International Journal of Engineering Research in Africa Vol. 74

Abstract: The processing of metallic materials alone has a huge impact on resource utilization, emission, and waste generation. With the emergent ecological concerns, there is a solid thrust towards sustainable materials development. Sustainable metal matrix composites are designed to minimize environmental impacts by reducing resource consumption and energy usage and curbing waste generation. Now a days, the automotive sector is making significant strides towards a more ecological product chain by adopting sustainable reinforcements such as basalt fibres, red mud reinforcements, fly ash, cenosphere particles etc. into matrix material which significantly influence the mechanical properties. With this perspective, the present work is aimed to investigate the hardness, tensile, flexural, impact and wear characteristics of 7075 reinforced with different combinations of B4C, egg shell particles along with fly ash. The results revealed that the best mechanical and wear are measured at 3 % boron carbide, 3 % Egg shell powder and 2 % fly ash reinforced AA-7075 composite among the other developed composites. The results thus suggested that the incorporation of sustainable reinforcements along with ceramic reinforcements offer enhanced material characteristics, cost savings and environmental advantages.

Abstract: In developing an accurate modelling technique of thermal profile parameters when welding High-strength steel, an algorithm based on an artificial neural network (ANN) for predicting cooling time using Gas Metal Arc Welding (GMAW) was set up. The neural network developed has a 4-20-1 architecture with the input parameters of the voltage of the station (U), welding current intensity (I), welding speed (V), and heat input (Q) with the output parameter Cooling time (∆t8/5). A protocol has been developed with the MATLAB R2020a software containing three neural networks. The goal was to determine the neural network that has the lowest root mean square error (MSE). The results showed that the first system produced an MSE of 1.295 × 10⁻³ and a regression R = 0.995 with a Relative error of 0 for 8 of the initial 14 data. The second system produced an MSE of 4.278 × 10⁻³ with a regression R = 0.978 with 11/15 showing an error of 0. Finally, the third system, consisting of associated experimental data to the analytical data produced an MSE of 2.506 × 10−3 with a regression R = 0.972 with a slight difference between the input data and predicted data on all 29 points. The results obtained by the first two systems are satisfactory and developed neural networks can be found reliable for predicting cooling times of welded joints of steel high-strength.

Abstract: The thermal swing adsorption process has been demonstrated as a promising technology for the biogas upgrading process, with ease of integration into renewable electricity sources. This study examined the influence of particle radius, regeneration temperature, and purge-to-feed flow rate ratio on the biogas upgrading process. A dynamic simulation model was developed to study the carbon dioxide capture process. Activated carbon pellets derived from coconut shells were used as the adsorbent material. The adsorption and desorption processes were based on single-component methane and carbon dioxide adsorption isotherms fitted to the Langmuir-Freundlich model. The developed simulation model was validated against experimental data. A particle radius, regeneration temperature, and purge-to-feed flow rate ratio range of 1 to 9 mm, 77 to 227 °C, and 0.1 to 0.7, respectively, were adopted for the parametric analysis. Multi-objective numerical optimization was performed using the response surface methodology. The results indicated that the purge-to-feed flow rate ratio had the highest contribution to the methane purity and recovery models of 92.37 % and 99.90 %, respectively. The optimal methane purity and recovery values obtained were 82.12 % and 37.21 %, respectively, achieved at a particle radius of 9 mm, a regenerating temperature of 227 °C and a purge-to-feed flow rate ratio of 0.4152.

Abstract: Water shortage is a major global issue affecting the construction industry. One possible solution is to use seawater instead of tap water in cement-based materials. However, this raises concerns about the impact on material properties. In addition, it is known that the use of volcanic pumice powder in cement mortar can improve its properties, but the combined effects of seawater and volcanic pumice powder have not been thoroughly investigated. This study aims to fill this gap by investigating the synergistic effects of seawater and volcanic pumice powder on the slump flow, compressive and flexural strengths, water absorption, and fracture toughness of cement mortar. The main variables in this study are the type of water (Mediterranean water and tap water) and the percentage of volcanic pumice powder (VPP). The volcanic pumice powder content is 0%, 10%, 20%, and 30%, replacing cement by mass. Based on investigation results, it was shown that the combination of seawater and volcanic pumice powder leads to less fluid and more viscous mortars compared to those made with tap water (TW). However, in the hardened state, seawater promoted the early precipitation of cement hydration, resulting in an increase in compressive strength from the second day until 28-days, along with an improvement in the transport properties of mortar at 28 days. Meanwhile, a noticeable decline in both strength and fracture toughness was recorded for ages more than 28 days and up to 90 days, compared to mortars cast and cured with tap water.

