Pusat Pengajian Kejuruteraan Aeroangkasa - Tesis

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An investigation into the influence of material properties on the performance of savonius turbines in hydrokinetic applications
(2023-09-01)
Mohamed Shamsuddin, Muhamad Syukri
Savonius hydrokinetic turbines (HKT) are practical for off-grid power generation due to their simplicity, self-starting capability, and low-speed requirement. Although the impact of turbine material selection on durability has been established, there is still limited research on its influence on the turbine’s power performance. Therefore, this research aims to investigate the effect of different material properties on the performance of a conventional, two-bladed Savonius rotor. The turbine’s performance was evaluated in three key aspects: power performance, self-starting characteristics, and flow structure. Based on the gap found in the literature review, three different material properties were investigated: weight, surface roughness, and stiffness. The study also considered the effect of water absorption as the turbine is developed for hydrokinetic applications. The experiment was conducted at various Reynolds numbers, R3 ranging from 5.22 ×104 to 9.40 ×104. The turbine performance was then compared in wind and water testing using the principle of dynamic flow similarity. Findings from the power performance analysis were then used to rank five different materials using multi-purpose decision-making analysis (MCDM). Results from the wind tunnel testing suggested that the 𝐶pmax increased with increasing R3, with the highest increment (150%) recorded at 5.22 ×104 to 6.27 ×104. The 𝐶pmax was also found to increase with increasing weight, increasing surface roughness, and decreasing stiffness. The highest 𝐶pmax increment was recorded at 220%, 201%, and 30%, respectively. However, the influence of material properties was significantly influenced by the variation in R3, indicating that some materials may be advantageous within specific ranges of flow speed. For water absorption, the 𝐶𝐶𝑃𝑃 performance of all turbines was found to be less affected, despite having deteriorated flexural strength property of up to 62.3%. The MCDM analysis revealed that soft plastic like poly-lactic acid (PLA) would have a higher performance index at R3 ≤ 6.27 ×104. However, at higher R3, i.e., R3 ≥ 7.31 ×104, conventional materials like aluminium (ALU) turbines would outperform the other materials. The outcomes of the current study demonstrated the impact of various material properties on the power performance of the Savonius turbine, emphasizing the significance of the material selection process particularly for power enhancement.
Automated route planning with obstacle avoidance for unmanned aerial systems
(2021-10-01)
Debnath, Dipraj
Autonomous unmanned aerial systems (UAS) are increasingly becoming a major focus of study in both academia and industrial sectors. With the aim of resolving the path planning issue, this study adopts the travelling salesmen problem (TSP) and solve it by applying an Improved Genetic Algorithm (IGA) that can identify the optimal way in terms of both distance and time. The outcome shows that the approach of the GA is relatively effective in finding not only the optimum path distance but also minimize and in some cases eliminate the crossing paths. Another value-added feature for UAS is to be equipped with a reliable obstacle detection and avoidance system especially when it operates in low-flying zone. The obstacles can be considered as a hindrance to the UAS flight path, and the algorithm should detect and avoid it through avoidance waypoints. The avoidance approach proposes here combines the linear equation and locating its intersection points between the diagonal lines within the square area. Based on that, the square areas are used to guide the algorithm to compute new safe avoiding waypoints. The size of the square areas is based on the safe avoidance distance defined based on the UAS specification such as size, speed and UAS type. All Algorithms here are created in MATLAB and then tested and assessed in several scenarios where the UAS must avoid obstacles during operation. The result from this research shows that the algorithms can provide reasonable solutions in finding the optimal path and avoiding obstacles based on the scenarios. Therefore, this approach is very helpful for any UAS that need a pre-plan mission prior to the actual flight operation.
Cfd simulation to study the effects of ribs in a converging nozzle flow at sonic mach number
(2020-04-01)
Tham, Foo Kean
The presence of a blunt base leads to flow separation in aerodynamic bodies, which causes a low-pressure in the wake region. At sonic Mach number, low pressure in the wake region contributes up to sixty percent of the total drag. This study is conducted to study the effect of the rectangular ribs on the base pressure. The parameters considered are the nozzle pressure ratio, rib’s aspect ratio, Length to Diameter (L/D) ratio of the duct when placed circumferentially operating from subsonic to sonic Mach number. The simulation is performed using CFD, and the k-ɛ turbulence model is employed. Initially, the simulation results obtained are validated with experimental work for different L/D ratio of the duct at various Nozzle Pressure Ratio’s (NPR), and the aspect ratio of the ribs from 3:1 to 3:3 for area ratio of 6.25. The results are in good agreement with the experimental results. Later simulations are done for a single rib, which is placed at different locations and aspect ratios for NPRs in the range from 1.5 to 5 from the base. Base pressure variations, velocity, and pressure field changes for the above variables are discussed. The simulation results indicate that the rib breaks the primary vortex at the base and form multiple vortices and hence controls the base pressure in the wake region. The results show that a rectangular rib with a lower aspect ratio is effective in reducing the base pressure, whereas the rib with a higher aspect ratio tends to increase the base pressure. The simulations are also conducted for a duct with a diameter, D = 20 mm. In this case, the rectangular rib with aspect ratios 3:1, 3:2, and 3:3 is placed at 20 mm, 40 mm, 60 mm, and 80 mm locations, for the same NPRs. Results show that the height and position of the rib plays a vital role in controlling the base pressure.
