Research Paper
Computational Fluid Dynamics (CFD)
Samaneh Hajikhani; Foad Farhani; Hassan Ali Ozgoli; Seyed Mostafa Hosseinalipour
Abstract
Hot gas ingestion, due to pressure differences in the turbine’s main flow path, is a challenge for gas turbine designers. It reduces aerodynamic performance, increases temperature gradients and thermal stresses, and decreases disk life. Designers should predict the ingestion and use the precise ...
Read More
Hot gas ingestion, due to pressure differences in the turbine’s main flow path, is a challenge for gas turbine designers. It reduces aerodynamic performance, increases temperature gradients and thermal stresses, and decreases disk life. Designers should predict the ingestion and use the precise design of the cooling system, balancing the cooling and sealing flow, to enable the turbine to operate at higher temperatures (TIT) and efficiency to save costs and reduce harmful effects on turbine components. This paper presents a numerical investigation of a 1.5-stage test rig to study the ingestion phenomenon. A numerical tool was developed to enhance the coefficients and constants of a rapid ingestion model in a zero-dimensional secondary air system (SAS) code applicable to power plant turbines, such as Frame 9. Comparisons of CFD and test results demonstrate satisfactory agreement. Combining CFD and experimental validation, a numerical effectiveness map for the selected test rig rim seal is presented. CFD results post-processing reveals that increased cooling flow rate increases the pressure within the wheelspace, reduces swirl in the core region, and improves seal effectiveness. The swirl ratio was highly sensitive to SAS flow, increasing by 90% with a 50% reduction in SAS flow at a dimensionless radius of 0.85. Analysis of flow vectors exiting the axial clearance rim seal indicates that increasing the SAS flow rate enhances the main gas path flow disturbances. Moreover, at a constant flow rate, an increase in the first wheelspace flow rate increases the effectiveness of the second wheelspace by approximately 33%.
Review paper
Micro and Nano Systems
Azadeh Shahidian; Sanam Tahouneh
Abstract
In recent years, microfluidic devices have had various applications, such as the biological field. Hence, it is essential to study fluid flow governing equations in order to realization and ability to better control fluids in different flow regimes according to microfluidic devices. Also, study of inducing ...
Read More
In recent years, microfluidic devices have had various applications, such as the biological field. Hence, it is essential to study fluid flow governing equations in order to realization and ability to better control fluids in different flow regimes according to microfluidic devices. Also, study of inducing source, fabrication technique, and numerical procedure of fluid flow simulation are necessary for flow solution and are used to select proper devices.Here, the mentioned cases have been studied. As well, numerical methods of fluid flow study for various type of fluid, their comparison and pros and cons of each of them have been briefly expressed that may be used for the development of them. Then, the extensive biological application of micromixers and micropumps have been investigated. It is expected that this paper will be of attention to scholars or practitioners in the micromixer and micropump biomedical technology field and those who enter this context for the first time and may also highlight what will assist in future development.
Research Paper
Stress Analysis
Hasan Eleashy
Abstract
This paper introduces a new study to improve performance of the v6-engine crankshaft as V-type engine crankshaft has little consideration in literature. First, static analysis for v6-crankshaft is presented including geometric parameters, loading analysis and material selection. Secondly, finite element ...
Read More
This paper introduces a new study to improve performance of the v6-engine crankshaft as V-type engine crankshaft has little consideration in literature. First, static analysis for v6-crankshaft is presented including geometric parameters, loading analysis and material selection. Secondly, finite element method is applied to analyze a model for v6-crankshaft with a fine element mesh. The boundary condition is formulated to simulate the proposed model. Then, solution for maximum equivalent stress, total deformation and safety factor is carried out. The solution indicates that fillet areas are the most critical sections with highest stress concentrations. Finally, parametric optimization technique is performed to detect the optimum values for fillet radii that produce minimum equivalent stress and minimum total deformation. The optimized model is compared with the original model and theoretical calculations. In the optimized model, maximum equivalent stress is reduced by 34.45% with an increase in mass by 0.02%. Geometric optimizing of v6-crankshaft design provides an effective methodology to improve its performance.
Research Paper
Composite Materials
Hossein Lexian; Javad Gholampour Darzi; Mohammad Hossein Alaei; Seyed Ali Khalife Soltani
Abstract
This research investigates the effect of feed rate, cutting speed, and orientation of fabric layers on milling forces in high-speed milling of bidirectional C/C composite using the Al2O3 grinding tool in order to decrease the machining time and increase the tool life based on the response surface method ...
