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 ...
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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%.
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 ...
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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
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. ...
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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.
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 ...
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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
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 ...
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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.