Classification of misfire technique using wide band oxygen sensor
(2024-09-01)
Md Sharib, Mohd Khairul Nizam
Problems with the engine often occur instability of the flame in the fuel mixture and cause it to fail to provide accurate ignition readings. In this study, a novel approach to classify the misfire techniques using wide band oxygen sensors is presented. Each signal that is given because of the failure of the fuel mixture flame should be investigated further. This research study has focused on a small single-cylinder engine with four strokes to detect the existence of abnormal conditions in engine combustion. The approach in this study began with the use of basic simulation methods through learning based on models in MATLAB through SIMULINK application version R2022b and experimental tests in the laboratory. The tested engine completed modified with the setting of input data through the Engine Control Unit (ECU) interface with Redleo Pro 9.1X software. Data was acquired with a wide band oxygen sensor and the signal was transmitted digitally by a tablet oscilloscope. The signal emitted through the oscilloscope has been analyzed and extracted by the pre processing on smooth method. The efficiency and sensitivity effects of sensory use of this wide band oxygen sensor have been observed with varying engine speed variations. The findings show abnormal combustion occurs at high-speed conditions of 4000-5000 RPM and a low Volumetric Efficiency (VE) of 2.06 % and 16.2 ignition degrees. The combination of simulation and experimental methods gives a good result by showing that lean combustion affects the signal appearance in detecting abnormal noise in the engine.
Conceptual design of small scale unmanned aerial vehicle (predator)
(2010-05-01)
Abd Manap, Amir
Nowadays, a UAV is an important vehicle. Many countries already have their own UAV, even Singapore. Malaysia already has RazakSAT, so it is possible to have a UAV developed by Malaysian. The use of the UAV is everywhere because it gives a lot of benefit which include cost reduction, increment in safety level and simplification of hard tasks. The main objective of this thesis is to generate a 3D model of Predator and compare it with the actual Predator that exists nowadays. Seven pivot points was suggested by Anderson[10] for conceptual design which are mission requirements, first estimation of the airplane weight, critical performance parameters, layout configuration, better weight estimation, performance analysis and optimization. Each single result was compared to the Predator’s performance and was discussed why there is a difference between those two UAV’s parameters. This UAV was designed to operate in Malaysia so it has different parameters compared to Predator developed by USAF. The project outcome is a 3D model of the Predator and it is a bit different from the actual Predator but perhaps the layout configuration will changes in preliminary and detail design. The result obtained is acceptable and it is possible for Malaysian to have own UAV. It will be used in preliminary design which aerodynamic, structural and control system analysis take place. Finally, the design process will enter detail design also called nuts and bolts phase which size, numbers and location of fasteners will be determined before the fabrication takes place.
Effect of alumina and magnesia nanofillers on mechanical and water absorption properties of surface treated flax/pla and jute reinforced epoxy composites
(2022-06-01)
Amjad, Adnan
Natural fibre-based materials are gaining popularity in the composites industry, particularly for aerospace, defence, construction, automobile structural and semi-structural applications. Continuous natural fibre composite materials not only offer low weight and better strength but are also biodegradable and eco-friendly. Natural fibres are a valuable and robust replacement for synthetic fibres, but the incompatibility between natural fibre and polymer matrices and the higher moisture absorption percentage of natural fibre limits their applications. To overcome these flaws, surface treatment of natural fibre and nanofiller addition have become some of the most important aspects of improving the performance of continuous natural fibre composite. In this research work, a comparative performance evaluation was conducted to investigate the effect of Al2O3 and MgO nanofillers on the alkali-treated and untreated flax/PLA and jute fibre reinforced epoxy laminates fabricated by vacuum bagging technique. The 5% NaOH solution was used to treat the flax/PLA and jute woven fabric and Al2O3 and MgO nanofillers were mixed with epoxy in a concentration from 1%wt - 4%wt. The developed laminates were evaluated based on mechanical and water absorption properties. The results show that the treated flax/PLA and jute fibre reinforced laminates display higher mechanical properties than the untreated fibre. In flax/PLA laminates, the treated flax/PLA reinforced MgO filled laminates increase the tensile strength by 56%, impact strength by 28% and interlaminar shear strength by 150%, while the treated flax/PLA reinforced Al2O3 filled laminates increases the flexural strength by 290% and compressive strength by 460% as compared to laminates without nanofillers. In jute laminates, the treated jute reinforced MgO filled laminates increase the tensile strength by 60%, flexural strengthby 67%, impact strength by 42%, compressive strength by 130%, while the treated jute reinforced Al2O3 filled laminates increase interlaminar shear strength by 62% as compared to laminates without nanofillers. The mechanical properties of the composites increase with the addition of both nanofillers up to 3 wt.%. Fibre surface treatment and nanofillers also affected the water absorption behaviour of flax/PLA and jute composite. Untreated reinforced composite absorbed more water than treated. The treated flax/PLA and jute reinforced MgO filled laminates exhibit the lowest water absorption at 4 wt. % of MgO, the treated flax/PLA is 72.4%, and the treated jute is 74.4 % less absorbent than the unfilled composite. Hence, the inclusion of nanofillers and the fibre surface treatment have improved the laminates' mechanical and water absorption properties.
