Faculty of Engineering & Technology
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Browsing Faculty of Engineering & Technology by Author "Alugongo, A. A., Prof."
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Item Controllability and stability of selectively wettable nanostructured membrane for oil/water separation(Vaal University of Technology, 2019-12) Sob, Peter Baonhe; Alugongo, A. A., Prof.; Tengen, T. B., Prof.Presently, the current membrane technologies used in oil/water separation are inefficient with poor controllability and stability during oil/water separation. The has led to the current problem of membrane fouling and degradation during oil/water separation. Several approaches have been used to modify or design a better wettable surface with limited success since the current problem of membrane fouling is persisting. It is, therefore, necessary for scientists, engineers, and researchers to come up with a new membrane technology that will be more efficient with stable wettability and controllability during oil/water separation. Membranes are made up of nanoparticles on their surface, which are both random in nature. Furthermore, the collection of membrane particles to form mesh membranes are made of pores with further ransom spatial distribution. Thus, it was necessary to use the tools of stochastic processes to theoretically characterize these parameters. These parameters affect both internal and external factors as well as characteristics of random membrane particle and pores on wettability like surface tension and surface energy were established in the current project. Design and production of the membrane material according to established relationships was by both low and high-pressure spay jet coating in a controlled laboratory environment, and microscopic characterization performed using SEM. TEM, EDS, statistical analysis, and Image J particle analyzer. The spread, orientation, morphology, spatial distribution, inter-separation distances, surface roughness, surface smoothness, contact angles, surface density of the particle, mean size of the coated nanoparticle on the membrane surface after different coating rounds were analyzed so as to establish conditions for optimal wettability. The testing of produced membranes under the application of external and internal factors was done. A centrifugal pump was used to pump contaminated oil and water mixture through the membrane under a steady flow rate of 10 L/s with a gauge pressure of 180 kPa at room temperature conditions. The membrane materials from different coating rounds were tested for their abilities to produce pure collected water or oil particles in the collected water. The separated water was analyzed using oil and grease analysis US EPA method 1664B with the SPE-DEX 1000 oil and grease system. As revealed theoretically and validated experimentally, it was found that the random natures of nanoparticle size, the spatial distribution of membrane channels, and their morphology have impacts on surface energy-driven separability of oil and water mixture. It was also observed that the scattering of nanoparticles on the membrane surface during coating lowered surface energy, which enhanced oil/water separation. It was also revealed that there is an optimal nanoparticle size, scattering, morphology, and spatial distribution of membrane channels that offer better separation of water from oil. From the microscopy analysis, different microstructures were revealed for glass, ceramics, and sediment during LP and HP coating. The microstructure characterization showed different surface densities of nanoparticles, mean particle sizes, surface roughness or smoothness, and nanoparticles inter-separation distances. It was also revealed that the materials, which were more stable and efficient with more controlled wettability were glass, sediment, and ceramic HP 3rd rounds of coating. Clusters were observed on the membrane surface during HP and LP coating rounds with more clusters observed in LP coating when compared with HP coating. These clusters increased surface energy, which negatively affected oil/water separation. It was concluded that to improved the wettability surface. membrane clusters must be minimized during coating rounds. This thesis contributed new knowledge to existing body knowledge of membrane technology used in oil/water separation in a number of ways by: (1) Designing a new membrane surface with a more controlled, efficient, and stable wettability process during oil/water separation. (2) Applying the logic of surface energy-driven separability, which has not been previously used extensively to study membrane wettability. (3) Establishing a model for the optimal membrane pore sizes that offer optimal membrane wettability during oil/water separation. (4) Establishing a model for optimal nanoparticle coating that offers optimal membrane wettability during oil /water separation. (5) A great attempt was made in characterizing nanoparticle surface densities, spread, particle coating, and nanoparticles intensity on a wettable membrane surface.Item Effect of fault and transmission error on a spur gear meshing stiffness by vibration and time-frequency techniques(Vaal University of Technology, 2021) Yakeu Happi, Kemajou Herbert; Tchomeni, B. X., Dr.; Alugongo, A. A., Prof.To meet the ever-increasing demand for maintenance of gear systems, industrial companies have traditionally depended on the shutdown of the machines before processing the fault diagnosis. Nowadays, online monitoring has proven to be effective in terms of machine state analysis and fault prediction. However, the application of such a technique in the analysis of combined multiple nonlinear faults is still a subject of research. The vibration signature of a coexisting nonlinear crack and pit in two-stage gear system is unknown, it can be regarded as one of the most difficult problems to extract and diagnose. Additionally, incorporating both a crack and a pit into numerical models is a time-consuming process that demands a breadth of mechanical understanding. Diagnostics of faulty gears, on the other hand, can be performed in the time and frequency domain or in the Time-Frequency domain, depending on the complexity of the vibration. Non-linear and non-stationary phenomena (Features) occur when repeated pitting and cracking faults occur, reducing the reliability of standard signal processing methods (Gear displacement and Fast Fourier Transform). This thesis solves each of these shortcomings by developing an eight-degree-of-freedom (DOF) gear model with a breathing crack and multiple pitted gear teeth. The identified spur-gear model enabled the investigation of the crack and pitting signatures and their effect on the ensuing vibrations independently of the action of other system components. Additionally, when pitting and cracking coexist, the study was conducted to determine the influence of such a failure on the transmission system. Theoretical results indicated that the presence of pitting and crack in the tooth of the gear resulted in a decrease in mesh stiffness. Additionally, the influence of the breathing pitting and crack results in material fatigue, which results in the generation of a random term in the vibration signal. To corroborate the acquired results, several experimental tests on a spur-gear test rig with a defined pit and crack size range were undertaken under a variety of conditions. In comparison to the presented methodologies, theoretical and experimental results indicate that 3D Frequency-RPM analysis is the most sensitive and resilient method for the early detection and identification of pit and crack faults. Furthermore, when crack or pit faults are studied individually, the STFT analysis yields interesting results. The feature analysis revealed that, when using the Time-Frequency technique, the crack and pit combination in a two-stage gear system is a priori more efficient than the other options.