Journal Articles

Permanent URI for this collection

http://hdl.handle.net/10204/11487

Browse

Browsing Journal Articles by browse.metadata.impactarea "Aeronautic Systems"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    An aerodynamic CFD analysis of inlet swirl in a micro-gas turbine combustor
    (2023-07) Meyers, Bronwyn C; Grobler, Jan-Hendrik; Snedden, GC
    A combustor was designed for a 200N micro-gas turbine [1, 2] using the NREC preliminary combustor design method [1, 2, 3]. During the design process, there are various aspects where there are no definitive methodologies for specifying the design detail, such as the design of the hole-sets, and multiple options can be derived that can satisfy the required mass flow split and pressure drop for a particular hole-set.
  • No Thumbnail Available
    Item
    Fatigue properties of additively manufactured tool steel
    (2024-09) Johnston, Charmaine M; Tshabalala, Lerato C; Davids, M
    Tool steel is routinely used by the Experimental Aerodynamics group at the Council for Scientific and Industrial Research (CSIR), South Africa, to manufacture critical components for wind tunnel testing. This steel is known for its high strength properties in both tension and compression, and has a good combination of machinability, ductility, and fracture toughness. The emergence of the Additive Manufacturing (AM) technology provides an alternative to traditional manufacturing procedures in the production of wind tunnel model parts and instrumentation; however, use of the AM technology requires knowledge, inter alia, of the fatigue characteristics of the AM materials. Test specimens were manufactured from tool steel powder using the Selective Laser Melting (SLM) technology and subjected to fatigue and tensile tests. The thermal treatments were used for stress relieving and aging the additively manufactured part; the processes used in this project were found to have an adverse effect on the properties of the material.
  • Thumbnail Image
    Item
    Feasibility of rotor fault detection from a fluid dynamics perspective
    (2020-05) Robbins, SL; Heyns, PS; Heyns, Johan A
    The majority of condition monitoring techniques employed today consider the acquisitioning and analysis of structural responses as a means of profiling machine condition and performing fault detection. Modern research and newer technologies are driving towards non-contact and non-invasive methods for better machine characterisation. Yet current literature lacks investigations into the monitoring and detection of anomalous conditions using fluid dynamic behaviour. If one considers unshrouded rotors which are exposed to a full field of fluid interaction such as helicopter rotors and wind turbines amongst others, such an approach could potentially be beneficial. In this work, time-dependent fluid dynamic data is numerically simulated around a helicopter tail rotor blade using URANS CFD with the Open FOAM software package. Pressures are probed at locations in the field of the rotor and compared to results attained in an experimental investigation where good correlation is seen between the results. A blade is modelled with a seeded fault in the form of a single blade out of plane by 4°. Comparisons are drawn between the blade in its ‘healthy’ and ‘faulty’ configurations. It is observed that the fault can be detected by deviations in the amplitudes of the pressure signals for a single revolution at the probed locations in the field. These deviations manifest as increases in the frequency spectrum at frequencies equivalent to the rotational rate (1 per revolution frequencies). The results described are assessed for their fidelity when the pressure is probed at different locations in the domain of the rotor. Deviations in the pressure profiles over the surface of the blades are also seen for the asymmetric rotor configuration, but may prove too sensitive for practical application.
  • No Thumbnail Available
    Item
    Thermal aging of additively manufactured maraging steel
    (2024-12) Davids, Micaela; Johnston, Charmaine M; Tshabalala, Lerato C
    The mechanical properties of Additively Manufactured M300 Maraging Steel were tested after two thermal treatments. It was found that the stress-relief process resulted in tensile strength comparable to the powder specification, but low ductility compared to the specifications, whilst the addition of an aging process resulted in substandard tensile strength and extreme brittleness. The results of a hardness test and the tensile properties achieved suggest that the material was embrittled by both thermal processes. The samples were inspected using an Optical Microscope (OM) after testing.
  • Thumbnail Image
    Item
    Two dimensional vortex shedding from a rotating cluster of cylinders
    (2023-09) Ndebele, Bright B; Gledhill, IMA
    The dynamics of two-dimensional vortex shedding from a rotating cluster of three cylinders was investigated using Computational Fluid Dynamics (CFD) and Dynamic Mode Decomposition (DMD). The cluster was formed from three circles with equal diameters in mutual contact and allowed to rotate about an axis passing through the cluster centroid. While immersed in an incompressible fluid with Reynolds number of 100, the cluster was allowed to rotate at non-dimensionalised rotation rates (Ω) between 0 and 1. The rotation rates were non-dimensionalised using the free-stream velocity and the cluster characteristic diameter, the latter being equal to the diameter of the circle circumscribing the cluster. CFD simulations were performed using StarCCM+. Dynamic Mode Decomposition based on the two-dimensional vorticity field was used to decompose the field into its fundamental mode-shapes. It was then possible to relate the mode-shapes to lift and drag. Transverse and longitudinal mode-shapes corresponded to lift and drag, respectively. Lift–drag polars showed a more complex pattern dependent on Ω in which the flow fields could be classified into three regimes: Ω less than 0.3, greater than 0.5, and between 0.3 and 0.5. In general, the polars formed open curves in contrast to those of static cylinders, which were closed. However, some cases, such as Ω = 0.01, 0.22, and 0.28, formed closed curves. Whether a lift-drag polar was closed or open was deduced to be determined by the ratio of Strouhal numbers calculated using lift and drag time series, with closed curves forming when the ratio is an integer.
  • Thumbnail Image
    Item
    Wind tunnel testing - A career at high speed - while standing still! 1990-2022
    (2022-11) Morelli, Mauro F
    This item is the John Weston Memorial Lecture and comprises a conference presentation providing details on a career involving wind tunnel testing (1990-2022).