L'amélioration de la performance des turbomachines fonctionnant loin de leur point d'adaptation passe par la maîtrise des phénomènes instationnaires qui se produisent dans ces différents organes. L'étude présentée ici se concentre sur les interactions entre une roue de ventilateur centrifuge et son diffuseur. Elle vise, par des mesures de pression sur les différentes parois du diffuseur, ainsi que par des sondages dans les canaux inter-aubages à analyser finement ces phénomènes instationnaires et notamment les décollements fluctuants apparaissant sur les aubes à sur débit, et à mesurer leur influence sur la performance du diffuseur. Dans un second temps, un dispositif de contrôle passif de ces décollements utilisant des générateurs de vortex est proposé. Plusieurs configurations sont testés et leurs résultats sont comparés / The performance improvement of turbomachinery operating at off-design conditions can be achieved by the understanding of unsteady phenomena which are occuring in its components. The present study is focussing on the interaction between a centrifugal impeller fan and its vaned diffuser. It aims at analysing precisely these unsteady phenomena (and especially the fluctuating separated region identified on the vanes wall) and their consequences on the diffuser performance by three holes probe and unsteady pressure measurements. In a second step, devices for a passive control of the separation are introduced. Several configurations are tested and their results are compared

Shallow foundations can provide the most economical solution for supporting small-scale structures. The design approach is quite simple considering the ultimate bearing capacity and working-load settlement. Research has shown that settlement calculations, determined using a linear-elastic approach, usually govern the design but this approach is inappropriate because soil is highly non-linear, even at small strains. The result is that signifi cant discrepancies are observed between predicted and actual settlements. This uncertainty has seen the development of settlement-based approaches such as Mobilisable Strength Design (MSD). MSD uses an assumed undrained mechanism and accounts for soil non-linearity by scaling a triaxial stress-strain curve to make direct predictions of footing load-settlement behaviour. Centrifuge experiments were conducted to investigate the mechanisms governing the settlement of shallow circular foundations on clay and saturated sand models. Clay model tests were performed on soft or rm kaolin beds, depending on its pre-consolidation. Sand model tests were performed on relatively loose Hostun sand saturated with methyl-cellulose to slow consolidation. One-dimensional actuators were developed to apply footing loads through dead-weight or pneumatic loading. A Perspex window in the centrifuge package allowed digital images to be captured of a central cross-section, during and after footing loading. These were used to deduce soil displacements by Particle Image Velocimetry which were consistent with footing settlements measured directly. Deformation mechanisms are presented for undrained penetration, consolidation due to transient flow, as measured by pore pressure transducers, and creep. A technique was developed for discriminating consolidation settlements from the varying rates of short and long-term creep of clay models. Using MSD, a method for predicting the undrained penetration of a spread foundation on clay was proposed, using database results alone, which then provided estimates of creep and consolidation settlements that follow. The importance of the undrained penetration necessitated further investigation by using the observed undrained mechanism as the basis of an ellipsoidal cavity expansion model. An upper-bound energy approach was used to determine the load-settlement behaviour of circular shallow foundations on linear-elastic and non-linear clays, with yield defined using the von Mises' yield criterion. Linear-elastic soil results were consistent with those obtained from nite element analyses. The non-linear model, as described by a power-law, showed good agreement with both centrifuge experiment results and some real case histories. The single design curve developed through this model for normalised footing pressure and settlement could be used by practising engineers based on existing soil correlations or site investigations.

Fried foods are delicious and enjoyed by almost everyone. However, they are not the healthiest foods to eat because of the amount of oil they contain. This thesis, sponsored by Moaero Company founder, Mr. Harrish Bhutani, intends to determine whether a simply designed centrifuge system can remove a reasonable amount of oil from fried foods after it has been deep fried without adversely affecting the texture of the fried food. Due to a large variety in the texture as well as the type of fried foods, and in order to keep the scope of this thesis more focused and feasible, the focus of this investigation will be French fries. Three variables are tested: the type of fry, the angular velocity of the centrifuge, and the time spent in the centrifuge. Multiple designs for the centrifuge system were made on SolidWorks. Engineer Equation Solver (EES) was used to aid steady state and transient heat transfer calculations. Minitab was used for statistical analysis. The impact of various parameters on the change in mass of the French fries, as a measure for evaluating the oil content, were studied. The results indicate whether a centrifuge will remove a reasonable amount of oil while also considering the integrity of the fries. The study concludes that centrifugation is be a cost-effective method for removing oil from fried foods.

