Browsing by Author "Brooks, Michael John."

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Analysis of potential small satellite launch operations at the Denel Overberg test range.
(2022) Arunakirinathar, Aravind.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
One of the primary objectives of the South African First Integrated Rocket Engine (SAFFIRE) programme of UKZN’s Aerospace System Research Group (ASReG) is to develop the capacity for orbital injection missions to Low Earth Orbits (LEOs) from South Africa. The most likely launch site for these missions is the Denel Overberg Test Range (OTR) near Cape Agulhas in the Western Cape. In order to determine the suitability of OTR as a launch site, it is imperative to gain an understanding of the performance, mechanics and structural loads of a vehicle entering orbit. The goal of this dissertation is to analyse the performance of a variety of modern two-stage launch vehicles as they travel along orbital injection trajectories into LEOs from OTR. This study considers solutions for the ascent-to-orbit trajectory for various launch vehicles. The primary method was to utilise trajectory optimisation methods and this was achieved by developing an optimal control solver, which makes use of direct Hermite-Simpson collocation methods, and a sequential quadratic programming solver. In order to improve the robustness and speed of the solver, formulae for the first order analytical derivative information of direct Hermite-Simpson collocation were developed. The optimal control solver was then validated using various linear and nonlinear examples from literature. The optimal control solver was used to analyse the performance of various hypothetical missions conducted by the following established launch vehicles: Rocket Lab’s Electron, SpaceX’s Falcon 1, SpaceX’s Falcon 9, and ASReG’s proposed small satellite launch vehicle, CLV. As a baseline comparison, all vehicles were launched from OTR into various LEOs. The payloads, trajectories, control histories and structural loads of these vehicles for injection were investigated. Finally, the effect of perigee altitude, inclination, and eccentricity of orbits on the extracted results was studied. The payload performance of the launch vehicles considered were relatively similar to that provided by each vehicle’s corresponding payload user guide. On all missions, the altitude of the Electron, Falcon 9 and CLV would constantly increase with range, however the Falcon 1 would tend to rise, dip, and then rise once more on missions to orbits with a perigee altitude of 200 km. Such trajectories are referred to as lofted trajectories and are common among vehicles with a low upper stage thrust to weight ratio (Patton and Hopkins, 2006), such as the Falcon 1. The tangent yaw and pitch of the thrust direction was highly linear for all analysed missions. This result allows for a reasonable control law which can be used to determine trajectory solutions using indirect optimal control methods. This study demonstrates the viability of the Denel Overberg Test Range as a competitive base of operation for space launch missions to LEO.
Broadband solar radiometric measurements in the greater Durban area.
(2011) Kunene, Khulisile.; Brooks, Michael John.; Roberts, Lancian Willett.
This work comprises a radiometric study of Durban‟s solar resource, utilizing data from the Howard College campus of the University of KwaZulu-Natal (UKZN), and the Solar Thermal Applications Research Laboratory (STARlab) at Mangosuthu University of Technology (MUT), located 17 km away. The study has three aims: first to establish a solar radiometric monitoring network for the greater Durban area, comprising the UKZN Howard College and Westville stations, and the STARlab facility at MUT. The UKZN Westville station is under refurbishment and should be operational by the end of 2011. Data from this station are not included in the study. The instrumentation and acquisition software in use at Howard College and STARlab are described. The stations record global horizontal irradiance (GHI), direct normal irradiance (DNI) and diffuse horizontal irradiance (DHI), measured by an unshaded pyranometer, a normal incidence pyrheliometer and a pyranometer shaded with a stationary band respectively. Second, to test a number of existing radiometric models against measured data gathered at the stations. Radiometric models assist in estimating missing components of radiation at stations that do not measure all three components separately, for reasons of cost. The models investigated included Erbs et al. (1982), Orgill and Hollands (1977), Reindl et al. (1990), Boland et al. (2001), and Skartveit and Olseth (1987) and correction models by Drummond et al. (1956), Le Baron et al. (1990), Batlles et al. (1995), and Muneer and Zhang (2000) to correct the shadow band effect. Third, to compare data from the two operational stations and to investigate potential spatial differences in sun strength arising from micro-climate effects in the greater Durban area. This takes the form of a statistical analysis of the differences in radiometric data recorded simultaneously at the UKZN and STARlab stations. The study found that the recorded difference in GHI over one year was 0.72%, which lies within the instrument measurement accuracy. Therefore no measurable radiometric differences due to microclimate could be detected and, for the period in which data were collected, measurements from Howard College could be used to estimate irradiance patterns for MUT, and vice versa.
Closed-loop throttle control of a hybrid rocket motor.
