Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The use of gas turbines in central receiver solar power plant cycles has become an increasingly popular research topic. This has led to the need to investigate and analyse the effect of the solar receiver on the gas turbine cycle. The aim of this thesis is to construct an experimental gas turbine setup to accommodate further research on utilizing solar energy to power gas turbines. The gas turbine under consideration is the Rover Gas Turbines 1S/60. The focus of this investigation is the centrifugal compressor of the gas turbine. An increase in static pressure is required for the gas turbine to cope with anticipated pressure drops in the central receiver that will be part of the gas turbine cycle. The standard compressor design is analysed by means of 3-D (CFD) analysis using CFX® and experimental data. The new centrifugal compressor is designed by means of 1-D and 3-D (CFD) analysis using CompAero and CFX®. The aim is to design a compressor that maximizes the total-to-static pressure ratio. The size of the compressor is highly constrained by the geometry parameters of the gas turbine. Since the turbine rotor will remain unchanged, the power input, mass flow rate and rotational speed must stay the same. The experimental setup was build and the numerical results of the standard compressor were validated against the experimental results. A new centrifugal compressor was designed. The total-to-static pressure ratio was increased from 2.50 to 3.30 at an operating speed of 46 krpm. The efficiency of the compressor was improved from 63.8% to 85.6%. The input power of the new compressor design deviated 1.6% from the set benchmark, and 1.3% from the numerical data of the standard compressor. / AFRIKAANSE OPSOMMING: Die gebruik van gasturbines in sonkragstasiesiklusse met ’n sentrale ontvanger het gegroei tot ’n gewilde navorsingsonderwerp. Dit het gelei tot die behoefte om die effek van die sonontvanger op die gasturbinesiklus te ondersoek en te analiseer. Die doel van hierdie tesis is om ’n eksperimentele gasturbine opstelling te bou vir verdere navorsing oor die benutting van sonenergie om ’n gasturbine aan te dryf. Die gasturbine in oorweging is die Rover Gas Turbines 1S/60. Die fokus van hierdie ondersoek is die sentrifugale kompressor van die gasturbine. ’n Toename in statiese druk word benodig vir die gasturbine om die verwagte drukverlies in die sentrale ontvanger, wat deel uit maak van die gasturbinesiklus, te hanteer. Die standaard kompressor ontwerp is geanaliseer deur middel van 3-D Berekenings Vloeimeganika (BVM) analises met behulp van CFX® en eksperimentele data. Die nuwe sentrifugale kompressor is ontwerp deur middel van 1-D en 3-D BVM analises met behulp van CompAero en CFX®. Die doel is om ’n kompressor te ontwerp wat die totale-tot-statiese drukverhouding maksimeer. Die grootte van die kompressor is beperk deur die geometrie van die gasturbine omhulsel. Aangesien die turbinerotor onveranderd sal bly, moet die insetdrywing, massa-vloeitempo en rotasiespoed dieselfde bly. Die eksperimentele opstelling is gebou en die numeriese resultate van die standaard kompressor is teenoor die eksperimentele resultate gevalideer. ’n Nuwe sentrifugale kompressor is ontwerp. Die totale-tot-statiese drukverhouding is verhoog van 2.50 tot 3.30 teen ’n rotasiespoed van 46 000 omwentelings per minuut. Die doeltreffendheid van die kompressor is verbeter van 63.8% tot 85.6%. Die insetdrywing van die nuwe kompressor ontwerp het met 1.6% afgewyk van die vasgestelde maatstaf, en met 1.3% van die numeriese data van die standaard kompressor.

