Time-Resolved Flow Field Analysis of Effusion Cooling System With Representative Swirling Main Flow

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
T. Lenzi ◽  
L. Palanti ◽  
A. Picchi ◽  
T. Bacci ◽  
L. Mazzei ◽  
...  
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Life Time ◽  
Open Loop ◽  
Main Flow ◽  
Field Analysis ◽  
Ansys Fluent ◽  
Time Resolved ◽  
Film Development

Abstract Film-cooling jets behavior in a combustor chamber is deeply affected by swirling flow interactions and unsteadiness; on the other hand, the jets behavior has a direct impact on different phenomena such as cooling capabilities and ignition. For these reasons, an in-depth characterization of the film-cooling flows in the presence of a swirling main flow and demands dedicated time-resolved analyses. The experimental setup consists of a nonreactive single-sector linear combustor simulator installed in an open-loop wind tunnel. It is equipped with a swirler and a multiperforated plate to simulate the effusion cooling system of the liner. The rig is scaled with respect to the engine configuration to increase spatial resolution and to reduce the characteristic frequencies of the unsteady phenomena. Time-resolved particle image velocimetry (TRPIV) was exploited for the investigation testing different values of liner pressure drop. In addition, numerical investigations were carried out to gain a deeper insight of the behavior highlighted by the experiments and to assess the capability of computational fluid dynamics (CFD) in predicting the flow physics. In this work, the stress-blended eddy simulation (SBES) approach implemented in ansys fluent was adopted. Oscillations of the jets and intermittent interactions of the mainstream with the wall of the liner and hence with the film development have been investigated in detail. The results demonstrate how an unsteady analysis of the flow structures that characterize the jets, the turbulent mixing of coolant flows, and the interaction between mainstream and cooling jets is strictly necessary to have a complete knowledge of the behavior of the coolant, which in turn affects combustor operability and life time.

Time-Resolved Flow Field Analysis of Effusion Cooling System With Representative Swirling Main Flow

2019 ◽  
Author(s):  
T. Lenzi ◽  
L. Palanti ◽  
A. Picchi ◽  
T. Bacci ◽  
L. Mazzei ◽  
...  
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Life Time ◽  
Open Loop ◽  
Field Analysis ◽  
Ansys Fluent ◽  
Time Resolved ◽  
Eddy Simulation ◽  
Film Development

Abstract Film cooling jets behaviour in a combustor chamber is deeply affected by swirling flow interactions and unsteadiness; on the other hand, the jets behaviour has a direct impact on different phenomena such as cooling capabilities and ignition. For these reasons, an in-depth characterization of the film-cooling flows in the presence of a swirling mainflow, demands dedicated time-resolved analyses. The experimental setup consists of a non-reactive single-sector linear combustor simulator installed in an open loop wind tunnel. It is equipped with a swirler and a multiperforated plate to simulate the effusion cooling system of the liner. The rig is scaled with respect to the engine configuration, to increase spatial resolution and to reduce the characteristic frequencies of the unsteady phenomena. Time-Resolved Particle Image Velocimetry (TRPIV) was exploited for the investigation testing different values of liner pressure drop. In addition, numerical investigations were carried out to gain a deeper insight of the behaviour highlighted by the experiments and to assess the capability of CFD in predicting the flow physics. In this work, the Stress-Blended Eddy Simulation (SBES) approach implemented in ANSYS Fluent was adopted. Oscillations of the jets and intermittent interactions of the mainstream with the wall of the liner and hence with the film development have been investigated in detail. The results demonstrate how an unsteady analysis of the flow structures that characterize the jets, the turbulent mixing of coolant flows and the interaction between mainstream and cooling jets is strictly necessary to have a complete knowledge of the behaviour of the coolant which in turn affects combustor operability and life-time.

scholarly journals Unsteady Flow Field Characterization of Effusion Cooling Systems with Swirling Main Flow: Comparison Between Cylindrical and Shaped Holes

