. En effet, son augmentation influe sur le rendement des transmissions. Or, avec des normes environnementales de plus en plus contraignantes mais aussi une hausse du prix du pétrole, cet axe d’amélioration représente un facteur d’attractivité pour les constructeurs. De plus, la durabilité des organes reste primordiale. Une voiture se doit d’avoir une transmission fiable ne nécessitant, pour le cas des joints homocinétiques, aucun entretien durant la vie du véhicule. C’est sur cet axe que les travaux suivants ont majoritairement porté. L’objectif de ce manuscrit est de comprendre le mécanisme d’usure des joints homocinétiques côté boîte dits tripode. Une analyse de la cinématique a d’abord été menée afin de reproduire les contacts sur des bancs d’essais. Elle s’est appuyée sur des données issues de la bibliographie mais aussi une simulation de la dynamique des solides. De plus, la création en fabrication additive d’un banc d’observation a permis d’évaluer de façon expérimentale le glissement dans cet organe de transmission. Par la suite, une caractérisation des graisses de transmission utilisée dans le groupe PSA a été effectuée afin de connaître les coefficients de frottement induisant le niveau de vibrations de la transmission pour un client. Ces derniers sont essentiels pour juger l’efficacité énergétique de l’organe. Enfin, une étude de l’usure a permis d’expliquer les mécanismes de défaillance de la lubrification avec des graisses proposant des propriétés mécaniques. Cela permet alors de comprendre les données-clés afin de choisir une graisse assurant une durabilité maximale des organes de transmission et remplissant alors un des deux enjeux cités ci-dessus. Pour le futur, un banc de caractérisation des lubrifiants spécialement conçu pour les contacts de joint tripode a été créé. Il permettra ainsi de caractériser de façon plus complète les lubrifiants du futur pour cet organe essentiel d’une voitureNew customer desires are leading car manufacturers to new challenges. Indeed, enhanced vehicles like SUV (Sport Utility Vehicle) becomes more and more popular, especially in Europe. These vehicles involve some modification over the usual mechanical transmissions designs. This vehicle type has a higher angularity than sedans for example. This desire modification has 2 impacts: the increase of slipping in the transmission and its influence on the durability of the components. The angularity modification remains one of the major lines of research in recent years for car manufacturers. Its increasing influences efficiency. Indeed, this axis of improvement is attractive for manufacturers due to new environmental standards but also an increase in oil price. In addition, a car must have a reliable transmission that does not require, in the case of constant velocity joints, any maintenance during vehicle life. The following work will focus on this objective. The main goal of this manuscript is to understand the wear mechanism of the tripod constant velocity joint (CVJ). An analysis of the kinematics was first conducted to reproduce contacts on test rigs. It relied on data from the bibliography but also a simulation of solid dynamics. In addition, the design of a new observation rig using additive manufacturing made it possible to experimentally reproduce slipping in tripod. Furthermore, a characterization of greases used in Groupe PSA transmissions was performed in order to know the friction coefficients inducing the shudder level of the CVJ. These are also essential in order to judge the efficiency of the component. Finally, a wear investigation is performed to explain the possible lubrication failure mechanisms with greases proposing different mechanical behaviour. This approaches enables the transmission designer to choose a grease ensuring maximum durability of transmission components. Looking ahead, a lubricant characterization rig specially designed for tripod joint contacts has been designed. It will thus allow a more complete characterization of further lubricants to this essential vehicle component
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Collins, Stephen. "Studies on the natural fluorescence of wool and wool grease." Thesis, City University London, 1992. http://openaccess.city.ac.uk/7894/.
