2018
Giovannini, Matteo; Rubechini, Filippo; Marconcini, Michele; Simoni, Daniele; Yepmo, Vianney; Bertini, Francesco
In: ASME Journal of Turbomachinery, vol. 140, no. 11, pp. 111002 (12 pages), 2018, ISSN: 0889-504X.
@article{1019,
title = {Secondary Flows in Low-Pressure Turbines Cascades: Numerical and Experimental Investigation of the Impact of the Inner Part of the Boundary Layer},
author = {Matteo Giovannini and Filippo Rubechini and Michele Marconcini and Daniele Simoni and Vianney Yepmo and Francesco Bertini},
url = {http://turbomachinery.asmedigitalcollection.asme.org/article.aspx?articleid=2702055&resultClick=3},
doi = {10.1115/1.4041378},
issn = {0889-504X},
year = {2018},
date = {2018-10-01},
journal = {ASME Journal of Turbomachinery},
volume = {140},
number = {11},
pages = {111002 (12 pages)},
abstract = {Due to the low level of profile losses reached in low-pressure turbines (LPT) for turbofan applications, a renewed interest is devoted to other sources of loss, e.g., secondary losses. At the same time, the adoption of high-lift profiles has reinforced the importance of these losses. A great attention, therefore, is dedicated to reliable prediction methods and to the understanding of the mechanisms that drive the secondary flows. In this context, a numerical and experimental campaign on a state-of-the-art LPT cascade was carried out focusing on the impact of different inlet boundary layer (BL) profiles. First of all, detailed Reynolds Averaged Navier-Stokes (RANS) analyzes were carried out in order to establish dependable guidelines for the computational setup. Such analyzes also underlined the importance of the shape of the inlet BL very close to the endwall, suggesting tight requirements for the characterization of the experimental environment. The impact of the inlet BL on the secondary flow was experimentally investigated by varying the inlet profile very close to the endwall as well as on the external part of the BL. The effects on the cascade performance were evaluated by measuring the span-wise distributions of flow angle and total pressure losses. For all the inlet conditions, comparisons between Computational Fluid Dynamics (CFD) and experimental results are discussed. Besides providing guidelines for a proper numerical and experimental setup, the present paper underlines the importance of a detailed characterization of the inlet BL for an accurate assessment of the secondary flows.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Due to the low level of profile losses reached in low-pressure turbines (LPT) for turbofan applications, a renewed interest is devoted to other sources of loss, e.g., secondary losses. At the same time, the adoption of high-lift profiles has reinforced the importance of these losses. A great attention, therefore, is dedicated to reliable prediction methods and to the understanding of the mechanisms that drive the secondary flows. In this context, a numerical and experimental campaign on a state-of-the-art LPT cascade was carried out focusing on the impact of different inlet boundary layer (BL) profiles. First of all, detailed Reynolds Averaged Navier-Stokes (RANS) analyzes were carried out in order to establish dependable guidelines for the computational setup. Such analyzes also underlined the importance of the shape of the inlet BL very close to the endwall, suggesting tight requirements for the characterization of the experimental environment. The impact of the inlet BL on the secondary flow was experimentally investigated by varying the inlet profile very close to the endwall as well as on the external part of the BL. The effects on the cascade performance were evaluated by measuring the span-wise distributions of flow angle and total pressure losses. For all the inlet conditions, comparisons between Computational Fluid Dynamics (CFD) and experimental results are discussed. Besides providing guidelines for a proper numerical and experimental setup, the present paper underlines the importance of a detailed characterization of the inlet BL for an accurate assessment of the secondary flows.
Cozzi, Lorenzo; Rubechini, Filippo; Giovannini, Matteo; Marconcini, Michele; Arnone, Andrea; Schneider, Andrea; Astrua, Pio
Capturing Radial Mixing in Axial Compressors with CFD Conference
ASME Turbo Expo 2018: Turbine Technical Conference and Exposition, vol. Volume 2C: Turbomachinery, ASME ASME, Oslo, Norway, 2018, ISBN: 978-0-7918-5101-2, (paper GT2018-75942).
