M. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Fault diagnosis of a rotor system operating in a fluid is one of the most difficult aspects of rotating machinery. Fluid in machinery plays a significant role in concealing the allowable rubbing stress limit during the impact generated from the rotor-stator rub which may progressively deteriorate the rotating system. Therefore, a numerical and experimental investigation was performed to analyse the influence of the fluid during the rotor-stator contact of a vertical rotor system partially submerged in an incompressible inviscid fluid with a focus on detecting rubbing fault in the presence of axial load. The theoretical model of lateral-torsional rotor consists of a 3-D rub-impact induced parametric excitation, which was assimilated to operate as elastic vertical rotor system by considering the transient vibration of a flexible axial force and energy of the vertical shaft system. The model was established based on Jeffcott rotor, time-varying stiffness and the rotor-stator fluid interaction. The Lagrangian principle was used to establish the governing equation of motion. The hydrodynamic forces acting on the vertical rotor were established and introduced into the system based on the Laplace form of the linearized Navier–Stokes equations under lateral excitation yielding a highly nonlinear 5-DOF system. To evaluate the dynamic response and ensure the accurate acquisition of rubbing features in a fluid, the classical Fast Fourier Transform (FFT) and the vibration waveform have been discretised and illustrated through the frequency components. Furthermore, for effective extraction of some hidden features of rub, the nonlinear features embedded in the vibration waveform have been discretised and illustrated through to the lateral deformation of the rotor and the orbit patterns of the shaft. Qualitative numerical analysis suitable for highly nonlinear and non-stationary signal Time-Frequency strategies, Wavelet Synchrosqueezed Transform (WSST) and Instantaneous Frequency (IF) technique were employed to successfully extract the frequency of oscillating modes and the periodic frequency response of the faulted rotor system. It is demonstrated that the coupled lateral-torsional vibration of the submerged vertical rotor system has the potential to enhance the much-unwanted hidden frequencies of vibration that leads to significant instability of the rotor system. In particular, the responses revealed the existence of unstable regimes with respect to the lateral-torsional deflection as well as the angular velocity. High harmonic peaks were also identified at the critical speed, which can be considered as a monitoring index to detect the rubbing in rotating shafts in a fluid. It was found that even at relatively slow rotating speed fluid elastic forces induced by the co-rotating flow surrounding the shaft significantly affect the transverse natural modes of vibration of the shaft. Despite the interaction between the fluid and the rotor generates self-excitation of low frequencies, obtained results indicated that the fluid-rotor interaction reduces the dynamic vibration response of the faulted system running below the second critical speed. It has been analytically demonstrated that the time-varying stiffness induced is the principal cause of the frequency-modification feature of the dynamic response of an unbalance-rub rotor system at the contact region. The model investigated in this study has potential application for drill string-borehole shaft system used in the oil industry.

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Traditional wireless site surveys produce a heat-map of link strength or quality over a target area, usually on the ground plane. In recent years research has gone into using aerial drones in network attack and surveillance, making three dimensional awareness of wireless coverage areas of interest. A multi-rotor drone and data collection module were built and tested as part of this research. Site assessments were conducted both in open space and near structures. Collected data was interpolated across the target area, and visualized as points and contours. These visualizations were exported to a Keyhole Markup Language (KML) for visualization in context. Resulting visualizations proved to be beneficial in identifying the coverage area of both authorized and rogue access points.