Read More
This research investigates the effect of feed rate, cutting speed, and orientation of fabric layers on milling forces in high-speed milling of bidirectional C/C composite using the Al2O3 grinding tool in order to decrease the machining time and increase the tool life based on the response surface method (RSM). For this reason, the above-mentioned parameters were assumed as the input parameters which their effects were investigated on the machining forces (using a milling dynamometer) and tool wear using the central composite design of RSM. Two quadratic models were developed to predict normal and tangential forces in high-speed milling of bidirectional C/C composite. The developed models were then evaluated using three experiments. The results also showed that the orientation of the composite layers has the greatest effect on the milling forces and tool wear after which the tool cutting speed and feed rate respectively. The lowest milling forces were observed at the orientation of (0°,90°), a feed rate of 0.5 m/min, and the cutting speed of 4521.6 m/min.
Research Paper
Manufacturing Processes
Haneen Lateef; Saad Mahmood Ali
Abstract
The objective of this study is to examine how the input parameters of wet-EDM, near-dry (ND-EDM), and NDPM-EDM affect the output performances of the newly fabricated metal matrix composites (MMCs) of aluminum Al-7075/MSGNP nanocomposites produced by the stir-casting. Air, Ar, mix (Ar+N2), and Ferron ...
Read More
The objective of this study is to examine how the input parameters of wet-EDM, near-dry (ND-EDM), and NDPM-EDM affect the output performances of the newly fabricated metal matrix composites (MMCs) of aluminum Al-7075/MSGNP nanocomposites produced by the stir-casting. Air, Ar, mix (Ar+N2), and Ferron gases were included in the current study, which used vegetable oil as a dielectric medium. Additionally, Kaolinite Nano powders were employed as an additive in ND-EDM studies. The data obtained indicate that the greatest MRR attained in the ND-EDM process was 29.425 mm3/min when vegetable oil and Freon gas were used. In the NDPM-EDM, the highest achieved MRR obtained using the Freon gas reached 15.468 (used 800 µsec, 5% Al2SiO2(OH)4). The obtained result is higher than the highest value obtained when using vegetable oil alone by 209.37%. The lowest achieved EWR obtained using the Freon gas reached 0.003 with the vegetable oil + 5% and 10% Al2SiO2(OH)4). The lowest achieved SR for all the implemented experiments, was obtained with used the Freon additive gas to dielectric, reached 4.797 µm (used 5% Al2SiO2(OH)4). The SR value obtained is 19.88% lower than the minimum value achieved when using only vegetable oil. The SEM study showed that the average thickness of the recast white layer was significantly reduced when using the ND-EDM approaches compared to the standard wet-EDM method. The decrease percentages for introducing air, Ar, mix (Ar-N2), and Freon gases into the vegetable oil dielectrics for ND-EDM were 108.17%, 165.51%, 630.26%, and (∞).
Research Paper
Fuel Cells
Mahdi Keyhanpour; Majid Ghassemi
Abstract
Researchers encounter difficulties in producing clean energy and addressing environmental issues. Solid oxide fuel cells (SOFCs) present a promising prospect to the growing demand for clean and efficient electricity due to their capacity to convert chemically stored energy into electrical energy directly. ...
Read More
Researchers encounter difficulties in producing clean energy and addressing environmental issues. Solid oxide fuel cells (SOFCs) present a promising prospect to the growing demand for clean and efficient electricity due to their capacity to convert chemically stored energy into electrical energy directly. In enhancing this technology, ammonia is employed as a cost-effective and carbon-free fuel with convenient transport capabilities. Efficiently predicting the performance of a system in relation to its operating environment has the potential to expedite the identification of the optimal operating conditions across a broad spectrum of parameters. For this purpose, the performance of intermediate temperature solid oxide fuel cell (IT-SOFC) with inlet ammonia fuel is predicted utilizing machine learning, which is efficient in time and cost. Initially, the system is simulated with computational fluid dynamics finite element code to generate data for training machine learning algorithms (DNN, RFM and LASSO regression), followed by an evaluation of the predictive accuracy of these algorithms. The analysis demonstrates that the three examined algorithms exhibit sufficient accuracy in predicting the performance of the introduced solid oxide fuel cell (SOFC) system, all surpassing a 95 percent threshold. The RFM and DNN exhibit the most accurate predictions for the maximum temperature and power density of fuel cells, respectively.
Research Paper
Robotics
Vengatesan Arumugam; Vasudevan Alagumalai
Abstract
Mobile robots have garnered significant attention across various domains, including industrial automation, healthcare, logistics, and autonomous vehicles. However, effective navigation in dynamic and complex environments remains a critical challenge. This research introduces an improved deep q-network ...
Read More
Mobile robots have garnered significant attention across various domains, including industrial automation, healthcare, logistics, and autonomous vehicles. However, effective navigation in dynamic and complex environments remains a critical challenge. This research introduces an improved deep q-network algorithm for learning-based mobile robot navigation, addressing a multi-objective optimization problem that seeks to minimize path distance, energy consumption, and travel time within a grid-mapped complex environment. The deep q-network algorithm was enhanced to improve its efficiency in determining the optimal path to a target point. Experimental validation using a learning robot demonstrated the effectiveness of the proposed approach, ensuring safe path generation with collision avoidance, optimized path distance, and practical implementability in mobile robot applications. Furthermore, training, simulation, and analysis results revealed less than 2% deviations between simulation and experimental outcomes, with a path distance error of only 1.3765%. Finally, the proposed algorithm was benchmarked against existing approaches, including the A* algorithm, enhanced deep q-network, and dueling double deep q-network, showcasing its superior performance.
