Simone Salvadori | Università degli Studi di Firenze (University of Florence) (original) (raw)
Papers by Simone Salvadori
This paper presents an investigation of the aerothermal performance of a modern un-shrouded high-... more This paper presents an investigation of the aerothermal performance of a modern un-shrouded high-pressure (HP) aero-engine turbine subject to nonuniform inlet temperature profile. The turbine used for this study was the MT1 turbine installed in the QinetiQ turbine test facility based in Farnborough (UK). The MT1 turbine is a full scale transonic HP turbine, and is operated in the test facility at the correct nondimensional conditions for aerodynamics and heat transfer. Datum experiments of aerothermal performance were conducted with uniform inlet conditions. Experiments with nonuniform inlet temperature were conducted with a temperature profile that had a nonuniformity in the radial direction defined by T max T min / T ¯ 0.355, and a nonuniformity in the circumferential direction defined by T max T min / T ¯ 0.14. This corresponds to an extreme point in the engine cycle, in an engine where the nonuniformity is dominated by the radial distribution. Accurate experimental area surveys of the turbine inlet and exit flows were conducted , and detailed heat transfer measurements were obtained on the blade surfaces and end-walls. These results are analyzed with the unsteady numerical data obtained using the in-house HybFlow code developed at the University of Firenze. Two particular aspects are highlighted in the discussion: prediction confidence for state of the art computational fluid dynamics (CFD) and impact of real conditions on stator-rotor thermal loading. The efficiency value obtained with the numerical analysis is compared with the experimental data and a 0.8% difference is found and discussed. A study of the flow field influence on the blade thermal load has also been detailed. It is shown that the hot streak migration mainly affects the rotor pressure side from 20% to 70% of the span, where the Nusselt number increases by a factor of 60% with respect to the uniform case. Furthermore , in this work, it has been found that a nonuniform temperature distribution is beneficial for the rotor tip, contrary to the results found in open literature. Although the hot streak is affected by the pressure gradient across the tip gap, the radial profile (which dominates the temperature profile being considered) is not fully mixed out in passing through the HP stage, and contributes significantly to cooling the turbine casing. A design approach not taking into account these effects will underestimate the rotor life near the tip and the thermal load at midspan. The temperature profile that has been used in both experiments and CFD is the first simulation of an extreme cycle point (more than twice the magnitude of distortion of all previous experimental studies): It represents an engine-takeoff condition combined with the full combustor cooling. This research was part of the EU funded Turbine AeroThermal External Flows 2 program.
This study presents an investigation of the impact of filleted edges variations on heat transfer.... more This study presents an investigation of the impact of filleted edges variations on heat transfer. In real gas turbines, sharp edges are an approximation, because of manufacturing tolerances and/or geometrical modifications occurring during operation. The value of fillet radius is not exactly known a priori. It can be assumed that a specific radius occurs with a probability following a probabilistic distribution.
This paper presents an investigation of the aerothermal performance of a modern unshrouded high-p... more This paper presents an investigation of the aerothermal performance of a modern unshrouded high-pressure (HP) aero-engine turbine subject to nonuniform inlet temperature profile. The turbine used for this study was the MT1 turbine installed in the QinetiQ turbine test facility based ...
Journal of Biophotonics, 2012
Proceeding of ETC10Th 2013
Gas Turbine are nowadays largely used for aircraft propulsion and land-based power genera- tion. ... more Gas Turbine are nowadays largely used for aircraft propulsion and land-based power genera- tion. The increased attention to environmental aspects has promoted research and development efforts both from manufacturers and research centres. The latest developments in turbine- cooling technologies play a critical role in the attempt to increase the efficiency and the specific power of the most advanced designs. Pin fin arrays, in particular, are widely used in jet en- gine application because of their ability to enhance cooling by providing extended surfaces for conduction and convection. They are also known to be an effective means to create turbulence which naturally increases heat transfer. Pin fin turbulators are typically located inside the trail- ing edge of high pressure turbine blade where they also act as a structural support. The optimum shapes and spacing of such elements are usually determined experimentally, or more recently, by using Computational Fluid Dynamics (CFD). On the other hand, the com- prehension of the real physics controlling the heat transfer enhancement process and the role played by the large scale vortical structures generated by the inserts, still represent a great chal- lenge for fluid mechanic researchers. The problem has been intensively investigated by Ames et al. (2005) by means of an experimental campaign on pin fin matrix. From the numerical point of view, the principal bottleneck of the CFD approach as applied to this kind ofmassively unsteady flow is related to the high computational cost and to the reliability of the turbulence models. The main objective of this work is to offer a critical analysis of the performance of a cooling device consisting of a pin fin turbulators geometry, as predicted by different CFD models of various complexity, using similar computational technology to integrate the corresponding gov- erning equations. Local velocity and turbulence distributions are presented and compared with available experimental data.