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4993
Author(s):  
Tommaso Lenzi ◽  
Alessio Picchi ◽  
Tommaso Bacci ◽  
Antonio Andreini ◽  
Bruno Facchini
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Gas Turbines ◽  
Swirling Flow ◽  
Cooling System ◽  
Complete Characterization ◽  
Time Resolved ◽  
Staggered Arrangement ◽  
Unsteady Characteristics

The presence of injectors with strongly swirled flows, used to promote flame stability in the combustion chambers of gas turbines, influences the behaviour of the effusion cooling jets and consequently of the liner’s cooling capabilities. For this reason, unsteady behaviour of the jets in the presence of swirling flow requires a characterization by means of experimental flow field analyses. The experimental setup of this work consists of a non-reactive single-sector linear combustor test rig, scaled up with respect to the real engine geometry to increase spatial resolution and to reduce the frequencies of the unsteadiness. It is equipped with a radial swirler and multi-perforated effusion plates to simulate the liner cooling system. Two effusion plates were tested and compared: with cylindrical and with laid-back fan-shaped 7-7-7 holes in staggered arrangement. Time resolved Particle Image Velocimetry has been carried out: the unsteady characteristics of the jets, promoted by the intermittent interactions with the turbulent mainstream, have been investigated as their vortex structures and turbulent decay. The results demonstrate how an unsteady analysis is necessary to provide a complete characterization of the coolant behaviour and of its turbulent mixing with mainflow, which affect, in turn, the film cooling capability and liner’s lifetime.

Numerical simulation of swirling flow effect on the first stage vane film cooling distribution

2016 ◽  
Vol 07 (03) ◽  
pp. 1650031
Author(s):  
Hong Yin
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Leading Edge ◽  
Suction Side ◽  
Local Area ◽  
Swirl Flow ◽  
Flow Effect ◽  
Recirculation Flow

In advanced gas turbine technology, lean premixed combustion is an effective strategy to reduce peak temperature and thus, NO[Formula: see text] emissions. The swirler is adopted to establish recirculation flow zone, enhancing mixing and stabilizing the flame. Therefore, the swirling flow is dominant in the combustor flow field and has impact on the vane. This paper mainly investigates the swirling flow effect on the turbine first stage vane cooling system by conducting a group of numerical simulations. Firstly, the numerical methods of turbulence modeling using RANS and LES are compared. The computational model of one single swirl flow field is considered. Both the RANS and LES results give reasonable recirculation zone shape. When comparing the velocity distribution, the RANS results generally match the experimental data but fail to at some local area. The LES modeling gives better results and more detailed unsteady flow field. In the second step, the RANS modeling is incorporated to investigate the vane film cooling performance under the swirling inflow boundary condition. According to the numerical results, the leading edge film cooling is largely altered by the swirling flow, especially for the swirl core-leading edge aligned case. Compared to the pressure side, the suction side film cooling is more sensitive to the swirling flow. Locally, the film cooling jet is lifted and turned by the strong swirling flow.

Analysis of Swirl number effects on effusion flow behaviour using time resolved PIV

2022 ◽  
pp. 1-33
Author(s):  
Tommaso Lenzi ◽  
Alessio Picchi ◽  
Antonio Andreini ◽  
Bruno Facchini
Keyword(s):  
Film Cooling ◽  
Cooling System ◽  
Tangential Velocity ◽  
Particle Image Velocimetry System ◽  
Swirl Number ◽  
Time Resolved ◽  
Experimental Apparatus ◽  
Turbulence Length ◽  
The Impact ◽  
Near Wall

Abstract The analysis of the interaction between the swirling and liner film-cooling flows is a fundamental task for the design of turbine combustion chambers since it influences different aspects such as emissions and cooling capability. Particularly, high turbulence values, flow instabilities, and tangential velocity components induced by the swirlers deeply affect the behavior of effusion cooling jets, demanding for dedicated time-resolved near-wall analysis. The experimental setup of this work consists of a non-reactive single-sector linear combustor test rig scaled up with respect to engine dimensions; the test section was equipped with an effusion plate with standard inclined cylindrical holes to simulate the liner cooling system. The rig was instrumented with a 2D Time-Resolved Particle Image Velocimetry system, focused on different field of views. The degree of swirl is usually characterized by the swirl number, Sn, defined as the ratio of the tangential momentum to axial momentum flux. To assess the impact of such parameter on the near-wall effusion behavior, a set of three axial swirlers with swirl number equal to Sn = 0.6 − 0.8 − 1.0 were designed and tested in the experimental apparatus. An analysis of the main flow by varying the Sn was first performed in terms of average velocity, RMS, and Tu values, providing kinetic energy spectra and turbulence length scale information. Following, the analysis was focused on the near-wall regions: the effects of Sn on the coolant jets was quantified in terms of vorticity analysis and jet oscillation.