Research Paper
Smart Material
Majid Jabbari
Abstract
Electrical energy can be harvested from the vibrations of piezoelectric plates. The behavior of the piezoelectric plate is simulated using electromechanical coupling. Given the large strain experienced by the flexible plate, the linear theory is inadequate; therefore, the effect of Von Karman strain ...
Read More
Electrical energy can be harvested from the vibrations of piezoelectric plates. The behavior of the piezoelectric plate is simulated using electromechanical coupling. Given the large strain experienced by the flexible plate, the linear theory is inadequate; therefore, the effect of Von Karman strain must be considered. This paper investigates and validates the vibrational behavior of a piezoelectric nonlinear plate. Specifically, it employs coupled equations for a multilayered plate, incorporates Von Karman’s nonlinear strain, and applies Mindlin’s first-order shear deformation theory. The electrical response is obtained through finite element analysis of the piezoelectric nonlinear plate in Matlab. Different boundary conditions are considered to verify the results, including clamped edges, simply supported edges, and a combination of two simply supported and two clamped edges. The electrical response of the open-circuit case under harmonic excitation is presented. Furthermore, the phenomenon of voltage cancellation during plate vibrations is studied, and a method for enhancing energy harvesting performance using separated electrodes is proposed. The results indicate that, across all cases, the voltage response with a continuous electrode is lower than with segmented electrodes at the first natural frequency.
Research Paper
Solar Energy
Fatemeh karami; Majid Sabzpooshani
Abstract
This paper presents a comparative analytical investigation of five distinct configurations of single-pass flat plate solar air heaters (SAHs), incorporating fins, baffles, porous matrix, and internal air recycling. A steady-state, one-dimensional mathematical model was developed and solved analytically ...
Read More
This paper presents a comparative analytical investigation of five distinct configurations of single-pass flat plate solar air heaters (SAHs), incorporating fins, baffles, porous matrix, and internal air recycling. A steady-state, one-dimensional mathematical model was developed and solved analytically to evaluate both thermal and thermo-hydraulic performance under various mass flow rates and reflux ratios. The results indicate that using a porous matrix alone results in approximately 14% lower thermal efficiency compared to configurations with fins and baffles. Placing the matrix beneath the absorber plate improved thermal efficiency by about 1.5%, but reduced thermo-hydraulic efficiency by roughly 2.5% compared to placing it above. While combining enhancement techniques does not always yield superior performance, the SAH equipped with fins and baffles alone achieved the highest thermal and thermo-hydraulic efficiencies across most conditions. Furthermore, increasing solar radiation intensity and air mass flow rate enhanced useful heat gain, although higher pressure losses caused the thermo-hydraulic efficiency to decline at elevated flow rates. Overall, this study provides valuable insights into the optimal integration of thermal enhancement methods in solar air heaters for improved energy performance.
Research Paper
Vibration
Seyyed Hamed Tabatabaei; Nima Bayandori
Abstract
Today, one of the criteria for choosing a vehicle is the comfort inside the cabin, which is influenced by various factors, including the noise inside the vehicle. For this purpose, this research investigates this issue experimentally by choosing a vehicle as a test study and using a portable sound pressure ...
Read More
Today, one of the criteria for choosing a vehicle is the comfort inside the cabin, which is influenced by various factors, including the noise inside the vehicle. For this purpose, this research investigates this issue experimentally by choosing a vehicle as a test study and using a portable sound pressure level measuring device. In the first stage, the standard insulators installed on the vehicle are evaluated. In the second stage, the standard insulators are separated from the vehicle and examined without insulation. In the last stage, the vehicle's insulation material is changed, insulation is re-evaluated by installing the new sound insulation, and the desired insulation performance is tested. For all the mentioned stages, two general tests are considered. First, the vehicle is tested under static tests at different engine speeds, including idling speed, 2000 and 3000 rpm, and then the vehicle is tested under dynamic tests at speeds of 30, 50, 70, and 100 km/h. The static test shows the performance of insulation in reducing engine noise, and the dynamic test shows the performance of insulation in reducing road and wind noise. The results indicate that vehicle insulation with Nano polyester significantly affects sound penetration into the interior of the vehicle, which on average is between 5.3% to 8.03% dB in the complete insulation of the vehicle decreases. These findings highlight the effectiveness of nano polyester insulation in improving acoustic comfort inside the vehicle cabin.
', './data/jcarme/coversheet/cover_en.jpg'))