WSEAS transactions on FluidMechanics 2011 Volume D, Issue 4 , 2011
"Improvements in mean flow and performances simulation in turbomachinery has brought research to ... more "Improvements in mean flow and performances simulation in turbomachinery has brought research to focus more demanding topics like turbulence effects on turbines. Although overall performances are well predicted by Unsteady-RANS, other phenomena such as aerodynamic noise or transition need more accurate prediction of turbulent flow features. Thus different kinds of equation modeling other than URANS are needed to cope with this issue. The success of Detached-Eddy Simulation and Large-Eddy Simulation applications in reproducing physical behavior of flow turbulence is well documented in literature. Despite that, LES simulations are still computationally very expensive and their use for investigating industrial configurations requires a careful assessment of both numerical and closure modeling techniques. Moreover LES solvers are usually developed on a structured mesh topology for sake of simplicity of high-order schemes implementation.
Application to complex geometries like those of turbomachinery is therefore difficult. The present work addresses this issue considering the feasibility of converting an operative in-house URANS solver, widely validated for applicative purposes, into higher resolution DES and LES, in order to face turbulence computation of turbomachinery technical cases. The solver presents a 3D unstructured finite-volume formulation, which is kept in LES approach in order to handle complex geometries and it is developed to perform unsteady simulations on turbine stages. Preliminary assessment of the solver has been performed to evaluate and improve the accuracy of the convective fluxes discretization on an inviscid bump test case. First a DES-based approach has been implemented, as it is less computationally challenging and numerically demanding than LES. A square cylinder test case has been assessed and compared with experiments. Then, a pure LES with a Smagorinsky sub-grid scale model has been evaluated on the test case of incompressible periodic channel flow in order to assess the capability of the solver to correctly sustain a time developing turbulent field."
This paper presents an investigation of the aerothermal performance of a modern un-shrouded high-... more This paper presents an investigation of the aerothermal performance of a modern un-shrouded high-pressure (HP) aero-engine turbine subject to nonuniform inlet temperature profile. The turbine used for this study was the MT1 turbine installed in the QinetiQ turbine test facility based in Farnborough (UK). The MT1 turbine is a full scale transonic HP turbine, and is operated in the test facility at the correct nondimensional conditions for aerodynamics and heat transfer. Datum experiments of aerothermal performance were conducted with uniform inlet conditions. Experiments with nonuniform inlet temperature were conducted with a temperature profile that had a nonuniformity in the radial direction defined by T max T min / T ¯ 0.355, and a nonuniformity in the circumferential direction defined by T max T min / T ¯ 0.14. This corresponds to an extreme point in the engine cycle, in an engine where the nonuniformity is dominated by the radial distribution. Accurate experimental area surveys of the turbine inlet and exit flows were conducted , and detailed heat transfer measurements were obtained on the blade surfaces and end-walls. These results are analyzed with the unsteady numerical data obtained using the in-house HybFlow code developed at the University of Firenze. Two particular aspects are highlighted in the discussion: prediction confidence for state of the art computational fluid dynamics (CFD) and impact of real conditions on stator-rotor thermal loading. The efficiency value obtained with the numerical analysis is compared with the experimental data and a 0.8% difference is found and discussed. A study of the flow field influence on the blade thermal load has also been detailed. It is shown that the hot streak migration mainly affects the rotor pressure side from 20% to 70% of the span, where the Nusselt number increases by a factor of 60% with respect to the uniform case. Furthermore , in this work, it has been found that a nonuniform temperature distribution is beneficial for the rotor tip, contrary to the results found in open literature. Although the hot streak is affected by the pressure gradient across the tip gap, the radial profile (which dominates the temperature profile being considered) is not fully mixed out in passing through the HP stage, and contributes significantly to cooling the turbine casing. A design approach not taking into account these effects will underestimate the rotor life near the tip and the thermal load at midspan. The temperature profile that has been used in both experiments and CFD is the first simulation of an extreme cycle point (more than twice the magnitude of distortion of all previous experimental studies): It represents an engine-takeoff condition combined with the full combustor cooling. This research was part of the EU funded Turbine AeroThermal External Flows 2 program.
