Ali Al-Abadi | Friedrich-Alexander-Universität Erlangen-Nürnberg (original) (raw)
Papers by Ali Al-Abadi
Flight Physics - Models, Techniques and Technologies, 2018
This chapter describes the method of airfoil optimization considering boundary layer for aerodyna... more This chapter describes the method of airfoil optimization considering boundary layer for aerodynamic efficiency increment. The advantages of laminar boundary layer expansion in airfoil of horizontal axis wind turbine (HAWT) blades are presented as well. The genetic algorithm (GA) optimization interfaced with the flow solver XFOIL was used with multiobjective function. The power performance of turbine with optimized airfoil was calculated by using blade element method (BEM) in software QBlade. The CFD simulation from OpenFOAM ® with Spalart-Allmaras turbulence model showed the visualized airflow. The optimized airfoil shows enlarged laminar boundary layer region in all flow regime with a higher aerodynamic efficiency and the increased gliding ratio (GR). The power velocity and annual energy production (AEP) curves show the performance improvement of wind turbine with the optimized airfoil. The boundary layer thickness and skin-friction coefficient values support the decreased drag of the optimized airfoil. The smaller laminar separation bubbles and reduced stall regime of CFD simulations illustrate the desirable aerodynamics of the resulted airfoil.
2019 6th International Advanced Research Workshop on Transformers (ARWtr), 2019
A thorough investigation of the design parameters influencing the load noise generated by power t... more A thorough investigation of the design parameters influencing the load noise generated by power transformers is performed. The investigation is done through evaluating the calculated noise by using an advanced vibro-acoustic model and benchmarking it against measured sound levels of transformers with different ratings and designs. The design parameters are weighted based on their level of influence on the generated noise and are used to drive a detailed load noise formula (d-LNF). The d-LNF is further developed by weighting the most relevant parameters to drive a simplified LNF. Both formulas have proven their reliability in calculating the load noise and therefore, they have been used in the daily designs to optimize for low noise transformers. However, the advantage of the LNF is that it can be easily exchanged between transformer manufacturers and utilities as it involves the main electrical design data without details about the designs of winding, shields, tank and insulations.
In this work, an optimized HAWT has been analyzed numerically for validating its experimental dat... more In this work, an optimized HAWT has been analyzed numerically for validating its experimental data. The 3-D steady state CFD simulations have been performed in Star CCM+ with the RANS k-ω SST turbulence model. A single blade is modelled in a 120± fraction of a cylindrical domain, using periodic boundaries. Rotational effects are modelled by a frozen rotor approach. The design and off-design performance are investigated. The power coefficient was in good agreement with experimental data. Of special interest are the limitations of steady CFD investigations for the case of partially stalled conditions. It is shown that RANS investigations can provide good power indication despite boundary layer separation and reversal flow. Additional information that can be obtained from simulation such as radial flow, detached boundary layer and flow circulation are presented as well.
In this study, numerical investigations of the performance, wake and control-strategies of an opt... more In this study, numerical investigations of the performance, wake and control-strategies of an optimized wind turbine were performed. These investigations delivers an intensive insight of the wind turbine operation under different control strategies. Further, wake analysis has been validated with existing experimental data. The wind turbine was analyzed by the 3-D steady state CFD simulations of Star CCM+ and by using of two CFD configurations. These are wake and pitch models. The first is used for the wake analysis at the design velocity, whereas the second, which is constructed of the overset technique, is applied for the pitch-control strategy. The overset mesh technique was adapted in the pitch model to overcome the computational domain with overlapping grids. The main advantage of the overset is to facilitate the computational time and effort in investigating the pitch control-strategy, since the pitch angle is prone to variation within a range of operating speed. Thus, it is po...
2019 6th International Advanced Research Workshop on Transformers (ARWtr)
In the current study, intensive measurements and finite element method (FEM) simulations to optim... more In the current study, intensive measurements and finite element method (FEM) simulations to optimize the application of magnetic shunts in power transformers are performed. The investigation accounts the effective parameters influencing the magnetic shunts design for the objective of controlling the leakage flux to reduce the generated losses and noise in transformers. Eventually, design rules for the tank and yoke shunts are developed. The developed design tools are applied on case study transformers with different designs, ratings and short circuit impedances. Results show significant reductions in the generated losses and noise during load operation. The study gives the opportunity to optimize the final power transformer design with saving in materials, and therefore the total cost, while the design is still fulfilling the market requirements for both losses and noise.