Effect of grooves on aerodynamic performance of a low reynolds number propeller
(2020-10-01)
Seeni, Aravind Seeni
UAVs in the future will be designed for next-generation applications such as product delivery from source to end-user. These UAVs weigh in the range of 1 to 10 kg and are powered by small-scale propellers that operate in the low Reynolds number (Re) regime (<100,000). The design of low Re propellers has gained particular importance in the research community with the development of UAVs. Small-scale propellers typically have low aerodynamic efficiency. Improvement in aerodynamic performance and efficiency of these propellers will enhance the endurance and operational range of UAVs. The desired requirement is a propeller design that can produce improved thrust and reduced torque. In order to fulfil such an objective, a novel technique known as the grooved design is studied on a small-scale propeller of pre-defined geometry. This grooved design is based on passive flow control, a technique in which the aerodynamic characteristics of a body is enhanced through the modification of surface geometry. A numerical study is performed on a baseline Applied Precision Composites 10x7 Slow Flyer propeller to investigate grooved passive flow control technique on propellers. Computational Fluid Dynamics as a method to solve Reynolds Averaged Navier Stokes equations is used as a tool to analyse this novel design. A steady, incompressible flow around the propeller is assumed. The commercial code ANSYS Fluent is selected as the solver. First, 2D simulations are conducted on NACA 0009 airfoil at very low Re of 20000 to study the flow characteristics of an airfoil at such low Re. The result showed at such low Re, as the α increases, the turbulence wake contours advanced from trailing edge to leading edge. Secondly, the effect of groove geometry variation is analysed. Grooved cross-sections considered in this study are rectangular in geometry with dimensions 0.1×0.1mm, 0.1×0.2mm, 0.1×0.3 mm, 0.2×0.1mm, 0.2×0.2mm and 0.2×0.3mm and placed at 4 specific locations, 0.09c, 0.17c, 0.32c and 0.42c from leading edge. Finally, the effect of positioning multiple grooves is investigated in which grooves of dimensions 0.1×0.2 mm, 0.1×0.3mm, 0.2×0.1mm, 0.2×0.2mm and 0.2×0.3mm are placed interchangeably at 0.09c, 0.17c, 0.32c and 0.42c. 53 different single and multi-grooved designs constitute the study in total. The results of the study showed that for the model with 0.2×0.1mm groove at 0.17c, the efficiency improved marginally over baseline for 11 cases of advance ratios and decreased for 3 cases of advance ratios. For all other models, the efficiency did not improve relative to baseline for most and/or all advance ratios.