@conference{1001,
title = {Capturing Radial Mixing in Axial Compressors with CFD},
author = {Lorenzo Cozzi and Filippo Rubechini and Matteo Giovannini and Michele Marconcini and Andrea Arnone and Andrea Schneider and Pio Astrua},
url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2700721&resultClick=3},
doi = {10.1115/GT2018-75942},
isbn = {978-0-7918-5101-2},
year = {2018},
date = {2018-01-01},
booktitle = {ASME Turbo Expo 2018: Turbine Technical Conference and Exposition},
volume = {Volume 2C: Turbomachinery},
pages = {pp. V02CT42A025; 11 pages},
publisher = {ASME},
address = {Oslo, Norway},
organization = {ASME},
abstract = {Due to the generally high stage and blade count, the current standard industrially adopted to perform numerical simulations on multistage axial compressors is the steady-state analysis based on the Reynolds-averaged Navier-Stokes approach (RANS), where the coupling between adjacent rows is handled by means of mixing planes. In addition to the well-known limitations of a steady-state picture of the flow, namely its inherent inability to capture the potential interaction and the wakes from the upstream blades, there is another flow feature which is lost through a mixing-plane, and which is believed to be a major accountable for the radial mixing: the transport of stream-wise vorticity. Streamwise vorticity arises throughout a compressor for various reasons, mainly associated with secondary and tip-clearance flows. A strong link does exist between the strain field associated with the transported 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 mixing itself. Especially for the rear stages of a multistage axial compressor, due to high clearances and low aspect ratios, only accounting for the development along the meridional path of secondary and clearance flow structures (e.g. running an unsteady computation) it is possible to properly predict the spanwise mixing. Within this paper, the results of steady and unsteady simulations performed on a heavy-duty multistage axial compressor of Ansaldo Energia fleet are compared with experimental data, showing the importance of modelling the unsteady interactions in capturing the radial mixing. This compressor was selected because of the enhanced radial mixing effect experimentally measured in its high-pressure section.},
note = {paper GT2018-75942},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Due to the generally high stage and blade count, the current standard industrially adopted to perform numerical simulations on multistage axial compressors is the steady-state analysis based on the Reynolds-averaged Navier-Stokes approach (RANS), where the coupling between adjacent rows is handled by means of mixing planes. In addition to the well-known limitations of a steady-state picture of the flow, namely its inherent inability to capture the potential interaction and the wakes from the upstream blades, there is another flow feature which is lost through a mixing-plane, and which is believed to be a major accountable for the radial mixing: the transport of stream-wise vorticity. Streamwise vorticity arises throughout a compressor for various reasons, mainly associated with secondary and tip-clearance flows. A strong link does exist between the strain field associated with the transported 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 mixing itself. Especially for the rear stages of a multistage axial compressor, due to high clearances and low aspect ratios, only accounting for the development along the meridional path of secondary and clearance flow structures (e.g. running an unsteady computation) it is possible to properly predict the spanwise mixing. Within this paper, the results of steady and unsteady simulations performed on a heavy-duty multistage axial compressor of Ansaldo Energia fleet are compared with experimental data, showing the importance of modelling the unsteady interactions in capturing the radial mixing. This compressor was selected because of the enhanced radial mixing effect experimentally measured in its high-pressure section.
Giovannini, Matteo; Rubechini, Filippo; Marconcini, Michele; Simoni, Daniele; Yepmo, Vianney; Bertini, Francesco
ASME Turbo Expo 2018: Turbine Technical Conference and Exposition, vol. Volume 2B: Turbomachinery, ASME ASME, Oslo, Norway, 2018, ISBN: 978-079185100-5, (paper GT2018-76737).
@conference{1000,
title = {Secondary Flows in LPT Cascades: Numerical and Experimental Investigation of the Impact of the Inner Part of the Boundary Layer},
author = {Matteo Giovannini and Filippo Rubechini and Michele Marconcini and Daniele Simoni and Vianney Yepmo and Francesco Bertini},
url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2700647},
doi = {10.1115/GT2018-76737},
isbn = {978-079185100-5},
year = {2018},
date = {2018-01-01},
booktitle = {ASME Turbo Expo 2018: Turbine Technical Conference and Exposition},
volume = {Volume 2B: Turbomachinery},
pages = {pp. V02BT41A027; 13 pages},
publisher = {ASME},
address = {Oslo, Norway},
organization = {ASME},
abstract = {Due to the low level of profile losses already reached in the design of modern low-pressure turbines for turbofan applications, a renewed interest is devoted to the other sources of loss, and namely to the secondary losses. At the same time, the importance of secondary losses has been reinforced by the current design trend towards high-lift profiles. A great attention, therefore, is dedicated to reliable and effective prediction methods as well as on the correct understanding of the mechanisms that drive the secondary flows. In this context, a systematic numerical and experimental campaign was carried out focusing on the impact of different inlet boundary layer (BL) profiles and considering a state-of-the-art low-pressure turbine cascade. Starting from a computational environment representative of a design standard, detailed RANS analyses were carried out in order to establish dependable guidelines for the computational setup. As a major result, such analyses also underlined the importance of the shape of the inlet BL very close to the endwall, hence suggesting tight requirements for the characterization of the experimental environment. The impact of the inlet BL profile on the secondary