Mechanical Engineering

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Browsing Mechanical Engineering by Author "Alugongo, A. A., Prof."

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    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.
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    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.
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    Enhancing wind turbine performance in cold climate through analysis of aerodynamic lift and drag
    (Vaal University of Technology, 2022) Odiagbe, Franklin Oyakhilomen; Masu, L. M., Prof.; Alugongo, A. A., Prof.
    Wind energy is one of the most economically sustainable energy, and power plays an important role in the diversification of energy security. Renewable energy resources such as wind energy are constantly replenished, and it is inexhaustible. Being one of the most environment-friendly and renewable, wind energy attracts enormous interest globally. However, wind energy production faces severe challenges in harshly cold climates or low-temperature conditions. Cold weather reduces the aerodynamic lift and increases aerodynamic drag, as ice accretes on the wind turbine blades. Some of the best sites for wind farms installation are cold regions, where the air density is favourable because of low-temperature conditions. Super-cooled droplets and precipitation affect the wind turbine operations and change the aerodynamic profile of the blade through ice accretion. This dissertation focuses on enhancing wind turbine performance in cold climate through ice accretion. this dissertation focuses on enhancing wind turbine performance in cold climate through analysis of aerodynamic lift and drags, using Computational Fluid Dynamics (CFD) and electromagnetic radiation principles. This is based on heat and mass transfer mechanisms of operation to prevent ice accretion on the turbine blades. To optimize the large wind turbines operation in ice prone cold regions, it is important to better understand the ice accretion behaviour and its effects on aerodynamic performance and power production losses. Numerical simulations on ice accretion for wind turbine aerodynamic were carried out for glaze and rime ice conditons using ANSYS. A multiphase based Computational Fluid Dynamic ANSYS was used to analyse electromagnetic radiation and the heat and mass transfer on the wind turbine. Results show that icing on a wind turbine can be mitigated using electromagnetic radiation and heat and mass transfer. Conservation of momentum and heat and mass transfer was applied to determine the effect of ice accretion on aerodynamic lift and drag. Ice mainly accretes along the leading edge of blade profile, which changes the aerodynamics profile by increasing surface roughness and heat fluxes during glaze and rime ice accretion. The effect of electromagnetic radiation on icing time and wind turbine rotation speed were analysed using the working principle of the infrared thermography ice sensing technique. Data collected by infrared sensors were used to retrieve features and parameters (temperature, icing time and wind turbine rotation speed) of the observed surface, without physical contact. The performance of electromagnetic radiation on wind turbine blades aerodynamic forces using Computational Fluid Dynamics (CFD) with Navier-Stokes equations and heat and mass transfer has been analysed and recommendations were drawn from the conclusions. The results from this investigation shows that electromagnetic energies are promising techniques for measuring critical parameters such as wind speed, icing time, and temperature of ice accretion. The electromagnetic energy (thermal infrared sensor) also detects the presence, type, location, thickness, and rate of the ice on a blade's surface. The combination of passing temperature gradients of fluid and solid requires heat transfer. The flow rate of passing temperature through the process (heat and mass transfer) has an essential impact on the application of Navier-Stroke equations for fluid around the wind turbine aerodynamic coefficients.
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    Improving the performance of membrane backwash system for efficient and stable wettability process during oil/water separation
    (Vaal University of Technology, 2022-10) Mopeli, Motebang Josias; Alugongo, A. A., Prof.; Sob, P. B., Dr.; Tengen, T. B., Prof.