(2018) Velthuysen, Timothy Johnathan.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
Hybrid rocket motors produce thrust by reacting a solid fuel with a liquid oxidizer inside a combustion chamber. This approach has certain advantages over conventional solid propellant rockets including improved safety and the potential for thrust control, while also being less expensive than liquid propellant engines. Liquefying hybrid fuels, such as paraffin wax, regress at a faster rate than the conventional solid fuels like HTPB that are dominated by vaporization at the solid-gas interface. Non-classical theory is still in its infancy, however, and more work is required to validate performance models experimentally, especially where throttling of the oxidizer mass flowrate is incorporated. While hybrid motor throttlabilty remains a subject of considerable interest, there has been little investigation of throttling in motors that use high regression rate, liquefying fuels such as paraffin wax. This study proposes a closed-loop thrust control scheme for paraffin wax/nitrous oxide hybrid rocket motors using a low-cost ball valve as the controlling hardware element. There are a number of advantages to throttling hybrid rocket motors but the most important is to enforce a constant thrust curve throughout the burn. A test facility and laboratory scale hybrid rocket motor utilizing paraffin wax as fuel and nitrous oxide as oxidiser were used for experimental testing. Using a mathematical model of a laboratory-scale hybrid rocket motor, the controller constants for a PID controller were obtained and tested through experimental testing. Open-loop testing was first done in order to determine the control authority of the ball valve over the oxidiser mass flowrate, as well as characterize the oxidiser mass flowrate in relation to each valve angle value. Closed-loop testing was undertaken to verify and refine the controller constants obtained via the laboratory-scale model. The tests prompted a redesign of the injector and additions to the LabVIEW™ controller regime. Using results from the open-loop tests a feed-forward lookup table was developed to allow for the controller to move to a specified angle quickly and thereby remove nonlinearities present in flow control using ball valves. Three successful closed-loop tests were done where the controller causes the thrust of the motor to track a predetermined thrust or chamber pressure set point with a reasonable degree of accuracy. The set-point profile of the first test was a constant thrust throughout the burn while the second test had a ramp set-point profile. The final test used chamber pressure as the feedback variable and had a step-down set-point profile. This study demonstrates that thrust control can be exercised over a paraffin wax/nitrous oxide hybrid rocket motor, using a low-cost ball valve as the control element to modulate the oxidiser mass flowrate.
Clustering analysis for classification and forecasting of solar irradiance in Durban, South Africa.
(2017) Govender, Paulene.; Matthews, Alan Peter.; Brooks, Michael John.
Classification and forecasting of solar irradiance patterns has become increasingly important for operating and managing grid-connected solar power plants. A powerful approach for classification of irradiance patterns is by clustering of daily profiles, where a profile is defined as irradiance as a function of time. Classification is useful for forecasting because if the class of a day can be successfully forecast, then the irradiance profile of that day will share the general pattern of the class. In Durban, South Africa (29.871 °S; 30.977 °E), beam and diffuse irradiance profiles were recorded over a one-year period and normalized to a clear sky model to reduce the effect of seasonality, from which several variables were derived, namely minute-resolution beam, hourly-resolution beam and diffuse, and hourly-resolution beam variability. To these variables, individually and in combination, k-means clustering was applied, and beam irradiance was found to be the one that best distinguishes between sky conditions. In particular, clustering of hourly-resolution beam irradiance produced four classes with diurnal patterns characterized as sunny all day, cloudy all day, sunny morning-cloudy afternoon, and cloudy morning-sunny afternoon. These classes were then used to forecast beam and diffuse irradiance for the day ahead, in association with cloud cover forecasts from Numerical Weather Prediction (NWP) output. Two forecasting methods were investigated. The first used k-means clustering on predicted daily cloud cover percentage profiles from the NWP, which was a novel aspect of this research. The second used a rule whereby predicted cloud cover profiles were classified according to whether their averages in the morning and afternoon were above or below 50%. From both methods, four classes were obtained that had diurnal patterns associated with the irradiance classes, and these were used to forecast the irradiance class for the day ahead. The two methods had a comparable success rate of about 65%. In addition, hour-ahead forecasts of beam and diffuse irradiance were performed by using the mean profile of the forecast irradiance class to extrapolate from the current measured value to the next hour. The method showed an average improvement of about 22% for beam and diffuse irradiance over persistence forecasts. These results suggest that classification of predicted cloud cover and irradiance profiles are potentially useful for development of class-specific, multi-hour irradiance forecast models.
Computational fluid dynamic modelling of baffled open volumetric receiver operation.
