The high frequency reciprocating rig (HFRR) is typically used to determine the lubricity of diesel fuels and has been accepted as the universal test apparatus in most countries of the world. A study was undertaken to analyse results obtained with the HFRR instrument by identifying crucial factors contributing to friction and wear mechanisms during a lubricity test under given conditions that may lead to a better understanding of test results obtained. The transient temperature distribution on a semiinfinite disk due to a circular continuous oscillatory heat source was also modelled. The model was used to calculate the contact temperature of a contact similar to what can be expected in the HFRR apparatus. For lubricated tests a mixture of n-hexadecane (cetane) as base fluid and palmitic acid as lubricity additive was used. Experimental results, including results obtained by running unlubricated (dry) tests and results obtained from literature were all considered to formulate the hypothesis that a fully functional additive film will not survive the full duration of the lubricity test, which is 75 minutes (ISO 12156-1, 2003). Friction values obtained in the experiments conducted were much higher than what is expected for boundary films formed by long chain carboxylic acids. Comparable friction values were obtained in the first few seconds of the tests, but the friction values increased indicating the destruction of the boundary film. Metal oxide lubrication dominates for the remainder of the test. Information of the exact mechanism prevailing in the crucial first few seconds of the test should be obtained by increasing the data acquisition rate of the apparatus. It is believed that junction growth through adhesion is the dominant factor in the initial stages of the test. GCxGC/TOF-MS showed the formation of hexane and heptane, which is a strong indication of the catalytic decomposition of the C16-hydrocarbons in the sample. / Dissertation (MEng)--University of Pretoria, 2010. / Chemical Engineering / unrestricted

No description available.

O objetivo deste estudo ex vivo foi avaliar o selamento apical e a resistência de união à dentina radicular da obturação de canais radiculares usando a técnica do cone único dos sistemas WaveOne e Reciproc com diferentes cimentos, em comparação à técnica da condensação lateral. Foram selecionados caninos superiores humanos cujas coroas foram removidas permanecendo as raízes com 15 mm. A amostra foi distribuída aleatoriamente de acordo com o sistema de instrumentação/ técnica de obturação: Reciproc R40/Cone único R40; WaveOne Large/Cone único Large e ProTaper Universal (até instrumento F4)/Condensação lateral. Posteriormente, 9 subgrupos (n=20) foram estruturados conforme o cimento endodôntico: AH Plus, Epiphany SE e MTA Fillapex. Após preparo biomecânico e obturação dos canais radiculares, os espécimes foram armazenados a 37&deg;C e 100% de umidade por período correspondente a três vezes o tempo de endurecimento dos cimentos. O método de filtração de fluidos foi utilizado para verificação do selamento apical em 10 espécimes de cada subgrupo. Espécimes apenas com cone de guta-percha e sem cimento (n=6) e outros completamente impermeabilizados (n=2) foram os controles positivos e negativos, respectivamente. Dos 10 espécimes remanescentes de cada subgrupo foram obtidas fatias de dentina com 1 mm de espessura (3 por terço radicular: cervical, médio e apical), sendo 6 (2 fatias por terço) utilizadas para o teste de push-out. O tipo de falhas ocorridas após a desunião foi avaliado em microscópio óptico (25X de aumento). Dentre as outras fatias, foram selecionadas 5 de cada terço, em cada subgrupo, para análise por microscopia eletrônica de varredura (MEV) (1000X de aumento). Foram mensurados doze pontos na interface material obturador/dentina e os seguintes escores foram atribuídos para a adaptação da obturação: 0 (seções sem lacunas); 1 (seções com pequenas falhas, <1 &mu;m); 2 (seções com muitas lacunas, entre 1 &mu;m e 10 &mu;m) e 3 (sem adaptação, lacunas >10 &mu;m). Os dados de infiltração apical e resistência de união (RU) foram analisados pelo teste ANOVA duas vias e teste de Tukey (p<0,05). Os testes de Kruskal-Wallis e Student-Newman-Keuls (p<0,05) foram utilizados para análise dos dados referentes à adaptação da obturação. Em relação ao selamento apical, as três técnicas apresentaram diferenças entre si, com melhores resultados para a condensação lateral (p<0,05). A técnica WaveOne propiciou menor índice de filtração de fluido que a Reciproc, sem diferença estatisticamente significante entre os cimentos (p>0,05). As técnicas de cone único apresentaram menores valores de RU que a condensação lateral (p<0,05), enquanto