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.
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.
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 .
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 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.
Parametric study on the effect of venting performance of savonius turbines for hydrokinetic applications
(2023-09-01)
Abu Bakar, Nurul Asyikin
Renewable energy has become increasingly significant in Malaysia particularly with the utilization of hydrokinetic energy to generate electricity from rivers and streams. However, despite the advantages of its simple design and compact size, the efficiency of the Savonius turbine is limited by negative torque. To address this issue, researchers have explored improvements such as incorporating vented blades that minimize the negative torque produced by returning blades. These efforts have predominantly focused previously on the elliptical Savonius blade rather than the conventional blade. Therefore, the investigation into optimized vent configurations for conventional blades remains scarce. This study aims to parametrically investigate the effects of various vent configuration parameters particularly on position, width and height, on the performance and flow structure of a Savonius turbine operating at a Reynolds number of 148 000. The finding reveals that variations in vent height have greater impact on turbine performance compared to vent position and width. The H3 turbine exhibits the highest performance of CP = 0.1520 with a 16.95% improvement over the conventional Savonius turbine achieved by utilizing an optimal vent configuration of 45 ° position, a width of 0.011 m, and a height of 0.071 m, resulting in a substantial increase in net torque. The top view flow visualization reveals a closer recovery flow behind the advancing blade in the H3 turbine, contributing to the enhanced net torque. The side view flow structure demonstrates a smaller wake size downstream, indicating the effectiveness of the H3 vent configuration in reducing excessive turbulence on the returning blade, thereby increasing the power coefficient. In conclusion, this study provides a comprehensive insight into the influence of different vent configurations on the performance and flow structure of Savonius turbines. The findings help to establish and contributes valuable knowledge for future applications in sustainable power generation systems, highlighting the importance of optimizing vent parameters to enhance turbine efficiency and overall performance.
Performance study of conventional savonius hydrokinetic turbine with two flat deflectors
(2022-03-01)
Salleh, Mohd Badrul
Hydrokinetic turbines (HKT) have great potential for providing sustainable energy. Savonius HKT is considered the best option for low-cost applications due to its simplicity and ability to operate under low flow rates. The deflectors have been shown to improve the low performance of the turbine. However, the use of two deflectors for a conventional Savonius HKT, particularly in flows with low and varying speeds is still lacking. This research aims to improve the performance of the conventional Savonius HKT by incorporating two flat deflectors. The power performance of the turbine was investigated in a wind tunnel with respect to three deflector parameters: angle, longitudinal position, and height. First, the turbine performance was evaluated on 2-bladed and 3-bladed turbine models with 30 combinations of the deflector angles of the advancing and returning blades, 𝛿𝐴 and 𝛿𝑅, respectively at 7.0 m/s airflow speed (equivalent water flow speed of 0.40 m/s). The better-performing 2-bladed turbine model was then selected for further investigation on 9 combinations of the deflector longitudinal positions of the advancing and returning blades, 𝑋𝐴⁄𝑅 and 𝑋𝑅⁄𝑅, respectively, followed by 3 different deflector heights: 0.5𝐻, 1𝐻, and 1.5𝐻. The experiments on the 2-bladed turbine were then repeated at various Reynolds numbers, 𝑅𝑒 ranging from 9.27 × 104to 1.48 × 105. The flow patterns surrounding the 2-bladed turbine were visualized using smoke generators to provide additional insights into the flow behaviors across various deflector configurations. The wind tunnel results were validated (within the experimental errors) by testing the 2-bladed turbine in a water channel for the same parametric variations of the deflectors with dynamically similar flow conditions. The maximum coefficient of power, 𝐶𝑃𝑚𝑎𝑥 of the 2-bladed turbine model with the two deflectors was 14% higher than that of the 3-bladed turbine. The 2-bladed turbine model exhibited the highest 𝐶𝑃𝑚𝑎𝑥 of 0.210 with 61.54% improvement relative to that of the turbine without the deflectors at the optimal deflector angles of 𝛿𝐴 = 30° and 𝛿𝑅 = 90°. The 𝐶𝑃𝑚𝑎𝑥 was further increased to 0.261 with 100.77% improvement at the optimal deflector longitudinal positions of 𝑋𝐴⁄𝑅 = −0.500 and 𝑋𝑅⁄𝑅 = −1.204, and at the optimal deflector height of 1𝐻. These optimal deflector configurations remain unchanged as 𝑅𝑒 increases, regardless of the increment in the turbine performance. In-depth investigation using flow visualization revealed that the deflector configurations influenced the surrounding flow patterns but were independent of variations in 𝑅𝑒. Optimizing the deflector configurations effectively directed the flow towards the advancing blade while preventing it from impinging on the returning blade, resulting in an increase in the positive net torque and thus the performance of the turbine. Findings from this research demonstrated the efficacy of using two flat deflectors in solving the problem of low power performance of the conventional Savonius turbine.