(2020) Jo Mathew, Mathew.; Pitot De La Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
An Open Volumetric Receiver (OVR) is a type of solar energy receiver that is able to heat atmospheric air volumetrically via a porous absorber exposed to concentrated solar radiation, through which the air flows. OVRs have the potential to attain higher operational efficiency than tubular or cavity type receivers, and they have been extensively investigated for use in concentrating solar power (CSP) plants. In CSP applications, the hot air leaving the OVR is typically passed through a heat recovery steam generator to generate steam for the plant’s steam turbine, after which it is returned to the OVR. Here, it is injected back into the atmosphere near the receiver inlet where some of the warm return air is re-entrained along with fresh air entering it. The amount of air that is re-entrained into the OVR is quantified by the air return ratio, and the higher this ratio, the lower the energy lost from the receiver. One of the factors limiting the operational efficiency of OVRs is fairly poor ARR performance, in the region of 50 % for state-of-the-art OVR designs. This research aims to evaluate the effectiveness of the addition of the vertical air flow baffles in improving the air re-entrained performance of an OVR. The evaluation was carried out numerically using Ansys Fluent Computational Fluid Dynamics (CFD) modelling software. Prior to the core investigation, cold and hot flow validation studies were conducted with respect to a generalized porous absorber and an arrangement of HiTRec-II OVR modules. The corresponding CFD models were successfully validated against experimental data and the methodology used to model the HiTRec-II modules was used to model an arrangement of SolAir OVR modules and modified arrangements incorporating air flow baffles of varying lengths. OVR air re-entrainment performance was evaluated in terms of the module air outlet temperature. The performance of the SolAir modules was evaluated when exposed to wind at varying magnitude and direction. The results from this study were used as a baseline against which the performance predicted for the SolAir modules modified with baffles (of different lengths) could be compared. A comparison of the results indicates that there is a clear increase in mean module air outlet temperature, when air flow baffles are incorporated with the lowest being 2.5 % and highest being 60.7 % increase in the temperature among the wind conditions and baffle lengths investigated for the study. The increase in the temperature also implies an improvement in air re-entrainment and thus OVR efficiency. The results also suggested the existence of an optimal baffle length for the receiver modules, beyond which the air outlet temperature drops and the OVR efficiency deteriorates.
The design and analysis of a kerosene turbopump for a South African commercial launch vehicle.
(2013) Smyth, Jonathan.; Brooks, Michael John.; Smith, Graham Douglas James.; Bindon, Jeffrey Peter.; Snedden, Glen Campbell.
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.
Design and analysis of a multi-trailer system for the Durban container terminal.
(2018) Govender, Theo.; Brooks, Michael John.; Bemont, Clinton Pierre.
Multi-trailer systems (MTS) allow for the transportation of multiple shipping containers in a single movement as opposed to the conventional trailer systems often used within a port terminal environment. The adoption of MTSs creates an opportunity for container terminal operators to reduce the operational costs associated with container movements between the container vessel and stacking areas during the vessel loading and unloading operations while maintaining, and in certain cases improving, the port’s quayside productivity. A reduction in operational costs can potentially result in lower tariffs levied to container vessel operators, improving the competitiveness of a port. While MTSs have been in existence for many years and have been successfully implemented in many international port container terminals, the influence of this type of trailer on the operational costs of the waterside horizontal-transport system and on the quayside productivity within South African ports has not been investigated or demonstrated to date. This study set out to determine the influence which an indigenously designed MTS has on the abovementioned factors at South Africa’s largest container port, the Durban Container Terminal. Discrete event simulations were used to benchmark the current performance of the container movement operations at Pier One of the Durban Container Terminal using the existing tractor-trailer units (TTUs). The performance of the operations was then analysed for the scenario of replacing the TTUs with MTSs that have twice the container carrying capacity. The results showed that nine MTSs can replace the existing fleet of fifteen TTUs without compromising on the quayside performance for the vessel unloading operations, which leads to a 25% reduction in operational costs. A reduction in labour costs accounts for 88% of the saving. Use of MTSs for the vessel loading operations showed minimal benefit and the performance using the existing TTUs for this operation can be considered equivalent. The results imply that an MTS configuration with the ability to uncouple the individual trailers in the set for use as TTUs was required. This lead to the selection of a semi-trailer lead MTS configuration incorporating the use of a converter dolly for the indigenous design conducted here. The indigenous MTS design consisted of two identical semi-trailers connected using a converter dolly, allowing for interchangeability in the MTS set and for use of the semi-trailers as TTUs. The terminal’s existing semi-trailers could have been used with the converter dolly designed in this study for the MTS, however an improved semi-trailer design with regards to mass, cost and manoeuvrability has been provided. The new semi-trailer design was shown to have a 21.4% lower tare mass and a 14.1% lower product manufacturing cost over the existing design. For the MTS configuration, up to an 11.6% improvement in manoeuvrability is expected when using the newly designed semi-trailer.