Analysis of Swirl Number Effects on Effusion Flow Behaviour Using Time Resolved PIV

2021 ◽  
Author(s):  
T. Lenzi ◽  
A. Picchi ◽  
A. Andreini ◽  
B. Facchini
Keyword(s):  
Momentum Flux ◽  
Swirling Flow ◽  
Cooling System ◽  
Tangential Velocity ◽  
Particle Image Velocimetry System ◽  
Swirl Number ◽  
Time Resolved ◽  
Experimental Apparatus ◽  
The Impact ◽  
Near Wall

Abstract The analysis of the interaction between the swirling and cooling flows, promoted by the liner film cooling system, is a fundamental task for the design of turbine combustion chambers since it influences different aspects such as emissions and cooling capability. In particular high turbulence values, flow instabilities, and tangential velocity components induced by the swirling flow deeply affect the behavior of effusion cooling jets, demanding for dedicated time-resolved near-wall experimental analysis. The experimental set up of this work consists of a non-reactive single-sector linear combustor test rig scaled up with respect to engine dimensions; the test section was equipped with an effusion plate with standard inclined cylindrical holes to simulate the liner cooling system. The rig was instrumented with a 2D Time-Resolved Particle Image Velocimetry system, focused on different field of views. The degree of swirl for a swirling flow is usually characterized by the swirl number, Sn, defined as the ratio of the tangential momentum flux to axial momentum flux. To assess the impact of such parameter on the near-wall effusion behavior, a set of three different axial swirlers with swirl number equal to Sn = 0.6 - 0.8 - 1.0 were designed and tested in the experimental apparatus. An analysis of the main flow field by varying the Sn was first performed in terms of average velocity, RMS, and Tu values, providing kinetic energy spectra and turbulence length scale information. In a second step, the analysis was focused on the near-wall regions: the strong effects of Sn on the coolant jets was quantified in terms of vorticity analysis and jet oscillation.

Combination Effects of Upstream-Ramp and Swirling Coolant Flow on Film Cooling Characteristics

2015 ◽  
Author(s):  
Wenshuo Yang ◽  
Jian Pu ◽  
Jianhua Wang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Measurement Techniques ◽  
Large Angle ◽  
Vortex Pair ◽  
Structure Design ◽  
Coolant Flow ◽  
Impingement Angle ◽  
Interesting Phenomenon ◽  
Time Resolved

This paper presents an experimental investigation on the performances of a new film cooling structure design, in which a ramp is placed upstream of cylindrical film hole and a cylindrical cavity with two diagonal impingement holes is set at the inlet of the film hole to generate a swirling coolant flow entering the film hole. The experiments are carried out by two undisturbed measurement techniques, Planar Laser Induced Fluorescence (PLIF) and Time-Resolved Particle Image Velocimetry (TRPIV) in a water tunnel. The effects of the upstream-ramp angle, blowing ratio (BR) and coolant impingement angle on the film cooling performances of a flat plate are studied at three ramp angles (0°, 15° and 25°), two coolant swirling directions (clockwise and counter-clockwise), two impingement angles (15° and 30°), and three BRs (0.6, 1.0, and 1.4). The experimental results show that at high BRs, the combination structures of the upstream-ramp with the swirling coolant flow generated by the impingement angles can significantly improve film cooling performances; the best combination is at 30° impingement angle and 25° ramp angle. The reason can be explained by the fact that the swirling flow is significantly pressed onto wall through the upstream-ramp. Using the analogous analysis of heat and mass transfer, the adiabatic film effectiveness averaged over a cross section is obtained, and the analysis indicates that at high BRs, the combined effect of the a ramp with a large angle of 25° with 30° impingement angle can increase the film effectiveness up to 30% in comparison with the case without ramp at the exit of the film hole. The images captured by PLIF exhibit an interesting phenomenon, i.e. the swirling coolant in different directions can influence the counter vortex pair (CVP) in rotating layer, and the coolant swirling direction in clockwise enhances the right mixing of the CVP with coolant ejection, whereas the coolant swirling direction in counter-clockwise enhances the left mixing of the CVP with coolant ejection.