2018 IEEE International Conference on High Voltage Engineering and Application (ICHVE), 2018
In the current study, we present an accurate approach for matching the calculated thermal perform... more In the current study, we present an accurate approach for matching the calculated thermal performance of power transformers with measurements. It is done by adapting some well-known and used assumptions for building a theoretical thermal model based on special measurements for the objective of minimum deviation (pm3mathrmK)(\pm 3\mathrm {K})(pm3mathrmK). This can guarantee to meet specified temperature rises while providing an optimized high economical cooling system. The theoretical model calculated oil temperature distribution in medium power transformers. The model handles different winding designs and arrangements and solves for multilayer top-oil temperatures in a matrix form. It also calculates the temperature distribution in radiators, which can easily be validated during temperature rise test. First, the winding temperature is calculated, then the measured data from cooling-curves of a set of different transformer designs is inserted in the model. This implies correcting the calculated gradient and recalculating the top-oil temperatures. The model however is under development and in validation with a set of new manufactured transformers in parallel.
2022 7th International Advanced Research Workshop on Transformers (ARWtr)
IEEE Conference Proceedings, 2019
The focus of European and international markets and standards in the last few years is to achieve... more The focus of European and international markets and standards in the last few years is to achieve highly efficient power transformer designs, depending on the application sector (generation, transmission or distribution). The efficiency is directly related to total losses and in turn the heat emission. Losses in the power transformer are the summation of load and no-load losses. The load losses, which generally dominate the total losses, consist of ohmic and stray losses. However, reduction of ohmic losses is limited by the conductivity and design of the winding conductors. The stray losses are generated inside and outside the windings. Losses outside the windings (leads, tank and clamping structure) can be reduced through control of the leakage flux and the trade-off between different electromagnetic materials, such as magnetic shunts. In the current study, we present intensive investigations and optimizations of the application of magnetic shunts to control the leakage flux in pow...
In oil immersed power transformers, tank resonance can add a significant contribution to the gene... more In oil immersed power transformers, tank resonance can add a significant contribution to the generated noise. In the current study, we present a systematic procedure to first detect the resonance in the tank and then controlling its effect on noise. This is done by either shifting resonance frequencies or damping the resulting vibrations via optimizing additional outer stiffeners. The procedure consists of measurement, simulation and modelling. The study shows the ability to predict the natural frequencies of the tank with a high accuracy, which is validated by applying hummer-test in specific places on the tank walls. Noise measurements are conducted before and after applying the outer stiffeners on the transformer walls with and without radiators. Results show that by following the presented procedure for a case study transformer it is possible to reduce the noise by about 5 dB. Introduction The transformer tank is mechanically, acoustically and electromagnetically connected to th...
2019 6th International Advanced Research Workshop on Transformers (ARWtr), 2019
Thermal performance of oil-immersed power transformer requires comprehensive solutions for the co... more Thermal performance of oil-immersed power transformer requires comprehensive solutions for the complex conjugate thermal-hydraulic problem which determines the thermal behavior of the oil and winding set. However, development of a thermal model without consideration of test procedures and limitations can led to inaccurate results during factory acceptance test (FAT). In the current study, we present improvements in modelling and testing based on an effective data exchange between both. Accurate loss calculation in transformer components and better investigation of oil behavior as well as development of more reliable rules to analyze heat-run results with consideration of new effective factors lead to a more accurate calculation of the thermal characteristics. This will increase the level of certainty in meeting the specified temperature rises during FAT, and therefore, accurate prediction of the transformer lifetime. Furthermore, minimum deviation between calculated and measured temperatures will allow optimization of the cooling system resulting in a more economical transformer design.
A numerical method was used for calculation the pressure distribution and then finding aerodynam ... more A numerical method was used for calculation the pressure distribution and then finding aerodynam ic forces to give an estimation for the high- lift systems effect on two-dimensional airfoil for an inviscid incompressible flow (panel method), the computational method investigated experimentally. The study focused on flap and slat effects on the aerodynamic forces at the wings as two of the important items of the high lift systems. Experimental study was made with suction type low-speed wind tunnel for an airfoil of (NACA 0015) supported with leading edge slat and trailing edge flap. The effective forces of lift and drag were measured by two components balance. Different angles of attack (-4, 0, 4, 8 & 12) o and different flap angles (0, 10, 20 & 30) o were chosen with and without slat, variable air velocities (8, 12, 16 & 20)m/s were applied. The computational results compared with experimentally measured data.
