2023
Davide Lengani Matteo Dellacasagrande, Daniele Simoni
Analysis of Unsteady Loss Sensitivity to Incidence Angle Variation in Low Pressure Turbine Proceedings Article
In: pp. V13BT30A037, ASME, 2023.
@inproceedings{unst-loss-turbine-2023,
title = {Analysis of Unsteady Loss Sensitivity to Incidence Angle Variation in Low Pressure Turbine},
author = {Matteo Dellacasagrande, Davide Lengani, Daniele Simoni, Marina Ubaldi, Angelo Alberto Granata, Matteo Giovannini, Filippo Rubechini, Francesco Bertini},
url = {https://doi.org/10.1115/GT2023-103770
https://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT2023/87097/V13BT30A037/7045565/v13bt30a037-gt2023-103770.pdf},
doi = {10.1115/GT2023-103770},
year = {2023},
date = {2023-09-28},
urldate = {2023-09-28},
volume = {13B},
pages = {V13BT30A037},
publisher = {ASME},
series = {Turbo Expo: Power for Land, Sea, and Air},
abstract = {In the present work, Large Eddy Simulations (LES) of a low pressure turbine cascade have been carried out to understand the different sensitivity to incidence angle variation observed under steady and unsteady inflow conditions. Indeed, experimental evidence shows poor sensitivity to incidence angle variation for the steady case in a range of −9° ≤ i ≤ +9°, while losses grow rapidly in the unsteady flow environment. It will be shown that this is due to wake migration into the core flow region, producing an additional source of losses for the unsteady flow case. Both steady and unsteady simulations have been carried out at nominal and two positive and negative incidence angles.The LES data have been inspected to identify the physical reasons behind the different loss trends, after being validated by means of blade loading and loss coefficient distributions. To this end, Proper Orthogonal Decomposition (POD) has been applied to each dataset. POD modes clearly identify the different structures responsible for loss production in the steady and the unsteady operation of the cascade. The structures carried by upstream wakes have been isolated and identified both in the boundary layer and in the core flow. The process of bowing, tilting and reorientation of the wake filaments and related structures is shown to be the dominant mechanism responsible for the strong loss sensitivity to the incidence angle variation observed under unsteady inflow. Otherwise, structures responsible for the transition of the blade boundary layer do not exhibit significant variation for both the steady and the unsteady flow cases, thus further strengthening that the sensitivity to incidence variation is mainly due to wake migration into the core flow region. This loss source is not classically considered in literature correlations and actual design processes.
},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In the present work, Large Eddy Simulations (LES) of a low pressure turbine cascade have been carried out to understand the different sensitivity to incidence angle variation observed under steady and unsteady inflow conditions. Indeed, experimental evidence shows poor sensitivity to incidence angle variation for the steady case in a range of −9° ≤ i ≤ +9°, while losses grow rapidly in the unsteady flow environment. It will be shown that this is due to wake migration into the core flow region, producing an additional source of losses for the unsteady flow case. Both steady and unsteady simulations have been carried out at nominal and two positive and negative incidence angles.The LES data have been inspected to identify the physical reasons behind the different loss trends, after being validated by means of blade loading and loss coefficient distributions. To this end, Proper Orthogonal Decomposition (POD) has been applied to each dataset. POD modes clearly identify the different structures responsible for loss production in the steady and the unsteady operation of the cascade. The structures carried by upstream wakes have been isolated and identified both in the boundary layer and in the core flow. The process of bowing, tilting and reorientation of the wake filaments and related structures is shown to be the dominant mechanism responsible for the strong loss sensitivity to the incidence angle variation observed under unsteady inflow. Otherwise, structures responsible for the transition of the blade boundary layer do not exhibit significant variation for both the steady and the unsteady flow cases, thus further strengthening that the sensitivity to incidence variation is mainly due to wake migration into the core flow region. This loss source is not classically considered in literature correlations and actual design processes.
