The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Andrew D. Sommers - One of the best experts on this subject based on the ideXlab platform.
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A thermal model of friction stir welding in aluminum alloys
International Journal of Machine Tools and Manufacture, 2008Co-Authors: Carter Hamilton, Stanisław Dymek, Andrew D. SommersAbstract:A thermal model of friction stir welding was developed that utilizes a new Slip Factor based on the energy per unit length of weld. The Slip Factor is derived from an empirical, linear relationship observed between the ratio of the maximum welding temperature to the solidus temperature and the welding energy. The thermal model successfully predicts the maximum welding temperature over a wide range of energy levels but under predicts the temperature for low energy levels for which heat from plastic deformation dominates. The thermal model supports the hypothesis that the relationship between the temperature ratio and energy level is characteristic of aluminum alloys that share similar thermal diffusivities. The thermal model can be used to generate characteristic temperature curves from which the maximum welding temperature in an alloy may be estimated if the thermal diffusivity, welding parameters and tool geometry are known.
Carter Hamilton - One of the best experts on this subject based on the ideXlab platform.
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A thermal model of friction stir welding in aluminum alloys
International Journal of Machine Tools and Manufacture, 2008Co-Authors: Carter Hamilton, Stanisław Dymek, Andrew D. SommersAbstract:A thermal model of friction stir welding was developed that utilizes a new Slip Factor based on the energy per unit length of weld. The Slip Factor is derived from an empirical, linear relationship observed between the ratio of the maximum welding temperature to the solidus temperature and the welding energy. The thermal model successfully predicts the maximum welding temperature over a wide range of energy levels but under predicts the temperature for low energy levels for which heat from plastic deformation dominates. The thermal model supports the hypothesis that the relationship between the temperature ratio and energy level is characteristic of aluminum alloys that share similar thermal diffusivities. The thermal model can be used to generate characteristic temperature curves from which the maximum welding temperature in an alloy may be estimated if the thermal diffusivity, welding parameters and tool geometry are known.
Tommaso Capurso - One of the best experts on this subject based on the ideXlab platform.
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Slip Factor Correction in 1-D Performance Prediction Model for PaTs
Water, 2019Co-Authors: Tommaso Capurso, Michele Stefanizzi, Giuseppe Pascazio, S. Ranaldo, Sergio Mario Camporeale, Bernardo Fortunato, Marco TorresiAbstract:In recent years, pumps operated as turbines (PaTs) have been gaining the interest of industry and academia. For instance, PaTs can be effectively used in micro hydropower plants (MHP) and water distribution systems (WDS). Therefore, further efforts are necessary to investigate their fluid dynamic behavior. Compared to conventional turbines, a lower number of blades is employed in PaTs, lowering their capability to correctly guide the flow, hence reducing the Euler’s work; thus, the Slip phenomenon cannot be neglected at the outlet section of the runner. In the first part of the paper, the Slip phenomenon is numerically investigated on a simplified geometry, evidencing the dependency of the lack in guiding the flow on the number of blades. Then, a commercial double suction centrifugal pump, characterized by the same specific speed, is considered, evaluating the dependency of the Slip on the flow rate. In the last part, a Slip Factor correlation is introduced based on those CFD simulations. It is shown how the inclusion of this parameter in a 1-D performance prediction model allows us to reduce the performance prediction errors with respect to experiments on a pump with a similar specific speed by 5.5% at design point, compared to no Slip model, and by 8% at part-loads, rather than using Busemann and Stodola formulas.
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How to Improve the Performance Prediction of a Pump as Turbine by Considering the Slip Phenomenon
Proceedings, 2018Co-Authors: Tommaso Capurso, Michele Stefanizzi, Giuseppe Pascazio, Sergio Mario Camporeale, Bernardo Fortunato, Marco Torresi, Giovanni Caramia, Lorenzo BergaminiAbstract:Nowadays Pumps working as Turbines (PaT) are devices widely used to perform energy recovery in hydraulic grids, thus improving their overall efficiency, and to build small hydropower plants. In this work, a centrifugal pump has been numerically investigated in turbine operating mode by means of the open-source CFD code OpenFOAM with emphasis on the flow field at the runner outlet. Due to the reduced number of blades in a PaT, the mean outlet relative velocity angle differs from the blade angle. In order to account for this phenomenon, the Slip Factor is introduced. The Slip Factor is investigated and its application to a 1D model is shown in order to highlight the improvement in predicting the characteristic curve of a centrifugal pump used in reverse mode as a turbine (PaT) especially at its part-load.