Design and development of the Phoenix-1B hybrid rocket.
(2017) Balmogim, Udil.; Brooks, Michael John.; Veale, Kirsty Lynn.; De La Beaujardiere, Jean-Francois Pitot.
In August 2014, South Africa’s first university-based hybrid rocket, Phoenix-1A, was launched at the Overberg Test Range near Cape Agulhas. The vehicle suffered nozzle and parachute failures during flight which, together with a reduced oxidiser load, reduced the nominal design apogee of 10 km to 2.5 km. The aim of this research was to improve on the design and performance of the prototype demonstrator and thereby develop a workhorse hybrid sounding rocket, named Phoenix-1B, to serve as a reliable platform for future hybrid rocket research at the University of KwaZulu-Natal (UKZN). Analysis of Phoenix-1A shortcomings served as the starting point for the new design, which utilises a paraffin wax and nitrous oxide propellant combination. The focus of this research was the propulsion system, with specific attention being paid to the nozzle and injector designs. In addition, an aerodynamic study was applied to the 1 m long ¾ parabolic nose cone and four tapered swept fins. Final design of the aluminium oxidiser tank and combustion chamber bulkheads incorporated finite element analyses to ensure an operational safety factor greater than 1.5. The oxidiser tank and combustion chamber assemblies were pressure tested to 80 and 60 bars respectively. A key output of the present work is an analysis of the effect of aluminium loading in the paraffin wax fuel grain, which indicated a potential rocket mass reduction of 23 kg when transitioning from a pure paraffin grain to one containing 40% aluminium by mass. The analysis also indicated that combustion temperature rises with aluminium loading, increasing from 3300 K for pure paraffin to 3600 K for 40% aluminised fuel. Consequently, an iterative transient thermo-structural analysis was conducted on the nozzle, resulting in an optimised design able to sustain the higher operating temperatures as well as mitigate the risk of failure as seen with Phoenix-1A. The final manufactured composite nozzle has a throat diameter of 32 mm, an expansion ratio of 6.38, and a length of 156 mm. The nozzle has a steel casing which provides structural support to the silica phenolic insulation and graphite throat insert. A two phase CFD analysis, coupled with analytical mass flow rate models, was used to configure the axial injector and reduce the potential for combustion instabilities associated with the nitrous oxide flow. The Phoenix-1B motor has a design thrust of 5 kN to propel the fully loaded vehicle, with a mass of 70 kg, a length of 4.3 m and a diameter of 164 mm, to an altitude of 16 km.
Design and performance simulation of a hybrid sounding rocket.
(2012) Chowdhury, Seffat Mohammad.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Roberts, Lancian Willett.
Sounding rockets find applications in multiple fields of scientific research including meteorology, astronomy and microgravity. Indigenous sounding rocket technologies are absent on the African continent despite a potential market in the local aerospace industries. The UKZN Phoenix Sounding Rocket Programme was initiated to fill this void by developing inexpensive medium altitude sounding rocket modeling, design and manufacturing capacities. This dissertation describes the development of the Hybrid Rocket Performance Simulator (HYROPS) software tool and its application towards the structural design of the reusable, 10 km apogee capable Phoenix-1A hybrid sounding rocket, as part of the UKZN Phoenix programme. HYROPS is an integrated 6–Degree of Freedom (6-DOF) flight performance predictor for atmospheric and near-Earth spaceflight, geared towards single-staged and multi-staged hybrid sounding rockets. HYROPS is based on a generic kinematics and Newtonian dynamics core. Integrated with these are numerical methods for solving differential equations, Monte Carlo uncertainty modeling, genetic-algorithm driven design optimization, analytical vehicle structural modeling, a spherical, rotating geodetic model and a standard atmospheric model, forming a software framework for sounding rocket optimization and flight performance prediction. This framework was implemented within a graphical user interface, aiming for rapid input of model parameters, intuitive results visualization and efficient data handling. The HYROPS software was validated using flight data from various existing sounding rocket configurations and found satisfactory over a range of input conditions. An iterative process was employed in the aerostructural design of the 1 kg payload capable Phoenix-1A vehicle and CFD and FEA numerical techniques were used to verify its aerodynamic and thermo-structural performance. The design and integration of the Phoenix-1A‟s hybrid power-plant and onboard electromechanical systems for recovery parachute deployment and motor oxidizer flow control are also discussed. It was noted that use of HYROPS in the design loop led to improved materials selection and vehicle structural design processes. It was also found that a combination of suitable mathematical techniques, design know-how, human-interaction and numerical computational power are effective in overcoming the many coupled technical challenges present in the engineering of hybrid sounding rockets.
Development of a composite oxidiser tank for the Phoenix-1B Mk. II hybrid rocket.
