Mechanical Engineering Advances

Traffic-based methodology to develop peak Heat Release Rate probability distributions for sizing road tunnels ventilation systems when using a probabilistic approach

2025-04-02T02:32:18+00:00

Road tunnels are a crucial part of today’s transport infrastructures worldwide. Among the installed systems, the tunnel ventilation is key, as in the case of fire, it establishes and keeps appropriate conditions for self-evacuation and emergency services operations. Recent works propose using a probabilistic approach to assess road tunnels ventilation systems’ capacity for fire scenarios. Under this approach, key design variables are defined based on probability distributions. From these distributions, the analysis uses the different possible values of the variables, including lower and upper limits as well as mean and characteristic values. The results obtained with this proposed probabilistic approach allow not only designers, but also tunnel operators and administrations, to quantify the reliability of the capacity of the ventilation system, assess its probability of failure, and define safety levels. This paper illustrates a methodology to define the design fire as a probability distribution for sizing road tunnels ventilation systems when applying the above-mentioned probabilistic approach. The methodology uses traffic information (crucial in road tunnels) and correlates it to peak Heat Release Rate (HRR) values from published reports by PIARC to obtain the design fire variable in terms of peak HRR probability distributions. The methodology is applied to two case study tunnels with different characteristics. The obtained results for the two tunnels are then compared and analyzed to peak HRR values normally recommended and used when sizing road tunnels ventilation systems to understand the uncertainty and sensitivity of the results.

Effect of inverse-square heat absorption on MHD natural convection flow in a vertical concentric annulus with radial and induced magnetic fields

2025-04-03T01:09:41+00:00

This study investigates the impact of inverse-square heat absorption on steady, fully developed laminar MHD natural convection flow within an infinite vertical concentric annulus under the influence of applied radial and induced magnetic fields. The governing transport equations in the model were transformed into a non-dimensional form, allowing for the derivation of unified analytical solutions for the velocity, temperature, magnetic field, and induced current density distributions for both isothermal and iso-flux on the inner cylinder of concentric annuli. The influence of key physical parameters in the model is illustrated through a comprehensive analysis of graphs and tables. The findings reveal that increasing the heat absorption parameter intensifies thermal gradients near the inner cylinder, while stronger magnetic fields suppress fluid motion, reducing mass flux and enhancing flow resistance. Mass flux and induced current density decrease as Hartmann number and heat absorption parameter increase, demonstrating the combined influence of thermal and electromagnetic forces. The magnetic field distributions and associated current densities exhibit pronounced attenuation near the inner cylinder under a higher Hartmann number. These findings highlight the intricate interaction between thermal and electromagnetic forces, offering valuable insights for applications in nuclear reactors, MHD power generation, and advanced cooling technologies. This study contributes to refining MHD-driven thermal management approaches for Advanced engineering systems.

Design method for intelligent robots applied to traditional CNC processing plants: An integrated system based on mechanical, circuit, and image recognition technologies

2025-04-07T02:05:52+00:00

This study aims to design an automated production assistance device for small to medium-sized traditional CNC factories. The goal is to provide a cost-effective auxiliary production tool that integrates seamlessly into existing machining environments. The design encompasses mechanical, circuit, and software components. Mechanically, the device features a robotic arm equipped with a camera for object recognition and gripping, utilizing real-time image processing to enhance efficiency and stability. The circuit design employs embedded devices and microcontrollers to create a low-power, high-performance control system that manages motor drive, sensor data collection, and image recognition. On the software front, the system uses OpenCV and You Only Look Once (YOLO) for object detection and identification to tackle complex industrial scenarios. The design also considers economic feasibility, making it suitable for effective application in small and medium-sized enterprises. Through detailed theoretical analysis and multi-stage system simulations, the intelligent robot system has been thoroughly validated for overall stability and practicality. The final product is an intelligent self-propelled cart with capabilities, supporting efficient automated production and the intelligent upgrade of traditional manufacturing industries. Such a system is expected to significantly enhance production line efficiency in variable environments, reduce reliance on manual labor, and promote the intelligent transformation of traditional factories.