Ranking - gradient – similarity multi - block matching algorithm for stereo vision
(2020-10-01)
Kok, Kai Yit
Various research has been conducted on the development of stereo vision whereby the local approach, the global approach, and the convolutional neural network (CNN) approach have different pros and cons. Nevertheless, the local approach still outperforms the others in terms of simplicity and computation cost, generally. Therefore, a new local block matching algorithm known as Ranking-Gradient-Similarity Multi-Block (RGSMB) has been proposed in this research work. This algorithm developed to resolve the accuracy issue of the local approach. A new cost computation has been introduced in the proposed algorithm, which fully utilizes the information from the limited local window region by combining the cost from three different constraints, including a Ranking constraint, a Gradient constraint, and a Similarity constraint. The performance evaluation of the RGSMB was done using the Karlsruhe Institute of Technology and Toyota Technological Institute (KITTI) dataset. A total number of 200 image pairs are used in the parameter optimization analysis to find the optimum parameter settings of the RGSMB for stereo vision. Performance comparison with other local approaches carried out has substantiated the superiority of the RGSMB. The proposed algorithm achieved the lowest average errors with moderate computational cost in comparison with the tested algorithms. It is also compared with recent CNN approaches using both KITTI 2012 and 2015 datasets to justify the capability of the RGSMB further. In this comparison, the RGSMB can outperform the CNN approaches with fewer disparity errors. This comparison indicates that the RGSMB exhibits excellent potential for stereo vision. Next, RGSMB is tested experimentally by implementing the algorithm on the StereoPi system. With appropriate strategies of increasing computational efficiency, the RGSMB can achieve near to 2.5 frames per second using a low-cost hardware system. Hence, a new local approach with satisfying accuracy and performing in real-time is developed in this research.
River feature morphology using k-means clustering in image segmentation of uav imagery
(2022-06-01)
Iftekar, Ansari Emaad
In Malaysia, flood disaster is considered to be an annual catastrophic disaster due to their consistent occurrence over the years. In this regard, flood hazard assessment models play a significant role, as they form the central component of the flood risk analysis system. With the expeditious evolution of computer techniques, processing of satellite and unmanned aerial vehicle (UAV) images for river hydromorphological feature detection and flood management have gathered pace in the last two decades. Different image processing algorithms and artificial neural networks were implemented in past studies for the monitoring and classification of river features. This study presents the application of the K-means image segmentation algorithm with image thresholding to quantify variation in river surface flow areas and vegetation growth along Kerian River, Perak, Malaysia. The river characteristic recognition directly or indirectly assisted in studying river behaviour and flood monitoring. Dice similarity coefficient (DSC) and Jaccard index were numerated between thresholded images that were clustered using the K-means image segmentation algorithm and segmented images. Based on the quantitative evaluation, a Dice similarity coefficient and Jaccard index of up to 97.86% and 94.36% were yielded for flow area and vegetation calculation. Thus, the proposed technique was functional in evaluating river characteristics with reduced errors. With minimum errors, the proposed technique can be utilized for quantifying agricultural areas and urban areas around the river basin. Regression analysis of suspended sediment concentration and Hue Saturation Value (HSV) color space components of UAV captured river surface images were also performed in the proposed study. It was concluded using various statistical test that the correlation between the suspended sediment concentration and HSV components of UAV captured river water surface images were non-linear. Furthermore, non-linear correlation analysis would be needed in future for obtaining an accurate relationship between the suspended sediment concentration and HSV components of aerial images.
Thermal impact of thermal interface materials and heat spreader co-planarity of the electronic packaging
(2020-06-01)
Pang, Shi Shiang
This thesis presents the thermal impact of thermal interface material 1 (TIM1) and heat spreader co-planarity to the flip chip package with heat spreader. The TIM1 material influences the efficiency of heat transfer from silicon die to the heat spreader while the co-planarity of heat spreader affects the thermal performance of the flip chip package significantly, especially on the junction-to-case thermal resistance of the package. Numerical studies using ANSYS Icepak were conducted to investigate the thermal impact contributed by the TIM1 material properties and thermal degradation due to heat spreader co-planarity in either concave or convex with deflections up to 0.12 mm. The result indicated that the bond line thickness (BLT) and the thermal conductivity of the TIM1 material affected the thermal performance of the flip chip package. The result also showed that with concave deflection improved up to 44 % while convex deflection degraded up to 80 % of the junction-to-case thermal resistance of the flip chip package. The outcome of the study is to propose design guidelines and recommendations for TIM1 material selection and implementation. Higher thermal conductivity and lower the BLT of TIM1 material shall be selected for better thermal performance of the flip chip package. The findings also recommended the co-planarity tolerance for the heat spreader shall not be greater than 0.07 mm for a 60 mm x 60 mm flip chip package with a heat dissipation of 150 W.
Three dimensional computational modelling of biofuels combustion characteristics and its effect on turbine blade structure
(2022-05-01)
Sim, Sing Mei
Biofuel has been identified to reduce pollution generated by an aircraft engine. This study is conducted to assess 1) biofuels combustion characteristics and 2) biofuel hot combustion gases effect on turbine blade structure at take-off, top of climb and cruise. The biofuels chosen in this study are Jatropha Bio-synthetic Paraffinic Kerosene (JSPK) and Camelina Bio-synthetic Paraffinic Kerosene (CSPK). The fuels were evaluated as pure (100%) and blend (50%) with Jet–A. The assessments were performed computationally via Computational Fluid Dynamic (CFD) and Fluid Structure Interaction (FSI) available in ANSYS. A comparison of combustion characteristics namely d2 law and penetration length of biofuels with Jet–A through the incorporation of fuel properties and actual combustor inlet data at various flight trajectories is obtained. The usage of biofuels in combustion provides up to a 15% maximum temperature reduction, and up to 83% reduction in penetration length. JSPK consumes less fuel and has better evaporation rate while producing similar thrust with Jet-A. JSPK has least improvement of fatigue life cycles due to consistent combustion characteristics with Jet-A. CSPK shows the highest improvement in fatigue life cycle during take-off and cruise due to lower temperature at the turbine inlet, thus lower stress and strain at the turbine blade section are obtained. The study generally indicates a correspond relation on temperature effect between combustion and turbine blade. The trend might contradict for a particular evaluation due to the dependency on the boundary condition that correspond to the properties of the fuel tested.

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