Stratification of water in large reservoirs occurs in summer, or at anytime in hot climates where the water surface is exposed long-term to sunlight and the water surface is heated. Natural mixing will not occur due to the cooler and denser water always staying at the lower levels. Therefore, mechanical circulators are designed to prevent water quality problems related to stratification and depletion of dissolved oxygen. Impellers that produce the flow in mechanical circulators are available in different sizes and these impellers are designed to produce different flow rates. Due to hydraulic loadings, impellers have to be strong and durable. Loadings on impellers depend on their geometries and therefore, a durable impeller is a good combination of the use of correct materials and good geometry. Long and slender impellers are prone to failure when subjected to high hydrodynamic loadings. Nowadays, designers have very limited information on predicting the stresses on impellers and the deflection patterns of impellers because there are no design rules in designing these impeller blades and there is no such thing as "best geometry". A good impeller blade design is by guesswork and experience. In order to design the geometry that suits this application, trial-and-error finite element analyses have been conducted in this project to minimize stress levels on the blades. This research involves the use of finite element analysis (FEA) to predict stress and deflection of impeller blades used on large (5m diameter) ducted axial flow impellers as the first step in the design process. Then, based on the results, improvements have been done to the models until the final design was made. As far as the author has been able to determine, this has not been researched before. Finite Element Analysis has been used on wind turbine blades, rudders and hulls of boats but not on axial flow impeller blades of the type used in this project. For the purpose of this project, commercial finite element computer program packages STRAND6 and STRAND7 were used as the main analysis tools. A static line load increasing linearly with radius along the blade has been used to simulate the assumed hydrodynamic loading, and applied to all FEA blade models. The analysis results proved the stresses on blades are largely dependant on the blade geometry. From the analysis results, the author modified the stacking arrangement of the FEA elements in order to minimize both the tensile stresses and the displacements of the blades at the tip. Parametric studies have been done in order to obtain the best FEA impeller blade model.

<p>The thesis investigates if it is possible to replace several pumpimpellers with one controllable pumpimpeller, with a economical and a manufacturing analisys aspect. The studied pumpimpeller is mounted on a midrange wastewaterpump, N3127MT.</p><p>In the thesis a contemplated manufacturing process is evaluated for a concept that are supposed to act as a controllable pumpimpeller. The pumpimpeller are studied in a manufacturing and flow matter and are presented in the thesis.</p><p>The manufacturing cost is also estimated, and this has been compared to the storage cost and other costs that the existing pumpimpeller generates.</p><p>The thesis also shows that the concept has minor losses in cutting quality aswell as the effiency comparing to the existing pumpimpeller.</p><p>The concept also raises the manufacturing cost and this increasing cost makes the presented concept to expensive to carry through.</p><p>An investigation of the costs that the existing pumpimpeller produces has also been done, and this shows that there is not that much expenses to earn regarding to for example the storage cost. The storage cost includes information from Flygt’s central storagecenter in Lindas, Sweden and Metz, France, and also an inventory about the pumpimpellers located at Flygt’s different distributors worldwide.</p><p>The thesis shows that a controllable pumpimpeller will generally increase the cost for the pumpimpeller and the performance of the pumpimpeller will decrease.</p>

The thesis investigates if it is possible to replace several pumpimpellers with one controllable pumpimpeller, with a economical and a manufacturing analisys aspect. The studied pumpimpeller is mounted on a midrange wastewaterpump, N3127MT. In the thesis a contemplated manufacturing process is evaluated for a concept that are supposed to act as a controllable pumpimpeller. The pumpimpeller are studied in a manufacturing and flow matter and are presented in the thesis. The manufacturing cost is also estimated, and this has been compared to the storage cost and other costs that the existing pumpimpeller generates. The thesis also shows that the concept has minor losses in cutting quality aswell as the effiency comparing to the existing pumpimpeller. The concept also raises the manufacturing cost and this increasing cost makes the presented concept to expensive to carry through. An investigation of the costs that the existing pumpimpeller produces has also been done, and this shows that there is not that much expenses to earn regarding to for example the storage cost. The storage cost includes information from Flygt’s central storagecenter in Lindas, Sweden and Metz, France, and also an inventory about the pumpimpellers located at Flygt’s different distributors worldwide. The thesis shows that a controllable pumpimpeller will generally increase the cost for the pumpimpeller and the performance of the pumpimpeller will decrease.

Impellers are important components in the field of aerospace, energy technology, and precision machine industries. Considering the high accuracy and structural integrity, impellers might be manufactured by cutting. Due to their complex geometries and high degrees of interference in machining, multi-axis machines are requested to produce impellers. The object of this thesis is to improve 5-axis tool paths for surface quality of impellers by smoothing point cutting tool paths in terms of linear segments and B-Splines and by using flank milling technologies with linear segment and B-Splines tool paths. Experimental results show that the surface quality of impeller blades can be improved by point cutting with smoothed tool paths and by flank milling. Moreover, the required milling time can be reduced by 18 percent and 13percent based on smoothed linear tool paths and smoothed B-Splines tool paths, respectively.