Effects of fabric architecture on mechanical properties of natural fibre (jute, hemp and flax) reinforced polypropylene composites
(2020-10-01)
Awais, Habib
Thermoplastic bio-composites are particularly attractive and ideal materials for weight critical applications. Long natural fibre reinforced thermoplastic composite materials not only offer low weight, better strength than short fibre reinforced composites but are also biodegradable and ecofriendly. The impregnation of resin into the reinforcement is considered as a major concern during the fabrication of thermoplastic composites. Intermediate materials known as commingled fabrics have evolved as an alternative solution to overcome the viscosity constrain and reduce the flow distance. Therefore, in this study, novel commingled fabrics were developed by aligning the polypropylene fibres alongside the reinforcement natural fibres (jute, hemp and flax) using weaving and knitting techniques to assist the fabrication of long fibre reinforced thermoplastic composites and to minimise the melt flow distance of resin. Thermal stability of reinforcing fibres (jute, hemp and flax) was assessed by thermogravimetric analysis (TGA). The strength of individual reinforcing yarn and fabrics was measured by single-strand method and strip method, respectively. A comparative performance evaluation was conducted on natural fibre (jute, hemp and flax) reinforced laminates fabricated using the woven, woven commingled and knitted commingled fabric architectures along with polypropylene matrix by compression moulding. The fibre volume fraction was 35 ± 2 % for all fabricated laminates. The effects of the fabric architecture on the mechanical properties of the fabricated laminates were assessed in terms of tensile, flexural, impact, short-beam shear (SBS) and compression after impact strength (CAI). The results show that flax fibres are more thermally stable than hemp and jute fibres and there is no significant mass loss up to 260 °C. The flax yarns and fabrics show higher tensile strength than hemp and jute yarns and fabrics owing to the difference in chemical composition. The results also show that the knitted commingled laminates display higher mechanical properties compared to the woven and woven commingled laminates. The knitted commingled laminates present higher tensile strength (13 % and 16 %), flexural strength (16.5 % and 14.3 %), Charpy impact strength (12 % and 54 %), SBS strength (20 % and 29 %) and CAI strength (37.9 % and 25.3 %) compared to the woven laminates and woven commingled laminates. The better performance of the knitted commingled laminates was ascribed by the improved wetting of fibres owing to the shortest average matrix flow distance. Although natural fibre reinforced polymer (NFRP) composites are emerging as a viable alternative to metal parts for lightweight components in the automotive and aerospace industry, their use is confined due to their poor performance properties. Currently, fillers are often incorporated in NFRP composites to modify their properties. This study also explores the reinforcing effects of hollow glass microspheres (HGM) as fillers in continuous NFRP composites. Tensile, flexural and impact tests were conducted to investigate the influence of HGM on the mechanical properties of the woven and woven commingled laminates. The results indicate that the loading of 1.5 vol. % HGM improves the tensile and flexural properties, but further addition of HGM (3 vol. %) leads to a decline in these properties; furthermore, the impact strength was significantly improved in woven and woven commingled laminates by the addition of 3 % HGM. The fracture surface morphology reveals the better wetting of fibres and straight yarn configuration in knitted commingled laminates compared to the woven and woven commingled laminates.
Elucidation of the rotor aerodynamics and performance of a self-starting darrieus turbine
(2023-03-01)
Selvarajoo, Shaza Rae
Global warming and over consumption of non-renewable energy sources are amongst the grand challenges facing humanity in the 21st century, where wind turbines provide an alternative source of power. However, wind flows in nature fluctuate greatly, which causes Darrieus turbines, a subset of vertical-axis turbines, to be in protracted transient modes that reduce their overall efficiency. The complex flow patterns surrounding these rotors, due to their interactions with multiple shed vortices, further exacerbate the reduced efficiency and complicate the elucidation of the rotor aerodynamics. In this work, a three-bladed H-Darrieus rotor was simulated numerically via a combination of the lifting line theory and vortex wake model, with their algorithms embedded in a software named QBlade. These algorithms model the entire self-starting process that consists of the linear and acceleration phases. Darrieus rotors face difficulty self-starting because of dead bands in the linear phase, where each dead band is a region when a net negative torque is generated over a single cycle due to a reverse dynamic stall. In the accelerated phase, significant torque is generated due to forward dynamic stalls, which then cause the rotor to enter the steady phase. The work herein elucidates the aerodynamics of a Darrieus rotor during self-start, via the use of a novel and newly developed in-house software named DRAFA. This software allows users to rapidly analyse Darrieus turbines, which significantly reduces the time taken to process raw data into insightful data. Its most significant aspect is the production of turbine vector diagrams which allow users to intuitively visualize the complex and spatio-temporally evolving inflow and force vectors on the turbine blades.
Equatorial ionization anomaly characteristics over malaysian region integrated by ground and satellite data
(2024-07-01)
Selvakone, Sivanandini
Equatorial ionization anomaly (EIA) is formed when both electric and magnetic fields intersect over the equator, resulting in electron density variabilities. The ionospheric irregularities disrupt radio communications and satellite operations by causing amplitude and phase scintillations of signals. Hence, the characteristics of the electromagnetic field and EIA must be studied simultaneously to understand the role of electromagnetic field variations on the EIA variabilities. Understanding these characteristics is important to mitigate the effects of the equatorial ionization anomalies on telecommunication and navigation systems. This study explores the periodic variations of electric and magnetic field intensities and their influence on the strength and development of EIA over the Malaysian region. Ground-based magnetometers from MAGDAS and INTERMAGNET systems, along with Swarm satellite data, are utilized for this synergistic analysis. The characteristics of EIA are studied for solar maximum and minimum years of 2015 and 2020, respectively. The investigation revealed diurnal and spatial variations in the EIA’s characteristics highlighting the influence of solar irradiance, space weather, and ionospheric dynamics. Notably, the EIA intensity, as indicated by geomagnetic variations, EEJ, drift velocity, plasma density, and temperature recorded by both sources was 36% higher in 2015 compared to 2020. This integrated approach enhances the understanding of the equatorial ionospheric phenomena and advances the accuracy of ionospheric forecasting models and predictions.