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The principal aims of the work were to further the current knowledge of the natural fluorescence of wool and wool wax, to characterise the species responsible and to thoroughly investigate the light induced changes. The natural visible fluorescence of Merino fibres was found to vary along the length of the fibre, from highly fluorescent tips to barely fluorescent roots. It would appear that the same species' are responsible for the fluorescence at the tip and root. An increased level of fluorescence was observed when the disulphide bonds of cystine were oxidised to cysteic acid residues, due to the removal of the quenching disulphide bond. Each of the morphological components examined (cuticle, cortex and cell membrane complex) were fluorescent. Chemical bleaching treatments caused an increase in the fluorescence intensity of the components, with the same emitting species being responsible as in the nonbleached. Fluorescent lamps and laser irradiation were used to investigate the (different) effects of UV and blue light upon the fluorescence intensity of wool. UV irradiation caused a rapid increase in intensity which was accompanied by a definite protective effect being exhibited by the wool yolk. The enhancement of the white appearance in photobleached wool is not due to the production of UV absorbing species which exhibit blue fluorescence, but to the destruction of yellow Coloured residues. Northlight fluorescent lamps led to no change in the level of fluorescence whereas blue laser light caused a decrease. The level of natural fluorescence decreased when wool, embedded in immersion oil or glycerol, was irradiated with UV light. The effect of four reducing agents on wool was investigated:in the presence of UV irradiation, blue light irradiation and in the dark. The agents fell into two groups. The first group (Rongalit C and sodium hypophosphite) had little effect on their own but in the presence of irradiation retarded the effect of light. The second group (BlankitD andt hiouread ioxide)h ada n effect on their own and upon irradiation acted as photosensitisers causing extensive photobleaching. The difference between the two groups was attributed to the pH of the solutions used. The whitenin gobserved was (generally)d uet o the destruction of visible absorbing chromophore rsather than to the production of UV absorbing chromophore which exhibit blue fluorescence. Wool yolk is highly fluorescent. The amount of wool yolk/intensity of wool yolk fluorescence was found to vary along a Merino wool fibre from 'zero' at the tips to intense at the roots. The fluorescence of wool grease consists of two components - 'grease' and chlorophyll. The 'grease' fluorescence reveals the presence of a number of chromophores/components. An attempt to isolate these was only partly successful. Chlorophyll could be detected in all the wool greases examined. Weathering was found to result ultimately in a decrease in the fluorescence intensity arising from both the 'grease' and chlorophyll components. UV irradiation revealed that complex photochemical reactions were occurring. The role of wool yolk in the photoyellowing of wool in nature was investigated. Using special conditions no migration of fluorescent probes (models for photosensitisers) into the wool structure could be observed. The 'swelling' solvent, toluene/methanol (9: 1) was found to act as a photosensitiser.
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Martinsdotter, Linnea. "Fiber based biocomposite material with water and grease barrier properties." Thesis, KTH, Fiber- och polymerteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298184.
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Syftet med denna studie var att utveckla en biokomposit med både fett-och vattenbarriär. Material med dessa egenskaper innehåller idag ofta PFAS-molekyler (per- och polyfluorerade alkylsubstanser). Det är av stor betydelse att byta ut dessa mot ett biobaserat alternativ då de är giftiga och ackumuleras i naturen. Biokompositen utvecklades genom att kombinera icke-trä pappersmassa (75%) och trä pappersmassa (25%) som matris. Därefter tillsattes olika biobaserade additiv i våtände för att påverka materialets egenskaper. Proverna testades på deras dragstyrka, vattenavvisning och fettavvisning. Den stora utmaningen var att lyckas med fettavisningen. 1% Polysackarid 1 tillsammans med 0.5% sizing komponent var det provet som gav bäst resultat. För att utvärdera denna metod gjordes en jämförelse med ytbehandling. Det gjordes genom att stryka på några av de tidigare använda additiven på ytan av matrisen. Ytbehandlingen visade sig ha en större påverkan på fettavvisningen men med liknande eller sämre påverkan på vattenavvisningen. Nackdelen med denna metod är att den kräver ett flertal extra steg i produktionen.The aim of this thesis work was to develop a pulp-based biocomposite material with good water and grease barrier properties. It is important to achieve such properties to able to replace PFAS (poly- and perfluoroalkyl substances) molecules due to their toxicity and accumulation. Different types of pulp were evaluated as the matrix and the optimal matrix was based on non-wood pulp (75%) with wood pulp 1 (25%). This was also combined with several different additives in the wet-end. The samples were tested for their tensile strength, water resistance and grease resistance. The biggest challenge was to achieve adequate grease resistance. 1% Polysaccharide 1 together with 0.5% sizing agent was one of the better samples. It was clear the additives affected each other when used in combination with each other which indicates that wet end chemistry is complex. For a comparison, some additives were also tested as coatings. This technique resulted in better grease resistance but requires several extra steps in the production.