flow development was experimentally investigated by varying the profile shape very close to the endwall as well as on the external part with respect to a reference condition. The effects on the cascade performance were evaluated focusing on the intensity of the over- under-turning as well as on the associated losses (intensity and penetration) by measuring the span-wise distributions of flow angle and total pressure losses at the cascade exit plane. For all the inlet conditions, comparisons between CFD and experimental results are discussed. Besides providing guidelines for a proper numerical and experimental setup, the present paper underlines the importance of a detailed characterization of the inlet BL for an accurate assessment of the secondary flows. From a broader perspective, when aiming at reproducing (numerically or experimentally) a real engine environment, this suggests that an in-depth matching of the inlet profiles is crucial for reliable estimates of the secondary losses.},
note = {paper GT2018-76737},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Due to the low level of profile losses already reached in the design of modern low-pressure turbines for turbofan applications, a renewed interest is devoted to the other sources of loss, and namely to the secondary losses. At the same time, the importance of secondary losses has been reinforced by the current design trend towards high-lift profiles. A great attention, therefore, is dedicated to reliable and effective prediction methods as well as on the correct understanding of the mechanisms that drive the secondary flows. In this context, a systematic numerical and experimental campaign was carried out focusing on the impact of different inlet boundary layer (BL) profiles and considering a state-of-the-art low-pressure turbine cascade. Starting from a computational environment representative of a design standard, detailed RANS analyses were carried out in order to establish dependable guidelines for the computational setup. As a major result, such analyses also underlined the importance of the shape of the inlet BL very close to the endwall, hence suggesting tight requirements for the characterization of the experimental environment. The impact of the inlet BL profile on the secondary flow development was experimentally investigated by varying the profile shape very close to the endwall as well as on the external part with respect to a reference condition. The effects on the cascade performance were evaluated focusing on the intensity of the over- under-turning as well as on the associated losses (intensity and penetration) by measuring the span-wise distributions of flow angle and total pressure losses at the cascade exit plane. For all the inlet conditions, comparisons between CFD and experimental results are discussed. Besides providing guidelines for a proper numerical and experimental setup, the present paper underlines the importance of a detailed characterization of the inlet BL for an accurate assessment of the secondary flows. From a broader perspective, when aiming at reproducing (numerically or experimentally) a real engine environment, this suggests that an in-depth matching of the inlet profiles is crucial for reliable estimates of the secondary losses.
Peruzzi, Lorenzo; Bellucci, Juri; Pinelli, Lorenzo; Marconcini, Michele; Gatta, G; Colatoni, S; Abhimanyu, S; Natale, G
Flutter-free design of aeroderivative gas turbine nozzles with simplified aero-mechanical models Conference
15th International Symposium on Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines (ISUAAAT), September 23-27, Oxford, UK, 2018, (paper ISUAAAT15-037).
@conference{1016,
title = {Flutter-free design of aeroderivative gas turbine nozzles with simplified aero-mechanical models},
author = {Lorenzo Peruzzi and Juri Bellucci and Lorenzo Pinelli and Michele Marconcini and G Gatta and S Colatoni and S Abhimanyu and G Natale},
year = {2018},
date = {2018-01-01},
booktitle = {15th International Symposium on Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines (ISUAAAT)},
address = {September 23-27, Oxford, UK},
abstract = {This work presents a simplified procedure to design a flutter free
airfoil geometry for aeroderivative gas turbine stator blade rows. The
common workflow for a fully 3D flutter numerical assessment with an
uncoupled method firstly involves a FE modal analysis to obtain the
airfoil mode shapes which will be used for unsteady aeroelastic
computations with moving airfoil. Nozzle geometries are usually very
complex: airfoils in a packet configuration and different mechanical
features needed to attach the packet itself to the turbine casing make
the structural meshing a not trivial task.
The aim of this paper is to demonstrate how, in the early
aero-mechanical design phases simplified models including only the
airfoil geometry and the endwalls chunks can be efficiently used to
design flutter-free components. First of all, detailed comparisons
between modal results from full and simplified mechanical models have
been performed. Then, flutter computations have been carried out using
modal results both from the full mechanical model (the sector or packet
model) and two different simplified models (single airfoil models).
Finally, flutter results in terms of logarithmic decrement curves will
be presented, showing the capability of this approach to guarantee
flutter free geometries even from the early design stages. This aspect
is essential to avoid bladerow redesign due to flutter issues which may
occur during the final design of the airfoil.},
note = {paper ISUAAAT15-037},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
This work presents a simplified procedure to design a flutter free
airfoil geometry for aeroderivative gas turbine stator blade rows. The
common workflow for a fully 3D flutter numerical assessment with an
uncoupled method firstly involves a FE modal analysis to obtain the
airfoil mode shapes which will be used for unsteady aeroelastic
computations with moving airfoil. Nozzle geometries are usually very
complex: airfoils in a packet configuration and different mechanical
features needed to attach the packet itself to the turbine casing make
the structural meshing a not trivial task.
