This work describes the development of a hybrid rocket propulsion system for a reusable sounding rocket, as part of the first phase of the UKZN Phoenix Hybrid Sounding Rocket Programme. The programme objective is to produce a series of low-to-medium altitude sounding rockets to cater for the needs of the African scientific community and local universities, starting with the 10 km apogee Phoenix-1A vehicle. In particular, this dissertation details the development of the Hybrid Rocket Performance Code (HRPC) together with the design, manufacture and testing of Phoenix-1A’s propulsion system. The Phoenix-1A hybrid propulsion system, generally referred to as the hybrid rocket motor (HRM), utilises SASOL 0907 paraffin wax and nitrous oxide as the solid fuel and liquid oxidiser, respectively. The HRPC software tool is based upon a one-dimensional, unsteady flow mathematical model, and is capable of analysing the combustion of a number of propellant combinations to predict overall hybrid rocket motor performance. The code is based on a two-phase (liquid oxidiser and solid fuel) numerical solution and was programmed in MATLAB. HRPC links with the NASA-CEA equilibrium chemistry programme to determine the thermodynamic properties of the combustion products necessary for solving the governing ordinary differential equations, which are derived from first principle gas dynamics. The combustion modelling is coupled to a nitrous oxide tank pressurization and blowdown model obtained from literature to provide a realistic decay in motor performance with burn time. HRPC has been validated against experimental data obtained during hot-fire testing of a laboratory-scale hybrid rocket motor, in addition to predictions made by reported performance modelling data. Development of the Phoenix-1A propulsion system consisted of the manufacture of the solid fuel grain and incorporated finite element and computational fluid dynamics analyses of various components of the system. A novel casting method for the fabrication of the system’s cylindrical single-port paraffin fuel grain is described. Detailed finite element analyses were performed on the combustion chamber casing, injector bulkhead and nozzle retainer to verify structural integrity under worst case loading conditions. In addition, thermal and pressure loading distributions on the motor’s nozzle and its subsequent response were estimated by conducting fluid-structure interaction analyses. A targeted total impulse of 75 kNs for the Phoenix-1A motor was obtained through iterative implementation of the HRPC application. This yielded an optimised propulsion system configuration and motor thrust curve. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.

Aviation is known to have some of the most stringent structural health monitoring standards in the world. An example of this would be the fact that certain bolts in the aircraft assembly must be periodically removed and inspected for fatigue damage. This can be a very costly endeavour: a case in point being the Hercules C130 aircraft, which requires approximately 200 man hours of down-time for the inspection of the bolts that attach the wings to the fuselage. The substitution of TRIP (Transformation Induced Plasticity) steel bolts for the current HSLA steel (AISI 4340) from which the bolts are manufactured, allows the bolt to act in the capacity of load bearing member as well as damage detector. This unique feature is a consequence of the transformation characteristic exhibited by TRIP steels when they are strained: an irreversible change within their microstructure from paramagnetic austenite parent phase to permanent ferromagnetic state occurs in direct proportion to the peak strain. This property allows us to establish a relationship from which the service life of the component can be determined. A prototype of a smart aircraft bolt and washer system has been developed, where the bolt acts as damage detector and the washer effectively examines the health of the bolt by reading the changing magnetic susceptibility of the bolt. This study presents both material development and product development phases of the Smart Aircraft Bolt prototype. A prediction of transformation characteristic due to deformation is carried out using finite element analysis (mechanical model) and a constitutive model (strain induced martensitic transformation kinetics) to predict the best situation for the smart washer. In addition, experimental work is performed in the form of cyclic temperature testing (with and without external loading) and tension-tension fatigue testing. For both sets of experimental testing, two positions of washer placement are tested. A correlation between volume fraction of martensite present and remaining life, is therefore possible. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