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Duong, Hanh To. "OPTIMIZING BIODIESEL PRODUCTION FROM YELLOW GREASE USING PASSIVE SOLAR HEATING." Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192320.
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Kain, Stephanie Linn. "OPTIMIZING BIODIESEL PRODUCTION FROM YELLOW GREASE USING PASSIVE SOLAR HEATING." Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192510.
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Wilson, Steve Jason. "Traction and Wear Evaluation of a Number of Plastic Materials and Greases under Combined Rolling and Sliding Contact Conditions." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337191253.
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Dittes, Nicholas J. "Condition Monitoring of Water Contamination in Lubricating Grease for Tribological Contacts." Licentiate thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25635.
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The purpose of this thesis is to summarize the research carried out that led to the development of measurement techniques which measure the water content of lubricating grease. A simple and effective grease mixing method for preparing grease samples was developed and tested for repeatability. Calcium sulphonate complex (CaS-X) grease was used in all experiments. The water content of these samples were also tested with time and temperature as added variables to study if and how much water will evaporate from the samples. Additionally, two measurement techniques were investigated: optical attenuation in the visible and near-infrared (NIR) region and with a dielectric measurement method. The optical attenuation investigation found that the attenuation ratio of two wavelengths of light appear to approximate the water content of grease samples with an acceptable coefficient of determination. Additionally, aged and oxidized grease were measured as well and were not found to affect the measurement results. The dielectric method uses the temperature dependence on the dielectric properties of water-contaminated grease to approximate the water content of the grease samples. An additional parameter of incomplete fill/coverage of the sensor has been investigated as a prestudy. Both methods were found to provide measurements of water content in the prepared grease samples (ranging from 0.22% to 5.5% added water). The dielectric measurement is likely going to be better for applications requiring the possibility of measuring a larger bulk of the grease within the bearing. It shows promise for providing an accurate and robust system for monitoring grease condition as well as the amount of grease contained. The optical measurement will likely provide additional information; however, it will only measure small point samples within the bearing instead of the larger bulk. This could be of use though, because the sensors could be small (in the several millimeter scale) and could measure where water damage is determined to be most important to detect at.
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Trefler, Caroline. "Dickens and food : realist reflections in a puddle of chicken grease." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24107.
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Food has a near-ubiquitous role in the fiction of Charles Dickens. From the action that does and does not take place, to the appearance and essence of the characters, and to the language and style in which they were written, virtually every aspect of Dickens's novels and short stories is, to some extent and at one time or another, connected with food. This thesis explores the nature and implications of food in Dickens and, in addition to its introduction and conclusion, it has been divided into three chapters: (a) Language, Style, and Subject/theme; (b) Plot and Setting; and (c) Characterization. As well, the parallel between food's omni-presence in Dickens's fiction and its centrality in the so-called 'real world' has meant that the literary concept 'realism' is a recurrent concern.
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Kwong, Kai-chi Linda, and 鄺佳慈. "New approaches to oil and grease waste management in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31255875.
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Venter, Roelof Jacobus. "Process grease : a possible feedstock for biodiesel production / Roelof Jacobus Venter." Thesis, North-West University, 2013. http://hdl.handle.net/10394/9729.
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The utilisation of waste process grease (WPG) as feedstock for biodiesel production was investigated in this study. WPG is a lubrication oil used in the metalworking industry and is considered a hazardous waste material. WPG contains vegetable oil and animal fat which are used as base oils in the lubricant formulation.
Three different production routes were followed to produce biodiesel using WPG as feedstock. The first production route involved the conventional two-step production process comprising the acid esterification of the free fatty acids, followed by alkaline transesterification. The second production route involved the extraction of free fatty acids in the WPG by means of liquid-liquid extraction and the production of biodiesel from the extracted free fatty acids through acid esterification. The produced biodiesel was purified by means of chromatography. A third process route was the saponification of the WPG using aqueous sodium hydroxide followed by acidulation with hydrochloric acid. The resulting acid oil was purified by means of column chromatography, using a hydrophobic resin as the stationary phase prior to esterification through acid catalysis to produce biodiesel. The crude biodiesel was purified using column chromatography with silica gel as stationary phase.