Barsi, Dario; Lengani, Davide; Simoni, Daniele; Bertini, Francesco; Giovannini, Matteo; Rubechini, Filippo
Analysis of the sealing flow rate on loss production mechanisms in LPT stage Proceedings Article
In: 15th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, European Turbomachinery Society, 2023, ISSN: 2410-4833.
@inproceedings{Barsi_2023,
title = {Analysis of the sealing flow rate on loss production mechanisms in LPT stage},
author = {Dario Barsi and Davide Lengani and Daniele Simoni and Francesco Bertini and Matteo Giovannini and Filippo Rubechini},
url = {http://dx.doi.org/10.29008/etc2023-170},
doi = {10.29008/etc2023-170},
issn = {2410-4833},
year = {2023},
date = {2023-01-01},
booktitle = {15th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics},
publisher = {European Turbomachinery Society},
series = {ETC15},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
2022
Davide Lengani Dario Barsi, Daniele Simoni
Analysis of the Loss Production Mechanism Due to Cavity–Main Flow Interaction in a Low-Pressure Turbine Stage Journal Article
In: Journal of Turbomachinery, vol. 144, no. 9, pp. 091004, 2022.
@article{nokey,
title = {Analysis of the Loss Production Mechanism Due to Cavity–Main Flow Interaction in a Low-Pressure Turbine Stage},
author = {Dario Barsi, Davide Lengani, Daniele Simoni, Giulio Venturino, Francesco Bertini, Matteo Giovannini, Filippo Rubechini},
url = {https://asmedigitalcollection.asme.org/turbomachinery/article/144/9/091004/1134931/Analysis-of-the-Loss-Production-Mechanism-Due-to},
doi = {10.1115/1.4053745},
year = {2022},
date = {2022-09-01},
journal = {Journal of Turbomachinery},
volume = {144},
number = {9},
pages = {091004},
abstract = {In the present work, URANS simulations are presented to describe the unsteady interaction process between the flow ingested/ejected from a cavity system and the main flow evolving into a low-pressure turbine stage. Particular care is posed on the analysis of the loss generation mechanisms acting outside the stator row and in the rear part of the axial gap separating the cavity flow ejection section and the leading edge plane of the downstream rotor row. The simulated geometry reproduces a typical engine cavity configuration, with upstream and downstream rotor rows reproduced by means of moving bars. Experimental results have been used to validate the simulations. These experimental data cannot explain and quantify alone the overall interaction process between the cavity flows and the main flow. The results of a simulation made by removing the domain of the cavity have been employed in order to better highlight and quantify the effects due to main flow and cavity flows interaction on total pressure loss. A deep inspection of the loss amount along the axial direction makes evident that losses generated in the vane row are basically increased prior to entering into the downstream rotor bars, due to cavity main flow interaction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In the present work, URANS simulations are presented to describe the unsteady interaction process between the flow ingested/ejected from a cavity system and the main flow evolving into a low-pressure turbine stage. Particular care is posed on the analysis of the loss generation mechanisms acting outside the stator row and in the rear part of the axial gap separating the cavity flow ejection section and the leading edge plane of the downstream rotor row. The simulated geometry reproduces a typical engine cavity configuration, with upstream and downstream rotor rows reproduced by means of moving bars. Experimental results have been used to validate the simulations. These experimental data cannot explain and quantify alone the overall interaction process between the cavity flows and the main flow. The results of a simulation made by removing the domain of the cavity have been employed in order to better highlight and quantify the effects due to main flow and cavity flows interaction on total pressure loss. A deep inspection of the loss amount along the axial direction makes evident that losses generated in the vane row are basically increased prior to entering into the downstream rotor bars, due to cavity main flow interaction.
Bellucci J Cozzi L, Giovannini M
Towards the development of an advanced wind turbine rotor design tool integrating full CFD and FEM Journal Article
In: Journal of Physics: Conference Series: Torque 2022, no. Conf. Ser. 2265 042050, 2022.