(2020) Williams, Dylan Roy.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
Abstract available in PDF.
Development of a comprehensive energy model to simulate the energy efficiency of a battery electric vehicle to allow for prototype design optimisation and validation.
(2017) Woods, Matthew Allan Ray.; Bemont, Clinton Pierre.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
This dissertation describes the development of an energy model of a battery electric vehicle (BEV) to assist designers in evaluating the impact of overall energy efficiency on vehicle performance. Energy efficiency is a crucial metric for BEVs as it defines the driving range of the vehicle and optimises the limited amount of energy available from the on-board battery pack, typically the most expensive component of the vehicle. Energy modelling also provides other useful information to the designer, such as the range of the vehicle according to legislative drive cycles and the maximum torque required from the motor. An accurate, fast and efficient model is therefore required to simulate BEVs in the early stages of design and for prototype validation. An extensive investigation into BEV modelling and the mechanisms of energy losses within BEVs was conducted. Existing literature was studied to characterise the effect of operating conditions on the efficiency of each mechanism, as well as investigating existing modelling techniques used to simulate each energy loss. A complete vehicle model was built by considering multiple domain modelling methods and the flow of energy between components in both mechanical and electrical domains. Simscape™, a MathWorks MATLAB™ tool, was used to build a physics based, forward facing model comprising a combination of custom coded blocks representing the flow of energy from the battery pack to the wheels. The acceleration and speed response of the vehicle was determined over a selected drive cycle, based on vehicle parameters. The model is applicable to normal driving conditions where the power of the motor does not exceed its continuous rating. The model relies on datasheet or non-proprietary parameters. These parameters can be changed depending on the architecture of the BEV and the exact components used, providing model flexibility. The primary model input is a drive cycle and the primary model output is range as well as the dynamic response of other metrics such as battery voltage and motor torque. The energy loss mechanisms are then assessed qualitatively and quantitatively to allow vehicle designers to determine effective strategies to increase the overall energy efficiency of the vehicle. The Mamba BEV, a small, high-power, commercially viable electric vehicle with a 21 kWh lithium-ion battery was simulated using the developed model. As the author was involved in the design and development of the vehicle, required vehicle parameters were easily obtained from manufacturers. The range of the vehicle was determined using the World-Harmonised Light Duty Vehicles Test Procedure and provided an estimated range of 285.3 km for the standard cycle and 420.8 km for the city cycle.
Development of a high concentration solar flux mapping system.
(2018) Van Bakel, Brandon Luke.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
The Group for Solar Energy Thermodynamics (GSET) is in the process of commissioning the Solar Energy Research Amplified Flux Facility (SERAFF), which is South Africa’s first solar furnace facility. SERAFF is situated at the University of KwaZulu-Natal’s Howard College campus and assumes an on-axis optical configuration, comprising a 9 m2 non-focusing heliostat reflector, a 3 m diameter paraboloidal dish concentrator and a test article platform. The facility was designed to aid research in the fields of high temperature materials testing, concentrating solar energy and solar thermochemistry. The concentrated radiative energy output of a solar furnace establishes the energy input to prototype receivers, reactors or materials that aim to be tested using the facility. The challenge is compounded by the temporal and spatial variation of SERAFF’s radiative energy output, influenced by weather-related and geometric factors. In this study, an indirect spatial flux mapping system is developed to characterise SERAFF’s spatial radiative energy output. SERAFF’s theoretical spatial radiative energy output is estimated through Monte Carlo ray-tracing techniques to provide benchmark performance parameters including total thermal power output, peak concentration ratio and focal spot size. The indirect system uses optical measurement techniques, in which spatial solar flux is measured via diffuse reflection off a Lambertian target using a digital CMOS camera through a neutral density filter and lens. Pixel intensities are calibrated against reference measurements acquired from a circular-foil Gardon gauge heat flux transducer. The calibrated CMOS camera can be used to measure values of radiative flux, incident at the focal plane from 0 kW/m2 - 468.19 kW/m2. Measurements were restricted to a brief testing period and are not representative of SERAFF’s peak operating conditions. Spatial flux measurements indicated a thermal power output of 3.83 kW, with a corresponding peak solar flux of 227.8 kW/m2 within a focal diameter of 250 mm. The study demonstrated successful integration of an indirect spatial flux mapping system into the SERAFF solar furnace.
Development of a hybrid sounding rocket motor.
(2013) Bernard, Geneviève.; Brooks, Michael John.; Roberts, Lancian Willett.; Pitot de la Beaujardiere, Jean-Francois Philippe.
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.
Development of a solar furnace heliostat.