The optimum reaction conditions for the reduction of the free fatty acid content of WPG in route 1 to 0.5% were a methanol to oil ratio of 8:1 and a reaction temperature of 65 °C with a catalyst loading of 4 wt%. Acetonitrile was found to be the most effective extraction solvent for the reduction of sulphur compounds in the free fatty acid feedstock in route 2. A reverse phase chromatographic system with a hydrophobic stationary phase and methanol as the mobile phase was found to be an effective system to reduce the sulphur to below 10 ppm as specified by the SANS 1935 biodiesel standard in route 3.
Both the conventional two-step process (route 1) and the liquid-liquid extraction process (route 2) were found not to be suitable for the production of biodiesel from WPG as the sulphur content of the produced biodiesel for routes 1 and 2 was 8 141 ppm and 4 888 ppm, respectively. The sulphur content of the produced biodiesel following route 3 was 9 ppm. The latter approach reduced the sulphur content of the biodiesel to acceptable levels that conform to the SANS 1935 standard to be used in a B10 biodiesel blend. A biodiesel yield of 45%, calculated as the mass of biodiesel produced as a percentage of the total mass of dried WPG used, was achieved with route 3. The biodiesel conformed to most of the specifications in the SANS1935 standard for biodiesel. The presence of a relatively high concentration of saturated fatty acids reflected in the higher cetane number of 74.7, the high cold filter plugging point of +10 and the oxidative stability of > 6 hours. A comparative cost analysis for route 3 indicated that the production cost of biodiesel, compared to the cost of petroleum diesel is marginally higher at the current Brent crude oil price of $102.41 per barrel. The production of biodiesel from WPG will be economically viable once the crude oil price has risen to about $113 per barrel.Thesis (PhD (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013.
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Pearson, Michael Patrick Robert. "Grease monkeys : A history of Australia's motor mechanic trade, 1900-1970." Phd thesis, Australian Catholic University, 2021. https://doi.org/10.26199/acu.8xqy1.
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Motor mechanics are iconic members of Australia’s working class. The timeless imagery associated with them, of men in grease-stained overalls – colloquially called ‘grease monkeys’ from the 1930s – hides a complex history.
This thesis explores how class structures affected the organisation of the motor mechanic trade. The first motor mechanics emerged from across the social divisions of class, race and gender. A demand for mechanics’ engineering skills created avenues of social mobility. The diversity of motor mechanics in the early years of automotive repair work also inhibited solidarity and their ability to organise. As a result, the organisational structures that governed the trade were imposed by multiple outside groups. Motorist organisations, employer associations, technical colleges and multiple trade unions all vied to advance their interests and gain control over automotive work. This affected both mechanics’ class positioning and social status.
Issues of skill are crucial here. Mechanics initially relied upon an unstructured, ad hoc education, based around practical learning. This changed in the interwar years, as technical colleges began offering courses in automobile repair. The formalisation of motor mechanics’ education that took place from this period affected more than their skills. Accreditations defined who could qualify as a mechanic. These were responsible for the initial gendering of the trade, as women were excluded from trade colleges. Changing gender norms following the Second World War acted in combination with the introduction of accreditations to set boundaries, both in terms of who could become a mechanic and the skills deemed relevant to the trade. This culminated in a broad deskilling program, enforced at the at the behest of employers which diminished mechanics’ expertise and affected their financial remuneration. This thesis explores the connections between these different aspects of the motor mechanic trade to extend our understanding of Australian class structures.
Engaging with a broad range of sources, this thesis incorporates archival records, interviews, newspapers, and trade journals. It integrates aspects of labour, economic, educational and gender history to provide historical context to our current understanding of mechanics. In turn, it contributes to debates regarding the right to repair, a grassroots movement of American origins that seeks to protect independent repairers, and the future of maintenance work.
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Li, Jinxia. "Lubricating grease Experiments and modeling of wall-bounded- and free-surface flows." Doctoral thesis, Luleå tekniska universitet, Maskinelement, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26489.
