The base metal distribution in, and losses to, Anglo Platinum six-in-line and slag cleaning furnace slags were characterised to coincide with various process changes at Waterval Smelter from 1999 to 2009. The base metals are presumed to be reliable indicators of PGE losses and are easier to detect and measure than these elements are. In addition, base metal and sulphur levels are used to monitor and control many smelter processes, including slag cleaning and converting. Some losses to slag are recoverable but others are not – these have been quantified during this study. Slag composition and smelting temperatures have varied substantially, and optimisation of the slag cleaning furnace – a first for the South African platinum industry – has produced a wide variation in oxidation conditions. Most of the base metal losses in the slag cleaning furnace are mechanically entrained matte particles, the largest of which should be recovered. These have been examined to establish any relationship between composition, size, and depth within the furnace so that recommendations can be made to limit these types of losses. In the six-in-line furnaces, over half of base metal losses to slag are as dissolved phases, which are not recoverable. Levels of dissolved metals have been measured and related to furnace operating conditions and slag composition. The prediction of such base metal losses is not easy, because the slag compositions are so complex. One aspect of the project has been to compare the measured distribution of the base metals with those calculated using the FactSage equilibrium model, to identify problem areas, and to recommend actions which could improve the predictions of this and similar modelling programs for base metal dissolution in slag. New electron microbeam techniques have been developed to quantify base metal distribution in slag, and novel combinations of these techniques with analytical chemistry and Mössbauer Spectroscopy have been pioneered. / Dissertation (MSc)--University of Pretoria, 2009. / Materials Science and Metallurgical Engineering / unrestricted

As a result of the rising electrical energy costs in South Africa, a method was sought to reduce the overall electrical consumption of typical shaft systems. A typical shaft configuration was analysed and the primary energy consumers were identified. The ventilation fans for this system were found to consume a total of 15% of the total energy of the shaft system. It was calculated that more than 50% of this energy is consumed by the shaft itself, more specifically by the pressure losses that occur in the shaft as the ventilation air passes through it. It was recognised that there was therefore an opportunity to achieve an energy savings and therefore a costs savings in the total cost of operating a shaft system by reducing the overall resistance of the equipped downcast shaft. However, before any work could continue in this regard, the results noted above required validation. This was achieved though the comprehensive evaluation of the Impala #14 Shaft system. This system was tested and the pressure losses noted in the calculations were verified. In order to ensure that the theory being used was accurate, the next step was to evaluate a number of shafts both from a theoretical perspective by measuring the real shaft pressure losses against time. This was done and a total of five shafts were instrumented and the actual pressure losses over the shaft plotted against time. These shafts were then subjected to a theoretical evaluation using the theory as described by McPherson in 1987. Finally, in order to ensure a thorough understanding of the behaviour of the ventilation air in shaft systems, the systems were simulated using computational fluid dynamic (CFD) techniques. On the whole there was not a good correlation between the tests and either the theoretical calculations or the CFD simulations. This was attributed to the general imperfections in the shaft and the difficulty in obtaining exact values for the drag coefficients of the buntons. These differences highlight the difficulty in modeling the non-homogenous physical environment and providing a factor that can be used to ensure that the theoretical designs are aligned with the physical reality. This factor is approximately 30%. There were also significant discrepancies between the theoretical analysis and the CFD simulation during the initial comparisons. This discrepancy reduced as the complexity of the CFD models increased, until, when the complete shaft was modeled using the full buntons sets, the pipes and the flanges, the difference between the theoretical evaluation and the CFD simulation was small. The result demonstrates that the theory is insufficient and that the inter-related effect of the buntons and fittings has not been fully appreciated. The current theory however has been developed using drag coefficients and interference factors for the buntons sets which have been taken from measurements of similar configurations. This does account for the relative accuracy of the current theory in that there is little difference between the CFD result and that of the theory. However, as the shaft parameters are changed to reflect new layouts and scenarios, it is unlikely that theory will continue to prove accurate. The final phase of the work presented here was to evaluate the cost-effectiveness of using different bunton shapes and shaft configurations. It is shown that: <ul><li> The increase in the pressure losses and therefore the direct operating costs of the shaft can vary by as much as 80%, depending on the bunton configuration chosen.</li><li> The placement of the piping in the shaft can increase the pressure losses and therefore the direct operating costs of the shaft by as much as 12%, depending on the placement of the piping in the shaft; this effect includes the use of flanges. </li><li> The use of fairings on a large cage can reduce the resistance that the cage offers to the ventilation flow by as much as 30%. This, however, does not translate into a direct saving because as the cage moves through the shaft, the overall effect is transitory. </li> </ul> The savings discussed above can be significant when the items highlighted in this work are applied correctly. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Mining Engineering / unrestricted