The aim of this paper is to demonstrate how, in the early
aero-mechanical design phases simplified models including only the
airfoil geometry and the endwalls chunks can be efficiently used to
design flutter-free components. First of all, detailed comparisons
between modal results from full and simplified mechanical models have
been performed. Then, flutter computations have been carried out using
modal results both from the full mechanical model (the sector or packet
model) and two different simplified models (single airfoil models).
Finally, flutter results in terms of logarithmic decrement curves will
be presented, showing the capability of this approach to guarantee
flutter free geometries even from the early design stages. This aspect
is essential to avoid bladerow redesign due to flutter issues which may
occur during the final design of the airfoil.
airfoil geometry for aeroderivative gas turbine stator blade rows. The
common workflow for a fully 3D flutter numerical assessment with an
uncoupled method firstly involves a FE modal analysis to obtain the
airfoil mode shapes which will be used for unsteady aeroelastic
computations with moving airfoil. Nozzle geometries are usually very
complex: airfoils in a packet configuration and different mechanical
features needed to attach the packet itself to the turbine casing make
the structural meshing a not trivial task.
The aim of this paper is to demonstrate how, in the early
aero-mechanical design phases simplified models including only the
airfoil geometry and the endwalls chunks can be efficiently used to
design flutter-free components. First of all, detailed comparisons
between modal results from full and simplified mechanical models have
been performed. Then, flutter computations have been carried out using
modal results both from the full mechanical model (the sector or packet
model) and two different simplified models (single airfoil models).
Finally, flutter results in terms of logarithmic decrement curves will
be presented, showing the capability of this approach to guarantee
flutter free geometries even from the early design stages. This aspect
is essential to avoid bladerow redesign due to flutter issues which may
occur during the final design of the airfoil.
Amato, Giorgio; Giovannini, Matteo; Marconcini, Michele; Arnone, Andrea
Unsteady Methods Applied to a Transonic Aeronautical Gas Turbine Stage Journal Article
In: Energy Procedia, vol. 148, pp. 74-81, 2018, ISSN: 1876-6102, (ATI 2018 – 73rd Conference of the Italian Thermal Machines Engineering Association).
@article{1011,
title = {Unsteady Methods Applied to a Transonic Aeronautical Gas Turbine Stage},
author = {Giorgio Amato and Matteo Giovannini and Michele Marconcini and Andrea Arnone},
url = {https://www.sciencedirect.com/science/article/pii/S1876610218303229},
doi = {10.1016/j.egypro.2018.08.032},
issn = {1876-6102},
year = {2018},
date = {2018-01-01},
journal = {Energy Procedia},
volume = {148},
pages = {74-81},
address = {Pisa, Italy, 12-14 September},
abstract = {The importance of considering the unsteady effects in aeronautical engine design has brought to the implementation of simplified unsteady CFD models to respect the temporal restrictions of design cycles. A comparison among steady, Non-Linear Harmonic (NLH) and Full-Annulus (FA) methods has been carried out analyzing the transonic turbine stage CT3, experimentally studied at von Karman Institute for Fluid Dynamics. The understanding of the unsteady phenomena is fundamental to increase the engine efficiency and is precluded in steady calculations. As the computational cost of NLH calculations is of the same order of magnitude of steady ones, it represents a valid and competitive option in a turbine design process.},
note = {ATI 2018 - 73rd Conference of the Italian Thermal Machines Engineering Association},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The importance of considering the unsteady effects in aeronautical engine design has brought to the implementation of simplified unsteady CFD models to respect the temporal restrictions of design cycles. A comparison among steady, Non-Linear Harmonic (NLH) and Full-Annulus (FA) methods has been carried out analyzing the transonic turbine stage CT3, experimentally studied at von Karman Institute for Fluid Dynamics. The understanding of the unsteady phenomena is fundamental to increase the engine efficiency and is precluded in steady calculations. As the computational cost of NLH calculations is of the same order of magnitude of steady ones, it represents a valid and competitive option in a turbine design process.
2017
Becciani, Michele; Bianchini, Alessandro; Checcucci, Matteo; Ferrari, Lorenzo; Luca, Michele De; Marmorini, Luca; Arnone, Andrea; Ferrara, Giovanni
13th International Conference on Engines & Vehicles, September 10-14, 2017, Capri, Italy, 2017, (SAE Technical Paper 2017-24-0020).