@article{nokey,
title = {Towards the development of an advanced wind turbine rotor design tool integrating full CFD and FEM},
author = {Cozzi L, Bellucci J, Giovannini M, Papi F, Bianchini A},
doi = {10.1088/1742-6596/2265/4/042050},
year = {2022},
date = {2022-06-01},
journal = {Journal of Physics: Conference Series: Torque 2022},
number = {Conf. Ser. 2265 042050},
abstract = {Large, highly flexible wind turbines of the new generation will make designers face un-precedent challenges, mainly connected to their huge dimensions. To tackle these challenges, it is commonly acknowledged that design tools must evolve in the direction of both improving their accuracy and turning into holistic, multiphysics tools. Furthermore, the wind turbine industry is reaching a high level of maturity, and ever more accurate and reliable design tools are required to further optimise these machines. Within this framework, the study shows the development of an integrated platform for blade design integrating 3D CFD flow simulations and 3D-FEM structural analysis. Artificial intelligence techniques are applied to develop an optimization procedure based on the proposed tool. The potential of the new platform has been tested on the well-known test case of the MEXICO rotor, for which an optimization of the blade design has been carried out. Exploring a design space sampled with 2000 CFD and FEM computations, increases in blade torque have been obtained at each of the three tip-speed ratios (TSR) investigated, ranging from 6% at the nominal TSR to 14% at the lowest one, while stresses on the blade are kept almost unaltered.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Large, highly flexible wind turbines of the new generation will make designers face un-precedent challenges, mainly connected to their huge dimensions. To tackle these challenges, it is commonly acknowledged that design tools must evolve in the direction of both improving their accuracy and turning into holistic, multiphysics tools. Furthermore, the wind turbine industry is reaching a high level of maturity, and ever more accurate and reliable design tools are required to further optimise these machines. Within this framework, the study shows the development of an integrated platform for blade design integrating 3D CFD flow simulations and 3D-FEM structural analysis. Artificial intelligence techniques are applied to develop an optimization procedure based on the proposed tool. The potential of the new platform has been tested on the well-known test case of the MEXICO rotor, for which an optimization of the blade design has been carried out. Exploring a design space sampled with 2000 CFD and FEM computations, increases in blade torque have been obtained at each of the three tip-speed ratios (TSR) investigated, ranging from 6% at the nominal TSR to 14% at the lowest one, while stresses on the blade are kept almost unaltered.
2021
Barsi, Dario; Lengani, Davide; Simoni, Daniele; Venturino, Giulio; Bertini, Francesco; Rubechini, Filippo; Giovannini, Matteo
Analysis of the Loss Production Mechanism due to Cavity-Main Flow Interaction in a LPT Stage Proceedings
ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition June 7–11, 2021 Virtual, Online ASME, vol. GT2021-59932, 2021.
