Journal of Research and Applications in Mechanical Engineering

Discretisation for Optimal Control of Nonlinear System with Noises

2025-04-16T20:57:43+07:00

This paper presents an optimal control framework for nonlinear systems with noise using Hamiltonian-based discretisation to enhance the approximation of stochastic differential equations. It employes the symplectic Euler method and Newton’s iteration, guided by Pontryagin’s maximum principle to solve implicit equations, incorporating Gaussian white noise into the Hamiltonian formulation of state and costate dynamics. Numerical simulations on the van der Pol oscillator and Lorenz system demonstrate the proposed method’s efficacy, achieving an average local truncation error reduction of 41% for the van der Pol oscillator and 1.1% for the Lorenz system, whilst reducing computational time by 27% on average for the Lorenz system, though often slower for the van der Pol oscillator. The method efficiently regulates noise, preserving dynamics, and minimising errors, contributing a robust numerical approach to nonlinear system control with advanced noise-handling capabilities.

CFD Analysis of the Thermal Hydraulic Performance of a Heat Exchanger Tube Utilizing a Combination of Different Inserts

2025-01-21T19:39:11+07:00

This inserts embedded heat exchanger tube is numerically investigated at a wide range of Reynolds number (Re) i.e. 4000-22000. The study examines the geometrical parameters of inserts, such as pitch, peg form length, and circular shaped inserts diameter. The smooth tube has a length of L = 1500 mm, an inner diameter of D_in = 37 mm, and an outer diameter of D_out = 42 mm. This model has been designed with multiple variations in ring diameters (d = 10, 12 and 14 mm) and peg leg lengths (l_p = 5, 6 and 7 mm), maintaining a constant arc, resulting in a seamless design of a smooth tube, ultimately referred to as the round peg-shaped HET. The width of the combined shaped inserts is represented as w_p = 37 mm, and the hydraulic diameter of the tube is Dh = 0.037 m, with pitch variations of round peg-shaped inserts P = 70, 90, 110 and 130 mm. The study displays the results of all modifications in these parameters. The CFD analysis of the RNG k-ɛ model, shows that heat transfer rate increases with Reynolds number. Nusselt number increases with pitch to hydraulic diameter ratio (P = 70 and 90 mm) and roughness variation. The highest Nusselt number is 209.3 for round peg leg HET. The friction factor is decreased with increasing Nusselt number and the lowest friction factor is achieved at 130 mm and d = 14 mm. These variations are pretended to enhance the thermal performance, and observed 329.53% increment of heat transfer as compared to smooth tube, and found maximum thermal performance of 2.2 at Re = 22000, d = 12 mm, l_p = 6 mm) and p = 90 mm.

Mathematical Modeling and Comparative Analysis of Stability in Internal Combustion Engine and Electric Vehicles

2025-04-16T20:33:59+07:00

With the increasing adoption of electric vehicles (EVs), understanding their stability characteristics compared to internal combustion engine (ICE) vehicles is crucial. This study investigates the impact of suspension tuning strategies on the stability of EVs, with a comparative reference to ICE vehicles. The analysis explores how mass distribution and control methods influence ride comfort and handling performance. A mathematical modeling approach is employed to examine how differences in mass distribution and suspension parameters affect vehicle stability. The results indicate that EVs experience lower ride comfort due to increased unsprung mass but exhibit improved road-holding capabilities. While EVs demonstrate greater roll stability at low frequencies due to a lower center of gravity, their yaw stability is less favorable, with increased deviations from the intended trajectory. To mitigate these drawbacks, a skyhook-damped semi-active suspension control strategy was implemented, improving ride comfort and handling stability. This study employs average parameters derived from 13 prior works to construct representative models of ICE and EV vehicles. As such, the findings highlight general trends rather than the behavior of any specific vehicle model. While the modeling approach effectively captures fundamental stability characteristics, further research incorporating nonlinear vehicle dynamics models and real-world experimental validation is recommended to enhance the applicability of these findings. Note that this study does not compare all possible ICE or EV configurations and is based on typical passenger car data; specialized ICE layouts such as boxer engines are not considered.