Heart disease is the developed world's biggest killer, and the shortage of donor hearts has accelerated the development of mechanical alternatives. Scientists, engineers and clinicians have attempted to replicate the human heart with a mechanical device for over 50 years. Although a number of pulsating devices have been developed, and in some cases worked briefly, they have invariably failed to match the success of heart transplantation. In an attempt to produce a suitable alternative, current research is focused on devices that do not replace the heart; but rather work along side it to assist its function. Many of these devices help the failing left ventricle; however some patients require the additional implantation of a second device to assist a failing right ventricle. This increases implantation time and associated risk, and because of the size of the current devices, reduces the access of smaller patients to this vital technology. The overall thesis objective focuses on the progressive design, development and preliminary evaluation of two novel centrifugal type ventricular assist devices, a bi-left ventricular device (Bi-LVAD) and a single bi-ventricular assist device (Bi-VAD). The devices have the respective capability to assist either the left ventricle, or both ventricles of a failing heart. The current concept for each VAD employs both magnetic and hydrodynamic suspension techniques to float a rotating double impeller, a technique that aims to reduce blood damage and component wear, two of the major problems encountered with current generation devices. Each VAD design was developed by conducting experimentation and drawing conclusions from a variety of engineering research fields, such as flow visualization, rotary pump design and testing, fluid dynamics, hemodynamics and heart failure, and magnetic motor bearing design. In order to evaluate pump prototype designs, it was necessary to design and develop a novel pulsatile systemic and pulmonary mock circulation loop capable of reproducing the hemodynamics of heart failure in the systemic and pulmonary circuits. The investigation then specifically examined the static hydraulic forces on the impeller of a centrifugal blood pump during operation in this mock circulation loop. The recorded magnitude and direction of radial and axial thrust then influenced the selection of magnetic and hydrodynamic bearing configurations to minimise impeller touchdown in the intended hemodynamic environment. This research required the development of correctly designed impeller (semi-open/closed) and volute (single, double, circular) components for each ventricular assist application and a unique test facility to isolate impeller hydraulic forces in addition to the mock circulation loop. The proposed Bi-LVAD incorporates symmetrical blade designs on each side of the double sided impeller. The device assists the function of the left ventricle only with symmetrical axial pressure distribution and elimination of stagnant regions beneath the impeller. These features improve axial touchdown capacity and reduce thrombus formation respectively. The proposed Bi-VAD incorporates different blade designs on each side of the double impeller to augment the function of both the left and right cardiac chambers. The design has the additional potential to act as a total artificial heart (TAH). To date there is no Bi-VAD/TAH system available that incorporates an LVAD and RVAD in one rotary pump. Successful development of each innovative VAD will provide an alternative to heart transplantation, potentially saving lives of many terminal heart patients each year. No longer would heart transplant candidates need to wait for the untimely death of a donor to provide a suitable heart. Instead, this new generation device would be available immediately, and be almost universally compatible with all patients. It has the potential to dramatically increase a patient’s expected lifetime, and to deliver them a higher quality of life.

The thesis considers a change in the manufacturing technology of a fan impeller from welding to 3D printing. The wish of the manufacturer was to investigate if such a change is possible and financially profitable and decide on a further approach to manufacturing. Models were created using information from the manufacturer and using them, conditions for manufacturing the impeller in the 1:1 ratio were derived. Based on the new technological process and the experience from prints a new price calculation for the fan impeller using 3D printing was created.

This dissertation focuses on the construction design of a sine pump. It particularly deals with loss minimisation and strives to solve problems relating to excessive wear of the scrapergate which separates suction and the delivery space. The first part of the dissertation describes a new construction variation of a sine pump and the second part deals with a more detailed study including optimisation of one variation.

The master's thesis deals with compressor turbochargers used for supercharging of combustion engines. The aim of the thesis is feasibility study of compressor surge limit simulation. First of all the principle and purpose of supercharged combustion engines is described and the compressors' types using for supercharging are mentioned as well. The main part of the thesis is focused on flow instabilities and their influence on compressor operating zone. There are mentioned some possibilities of operating zone extension. The practical part comprises the simplified computation of a one stage of centrifugal compressor and flow analysis by means of CFD simulation.

This master’s thesis deals with changing the geometry of the output section of the impeller of the radial centrifugal pumps and its influence on the characteristics of the pump. In engineering practice for these radial centrifugal pumps it is possible to change the parameters based on the requirements. This adaptation of parameters is called impeller trimming. Impeller trimming means the reduction of the impeller diameter thereby decreasing the flow, head and efficiency. Existing equations for calculating the changes in the characteristics of the impeller trimming are inaccurate. In this thesis is describes a possible method of putting for the recalculation characteristics of a pump based on the impeller diameter on the available characteristics of pumps.