@proceedings{cavity2021,
title = {Analysis of the Loss Production Mechanism due to Cavity-Main Flow Interaction in a LPT Stage},
author = {Dario Barsi and Davide Lengani and Daniele Simoni and Giulio Venturino and Francesco Bertini and Filippo Rubechini and Matteo Giovannini},
url = {https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2021/84935/V02DT39A012/1119835},
doi = {10.1115/GT2021-59932},
year = {2021},
date = {2021-09-16},
urldate = {2021-09-16},
volume = {GT2021-59932},
pages = {V02DT39A012; 12 pages},
publisher = {ASME},
organization = {ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition June 7–11, 2021 Virtual, Online},
abstract = {In the present work URANS simulations are presented to describe the unsteady interaction process between the flow ingested/ejected from a cavity system and the main flow evolving into a Low Pressure Turbine stage. Partic- ular care is posed on the analysis of the loss generation mechanisms acting outside the stator row and in the rear part of the axial gap separating the cavity flow ejection section and the leading edge plane of the downstream ro- tor row. The simulated geometry reproduces a typical en- gine cavity configuration, with upstream and downstream rotor rows reproduced by means of moving bars. Experi- mental results have been used to validate the simulations. This experimental data cannot explain and quantify alone the overall interaction process between the cavity flows and the main flow. The results of a simulation made by remov- ing the domain of the cavity have been employed in order to better highlight and quantify the effects due to main flow and cavity flows interaction on total pressure loss. A deep inspection of the loss amount along the axial direc- tion makes evident that losses generated in the vane row are basically increased prior to enter into the downstream rotor bars, due to cavity main flow interaction},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
In the present work URANS simulations are presented to describe the unsteady interaction process between the flow ingested/ejected from a cavity system and the main flow evolving into a Low Pressure Turbine stage. Partic- ular care is posed on the analysis of the loss generation mechanisms acting outside the stator row and in the rear part of the axial gap separating the cavity flow ejection section and the leading edge plane of the downstream ro- tor row. The simulated geometry reproduces a typical en- gine cavity configuration, with upstream and downstream rotor rows reproduced by means of moving bars. Experi- mental results have been used to validate the simulations. This experimental data cannot explain and quantify alone the overall interaction process between the cavity flows and the main flow. The results of a simulation made by remov- ing the domain of the cavity have been employed in order to better highlight and quantify the effects due to main flow and cavity flows interaction on total pressure loss. A deep inspection of the loss amount along the axial direc- tion makes evident that losses generated in the vane row are basically increased prior to enter into the downstream rotor bars, due to cavity main flow interaction
2019
Rubechini, Filippo; Giovannini, Matteo; Arnone, Andrea; Simoni, Daniele; Bertini, Francesco
ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition June 17–21, 2019 Phoenix, Arizona, USA ASME, vol. Volume 2B: Turbomachinery, no. GT2019-91280, 2019, ISBN: 978-0-7918-5856-1.
@proceedings{Rubechini2019,
title = {Reducing Secondary Flow Losses in Low-Pressure Turbines With Blade Fences: Part I — Design in an Engine-Like Environment},
author = {Filippo Rubechini and Matteo Giovannini and Andrea Arnone and Daniele Simoni and Francesco Bertini},
url = {https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2019/58561/V02BT40A020/1066491},
doi = {10.1115/GT2019-91280},
isbn = {978-0-7918-5856-1},
year = {2019},
date = {2019-11-05},
volume = {Volume 2B: Turbomachinery},
number = {GT2019-91280},
publisher = {ASME},
organization = {ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition June 17–21, 2019 Phoenix, Arizona, USA},
abstract = {This paper deals with the design of passive control devices for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. A novel kind of device is introduced which consists of shelf-like fences to be added to the blade surface. Such a device is intended to hinder the development of secondary flows, thus reducing losses and flow turning deviation with respect to the straight blade.
The first part of this work is devoted to the design of the blade fences, whereas the second part addresses the experimental validation of the device. The blade fences are designed on a LPT stator vane, in an engine-like environment. As secondary flows generated by one blade row produce their major effects on the downstream one, and hence on the stage performance, the assessment is performed on a stator-rotor configuration. Steady calculations are considered for the design, then the optimal geometry is verified via unsteady calculations to include the effects of the actual interaction. The geometry and layout of the blade fences are effectively handled by means of a parametric approach, which enables the fast generation of several configurations. An optimization procedure, based on Artificial Neural Networks (ANNs) is exploited to drive the fences design. The analysis of the relative merit of each solution is carried out using a state-of-the-art CFD approach. Finally, a detailed comparison between the original blade and the one equipped with fences is presented, and the physical mechanisms responsible for the mitigation of secondary flow losses are discussed in detail.},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
This paper deals with the design of passive control devices for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. A novel kind of device is introduced which consists of shelf-like fences to be added to the blade surface. Such a device is intended to hinder the development of secondary flows, thus reducing losses and flow turning deviation with respect to the straight blade.
