Applied Mechanics and Materials Vol. 932

Abstract: The car’s performance improves with higher engine combustion efficiency. In this study, the volumetric airflow rate entering the intake manifold was significantly enhanced by replacing the stock air filter in the Cold Air Intake (CAI) system and integrating a valvetronic mechanism. The valvetronic regulates the air volume intake based on the vehicle's speed. The CAI design was evaluated by comparing the volumetric airflow rate per minute obtained from analytical calculation and flow bench prototype testing, considering three conditions: before re-design, after CAI implementation, and after adding the valvetronic. The results demonstrate a substantial performance gain with the valvetronic, achieving 38.35 hp and a maximum torque of 429.13 Nm. The intake system temperature sensor recorded a reduction of up to 3 °C in air temperature before the intercooler. This improvement can drive innovation in the automotive sector and contribute to achieving Sustainable Development Goals (SDGs) 9.4 and 12 by 2030.

Abstract: Several studies have investigated sloshing due to seismic excitation, mainly focusing on baffle effects and cyclic or recorded seismic loads. This study analyzes the seismic impact on an 80,000 m³ fuel storage tank in Tuban, East Java. Seismic events can cause fluid sloshing, increasing pressure on the tank walls and roof. Utilizing general-purpose finite element software, the sloshing phenomena are simulated using input dynamic loading in spectral response acceleration representing typical seismic loading per the Indonesian standard (SNI). It compares the traditional API 620 method with numerical simulations, revealing a 38% difference in sloshing height and a 40% difference in dynamic hoop stress. The numerical simulations predict a lower sloshing height due to unaccounted warm gas pressure, while the traditional method estimates less dynamic hoop stress. Although the API 620 method is more straightforward for design, numerical simulations provide a deeper understanding of sloshing pressure effects, enhancing asset integrity assessment.

Abstract: Underwater gliders rely on buoyancy-based propulsion for energy-efficient and long-duration exploration, yet the efficiency of pump-driven buoyancy engines in small-scale systems remains insufficiently understood. This study aimed to evaluate the efficiency, repeatability, and stability of a pump-based buoyancy engine for a scaled underwater glider. A laboratory-scale glider model equipped with a pump-driven fluid transfer system was constructed and tested under controlled buoyancy states. Key performance indicators included servo displacement time, fractional volume of displaced water, average velocity, buoyancy efficiency, and platform stability. Results showed a strong linear relationship between servo displacement time and displaced volume, confirming precise and repeatable buoyancy control. Increasing the displaced volume from 60% to 80% improved the average velocity by 33% and buoyancy efficiency by 41%. Stability analysis indicated that the glider maintained consistent pitch and roll angles during buoyancy transitions, although larger displacements induced greater fluctuations due to longer motor operation and hydrodynamic resistance. These findings demonstrate that optimizing displaced volume is essential to balance velocity and stability in small-scale designs. The study contributes novel experimental evidence on buoyancy-based propulsion and provides a foundation for future work on scalability toward larger gliders and longer-duration missions.

Abstract: The petroleum production process emphasizes the importance of inspection, analysis, test planning, and providing feedback on rotating equipment. This study discusses the analysis of steam turbine generator overhaul (OH) for efficiency enhancement at the power plant center of refinery unit. The efficiency of steam turbines in power plants is critical for optimizing energy conversion and minimizing operational costs. This study analyzes the impact of a steam turbine generator overhaul on efficiency at a refinery unit power plant. Efficiency was evaluated using Rankine cycle calculations, comparing performance data before and after the overhaul. The findings indicate a 2.63% increase in efficiency, with entropy-temperature analysis revealing energy losses due to scaling buildup and seal strip clearance deterioration. To maintain efficiency and reduce overhaul frequency, demineralized water quality, periodic maintenance, and anti-scaling treatments are recommended. These results highlight the importance of proactive maintenance in sustaining turbine performance and minimizing long-term costs.

Abstract: Offshore pipelines are crucial for transporting fluids from offshore platforms to onshore processing facilities. However, these pipelines are susceptible to damage from third-party activities, such as collisions with ship anchors. An inspection revealed a dent in the pipeline with a depth of 111 mm, resulting in a dent depth to outside diameter ratio of 31.21%. According to various regulatory codes, this ratio indicates failure. Despite this, no leaks or ruptures were observed during the inspection. To assess the pipeline's integrity, finite element analysis (FEA) using Abaqus was conducted to determine the maximum stress in the dented area. The analysis produced a graph illustrating the relationship between stress and the allowable operating pressure of the pipeline.