The SG6043 airfoil optimization for low Reynolds number applications in wind turbines

2025-04-08T02:11:36+00:00

This study focuses on optimizing the SG6043 airfoil for small wind turbines (SWTs) operating at low Reynolds numbers (Re = 100,000 to 600,000). Using XFOIL software, 71 airfoils were analyzed, and the SG6043 airfoil demonstrated the highest lift-to-drag ratio (C_L/C_D). Three modified airfoils were designed by varying the thickness-to-camber ratio (t/c) between 0.5 and 1.5. The SG6043 modified 1 airfoil achieved a maximum C_L/C_D of 184.85 at Re = 600,000, outperforming other airfoils. These findings provide valuable insights for designing more efficient SWTs for low wind speed applications. At first, 71 airfoils, including some symmetrical National Advisory Committee for Aeronautics (NACA) 4-digit, NACA 5-digit, Eppler series, Selig series, and other airfoils with higher aerodynamic performance at Reynolds numbers (Re) of 100,000 to 600,000 (the operation range for small wind turbines, SWTs), were chosen and analyzed in XFOIL software to determine their lift-to-drag ratio (C_L/C_D). The results showed that the SG6043 airfoil had the highest maximum C_L/C_D when compared to the other airfoils. To investigate and enhance the shape modification of the airfoil utilizing variations in thickness-to-camber ratio (t/c) and to determine the ideal t/c at Re of 100,000 to 600,000, the SG6043 airfoil was used. Based on the findings, 0.5 to 1.5 was the optimum t/c at Re of 100,000 to 600,000 for the development of the SG6043 airfoil, which had the maximum C_L/C_D. Then, three airfoils with varying thicknesses and cambers were designed and analyzed at the mentioned Re, with the optimal t/c being between 0.5 and 1.5. The findings indicated that when the Re increased, the SG6043 modified airfoil’s aerodynamic efficiency enhanced. SG6043 modified 1 airfoil presented the greatest C_L/C_D of 184.85 at a Re of 600,000. For the SG6043 modified 2 airfoil, the maximum stall angle (AoA_stall) of 13° was demonstrated for Re of 300,000 to 600,000. Maximum C_L/C_D values for SG6043 modified 1, SG6043 modified 3, and SG6043 modified 2 were 184.85, 182.36, and 177.25, respectively. SG6043 modified 2, SG6043 modified 1, and SG6043 modified 3 had peak lift coefficients (C_L) of 1.798, 1.79, and 1.788, respectively. SG6043 modified airfoils performed well in the drag bucket when initial lift increases were accompanied by either steady or decreasing drag.

Two-phase heat conductors for passive thermal regulation systems of electric vehicles

2025-04-09T00:55:10+00:00

Due to the growing demands for a better environment, great efforts are currently being made in the world to create and improve electric and hybrid vehicles. Heat-loaded equipment of electric transport requires efficient cooling systems. A loop thermosyphon made of aluminum, having two flat multi-channel evaporators and one condenser for cooling electronic components, is developed and tested with acetone as the working fluid. The procedure and results of an experimental study of the characteristics of a thermosyphon are described. The evaporators are supplied with a heat load of varying power; the absorbed heat is dissipated by the condenser. The working fluid is acetone. The influence of thermal load and volume of working fluid on the thermal resistance of a thermosyphon and its components was determined and investigated. The lowest evaporator thermal resistance is 0.15 K/W for the heat load range 30–60 W. The thermosyphon operates stably in a wide range of thermal loads and quickly responds to their changes.

Semi-analytical solution for nonlinear Von Kármán swirling fluid flow via the hybrid analytical and numerical method

2025-04-14T01:15:12+00:00

This study investigates the nonlinear and classical problem of Von Kármán’s viscous swirling fluid flow caused by a single rotating disk. Despite over a century since this problem was first introduced, recent advancements enable more accurate calculations and practical results than previously possible. The core innovation of this paper lies in the application of the Hybrid Analytical and Numerical method (HAN method), which facilitates the derivation of a semi-analytical solution to complex nonlinear differential equations. The HAN method combines numerical and analytical approaches to solve nonlinear problems. Initially, the system of nonlinear differential equations is solved using an arbitrary numerical method. The numerical solution then aids in extracting the analytical solution, which can take forms such as polynomial solutions with constant and unknown coefficients. Since boundary conditions lack the capacity to generate a sufficient number of algebraic equations, the numerical solution provides the additional required equations. The flexibility of the HAN method stems from its ability to leverage various numerical methods, making it a robust approach for solving nonlinear differential equations. Using this methodology, the Von Kármán problem is analytically calculated with remarkable accuracy. Furthermore, this study provides highly precise calculations of several physical and practical outputs, including the thickness of the layer, the slope of flow lines at the wall in the peripheral direction, the peripheral component of wall shear stress, the moment on one side of the wetted disk, the dimensionless moment coefficient for both sides of the disk, Reynolds number as a function of the disk’s finite radius, volume flux, and mechanical power. This research contributes to two main perspectives: first, the mathematical aspect, which demonstrates the ability of the HAN method to solve various nonlinear problems; second, the practical-physical perspective, showcasing the enhanced accuracy and reliability of the obtained results in analyzing fluid flow mechanics.