@conference{999,
title = {A Pre-Design Model to Estimate the Effect of Variable Inlet Guide Vanes on the Performance Map of a Centrifugal Compressor for Automotive Applications},
author = {Michele Becciani and Alessandro Bianchini and Matteo Checcucci and Lorenzo Ferrari and Michele De Luca and Luca Marmorini and Andrea Arnone and Giovanni Ferrara},
url = {http://papers.sae.org/2017-24-0020/},
doi = {10.4271/2017-24-0020},
year = {2017},
date = {2017-09-01},
booktitle = {13th International Conference on Engines & Vehicles},
address = {September 10-14, 2017, Capri, Italy},
abstract = {The onset of aerodynamic instabilities in proximity of the left margin of the operating curve represents one of the main limitations for centrifugal compressors in turbocharging applications. An anticipated stall/surge onset is indeed particularly detrimental at those high boost pressures that are typical of engine downsizing applications using a turbocharger. Several stabilization techniques have been investigated so far to increase the rangeability of the compressor without excessively reducing the efficiency. One of the most exploited solutions is represented by the use of upstream axial variable inlet guide vanes (VIGV) to impart a pre-whirl angle to the inlet flow. In the pre-design phase of a new stage or when selecting, for example, an existing unit from an industrial catalogue, it is however not easy to get a prompt estimation of the attended modifications induced by the VIGV on the performance map of the compressor.A simplified model to this end is presented in the study. Figuring out a typical industrial pre-design phase, the model assumes the availability of the original performance data of the compressor without pre-whirl and only very few geometrical parameters. Based on fluid dynamic considerations and some additional models and correlations, a procedure is defined to correct the attended stage pressure ratio and efficiency as a function of the pre-whirl angle imposed by the VIGV. The model has been successfully validated using an experimental literature case study and is thought to represent a new useful preliminary tool for turbocharger designers.},
note = {SAE Technical Paper 2017-24-0020},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
The onset of aerodynamic instabilities in proximity of the left margin of the operating curve represents one of the main limitations for centrifugal compressors in turbocharging applications. An anticipated stall/surge onset is indeed particularly detrimental at those high boost pressures that are typical of engine downsizing applications using a turbocharger. Several stabilization techniques have been investigated so far to increase the rangeability of the compressor without excessively reducing the efficiency. One of the most exploited solutions is represented by the use of upstream axial variable inlet guide vanes (VIGV) to impart a pre-whirl angle to the inlet flow. In the pre-design phase of a new stage or when selecting, for example, an existing unit from an industrial catalogue, it is however not easy to get a prompt estimation of the attended modifications induced by the VIGV on the performance map of the compressor.A simplified model to this end is presented in the study. Figuring out a typical industrial pre-design phase, the model assumes the availability of the original performance data of the compressor without pre-whirl and only very few geometrical parameters. Based on fluid dynamic considerations and some additional models and correlations, a procedure is defined to correct the attended stage pressure ratio and efficiency as a function of the pre-whirl angle imposed by the VIGV. The model has been successfully validated using an experimental literature case study and is thought to represent a new useful preliminary tool for turbocharger designers.
Marconcini, Michele; Bianchini, Alessandro; Checcucci, Matteo; Ferrara, Giovanni; Arnone, Andrea; Ferrari, Lorenzo; Biliotti, Davide; Rubino, Dante Tommaso
In: ASME Journal of Turbomachinery, vol. 139, pp. 021001, 2017, ISSN: 0889-504X.