Numerical Simulation and Thermal Performance of a Novel Parabolic Solar Collector Panels

2025-04-18T16:33:44+07:00

This study investigates the design of a novel parabolic solar collector. It examines the effects of solar radiation on the collector panels and the flow characteristics of water through the system. The design incorporates two solar collector panels, each measuring 2×1.5 meters, with 2-inch diameter water pipes extending 11 meters in total. The parabolic panels have a focal point positioned 0.25 meters above the collector surface. A computational fluid dynamics (CFD) analysis was performed for flow rates of 0.25, 0.50, 0.75 and 1.00 liters per minute. The computational domain consisted of 1,520,000 mesh elements for analyzing solar thermal energy and 130,000 elements for simulating heat transfer from the radiation panels to the water within the pipes. The optimal flow rate was found to be between 0.50 and 0.75 liters per minute. The results show that the designed parabolic heat collector achieves maximum thermal efficiencies of 36.03% and 41.57%, respectively.

Mechanical and Thermal Characterization of Natural Composites for Sustainable Applications

2025-04-26T23:06:43+07:00

This study explores the development and mechanical characterization of sustainable hybrid composites reinforced with rockwool, conch shell powder, and flax fibers within an epoxy matrix. Two distinct composite formulations were fabricated: Rockwool/Conch/Epoxy (C-1) and Rockwool/Flax/Epoxy (C-2), each comprising 30 wt.% reinforcement (15 wt.% rockwool fibers and 15 wt.% conch powder or flax fibers) and 70 wt.% epoxy resin. The composites were produced using the hand lay-up method followed by compression molding. Comprehensive mechanical tests, including tensile and flexural strength assessments, were conducted in accordance with ASTM standards. Additionally, thermogravimetric analysis (TGA), water-absorption testing and scanning electron microscopy (SEM) were employed to evaluate thermal stability, moisture affinity, and microstructural characteristics. The results indicated that C-2 exhibited superior tensile and flexural strengths compared to C-1, attributed to the enhanced fiber–matrix bonding facilitated by flax fibers. Conversely, C-1 demonstrated better thermal stability but also higher water uptake, reflecting the porous, hydrophilic nature of conch shell particles. SEM analysis revealed effective dispersion of reinforcements and strong interfacial adhesion in C-2, whereas C-1 showed minor voids around conch particles. These findings highlight the potential of integrating natural and industrial waste materials to develop high-performance, eco-friendly composites with tailored mechanical, thermal, and moisture-management properties suitable for various structural applications.

Thermo-Mechanical Stress Analysis of a Linearly Functionally Graded Rotating Disk with Uniform and Tapered Cross Sections

2025-08-11T12:38:36+07:00

Functional gradation of materials in a component, whether metal-metal, metal-ceramic, or ceramic-ceramic, offers benefits such as high toughness and strength at elevated temperatures, which are desirable traits in rotating disks. With the advent of FGMs, isotropic material components began to be replaced. In the present study, Thermo-mechanical stress analysis on rotating disks was performed for isotropic materials (both metal and ceramic), and their results were compared with those of a linearly varying functionally graded (FG) disk. The approach utilized is the Variational principle, deriving the solution through Galerkin's error minimization method. Comparison plots of displacement, radial and tangential strains, as well as radial, tangential, and von Mises stresses, were presented to illustrate the advantages of advanced materials such as FGMs (functionally graded materials) over isotropic materials. The study reveals the benefits of functional grading of disks over those made of isotropic materials. Moreover, the analysis was performed for uniform as well as tapered disk profiles.