Mark R. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Analysis and Validation of a Unified Slip Factor Model for Impellers at Design and Off-Design Conditions
Journal of Turbomachinery, 2011Co-Authors: Xuwen Qiu, David Japikse, Jinhui Zhao, Mark R. AndersonAbstract:This paper presents a unified Slip model for axial, radial, and mixed-flow impellers. The core assumption of the model is that the flow deviation or the Slip velocity at the impeller exit is mainly originated from the blade loading near the discharge of an impeller and its subsequent relative eddy in the impeller passage. The blade loading is estimated and then used to derive the Slip velocity using Stodola’s assumption. The final form of the Slip Factor model can be successfully related to Carter’s rule for axial impellers and Stodola’s Slip model for radial impellers, making the case for this model applicable to axial, radial, and mixed-flow impellers. Unlike conventional Slip Factor models for radial impellers, the new Slip model suggests that the flow coefficient at the impeller exit is an important variable for the Slip Factor when there is significant blade turning at the impeller discharge. This explains the interesting off-design trends for Slip Factor observed from experiments, such as the rise of the Slip Factor with flow coefficient in the Eckardt A impeller. Extensive validation results for this new model are presented in this paper. Several cases are studied in detail to demonstrate how this new model can capture the Slip Factor variation at the off-design conditions. Furthermore, a large number of test data from more than 90 different compressors, pumps, and blowers were collected. Most cases are radial impellers, but a few axial impellers are also included. The test data and model predictions of the Slip Factor are compared at both design and off-design flow conditions. In total, over 1650 different flow conditions are evaluated. The unified model shows a clear advantage over the traditional Slip Factor correlations, such as the Busemann–Wiesner model, when off-design conditions are considered.
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Analysis and Validation of a Unified Slip Factor Model for Impellers at Design and Off-Design Conditions
Volume 7: Turbomachinery Parts A B and C, 2010Co-Authors: Xuwen Qiu, David Japikse, Jinhui Zhao, Mark R. AndersonAbstract:This paper presents a unified Slip model for axial, radial, and mixed-flow impellers. The core assumption of the model is that the flow deviation or Slip velocity at impeller exit is mainly originated from the blade loading near the discharge of an impeller and its subsequent relative eddy in the impeller passage. The blade loading is estimated and then used to derive the Slip velocity using Stodola’s assumption. The final form of the Slip Factor model can be successfully related to Carter’s rule [1] for axial impellers and Stodola’s [2] Slip model for radial impellers, making the case for this model to be applicable to axial, radial, and mixed-flow impellers. Unlike conventional Slip Factor models for radial impellers, the new Slip model suggests that the flow coefficient at the impeller exit is an important variable for the Slip Factor when there is significant blade turning at the impeller discharge. This explains the interesting off-design trends for Slip Factor observed from experiments, such as the rise of the Slip Factor with flow coefficient in the Eckardt A impeller [3]. Extensive validation results for this new model are presented in this paper. Several cases are studied in detail to demonstrate how this new model can capture the Slip Factor variation at the off-design conditions. Furthermore, a large number of test data from more than 90 different compressors, pumps, and blowers were collected. Most cases are radial impellers, but a few axial impellers are also included. The test data and model predictions of the Slip Factor are compared at both design and off-design flow conditions. In total, over 1,650 different flow conditions are evaluated. The unified model shows a clear advantage over the traditional Slip Factor correlations, such as the Busemann-Wiesner model [4], when off-design conditions are considered.
Marco Torresi - One of the best experts on this subject based on the ideXlab platform.
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Slip Factor Correction in 1-D Performance Prediction Model for PaTs
Water, 2019Co-Authors: Tommaso Capurso, Michele Stefanizzi, Giuseppe Pascazio, S. Ranaldo, Sergio Mario Camporeale, Bernardo Fortunato, Marco TorresiAbstract:In recent years, pumps operated as turbines (PaTs) have been gaining the interest of industry and academia. For instance, PaTs can be effectively used in micro hydropower plants (MHP) and water distribution systems (WDS). Therefore, further efforts are necessary to investigate their fluid dynamic behavior. Compared to conventional turbines, a lower number of blades is employed in PaTs, lowering their capability to correctly guide the flow, hence reducing the Euler’s work; thus, the Slip phenomenon cannot be neglected at the outlet section of the runner. In the first part of the paper, the Slip phenomenon is numerically investigated on a simplified geometry, evidencing the dependency of the lack in guiding the flow on the number of blades. Then, a commercial double suction centrifugal pump, characterized by the same specific speed, is considered, evaluating the dependency of the Slip on the flow rate. In the last part, a Slip Factor correlation is introduced based on those CFD simulations. It is shown how the inclusion of this parameter in a 1-D performance prediction model allows us to reduce the performance prediction errors with respect to experiments on a pump with a similar specific speed by 5.5% at design point, compared to no Slip model, and by 8% at part-loads, rather than using Busemann and Stodola formulas.
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How to Improve the Performance Prediction of a Pump as Turbine by Considering the Slip Phenomenon
Proceedings, 2018Co-Authors: Tommaso Capurso, Michele Stefanizzi, Giuseppe Pascazio, Sergio Mario Camporeale, Bernardo Fortunato, Marco Torresi, Giovanni Caramia, Lorenzo BergaminiAbstract:Nowadays Pumps working as Turbines (PaT) are devices widely used to perform energy recovery in hydraulic grids, thus improving their overall efficiency, and to build small hydropower plants. In this work, a centrifugal pump has been numerically investigated in turbine operating mode by means of the open-source CFD code OpenFOAM with emphasis on the flow field at the runner outlet. Due to the reduced number of blades in a PaT, the mean outlet relative velocity angle differs from the blade angle. In order to account for this phenomenon, the Slip Factor is introduced. The Slip Factor is investigated and its application to a 1D model is shown in order to highlight the improvement in predicting the characteristic curve of a centrifugal pump used in reverse mode as a turbine (PaT) especially at its part-load.
