External heat transfer on nozzle guide vanes under highly swirled combustor outlet flow

Cubeda, Simone; Mazzei, Lorenzo; Andreini, Antonio

doi:10.29008/etc2019-293

Cited by 4 publications

(7 citation statements)

References 14 publications

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“…However, this behavior is not observed for different span values: in fact, at 25 and 75% of the span, it can be noted that the RANS generally tends to assume values of adiabatic effectiveness that are higher than those of SBES, especially on the SS. This demonstrates that, as expected and already demonstrated in the literature [34,35], it is essential to include the effects of unsteadiness on turbulent mixing, which otherwise would be strongly under-predicted.…”

Section: Evaluation Of the Airfoil Loads And Adiabatic Effectivenesssupporting

confidence: 71%

“…The authors pointed out that SAS predicts better than RANS the recirculating region inside the combustor, which has a large impact over the resulting gas temperature at the turbine inlet and over the coolant and the main stream mixing process, even if it mildly affects the velocity field. As a matter of fact, even if RANS is sufficient to predict the aerodynamics of the turbine and to provide a reasonably accurate solution with a low computational effort [33], Scale-Resolving methods are required to assess satisfactorily the thermal behavior of the vanes, as demonstrated by subsequent works [34,35].…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study of Combustor-Turbine Interaction by Using Hybrid RANS-LES Approach

Tomasello

Andreini

Meloni³

et al. 2022

Volume 6A: Heat Transfer — Combustors; Film Cooling

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The complex flow field of gas turbine lean combustors is meant to reduce NOx emissions and maintain a stable flame by controlling the local temperature and promoting high turbulent mixing. Still, this may produce large flow and temperature unsteady distortions capable of disrupting the aerodynamics and heat transfer of the first high-pressure-turbine cooled nozzle. Therefore, the interaction between the combustion chamber and the turbine nozzle is analyzed first with the help of scale-resolving simulations that notably also include a realistic turbine nozzle cooling system. To determine the nature and severity of the interaction, and the risks associated to performing decoupled simulation, the results of the coupled computer simulation are analyzed and compared with those of decoupled simulations. In this case, the combustor is computed by replacing the turbine nozzle with a discharge convergent with the same throat area, and the conditions at the interface plane are used as inlet boundary conditions for a conventional RANS of the nozzle. The analyses of the coupled and decoupled simulation reveal that the combustion chamber is weakly affected by the presence of the nozzle, whereas the two thermal fields of the nozzle surface differ considerably, as well as the disruption of the film cooling by the incoming flow distortions.

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Section: Evaluation Of the Airfoil Loads And Adiabatic Effectivenesssupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Numerical Study of Combustor-Turbine Interaction by Using Hybrid RANS-LES Approach

Tomasello

Andreini

Meloni³

et al. 2022

Volume 6A: Heat Transfer — Combustors; Film Cooling

View full text Add to dashboard Cite

show abstract

“…As a consequence, it can be stated that CFD is satisfactorily replicating the coolant alternate spread on the higher/lower half of the PS/SS due to the main flow swirling structure, although there is yet wide margin for improvement. In fact, based on available data in the open literature, it is expected that more advanced CFD modelling techniques (such as scale-resolving methods) can help in overcoming the limitations of RANS in accurately reproducing the mixing between coolant and main streams [23] [32].…”

Section: Film-cooling Adiabatic Effectivenessmentioning

confidence: 99%

Numerical Prediction of Heat Transfer Coefficient and Adiabatic Effectiveness on a Nozzle Guide Vane With Representative Combustor Outflow

Tomasello

Andreini

Bacci

et al. 2022

Volume 6A: Heat Transfer — Combustors; Film Cooling

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The employment of lean-premix combustors in modern gas turbines allows to reduce NOx emissions by controlling the flame temperature at the expense of highly unsteady and strongly non-uniform flow fields which are necessary to stabilize the flame. This highly complex swirled flow field characterized by evident temperature distortions alters the aerodynamics and heat transfer in the first high pressure turbine stator with potential detrimental consequences on engine life and efficiency. From a numerical point of view, the mutual combustor-turbine interaction has been studied by using standard turbulence modeling approaches, as commonly employed during the design phase, even if more advanced scale-resolving methods have been proven more reliable and benchmarked against various experimental findings. From the experimental perspective, film-cooling adiabatic effectiveness and heat transfer coefficient (HTC) measurements on the external surface of the nozzle guide vanes, in the presence of representative combustor outflow characteristics, are not common since the relevant temperature distortions that are present make such kind of measurements really challenging to perform. For this reason, very limited assessment of such approaches regarding this aspect is available in literature. In this study, an experimental test case with a combustor simulator and a nozzle cascade, where both adiabatic effectiveness and HTC measurements have been carried out, is investigated by carrying out a systematic computational study, through RANS calculations of the combustor-cascade integrated domain. The film cooling system performance has been predicted by meshing the whole vane internal cooling system, while the heat transfer coefficient is calculated using the conventional two-point method, normally adopted for heat transfer calculations in gas turbines. The comparison between numerical predictions and experimental results was exploited to assess the capability of traditional modeling approaches in the characterization of both adiabatic effectiveness and heat transfer coefficient. This evaluation represents an effective means to assess if conventional/industrial approaches can be reliably used, when representative and highly unsteady combustor outflows are considered, or advanced and more time-consuming methods shall be adopted.