nesta última técnica o cimento AH Plus apresentou os maiores valores de RU, sendo estatisticamente superior ao MTA Fillapex e Epiphany SE (p<0,05). Houve predominância de falhas adesivas à dentina no terço apical e mistas nos terços médio e cervical. A análise por MEV mostrou melhor adaptação na interface dentina/material obturador para o cimento AH Plus que para os cimentos MTA Fillapex e Epiphany SE (p<0,05). Concluiu-se que as técnicas de cone único apresentaram maior infiltração apical e menor resistência de união que a condensação lateral. Melhor adaptação marginal foi obtida com o cimento AH Plus, independentemente da técnica de obturação utilizada. / The aim of this ex vivo study was to evaluate the apical sealing and bond strength (BS) of root canal filling using single-cone from WaveOne and Reciproc systems associated to different sealers compared with the lateral condensation technique. The crowns of maxillary human canines were sectioned in order to standardize the root length to 15 mm. The sample was randomly allocated according to instrumentation system /obturation technique: R40 Reciproc file/ R40 single cone; WaveOne Large/Large single cone; ProTaper Universal (up to F4 file)/ Lateral condensation. Subsequently, 9 subgroups (n=20) were defined according to root canal sealer: AH Plus, Epiphany SE and MTA Fillapex. After the preparation and filling procedures, the specimens were stored at 37°C and 100% humidity for a period three times longer than the setting time of the sealers. The fluid filtration method was used to investigate the apical sealing in 10 specimens of each subgroup. Specimens with only cone and without sealer (n=6) and others completely sealed (n=2) were used as positive and negative controls, respectively. Slices with 1 mm thickness (3 per root third: cervical, middle and apical) were obtained from the remaining specimens of each subgroup, while 6 slices (2 per third) were submitted to push-out test. Failures modes were evaluated in optical microscope (magnification 25X). Among the other slices for each experimental condition, five were selected from each third for analysis by scanning electron microscopy (SEM) (magnification 1000X). Twelve points were measured in filling material/dentin interface, and the following scores were used in order to evaluate the root filling adaptation: 0 (sections without gaps); 1 (sections with small gaps, <1&mu;m); 2 (sections with many gaps, between 1 &mu;m and 10 &mu;m) and 3 (without adaptation, gaps>10 &mu;m). The data on apical infiltration and BS were analyzed by two way ANOVA test and Tukey&prime;s test (p<0.05). The Kruskal-Wallis test followed by Student-Newman-Keuls test (p<0.05) were used for data analysis concerning the adaptation of the root filling. Regarding the apical sealing, there was statistical difference between the obturation techniques, whereas the lateral condensation showed the best results (p<0.05). The WaveOne technique provided lower rate of fluid filtration than Reciproc, and no statistically significant differences were observed between the sealers (p>0.05). The single-cone techniques showed lower values of BS than lateral condensation, in which AH Plus showed the highest BS values, with statistical difference from MTA Fillapex and Epiphany SE (p<0.05). There was predominance of adhesive failures in the apical third and mixed failures in the middle and cervical thirds. The SEM analysis revealed better adaptation in the filling material/dentin interface for AH Plus than MTA Fillapex and Epiphany SE. It was concluded that the single-cone techniques resulted in highest apical infiltration and lowest BS than lateral condensation one. Better marginal adaptation was obtained with AH Plus, regardless of obturation technique used.

Oil feed grooves are implemented in reciprocating compressor piston applications to assure a constant supply of lubricating oil on bearing surfaces and decrease friction loss. In a hermetically sealed compressor, due to small clearances encountered, oil supply becomes critical in order not to operate in boundary lubrication regime. Due to the small size of the piston and small piston &ndash / cylinder clearance, a partial lubrication regime is present. In the current study, a model that solves Reynolds&rsquo / equation for piston-cylinder lubrication and the average Reynolds&rsquo / equation that considers the effect of roughness on partially lubricated bearing for a compressor piston with oil feed grooves is developed. A parametric study is carried out to investigate the effects of piston design parameters and then arrive at an improved piston performance by using alternative designs for oil feed groove and the other design parameters.