The first part of this work is devoted to the design of the blade fences, whereas the second part addresses the experimental validation of the device. The blade fences are designed on a LPT stator vane, in an engine-like environment. As secondary flows generated by one blade row produce their major effects on the downstream one, and hence on the stage performance, the assessment is performed on a stator-rotor configuration. Steady calculations are considered for the design, then the optimal geometry is verified via unsteady calculations to include the effects of the actual interaction. The geometry and layout of the blade fences are effectively handled by means of a parametric approach, which enables the fast generation of several configurations. An optimization procedure, based on Artificial Neural Networks (ANNs) is exploited to drive the fences design. The analysis of the relative merit of each solution is carried out using a state-of-the-art CFD approach. Finally, a detailed comparison between the original blade and the one equipped with fences is presented, and the physical mechanisms responsible for the mitigation of secondary flow losses are discussed in detail.
The first part of this work is devoted to the design of the blade fences, whereas the second part addresses the experimental validation of the device. The blade fences are designed on a LPT stator vane, in an engine-like environment. As secondary flows generated by one blade row produce their major effects on the downstream one, and hence on the stage performance, the assessment is performed on a stator-rotor configuration. Steady calculations are considered for the design, then the optimal geometry is verified via unsteady calculations to include the effects of the actual interaction. The geometry and layout of the blade fences are effectively handled by means of a parametric approach, which enables the fast generation of several configurations. An optimization procedure, based on Artificial Neural Networks (ANNs) is exploited to drive the fences design. The analysis of the relative merit of each solution is carried out using a state-of-the-art CFD approach. Finally, a detailed comparison between the original blade and the one equipped with fences is presented, and the physical mechanisms responsible for the mitigation of secondary flow losses are discussed in detail.
Giovannini, Matteo; Rubechini, Filippo; Amato, Giorgio; Arnone, Andrea; Simoni, Daniele; Yepmo, Vianney; Satta, Francesca; Bertini, Francesco
ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition June 17–21, 2019 Phoenix, Arizona, USA ASME, vol. Volume 2B: Turbomachinery, no. GT2019-91284, 2019, ISBN: 978-0-7918-5856-1.
@proceedings{Giovannini2019,
title = {Reducing Secondary Flow Losses in Low-Pressure Turbines With Blade Fences: Part II — Experimental Validation on Linear Cascades},
author = {Matteo Giovannini and Filippo Rubechini and Giorgio Amato and Andrea Arnone and Daniele Simoni and Vianney Yepmo and Francesca Satta and Francesco Bertini},
url = {https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2019/58561/V02BT40A021/1066499},
doi = {10.1115/GT2019-91284},
isbn = {978-0-7918-5856-1},
year = {2019},
date = {2019-11-05},
volume = {Volume 2B: Turbomachinery},
number = {GT2019-91284},
publisher = {ASME},
organization = {ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition June 17–21, 2019 Phoenix, Arizona, USA},
abstract = {This paper deals with the design of passive control devices for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. A novel kind of device is introduced which consists of shelf-like fences to be added to the blade surface. Such a device is intended to contrast the development of secondary flows, thus reducing losses and flow turning deviation with respect to the straight blade.
In this second part, an experimental campaign on a linear cascade is presented which is aimed at proving the beneficial impact of the blade fences. Experiments were carried out on a low-speed test-rig, equipped with a large scale blade representative of the stators of the engine-like environment considered in part I. Measurements are mainly focused on the stator losses and on the flow field at the stator exit. The performance of the blade fences was evaluated by comparing the straight cascade and the fenced ones. The measurements highlighted the impact of the blade fences on the development of the secondary flows, affecting both the stator losses and the non-uniformity of the flow field over the exit plane, which, in the actual stage environment, impacts the operation of the downstream blade row. Moreover, the comparison between CFD and experiments proved the accuracy of the CFD setup, thus suggesting its reliability in predicting the stage performance in the engine-like configuration.},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
This paper deals with the design of passive control devices for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. A novel kind of device is introduced which consists of shelf-like fences to be added to the blade surface. Such a device is intended to contrast the development of secondary flows, thus reducing losses and flow turning deviation with respect to the straight blade.