(2016) Perumall, Preyen Agasthian.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
The Solar Energy Research Amplified Flux Facility (SERAFF) is the flagship project of University of KwaZulu-Natal’s Group for Solar Energy Thermodynamics (GSET). SERAFF will assume an on-axis optical configuration, common in solar furnaces around the world, comprising a flat, non-imaging heliostat reflector and a paraboloidal primary concentrator. At design-point conditions, a thermal power output of approximately 5 kW is expected with a peak flux in the region of 3 MW/m2. The facility will provide the University of KwaZulu-Natal with a platform to undertake wide-ranging research in disciplines including concentrating solar power, materials testing and processing, and solar thermochemistry, amongst others. The primary goal of this research was to design and fabricate a flat heliostat which will enable SERAFF to meet the specified thermal requirements. The first phase of this study was to characterise the available solar resource for Durban, South Africa, where SERAFF will be installed. A statistical algorithm was developed that processes historical ground-based solar measurements to generate a continuous function that estimates clear-sky direct normal irradiance (DNI) as a function of solar time and day number over a typical year. The three-dimensional surface that results from this function is termed a temporal DNI topograph (TDT) and can be used to define solar flux input for the modelling of concentrator systems. The heliostat dimensions are dependent on the size of the concentrator aperture it is tasked with illuminating. As such, sizing the concentrator was key. A geometrically based approximation of the maximum theoretical power output of a parabolic primary concentrator was developed. This model was used to calculate the diameter of the parabolic concentrator needed to achieve SERAFF’s specified power output. The model was validated against real solar furnaces around the world and it was found that the model approximated the power output for these solar furnaces within 12% of their published power output values. Following an optical analysis and illumination study, and after taking into consideration the practical and financial constraints placed on the project, it was decided that 3 m x 3 m was the most suitable size for SERAFF’s heliostat. A finite element analysis was used in the design process to assess the survivability (under load from a worst-case wind speed of 100 km/hr) and the rigidity (under load from an operational wind speed of 20 km/hr) for the different heliostat design concepts considered. After analyses of the FEA results it was decided that a classical T-shape design with an aluminium mirror backing frame would be employed. Fabrication of the structural components was undertaken at the department of Mechanical Engineering’s workshop and assembled at a temporary site in close proximity. Consideration was given to the effect the fabrication process would have on the tracking and optical accuracy of the heliostat. The total cost of fabrication was R91,655, exceeding the budget of R85,000 by R6,655. This was due to high import taxes paid on the slewing drive actuator and polished aluminium mirror facets. The actual cost of materials and components was R70,353 excluding the import taxes.
Development of a universal impeller test rig for scaled testing of high performance impellers.
(2014) Philogene, Luke Charles.; Smith, Graham Douglas James.; Brooks, Michael John.; Bindon, Jeffrey Peter.; Snedden, Glen Campbell.
This dissertation presents the validation of a universal impeller test rig, designed by the author and constructed at the University of KwaZulu-Natal (UKZN). The research was conducted as part of UKZN’s Aerospace Systems Research Group’s (ASReG) work into liquid rocket propulsion. The rig will be used to evaluate the performance of an impeller, developed as part of ASReG’s research, for use in a hypothetical launch vehicle’s fuel turbopump. Head rise versus flow rate characteristics, as well as cavitation performance will be assessed by the rig. The power requirements of the impeller necessitated the reduction in rotational speed and geometric size of the test case. Scaling laws and dimensionless numbers were used to predict the test case performance based on the design performance. This predicted performance was then used to determine specific parameters used in the rig design. Validation of the rig and testing procedures was performed using a standard industrial KSB ETA 125 – 200 centrifugal pump, by comparing the experimental results with those of the supplier. Head rise characteristics were determined by measuring the change in pressure between the inlet and discharge of the pump and then plotted against the flow rate for varying system heads. Cavitation performance was assessed by decreasing the inlet pressure while maintaining a constant flow rate. This was performed at various flow rates within the range of operation. Head breakdown, vibration and noise levels, both in the time and frequency domains, were used to assess the cavitation performance. The head rise versus flow characteristics of the pump, determined on the rig, showed good agreement with the supplier’s data. Cavitation performance, determined by head breakdown, was also in accordance with the supplier. It was found that both the vibration and general noise levels increased, indicating the presence of cavitation, before any head breakdown was detected. By monitoring the level of the high frequency noise in particular, > 10 kHz, the presence of cavitation was detected at a significantly higher inlet pressure than would be suggested by the head breakdown approach.
Development of liquid propellant tanks for a suborbital launch vehicle.