@article{987,
title = {A Three-Dimensional Time-Accurate Computational Fluid Dynamics Simulation of the Flow Field Inside a Vaneless Diffuser During Rotating Stall Conditions},
author = {Michele Marconcini and Alessandro Bianchini and Matteo Checcucci and Giovanni Ferrara and Andrea Arnone and Lorenzo Ferrari and Davide Biliotti and Dante Tommaso Rubino},
url = {http://turbomachinery.asmedigitalcollection.asme.org/article.aspx?articleid=2551877},
doi = {dx.doi.org/10.1115/1.4034633},
issn = {0889-504X},
year = {2017},
date = {2017-09-01},
journal = {ASME Journal of Turbomachinery},
volume = {139},
pages = {021001},
abstract = {An accurate characterization of rotating stall in terms of inception modality, flow structures, and stabilizing force is one of the key goals for high-pressure centrifugal compressors. The unbalanced pressure field that is generated within the diffuser can be in fact connected to a non-negligible aerodynamic force and then to the onset of detrimental sub-synchronous vibrations which can prevent the machine from operating beyond this limit. An inner comprehension on how the induced flow pattern in these conditions affects the performance of the impeller and its mechanical stability can therefore lead to the development of a more effective regulation system able to mitigate the effects of the phenomenon and extend the left-side margin of the operating curve. In the present study, a 3D-unsteady CFD approach was applied to the simulation of a radial stage model including the impeller, the vaneless diffuser and the return channel. Simulations were carried out with the TRAF code of the University of Florence. The tested rotor was an industrial impeller operating at high peripheral Mach number, for which unique experimental pressure measurements, including the spatial reconstruction of the pressure field at the diffuser inlet, were available. The comparison between experiments and simulations showed a good matching and corroborated the CFD capabilities in correctly describing also some of the complex unsteady phenomena taking place in proximity of the left margin of the operating curve.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
An accurate characterization of rotating stall in terms of inception modality, flow structures, and stabilizing force is one of the key goals for high-pressure centrifugal compressors. The unbalanced pressure field that is generated within the diffuser can be in fact connected to a non-negligible aerodynamic force and then to the onset of detrimental sub-synchronous vibrations which can prevent the machine from operating beyond this limit. An inner comprehension on how the induced flow pattern in these conditions affects the performance of the impeller and its mechanical stability can therefore lead to the development of a more effective regulation system able to mitigate the effects of the phenomenon and extend the left-side margin of the operating curve. In the present study, a 3D-unsteady CFD approach was applied to the simulation of a radial stage model including the impeller, the vaneless diffuser and the return channel. Simulations were carried out with the TRAF code of the University of Florence. The tested rotor was an industrial impeller operating at high peripheral Mach number, for which unique experimental pressure measurements, including the spatial reconstruction of the pressure field at the diffuser inlet, were available. The comparison between experiments and simulations showed a good matching and corroborated the CFD capabilities in correctly describing also some of the complex unsteady phenomena taking place in proximity of the left margin of the operating curve.
Marconcini, Michele; Bianchini, Alessandro; Checcucci, Matteo; Biliotti, Davide; Giachi, Marco; Rubino, Dante Tommaso; Arnone, Andrea; Carnevale, Ennio Antonio; Ferrari, Lorenzo; Ferrara, Giovanni
Determinazione della forza indotta dallo stallo rotante nei compressori centrifughi con diffusore liscio Journal Article
In: La Termotecnica, vol. 3, pp. 50-54, 2017, ISSN: 0040-3725.
@article{996,
title = {Determinazione della forza indotta dallo stallo rotante nei compressori centrifughi con diffusore liscio},
author = {Michele Marconcini and Alessandro Bianchini and Matteo Checcucci and Davide Biliotti and Marco Giachi and Dante Tommaso Rubino and Andrea Arnone and Ennio Antonio Carnevale and Lorenzo Ferrari and Giovanni Ferrara},
url = {http://www.verticale.net/determinazione-della-forza-indotta-dallo-stallo-11019},
issn = {0040-3725},
year = {2017},
date = {2017-05-01},
journal = {La Termotecnica},
volume = {3},
pages = {50-54},
abstract = {Una corretta stima della forza destabilizzante indotta dallo stallo rotante è un elemento chiave per i produttori di macchine industriali in vista in vista di una estensione del margine sinistro dei compressori centrifughi. In questo studio, i risultati di alcune simulazioni 3D instazionarie sono stati usati per stimare la forza di stallo su uno stadio e paragonare tale stima a quella ottenuta con un approccio che ricalca quello sperimentale generalmente usato al banco prova basato su sensori dinamici di pressione. L'analisi ha mostrato che: a) il metodo sperimentale, basato su media d'assieme, è in grado di fornire risultati accurati, nonostante alcune ipotesi semplificative; b) il contributo della quantità di moto risulta trascurabile per l'intensità della forza.
ESTIMATION OF THE AERODYNAMIC FORCE INDUCED BY VANELESS DIFFUSER ROTATING STALL IN CENTRIFUGAL COMPRESSOR STAGES
A correct estimation of the destabilizing force due rotating stall is a key element for industrial manufacturers in view of an extension of the minimum flow limit of centrifugal compressor stages. In this study, the results of a 3D-unsteady CFD simulation were used to estimate the stall force on a stage and to compare it with the approximation obtained with a method similar to that usually employed at the test rig by means of dynamic pressure sensors. Results showed that: a) the experimental approach, using an ensemble average for transposing data from time to space domain, provides robust results; b) the momentum gives a negligible contribution to the intensity of the stall force.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Una corretta stima della forza destabilizzante indotta dallo stallo rotante è un elemento chiave per i produttori di macchine industriali in vista in vista di una estensione del margine sinistro dei compressori centrifughi. In questo studio, i risultati di alcune simulazioni 3D instazionarie sono stati usati per stimare la forza di stallo su uno stadio e paragonare tale stima a quella ottenuta con un approccio che ricalca quello sperimentale generalmente usato al banco prova basato su sensori dinamici di pressione. L’analisi ha mostrato che: a) il metodo sperimentale, basato su media d’assieme, è in grado di fornire risultati accurati, nonostante alcune ipotesi semplificative; b) il contributo della quantità di moto risulta trascurabile per l’intensità della forza.