Numerical Prediction of Water Droplet to Investigate the Evaporation Process within Venturi Tubes Under Varying Pressure Conditions

2025-05-11T20:37:09+07:00

The evaporation of water droplets is influenced by various factors. Especially, pressure is a significant factor affecting the water droplets evaporation process. To study this phenomenon, the Computational Fluid Dynamics (CFD) for continuous phase flows, RANS 3D steady equations were solved in combination with the realizable k-Ɛ turbulence model. Lagrangian trajectory simulations of droplets evaporation was simulated by Discrete Phase Model (DPM) and species transport model. The evaporation time of 10-micron droplets under atmospheric pressure was determined through droplets simulation. Results from comparing the droplets evaporation time, show that the evaporation times for droplets within the tube under various pressure conditions (i.e. 0.5 bar - atmospheric pressure) were 0.05002 s - 0.08235 s. This represented a decrease of 11.52% - 39.26% of the evaporation time at atmospheric pressure. Furthermore, there was observed that the droplets evaporation time is shorter under low-pressure conditions, and decreasing air pressure enhances devolatilization in water droplets. This observation led to the simulation of a venturi throat with various throat sizes and pressure conditions. This study aimed to investigate the behavior of evaporating droplets in the venturi throat. According to the results, it was observed that reducing the diameter size of the venturi throat (0.1 – 1.0 meters) led to a decrease in the droplets evaporation times by 0.41% - 26.58%. In addition, it was noted that higher speeds airflow in venturi throat result in lower air pressure and evaporation time.

Evaluation of Conical Pin Fin Arrangements on Heat Sink Heat Transfer and Flow Characteristics

2025-06-13T22:10:06+07:00

This study experimentally evaluates the thermal and hydraulic performance of conical pin-fin heat sinks under varying airflow rates, power inputs, and fin spacing configurations. Four heat sink designs were fabricated from aluminum alloy 6061-T6 and tested in an open-loop wind tunnel. Key performance metrics, including the Nusselt number and apparent friction factor, were assessed across Reynolds numbers ranging from 10,480 to 23,900 and power inputs of 180, 285 and 480 W. Results indicate that the configuration with a longitudinal-to-transverse pitch ratio (R) of 1 achieved the highest thermal performance, enhancing the Nusselt number by up to 19.4% compared to other arrangements. In contrast, the R = 2 configuration exhibited the highest friction factor due to increased flow resistance. Experimental outcomes were validated using established correlations from Zukauskas, Colburn, and Jacob, showing strong agreement. These findings support the design optimization of heat sinks for efficient thermal management in electronic applications.

Reactive Gas Flows Fluctuations in Hydrogen Powered Wankel – Experimental Research using a Novel Flowmeter

2025-08-28T00:18:49+07:00

This paper presents experimental research of gas flow fluctuations on a two-rotor direct injected Wankel engine fueled with Hydrogen using special mass flow meter. The flow parameters of two reaction components - air and pure Hydrogen were measured at 9 engine operation points. The research of reacting gases fluctuations focuses on testing and measuring of Hydrogen pressure oscillation and intake air phenomena by means of air mass flow oscillation. For this purpose, a special orifice flow meter measurement system was developed to evaluate the intake-air performances under consideration of intake air pressures and engine temperatures. The experimental engine setup is discussed in the first part of the paper. Then, the H₂-direct injection stochastic behavior and intake flow fluctuations were measured and analyzed to explain the combustion phenomena and engine performance, which were compared with the experimental data. The investigation confirmed that the developed airflow measurement system can be applied to understand behavior of the H₂-engine and to improve the quality of the engine filling, combustion and resulting efficiency.

