R&D Journals for 2017 - Volume 33.
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A Computational Tool for Predicting Hybrid Rocket
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Administration
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2017/08/23
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TITLE: A Computational Tool for Predicting Hybrid Rocket Motor Performance
AUTHORS: B. Genevieve, J.F. Pitot de la Beaujardiere, M.J. Brooks
DATE PUBLISHED: August 2017
ABSTRACT: A model is described to aid in the design of hybrid rockets and in the prediction of motor performance, specifically with respect to the University of KwaZulu-Natal’s Phoenix-1A vehicle. The Hybrid Rocket Performance Code (HRPC), programmed in MATLAB, is segregated into two individual models: i) a preliminary motor design code to analyse and design hybrid rocket motors, and ii) a predictive motor performance code to compute the instantaneous motor performance for a targeted burn time. The predictive motor performance code is based on a one-dimensional unsteady gas flow model through the nozzle and, on a zero-dimensional model of the combustion chamber capturing only the filling and emptying dynamics. The zero-dimensional model is linked to a self-pressurising delivery tank model obtained from literatur...
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A Numerical Evaluation of Dunnage Bag Pressure...
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Administration
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2017/07/17
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TITLE: A Numerical Evaluation of Dunnage Bag Pressure Drop Subject to a Single Void Reduction Cycle
AUTHORS: MP Venter, G Venter
DATE PUBLISHED: July 2017
ABSTRACT: Abstract - A method using a simple response model is used to replicate the results of an industry standard certification test for a dunnage bag. The method makes use of numerical optimization tools, standard commercial FEA software and a simple material response model to predict the pressure drop in a dunnage bag caused by material plastic deformation under a compressive cycled load. The results of the response model are evaluated to ensure that the overall response of the model matches that of the measured system. Calibration of the model is done by numerical optimization and the resulting model predicts the pressure drop over one cycle to within one standard deviation of the measured results.
Additional keywords: woven polypropylene fabric, finite element methods, dunnage bags, optimization, plastic deformation.
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Characterisation of Submerged Arc Welding Process
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Administration
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2017/09/05
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TITLE: Characterisation of Submerged Arc Welding Process Using Infrared Imaging Technique
AUTHORS: M.C. Zondi, Y. Tekane, E. Magidimisha, E. Wium, A. Gopal, C. Bemont
DATE PUBLISHED: September 2017
ABSTRACT: Infrared (IR) thermography is a technique used to measure temperature distribution of heat generation in manufacturing processes such as welding. IR
thermography is a non-destructive and non-contact method, which makes it favoured for the arc welding process where interference with the welding process must be avoided. In this study, IR thermography is used to record the temperature history during the submerged arc welding (SAW) process experiment; and to validate the numerical model developed to simulate the said SAW process of a multi-pass circumferential weld on pressure vessel steel. The Flir Short Wave Infrared Radiometer (FSIR) is used during SAW experiments with the ESAB welding unit. The weld pool and the surrounding area are continuously monitored and their temp...
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Design of a Six-Component Side-Wall Balance Usi...
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Administration
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2017/08/25
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TITLE: Design of a Six-Component Side-Wall Balance Using Optical Fibre Sensors
AUTHORS: FF Pieterse, PM Bidgood, NF Vaz
DATE PUBLISHED: August 2017
ABSTRACT: The requirements that a wind tunnel balance need to satisfy have become increasingly stringent. These requirements, as set out by the wind tunnel testing community, include: improved static force accuracy and resolution, increased stiffness, temperature compensation and immunity to electromagnetic interference (EMI). In order to satisfy these requirements, wind tunnel balance design philosophy needs to include alternative strain sensing technologies, alternative materials and alternative manufacturing techniques. This paper outlines the expansion of balance design philosophy to incorporate displacement sensors. This is done on a six-component side wall balance using optical fibre Bragg grating sensors (OFBGs). The balance employs the two-groove optical fibre method. This method has been demonstrated by Pieterse [1], to...
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Development and Testing of a Scale Model Clam...
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Administration
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2017/05/02
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TITLE: Development and Testing of a Scale Model Clamshell Mucker
AUTHORS: ST Moss and TJ Frangakis
DATE PUBLISHED: 27 March 2017
ABSTRACT: The aim of the research was to develop a scaled experimental model of a Clamshell mucker and assess its performance over a range of operating parameters, including bucket closure angular velocity, bucket starting height (translating into increased depth of penetration and bucket fill), bucket angle of attack, and location of the bucket relative to a boundary wall. An experimental rig was developed consisting of a 1/6th scale model opposed bucket arrangement which was actuated by means of hydraulic cylinders. The digging performance was assessed in two materials: a mixture of hard plastic spheres (of diameters 19 and 25 mm), and 13 mm decomposed granite stone aggregate. Flow visualisation tests conducted in the plastic spheres and stone aggregate revealed that particles move initially downwards ahead of the bucket jaws before rising to the in...
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Development of a Combustion Visualisation Hybrid
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Administration
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2017/12/08
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TITLE: Development of a Combustion Visualisation Hybrid Rocket Motor
AUTHORS: R Theba, KL Veale and CP Bemont
DATE PUBLISHED: December 2017
ABSTRACT: The Phoenix Hybrid Sounding Rocket Programme in the University of KwaZulu-Natal’s Mechanical Engineering department has so far only utilised pure paraffin wax and nitrous oxide as the propellant combination in their hybrid rockets. Knowledge of regression rate behaviour is required for the design and performance characterisation of hybrid rocket propulsion systems. The regression rate is the rate at which the fuel recedes in the direction perpendicular to the burning fuel surface. A hybrid slab motor was purpose designed for regression rate analysis. Optimum oxidiser-to-fuel (O/F) ratios obtained from literature and NASA CEA were used with interpolation to define the fuel grain dimensions, and the oxidiser and fuel mass flow rates. The slab motor, with windows for direct regression rate visualisation, was
designed based on these...