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Lubricating grease is commonly applied to lubricate e.g. rolling bearings, sealsand gears. Grease has some clear advantages over lubricating oil: it is a semisolidmaterial, which prevents it from flowing/ leaking out from the bearingsystem and gives it sealing properties, and it also protects the system fromcontaminants and corrosion. Due to its consistency, lubricating grease has manyadditional advantages over lubricating oil: it does not require pumps, filters andsumps. However, the rheology of grease makes it more difficult to measure andstudy its flow dynamics. This study focuses on the influence of rheology ongrease flow in different geometries involving a straight channel with restrictions,concentric cylinder geometry, and free-surface flow on a rotating disc.To better understand grease flow in bearings and seals, two types of flowrestrictions were applied into the straight channel in order to simulate the flowof grease near a seal pocket. In the case of a single restriction, the horizontaldistance required for the velocity profile to fully develop is approximately thesame as the height of the channel. In the corner before and after the restriction,the velocities are very low and part of the grease is stationary. For the channelwith two flow restrictions, this effect is even more pronounced in the narrowspace between the restrictions. Clearly, a large part of the grease is not moving.This condition particularly applies in the case of a low-pressure gradient andwhere high-consistency grease is used. In practice this means that grease may belocally trapped and consequently old/contaminated grease will remain in theseal pockets.A configuration comprising a rotating shaft and two narrow gap sealing-likerestrictions (also called Double Restriction Seal, DRS) was designed to simulatea sealing contact. Two different gap heights in the DRS have been used tocompare the grease flow. It is shown that partially yielded grease flow isdetected in the large gap geometry and fully yielded grease flow in the small gapgeometry. For the small gap geometry, it is shown that three distinct grease flowregions are present: a slip layer close to the stationary wall, a bulk flow layer,and a slip layer near the rotating shaft. The shear thinning behaviour of thegrease and its wall slip effects have been determined and discussed.Free-surface flow of grease occurs in a variety of situations such as during relubrication and inside a rolling element bearing which is filled to about 30%with grease in order to prevent heavy churning. Here the reflow of lubricant tothe bearing races is a key point in the lubricant film build-up, and centrifugalforces have a direct impact on the amount of available grease. Understanding ofthe free-surface flow behaviour of grease is hence important for theunderstanding of the lubrication mechanism. Adhesion and mass loss aremeasured for greases with different rheology on different surfaces andtemperatures. It is shown that the critical speed at which the grease starts tomove is mostly determined by grease type, yield stress and temperature ratherthan surface material. A developed analytical model covers a stationary analysisof the flow resulting in solutions for the velocity profile of the grease as well as asolution for the thickness of the viscous layer remaining on the disc.Godkänd; 2014; 20141017 (jinlit); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Jinxia Li Ämne: Maskinelement/Machine Elements Avhandling: Lubricating Grease Experiments and Modellingo f Wall-Bounded and Free-Surface Flours Opponent: Professor Arto Lehtovaara, University of Technology, Tampere, Finland Ordförande: Professor Erik Höglund, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Fredag den 19 december 2014, kl 09.00 Plats: E632, Luleå tekniska universitet
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Outram, Alan Keith. "The identification and palaeoeconomic context of prehistoric bone marrow and grease exploitation." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/1432/.
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Young, Bradley. "Enhancement of the Mesophilic Anaerobic Co-digestion of Municipal Sewage and Scum." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23530.
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Scum is an integral component of solids management in MWWTP and is composed of fats, oils, grease and other entrained floatable materials that are collected during primary clarification. Lab scale BMP tests showed the addition of 14.5 g VS/L of scum exhibited the greatest increase in biogas production of 1.6 times per g VS added compared to the control, while a higher additional scum loading of 33.7 g VS/L reduced the biogas yield to 32% of the control reactor. Lab scale semi-continuous digestion measured the effects of scum loading and temperature of pretreatment in the scum concentrator. At 15 d and 20 d HRTs the greatest observed improvement in biogas was achieved by adding 3% scum by volume and pretreating the scum at 70°C in a scum concentrator with respective improvements of 24% and 16%.
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Sakai, Kazumi. "Study of Correlation between Grease Film Formations and Mechanical Losses on Various Surfaces." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-383527.
