Band 23, Heft 10

The various aspects of experimental rocket engine development, utilizing different fuels, including model studies, component-level tests, and simulated flight conditions, play an essential role in the Rocket propulsion system. The experimental development of a rocket engine or propulsion system depends on the design of the experiment. The challenges faced by classical hybrid rockets, their real-world importance, and potential mitigation methods, ensuring simplicity, cost-effectiveness, and safety without compromising their advantages. It aims to establish state-of-the-art sustainable technologies based on global findings, as most current technologies are still in early stages of commercialization. The development of a rocket engine and propulsion system depends on model studies, component-level tests, and system-level tests. When rocket engines and power plants are tested on the ground, specific techniques and equipment are used to ensure safety. Advanced hybrid rockets, which combine fast-burning fuels, composite motor construction, and innovative design, offer high performance while maintaining cost-effectiveness, environmental sustainability, and simplicity. Future space missions could be revolutionized by these technologies, requiring short-term investments that are green, safe, affordable, and high-performance. The effectiveness of Machine Learning (ML) models is contingent on the availability of high-quality training data, which can be a limiting factor in their application. Incorporating ML into existing engineering workflows poses challenges, requiring interdisciplinary collaboration and expertise.

Adsorption of carbon dioxide (CO 2 ) on shale formations is a viable strategy for improving methane (CH 4 ) recovery, crucial for maximising natural gas production and resolving environmental concerns about greenhouse gas emissions. Shale’s fine-grained sedimentary structure and high organic content make it ideal for CO 2 adsorption. This interaction can potentially boost methane extraction while contributing to carbon sequestration efforts. For the successful exploration of shale gas recovery, the gas adsorption mechanisms must be well understood. This article discusses the recent works on shale gas adsorption and their merits and demerits. The study of desorption behaviour is also critical to understanding the gas release behaviour, desorption hysteresis, influence of TOC, clay minerals, and presence of water on gas adsorption-desorption behaviour. For small-sized particle samples, the gravimetric method could be the best choice; however, the volumetric method is widely used for heterogeneous materials like shale rock. Adsorption processes are commonly analysed using a variety of isotherm models, including Langmuir, Freundlich, Brunauer–Emmett–Teller (BET), Dubinin–Radushkevich (DR), Temkin, Sips, Redlich–Peterson, Simplified Local Density (SLD) theory, and the Ono–Kondo model. These models have been developed through advanced theoretical approaches and empirical routes, enabling them to describe both generalised and specific gas adsorption phenomena. A powerful technique, molecular simulation – including Molecular Dynamics (MD) and Grand Canonical Monte Carlo (GCMC) – has recently emerged for investigating gas adsorption on shale at the microscopic level, offering deeper and more detailed insights into gas–shale interactions at the atomic scale.

This study explores the design and development of chemically modified epoxy nanocomposites reinforced with acid-treated pine needle (PN) fillers, aiming to enhance the mechanical and thermal properties of sustainable materials. The research examines the effects of nitric acid treatment on PN fillers, focusing on improvements in filler adhesion, surface roughness, and contaminant removal. Characterization techniques such as Fourier-transform infrared spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) confirm the chemical modifications and enhanced thermal stability of the treated fillers. FTIR analysis confirmed chemical modifications through enhanced C–O–C and reduced –OH absorption bands. The acid-treated fillers exhibited a density of 1,120 ± 43.42 kg/m 3 , confirming their suitability for lightweight applications. TGA results indicated improved thermal stability of the acid-treated fillers, with the onset of major degradation delayed from approximately 265 °C in untreated fillers to around 288 °C in treated fillers, and a higher residual weight observed at 600 °C. Epoxy nanocomposites were fabricated using precise filler-epoxy mixing, degassing, and curing processes. Tensile and impact tests, conducted according to ASTM standards, revealed significant improvements in mechanical properties, particularly tensile strength (TS) and impact strength (IS), influenced by filler weight, ultra-sonication time, and degassing time. Response surface methodology (RSM) and analysis of variance (ANOVA) were employed to optimize the composite synthesis process, yielding an optimized composite with a TS of 60.85 MPa and an IS of 14.67 kJ/m 2 . The optimized composite exhibited a 25 % increase in TS and a 30 % increase in IS compared to neat epoxy. These findings highlight the potential of acid-treated PN fillers in producing high-performance, eco-friendly composites for automotive, aerospace, and construction applications. Future work will explore further optimization and real-world performance testing of these composites.

While scramjets offer promising advantages such as reduced mechanical complexity and high thrust-to-weight ratios, their performance is severely constrained by extremely short residence times for fuel-air mixing and combustion. Efficient flame stabilization and rapid mixing remain two of the most critical challenges in this domain. One of the most effective methods to address these challenges involves the use of strut-based fuel injectors, which simultaneously deliver fuel and promote turbulence through shock wave interactions and vortex formation. However, the performance of these injectors depends heavily on their geometric configuration. This current study presents a comprehensive computational fluid dynamics (CFD) study aimed at evaluating the impact of backward-facing strut injector design parameters, including tip angle, step height, and spacing, on shock wave structure, mixing efficiency, and combustion characteristics in a scramjet combustor operating at Mach 2.5 with hydrogen fuel. The simulations are conducted using ANSYS Fluent with a density-based solver, incorporating the SST k–ω turbulence model and a Finite-Rate Eddy-Dissipation (FRED) chemical reaction model. High combustion efficiency was observed, increasing from 98.5 % at Mach 2–99.9 % at Mach 3.