Abstract: Induction motors are critical components in various industrial applications. Any faults can seriously affect the production system. Therefore, early fault detection is essential to prevent such occurrences. This research aims to develop a fault diagnosis model for induction motors. Raw signal data were obtained experimentally in the laboratory using two identical three-phase induction motors. There are eight different conditions categorized into single-combined faults. 18 features were extracted from each signal, consisting of 12 time-domain features and 6 frequency-domain features. These features were selected using the minimum Redundancy maximum Relevance (mRmR) algorithm. The selected features were then used as input to build a model using the Discriminant Analysis. The results indicate that the Discriminant Analysis model achieved very high accuracy across all condition classes. The computation time of the developed model is exceptionally fast, even below one second. Quadratic Discriminant Analysis (QDA) proved to be more accurate than Linear Discriminant Analysis (LDA) in classifying faults data.

Abstract: Early fault diagnosis is a crucial element in maintaining the optimal operation of rotating machinery and avoiding sudden failure resulting in material and non-material losses. This research aims to select the salient features to diagnose the induction motor faults using an SVM model. The induction motor is simulated experiencing three fault scenarios: single fault, double faults, and multiple faults. These scenarios consist of stator fault, rotor fault, bearing fault, stator-bearing fault, stator-rotor fault, bearing-rotor fault, and stator-bearing-rotor fault. Vibration signals for each of these conditions are collected using an accelerometer sensor with a sampling frequency of 20 kHz. The study utilizes 12 statistical features, comprising 7-time time-domain features, namely mean, standard deviation, kurtosis, RMS, skewness, peak value, crest factor, and 5 frequency domain features, namely mean frequency, median frequency, spectral entropy, power spectral density, and spectral centroid. These features are selected using the ReliefF feature selection algorithm, and the selected features are then employed as classification parameters. The results indicate that the most relevant statistical features used for classification parameters are RMS, Standard Deviation, and Power Spectral Density. Meanwhile, the performance of the Support Vector Machine is excellent for three cases of the induction motor faults. The accuracies for single faults, double faults, and multiple faults are 99%, 100%, and 99% respectively.

Abstract: This paper presents an assessment of system collapse causes in Nigeria’s 132-330kV Grid. Long-term monthly data of system collapse incidences (SCI) from grid’s record was analyzed using statistical analytical procedures and adapted equations. Results established that the most probable cause of SCI is transmission grid faults at 81.6%, followed by generation faults at 13.2%, and lastly, intermediate faults at 5.2%. Furthermore, probability of non-occurrence of system collapse in a month is approximately 31%, which is low and an indication of fragile grid, requiring rigorous daily system planning, monitoring and control. Furthermore, the probability of at least 1 occurrence of SCI is also 31%, which is high and an indication that the grid is not safe from possible contingency that can result in total loss of the grid. Load loss impact of SCI is rated at an annual average of 20% for partial system collapse (PSC), while load loss would be 100% for total system collapse (TSC), implying huge costs on the national grid. These analyses indicate that the transmission network of Nigeria is most susceptible to faults that leads to SCI and needs to be investigated for specific vulnerabilities that can cause system instability and failure.

Abstract: Renewable energy sources (RES) offer outstanding attributes namely environmental-friendly and reduction in the cost of Grid system. Global power firm have embraced RES in generating electrical energy. RES, notably wind energy lessens electrical power losses on the network, nevertheless, RES incorporation into the network has adverse effect on the entire network. This research bequest critical investigation and comprehensive evaluation of reverse power flow (RPF)due to the outcome of vigorous and increased RES penetration to the Electrical Power Network. Matlab/Simulink Software is employed to carry out critical investigation on eight-bus electrical power network. The Matlab simulation was carried out with and without RES connection to the electric power network. Zones are employed for potent and effective investigation and evaluation of the network. The outcome of evaluation and analysis in sub-networks and the zones were carefully compared. The result show that RPF happens at all levels of electrical power networks, though, the penetration levels are not the same. It was revealed that RPF at the zone directly linked with the RES is higher compared with other zones.