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Tato disertační práce se zaměřuje na studium závislosti mezi reakčním momentem ložiska mazaného plastickým mazivem s lithným mýdlem a vlastnostmi maziva, jako například tloušťka vytvářeného mazacího filmu, jeho reologie, struktura zpevňovadla, trakční vlastnosti či vliv topografie povrchu. Typ maziva poskytujícího nižší odpor závisí na podmínkách provozu ložiska, zejména rychlosti. Chování mazacího filmu za nízkých rychlostí má vliv na reakční moment ložiska v nízkých rychlostech. Mez toku a trakční chování koreluje s momentem ložiska za vysokých rychlostí. Schopnost zpevňovadla vstupovat do kontaktu má vliv na tloušťku filmu, vzhled kavitační oblasti na výstupu kontaktu a chování hladovění. Důvod vstupu zpevňovadla do kontaktu je jeho chemická struktura. Vysoká polárnost hydroxylových sloučenin zpevňovadla podporuje jeho vtažení kontaktními povrchy. Mazivo s nejvyšší polaritou prokázalo na površích obsahujících denty nejčastější vstup do prostoru dentů. Na základě předchozích pozorování je navržen popis principu mechanismu mazání.
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Navrátil, Marek. "Vliv stárnutí plastického maziva na jeho chování v blízkém okolí elastohydrodynamického kontaktu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400948.
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This thesis aims to describe the differences in grease behaviour caused by degradation. Observation of EHL contact and its surroundings is done using optical fluorescence, which allows to measure lubricant thickness even if it is discontinuous and air is present. New grease is observed, along with samples aged in bearings. One sample was worked for 1000 hours, which was the planned duration of the experiment. Two other samples were stopped prematurely after approx. 900 hours. Several possible age-related factors were examined and strong link between contamination and grease behaviour was found. In observed cases, contamination was identified to be the leading cause of lubricant shortage near EHL contact, which is one of possible bearing failure causes. The results expand existing knowledge about grease lubrication topic, but much further research is needed.
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De, Laurentis Nicola. "An experimental study into the influence of grease composition on friction in EHL contacts." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/56198.
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Rolling bearings are among the most widely used machine elements. As a result, reducing bearing frictional losses can have a significant impact on the overall energy efficiency of the vast majority of engineering systems. Given that rolling bearings are typically lubricated with grease, one of the most effective ways to improve bearing efficiency is through a suitable grease formulation. However, at present there is a lack of understanding of grease frictional behaviour in typical non-conformal, highly stressed bearing contacts. This limits the development of low-friction bearing greases, and thus further improvements in bearing efficiency. The current research work attempts to address this topic through an experimental investigation. Friction and film thickness tests were conducted on a wide selection of greases in ball-on-disc tribometers, under conditions broadly representative of rolling bearing contacts. Initial work was carried out with a series of commercially available greases, selected to cover a wide spectrum of thickener types, base oil types and viscosities, and practical bearing applications. These tests served to identify the most influential aspects of grease formulation on friction, and provide a reference line in terms of the current state of the art in low-friction bearing greases. Subsequently, the work was focussed on the study of a series of custom lithium-thickened greases. These were designed and manufactured with the purpose of isolating and investigating the effects of particular aspects of interest in grease formulation, including base oil type, base oil viscosity and the presence of friction modifiers. In addition, the performance of the corresponding bled and base oils was also studied to help shed some light on the prevailing mechanisms. The results show that two distinct operating regions, at high and low speeds, can be identified in the tribological performance of greases. At high speed greases behave approximately as their base oils. In this region, oil type was found to be the major parameter of influence on friction, with synthetic oils (particularly PAO) providing the lowest friction coefficients. In the same high speed region, the influence of base oil viscosity is that expected from a classical Stribeck relationship for oils, i.e. higher base oil viscosities in the grease formulation tend to produce higher friction as a result of thicker films. In contrast, at low speed grease behaviour is much more complex and is strongly influenced by both base oil and thickener properties. In this region the combination of lithium and PAO was shown to provide both thick films and low friction. No benefit in friction reduction was observed when a friction modifier, namely oleic acid, was added to the formulation of the greases. The influence of mechanical degradation of greases on their tribological performance was also evaluated. It was established that mechanical degradation has the effect of diminishing the friction and film thickness benefits provided by some of the greases at low speeds. A remarkable exception was found in the tribological behaviour of greases formulated with lithium and PAO oil, which was overall practically unaffected by mechanical degradation. Finally, based on the observed results, the combination of a low viscosity PAO base oil and lithium thickener was suggested as the most suitable formulation for a low-friction rolling bearing grease.