This study simulated gas flow in oil droplet-gas cyclones using the Reynolds stress turbulent model incorporated into the CFD code Ansys-Fluent. Five cyclone body designs, namely, cylindrical, square, octagonal, hexagonal, and inverted cone, were analyzed to determine their effect on gas flow patterns. The inverted cone geometry had a greater maximum tangential velocity, roughly 1.6 times the inlet gas velocity. In contrast, the square geometry had the lowest maximum axial velocity of 0.36 times the inlet velocity. The inverted cone cyclone showed the highest number of floating droplets, whereas the square cyclone yielded the least. Overall, the square shapes showed better performance than other shapes. The developed computational model accurately estimated droplet behavior, with its predictions closely matching the experimental data. Therefore, it is well-suited for simulating oil droplet motions in gas cyclones using CFD.

Hydrogen has emerged as an important component in the global transition to sustainable energy systems due to its ability to decarbonize multiple sectors while facilitating energy storage and transfer. However, achieving large-scale hydrogen generation faces several hurdles, including technological inefficiencies, high costs, and limited infrastructure, which vary by region. This research examines the global challenges of hydrogen production, with an emphasis on technological, economic, and legislative limitations. It also highlights Saudi Arabia’s significant potential to become a global leader in hydrogen production, owing to its vast renewable energy resources, strategic location, and ambitious investments in hydrogen technologies. The study reviews the use of hydrogen in the aviation sector and its integration into various applications. It covers scenarios where hydrogen can serve as the primary energy source (fuel) instead of kerosene, compares their performance, and discusses the main challenges associated with using hydrogen – either as a gas or liquid – as fuel. It also addresses electricity generation through different types of fuel cells for applications onboard aircraft (auxiliary power units) and at airports (ground support equipment). Furthermore, the research explores the implementation of solar hydrogen panels in various regions and assesses their potential benefits in Saudi Arabia. The study highlights the operational principles, economic impacts, and environmental advantages of this innovation by reviewing case studies from Europe, Asia, the Americas, and the Middle East. Key results and data are presented, providing insights into efficiency improvements and cost reductions. Finally, the research concludes by outlining how Saudi Arabia’s solar potential and strategic initiatives can leverage solar hydrogen panels to enhance energy diversification and sustainability. By addressing the identified challenges, Saudi Arabia can not only strengthen its energy security but also play a pivotal role in developing the global hydrogen economy.

In this paper, efforts have been made to identify the flow regimes and their transitions using pressure signals and optical probe signals in millichannels of diameter 4.2 mm. Observations are first made through high-speed videography, and then voltage signals from the optical probe and pressure transmitter are used to identify the different flow regimes. A statistical approach, the probability density function (PDF), has been used to analyze the signal data and draw conclusions about the flow regimes. Results show both methods are very effective in detecting flow regimes in non-transparent pipes. Both the pressure and optical probe methods show high potential for flow pattern recognition.

Glass fiber raw material mixing directly affects glass melting efficiency, fiber forming quality, and final product performance. Understanding the mixing process supports pneumatic homogenizer optimization and improvements in efficiency and uniformity. In this study, a coupled computational fluid dynamics-discrete element method (CFD-DEM) was used to simulate the mixing of glass fiber raw materials (pyrophyllite, 70 μm; limestone, 80 μm) in a pneumatic homogenizer under two nozzle configurations: without horizontal nozzles (Case 1) and with horizontal nozzles (Case 2). Engineering-scale similarity was employed in the model to reduce computational cost while preserving dynamic fidelity. Results showed that at a specific location ( Z  = 1.0 m and X / m  = 0), axial gas and particle velocities in Case 1 (−9.46 m/s; −5.76 m/s) were lower than in Case 2 (−16.12 m/s; −8.74 m/s). The Lacey Mixing Index fluctuated around 0.83 in Case 1, clearly below Case 2 (0.90); particle visualization further revealed noticeable agglomeration in Case 1. The airflow velocity field strongly governs particle motion and mixing efficiency: entrainment forms a fountain-to-wall recirculation that controls particle trajectories. The horizontal jet inlets effectively enhance the mixing behavior between particles at the bottom and upper regions of the pneumatic homogenizer, providing a reliable theoretical basis and technical support for optimizing the mixing process of glass fiber raw materials.

This study aims to develop a kinetic model for the hydrolysis reaction of soybean oil based on experimental data. The development of studies involving the estimation of kinetic parameters of mechanistic models is fundamental for greater precision in controlling the desired product. A kinetic model for triglyceride hydrolysis is essential to optimize biodiesel production, improving efficiency and cost of industrial production. It must overcome the challenges of reversible reactions and limited kinetic data to enable better process control. The model describes the initial phase of biodiesel production via the hydroesterification process, involving hydrolysis of oil into FAtty acids and glycerin, followed by esterification of the FAtty acids into biodiesel and water. Experiments were conducted in a pressurized stainless-steel reactor with sampling throughout the reaction. Conditions included temperatures of 200, 230, and 250 °C, a 1:1 water-to-oil volumetric ratio, and 1 % H 2 SO 4 by weight as a catalyst. Reaction conversion was determined by titration, and molar fractions of reactants and products were calculated. A kinetic model for the hydroesterification reaction was proposed, assuming that the different steps for the production of FAtty acids and glycerol had forward and reverse reaction rates, which were solved using the Dassl subroutine. Thus, expressions for the consumption rates of the reactants and byproducts were derived. The obtained solution was compared with the experimental data to estimate the Arrhenius constants. Furthermore, the influence of temperature on hydrolysis was assessed by calculating the pre-exponential FActor and activation energy. The estimated pre-exponential FActor were 1.02·10 7 min −1 , 5.20·10 2 min −1 , 1.60·10 3 min −1 and 7.55·10 5 min −1 while the values for activation energy were 89.283 kJ mol −1 , 15.795 kJ mol −1 , 37.071 kJ mol −1 and 44.208 kJ mol −1 . The proposed model effectively described the kinetics of the hydrolysis reaction.