O objetivo deste estudo ex vivo foi avaliar o selamento apical e a resistência de união à dentina radicular da obturação de canais radiculares usando a técnica do cone único dos sistemas WaveOne e Reciproc com diferentes cimentos, em comparação à técnica da condensação lateral. Foram selecionados caninos superiores humanos cujas coroas foram removidas permanecendo as raízes com 15 mm. A amostra foi distribuída aleatoriamente de acordo com o sistema de instrumentação/ técnica de obturação: Reciproc R40/Cone único R40; WaveOne Large/Cone único Large e ProTaper Universal (até instrumento F4)/Condensação lateral. Posteriormente, 9 subgrupos (n=20) foram estruturados conforme o cimento endodôntico: AH Plus, Epiphany SE e MTA Fillapex. Após preparo biomecânico e obturação dos canais radiculares, os espécimes foram armazenados a 37&deg;C e 100% de umidade por período correspondente a três vezes o tempo de endurecimento dos cimentos. O método de filtração de fluidos foi utilizado para verificação do selamento apical em 10 espécimes de cada subgrupo. Espécimes apenas com cone de guta-percha e sem cimento (n=6) e outros completamente impermeabilizados (n=2) foram os controles positivos e negativos, respectivamente. Dos 10 espécimes remanescentes de cada subgrupo foram obtidas fatias de dentina com 1 mm de espessura (3 por terço radicular: cervical, médio e apical), sendo 6 (2 fatias por terço) utilizadas para o teste de push-out. O tipo de falhas ocorridas após a desunião foi avaliado em microscópio óptico (25X de aumento). Dentre as outras fatias, foram selecionadas 5 de cada terço, em cada subgrupo, para análise por microscopia eletrônica de varredura (MEV) (1000X de aumento). Foram mensurados doze pontos na interface material obturador/dentina e os seguintes escores foram atribuídos para a adaptação da obturação: 0 (seções sem lacunas); 1 (seções com pequenas falhas, <1 &mu;m); 2 (seções com muitas lacunas, entre 1 &mu;m e 10 &mu;m) e 3 (sem adaptação, lacunas >10 &mu;m). Os dados de infiltração apical e resistência de união (RU) foram analisados pelo teste ANOVA duas vias e teste de Tukey (p<0,05). Os testes de Kruskal-Wallis e Student-Newman-Keuls (p<0,05) foram utilizados para análise dos dados referentes à adaptação da obturação. Em relação ao selamento apical, as três técnicas apresentaram diferenças entre si, com melhores resultados para a condensação lateral (p<0,05). A técnica WaveOne propiciou menor índice de filtração de fluido que a Reciproc, sem diferença estatisticamente significante entre os cimentos (p>0,05). As técnicas de cone único apresentaram menores valores de RU que a condensação lateral (p<0,05), enquanto nesta última técnica o cimento AH Plus apresentou os maiores valores de RU, sendo estatisticamente superior ao MTA Fillapex e Epiphany SE (p<0,05). Houve predominância de falhas adesivas à dentina no terço apical e mistas nos terços médio e cervical. A análise por MEV mostrou melhor adaptação na interface dentina/material obturador para o cimento AH Plus que para os cimentos MTA Fillapex e Epiphany SE (p<0,05). Concluiu-se que as técnicas de cone único apresentaram maior infiltração apical e menor resistência de união que a condensação lateral. Melhor adaptação marginal foi obtida com o cimento AH Plus, independentemente da técnica de obturação utilizada. / The aim of this ex vivo study was to evaluate the apical sealing and bond strength (BS) of root canal filling using single-cone from WaveOne and Reciproc systems associated to different sealers compared with the lateral condensation technique. The crowns of maxillary human canines were sectioned in order to standardize the root length to 15 mm. The sample was randomly allocated according to instrumentation system /obturation technique: R40 Reciproc file/ R40 single cone; WaveOne Large/Large single cone; ProTaper Universal (up to F4 file)/ Lateral condensation. Subsequently, 9 subgroups (n=20) were defined according to root canal sealer: AH Plus, Epiphany SE and MTA Fillapex. After the preparation and filling procedures, the specimens were stored at 37°C and 