In this study a semi-passive pulse thermal loop (PTL) was designed and experimentally validated. It provides improved heat transfer over passive systems such as the loop heat pipe in the moderate to high heat flux range and can be a sustainable alternative to active systems as it does not require an electric pump. This work details the components of the engineering prototype and characterizes their performance through the application of compressible and two-phase flow theory. A custom LabVIEW application was utilized for data acquisition and control. During operation with refrigerant R-134a the system was shown to be robust under a range of heat loads from 100 W to 800 W. Operation was achieved with driving pressure differentials ranging from 3 bar to 12 bar and pulse frequencies ranging from 0.42 Hz to 0.08 Hz. A smaller pressure differential and an increased pulse frequency results in improved heat transfer at the boilers. An evolution of the PTL is proposed that incorporates a novel, ejector-based pump-free refrigeration system. The design of the pulse refrigeration system (PRS) features valves at the outlet of two PTL-like boilers that are alternately actuated to direct pulses of refrigerant through an ejector. This is intended to entrain and raise the pressure of a secondary stream of refrigerant from the cooling loop, thereby replacing the compressor in a conventional vapor-compression cycle. The PRS is therefore characterized by transient flow through the ejector. An experimental prototype has been constructed which is able to operate as a conventional PTL when the cooling section is bypassed, although full operation of the refrigeration loop remains to be demonstrated. The design of the ejector is carried out using a one-dimensional model implemented in MATLAB that accounts for compressibility effects with NIST REFPROP vapor data sub-routines. The model enables the analysis of ejector performance in response to a transient pressure wave at the primary inlet. The high driving pressures provided by the PTL permit operation in a micro-gravity environment with minimal power consumption. Like the PTL, the proposed PRS is therefore well suited to terrestrial and aerospace applications where it could be driven by waste heat from electronics or solar thermal energy. As a novel semi-passive thermal management system, it will require complex control of the valves. Further analysis of the transient thermodynamic cycle is necessary in order to characterize and effect successful operation of the PRS. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2013.

Power line function is to transfer electrical power. Power lines represent a major component in the transport process of electricity and they are subjected to various types of failures. Causes of failure include wind-induced oscillations or Aeolian vibrations. Wind causes transmission line conductors to undergo oscillatory motions which cause failure. To mitigate oscillations of line conductors, Stockbridge dampers are used. It has been observed that dampers are subjected to the same undesirable and destructive effects from vibrations as the conductors they are meant to protect. In the case of a damper, the cyclic bending as well as the friction between its wire cables are caused by vibrations leading to failure. The mathematical model describing the bending stress of the symmetrical Stockbridge damper’s messenger cable near the clamped end is analyzed. The reliability of the mathematical model is assessed using experimental data obtained from the forced response test conducted at the VRTC laboratory at the University of KwaZulu-Natal, Durban. Data from the experiment has been compared with the MatLab model established by the researcher. Due to friction between the wires of the messenger cable, variation of temperature is observed in the messenger cable during operation. Change of temperature of the messenger cable was investigated, as a function of time, at constant velocity and constant displacement. Experimental data were generated during dynamic characteristic tests on Stockbridge dampers and thereafter the prediction of the variation temperature was undertaken. There are various mechanical characteristics of a damper that can be affected with time. To reach the aim of this study, three types of vibration test were conducted on the Stockbridge damper: the fatigue test, the forced vibrations test and the free vibrations test. Tests were conducted on a shaker machine with new and used Stockbridge dampers to determine the remaining life of those dampers by looking at their different mechanical properties. The frequency domain and time spectrum were used to display the results. The fatigue test investigated one of the commonest types of Stockbridge damper failure, namely, loss of the small mass because of sustained high frequency resonance. Ultimately, data correlated well and two mathematical models were developed: one for predicting damage in the life of a Stockbridge damper (based on the highest resonance frequency of the damper), and one for predicting the temperature of the messenger cable. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