(2022) Mchunu, Vulinhlanhla Salvation.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
Having developed several hybrid sounding rockets, the Aerospace Systems Research Group (ASReG) at the University of KwaZulu-Natal is currently investigating the development of an indigenous launch vehicle for micro satellites. As part of this effort, a liquid propellant rocket engine called the South African First Integrated Rocket Engine (SAFFIRE) is in the advanced design phase. SAFFIRE combusts liquid oxygen and kerosene propellants to generate thrust. Following ground tests, the first version of the SAFFIRE engine will be incorporated into a single-stage launch vehicle to test its flight performance during the suborbital flight. This study aimed to develop a design procedure and subsequent engineering designs for propellant tanks suitable for use by this launch vehicle, known as the Suborbital Test Vehicle (STEVE). The liquid oxygen and kerosene propellant tanks were designed according to NASA propellant tank design guidelines based on the mechanical properties of half-hard 301L stainless steel – the alloy selected as the material of construction for both tanks. This material has various advantageous characteristics, including its compatibility with liquid oxygen, its high strength once work-hardened and its increased strength and ductility at cryogenic temperatures. As part of the study, comprehensive material testing was conducted to establish a suitable tank welding procedure and to evaluate the achievable weld efficiency. For the best performing welding procedure assessed, mean weld efficiencies with respect to yield strength and tensile strength were determined to be 70 % and 81 %, respectively. A trial propellant tank was fabricated using the selected welding procedure and subsequently subjected to a destructive hydrostatic pressure test. The outcomes of this test provided a clear indication of the modes and progression of tank failure and served to inform final design work. In terms of propellant tank layout, a tandem configuration with the liquid oxygen tank positioned above the kerosene tank was selected, in order to improve the stability characteristics of the vehicle and to minimise total feedline length. To reduce vehicle drag and mitigate aerodynamic heating effects, the liquid oxygen feedline was configured to pass coaxially through the kerosene tank via a tunnel tube. The incorporation of elliptical tank ends in both tank designs was dictated by pre-existing tooling made available by the tank end manufacturer. Based on these design characteristics, the anticipated tank loading conditions and the mechanical properties of the as-welded 301L stainless steel alloy, a minimum wall thickness requirement of 2 mm was determined for both tanks via finite element analysis.
A high-flux solar concentrating system.
(2011) Mouzouris, Michael.; Brooks, Michael John.; Roberts, Lancian Willett.
This research investigates the collection of concentrating solar energy and its transmission through optical fibres for use in high temperature applications such as lunar in-situ resource utilisation (ISRU) programmes, solar power generation and solar surgery. A prototype collector, known as the Fibre Optic Concentrating Utilisation System (FOCUS), has been developed and is capable of delivering high energy fluxes to a remote target. Salient performance results include flux concentrations approaching 1000 suns with an overall optical efficiency of 13%, measured from the inlet of the collector to the fibre outlet. The system comprises a novel solar concentrator designed to inject solar energy into a four metre long fibre optic cable for the transmission of light to the target. A nonimaging reflective lens in the form of a 600 mm diameter ring array concentrator was chosen for the collection of solar energy. Advantageous characteristics over the more common parabolic dish are its rearward focusing capacity and single stage reflection. The ring array comprises a nested set of paraboloidal elements constructed using composite material techniques to demonstrate a low-cost, effective fabrication process. At concentrator focus, a fibre optic cable of numerical aperture 0.37 is positioned to transport the highly concentrated energy away from the collector. The cable is treated to withstand UV exposure and high solar energy flux, and allows flexibility for target positioning. A computational analysis of the optical system was performed using ray tracing software, from which a predictive model of concentrator performance was developed to compare with experimental results. Performance testing of FOCUS was conducted using energy balance principles in conjunction with a flat plate calorimeter. Temperatures approaching 1500°C and flux levels in the region of 1800 suns were achieved before injection to the cable, demonstrating the optical system's suitability for use in high flux applications. During testing, peak temperatures exceeding 900°C were achieved at the remote target with a measured flux of 104 W/cm2 at the cable outlet. The predicted optical efficiency was 22%, indicating that further refinements to the ray trace model are necessary, specifically with regard to losses at the inlet to the cable. FOCUS was able to demonstrate its usefulness as a test bed for lunar in-situ resource utilisation technologies by successfully melting a lunar soil simulant. The system permits further terrestrial-based ISRU research, such as oxygen production from regolith and the fabrication of structural elements from lunar soil.
The hydrodynamic design and analysis of a liquid oxygen pump impeller for a rocket engine.
(2018) Singh, Nalendran.; Brooks, Michael John.; Smith, Graham Douglas James.; Snedden, Glen Campbell.
