The objective of this thesis is to create Gaussian 1D filters with rotating kernel theory which enables to program algorithm for noise reduction and beam structure highlighting in a digital picture of the solar corona. A fragment of original picture of solar corona and of pictures filtred by this algorithm is in the enclosure.

Conventional rotating machine vibration monitoring techniques are based on the assumption that changes in the measured structural response are caused by deterioration in the condition of the rotating machine. However, due to changing rotational speed, the measured signal may be non-stationary and difficult to interpret. For this reason, the order tracking technique was introduced. One of main advantages of order tracking over traditional vibration monitoring techniques, lies in its ability to clearly identify non-stationary vibration data, and to a large extent exclude the influences from varying rotational speed. Several order tracking techniques have been developed and researched during the past 20 years. Among these techniques, Fourier Transform Based Order Tracking (FT-OT), Angle Domain Sampling Based Order Tracking (AD-OT) and Vold-Kalman Filter Order Tracking (VKF-OT) are the three most popular techniques and have been commercialised in software. While the VKF-OT is comparatively new, and both its theory and application are different from the other two techniques, the unique advantages of this technique has led to increased research attention in this field. This growing interest in research on the application of the VKF-OT technique on real machines, and its comparative advantages with respect to other order tracking techniques, inspired the present research. With this work, a comprehensive literature of electrical machine condition monitoring was surveyed, which gives a broad perspective of electrical machine monitoring methods ranging through electrical techniques, vibration techniques, temperature techniques and chemical techniques. To simply the process of applying VKF-OT in initial investigations, simulated single-degree-of freedom and two-degree-of freedom rotor models were established, and the application of the VKF-OT technique on these simulated models was explored. Because most of the current research draws significantly on an understanding of the VKF-OT theory, it was also necessary to review and summarize the current status of VKF-OT theory from previous work, as well as explore the procedures for selection of its filter bandwidth when dealing with real data. An experimental set-up for monitoring an electrical alternator was constructed. Real experimental data were subsequently used to compare the advantages and disadvantages of the three popular order tracking techniques. The unique time domain advantage of VKF-OT was implemented, using crest factor and kurtosis values as indictors of the fault condition of the machine. This gave encouraging results. / Dissertation (MSc)--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / unrestricted

A centrifugal compressor is a mechanical machine with purpose to convert kineticenergy from a rotating impeller wheel into the fluid medium by compressingit. One application involves supplying boost air pressure to downsized internalcombustion engines (ICE). This allows, for a given combustion chamber volume,more oxygen to the combustion process, which is key for an elevated energeticefficiency and reducing emissions. However, the centrifugal compressor is limitedat off-design operating conditions by the inception of flow instabilities causingrotating stall and/or surge. These instabilities appear at low flow rates andtypically leads to large vibrations and stress levels. Such instabilities affectthe operating life-time of the machine and are associated with significant noiselevels.The flow in centrifugal compressors is complex due to the presence of a widerange of temporal- and spatial-scales and flow instabilities. The success fromconverting basic technology into a working design depends on understandingthe flow instabilities at off-design operating conditions, which limit significantlythe performance of the compressor. Therefore, the thesis aims to elucidate theunderlying flow mechanisms leading to rotating stall and/or surge by means ofnumerical analysis. Such knowledge may allow improved centrifugal compressordesigns enabling them to operate more silent over a broader operating range.Centrifugal compressors may have complex shapes with a rotating partthat generate turbulent flow separation, shear-layers and wakes. These flowfeatures must be assessed if one wants to understand the interactions among theflow structures at different locations within the compressor. For high fidelityprediction of the complex flow field, the Large Eddy Simulation (LES) approachis employed, which enables capturing relevant flow-driven instabilities underoff-design conditions. The LES solution sensitivity to the grid resolution usedand to the time-step employed has been assessed. Available experimentaldata in terms of compressor performance parameters, time-averaged velocity,pressure data (time-averaged and spectra) were used for validation purposes.LES produces a substantial amount of temporal and spatial flow data. Thisnecessitates efficient post-processing and introduction of statistical averagingin order to extract useful information from the instantaneous chaotic data. Inthe thesis, flow mode decomposition techniques and statistical methods, suchas Fourier spectra analysis, Dynamic Mode Decomposition (DMD), ProperOrthogonal Decomposition (POD) and two-point correlations, respectively, areemployed. These methods allow quantifying large coherent flow structures atvfrequencies of interest. Among the main findings a dominant mode was foundassociated with surge, which is categorized as a filling and emptying processof the system as a whole. The computed LES data suggest that it is causedby substantial periodic oscillation of the impeller blade incidence flow angleleading to complete system flow reversal. The rotating stall flow mode occurringprior to surge and co-existing with it, was also captured. It shows rotating flowfeatures upstream of the impeller as well as in the diffuser. / <p>QC 20171117</p>