ESTIMATION OF THE AERODYNAMIC FORCE INDUCED BY VANELESS DIFFUSER ROTATING STALL IN CENTRIFUGAL COMPRESSOR STAGES
A correct estimation of the destabilizing force due rotating stall is a key element for industrial manufacturers in view of an extension of the minimum flow limit of centrifugal compressor stages. In this study, the results of a 3D-unsteady CFD simulation were used to estimate the stall force on a stage and to compare it with the approximation obtained with a method similar to that usually employed at the test rig by means of dynamic pressure sensors. Results showed that: a) the experimental approach, using an ensemble average for transposing data from time to space domain, provides robust results; b) the momentum gives a negligible contribution to the intensity of the stall force.
ESTIMATION OF THE AERODYNAMIC FORCE INDUCED BY VANELESS DIFFUSER ROTATING STALL IN CENTRIFUGAL COMPRESSOR STAGES
A correct estimation of the destabilizing force due rotating stall is a key element for industrial manufacturers in view of an extension of the minimum flow limit of centrifugal compressor stages. In this study, the results of a 3D-unsteady CFD simulation were used to estimate the stall force on a stage and to compare it with the approximation obtained with a method similar to that usually employed at the test rig by means of dynamic pressure sensors. Results showed that: a) the experimental approach, using an ensemble average for transposing data from time to space domain, provides robust results; b) the momentum gives a negligible contribution to the intensity of the stall force.
Cozzi, Lorenzo; Rubechini, Filippo; Marconcini, Michele; Arnone, Andrea; Astrua, Pio; Schneider, Andrea; Silingardi, Andrea
Facing the Challenges in CFD Modelling of Multistage Axial Compressors Conference
ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition, vol. 2B: Turbomachinery, ASME ASME, Charlotte, NC, USA, 2017, ISBN: 978-0-7918-5079-4, (ASME paper GT2017-63240).
@conference{990,
title = {Facing the Challenges in CFD Modelling of Multistage Axial Compressors},
author = {Lorenzo Cozzi and Filippo Rubechini and Michele Marconcini and Andrea Arnone and Pio Astrua and Andrea Schneider and Andrea Silingardi},
url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleID=2649617},
doi = {10.1115/GT2017-63240},
isbn = {978-0-7918-5079-4},
year = {2017},
date = {2017-01-01},
booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition},
volume = {2B: Turbomachinery},
pages = {pp. V02BT41A007; 11 pages},
publisher = {ASME},
address = {Charlotte, NC, USA},
organization = {ASME},
abstract = {Multistage axial compressors have always been a great challenge for designers since the flow within these kind of machines, subjected to severe diffusion, is usually characterized by complex and widely developed 3D structures, especially next to the endwalls. The development of reliable numerical tools capable of providing an accurate prediction of the overall machine performance is one of the main research focus areas in the multistage axial compressor field. This paper is intended to present the strategy used to run numerical simulations on compressors achieved by the collaboration between the University of Florence and Ansaldo Energia. All peculiar aspects of the numerical setup are introduced, such as rotor/stator tip clearance modelling, simplified shroud leakage model, gas and turbulence models. Special attention is payed to the mixing planes adopted for steady-state computations because this is a crucial aspect of modern heavy-duty transonic multi stage axial compressors. In fact, these machines are characterized by small inter-row axial gaps and transonic flow in front stages, which both may affect non-reflectiveness and fluxes conservation across mixing planes. Moreover, the high stage count may lead to conservation issues of the main flow properties form inlet to outlet boundaries. Finally, the likely occurrence of part span flow reversal in the endwall regions affects the robustness of non-reflecting mixing plane models. The numerical setup has been validated on an existing machine produced and experimentally tested by Ansaldo Energia. In order to evaluate the impact on performance prediction of the mixing planes introduced in the steady-state computation, unsteady simulations of the whole compressor have been performed at different operating conditions. These calculations have been carried out both at the compressor design point and close to the surge-line to evaluate the effect of rotor/stator interaction along the compressor working line.},
note = {ASME paper GT2017-63240},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Multistage axial compressors have always been a great challenge for designers since the flow within these kind of machines, subjected to severe diffusion, is usually characterized by complex and widely developed 3D structures, especially next to the endwalls. The development of reliable numerical tools capable of providing an accurate prediction of the overall machine performance is one of the main research focus areas in the multistage axial compressor field. This paper is intended to present the strategy used to run numerical simulations on compressors achieved by the collaboration between the University of Florence and Ansaldo Energia. All peculiar aspects of the numerical setup are introduced, such as rotor/stator tip clearance modelling, simplified shroud leakage model, gas and turbulence models. Special attention is payed to the mixing planes adopted for steady-state computations because this is a crucial aspect of modern heavy-duty transonic multi stage axial compressors. In fact, these machines are characterized by small inter-row axial gaps and transonic flow in front stages, which both may affect non-reflectiveness and fluxes conservation across mixing planes. Moreover, the high stage count may lead to conservation issues of the main flow properties form inlet to outlet boundaries. Finally, the likely occurrence of part span flow reversal in the endwall regions affects the robustness of non-reflecting mixing plane models. The numerical setup has been validated on an existing machine produced and experimentally tested by Ansaldo Energia. In order to evaluate the impact on performance prediction of the mixing planes introduced in the steady-state computation, unsteady simulations of the whole compressor have been performed at different operating conditions. These calculations have been carried out both at the compressor design point and close to the surge-line to evaluate the effect of rotor/stator interaction along the compressor working line.