The deployment of micro- and nanosatellites has greatly increased over the past few decades with advances in miniaturized electronics for communication, imaging and attitude control. The South African satellite industry is now also currently developing two microsatellites and nanosatellites for launch by foreign providers. The outsourcing of launch services to foreign providers is costly and can lead to unanticipated delays. In this context, the UKZN Aerospace Systems Research Group (ASReG), in conjunction with the Council for Scientific and Industrial Research (CSIR) has begun designing a modular and compact liquid propulsion engine (LOX/RP-1) named SAFFIRE (South AFrican First Integrated Rocket Engine). This dissertation details the design and analysis of the liquid oxygen pump that delivers the oxidiser to the SAFFIRE combustion chamber at high pressure, where the propellants are burnt and expelled, generating thrust. The pump is electrically powered as opposed to the conventional turbine-driven turbopump, to further simplify start-stop procedures and reduce the complexity of the engine. The pump’s operating conditions were determined by an engine performance analysis, with these results forming the initial conditions for the pump design process. The oxidiser pump is required to deliver a mass flow rate of 6.13 kg/s at a pressure of 62.8 bar. The pump was designed using conventional centrifugal pump design procedures, with special considerations taken due to the working temperature of liquid oxygen being -183°C. The final one-dimensional design for the impeller was developed using the commercial software PUMPAL™, which was provided by the CSIR. A 3D impeller geometry was developed by importing the one-dimensional design into AxCent™, where quasi-3D Multiple Stream Tube (MST) analysis and full 3D computational fluid dynamics (CFD) simulations were performed. The impeller design was refined multiple times until the parameters set by the engine performance analysis were met. The AxCent™ analyses determined that low-pressure zones occurred at the inlet of the pump impeller. Hence Star-CCM+™, which has a more robust computational solver and allows for a full transient, multiphase CFD to be performed, was employed to analyse any potential cavitation affects. The results from Star-CCM+™ and AxCent™ were compared and designs altered until a final design was realized that met the prescribed performance parameters. The final pump impeller has an outer diameter of 86 mm, delivering a mass flow rate of 6.13 kg/s at a pressure of 64.2 bar. The pump operates at an efficiency of 60.8% requiring a power input of 51.96 kW at a rotational speed of 26000 rpm.
The hydrodynamic design and analysis of an RP-1 pump for a liquid rocket engine.
(2018) Chetty, Creason.; Brooks, Michael John.; Smith, Graham Douglas James.; Snedden, Glen Campbell.
South Africa has a fledgling satellite industry but lacks the ability to launch spacecraft into low Earth orbit. As a result, the University of KwaZulu-Natal’s (UKZN’s) Aerospace Systems Research Group (ASReG) began the development of the South African First Integrated Rocket Engine (SAFFIRE). SAFFIRE aims to be a versatile, small scale, liquid rocket engine capable of being clustered for use on small-satellite (‘small-sat’) launch vehicles. The propellants for the proposed engine are Rocket Propellant-1 (RP-1) and liquid oxygen (LOX), which are fed into the combustion chamber via the injector. The uniqueness of SAFFIRE lies in the use of electrically driven pumps (‘electropumps’) as opposed to the conventional turbopump design. The electropump system has the fuel and oxidiser pumps independently housed and driven by brushless DC motors, which draw power from a lithium-polymer battery pack. A hypothetical launch vehicle was proposed to validate design specifications for the SAFFIRE engine, from which the hydrodynamic requirements of the electropump system were obtained. A meanline design algorithm was developed, using conventional design methods for centrifugal pumps. The algorithm was constructed to simultaneously meet the hydrodynamic system requirements of the engine, minimize the potential of cavitation at the fuel pump inlet and maximize the operational speed to minimize the overall pump weight. The hydrodynamic requirements of the system result in a low specific speed design, thus placing the pump in the region between full emission centrifugal pumps and positive displacement pumps. The low specific speed presented unique problems, not commonly encountered via the conventional pump design method, such as excessively small blade exit widths that are sensitive to dimensional variations. The Barske pump was investigated as a potential solution; it is a partial emission pump with the meanline design being governed by vortex theory. A comparative analysis between the conventional and Barske design was done using computational fluid dynamic techniques. The final hydrodynamic design is a hybrid between a Barske impeller and a scroll collection volute, which is typically found on a full emission pump. An investigation was done to determine an appropriate solution for mitigating the cavitation. It was found that the initial 3 bar tank pressure, suggested by literature, is applicable for an equivalent engine utilizing a turbopump system. The optimal tank pressure for the electropump system was found to be 9 bar. This increased available pressure head at the inlet of the pump eliminated any form of cavitation. The hybrid pump delivers 62.12 bar of pressure at a mass flow rate of 2.75 kg/s with a 62.12 % efficiency.
Modeling and experimental validation of a loop heat pipe for terrestrial thermal management applications.
(2013) Page, Matthew Christopher.; Brooks, Michael John.; Roberts, Lancian Willett.; Bemont, Clinton Pierre.
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.