A New Test Facility for Investigating Thermal Behaviour of Effusion Cooling Test Plates for RQL Combustors

2020 ◽  
Author(s):  
A. Picchi ◽  
A. Andreini ◽  
R. Becchi ◽  
B. Facchini
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Mixture Fraction ◽  
Median Plane ◽  
Test Facility ◽  
Cooling Systems ◽  
Ir Camera ◽  
Cooling Flows ◽  
Effectiveness Data

Abstract In aero engines the combustors are subjected to critical thermal conditions in terms of high temperatures and corrosive environment, which could affect the service life of the entire system. As well known, Thermal Barrier Coatings (TBC) and above all cooling systems represents the state-of-the-art in the nowadays protecting methods: the maximization of this beneficial effect is achieved by defining an optimal cooling arrangement and developing suitable manufacturing technologies for these systems. In modern aero-engine combustors, one of the most effective cooling scheme for liners is composed by an effusion perforation coupled with a slot system to start the film cooling. The cooling performances are deeply influenced by the mutual interactions between swirling and cooling flows. In addition, for typical Rich-Quench-Lean (RQL) combustor architectures, the injection of air provided to promoting the local break-down of the flame mixture fraction, deeply interacts with the swirled flow, generating recirculating structures capable of affecting the development of film cooling and making the design of cooling systems very challenging. A new test facility for testing effusion test plates for RQL combustors applications has been developed with the final aim of comparing different cooling strategies and at the same time to collect data for numerical model validation. The experimental set-up consists of a non-reactive planar sector rigs with 5 engine-scale swirlers fed with air up to 250 °C and 3 bar. The rig was equipped with outer/inner dilution ports, and a simple inner liner cooling scheme composed of effusion and a slot system: all these features, fed with air at ambient temperature, can be independently controlled in terms of mass flow. Using dedicated optical accesses, InfraRed (IR) camera tests were performed to retrieve overall effectiveness data imposing a temperature difference between swirling and cooling flows. To better understand those results, Pressure Sensitive Paint (PSP) technique was used to obtain reliable film effectiveness data decoupling the contribution of slot and effusion flows. The thermal characterization was supported by Particle Image Velocimetry (PIV) investigations on the median plane. Tests were performed at different pressure drops across swirler and varying the mass flows of slot and inner/outer liners. The analysis of the data highlighted the influences of the swirling flow on the overall thermal performance and the behaviour of the film cooling system.

Impact of Swirl Flow on Combustor Liner Heat Transfer and Cooling: A Numerical Investigation With Hybrid RANS-LES Models

2015 ◽  
Author(s):  
L. Mazzei ◽  
A. Andreini ◽  
B. Facchini ◽  
F. Turrini
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Numerical Investigation ◽  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Swirl Flow ◽  
Opening Angle ◽  
Lean Burn ◽  
Combustor Liner

This paper reports the main findings of a numerical investigation aimed at characterizing the flow field and the wall heat transfer resulting from the interaction of a swirling flow provided by lean burn injectors and a slot cooling system, which generates film cooling in the first part of the combustor liner. In order to overcome some well-known limitations of RANS approach, e.g. the underestimation of mixing, the simulations were performed with hybrid RANS-LES models, namely SAS-SST and DES-SST, which are proving to be a viable approach to resolve the main structures of the flow field. The numerical results were compared to experimental data obtained on a non-reactive three sector planar rig developed in the context of the EU project LEMCOTEC. The analysis of the flow field has highlighted a generally good agreement against PIV measurements, especially for the SAS-SST model, whereas DES-SST returns some discrepancies in the opening angle of the swirling flow, altering the location of the corner vortex. Also the assessment in terms of Nu/Nu0 distribution confirms the overall accuracy of SAS-SST, where a constant over-prediction in the magnitude of the heat transfer is shown by DES-SST, even though potential improvements with mesh refinement are pointed out.