This document deals with devices which are used for the automatic Gram staining. The document starts by a research with the aim to discover existing devices and to compare them to the concept of the device developed by company Biovendor. There is theoretically and then practically dealed with the methods of the rotor imbalance detection and measurement of water-level. The Practical part of this document describes the development of the control unit with the microcontroller ARM Cortex-M3 which will be used for the prototype development of Biovendor’s device. The Last part describes measurement of imbalance of three different rotors with the aid of the control unit.

The dissertation deals with clogging of reservoirs and ponds by redundant sediments which penetrate water system by erosion. It describes methods of extracting pond sediments. It contains measurement of dewatering of sediments on hydrocyclone and design of laboratory hydrocyclone and filter unit. In the conclusion there is design of technology of dewatering sediments which were extracted by wet method by drainage excavator. Numerical simulation of flowing in hydrocyclones is simulated in the CFX programme and dewatering technology is simulated in the CHEMCAD programme.

Continued population growth is placing strain on the waste disposal facilities available in South Africa. However, limited air space suitable for landfilling drives the need for alternative solutions such as piggyback landfills to expand the waste disposal capacity. This method entails building a new, fully lined, landfill on top of existing waste. However, the old underlying waste is prone settlement that can result in the cracking of new landfill clay liner. Geogrid reinforcement have been successfully used in clay liners to mitigate cracking induced by waste settlement. This research focused on investigating of the optimal reinforcement strategy (ORS) of such a liner subject to settlement. The ORS entails the optimal position for geogrid reinforcement in a liner, and the stiffness to be used at that position, given a total reinforcement cost. Firstly, the fracture behaviour of unreinforced clay liners was investigated by means of four point bending tests on clay beams. It was found that the fracture of this clay occurred in three stages: linear behaviour, followed by non-linear behaviour when micro-cracks forms and finally macro-cracks that opened once the peak load was reached. Thereafter, the behaviour of geogrid-reinforced clay liners, subjected to differential settlement, was investigated with finite element analyses in ABAQUS. A number of key factors were varied and the resulting change in behaviour of the liners was observed. These were: the overburden stress applied, clay liner thickness, magnitude of central settlement and the width and shape of the settlement trough developing in the underlying waste body. Based on the numerical results, a series of plane-strain centrifuge tests of reinforced clay liners subject to differential settlement were designed. An unreinforced liner, a liner reinforced at the bottom quarter, a liner reinforced at the top quarter and a liner reinforced at both the bottom and top quarters were tested. Laser scanner scans of the surface and strains calculated from digital image velocimetry results were used to compare the behaviour of the liners. Based on these results it is recommended that for optimal performance the available reinforcement should be divided between the top and bottom quarters of the liner to mitigate the effect of settlement. / Volgehoude bevolkingsgroei in Suid-Afrika plaas bestaande rommelstortingsfasiliteite onder druk. ’n Tekort aan grond geskik vir die bou van stortingsterreine moedig die soektog na alternatiewe oplossings soos abba-stortingsterreine aan. Hierdie metode behels ’n splinternuwe stortingsterrein wat bo-op bestaande rommel gebou word. Versakking van die bestaande rommel kan egter veroorsaak dat krake vorm in die nuwe stortingsterrein se kleivoering wat daarop lê. Vorige navorsing het die vorming van krake in die kleivoerings al welgeslaagd verhoed deur van georoosters as versterking gebruik te maak. Die huidige studie het op daardie navorsing gebou deur die optimale versterkings strategie (OVS) te bepaal vir so ’n kleivoering wat vervorm onder versakking van die onderliggende rommel. Die OVS definieer beide die optimale versterkings posisie in ’n kleivoering, en die styfheid van die georooster wat in daardie posisie geplaas moet word, gegewe ’n sekere totale versterkingskoste. Eerstens was daar ondersoek ingestel na die kraakgedrag van onversterkte kleivoerings. Vierpuntbuigtoetse van kleibalkies was hiervoor gebruik. Die krake het oor drie fases gevorm: eerstens was daar lineêre gedrag tot en met mikro-krake gevorm het. Dit is gevolg deur nie-lineêre gedrag wat gelei het tot makro-krake. Sodra die makro-krake gevorm het, is die maksimum las bereik wat die klei kon ondersteun. Na afloop van die balkbuigtoetse was eindige element analises in ABAQUS uitgevoer om die gedrag van versterkte kleivoerings wat bo-op versakkende afval lê te ondersoek. Die spanning toegepas op die oppervlak van die kleivoerings, die dikte van die kleivoerings en die versakkingstrogwydte, -vorm en -diepte was gevarieer om die effek daarvan op die gedrag van die kleivoerings te ondersoek. Na aanleiding van die resultate van die numeriese analise is ’n reeks sentrifuge toetse van kleivoerings wat aan versakking onderwerp word uitgevoer. ’n Onversterkte kleivoering, kleivoerings versterk in die boonste en onderste kwarte, en een versterk in beide die boonste en onderste kwart was getoets. Die gedrag van die verskillende kleivoerings was vergelyk deur die oppervlaktekrake op te meet met ’n laserskandeerder. Verder is die vervorming van die kleivoerings bepaal vanaf die verplasing van die grondpartikels tussen opeenvolgende digitale foto’s. Na aanleiding van hierdie resultate word dit aanbeveel dat die beskikbare georooster versterking opgedeel moet word tussen die boonste en onderste kwart van die kleivoerings ten einde optimale gedrag te verseker indien versakking sou plaasvind. / Dissertation (MEng)--University of Pretoria, 2017. / Deutscher Akademischer Austausch Dienst (DAAD) / Geosynthetics Interest Group of South Africa (GIGSA) / National Research Foundation of South Africa (NRF) / Civil Engineering / MEng / Unrestricted