Energetic and Exergetic Analysis of Two-Phase Constant Pressure Ejector Used in Ejector Expansion Refrigeration System (EERS) Using Alternative Refrigerants

2025-09-14T21:08:24+07:00

The study explores an ejector expansion refrigeration system in which a constant pressure ejector is incorporated as expansion device in place of throttle valve used in conventional vapour compression refrigeration system. To identify the potential performance enhancement, an energy and exergy numerical analysis were conducted using five different refrigerant R134a, R1234yf, R1234ze, R410a and R152a as these are used in various domestic and industrial application. The novelty of this study lies in the application of energetic and exergetic analysis to a two-phase constant-pressure ejector in an ejector expansion refrigeration system using alternative refrigerants, which has not been adequately explored in previous literature. Coefficient of Performance, Exergy Destruction, Exergy Efficiency is evaluated from the mathematical model developed using Engineering Equation Solver (EES). R1234ze gives better performance as improvement in COP of about 10% to 28% is observed in Ejector Expansion Cycle (EEC) as compared to (BC). Also, Total Exergy Destruction decrement from 52% to 26% is estimated due to which exergy efficiency improvement decreases to 8% from 23% in an EEC as compared to BC, if evaporator temperature changes from 248K to 288K at constant condenser temperature of 318K.

A Systematic Exploration of the Role of Al₂O₃ Nanoparticles in CI Engines Fuelled with Co-Pyrolytic Bio-Oil

2025-04-18T15:10:50+07:00

The rising demand for sustainable energy solutions has prompted research into alternative fuels and advanced technologies aimed at enhancing engine performance and minimising emissions. Al oxide (Al₂O₃) nanoparticles' impact on performance and emission properties of compression ignition (CI) engines driven with co-pyrolytic bio-oil is investigated in this paper. Derived from biomass pyrolysed, co-pyrolytic bio-oil presents a renewable substitute for conventional diesel but suffers lower energy density and more emissions. Prominent for their catalytic and thermal characteristics, Al₂O₃ nanoparticles have showed potential in improving performance and lowering of hazardous emissions. Existing paper is compiled in this work to show the processes by which Al₂O₃ nanoparticles enhance engine performance and reduce emissions. Investigation also points up areas of research lacking and suggests potential paths for the integration of nanotechnology into biofuel uses.

Metallic Biomaterials in Biomedical Implants: A Review of Materials, Manufacturing Processes, and Emerging Trends

2025-08-04T05:36:53+07:00

Biomedical implants are artificial human-made devices designed to replace damaged hard tissues in the human body caused by fractures, accidents, diseases, and the natural effects of aging. Metallic biomaterials (MBMs) are commonly used in biomedical implants because of their excellent mechanical strength, stiffness, and durability. Consequently, the global demand for metallic biomaterials is growing rapidly and steadily, driven by the aging population and a rise in the incidence of injuries and diseases. This review highlights the various types of biomaterials and the processing methods used to fabricate medical implants from metallic biomaterials. It also highlights applications of biomaterials and machining processes. To encourage further research in this area, this review concludes with a summary and suggestions for future research.

Advancements in Fused Deposition Modeling: Materials, Processes, and Emerging Trends in Polymer Additive Manufacturing

2025-07-01T23:46:51+07:00

Fused Deposition Modeling (FDM) has become a leading technology in polymer additive manufacturing due to its versatility, cost effectiveness, and accessibility. This review explores the current advancements, material innovations, and emerging trends within FDM, particularly focusing on high performance polymers and composite materials. Key materials like PEEK (Polyetheretherketone), PEI (Polyetherimide), and PPSU (Polyphenylsulfone) are discussed in terms of their mechanical, thermal, and chemical properties, as well as their applications across industries such as aerospace, automotive, and medical devices. The incorporation of fiber and particle reinforced composites has significantly enhanced FDM capabilities, offering improved strength, rigidity, and thermal resistance for demanding applications. Moreover, the integration of Artificial Intelligence (AI) and the Internet of Things (IoT) is poised to revolutionize the FDM process by enabling predictive maintenance, and real time monitoring. However, challenges such as printability, cost, and material limitations continue to hinder broader adoption, especially for high performance composites and advanced materials. The review concludes by highlighting areas for future research, and material development, which are essential for unlocking the full potential of FDM in both prototyping and end use production.