Hydrokinetic savonius turbine for sustainable energy in low-speed flows
(2024-01-01)
Abdullah, Mohd Safie
Hydrokinetic turbine (HKT) technology is both cost-effective and reliable, producing clean energy with minimal environmental impact. The goal of this research is to improve the power performance (𝐶𝑝) of a Savonius HKT in a low-speed river in Malaysia (Re < 1.5 × 105). Two methods are proposed to improve 𝐶𝑝 in this study. The first method involves developing and optimizing a novel blade profile using 3D CFD simulation with a systematic Design of Experiment (DOE). The best design out of 625 options was determined statistically using the Taguchi method and analysis of variance (ANOVA). The novel blade enhances 𝐶𝑝 by approximately 10.9% compared to the conventional design at optimal tip-speed ratio (TSR) (best 𝐶𝑝 = 0.159) and 16.7% improvement at higher TSR value of 0.9 (𝐶𝑝 = 0.158). Moreover, the novel blade outperforms the nature-inspired blade (golden spiral blade profile) by 27% in terms of efficiency. The second method focuses on developing and optimizing a new augmentation device called the wake accelerator. The device utilizes the Magnus Effect to improve overall flow by altering the wake profile behind the turbine. The Taguchi method and ANOVA were used to optimize the size, position, and location of the device. The 𝐶𝑝 improved by 83.73% at TSR = 1.1 (best 𝐶𝑝 = 0.4450). Additionally, this thesis investigates the effect of turbine size on structural behavior during stationary operation under various loading conditions. It provides insights into stress concentration around the turbine rotor, potential issues, and the optimal rotor angle for maintenance to minimize the stress. The computational fluid dynamics (CFD) and finite element analysis (FEA) simulations in this study are well-established and validated for precision and accuracy .
Investigating the relation of high temperature biofuel combustion with gas turbine rotor blade structure at increasing shaft speeds using fluid-structure interaction
(2024-07-01)
Noorashid, Muhammad Noorakmal
This study investigates the correlation between biofuel combustion temperature and the structural integrity of the high-pressure turbine (HPT) blade in an aircraft engine, examining the effects across a range of increasing shaft speeds from 8400 rpm to 10, 400 rpm. The biofuels were Jatropha Bio-synthetic Paraffinic Kerosene (JSPK) and Camelina Bio-synthetic Paraffinic Kerosene (CSPK). The fuels were tested as pure fuels and blended with Jet-A. The study was first performed by simulating the fuels in a Gas Turbine Simulation Program (GSP11) to evaluate changes in the thermodynamic properties of gas turbine engine components, particularly at the turbine. The results obtained served as input parameters for the boundary condition of the turbine blade model simulated in computational fluid dynamics (CFD) to visualize the flow behavior around the turbine blade. Fluid-Structure Interaction (FSI) approach is then used to analyse the impact on the turbine blade structure. For the same engine parameters, the results from GSP11 revealed a linear correlation between temperature and pressure across the gas turbine components with shaft speeds. Combusting biofuels produced lower temperatures and pressures than Jet-A, resulting in a lower engine thrust. Also, at all shaft speeds, the fuel flow and thrust specific fuel consumption (TSFC) of biofuels was 1% to 3% lower than that of Jet-A, indicating that the engine thrust improved while consuming less fuel. The combustion temperature and pressure reduction of biofuels contribute to the lower thermomechanical loading exerted on the turbine rotor blades. At all ranges of shaft rotational speed, utilizing biofuel as a blend leads to reductions of up to 0.047% to 0.232% in blade deformation, 0.045% to 0.116% in stress, and 0.076% to 0.274% in strain, ultimately improving the fatigue life cycles of the rotor blade by up to 0.274% to 0.699%. The reduction becomes more significant when pure CSPK and JSPK are utilized. This study serves as a preliminary analysis of the advantages of utilizing biofuels in the component structures of aircraft engines.