With the growing concern of the accumulation of plastic-based food packaging waste, the search for bio-based biodegradable packages is on the rise. These materials differ from their petro-based counterparts in their degradation rates, which are much higher in the former. Not only do bio-based biodegradable materials degrade faster during post-usage processes but also they age faster during usage and storage, which affects their performance and functionality. The application of noninvasive testing methods with the capability to report on the matrix’s state could assist in the development of a more ubiquitous way to assess ageing in food packaging, particularly in biodegradable ones. To this end, the performance of a luminescence spectroscopy technique based on three luminescent probes, one intrinsic to the matrix and two added, was monitored and the sensitivity of the probes to report on ageing was analyzed. Biodegradable films were made of 2% gelatin (type A) and 0.5% glycerol (plasticizer). Gelatin contains an intrinsic fluorophore, the aromatic amino acid tyrosine (Tyr), which can report on the molecular mobility of a matrix. Additionally, the films were doped with two extrinsic fluorophores, Fast Green FCF (FG) at 0.124 mM and pyranine (Pyr) at 0.05 mM, which can report on the physical state and available free water within a matrix, respectively. Films were casted onto plastic Petri dishes and stored at five relative humidities (RHs), namely 2.5, 25, 33, 53, and 75%, for five weeks with measurement collection every week. Films were tested using fluorescence spectroscopy at excitation and emission range wavelengths optimized depending on the assessed probe. Additional measurements to determine moisture content, changes in secondary protein structure using FTIR spectroscopy, and mechanical properties using a Universal Testing Machine in tensile mode aided in the evaluation of the sensitivity of the luminescent probes in sensing ageing. Luminescent probes, intrinsic or added, have the capability to assess the physical state of the films in situ and can provide molecular level sensing of their local environment. Tyr emission showed a sharp increase in fluorescence intensity in films stored at low RH as a function of time. FG showed a similar pattern to that of Tyr but higher sensitivity to changes along the observed period. The two characteristics emission bands of Pyr provide information on the state of water within the matrix. Although the results on this probe hinted microstructural rearrangements within the films as a function of time, the sensitivity of this probe was not high enough at the conditions evaluated and provided limited information on films’ solvation. The sensitivity of the luminescent probes to changes during ageing were revealed through correlation of the photophysical properties of the two effective probes, Tyr and FG, and the mechanical properties of the films at different RH through storage. Both methods, mechanical and optical, were similarly sensitive to changes during ageing particularly after 3-week storage. However,, it can be speculated that because of the different scales at which optical and mechanical measurements report (local vs. bulk), the methods, they could also complement each other. These findings suggest that, in principle, a luminescence spectroscopy technique using intrinsic and extrinsic probes can replace mechanical testing to noninvasively monitor structural changes and stability of biodegradable packaging as a function of time.

The identification and characterization of molecular biomarkers using mass spectrometry on an orbiting or fly-by spacecraft is one of the preferred analytical techniques in the search for life beyond the Earth. However, analysis is complicated by unwanted molecular dissociation occurring when sampled native molecules impact the instrument at high velocity. The mechanisms of chemical changes produced in high velocity impacts have been studied experimentally in some cases; however, there are significant experimental limitations to these techniques. Here I present the design, construction, and testing of a new experimental technique to produce high velocity molecular and microparticle collisions under a controlled lab setting using a high-speed spinning rotor. Chapter 1 of this manuscript gives a scientific review of the astrobiological importance of this project for future and current space missions as well as describing previous techniques used to produced hypervelocity impacts and their limitations. Chapter 2 presents the design, construction, calibration, and preliminary experiments of the new technique involving the high-speed rotor. Chapter 3 describes the fabrication of a molecular beam system from the ground up to be coupled with the high-speed rotor. Chapter 4, describes future project directions and presents future experiments using the rotor as a stand-alone instrument. Lastly, the appendix contains the standard operation procedures and design notes regarding the operation of these two instruments.

An experimental and analytical investigation was conducted to gain insight and ultimately predict the dynamic flow response of a fan rotor with inlet flow distortion. Rotor exit total pressure circumferential profiles were accurately predicted using frequency response functions derived from experimental rotor response data. Using these predicted profiles, an initial attempt was made at predicting the dynamic (distorted) stage characteristics of the test machine with promising results. The first step of this research was an experimental investigation to gather unsteady rotor response data. The steady three-dimensional inlet flow of an isolated rotor subjected to inlet distortion was obtained using a five-hole pneumatic prism probe. Exit flow dynamic wake data were obtained using a piggyback steady/unsteady total pressure probe in non-nulling mode. Inlet and exit data were collected for eighteen different combinations of distortion level, operating point, and measurement span. Frequency response functions were generated and then averaged for each operating regime, span, and distortion intensity, assuming the data to be stationary and ergodic. These 'generalized' FRF's were used to predict the rotor exit total pressure profile. These pressure profiles were then used in an initial attempt to predict the dynamic stage (distorted) characteristics of the test machine. Best predictions resulted when an FRF was used for individual operating regimes, defined with respect to rotor blade mean aerodynamic loading. / Master of Science

This thesis involves the development and study of a finite element model of a hermetic, single-vane compressor and a single-phase alternating current induction motor assembled in a common housing. The manufacturer of this unit is experiencing a high scrap rate due to interference during operation between the stator and rotor of the motor. The rotor shaft of the motor is non-typical because of its cantilever design. The finite element model was first subjected to eigenvalue analysis. This revealed that the interference producing displacements were not the result of torque application to the rotor at a frequency close to an eigenvalue of the mechanical system. After a review of the literature and discussions with Electrical Engineering Department faculty possessing extensive motor experience, it was surmised that the physical phenomenon causing the rotor displacement was unbalanced magnetic pull. This phenomenon occurs in the air gap of rotating electric machines due to eccentricity in the air gap. The model was then subjected to simultaneous harmonic force inputs with magnitudes of unity on the rotor and stator surfaces to simulate the presence of unbalanced magnetic pull. It was found that the rotor shaft acts as a cantilever beam while the stator and housing are essentially rigid. The displacements due to these forces were examined and then scaled to develop the motor parameters necessary to produce the radial forces required for stator/rotor interference. Several recommendations were then made regarding possible solutions to the interference problem. / Master of Science