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Langridge, David Anthony. "The effect of sebaceous grease and hair colour on the mechanism of hair removal." Thesis, Liverpool John Moores University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505929.
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Charles, (nee Lapsirikul) Wipa. "Anaerobic bioflocculation as a mechanism for the removal of grease from wool scouring effluent." Thesis, Charles (nee Lapsirikul), Wipa (1994) Anaerobic bioflocculation as a mechanism for the removal of grease from wool scouring effluent. PhD thesis, Murdoch University, 1994. https://researchrepository.murdoch.edu.au/id/eprint/39184/.
Full textAbstract:
Effluent produced by the wool scouring process is highly polluted with emulsified grease, dirt particles, salts, and detergent. The major problem in treating this waste stream is the wool grease which is resistance to biodegradation. The removal of grease from the effluent would lead to a more readily degradable waste stream, and therefore suitable for further biological treatment processes. This study aimed to investigate anaerobic destabilisation (flocculation), rather than degradation, of wool grease emulsion from wool scouring effluent (WSE). The process therefore can serve as a pretreatment step, prior to a conventional biological process.
The results from this study show that emulsified wool grease in WSE could be removed by bioflocculation under anaerobic conditions. After 110 days of continuous operation, a two-stage anaerobic process treating a high grease (> 10 g/L) effluent removed 70 to 90% grease and approximately 60 to 86% COD at a combined hydraulic residence time (HRT) of 4 to 10 days. With low grease (<10 g/L) effluent grease removal was reduced. At a HRT of 3 days a single stage anaerobic process removed 40 and 44% grease (37 and 43% COD) at 20 °C and 37 °C respectively. Since the supernatant of the treated effluent still contained residual grease of over 1.5 g/L, further purification was necessary. The supernatant was readily treated by an aerobic activated sludge process, reducing the grease concentration from about 1.5 g/L to less than 0.1 g/L, in the final effluent, with an HRT of 3 days.
Methane production and volatile fatty acids consumption of both the above anaerobic systems were negligible. The majority of the grease was removed by flocculation as a result of anaerobic bacterial activity. The mechanisms of this process were investigated by a series of batch experiments. It was found that: (1) appropriate gentle mixing between wool scouring effluent (WSE) and anaerobic sludge resulted in the absorption of wool grease from the liquid phase to the sludge phase, (2) further estabilisation of the wool grease emulsion was obtained when the mixed liquor is left undisturbed. The process thus required a short gentle mixing period of approximately 15 minutes to enable complete contact between the sludge and WSE, and a longer settling period of 2 to 4 days to provide appropriate time for the microbes to destabilise wool grease emulsion and transfer it to the sludge phase.
The process of destabilising the wool grease from wool scouring liquor was found to result from the activities of suspended microbes in the anaerobic sludge, which could successfully grow in WSE, rather than the bulk biomass as required in a conventional anaerobic digestion process. General microscopic observation indicated that during the process of bioflocculation a large number of mixed bacterial cells (> 1Q8 cells/nil) were present in the supernatant and only a small number appeared within the flocculated grease. No evidence of bacterial cell aggregation was observed in the process. It was hypothesised that the mechanism involved the partial degradation of detergent.
Detergent analysis revealed that anaerobic microbes' (taken from the sludge of a municipal wastewater treatment plant) had an ability to partially degrade non-ionic surfactants (nonylphenol polyethoxylates - NPEO) by shortening the hydrophilic ethoxylate chain, resulting in the reduction of surfactant properties. This is likely to be one factor causing coagulation and subsequent flocculation of wool grease in the liquor. Other factors such as production of biopolymers and enzymes by microbes may also play a role, and should be further investigated as they beyond the scope of this thesis.
Ten different bacteria strains were isolated from the supernatant of successfully flocculated WSE samples. Six strains were found to grow in raw WSE as a pure culture. Only three strains caused some flocculation of wool grease, although the reduction of grease from the supernatant was not as effective (20-30%) as that using the mixed culture (60-80%). However, the results were not reproducible when different WSE samples were used, thus no definite conclusions could be obtained from this experiment.