Journal of Physics: Conference Series
Experimental investigations have been conducted by exposing an efficient wind turbine model to di... more Experimental investigations have been conducted by exposing an efficient wind turbine model to different turbulence levels in a wind tunnel. Nearly isotropic turbulence is generated by using two static squared grids: fine and coarse one. In addition, the distance between the wind-turbine and the grid is adjusted. Hence, as the turbulence decays in the flow direction, the wind-turbine is exposed to turbulence with various energy and length scale content. The developments of turbulence scales in the flow direction at various Reynolds numbers and the grid mesh size are measured. Those measurements are conducted with hot-wire anemometry in the absence of the wind-turbine. Detailed measurements and analysis of the upstream and downstream velocities, turbulence intensity and spectrum distributions are done. Performance measurements are conducted with and without turbulence grids and the results are compared. Performance measurements are conducted with an experimental setup that allow measuring of torque, rotational speed from the electrical parameters. The study shows the higher the turbulence level, the higher the power coefficient. This is due to many reasons. First, is the interaction of turbulence scales with the blade surface boundary layer, which in turn delay the stall. Thus, suppressing the boundary layer and preventing it from separation and hence enhancing the aerodynamics characteristics of the blade. In addition, higher turbulence helps in damping the tip vortices. Thus, reduces the tip losses. Adding winglets to the blade tip will reduce the tip vortex. Further investigations of the near and far wake-surrounding intersection are performed to understand the energy exchange and the free stream entrainment that help in retrieving the velocity.
In this paper, the error estimate of -Galerkin expanded mixed finite element methods (EMFEMs) is ... more In this paper, the error estimate of -Galerkin expanded mixed finite element methods (EMFEMs) is studied by investigating the semi discrete and fully discrete for parabolic integro-differential equations (PIDEs) with a nonlinear memory. We carried out theoretical survey for studying the existence and uniqueness of the numerical schemes.
Flight Physics - Models, Techniques and Technologies, 2018
This chapter describes the method of airfoil optimization considering boundary layer for aerodyna... more This chapter describes the method of airfoil optimization considering boundary layer for aerodynamic efficiency increment. The advantages of laminar boundary layer expansion in airfoil of horizontal axis wind turbine (HAWT) blades are presented as well. The genetic algorithm (GA) optimization interfaced with the flow solver XFOIL was used with multiobjective function. The power performance of turbine with optimized airfoil was calculated by using blade element method (BEM) in software QBlade. The CFD simulation from OpenFOAM ® with Spalart-Allmaras turbulence model showed the visualized airflow. The optimized airfoil shows enlarged laminar boundary layer region in all flow regime with a higher aerodynamic efficiency and the increased gliding ratio (GR). The power velocity and annual energy production (AEP) curves show the performance improvement of wind turbine with the optimized airfoil. The boundary layer thickness and skin-friction coefficient values support the decreased drag of the optimized airfoil. The smaller laminar separation bubbles and reduced stall regime of CFD simulations illustrate the desirable aerodynamics of the resulted airfoil.
2019 6th International Advanced Research Workshop on Transformers (ARWtr), 2019
A thorough investigation of the design parameters influencing the load noise generated by power t... more A thorough investigation of the design parameters influencing the load noise generated by power transformers is performed. The investigation is done through evaluating the calculated noise by using an advanced vibro-acoustic model and benchmarking it against measured sound levels of transformers with different ratings and designs. The design parameters are weighted based on their level of influence on the generated noise and are used to drive a detailed load noise formula (d-LNF). The d-LNF is further developed by weighting the most relevant parameters to drive a simplified LNF. Both formulas have proven their reliability in calculating the load noise and therefore, they have been used in the daily designs to optimize for low noise transformers. However, the advantage of the LNF is that it can be easily exchanged between transformer manufacturers and utilities as it involves the main electrical design data without details about the designs of winding, shields, tank and insulations.