Total pressure non-uniformities in an axial flow compressor can contribute to losses in aerodynamic operability through a reduction in stall margin, pressure rise and mass flow, and to loss of structural integrity through means of high cycle fatigue (HCF). HCF is a primary mechanism of blade failure caused by vibrations at levels exceeding material endurance limits. Previous research has shown total pressure distortions to be the dominant HCF driver in aero engines, and has demonstrated the damaging results of total pressure distortion induced HCF on first stage fan and compressor blade rows [Manwaring et al., 1997]. It is, however, also of interest to know how these distortion patterns propagate through a rotor stage and impact subsequent downstream stages and engine components. With current modeling techniques, total pressure distortion magnitudes can be directly correlated to induced blade vibratory levels and modes. The ability to predict downstream distortion patterns then allows for the inference of blade vibratory response of downstream blades to inlet distortion patterns. Given a total pressure distortion excitation entering a blade row, the nonlinear Volterra series can serve as a predictor of the downstream total pressure profile and therefore provide insight into the potential for HCF in downstream blade rows. This report presents the adaption of nonlinear Volterra theory to the prediction of the transport of non-uniform total pressure distortions through an axial flow compressor. The use of Volterra theory in nonlinear system modeling relies on the knowledge of Volterra kernels, which capture the behavior of a system's response characteristics. Here an empirical method is illustrated for identifying these kernels based on total pressure distortion patterns measured both upstream and downstream of a transonic rotor of modern design. A Volterra model based on these kernels has been applied to the prediction of distortion transfer at new operating points of the same rotor with promising results. Methods for improving Volterra predictions by training Volterra kernels along individual streamlines and normalizing total pressure data sets by physics-based parameters are also investigated. / Master of Science

Die Kenntnis der dynamischen Eigenschaften von Turbomaschinenrotoren sind bei magnetgelagerten Maschinen von entscheidender Bedeutung für den sicheren Betrieb und die Regelung. Besonders der Temperatureinfluss auf die Materialien und die Eigenformen müssen dabei berücksichtigt werden. In diesem Beitrag wird ein MATLAB-Tool vorgestellt mit dem es möglich ist, die Eigenfrequenzen und -formen für magnetgelagerte Turbomaschinen zu berechnen und das Rotormodell für dynamische Simulationen zu erstellen. Es wird auf die zu Grunde liegende Mathematik eingegangen und die Implementierung vorgestellt. Die bisher erreichten Ergebnisse und die Implementierung in ein Simulationsmodell für eine magnetgelagerte Maschine werden gezeigt. / Knowledge of the dynamic properties of turbomachinery rotors is of crucial importance for safe operation and control in machines with magnetic bearings. Especially the temperature influence on the materials and the eigenmodes have to be considered. In this paper, a MATLAB tool is presented with which it is possible to calculate the natural frequencies and shapes for magnetically levitated turbomachinery and to create the rotor model for dynamic simulations. The underlying mathematics is discussed and the implementation is presented. The results achieved so far and the implementation in a simulation model for a machine with magnetic bearings are shown.

Self propulsion modelling is important in order to accurately simulate ships and submarinesusing Computational Fluid Dynamics (CFD). However, fully resolved simulations of hull andpropeller geometries are computationally heavy and time consuming. As such there is a greatinterest in lower order CFD models of propellers. This work investigates three lower ordermodels of a non-cavitating generic submarine propeller (INSEAN E1619) in OpenFOAM. Themodels investigated are Actuator Disk (AD). Rotor Disk (RD) and Actuator Line Model (ALM).The AD model applies a momentum change based on propeller performance coefficients overa disc cell set. The RD uses Blade Element Method (BEM) to calculate a more realistic thrustdistribution over the disk. Finally the ALM applies BEM over seven rotating lines within the cellset disc. The source code to the RD model was modified according to suggestions provided fromearlier studies on the model. The ALM used was originally designed for turbines which wasrectified by changing the force projection vectors in the source code to model propellers instead.There was not enough published data to directly utilize BEM on the E1619 propeller, thus thedata was generated by conducting 2D simulations on every element. The simulations were setup to replicate results provided in earlier works with higher order models in order to compareboth quantitative and qualitative results. It was found the ALM matched the reference databest out of the models tested in this work. The RD was qualitatively similar to the time averageof the ALM fields but numerically inaccurate. The AD results were poor, both quantitativelyand qualitatively.