The study investigated the informal savings approach as an income-generating and poverty alleviation tool for women. The focus of the study is specifically in the Nelson Mandela Bay Municipality. The purpose of the study was to explore the reasons behind the involvement of women, in particular, to the use of informal savings as a tool for income generation and poverty alleviation. South Africa is characterised by inequitable growth and development, a high degree of poverty, increasing demands and limited resources. It is because of this backdrop that many women in poor communities, both rural and urban, devised brilliant plans to overcome this setback. Women, particularly African women, have for a long time been side-lined in economic decision making activities, both in their homes and elsewhere. For the purposes of this study, a mixed method research approach was employed, meaning that the study will follow both the qualitative and quantitative approaches. The respondents are a mixture of both literate and illiterate persons, and because of that, the researcher had to use both English and the home language of the respondents to explain the contents of the questionnaires and obtain the relevant information. The study identified the reasons that stokvels, which were believed to be popular in the past, and still are, because Black people in South Africa did not have access to formal financial institutions, remain popular long after the demise of apartheid. It is in the interest of the citizens of Nelson Mandela Bay Municipality to archive the financial activities of its inhabitants as this valuable information will be needed by future generations. This can be done by creating a website or adding a link to the existing ones where the information is readily available for the users. For future research purposes, stokvels in various parts of the Municipality and South Africa as a whole need to be studied in order to identify and compare to the available literature the general success factors.

The healthy condition of a rotating machine leads to safe and cheap operation of almost all industrial facilities and mechanical systems. To achieve such a goal, vibration-based condition monitoring has proved to be a well-accepted technique that detects incipient fault symptoms. The conventional way of On-Bearing Vibration Measurement (OBVM) captures symptoms of different faults, however, it requires a relatively expensive setup, an additional space for the auxiliary devices and cabling in addition to an experienced analyst. On-Shaft Vibration Measurement (OSVM) is an emerging method proposed to offer more reliable Faults Diagnosis (FD) tools with less number of sensors, minimal processing time and lower system and maintenance costs. The advancement in sensor and wireless communications technologies enables attaching a MEMS accelerometer with a miniaturised wireless data acquisition unit directly to the rotor without altering the machine dynamics. In this study, OSVM is analysed during constant speed and run-up operations of a test rig. The observations showed response modulation, hence, a Finite Element (FE) analysis has been carried out to help interpret the experimental observations. The FE analysis confirmed that the modulation is due to the rotary motion of the on-shaft sensor. A demodulation method has been developed to solve this problem. The FD capability of OSVM has been compared to that of OBVM using conventional analysis where the former provided more efficient diagnosis with less number of sensors. To incorporate more features, a method has been developed to diagnose faults based on Principal Component Analysis and Nearest Neighbour classifier. Furthermore, the method is enhanced using Linear Discriminant Analysis to do the diagnosis without the need for a classifier. Another faults diagnosis method has been developed that ensures the generalisation of extracted faults features from OSVM data of a specific machine to similar machines mounted on different foundations.

In this study we investigates the thermal behavior of an assembly of consecutive cylinders in a counter-rotating configuration cooled by natural convection with the objective of maximizing the heat transfer density rate (heat transfer rate per unit volume). A numerical model was used to solve the governing equations that describe the temperature and flow fields and an optimization algorithm was used to find the optimal structure for flow configurations with two or more degrees of freedom. The geometric structure of the consecutive cylinders was optimized for each flow regime (Rayleigh number) and cylinder rotation speed for one and two degrees of freedom. Smaller cylinders were placed at the entrance to the assembly, in the wedge-shaped flow regions occupied by fluid that had not yet been used for heat transfer, to create additional length scales to the flow configuration. It was found that the optimized spacing decreases and the heat transfer density rate increases as the Rayleigh number increases, for the optimized structure. It was also found that the optimized spacing decreases and the maximum heat transfer density rate increases, as the cylinder rotation speed was increased for the single scale configuration at each Rayleigh number. Results further showed that there was an increase in the heat transfer density rate of the rotating cylinders over stationary cylinders for a single scale configuration. For a multi scale configuration it was found that there was almost no effect of cylinder rotation on the maximum heat transfer density rate, when compared to stationary cylinders, at each Rayleigh number; with the exception of high cylinder rotation speeds, which serve to suppress the heat transfer density rate. It was, however, found that the optimized spacing decreases as the cylinder rotation speed was increased at each Rayleigh number. Results further showed that the maximum heat transfer density rate for a multi scale configuration (with stationary cylinders) was higher than a single scale configuration (with rotating cylinders) with an exception at very low Rayleigh numbers. / Dissertation (MEng)--University of Pretoria, 2012. / Mechanical and Aeronautical Engineering / unrestricted