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Heat Transfer in a Hot Stamping Process: A Review
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Administration
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2017/10/19
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TITLE: Heat Transfer in a Hot Stamping Process: A Review
AUTHORS: R Muvunzi, DM Dimitrov, S Matope, TM Harms
DATE PUBLISHED: September 2017
ABSTRACT: Heat transfer rate during the hot stamping process affects the resultant quality and production rate of the process. This is because the ability of the tool to transfer heat from the blank affects the resultant tensile strength, temperature distribution and cooling time of the formed part. Research efforts have been made on the design of cooling systems that are aimed towards improving the cooling effectiveness of the blanks thereby improving the quality characteristics of the formed parts. The cooling rate is governed by the interfacial heat transfer coefficient (IHTC). A proper design of hot stamping tools requires knowledge of the heat transfer modes during the hot stamping process. It is important to gain an understanding of the heat transfer scenarios during the process to seek opportunities to reduce the cooling time and imp...
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Investigation of Nozzle Contours in the CSIR Super
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Administration
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2017/06/28
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TITLE: Investigation of Nozzle Contours in the CSIR Supersonic Wind Tunnel
AUTHORS: B Vallabh and BW Skews
DATE PUBLISHED: June 2017
ABSTRACT: The existing nozzle contour profiles of the CSIR’s supersonic or High Speed Wind Tunnel (HSWT) produce weak waves in the test section region, which effectively degrades the air flow quality in the test section. This paper describes a calculation method developed to improve the flow quality in the test section region subject to the HSWT’s limitations. The wind tunnel geometry and constraints were employed in accordance with the Sivells’ nozzle design method and the method of characteristics technique to design the nozzle profiles for the full supersonic Mach number range 11 ≤ MM ≤ 44.5 of the facility. Automatic computation was used for the profile design and a computational method analysed the test section flow characteristics. A boundary layer correction was applied to the profiles to account for the reduction in Mach number due to vis...
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Non-Inertial Forces in Aero-Ballistic Flow and...
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Administration
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2017/10/27
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TITLE: Non-Inertial Forces in Aero-Ballistic Flow and Boundary Layer Equations
AUTHORS: M Combrinck, L Dala, I Lipatov
DATE PUBLISHED: October 2017
ABSTRACT: Abstract: This paper derives the non-inertial terms, also referred to as fictitious forces, for aero-ballistic cases using an Eulerian approach. These cases display unsteady rates of change in acceleration in all six degrees of freedom.Six fictitious forces are identified in the momentum equation. Their origin and nature of these forces are elaborated upon. As shown in previous work, the continuity and energy equations remain invariant. The non-inertial boundary layer equations are derived to determine the effect of fictitious forces in the near-wall region. Through an order of magnitude analysis it was determined that none of the fictitious forces cancels out. It will therefore have an influence on the boundary layer properties.
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Simulation System to Aid in Vehicle Simulator...
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Administration
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2017/03/28
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TITLE: Simulation System to Aid in Vehicle Simulator Design
AUTHORS: T Kader, R Stopforth, G Bright
DATE PUBLISHED: October 2016
ABSTRACT: Vehicle simulators aim to provide the user with a driving experience that replicates the sensations experienced in a real vehicle. An important aspect is the replication of motion cues. The replication of motion cues in the vehicle simulator is limited by platform workspace and the selected position control systems performance. In this work a Matlab/Simulink setup that incorporates the various aspects involved in replication of motion sensations was created. This includes input data scaling, classical washout algorithm and inverse kinematic implementations. By adjusting the input data scaling and classical washout algorithm filter parameters platform motion that adheres to the actuator motion constraints was assured. Therefore this simulation system makes the design process easier since no parameter adjusting was done on the actual motion...
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The National Wind Resource Assessment Project of
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Administration
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2017/12/18
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TITLE: The National Wind Resource Assessment Project of Namibia
AUTHORS: EBJ Siepker and TM Harms
DATE PUBLISHED: December 2017
ABSTRACT: With eleven tall masts equipped with modern wind data acquisition systems, the National Wind Resource Assessment Project (NWRAP) of Namibia is the most comprehensive dedicated wind measurement project undertaken in the country to date. The objective of NWRAP is the provision of high-quality wind data from which reliable wind climates can be identified for relevant parts of the country. The article provides a brief background to the project and proceeds with a description of the development and location thereof, the equipment employed to produce wind data and the processes and methods used to analyse the data. The statistics pertaining to the observed wind climates as identified from wind speed data observed at two elevations at each of the masts are presented in the results section. The statistics include Weibull parameters and mean wind power..
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Upgrading the BMT 120 KS Micro Gas Turbine
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Administration
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2017/06/22
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TITLE: Upgrading the BMT 120 KS Micro Gas Turbine
AUTHORS: F Oppong, SJ van der Spuy, TW von Backström
DATE PUBLISHED: June 2017
ABSTRACT: This study evaluates the performance of the BMT 120 KS micro gas turbine engine. The analysis involves matching the existing engine components as well as redesigned elements using engine characteristic maps. An experimental investigation was conducted to measure the baseline performance parameters of the engine. analytical calculations were used to review the thermodynamic cycle of the engine. A numerical component sensitivity analysis was also used to evaluate the engine’s output. The performance predictions of the engine and its modifications showed good correlation with test results and available engine data.
Additional keywords: Micro gas turbine, Performance, Component matching, Flownex.
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