Pile foundations are extensively used to support various structures that are constructed in soft/loose soils, where shallow foundations would be considered ineffective due to low bearing capacities and large settlements. The design of these structures to accommodate lateral applied loads in particular, usually imposed by winds, water and earth pressures, has gained popularity over the past few decades. The behaviour of horizontally loaded piled foundations is a complex soil-structure interaction problem and is usually concerned with the relative stiffness between the pile and the surrounding soil, where the relative stiffness is a function of both the stiffness and properties of the pile and the stiffness of the soil. Many design assumptions and methods used for pile foundations are based on the principles observed from metal piles. This raises the question of the validity and accuracy of assumptions and methods for the use of analysing and designing reinforced concrete piles, that exhibits highly non-linear material behaviour and changing pile properties after cracking. Due to the elastic behaviour of metal sections, these methods typically only focus on the soil component of the soil-structure interaction problem, only allowing changes and non-linear behaviour of the soil surrounding the pile to take place upon load application, mostly disregarding the behaviour and response of the pile itself. The main purpose and objective of the study was to determine whether aluminium sections in a centrifuge could be used to realistically and sufficiently accurately model the monotonic and cyclic response of reinforced concrete piles subjected to lateral loading. This was observed though a number of tests conducted in a geotechnical centrifuge on scaled aluminium and reinforced concrete piles, subjected to both monotonic and cyclic loading. After conducting the tests on both the scaled aluminium and reinforced concrete piles in the centrifuge it was concluded that aluminium sections cannot be used to accurately model and predict the lateral behaviour of reinforced concrete piles. Both the scaled aluminium and reinforced concrete piles proved to model the concept of laterally loaded piles quite well regarding bending at low loads. However, even at low lateral loads, the observed response of the scaled reinforced concrete was significantly different than that observed from the scaled aluminium pile. Furthermore, as the magnitude of the applied load and bending increased, the scaled reinforced concrete pile cracked, resulting in non-linear behaviour of the section under loading, which was not the case for the scaled aluminium pile that remained uncracked. This contributed to the difference in behaviour between the piles studied, therefore, the true material behaviour and failure mechanisms involved with reinforced concrete piles were not replicated by using a scaled aluminium pile section. The non-linear behaviour of the scaled reinforced concrete pile after cracking affected both the behaviour of the pile, as well as the response of the soil surrounding the pile, in contrast with the behaviour observed from the scaled aluminium pile. / Dissertation (MEng)--University of Pretoria, 2020. / The Concrete Institute / Concrete Society of Southern Africa / WindAfrica project / Civil Engineering / MEng (Structural Engineering) / Unrestricted