In South Africa, a significant amount of electrical energy is used for air conditioning in commercial buildings, on account of the high humidity experienced. Due to its geographical location, the levels of solar irradiation and the demand for air-conditioning of commercial buildings reach maximum levels simultaneously. The South African region daily solar radiation average varies between 4.5 and 6.5 kWh/m2 and when compared to the United States 3.6 kWh/m2 and Europe’s 2.5 kWh/m2 , solar thermal powered cooling technologies has significant potential as this solar irradiation is also available all year around [1]. Utilizing solar energy for an air conditioning system has the advantage that the availability of solar radiation and the need for cooling reach maximum levels simultaneously and proportionally. This type of air conditioning system has an electrical energy saving benefit in light of increasing energy tariffs and the energy crisis currently facing Eskom in South Africa. Solar-assisted Absorption Cooling systems decreases the peak electricity consumption, is less noisy and vibration free, since it does not contain a compressor and this gives a higher reliability, low maintenance and its electricity consumption is approximately four times less (21.8kW versus 5.5kW for 35kW of Cooling) than that of an electric driven chiller containing a mechanical compressor [2]. However, due to the high capital cost of solar powered air-conditioning plants, it is essential that a feasibility analysis be undertaken to indicate and establish a return on capital investment. The main objective of the present study is to investigate and establish the feasibility of a solar-assisted air-conditioning system based on Lithium Bromide and Water (LiBr/H2O) absorption chillers on a medium scale for commercial buildings in terms of energy saving and performance. This study presents the results of the experiment on a solar-assisted air-conditioning facility constructed and installed in October 2009 at Pretoria’s Netcare Moot Hospital. This study has confirmed that a payback period of 13 months can be achieved and the performance parameters of the manufacturer’s specifications for a solar-assisted air conditioning system are exceeded for the South African climate. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

The Loop Heat Pipe (LHP) is a passive, two-phase heat transfer device used, most commonly, for thermal management of aerospace and aeronautical electronic equipment. A unique feature is a porous wick which generates the necessary capillary action required to maintain circulation between the heat source and the heat exchanger. What differentiates LHP devices from traditional heat pipes, which also work through the use of a wick structure, is the constrained locality of the wick, placed solely in the evaporator, which leaves the remainder of the piping throughout the device as hollow. This provides the LHP with a number of advantages, such as the ability to transport heat over long distances, operate in adverse gravitational positions and to tolerate numerous bends in the transport lines. It is also self-priming due to the use of a compensation chamber which passively provides the wick with constant liquid access. These advantages make LHPs popular in aerospace and aeronautical applications, but there is growing interest in their deployment for terrestrial thermal management systems. This research had two aims. Firstly, to create and validate a robust mathematical model of the steady-state operation of an LHP for terrestrial high heat flux electronics. Secondly, to construct an experimental LHP, including a sintered porous wick, which could be used to validate the model and demonstrate the aforementioned heat exchange and gravity resistant characteristics. The porous wick was sintered with properties of 60% porosity, 6.77x10-13 m2 permeability and an average pore radius of 1μm. Ammonia was the chosen working fluid and the LHP functioned as expected during horizontal testing, albeit at higher temperatures than anticipated. For safety reasons the experimental LHP could not be operated past 18 bar, which translated into a maximum saturated vapour temperature of 45°C. The heat load range extended to 60 W, 50 W and 110 W for horizontal, gravity-adverse and gravity-assisted operation respectively. Because of certain simplifying assumptions in the model, the experimental results deviated somewhat from predicted values at low heat loads. Model accuracy improved as the heat load increased. The experimental LHP behaved as expected for 5° and 10° gravity-assisted and gravity-adverse conditions, as well as for transport line variation, in which performance was assessed while the total tubing length was increased from 2.5 m to 4 m. Overall, the construction of the LHP, particularly of the porous wick, its operation and the modeling of the constant conductance mode of operation proved to be successful. The variable conductance mode of operation was not accurately modeled, nor was expected behaviour in the elevation testing encountered, although the reasons for these results are suggested. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.