This study presents an investigation of the impact of filleted edges variations on heat transfer.... more This study presents an investigation of the impact of filleted edges variations on heat transfer. In real gas turbines, sharp edges are an approximation, because of manufacturing tolerances and/or geometrical modifications occurring during operation. The value of fillet radius is not exactly known a priori. It can be assumed that a specific radius occurs with a probability following a probabilistic distribution.
This paper presents an investigation of the aerothermal performance of a modern unshrouded high-p... more This paper presents an investigation of the aerothermal performance of a modern unshrouded high-pressure (HP) aero-engine turbine subject to nonuniform inlet temperature profile. The turbine used for this study was the MT1 turbine installed in the QinetiQ turbine test facility based ...
Journal of Biophotonics, 2012
Proceeding of ETC10Th 2013
Gas Turbine are nowadays largely used for aircraft propulsion and land-based power genera- tion. ... more Gas Turbine are nowadays largely used for aircraft propulsion and land-based power genera- tion. The increased attention to environmental aspects has promoted research and development efforts both from manufacturers and research centres. The latest developments in turbine- cooling technologies play a critical role in the attempt to increase the efficiency and the specific power of the most advanced designs. Pin fin arrays, in particular, are widely used in jet en- gine application because of their ability to enhance cooling by providing extended surfaces for conduction and convection. They are also known to be an effective means to create turbulence which naturally increases heat transfer. Pin fin turbulators are typically located inside the trail- ing edge of high pressure turbine blade where they also act as a structural support. The optimum shapes and spacing of such elements are usually determined experimentally, or more recently, by using Computational Fluid Dynamics (CFD). On the other hand, the com- prehension of the real physics controlling the heat transfer enhancement process and the role played by the large scale vortical structures generated by the inserts, still represent a great chal- lenge for fluid mechanic researchers. The problem has been intensively investigated by Ames et al. (2005) by means of an experimental campaign on pin fin matrix. From the numerical point of view, the principal bottleneck of the CFD approach as applied to this kind ofmassively unsteady flow is related to the high computational cost and to the reliability of the turbulence models. The main objective of this work is to offer a critical analysis of the performance of a cooling device consisting of a pin fin turbulators geometry, as predicted by different CFD models of various complexity, using similar computational technology to integrate the corresponding gov- erning equations. Local velocity and turbulence distributions are presented and compared with available experimental data.
WSEAS transactions on FluidMechanics 2011 Volume D, Issue 4 , 2011
"Improvements in mean flow and performances simulation in turbomachinery has brought research to ... more "Improvements in mean flow and performances simulation in turbomachinery has brought research to focus more demanding topics like turbulence effects on turbines. Although overall performances are well predicted by Unsteady-RANS, other phenomena such as aerodynamic noise or transition need more accurate prediction of turbulent flow features. Thus different kinds of equation modeling other than URANS are needed to cope with this issue. The success of Detached-Eddy Simulation and Large-Eddy Simulation applications in reproducing physical behavior of flow turbulence is well documented in literature. Despite that, LES simulations are still computationally very expensive and their use for investigating industrial configurations requires a careful assessment of both numerical and closure modeling techniques. Moreover LES solvers are usually developed on a structured mesh topology for sake of simplicity of high-order schemes implementation.
Application to complex geometries like those of turbomachinery is therefore difficult. The present work addresses this issue considering the feasibility of converting an operative in-house URANS solver, widely validated for applicative purposes, into higher resolution DES and LES, in order to face turbulence computation of turbomachinery technical cases. The solver presents a 3D unstructured finite-volume formulation, which is kept in LES approach in order to handle complex geometries and it is developed to perform unsteady simulations on turbine stages. Preliminary assessment of the solver has been performed to evaluate and improve the accuracy of the convective fluxes discretization on an inviscid bump test case. First a DES-based approach has been implemented, as it is less computationally challenging and numerically demanding than LES. A square cylinder test case has been assessed and compared with experiments. Then, a pure LES with a Smagorinsky sub-grid scale model has been evaluated on the test case of incompressible periodic channel flow in order to assess the capability of the solver to correctly sustain a time developing turbulent field."