High speed separators from Alfa Laval are widely in use for processing flammable and non-flammable liquids. The following work is focusing on the case of non-flammable liquid as the process liquid in case the working area around the equipment may contain quantities of explosive gases. As stated by Alfa Laval documentation, the major risk is leaking of the explosive atmosphere into the separator from the surrounding environment which may result in producing zone 1 or zone 2 of hazardous area classification. Zone 1: Area in which an explosive gas-air mixture is likely to occur for short periods in normal operation.1 Zone 2: Area in which an explosive gas-air mixture is not likely to occur, and if it occurs it will only exist for a very short time due to an abnormal condition.1 According to Alfa Laval design package, there is a need of continuous inert gas injection into the separator during the process in order to reduce the oxygen concentration and keep it in the safe level (inert gas purging) and this policy is aimed to meet the requirements of ATEX-directive 94/9/EC/2003. The objective of the current thesis is a wish to have a better understanding of the potential risks, evaluating them and try to find ways to ease the process. The outcome can be useful to make a basic instruction for further tests and simplifications as well. The separator GTN 50 is selected and hydrogen (1% concentration) is used to simulate the explosive atmosphere. The result of the tests indicates that the cooling down stage after normal operation is the only period in which hydrogen will leak into the separator, frame top part and it should be cleaned up before the next start up. A number of recommendations -Ventilation to the fresh air, Water discharges, Pressurized air injectionare also being tested and discussed. Ventilation to the fresh air and injection of pressurized air seem to be applicable A Standard Testing Flow chart is suggested and calculation on real case is considered. A number of additional ideas are also included in the last section.

Le développement de nouvelles motorisations plus économes en carburant, entraine une augmentation du niveau de vibration. Afin de répondre à cela, Valeo développe un nouveau système : le pendule centrifuge. C’est dans cette phase de développement que s’inscrit ce travail de thèse. L’objectif est de réaliser un outil de pré-dimensionnement permettant de modéliser l’endommagement des guidages d’un pendule centrifuge. Une première étude expérimentale présente la faisabilité du suivi du système mécanique par l’utilisation de l’imagerie dynamique. Des essais de caractérisation matériaux des différents constituants du système viennent ensuite compléter l’étude. Ce travail expérimental réalisé à l’aide d’un tribomètre bi-disque permet d’obtenir les lois de frottements en fonction du taux de glissement ainsi que leur sensibilité à l’état de surface, au traitement thermique et au chargement. Un modèle théorique de détermination des valeurs du glissement est ensuite proposé, permettant de prendre en compte les différentes géométries de pendules. Enfin, les perspectives d’industrialisation sont envisagées en proposant une étude paramétrique sur le système réel en vue de son dimensionnement ainsi qu’une étude d’endurance pour modéliser l’usure du système. / The development of more fuel efficient engines results in an increase in the vibration levels. To solve this, Valeo is developing a new system: the centrifugal pendulum. This PhD research thesis registered as a contribution to the system development phase. The objective is to realize a predimensioning tool in order to model the wear of a centrifugal pendulum. A first experimental study shows the feasibility of monitoring the mechanical system through the use of dynamic imaging. Materials characterization tests of the various system components complete the study. The experimental work carried out using a twin-disc tribometer provides the friction laws versus sliding rate and their sensitivity to surface condition, processing and loading. A theoretical model for determining sliding values is then proposed to take into account the different pendulum geometries. Finally, the perpectives of industrialization are considered with a parametric study on the real system for a sizing purpose and an endurance study to model the wear of the system.

Pyrolysis oil is known to be unstable due to polycondensation reactions that negatively affect properties, such as increased viscosity and water content, lower heating values, and phase separation. Filtration of particulates and solid content out of the pyrolysis oil has been proven to increase stability, thus a filtration system was designed for pilot scale testing for the Mississippi State University Sustainable Energy Research Center (SERC). A literature review was conducted to determine potentially effective methods and eliminate methods likely to not improve the pyrolysis oil properties and stability. An in-line centrifuge system was identified as a useful and cost effective way to remove solids from the pyrolysis oil with an added benefit of potentially removing water content through a three-phase separation configuration. Lab-scale testing of centrifugation on pyrolysis oil indicated both two phase (solid + oil phases) and three phase (solid + aqueous phase + oil phases) separations could be obtained depending on feedstock and pyrolysis oil characteristics, and that centrifugation was a viable option for the removal of solid content. KiOR, Inc. pine clear wood derived pyrolysis oil (formerly known as ReCrude™) was characterized to determine physicochemical properties in comparison to literature results. Aging tests were also performed to investigate stability. In comparison with literature data, the properties for the KiOR product indicated significantly lower water content, particulate matter loading, and viscosity coupled with higher heating and pH values, indicating a product much closer in composition to fossil fuel oils than other pyrolysis oils. The KiOR ReCrudeM™ oil also demonstrated a much higher degree of stability versus other pyrolysis oils; however, there are still some stability issues with the aged samples resulting in slightly higher water content and viscosity values and lower heating and pH values. It is recommended that stability testing (aging) be performed on aliquots separated using a method such as rotary evaporation to more accurately determine what mechanisms are resulting in the properties changes observed over time in response to elevated temperature and/or pressure.