Detonations in gases usually propagate with lateral strain rates, in either weakly confined or varying-cross-section or curved or even small-sized geometries. Lateral strain rates have been generally known to significantly impact the detonation dynamics, i.e., decreasing the propagation speeds lower than the theoretical Chapman-Jouguet (CJ) velocities, increasing the propagation limit pressures as well as cell sizes. Since the detonation-based engines require the reliable control of the accurate ignition and stable propagation of a detonation wave, it is desirable to have the predictive capability of the response of detonation dynamics to lateral strain rates, for achieving the practical purposes of detonation applications. Therefore, the present thesis aims to provide such predictability, by quantifying the effect of lateral strain rates on detonation dynamics from both the experimental and numerical modelling perspectives. Experimentally, this study extended the exponential horn technique of Radulescu and Borzou (2018) to a range of characteristic mixtures with varied detonation instability levels, i.e., from the weakly unstable system of 2H₂/O₂/7Ar to the highly unstable one of CH₄/2O₂. Steady detonation waves were obtained at the macro-scale, with the very regular H₂/O₂/Ar detonation cellular structures characterized by reactive transverse waves while the unstable hydrocarbon-oxygen detonation reaction zone structures in the presence of significant unreacted gas pockets. The meaningful D-K curves characterizing the relationships between the detonation mean propagation speeds and lateral strain rates were directly obtained from experiments. Comprehensive comparisons were then made between experiments and predictions from the generalized ZND model with lateral strain rates. Excellent agreement was found for the stable H₂/O₂/Ar detonations due to the much longer thermally insensitive reaction zone lengths compared to the characteristic induction zone lengths, while substantial departures exist for the highly unstable CH₄/2O₂ detonations. The degree of departure was found to correlate well with the detonation instability. As compared to the laminar ZND wave, the more unstable hydrocarbon-oxygen detonations manifested themselves in the significantly enhanced global rates of energy release with the notably suppressed thermal character of ignition. Implications of such a globally enhanced burning mechanism highlight the important role of diffusive processes involved in turbulent burning of the unreacted gas pockets. Finally, empirical global reaction rate laws were developed for effectively capturing the dynamics of unstable detonations. Numerically, this work proposed a novel model for evaluating the effect of boundary layer losses on cellular structures of 2D detonations in narrow channels. The boundary-layer-induced lateral strain rate was evaluated using the negative boundary layer displacement of Mirels' theory. With the theoretical Mirels' constant KM reduced by a factor of 2, the experimentally obtained 2H₂/O₂/7Ar detonations can be very well reproduced by simulations using the resulting quasi-2D formulation. It was further found out that detonation cellular cycle dynamics can be modified by the presence of boundary layer losses, yielding larger velocity fluctuations and more rapid decay rates of the lead shock. The exponential sensitivity of detonation cell sizes to velocity deficits, controlled by the global activation energy, highlights the importance of providing the detonation speed when reporting experimentally measured cell sizes.

This master´s thesis enter on the construction, losses and temperature computations asynchronuos engine. Preliminary is talk about the function cage induction motor, than describet construction and losses in this motor and in conclusion describet temperature computations and principia programme ANSYS Workbench and like the example for asynchronuos engine. In conclusion was make the komparative analysis with laboratory measurement for this engine

This thesis focuses on design of device to generate hot air. This generator is supposed to be used to perform thermal tests for a company. Introduction summarizes general knowledge about ventilators, heat transport in air flow, and pressure losses. Main part of the thesis describes development of the generator. Initial design was followed by selection of suitable solution variants, design of major parts of the generator supported by calculations and overall conception of the generator. Final part summarizes the achievements and economic analysis.