Investigation of ionospheric effects on ground based augmentation systems at low latitude region
(2024-09-01)
Rajwant Singh, Brelveenraj Kaur
Space-based technologies such as the Global Navigation Satellite Systems (GNSS) are playing an increasingly important role in aviation navigation due to the increasing demand for long-haul air travel. This encouraged airports to deploy Ground Based Augmentation System (GBAS) replacing the Instrument Landing System (ILS) which resulted in reduced delays and disruptions for travellers. Low latitudes and equatorial regions, such as Malaysia are more likely to experience ionospheric disturbances caused by solar activity and geomagnetic storms, which disturb the GNSS signals. The performance of the GNSS is subjected to risk as the integrity of the GBAS between the ground receiver and the aircraft deteriorates. This study analyse ionospheric scintillation and Total Electron Content (TEC) effects on the GBAS receivers installed at KLIA. The data collected was during solar minimum which reflected towards the GBAS in KLIA not experiencing any anomaly events that could disrupt the GPS receiver's signal during equinox months. The amplitude scintillation, S4 index values were found within (0.2 < S4< 0.5), indicating weak or negligible scintillation. The GBAS receivers consistently show of spikes of S4 data at precise times across the months, suspected due to nearby interference rather than active scintillation events. The TEC values vary from a low in the early hours of the day to a diurnal maximum between 15:00 LT and 18:00 LT before falling to a minimum in the afternoon. The TEC were particularly higher in September and March corresponding to the months of equinox. This paper investigates the ionospheric disturbance in the low latitude region and ideas for improving GBAS receiver performance for future developments.
Investigation on the physical, thermal and rheological properties of graphene and functionalised multi-walled carbon nanotube lubricant
(2022-09-01)
Mohammed, Aws Sadoon
The purpose of this study is to determine the effects of graphene (GR) and functionalised multi-walled carbon nanotube (FMWCNT) as mono and hybrid nanoparticles in SUNISO SL68 refrigerant lubricant in terms of dispersion, stability, thermal conductivity (TC), rheological, and tribological properties. This study is divided into three stages, finding the volume per cent (vol%) of the nanoparticles in the nanolubricant that represent higher stability, finding the surfactant ratio with nanolubricant to give the highest stability, and finding ratio combination between these nanoparticles and surfactant that gives higher viscosity index (VI) and less coefficient of friction (COF) and wear scar diameter (WSD) values. The dispersion and the stability parts have been examined through visual observation, Zeta potential value measurements, and UV-vis spectrum intensity. The TC part has been measured at different temperatures and vol%. The rheological properties have been concluded by viscosity values at different temperatures and shear rates, and by conducting ASTM 2270 standard for viscosity index measurement. The tribological properties have been concluded by ASTM D4172 and ASTM D2783 standards for both wear and extreme pressure analysis. The outcome of the first stage revealed a vol% between 0.025 vol% to 0.100 vol% is suitable for the study of both GR and FMWCNT in mono and hybrid system. The value of 0.100 vol% was the best for both GR and FMWCNT. The outcomes highlight higher stability and TC for the samples with higher vol%. The TC improvement recorded 9.5% TC higher than pure lubricant. The outcome of the second stage revealed better dispersion and stability for Cetrimonium bromide (CTAB) surfactant than Sodium Dodecylbenzene Sulfonate (SDBS) and Sorbitan monooleate 80 (SPAN-80) surfactants for both GR and FMWCNT in mono nanoparticle system. GR's best ratio between GR:CTAB is 1:1, and FMWCNT's best ratio between FMWCNT:CTAB is 1:8. UV-vis spectrum recorded over 800% higher absorbance between samples with best CTAB ratio and pure oil after 14 days. In hybrid nanolubricant, the CTAB surfactant gains stability over non-surfactant samples even after 30 days. The outcome of the last stage highlights the shear-thinning flow behaviour of the nanolubricant. FMWCNT nanolubricant samples show an intensive level of shear-thinning flow behaviour than GR nanolubricant samples. The viscosity index (VI) tends to increase with CTAB samples, low vol% GR nanolubricant samples, and high vol% FMWCNT nanolubricant samples. The VI increased as much as 6% for FMWCNT100 sample. Tribological outcomes indicate GR nanoparticles tend to reduce the coefficient of friction (COF) and increase wear scar diameter (WSD), as they act as a nano ball bearing. On the other hand, FMWCNT nanoparticles tend to increase the COF and reduce the WSD, as they act as fillers. However, hybrid nanolubricant samples aided with CTAB show a higher trend in COF and WSD compared to samples without CTAB.