In this second part, an experimental campaign on a linear cascade is presented which is aimed at proving the beneficial impact of the blade fences. Experiments were carried out on a low-speed test-rig, equipped with a large scale blade representative of the stators of the engine-like environment considered in part I. Measurements are mainly focused on the stator losses and on the flow field at the stator exit. The performance of the blade fences was evaluated by comparing the straight cascade and the fenced ones. The measurements highlighted the impact of the blade fences on the development of the secondary flows, affecting both the stator losses and the non-uniformity of the flow field over the exit plane, which, in the actual stage environment, impacts the operation of the downstream blade row. Moreover, the comparison between CFD and experiments proved the accuracy of the CFD setup, thus suggesting its reliability in predicting the stage performance in the engine-like configuration.
In this second part, an experimental campaign on a linear cascade is presented which is aimed at proving the beneficial impact of the blade fences. Experiments were carried out on a low-speed test-rig, equipped with a large scale blade representative of the stators of the engine-like environment considered in part I. Measurements are mainly focused on the stator losses and on the flow field at the stator exit. The performance of the blade fences was evaluated by comparing the straight cascade and the fenced ones. The measurements highlighted the impact of the blade fences on the development of the secondary flows, affecting both the stator losses and the non-uniformity of the flow field over the exit plane, which, in the actual stage environment, impacts the operation of the downstream blade row. Moreover, the comparison between CFD and experiments proved the accuracy of the CFD setup, thus suggesting its reliability in predicting the stage performance in the engine-like configuration.
Giovannini, Matteo; Rubechini, Filippo; Marconcini, Michele; Arnone, Andrea; Bertini, Francesco
Reducing Secondary Flow Losses in Low-Pressure Turbines: The Snaked Blade Journal Article
In: Int. J. Turbomachinery Propulsion and Power, vol. 4, no. 3, 2019, (This paper is an extended version of the paper published in Proceedings of the European Turbomachinery Conference, ETC13, Lausanne, Switzerland, 8–12 April 2019; Paper No. 338).
@article{1023,
title = {Reducing Secondary Flow Losses in Low-Pressure Turbines: The Snaked Blade},
author = {Matteo Giovannini and Filippo Rubechini and Michele Marconcini and Andrea Arnone and Francesco Bertini},
editor = {MDPI},
url = {https://www.mdpi.com/2504-186X/4/3/28/htm},
doi = {10.3390/ijtpp4030028},
year = {2019},
date = {2019-08-21},
journal = {Int. J. Turbomachinery Propulsion and Power},
volume = {4},
number = {3},
address = {Lausanne (CH), 8-12 April 2019},
abstract = {This paper presents an innovative design for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. Starting from a state-of-the-art LPT stage, a local reshaping of the stator blade was introduced in the end-wall region in order to oppose the flow turning deviation. This resulted in an optimal stator shape, able to provide a more uniform exit flow angle. The detailed comparison between the baseline stator and the redesigned one allowed for pointing out that the rotor row performance increased thanks to the more uniform inlet flow, while the stator losses were not significantly affected. Moreover, it was possible to derive some design rules and to devise a general blade shape, named ‘snaked’, able to ensure such results. This generalization translated in an effective parametric description of the ‘snaked’ shape, in which few parameters are sufficient to describe the optimal shape modification starting from a conventional design. The “snaked” blade concept and its design have been patented by Avio Aero. The stator redesign was then applied to a whole LPT module in order to evaluate the potential benefit of the ‘snaked’ design on the overall turbine performance. Finally, the design was validated by means of an experimental campaign concerning the stator blade. The spanwise distributions of the flow angle and pressure loss coefficient at the stator exit proved the effectiveness of the redesign in providing a more uniform flow to the successive row, while preserving the original stator losses.},