Propagation of a Gaussian beam in a layered periodic structure is studied analytically, numerically, and experimentally. It is demonstrated that for a special set of parameters the acoustic beam propagates without diffraction spreading. This propagation is also accompanied by negative refraction of the direction of phase velocity of the Bloch wave. In the study of two-dimensional viscous phononic crystals with asymmetrical solid inclusions, it was discovered that acoustic transmission is nonreciprocal. The effect of nonreciprocity in a static viscous environment is due to broken PT symmetry of the system as a whole. The difference in transmission is caused by the asymmetrical transmission and dissipation. The asymmetrical transmission is caused solely by broken mirror symmetry and could appear even in a lossless system. Asymmetrical dissipation of sound is a time-irreversible phenomenon that arises only if both energy dissipation and broken parity symmetry are present in the system. The numerical results for both types of phononic crystals were verified experimentally. Proposed devices could be exploited as collimation, rectification, and isolation acoustic devices.

One possible way of solving future energy shortages is by the optimization of our current energy consumption. These optimizations must span all possible fields of consumption. In the mechanical field radial piston hydraulic motors may show some margin of improvement. The radial piston hydraulic motor is driven by a pressure difference in hydraulic oil. These motors are commonly found in heavy industrial equipments such as drills and conveyor belts. The advantage with these motors in comparison with electric motors is the high torque and ability to absorb shock loads that may cause damage to electrical motors. The effectiveness of these motors are determined both by the motor and by the drive system as a whole consisting of hydraulic pump driven by a electric motor, hydraulic hoses, motor and possible external coolers. If the effectiveness of the motor is low the whole drive system will be affected thus amplifying the total losses. The losses in the motor can be both mechanical and derived to the viscosity of the oil. One region in the motor where there are viscous losses are in the housing. The housing is filled with oil, that both aids in the cooling and acts as a lubricant for the motor. Pistons and rollers are some of the components found in the housing. These components rotates around the centre line axis while having a pulsating radial motion following a cam ring. This rotating and pulsating motion will push oil in and out of a volume between two consecutive pistons and rollers. This will create viscous losses and regions with a enhanced risk of cavitation. This study investigates if the flow of oil in the housing can be simulated accurately. The study also examine what are the main problems regarding the flow of oil in the housing and the factors affecting the size of the viscous losses. The study also examines the correlation between viscosity and viscous losses. Finally two different optimizations with the intention of decreasing the viscous losses are compared. The study found that the majority of the viscous losses in the housing can be derived to the flow of hydraulic oil in and out of the volume between two consecutive pistons and rollers. The oil will pass a sharp edge around the cylinder block and a narrow passage under the spacing between the cylinder rows in a two cam ring configured motor. This will create regions with a enhanced velocity and risk of cavitation. The stroke of the motor will greatly affect the effectiveness of the motor especially at a high rotational speed. The viscous losses will be transformed into internal energy, heat, thus increasing the temperature of the oil. A increased temperature will decrease the viscosity and the viscous losses. The viscous losses will vary with 17 % if the viscosity is varied between 20 and 100 cSt. The developed model is not sufficient to determine the viscous losses accurately since the geometry had to be considerably simplified, but can act as a way of comparing different optimizations of the motor. The viscous losses can be decreased with 25 % in the CCe motor at 150 rpm by milling material of the cylinder block between the piston holes. This is an expensive optimization and needs to be justified from a cost-benefit perspective.