Ionospheric and geomagnetic disturbance study during seismic activity in southeast asia using space borne and ground sensor
(2021-10-01)
Mohamad Rizal, Nur Awatiff
Many studies on the pre-earthquake involving various methods have been conducted to understand the earthquake activity. The Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) effect describes what physical processes are involved prior to an earthquake. Southeast Asia is a region where earthquakes have a high frequency to occur, and the earthquake’s studies in this region still lack and poorly understood. Therefore, this study aims to understand the pre-earthquake behaviour by investigating the behaviour of the geomagnetic field and the components before an earthquake. The geomagnetic field data is collected using space borne sensors and ground sensors. Satellite data will be collected by the CHAMP and Swarm satellites, while MAGDAS will collect ground sensor data. This study is based on the major earthquakes (M>6.5) that happened in Southeast Asia for eleven years, from 2008 to 2018. Two weeks prior to every listed earthquake, the data was collected, filtered, and distinguished from any unrelated geomagnetic anomalies such as solar activities and magnetic storms. Based on the result, at least one disturbed profile would appear before a major earthquake. The dominant component that showed the most significant anomalies on every disturbed profile was the y-component and N-component for satellites and MAGDAS data, respectively. Lastly, the mass collecting data from both satellite and ground sensors hopefully will be helpful to the improvement for the future real-time earthquake precursor in the Southeast Asia region.
Modeling and control of the ducted fan lift system
(2023-09-01)
Jiang, Hanjie
Urban air mobility is an emerging concept that has been proposed in recent years which encompasses a diverse range of Vertical TakeOff and Landing (VTOL) vehicles that function similar to passenger-carrying drones for on-demand transportation. Among them, the car-like VTOL is favorable due to its compact configuration, safe rotors, high user affinity, and technological fashion. These characteristics are frequently derived from the Ducted Fan Lift System (DFLS). Compared to an electrically powered DFLS, a fuel-engine-powered DFLS is more likely to meet the requirements of high power and high energy density, thereby delivering superior flight performance. Two-stroke aviation piston engine-driven DFLSs are multivariable with highly non linear dynamics, which poses challenges for control engineers in both modeling and control. Firstly, it is difficult to accurately model and evaluate the aerodynamic performance of a ducted fan in a rapid and theoretical manner. Secondly, constructing a general dynamic model for the two-stroke engine control application is a daunting task. Lastly, the engine-driven DFLS is a complex, multivariable system with tightly coupled nonlinear dynamics, which creates additional obstacles for effective control. To address the before-mentioned problems, this thesis developed a ducted fan model using blade element theory and momentumtheorytosupport the rapid scheme demonstration and control study. Meanwhile, a general Mean Value Engine Model (MVEM) of two stroke aviation piston engines was developed, which is represented by appropriate empirical equations that require little engine data and easily capture the main dynamics. Based onthetwoproposedmodels, this thesis developed an Adaptive Model Predictive Control (AMPC) strategy with an associated Linear Parameter Varying (LPV) model for controlling the engine-driven DFLS. The LPV model is derived from an Radial Basis Function (RBF) network model trained with the data from the proposed general MVEM. The proposed AMPC was selected in the Air-Fuel Ratio (AFR) control study of HIRTH-3203 for better precision and faster response, compared with the control strategy using Deterministic Policy Gradient (DPG) algorithm. The ducted fan of a 1:3 scale verifier for a flying car scheme was designed and evaluated using the proposed method, a numerical method, and a bench test. Compared to the test results, the proposed model showed its precise performance with an average difference of 1.9%. The proposed engine model was validated using HIRTH-3203 and NU-57 laboratory data, and the results illustrated that the issues of fitting simplicity and general applicability were well addressed. The efficiency of the proposed RBF-based AMPC was demonstrated through numerical simulations of a vertical take-off thrust preparation process for the DFLS. The simulation results indicate that the proposed AMPC method can effectively control the DFLS thrust with a relative error below 3.5%.
Numerical and experimental aeroacoustic analysis of cavity at low wind speed
(2024-06-01)
Hairudin, Wan Masrurah
Wind-induced noise (aeroacoustics) in the microphone port cavity of two-way radio is a prevalent issue that significantly affects speech and audio quality, particularly in windy conditions. This thesis presents a comprehensive investigation of wind induced noise (aero-acoustic) generation in the microphone port of two-way radio through numerical and experimental analyses. A smoke visualization test was conducted in a closed wind tunnel to observe the flow structure, while a coupled direct-hybrid Computational Aero-Acoustics (CAA) method called scFLOW2Actran was employed for simulations. This method simultaneously addresses fluid and acoustics field within a single computational framework, utilizing large eddy simulation (LES) and Ffowcs William-Hawking (FW-H) acoustic analogy. The CAA investigation focuses on analyzing noise parameters such as cavity length to depth (L/D), wind speed, and wind angle orientation. Numerical results presents pressure, velocity distributions, and noise level in the near-field and far-field regions for both original and the modified microphone port geometries. The validation of the numerical results and experimental test shows a 3 dB difference at frequency of 20 Hz, confirming the feasibility of the proposed simulation method. The findings indicate that higher noise levels are observed at a cavity length to a depth of 0.7, particularly under higher wind speeds of 4.4 m/s and wind angle direction of 45°. Regarding the microphone port modifications, the result reveal that the Helmholtz resonator port with an additional aperture provides a lower reduction of 19 dB in noise level compared to others modifications. The findings also suggest that by modifying the microphone port can help reduce by weakening vortex effects. These results contribute to the understanding of wind-induced noise generation and offer valuable insights for design and acoustic engineers involved in the development of mobile telecommunication devices. The aeroacoustics analysis proves useful in devising noise reduction strategies and guiding improved microphone port design within these devices.