Abstract: Integrated water management aims to promote water supply from conventional resources and wastewater reuse to address issues such as water scarcity. The positive input from collecting and reusing water for household purposes has not often seen assessments of the impact of climatic change, water resource availability, and water deprivation in various regions. If the water resource comes from a clean water resource and was first used to wash or bathe, it is commonly referred to as greywater. GW is an abundant resource generated throughout people's daily lives. GW can be used for domestic cleaning, flushing toilets, washing vehicles, washing kitchen gardens, washing clothes, and washing before rinsing. This research study aims to develop an experimental system for GW treatment with the optimum cost and reuse it in landscape facilities. The main result showed achieving a suitable design for GW, which improves the water's characteristics and quality so that it is suitable for use in landscaping agriculture, at a total cost of 15.6 $ to effluent discharge water amount of 1.75 m³/h. This study showed that the presented experimental study, which uses a conventional treatment process built with existing systems, can achieve satisfactory results of GW treatment. The turbidity was reduced with an effectiveness rate of 96% and a filtration efficiency of 96.5% for TSS, particularly in filtration by a mixture of screen filter and gravel filter.

Abstract: Ethiopia’s agriculture, which is mainly rainfed and managed by smallholder farmers, faces significant productivity challenges due to limited rainfall during a short rainy season. Solar-powered water pumping offers a sustainable and efficient alternative for dry-season irrigation by harnessing the country's abundant solar energy potential. This study presents a novel approach to optimizing solar-assisted water pumping systems by evaluating the hydraulic and electrical performance of both centrifugal and helical rotor pumps under varying flow rates and solar irradiance levels. The findings indicate that system efficiency peaks at specific heads depending on solar irradiance: at 450 W/m², a head of 16 meters achieves 33% efficiency; at 750 W/m², a head of 20 meters yields 34%; and at 950 W/m², a head of 28 meters achieves 32% efficiency with a centrifugal pump. Notably, the helical rotor pump demonstrates superior performance for applications requiring consistent pressure at low to moderate flow rates. This study provides valuable insights into the head-flow relationship, optimal operational conditions for various solar irradiance levels, and comparative performance metrics of different pump types, offering practical guidelines for enhancing the efficiency of solar-powered irrigation systems.

Abstract: Fretting wear primarily impacts the bushing of the con-rod, subsequently influencing the con-rod's overall performance. In this investigation, the contact interactions between the con-rod small end, the small end cover, and the bushing under conditions of utmost combustion pressure were investigated. This analysis included examining the contact pressure and friction stress distribution. Subsequently, an orthogonal simulation test was developed to further investigate these interactions. The study took into account the friction coefficient of the interface and the quantity of interference as test factors based on contact mechanics theory. The objective functions were the utmost friction stress and contact pressure, ascertained under conditions of peak combustion pressure. Based on the findings from this study, the contact pressure of the top portion of the bushing is lower than that of the bottom portion. The friction stress of the top portion of the bushing is larger than that of the bottom portion. The optimal values for the interference amount and friction coefficient are 0.11 and 0.15, respectively, which will result in the most favorable conditions for minimizing fretting wear in the bushing.

Abstract: The availability of electrical energy is essential for human progress and economic development. Renewable energy solutions, including waste-to-energy (WtE) systems, present sustainable alternatives but require advanced control strategies for optimal performance. This research aims to enhance the control of drum level, temperature, and pressure in WtE steam boilers at Ethiopia's Reppie power plant. The existing Programmable Logic Controller (PLC) system is limited in its ability to predict future states and handle nonlinear system behaviors. To overcome these challenges, a Radial Basis Function Autoregressive with Exogenous input (RBF-ARX) model was developed and integrated with a Model Predictive Controller (MPC). The results demonstrate that the MPC approach significantly surpasses the performance of the Linear Quadratic Regulator (LQR) in terms of control efficiency. For temperature control, the MPC achieves a settling time of 0.3955 seconds and a rise time of 0.0195 seconds, compared to LQR's 5.99 seconds. Similarly, for pressure control, the MPC achieves a settling time of 0.6678 seconds, outperforming the LQR's 12.507 seconds. Drum level regulation further showcases the superiority of MPC, with a settling time of 0.5223 seconds versus the LQR's 8.302 seconds. This proposed RBF-ARX-based MPC framework not only optimizes control efficiency at Reppie but also demonstrates scalability and applicability to other WtE plants, enhancing operational performance under varying conditions. MATLAB/Simulink was used for the modeling and simulation, confirming the robustness of this approach for global adoption in WtE systems.

Abstract: This study introduces a novel methodology to determine the effective area of artificial tree camouflaged telecommunication towers, focusing on the pine tree type, using drone technology and photogrammetry. Accurate frontal area determination is essential for wind load calculations, critical to the structural design of such towers. Conducted on a telecommunication tower in East London, South Africa, the research applied image thresholding to point clouds generated from drone-captured images. The drone-derived frontal area of 23.484 m², when combined with a force coefficient of 0.5 from previous wind tunnel research, resulted in an effective area of 11.742 m², differing by less than 4% from the in-situ strain-derived effective area of 12.10 m² utilized as verification. The study addresses the lack of guidelines for designing camouflaged towers and highlights the advantages of drone technology over traditional methods. The results suggest a 47% reduction in the original design's effective area, leading to a 20% reduction in bending moments at the telecommunication tower base. This can result in cost savings by reducing the required structural capacity in future designs or increasing antenna space, which is crucial for 5G deployment. The research offers a practical solution to optimize existing telecommunication towers' capacity, improving efficiency without requiring new infrastructure.