För att öka köreffektivitet och säkerhet samt minska bromsarnas slitage är de flesta av Scanias lastbilar och bussar utrustade med en hjälpbroms, så kallad retarder. En retarder arbetar generellt sett enligt någon av följande två principer. Dels en elektromagnetisk variant av retarder som bromsar bilens kardanaxel, drivaxlar eller växellåda genom att utnyttja elektromagnetisk induktion, eller som i Scanias fall där man använder sig av en hydrodynamisk tillsatsbroms som bromsar bilens kardanaxel genom att slunga vätska inom ett skovelsystem. Bromsenergin övergår då till värmeenergi som i sin tur kyls bort av bilens ordinarie vattenkylsystem. Bromsmomentet styrs via trycket som råder mellan skovelbladen. Som mest överträffar retardern den effekt som bilens motor kan leverera. Då retardern inte används är skovelsystemet trycklöst. Men även då skapas det dock ett litet släpmoment i retardern eftersom den fortfarande roterar med växellådan. Detta släpförlustmoment är en bråkdel jämfört med det moment som skapas vid bromsning men ur bränslebesparingssynpunkt är det ändå viktigt att det hålls på minimal nivå. Detta examensarbete syftar till att utreda hur dessa släpförluster kan minimeras genom att via konceptstudier ta fram den bäst lämpade släpförlustreduceringsmetoden för Scanias retarder. En studie på konkurrenter och andra applikationer där inspiration skulle kunna inhämtas genomfördes och ett antal koncept togs fram. Därefter genomfördes en provkörning av en konkurrentretarder för ytterligare fördjupade kunskaper om problemet. Där samtidigt ett av koncepten med en bländarskiva mellan rotor och stator provades, dock med ett resultat som inte kunde anses tillräckligt. Efter detta kunde det konstateras att den bäst lämpade släpförlustreduceringsmetoden för Scania bör vara att helt frikoppla retardern från växellådan vid avaktivering då ett flertal av de största förlusterna som mättes upp kunde härledas in diverse tätningar och lager och inte till själva retardern. Denna frikoppling bör förslagsvis ske genom någon form av synkroniseringsinkoppling för att minimera vikt, storlek och kostnad. Slutligen kan det konstateras att kunskapen om vad som exakt sker i en retarder är begränsad och att det är ett komplext område. Vidare bör simuleringsmodeller användas för att minimera utvecklingsarbetet och ytterligare studier på hur en effektiv frikoppling kan användas bör genomföras. Nyckelord: retarder, släpförluster, växellåda / In order to increase the drive efficiency and safety as well as to minimize the brake wear, most Scania trucks and busses are equipped with a complementary brake system, also known as a retarder. A retarder generally works under one of the following two principles. An electromagnetic retarder that brakes the propeller shaft, drive axles or the gearbox using electromagnetic induction or as in Scania's case using a hydrodynamic brake that brakes the propeller shaft by pumping a fluid thru a rotating turbine shaped system. The braking energy then turns to heat which then cools off by the engine’s cooling system. The brake power is controlled by the fluid pressure in the retarder. At its maximum, the brake power exceeds the power of the engine. When the retarder is deactivated, the system is not pressurized. But even then, it creates a small slip loss, because the retarder is still rotating with the gearbox. This slip loss is a fraction compared to the braking torque than can be used, but from a fuel efficiency standpoint it is still important that it is kept at a minimum. The goal of this master thesis is to investigate how to minimize these losses. To find out which the best suited solution for Scania would be, different concept studies has been carried out. A study of competitors and other applications where further inspiration could be obtained was conducted and a number of concepts were developed. Thereafter a test run of a retarder from a competitor for further in-depth knowledge was conducted. At the same time one of the concepts with an aperture plate between the rotor and stator was tested on the competitor retarder. With a result that could not be considered sufficient. After this it was found that the most appropriate slip reduction method should be to completely disengage the retarder from the gearbox at deactivation since most of the losses that was measured could be traced to various seals and bearings and not to the retarder itself. The decoupling should be done through some kind of synchronization unit to minimize weight, size and cost. Finally it was observed that the knowledge about what’s exactly happening in the retarder is limited and that it is a complex area. Furthermore should the use of simulation models enhance to minimize the development work and further studies about how to disengage the retarder in the most effective way should be worked out Keywords: losses, retarder, slip

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