note = {This paper is an extended version of the paper published in Proceedings of the European Turbomachinery Conference, ETC13, Lausanne, Switzerland, 8–12 April 2019; Paper No. 338},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This paper presents an innovative design for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. Starting from a state-of-the-art LPT stage, a local reshaping of the stator blade was introduced in the end-wall region in order to oppose the flow turning deviation. This resulted in an optimal stator shape, able to provide a more uniform exit flow angle. The detailed comparison between the baseline stator and the redesigned one allowed for pointing out that the rotor row performance increased thanks to the more uniform inlet flow, while the stator losses were not significantly affected. Moreover, it was possible to derive some design rules and to devise a general blade shape, named ‘snaked’, able to ensure such results. This generalization translated in an effective parametric description of the ‘snaked’ shape, in which few parameters are sufficient to describe the optimal shape modification starting from a conventional design. The “snaked” blade concept and its design have been patented by Avio Aero. The stator redesign was then applied to a whole LPT module in order to evaluate the potential benefit of the ‘snaked’ design on the overall turbine performance. Finally, the design was validated by means of an experimental campaign concerning the stator blade. The spanwise distributions of the flow angle and pressure loss coefficient at the stator exit proved the effectiveness of the redesign in providing a more uniform flow to the successive row, while preserving the original stator losses.
Cozzi, Lorenzo; Rubechini, Filippo; Giovannini, Matteo; Marconcini, Michele; Arnone, Andrea; Schneider, Andrea; Astrua, Pio
Capturing Radial Mixing in Axial Compressors With Computational Fluid Dynamics Journal Article
In: ASME Journal of Turbomachinery, vol. 141, no. 3, pp. 9, 2019, ISBN: 0889-504X.
@article{1020,
title = {Capturing Radial Mixing in Axial Compressors With Computational Fluid Dynamics},
author = {Lorenzo Cozzi and Filippo Rubechini and Matteo Giovannini and Michele Marconcini and Andrea Arnone and Andrea Schneider and Pio Astrua},
url = {https://asmedigitalcollection.asme.org/turbomachinery/article/141/3/031012/475779/Capturing-Radial-Mixing-in-Axial-Compressors-With},
doi = {10.1115/1.4041738},
isbn = {0889-504X},
year = {2019},
date = {2019-01-21},
journal = {ASME Journal of Turbomachinery},
volume = {141},
number = {3},
pages = {9},
abstract = {The current industrial standard for numerical simulations of axial compressors is the steady Reynolds-averaged Navier–Stokes (RANS) approach. Besides the well-known limitations of mixing planes, namely their inherent inability to capture the potential interaction and the wakes from the upstream blades, there is another flow feature which is lost, and which is a major accountable for the radial mixing: the transport of streamwise vorticity. Streamwise vorticity is generated for various reasons, mainly associated with secondary and tip-clearance flows. A strong link exists between the strain field associated with the vortices and the mixing augmentation: the strain field increases both the area available for mixing and the local gradients in fluid properties, which provide the driving potential for the mixing. In the rear compressor stages, due to high clearances and low aspect ratios, only accounting for the development of secondary and clearance flow structures, it is possible to properly predict the spanwise mixing. In this work, the results of steady and unsteady simulations on a heavy-duty axial compressor are compared with experimental data. Adopting an unsteady framework, the enhanced mixing in the rear stages is properly captured, in remarkable agreement with experimental distributions. On the contrary, steady analyses strongly underestimate the radial transport. It is inferred that the streamwise vorticity associated with clearance flows is a major driver of radial mixing, and restraining it by pitch-averaging the flow at mixing planes is the reason why the steady approach cannot predict the radial transport in the rear part of the compressor.