In this work, an optimized HAWT has been analyzed numerically for validating its experimental dat... more In this work, an optimized HAWT has been analyzed numerically for validating its experimental data. The 3-D steady state CFD simulations have been performed in Star CCM+ with the RANS k-ω SST turbulence model. A single blade is modelled in a 120± fraction of a cylindrical domain, using periodic boundaries. Rotational effects are modelled by a frozen rotor approach. The design and off-design performance are investigated. The power coefficient was in good agreement with experimental data. Of special interest are the limitations of steady CFD investigations for the case of partially stalled conditions. It is shown that RANS investigations can provide good power indication despite boundary layer separation and reversal flow. Additional information that can be obtained from simulation such as radial flow, detached boundary layer and flow circulation are presented as well.
In this study, numerical investigations of the performance, wake and control-strategies of an opt... more In this study, numerical investigations of the performance, wake and control-strategies of an optimized wind turbine were performed. These investigations delivers an intensive insight of the wind turbine operation under different control strategies. Further, wake analysis has been validated with existing experimental data. The wind turbine was analyzed by the 3-D steady state CFD simulations of Star CCM+ and by using of two CFD configurations. These are wake and pitch models. The first is used for the wake analysis at the design velocity, whereas the second, which is constructed of the overset technique, is applied for the pitch-control strategy. The overset mesh technique was adapted in the pitch model to overcome the computational domain with overlapping grids. The main advantage of the overset is to facilitate the computational time and effort in investigating the pitch control-strategy, since the pitch angle is prone to variation within a range of operating speed. Thus, it is po...
2019 6th International Advanced Research Workshop on Transformers (ARWtr)
In the current study, intensive measurements and finite element method (FEM) simulations to optim... more In the current study, intensive measurements and finite element method (FEM) simulations to optimize the application of magnetic shunts in power transformers are performed. The investigation accounts the effective parameters influencing the magnetic shunts design for the objective of controlling the leakage flux to reduce the generated losses and noise in transformers. Eventually, design rules for the tank and yoke shunts are developed. The developed design tools are applied on case study transformers with different designs, ratings and short circuit impedances. Results show significant reductions in the generated losses and noise during load operation. The study gives the opportunity to optimize the final power transformer design with saving in materials, and therefore the total cost, while the design is still fulfilling the market requirements for both losses and noise.
2018 IEEE International Conference on High Voltage Engineering and Application (ICHVE), 2018
In the current study, we present an accurate approach for matching the calculated thermal perform... more In the current study, we present an accurate approach for matching the calculated thermal performance of power transformers with measurements. It is done by adapting some well-known and used assumptions for building a theoretical thermal model based on special measurements for the objective of minimum deviation (pm3mathrmK)(\pm 3\mathrm {K})(pm3mathrmK). This can guarantee to meet specified temperature rises while providing an optimized high economical cooling system. The theoretical model calculated oil temperature distribution in medium power transformers. The model handles different winding designs and arrangements and solves for multilayer top-oil temperatures in a matrix form. It also calculates the temperature distribution in radiators, which can easily be validated during temperature rise test. First, the winding temperature is calculated, then the measured data from cooling-curves of a set of different transformer designs is inserted in the model. This implies correcting the calculated gradient and recalculating the top-oil temperatures. The model however is under development and in validation with a set of new manufactured transformers in parallel.
2022 7th International Advanced Research Workshop on Transformers (ARWtr)
IEEE Conference Proceedings, 2019
The focus of European and international markets and standards in the last few years is to achieve... more The focus of European and international markets and standards in the last few years is to achieve highly efficient power transformer designs, depending on the application sector (generation, transmission or distribution). The efficiency is directly related to total losses and in turn the heat emission. Losses in the power transformer are the summation of load and no-load losses. The load losses, which generally dominate the total losses, consist of ohmic and stray losses. However, reduction of ohmic losses is limited by the conductivity and design of the winding conductors. The stray losses are generated inside and outside the windings. Losses outside the windings (leads, tank and clamping structure) can be reduced through control of the leakage flux and the trade-off between different electromagnetic materials, such as magnetic shunts. In the current study, we present intensive investigations and optimizations of the application of magnetic shunts to control the leakage flux in pow...