100% humidity for a period three times longer than the setting time of the sealers. The fluid filtration method was used to investigate the apical sealing in 10 specimens of each subgroup. Specimens with only cone and without sealer (n=6) and others completely sealed (n=2) were used as positive and negative controls, respectively. Slices with 1 mm thickness (3 per root third: cervical, middle and apical) were obtained from the remaining specimens of each subgroup, while 6 slices (2 per third) were submitted to push-out test. Failures modes were evaluated in optical microscope (magnification 25X). Among the other slices for each experimental condition, five were selected from each third for analysis by scanning electron microscopy (SEM) (magnification 1000X). Twelve points were measured in filling material/dentin interface, and the following scores were used in order to evaluate the root filling adaptation: 0 (sections without gaps); 1 (sections with small gaps, <1&mu;m); 2 (sections with many gaps, between 1 &mu;m and 10 &mu;m) and 3 (without adaptation, gaps>10 &mu;m). The data on apical infiltration and BS were analyzed by two way ANOVA test and Tukey&prime;s test (p<0.05). The Kruskal-Wallis test followed by Student-Newman-Keuls test (p<0.05) were used for data analysis concerning the adaptation of the root filling. Regarding the apical sealing, there was statistical difference between the obturation techniques, whereas the lateral condensation showed the best results (p<0.05). The WaveOne technique provided lower rate of fluid filtration than Reciproc, and no statistically significant differences were observed between the sealers (p>0.05). The single-cone techniques showed lower values of BS than lateral condensation, in which AH Plus showed the highest BS values, with statistical difference from MTA Fillapex and Epiphany SE (p<0.05). There was predominance of adhesive failures in the apical third and mixed failures in the middle and cervical thirds. The SEM analysis revealed better adaptation in the filling material/dentin interface for AH Plus than MTA Fillapex and Epiphany SE. It was concluded that the single-cone techniques resulted in highest apical infiltration and lowest BS than lateral condensation one. Better marginal adaptation was obtained with AH Plus, regardless of obturation technique used.

Production of steel powder is done by atomization of a molten steel stream. Atomization is done by feeding high pressure nitrogen gas through nozzles, creating jets of gas which scatter the molten steel stream into powder. The steel powder falls through the atomization tower whilst it cools and solidifies. Finally, the steel powder is transported for further processing. The compressor is used for two main purposes, to compress the nitrogen gas to desired pressure and enable recycling of nitrogen gas. As nitrogen is inert and do not react with its surrounding, the gas can be recycled. Filtering nitrogen gas from the atomization process, one is able to reuse the gas, which is led to the inlet side of a compressor. A closed loop is thus created which is economically important. In 2021 a major compressor failure occurred, which caused large production losses. iba systems is a commercially available product extensively utilized in the Swedish steel industry for data acquisition, production monitoring and generating key performance indicators. Therefore, this thesis investigates what modules and functionality iba systems have to offer. Process and machine signals are studied to assess both their utility in predicting machine failure and relevant iba modules for the predictive maintenance purposes, based on a literature review. This thesis shows the possibility to implement an anomaly detection to detect abnormal behavior, related to historic compressor failure. Estimating when maintenance is needed is possible but requires implementation of new sensors to obtain useful information, mainly vibration data from machinery. Anomaly detection is implemented using ibaAnalyzer. Additional analysis is done in Matlab.

No description available.