Bellucci, Juri; Rubechini, Filippo; Arnone, Andrea; Arcangeli, Lorenzo; Maceli, Nicola; Paradiso, Berardo; Gatti, Giacomo
Numerical and experimental investigation of axial gap variation in high pressure steam turbine stages Journal Article
In: Journal of Engineering for Gas Turbines and Power, vol. 139, pp. 052603 (9 pages), 2017, ISSN: 0742-4795.
@article{988,
title = {Numerical and experimental investigation of axial gap variation in high pressure steam turbine stages},
author = {Juri Bellucci and Filippo Rubechini and Andrea Arnone and Lorenzo Arcangeli and Nicola Maceli and Berardo Paradiso and Giacomo Gatti},
url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2580913},
doi = {dx.doi.org/10.1115/1.4035158},
issn = {0742-4795},
year = {2017},
date = {2017-01-01},
journal = {Journal of Engineering for Gas Turbines and Power},
volume = {139},
pages = {052603 (9 pages)},
abstract = {This work aims at investigating the impact of axial gap variation on aerodynamic performance of a HP steam turbine stage. Numerical and experimental campaigns were conducted on a 1.5-stage of a reaction steam turbine. This low speed rig was operated in different operating conditions. Two different configurations were studied, in which blades axial gap was varied in a range from 40% to 95%. Numerical analyses were carried out by means of three-dimensional, viscous, unsteady simulations, adopting measured inlet/outlet boundary conditions. Two set of measurements were performed. Steady measurements, from one hand, for global performance estimation of the whole turbine. Steady and unsteady measurements, on the other hand, were performed downstream of rotor row, in order to characterize the flow structures in this region. The fidelity of computational setup was proven by comparing numerical results to measurements. Main performance curves and span-wise distributions shown a good agreement in terms of both shape of curves/distributions and absolute values. Moreover, the comparison of two dimensional maps downstream of rotor row shown similar structures of the flow field. Finally, a comprehensive study of the axial gap effect on stage aerodynamic performance was carried out for four blade spacings, and five aspect ratios. The results pointed out how unsteady interaction between blade rows affects stage operation, in terms of pressure and flow angle distributions, as well as of secondary flows development. The combined effect of these aspects in determining the stage efficiency is investigated and discussed in detail.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This work aims at investigating the impact of axial gap variation on aerodynamic performance of a HP steam turbine stage. Numerical and experimental campaigns were conducted on a 1.5-stage of a reaction steam turbine. This low speed rig was operated in different operating conditions. Two different configurations were studied, in which blades axial gap was varied in a range from 40% to 95%. Numerical analyses were carried out by means of three-dimensional, viscous, unsteady simulations, adopting measured inlet/outlet boundary conditions. Two set of measurements were performed. Steady measurements, from one hand, for global performance estimation of the whole turbine. Steady and unsteady measurements, on the other hand, were performed downstream of rotor row, in order to characterize the flow structures in this region. The fidelity of computational setup was proven by comparing numerical results to measurements. Main performance curves and span-wise distributions shown a good agreement in terms of both shape of curves/distributions and absolute values. Moreover, the comparison of two dimensional maps downstream of rotor row shown similar structures of the flow field. Finally, a comprehensive study of the axial gap effect on stage aerodynamic performance was carried out for four blade spacings, and five aspect ratios. The results pointed out how unsteady interaction between blade rows affects stage operation, in terms of pressure and flow angle distributions, as well as of secondary flows development. The combined effect of these aspects in determining the stage efficiency is investigated and discussed in detail.