South Africa is one of the few developing countries able to design and build satellites; however it is reliant on other nations to launch them. This research addresses one of the main technological barriers currently limiting an indigenous launch capacity, namely the development of a locally designed liquid fuel turbopump. The turbopump is designed to function in an engine system for a commercial launch vehicle (CLV) with the capacity to launch 50-500 kg payloads to 500 km sun synchronous orbits (SSO) from a South African launch site. This work focuses on the hydrodynamic design of the impeller, vaneless diffuser and volute for a kerosene (RP-1) fuel pump. The design is based on performance analyses conducted using 1D meanline and quasi-3D multi-stream tube (MST) calculations, executed using PUMPAL and AxCent software respectively. Specific concerns that are dealt with include the suction performance, cavitation mitigation, efficiency and stability of the pump. The design is intended to be a relatively simple solution, appropriate for a South African CLV application. For this reason the pump utilises a single impeller stage without a separate inducer element, limiting the design speed. The pump is designed to run at 14500 rpm while generating 889 m of head at a flowrate of 103.3 kg/s and consuming 1127.8 kW of power. The impeller has six blades with an outer diameter of 186.7 mm and axial length of 84.6 mm. The impeller's high speed and power requirement make full scale testing in a laboratory impractical. As testing will be a critical component in the University of KwaZulu-Natal's turbopump research program, this work also addresses the scaling down of the impeller for testing. The revised performance and base dimensions of the scaled impeller are determined using the Buckingham-Pi based scaling rules. The test impeller is designed to run at 5000 rpm with a geometric reduction of 20%, using water as the testing medium. This gives an outer diameter of 147.8 mm and an axial length of 69.9 mm. At its design point the test impeller generates a total dynamic headrise of 67.7 m at a flow rate of 18 kg/s, with a power requirement of 15 kW. A method for maintaining a similar operating characteristic to the full scale design is proposed, whereby the scaled impeller's blade angle distribution is modified to maintain a similar diffusion characteristic and blade loading profile. This technique is validated by MST analysis for off-design conditions with respect to both speed and flowrate. / M.Sc.Eng. University of KwaZulu-Natal, Durban 2013.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In the design or modification of internal combustion (IC) engine components, the South African Automotive industry has always relied on either design by mother companies or quasi-empirical design methods. These methods have restricted the performance and reliability of local designs. A personal computer based model of four stroke engine operation has been developed as a rapid and cost-effective aid to users who wish to determine the performance of an engine with reasonable accuracy before dynamometer testing is possible. This model consists of a thermodynamic model of combustion and gas exchange linked to a manifold flow model. Accompanying this is a simulation of valve flow and a cam dynamic model, enabling full assessment of the optimum cam profiles and valve angles for various automotive engine configurations. The accuracy of these models has been verified by comparison with a set of engine dynamometer tests. The models have also been used with great success in local and international development projects in conjunction with local automotive manufacturers. In particular, two engine upgrade projects have been successfully completed, in which the program was used to aid the design of inlet manifolds, the selection of camshafts, and the selection of compression ratios. / AFRIKAANSE OPSOMMING: In die ontwerp of modifikasie van binnebrandenjin-komponente het die Suid-Afrikaanse Motorbedryf gewoonlik staatgemaak op óf die ontwerpe van die moedermaatskappy óf is van quasi-empiriese ontwerp metodes gebruik gemaak. Hierdie metodes het die werkverrigting en uithouvermoë van plaaslike ontwerpe beperk. 'n Rekenaar model wat die werking van 'n vierslagenjin moduleer, is ontwikkel as 'n vinnige en koste effektiewe hulpmiddel vir ontwerpers om 'n redelike akkurate voorspelling van enjin werkverrigting te verkry, voordat dynamomotor toetswerk moontlik is. Die model bestaan uit 'n termodinamise model vir ontbranding en die gas uitruilproses, gekoppel aan 'n spruitstuk vloeimodel. Die model word saam met 'n simulasie van klepvloei en 'n nok dinamiese model gebruik, wat toelaat dat 'n goeie raming van die optimum nokprofiele en klephoeke gemaak kan word vir verskeie automobielenjin konfigurasies. Die akuraatheid van hierdie modelle is bevestig deur die vergelyking van simulasie resultate met 'n omvangreike stel enjin dynamomotor toetse. Die modelle is ook met groot sukses in verskeie plaaslike en internasionale ontwikkelingsprojekte, in samewerking met die plaaslike motorbedryf, gebruik. In besonder is twee enjinontwikkelingsprojekte suksesvol voltooi, waarin die simulasie program gebruik is om die ontwerp van die inlaat spruitstuk, die keuse van nokasse en die keuse van drukverhouding te vergemaklik.