Numerical and experimental study of passive control in the form of ribs at sonic and supersonic mach numbers
(2023-10-01)
Khan, Ambareen
Flow from Converging and Converging-Diverging nozzles expanded suddenly into the enlarged duct has been investigated experimentally and numerically, with emphasis on the base pressure, and the development of flow in the duct. In this investigation, the variables considered are the Mach number, Nozzle Pressure Ratio, area ratios, rib geometry, and rib size. Experiments were conducted to control the flow by a semi-circular rib at sonic and supersonic Mach numbers. Results show nozzles flowing under favorable pressure become effective and there is a significant increase in the base pressure. Numerical simulations were done for three area ratios (i.e. 3.61, 5.76, and 7.84) using three shapes of the ribs (i.e. Rectangular, triangular, and semicircular) of three different sizes (i.e. 6 mm, 8 mm, and 10 mm diameter) for four rib locations (i.e. 1D, 2D, 3D, and 4D) at sonic and supersonic Mach numbers. As experimental tests were conducted up to NPR 10 nozzles remained over-expanded for Mach 2.2 and 2.5. To account for design NPR and beyond the numerical simulations were done up to NPR = 25. As a first step CFD results were validated with the experimental results for semi-circular ribs. Among the three shapes of the ribs rectangular ribs seem to be the best option and result in a maximum increase in the base pressure. While scanning the wall pressure in the duct, the flow field is not aggravated due to the presence of various ribs, and the flow field with and without control remains the same.
Numerical study on modification of the chevron nozzle design for reduction of noise emission
(2022-12-01)
Abd Rahim, Muhammad Afiq Farahi
This study investigates into the effects of various vortex generator designs on the chevron nozzle for improving mixing between hot and cold gases. A vortex generator is a well recognized device on creating vortices in a stream. The horseshoe design, the counter-rotating arrangement, and the co-counter rotating arrangement are three types of vortex generators used in this study. These vortex generators are used to improve aerodynamic performance of the wing and reduce noise generated by aerodynamic noise at a fuel port section. This study uses a Chevron nozzle design based on NASA Glen Research Centre SMC006 as initial design and these three different vortex generators have been applied on the root of SMC006 to test the effectiveness of a different types of vortex generators for improving mixing in the liquid. An improvement in mixing between the core's hot gases and cold gases from the bypass flow or ambient flow might be achieved by a counter rotating design that appears like it would work well.
Optimised formulation of eggshell powder filled glass fibre reinforced polymer composite: mechanical, thermal and fire resistance properties
(2024-07-01)
Muhammad, Athifah Fakhirah
This study explores the use of chicken eggshell powder (ESP) as a biofiller in E-glass fibre-reinforced composites. Eggshells, typically agricultural waste, are low density, abundant, inexpensive, and effective as flame-retardants. The research examines the mechanical, thermal, and fire resistance properties of GFRP composites with ESP. The eggshells were cleaned, dried, crushed, pulverized, and sieved to obtain filler powders of 50 μm, 100 μm, and 150 μm sizes. These powders were mixed with epoxy and laminated with E-glass using a wet hand lay-up technique. The mechanical performance was evaluated based on filler size and loading concentration, with ANOVA used to assess the maximum tensile and flexural stress. The optimal parameters obtained from the regression analyses were 150 µm filler size and 10 wt% loading, resulting in a maximum tensile stress of 272.95 MPa, flexural stress of 189.15 MPa, and a desirability score of 0.874, indicating a strong model fit. Thermal stability and fire resistance assessments revealed significant improvements in fire resistance, with a 22.52% decrease in weight loss, an 11.54% decrease in self-extinguishing time, and a 16.97% decrease in linear burning rate. These findings suggest that ESP enhances the degradation temperature, reduces weight loss, shortens flame extinguishment times, and improves flame retardancy, highlighting the potential for using eggshell waste in sustainable composite materials.

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