A performance comparison of heat pumps using a scroll (Sanden) and a reciprocating (Bitzer) compressor was conducted experimentally. The refrigerant used was R600a (isobutane). The heat pump components were evaluated performance-wise through: volumetric and isentropic efficiency of the compressors; the UA-value of the condensers and evaporators; sensible enthalpy differences between the liquid and the suction line in the internal heat exchanger; and overall heat pump system comparison as the coefficient of performance. The Bitzer heat pump had existing measuring devices and equipment installed, and it was already filled with refrigerant. The Sanden heat pump required installation of equipment and measuring devices and a refrigerant refill. The refrigerant charge was decided according to the criteria of the lowest compressor speed, which had an effect of overcharge for higher speeds. The measurements included the temperature of water and refrigerant, pressure of the refrigerant, water volume flow, and compressor power. The heat pumps performances were then evaluated based on these parameters. The Sanden compressor showed higher volumetric efficiency than the Bitzer compressor, for the two lower (out of three) speeds of the compressor. The isentropic efficiency of the Bitzer compressor proved to be higher for all pressure ratios out of the three speeds respectively. The condenser in the Bitzer heat pump showed proper UA-values based on the temperature differences between refrigerant and heat sink. The UA-values of the Sanden heat pump condenser did not increase with compressor speed which then gave a larger temperature difference between refrigerant and heat sink, for the two higher compressor speeds. The evaporators had a similar issue with the temperature difference between refrigerant and heat source, which also showed on the UA-values. The internal heat exchanger in the Bitzer heat pump had a larger sensible enthalpy difference on the suction side compared to the liquid side, when condenser subcooling was low, indicating that some fraction of refrigerant was being condensed instead. The Sanden heat pump instead had higher condenser subcooling and the sensible enthalpy difference showed to be very low in the internal heat exchanger. Finally, the coefficient of performance showed to be slightly higher in the Bitzer heat pump for almost all evaluated condensation and evaporation temperatures. / En jämförelse av prestandan för två värmepumpar, en med scroll- (Sanden) och en med kolvkompressor (Bitzer) har gjorts. Köldmedlet som användes var R600a (isobutan). Komponenterna och hur deras prestanda blev utvärderad följer här: kompressorernas volymetriska och isentropisk verkningsgrad; kondensorns och förångarens UA-värden; den sensibla entalpiskillnaden mellan gas- och vätskeledning i den interna värmeväxlaren; en övergripande jämförelse av värmepumparna i form av deras värmefaktor. Värmepumpen med Bitzerkompressor utvärderades med befintliga komponenter och mätutrustning, och en redan fylld mängd köldmedium. Värmepumpen med Sandenkompressor installerades med mätutrustning och komponenter, och fylldes med köldmedium. Mängden köldmedium bestämdes utifrån kriterier för det lägsta varvtalet på kompressorn, vilket visade sig ge en för stor mängd köldmedium vid de högre varvtalen. Mätningarna inkluderade temperatur på vatten och köldmedium, köldmediets tryck, vattnets volymflöde samt kompressorns effektbehov. Prestandan för värmepumparna är sedan utvärderad utifrån dessa data. Sandenkompressorn visade en högre volymetrisk verkningsgrad för de två lägre (av tre) hastigheterna utvärderade i experimenten, jämfört med Bitzer. Den isentropiska verkningsgraden var högre i Bitzerkompressorn för samtliga tryckförhållanden för de tre respektive hastigheterna. Kondensorn i Bitzervärmepumpen uppvisade goda UA-värden, baserat på temperaturskillnaderna mellan köldmedium och värmesänka. Kondensorn i Sandenvärmepumpen visade ingen förbättring av UA-värden när kompressorns hastighet ökade, vilket i sin tur gav upphov till stora temperaturskillnader mellan köldmediet och värmesänkan. Förångarna i båda värmepumparna uppvisade liknande problem med höga temperaturskillnader mellan värmekälla och köldmedium, vilket även deras UA-värden visade. Den interna värmeväxlaren i Bitzervärmepumpen visade större skillnad i den sensibla entalpin på sug- jämfört med vätskesidan, när underkylningen i kondensorn var låg, vilket indikerade på att en del av köldmediet istället kondenserade. I Sandenvärmepumpen var kondensorns underkylning högre vilket då uppvisade en liten skillnad i den sensibla entalpin mellan de båda sidorna. Slutligen så visade Bitzervärmepumpen en något högre värmefaktor än Sandenvärmepumpen för nästan alla utvärderade kondenserings- och förångningstemperaturer.