Adiabatic Effectiveness on High Pressure Turbine Nozzle Guide Vanes Under Realistic Swirling Conditions

2018 ◽  
Author(s):  
T. Bacci ◽  
R. Becchi ◽  
A. Picchi ◽  
B. Facchini
Keyword(s):  
High Pressure ◽  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Flame Stabilization ◽  
Lean Burn ◽  
Relevant Effect

In modern lean burn aero-engine combustors, highly swirling flow structures are adopted to control the fuel-air mixing and to provide the correct flame stabilization mechanisms. Aggressive swirl fields and high turbulence intensities are hence expected in the combustor-turbine interface. Moreover, to maximize the engine cycle efficiency, an accurate design of the high pressure nozzle cooling system must be pursued: in a film cooled nozzle the air taken from last compressor stages is ejected through discrete holes drilled on vane surfaces to provide a cold layer between hot gases and turbine components. In this context, the interactions between the swirling combustor outflow and the vane film cooling flows play a major role in the definition of a well performing cooling scheme, demanding for experimental campaigns at representative flow conditions. An annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central airfoil aligned with the central swirler. In this experimental work, adiabatic film effectiveness measurements have been carried out in the central sector vanes, in order to characterize the film-cooling performance under swirling inflow conditions. The Pressure Sensitive Paint technique, based on heat and mass transfer analogy, has been exploited to catch highly detailed 2D distributions. Carbon dioxide has been used as coolant in order to reach a coolant-to-mainstream density ratio of 1.5. Turbulence and five hole probe measurements at inlet/outlet of the cascade have been carried out as well, in order to highlight the characteristics of the flow field passing through the cascade and to provide precise boundary conditions. Results have shown a relevant effect of the swirling mainflow on the film cooling behaviour. Differences have been found between the central airfoil and the adjacent ones, both in terms of leading edge stagnation point position and of pressure and suction side film coverage characteristics.

Application of Film Cooling to an Unshrouded High-Pressure Turbine Casing

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Matthew Collins ◽  
Kamaljit Chana ◽  
Thomas Povey
Keyword(s):  
High Pressure ◽  
Film Cooling ◽  
Cooling System ◽  
Experimental Testing ◽  
Adiabatic Wall ◽  
Time Resolved ◽  
Film Cooling Effectiveness ◽  
Leakage Flows ◽  
And Performance ◽  
Tip Leakage Flows

In this paper, we describe the design, modeling, and experimental testing of a film cooling scheme employed on an unshrouded high-pressure (HP) rotor casing. The casing region has high thermal loads at both low and high frequency, with the flow being dominated by the potential field of the rotor and over-tip leakage flows. Increasingly high turbine entry temperatures necessitate internal and film cooling of the casing to ensure satisfactory service life and performance. There are, however, very few published studies presenting computational fluid dynamics (CFD) and experimental data for cooled rotor casings. Experimental testing was performed on a film-cooled rotor casing in the Oxford Turbine Research Facility (OTRF)—a rotating transonic facility of engine scale. Unsteady CFD of an HP rotor blade row with a film-cooled casing was undertaken, uniquely with a domain utilizing a sliding interface in the tip gap. A high density array of thin film heat flux gauges (TFHFGs) was used to obtain time-resolved and time-mean results of adiabatic wall temperature and film cooling effectiveness on the film-cooled rotor casing between −30% and +125% rotor tip axial chord. Results are compared to CFD predictions, and mechanisms for interaction of the coolant with the rotor tip are proposed and discussed. Acoustic effects within casing coolant holes due to the passing of the rotor are demonstrated on a 3D CFD geometry, supporting conclusions drawn in earlier work by the authors on the importance of this effect in a casing film cooling system.

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