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“…As a matter of fact, several studies have shown that the vortical structures that characterize the combustor flow field are able to maintain a non-negligible part of its characteristics even at a relevant distance from the regions of the combustor where they are generated, in correspondence to the swirler. In particular, at the exit of the combustor, a highly non-uniform velocity distribution can be observed, characterized by high swirl and pitch components, along with temperature non-uniformities ("hot streaks") [1] and high turbulence levels [2][3][4] that can be conserved up to the inlet of the following component, the first-stage nozzle of the high-pressure turbine (HPT), as proven both experimentally and numerically [5][6][7][8]. Such severe conditions are particularly exacerbated due to the employment of modern gas turbine (GT) combustors, such as lean-burning systems [9].…”

Section: Introductionmentioning

confidence: 99%

“…For example, in the context of the project FACTOR (full aerothermal combustor-turbine interactions research), SAS simulations have been performed in order to study the aerothermal field on the vanes that were equipped on a non-reacting test rig of a lean-burn annular combustor. As a matter of fact, benchmarking the CFD predictions to the available experimental results obtained by Bacci et al [20,35], Andreini et al [2] demonstrated that SAS simulations describe the recirculating area inside the combustor better than RANS, thus improving the prediction of the turbulent mixing between the hot main flow coming from the combustor and the cooling flows [3]. An alternative to SAS and DES is represented by the stressblended eddy simulation (SBES) model, that has become increasingly popular in recent years since it allows modeling of the boundary layers regions using RANS instead of using the more expensive LES, in terms of computational resources required [36].…”

Section: Introductionmentioning

confidence: 99%

Study of Combustor–Turbine Interactions by Performing Coupled and Decoupled Hybrid RANS-LES Simulations under Representative Engine-like Conditions

Tomasello¹,

Meloni²,

Andrei³

et al. 2023

Energies

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Combustion–turbine interaction phenomena are attracting ever-growing interest in recent years. As a matter of fact, the strong unsteady and three-dimensional flow field that characterizes the combustor is usually conserved up to the first-stage nozzle, possibly affecting its design and performance in terms of aerodynamics and the effectiveness of the cooling system as well. Such conditions are also exacerbated by the employment of lean-burn combustors, where high turbulence levels are required for the flame stabilization, resulting in even greater temperature and velocity distortions at the inlet of the first-stage nozzle. Even if it has been proven by several past studies that the best way of studying the combustor–turbine interaction is simulating the two components together, performing coupled simulations is still challenging from a numerical point of view, especially in an industrial context. For this reason, the application and generation of the most representative and reliable boundary conditions possible at the inlet of the S1N have assumed an increased importance in order to study the two components separately by performing decoupled simulations. In this context, the purpose of the present work is to compare fully integrated combustor–stator SBES simulations to isolated stator ones. To perform the stator-only calculations, the fully unsteady inlet conditions of the stator have been recorded at the interface plane between the two components in the integrated SBES simulation and then they have been reconstructed by applying the proper orthogonal decomposition (POD) technique. The SBES simulations of the isolated stator have been so performed with the aim of determining whether the flow field obtained is comparable with the one of the integrated simulation, thus allowing more realistic results to be obtained rather than imposing time-averaged 2D maps, as per standard design practice.

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External heat transfer on nozzle guide vanes under highly swirled combustor outlet flow

Cited by 4 publications

References 14 publications

Numerical Study of Combustor-Turbine Interaction by Using Hybrid RANS-LES Approach

Numerical Study of Combustor-Turbine Interaction by Using Hybrid RANS-LES Approach

Numerical Prediction of Heat Transfer Coefficient and Adiabatic Effectiveness on a Nozzle Guide Vane With Representative Combustor Outflow

Study of Combustor–Turbine Interactions by Performing Coupled and Decoupled Hybrid RANS-LES Simulations under Representative Engine-like Conditions

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