The efficiency of anaerobic bioflocculation was found to vary greatly (30% to 80% grease removal) depending on the source of wool scouring effluent The concentration of bacterial substrate, grease and free detergent (rather than total detergent) were all found to effect the efficiency of the process. At a constant loading rate, the efficiency of the process was found to increase with increased grease concentration in WSE. A rationalisation of the scouring process to minimise detergent use and produce higher concentration grease and suint WSE is a likely benefit of bioflocculation process. These findings lead to the recommendation of a proposed treatment scheme.
The main conclusion drawn from this study is that the anaerobic biological removal of wool grease in WSE is due to the destabilisation of the wool grease emulsion resulting in grease flocculation. Since the process does not require further additives, such as chemical flocculant or oxygen, the removal of the bulk of the grease by simple anaerobic bioflocculation appears to be a useful part of an economic treatment system.
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Brown, Robert W. "Development of a Novel Grease Resistant Functional Coatings for Paper-based Packaging and Assessment of Application by Flexographic Press." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4554/.
Full textAbstract:
Recent commercial developments have created a need for alternative materials and methods for imparting oil/grease resistance to paper and/or paperboard used in packaging. The performance of a novel grease resistant functional coating comprised of polyvinyl alcohol (PVA), sodium tetraborate pentahydrate (borate) and acetonedicarboxylic acid (ACDA) and the application of said coating by means of flexographic press is presented herein. Application criteria is developed, testing procedures described, and performance assessment of the developed coating materials are made. SEM images along with contact angle data suggest that coating performance is probably attributable to decreased mean pore size in conjunction with a slightly increased surface contact angle facilitated by crosslinking of PVA molecules by both borate ions and ACDA.
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Newyear, Karl D. "A comparison of theory with laboratory and field observations of wave propagation in grease ice /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/11057.
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Manne, Tiina. "Upper Paleolithic foraging decisions and early economic intensification at Vale Boi, southwestern Portugal." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/204309.
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The Upper Paleolithic site of Vale Boi in coastal, southwestern Portugal currently represents the earliest known case of grease-rendering in Eurasia, with initial occupation occurring during the early Gravettian at ~ 27,000 BP. Long-term exploitation of marine resources is indicated by marine shellfish remains, mainly in the form of limpets (
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Chen, Qi. "Benchmarking of temperature and friction in axial ball bearings lubricated by a novel polymer thickened grease." Thesis, KTH, Maskinkonstruktion (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183007.
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This project concerns the benchmarking of a novel polymer thickened grease with a lithium thickened one. The new grease has shown low temperature property in the previous bearing tests on SKF-R2F. A DAQ interface was implemented using lab View for a modified four-ball machine. The result shows the temperature and friction torque profiles of the greases at different speeds. The raw data is attached with a suggested improvement for friction measurement.Det här projektet avser att jämföra ett nytt polymerbaserat fett med ett lithiumbaserat fett. Det nya fettet har påvisat låga temperaturegenskaper i det tidigare testet med ett lager av typen SKF-R2F. Ett DAQ-gränssnitt implementerades med Lab View för en modifierad fyr-kulig maskin. Resultaten visar temperaturer och friktionsmoment av fetterna vid olika hastigheter. Förslag på förbättring av friktionsmomentet är presenterat tillsammans med rådata.
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Kuňák, Jiří. "Studium chování plastického maziva v hladovějícím elastohydrodynamicky mazaném kontaktu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231062.
Full textAbstract:
This diploma thesis is an experimental study of grease lubrication in a starved elastohydrodynamic lubricated (EHL) contact. Lubricating film thickness is measured with tribological experimental device ball-on-disc using optical interferometry and high speed camera. The experiment is aimed at a comparison of results acquired by ball-on-disc device and full scale axial bearing. In addition, this paper also investigates the influence of number of the rolling elements (overrolling time) on the resulting film thickness.
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Gonçalves, David Emanuel Pimentel. "Polymer greases: film Thickness, Friction and Thermal Degradation." Doctoral thesis, 2016. https://repositorio-aberto.up.pt/handle/10216/85904.
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Gonçalves, David Emanuel Pimentel. "Polymer greases: film Thickness, Friction and Thermal Degradation." Tese, 2016. https://repositorio-aberto.up.pt/handle/10216/85904.
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