The mass customisation manufacturing (MCM) paradigm has created a problem in manufacturing control implementation, as each individual customer has the potential to disrupt the operations of production. The aim of this study was to characterise the manufacturing effects of customers’ decisions in product configuration, in order to research steady state control requirements and work-in-process distributions for effective MCM operations. A research method involving both analytic and empirical reasoning was used in characterising the distributed control environment of manufacturing systems involved in MCM. Sequences of job arrivals into each manufacturing system, due to customers’ decisions in product configuration, were analysed as Bernoulli processes. A customer model based on this analysis captured the correlation in product configuration decisions over time. Closed form analytic models were developed from first principles, which described the steady state behaviour of flow controlled manufacturing systems under generalised clearing policy and uncorrelated job arrival sequences. Empirical analysis of data sets achieved through discrete event simulation was used in adjusting the models to account for more complex cases involving multiple job types and varying correlation. Characteristic response surfaces were shown to exist over the domains of manufacturing system load and job arrival sequence correlation. A novel manufacturing flow control method, termed biased minimum feedback (BMF) was developed. BMF was shown to posses the capability to distribute work-in-process within the entire manufacturing facility through work-in-process regulation at each manufacturing system, so as to increase the performance of downstream assembly stations fed from parallel upstream processing stations. A case study in the production of a configurable product was used in presenting an application for the models and methods developed during this research. The models were shown to be useful in predicting steady state control requirements to increase manufacturing performance. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2013.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / This thesis describes the development of a vacuum arc thruster (VAT) to be used as a potential low mass (< 500 g), low power (< 5–10W) propulsion system for nanosatellites. The thruster uses a high voltage capacitive circuit to initiate and power the arc process with a 400 ns high current (150–800A) pulse. A one-dimensional steady state analyticalmodel describing the cathode region of the vacuum arc was developed. The model made use of mass and energy balances at the sheath region and cathode surface respectively to predict key quantities such as thrust, ion velocity, ion-to-arc current ratio and erosion rate. Predicted results were shown to be within the limits of reported literature (∼63 μN/A, 26.12 km/s, 0.077 and 110 μg/C respectively). A sensitivity analysis of the analytical model found that a high electric field in the cathode region impedes and decelerates ion flow, which is used for thrust. This was confirmed experimentally for thrust values at arc voltages greater than 2000 V. Both direct and indirect means of measuring thrust were achieved by using a deflecting cantilever beam and an ion collector system, respectively. The transient response of the cantilever beam to impulsive thrust was analytically modeled, whilst the ion current was found by measuring the current induced on a plate subject to ion bombardment. Knowledge of the ion current density distribution was successfully used to approximate the effective normal thrust vector. Direct and indirect thrust levels were roughly 140 and 82 μN/A of average arc current, respectively. Measured thrust was found to be higher than predicted thrust due to thrust contributions fromthe ablation of Teflon insulation. The discrepancy is also due to the uncertainty in quantifying free parameters in the analytical model such as the fraction of generated ions flowing away from the cathode region. The thrust-topower ratio, specific impulse and efficiency of the vacuum arc thruster at an average arc current of 200 A was measured to be 0.6 μN/W, 160 s and 0.05 %, respectively. A thruster performance analysis and specification showed that the VAT is capable of achieving specific orbital and slew manoeuvres within a constant 5–10 W average power. It was concluded that thruster performance could be improved by using a two-stage arc circuit consisting of a high voltage, low current, short pulse trigger and a low voltage, high current, long pulse driver.