In oil immersed power transformers, tank resonance can add a significant contribution to the gene... more In oil immersed power transformers, tank resonance can add a significant contribution to the generated noise. In the current study, we present a systematic procedure to first detect the resonance in the tank and then controlling its effect on noise. This is done by either shifting resonance frequencies or damping the resulting vibrations via optimizing additional outer stiffeners. The procedure consists of measurement, simulation and modelling. The study shows the ability to predict the natural frequencies of the tank with a high accuracy, which is validated by applying hummer-test in specific places on the tank walls. Noise measurements are conducted before and after applying the outer stiffeners on the transformer walls with and without radiators. Results show that by following the presented procedure for a case study transformer it is possible to reduce the noise by about 5 dB. Introduction The transformer tank is mechanically, acoustically and electromagnetically connected to th...
2019 6th International Advanced Research Workshop on Transformers (ARWtr), 2019
Thermal performance of oil-immersed power transformer requires comprehensive solutions for the co... more Thermal performance of oil-immersed power transformer requires comprehensive solutions for the complex conjugate thermal-hydraulic problem which determines the thermal behavior of the oil and winding set. However, development of a thermal model without consideration of test procedures and limitations can led to inaccurate results during factory acceptance test (FAT). In the current study, we present improvements in modelling and testing based on an effective data exchange between both. Accurate loss calculation in transformer components and better investigation of oil behavior as well as development of more reliable rules to analyze heat-run results with consideration of new effective factors lead to a more accurate calculation of the thermal characteristics. This will increase the level of certainty in meeting the specified temperature rises during FAT, and therefore, accurate prediction of the transformer lifetime. Furthermore, minimum deviation between calculated and measured temperatures will allow optimization of the cooling system resulting in a more economical transformer design.
A numerical method was used for calculation the pressure distribution and then finding aerodynam ... more A numerical method was used for calculation the pressure distribution and then finding aerodynam ic forces to give an estimation for the high- lift systems effect on two-dimensional airfoil for an inviscid incompressible flow (panel method), the computational method investigated experimentally. The study focused on flap and slat effects on the aerodynamic forces at the wings as two of the important items of the high lift systems. Experimental study was made with suction type low-speed wind tunnel for an airfoil of (NACA 0015) supported with leading edge slat and trailing edge flap. The effective forces of lift and drag were measured by two components balance. Different angles of attack (-4, 0, 4, 8 & 12) o and different flap angles (0, 10, 20 & 30) o were chosen with and without slat, variable air velocities (8, 12, 16 & 20)m/s were applied. The computational results compared with experimentally measured data.
Journal of Physics: Conference Series
Experimental investigations have been conducted by exposing an efficient wind turbine model to di... more Experimental investigations have been conducted by exposing an efficient wind turbine model to different turbulence levels in a wind tunnel. Nearly isotropic turbulence is generated by using two static squared grids: fine and coarse one. In addition, the distance between the wind-turbine and the grid is adjusted. Hence, as the turbulence decays in the flow direction, the wind-turbine is exposed to turbulence with various energy and length scale content. The developments of turbulence scales in the flow direction at various Reynolds numbers and the grid mesh size are measured. Those measurements are conducted with hot-wire anemometry in the absence of the wind-turbine. Detailed measurements and analysis of the upstream and downstream velocities, turbulence intensity and spectrum distributions are done. Performance measurements are conducted with and without turbulence grids and the results are compared. Performance measurements are conducted with an experimental setup that allow measuring of torque, rotational speed from the electrical parameters. The study shows the higher the turbulence level, the higher the power coefficient. This is due to many reasons. First, is the interaction of turbulence scales with the blade surface boundary layer, which in turn delay the stall. Thus, suppressing the boundary layer and preventing it from separation and hence enhancing the aerodynamics characteristics of the blade. In addition, higher turbulence helps in damping the tip vortices. Thus, reduces the tip losses. Adding winglets to the blade tip will reduce the tip vortex. Further investigations of the near and far wake-surrounding intersection are performed to understand the energy exchange and the free stream entrainment that help in retrieving the velocity.
In this paper, the error estimate of -Galerkin expanded mixed finite element methods (EMFEMs) is ... more In this paper, the error estimate of -Galerkin expanded mixed finite element methods (EMFEMs) is studied by investigating the semi discrete and fully discrete for parabolic integro-differential equations (PIDEs) with a nonlinear memory. We carried out theoretical survey for studying the existence and uniqueness of the numerical schemes.