    Membrane technology has enormous potential for oil/water separation applications. However, membrane performance is hampered by the ongoing fouling issue. Membrane fouling does not only affect the water permeability and separation efficiency but it also reduces the membrane lifespan. Numerous studies on backwash optimization have been conducted to reduce the fouling effect. However, it's worth mentioning that none of the studies in membrane backwash on oil/water separation applications has attempted to improve the cleaning procedure by identifying critical operation conditions through numerical model simulation and experimentation. In the past, accurate modelling of the backwash flow to dislodge the foulants found on the membrane pores or surfaces (concentration polarization) in pressure-driven membrane processes was hindered by complex couplings between the flow equations and the variable operating properties. However, the developed backwash model in this study is based on Navier Stokes laws which govern the entire flow field that incorporate the backwash media flow domain, and oil droplet dislodgement on the membrane domain. The varying nature of flow necessitates different modelling methodologies to help predict the behaviour of backwash flow. As such, Navier Stokes's laws governing the fluid flow were the obvious choice, due to their high accuracy and diversity in describing a whole set of flow phenomena:, from laminar to turbulent under Newtonian flow. Additionally, incorporating computational fluid dynamics (CFD) ANSYS Fluent numerical model simulation, as a preliminary evaluation tool to improve the backwash cleaning efficiency for oil/water separation application has shown to be an effective approach. This developed backwash model depends heavily on the backwash critical operating parameters such as temperature, driving back-pressure, and the subsequent backwash flow velocity. The theoretical numerical simulation model and experimental results were in good agreement that oil droplets can be dislodged effectively, only if the critical backwash operating conditions for oil/water separation application are identified and utilized. These critical operating parameters are identified to improve the backwash system, such as the thermal forces applied to lower the oil viscosity (critical temperature 0 65 c) and the critical pressure (190kpa) was subsequently utilized to loosen the interfacial tension force(adhesive forces). Consequently, the oil droplet blockage was easily dislodged by the backwash flowmedia (backwash velocity). Ultimately, this study investigated the dynamic relationship of the proposed critical operating parameters (temperature, pressure, and the subsequent backwash flow velocity) with membrane material capable of withstanding this proposed intense backwash procedure. The evaluation criteria were focused on permeate flux recovery, thermal stability, and the ability of the membrane to withstand harsh operating conditions during the backwash procedure. Consequently, this study developed an improved backwash cleaning procedure in relation to membrane material selection for efficient wettability which has proven to be an effective approach to control fouling during oil/water separation. According to the results obtained, the use of critical backwash pressure resulted in efficient fouling removal. In addition, the thermal stability of ceramic membrane permits the use of high temperature by backwash parameter to lower the oil droplets viscosity, subsequently allowing easy dislodgement of foulants found on the membrane structure. Consequently, this attempt to exploit the research gap in membrane backwash has led to this dissertation contributing to advancing new knowledge of membrane technology for application in oil/water separation. The contributions of the project includes: 1. Establishing the most efficient backwash process, through the identification of critical operating conditions (temperature, pressure, and the subsequent backwash flow velocity) using Navier Stokes laws under fluid flow modelling. 2. Designing a numerically simulated model by utilizing computational fluid dynamics (CFD) ANSYS Fluent software tool, as a preliminary evaluation measure, to validate an improved backwash procedure 3. Establishing an improved backwash cleaning procedure in relation to membrane material design for efficient wettability to mitigate fouling during oil/water separation.
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    Performance analysis and modelling of diesel engine operational characteristics using pyrolytic oil from scrap tyre
    (Vaal University of Technology, 2017-07) Mwanzi, Maube Obadiah; Masu, L. M., Prof.; Alugongo, A. A., Prof.
    In this work, an investigation on the fraction of tyre pyrolysis oil with a similar distillation range to that of automotive diesel (150 – 360 oC) was carried out to determine its suitability as an alternative or additive to petro-diesel fuel. The quality of this oil was evaluated by comparing its key properties to the requirements of South African National Standards for Automotive diesel fuel (SANS-342) and to conventional automotive diesel fuel. The viscosity, density, copper strip corrosion of this fuel were found to be within the acceptable limits set by SANS while sulphur content and flash point were out of their respective set limits. In addition, mixing rule equations for predicting viscosity and density for both pure and blends of the oil as a function of temperature were developed and evaluated. The equations were found to be suitable due to their low Absolute Percentage Deviation. Engine performance tests were carried out with blends of Distilled Tyre Pyrolysis Oil (DTPO) and petro-diesel fuel in a single cylinder air cooled diesel engine. The performance, emission and combustion characteristics of the diesel engine while running on these blends were evaluated and subsequently, a comparative analysis was performed with conventional petro-diesel fuel as the reference fuel. It was found that, the engine could run with up to 60% (DTPO) without any problem. Beyond this level the engine became unstable. The power and torque were similar at low and medium speeds. However, at high speeds, the power dropped with increase in DTPO in the blend. Fuel consumption was very comparable for all the test fuels. Carbon monoxide and unburned hydrocarbons were higher for the blends compared to petro-diesel fuel but oxides of Nitrogen were lower. The peak pressure for petro-diesel fuel was marginally higher than that of the blends. Present results indicate that, petro-diesel fuel can be blended with up to 60% DTPO and produce acceptable performance. Testing the diesel engine under different operating conditions is a time consuming and expensive process that also requires the use of specialised equipment which may not be readily available. An Artificial Neural Network (ANN) model based on a back-propagation learning algorithm was developed to predict engine performance and emissions separately, based on fuel blend and speed. The performance and accuracy of the model were evaluated by comparing experimental and ANN predicted results. The ANN was able to predict both engine performance and emissions with acceptable levels of accuracy. The values of correlation coefficient between experimental and predicted data being greater than 0.99. From this work, it can be implied that engine emission and performance can be predicted using neural network-based mode, consequently, it will be able to do further investigations without running laboratory experiments. Energy recovery from waste is an interesting field for engineers and scientists. It is hoped that this work will prompt new research ideals on how tyre pyrolysis oil can be improved for use as diesel engine fuel and building better models for diesel engine performance and emissions