Lithium ion (Li-ion) batteries have been identified as a promising solution to meet the increasing demands for alternative energy in electric vehicles (EVs) and hybrid electric vehicle (HEVs). This work describes experimental and numerical study of thermal management of battery module consisting of cylindrical Li-ion cells, with an emphasis on the use of active control to achieve optimal cooling performance with minimal parasitic power consumption. The major contribution from this work is the first experimental demonstration (based on our review of archival journal and conference literature) and the corresponding analysis of active thermal control of battery modules. The results suggest that the active control strategy, when combined with reciprocating cooling flow, can reduce the parasitic energy consumption and cooling flow amount substantially. Compared with results using passive control with unidirectional cooling flow, the parasitic energy consumption was reduced by about 80%. This contribution was achieved in three steps, which was detailed in this dissertation in chapters 2, 3, and 4, respectively. In the first step, an experimental facility and a corresponding CFD model were developed to capture the thermal behavior of multiple battery cells. Based on the experimental and CFD results, a reduced-order model (ROM) was then developed for active monitoring and control purposes. In the second step, the ROM was parameterized and an observer-based control strategy was developed to control the core temperature of battery cells. Finally, based on the experimental facility and the ROM model, the active control of a battery module was demonstrated. Each of these steps represents an important facet of the thermal management problem, and it is expected that the results and specifics documented in this dissertation lay the groundwork to facilitate further study. / Ph. D.

La grande diversité des applications, dans tous les domaines industriels, des plus simples aux plus complexes, que ce soit pour un usage quotidienne ou pour des applications high-tech, nécessite la conception continue de systèmes d'étanchéité de plus en plus performants. Les vérins pneumatiques sont des éléments fondamentaux de l'automatisation dans des domaines industriels très variés : les dispositifs de levage, la robotique, l'aérospatial, les systèmes respiratoire, etc. Cependant, un dysfonctionnement d'étanchéité conduit à des performances plus faibles et même à des disfonctionnements. Inversement, une meilleure connaissance des phénomènes aux interfaces, permettra l’amélioration du rendement, la prolongation de la durée de vie et de la fiabilité des différentes applications pneumatiques.Ce travail de thèse est focalisé sur l'étude expérimentale et numérique des systèmes d'étanchéité par joints pneumatiques. Un banc d'essais modulable a été conçu et réalisé pour permettre l'investigation expérimentale de différents types de joints pneumatiques, pour une large gamme de conditions de fonctionnement, en termes de vitesse linéaire, pression pneumatique et solutions constructives. Il permet principalement de caractériser le frottement des joints mais aussi la visualisation des phénomènes physiques au niveau de la zone d'étanchéité et de son environnement.En parallèle, un modèle théorique ElastoHydroDynamique, incluant la prise en compte des conditions de lubrification mixte et le comportement rhéologique non-newtonien de lubrifiant (graisse) a été développé. Il est basé sur le couplage d'un logiciel de calcul non-linéaire (permettant la prise en compte du comportement mécanique hyperélastique des joints) et un modèle d'écoulement en film mince. Les comparaisons de mesures expérimentales avec les prédictions numériques ont permis de valider le modèle théorique ainsi que d'améliorer la compréhension des conditions de fonctionnement et d'alimentation de la zone d'étanchéité. / The great diversity of applications in all industrial fields, from the simplest to the most complex, whether for everyday use or for high-tech applications, requires the continuous design of increasingly efficient sealing systems. Pneumatic cylinders are fundamental elements of automation in a wide variety of industrial fields: lifting devices, robotics, aerospace, respiratory systems, etc. However, a sealing failure leads to lower performance and even malfunctions. Conversely, a better knowledge of the phenomena at the interfaces will allow the improvement of efficiency, the extension of the service life and of the reliability of the various pneumatic applications.This thesis work focuses on the experimental and numerical study of pneumatic seal systems. A modular test bench has been designed and built to allow the experimental investigation of different types of pneumatic seals, for a wide range of operating conditions, in terms of linear velocity, pneumatic pressure and constructive solutions. It mainly allows to characterize the friction of the joints but also the visualization of physical phenomena at the level of the sealing zone and its environment.In parallel, an ElastoHydroDynamic theoretical model, including the consideration of mixed lubrication conditions and the non-Newtonian rheological behaviour of lubricant (grease) has been developed. It is based on the coupling of a non-linear comercial software (allowing the modelling of the hyperelastic mechanical behaviour of the joints) and a thin film flow model. Comparisons of experimental measurements with numerical predictions validated the theoretical model and improved the understanding of the operating and supply conditions of the sealing area.