Elevados níveis de vibração podem levar um equipamento à fadiga, e consequente quebra, podendo causar perdas de produção, problemas de fornecimento de material ou de serviço. Este trabalho desenvolveu um sistema para acionamento, aquisição e análise de uma bancada de ensaio de vibração em máquinas rotativas. O sistema proposto é composto por uma bancada com um motor fixo a uma plataforma, cujo eixo está acoplado a um rotor que pode sofrer desbalanceamento, através de inserção de massas. A rotação do eixo do motor é mensurada por um sensor indutivo, a vibração no mancal é monitorada por um acelerômetro. Para controle de acionamento e aquisição de dados foi utilizado o software LabVIEW. Esta bancada foi desenvolvida com a finalidade de estudar o comportamento dinâmico do rotor que está apoiado em mancais de rolamento. A estrutura montada permite simulação de falhas. Neste trabalho foi proposto o desbalanceamento de massa em um único plano, que é classificado como desbalanceamento estático. Este tipo de simulação foi escolhido também, visto que o rotor só possui um plano para desbalanceamento. Foram realizados experimentos que possibilitaram a detecção das falhas através do nível de vibração medido pelo acelerômetro e através da frequência do sinal de vibração foi comprovado que a amplitude significativa do espectro ocorre na frequência de rotação do equipamento, quando se trata de desbalanceamento. A bancada foi desenvolvida para ser utilizada no Laboratório de Vibrações Mecânicas da Universidade de Taubaté, porém as técnicas desenvolvidas podem ter aplicabilidade no ramo industrial, principalmente em manutenção preditiva. / High levels of vibration equipment can lead to fatigue and consequent breakage, may cause production losses, problems of supply of equipment or service. This study developed a system for triggering, acquisition and analysis of a bench test vibration in rotating machines. The proposed system consists of a bench with a motor fixed to a platform whose shaft is coupled to a rotor imbalance can suffer through insertion of mass. The rotation of the motor shaft is measured by an inductive sensor, vibration in the bearing is monitored by an accelerometer. To drive control and data acquisition software was used LabVIEW. This bench was developed in order to study the dynamic behavior of the rotor that is supported by ball bearings. The assembled structure allows fault simulation. This work proposes the unbalance mass in a single plane, which is classified as static unbalance. Such simulation was also chosen since the rotor has only one plan for unbalance. Experiments were performed which allowed the detection of faults through the vibration level measured by the accelerometer and by the frequency of the vibration signal has been proven that the amplitude of the spectrum of significant vibration occurs in the rotation frequency of the machine when it comes to unbalance. The bench has been developed for use in Mechanical Vibration Laboratory at the University of Taubate, but the techniques developed may have applicability in the industrial sector, especially in predictive maintenance.

The most main wall insulations of rotating electrical high voltage machines consists of several layers of wound mica tape impregnated with epoxy resins. Methylhexahydrophthalic anhydride and Hexahydrophthalic anhydride are the state-of-the-art curing agents in epoxy insulations and are therefore essential components of the insulation system. Both anhydrides were proposed to the candidate list of Substances of Very High Concern and are therefore part of the European REACH authorization process. The prohibition or restricted use of both anhydrides in Europe in the future is possible and puts high pressure on the European manufacturers of electrical devices. Possible substitutes are available, but have to be qualified e.g. with respect to their dielectric properties. Hence, this paper compares several insulating resin systems with and without anhydride curing agents regarding their dielectric loss behavior. The results reveal that the curing agent has a measurable effect on the dielectric losses. Furthermore, the investigated anhydride-free insulation systems are a viable substitute at least with regard to their dielectric losses.

The objective of this thesis is to create Gaussian 1D filters with rotating kernel theory which enables to program algorithm for noise reduction and beam structure highlighting in a digital picture of the solar corona.

The construction of swirl turbine with counter-rotating runners. Master's thesis of master's studies of 2th years. This master's thesis is a technical report. The content of this technical report is engineering design of turbine, strength calculation of designed parts, design of bearings and development drawings for production.