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The current industrial standard for numerical simulations of axial compressors is the steady Reynolds-averaged Navier–Stokes (RANS) approach. Besides the well-known limitations of mixing planes, namely their inherent inability to capture the potential interaction and the wakes from the upstream blades, there is another flow feature which is lost, and which is a major accountable for the radial mixing: the transport of streamwise vorticity. Streamwise vorticity is generated for various reasons, mainly associated with secondary and tip-clearance flows. A strong link exists between the strain field associated with the vortices and the mixing augmentation: the strain field increases both the area available for mixing and the local gradients in fluid properties, which provide the driving potential for the mixing. In the rear compressor stages, due to high clearances and low aspect ratios, only accounting for the development of secondary and clearance flow structures, it is possible to properly predict the spanwise mixing. In this work, the results of steady and unsteady simulations on a heavy-duty axial compressor are compared with experimental data. Adopting an unsteady framework, the enhanced mixing in the rear stages is properly captured, in remarkable agreement with experimental distributions. On the contrary, steady analyses strongly underestimate the radial transport. It is inferred that the streamwise vorticity associated with clearance flows is a major driver of radial mixing, and restraining it by pitch-averaging the flow at mixing planes is the reason why the steady approach cannot predict the radial transport in the rear part of the compressor.
2018
Riccietti, Elisa; Bellucci, Juri; Checcucci, Matteo; Marconcini, Michele; Arnone, Andrea
Support Vector Machine Classification Applied to the Parametric Design of Centrifugal Pumps Journal Article
In: Engineering Optimization, vol. 50, pp. 1304-1324, 2018, ISSN: 1029-0273.
@article{986,
title = {Support Vector Machine Classification Applied to the Parametric Design of Centrifugal Pumps},
author = {Elisa Riccietti and Juri Bellucci and Matteo Checcucci and Michele Marconcini and Andrea Arnone},
url = {http://www.tandfonline.com/doi/full/10.1080/0305215X.2017.1391801},
doi = {dx.doi.org/10.1080/0305215X.2017.1391801},
issn = {1029-0273},
year = {2018},
date = {2018-11-01},
journal = {Engineering Optimization},
volume = {50},
pages = {1304-1324},
abstract = {In this article the parametric design of centrifugal pumps is addressed. To deal with thisproblem, an approach based on coupling expensive Computational Fluid Dynamics (CFD) computations with Artificial Neural Networks (ANN) as a regression meta-model had been proposed in Checcucci et al. (2015), "A Novel Approach to Parametric Design of Centrifugal Pumps for a Wide Range of Specific Speeds."; ISAIF 12 paper n.121. Here, the previously proposed approach is improved by including also the use of Support Vector Machines (SVM) as a classification tool. The classification process is aimed at identifying parameters combinations corresponding to manufacturable machines among the much larger number of unfeasible ones. A binary classification problem on an unbalanced dataset has to be faced. Numerical tests show that the addition of this classification tool helps to considerably reduce the number of CFD computations required for the design, providing large savings in computational time.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this article the parametric design of centrifugal pumps is addressed. To deal with thisproblem, an approach based on coupling expensive Computational Fluid Dynamics (CFD) computations with Artificial Neural Networks (ANN) as a regression meta-model had been proposed in Checcucci et al. (2015), "A Novel Approach to Parametric Design of Centrifugal Pumps for a Wide Range of Specific Speeds."; ISAIF 12 paper n.121. Here, the previously proposed approach is improved by including also the use of Support Vector Machines (SVM) as a classification tool. The classification process is aimed at identifying parameters combinations corresponding to manufacturable machines among the much larger number of unfeasible ones. A binary classification problem on an unbalanced dataset has to be faced. Numerical tests show that the addition of this classification tool helps to considerably reduce the number of CFD computations required for the design, providing large savings in computational time.