Bruno Facchini | Università degli Studi di Firenze (University of Florence) (original) (raw)

Papers by Bruno Facchini

Volume 3: Turbo Expo 2003, 2003

ABSTRACT

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2012

ABSTRACT In new generation aero-engines based on the innovative lean combustion technology, therm... more ABSTRACT In new generation aero-engines based on the innovative lean combustion technology, thermoacoustic instabilities are one of the most important issues and their prevention and reduction are challenging goals. To achieve these targets, the use of multi-perforated liners, that have to primarily provide an efficient liner cooling, is very attractive because they are efficient passive dampers of pressure fluctuations, especially with bias flow. The design of multi-perforated liners for both thermal and acoustic purposes can be accomplished by selecting liner parameters, such as hole diameter, pattern and inclination, main and bias Mach numbers, fulfilling both requirements; this procedure requires to assess the effect of both geometrical and fluid-dynamic features. Thus, a specific research project is ongoing on the acoustic and thermal experimental characterization of selected multi-perforated liner geometries. In this paper, the complete experimental campaign on the acoustic behavior of the aforementioned liners has been carried out in the planar wave field range, that is of main concern in aero-engines. For this purpose, an innovative modular test rig has been designed to characterize test cases at ambient conditions, changing bias and main flows up to operating engine conditions. Liner geometries account for 3 different hole diameters, 5 different patterns and 2 hole inclinations, ranging within typical cooling system values; tests were performed with the two-source multi-microphone technique to evaluate global acoustic parameters independently from test rig boundary conditions. The acoustic performances of liners are discussed in terms of the energy dissipation coefficient.

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011

ABSTRACT Multi-perforated liners, commonly employed in Gas Turbine combustors as cooling devices ... more ABSTRACT Multi-perforated liners, commonly employed in Gas Turbine combustors as cooling devices to control metal temperature, are recognized as very effective sound absorbers. Thus, in the innovative lean combustion technology, where the onset of thermoacoustic instabilities represents one of the most important issue, the multi-perforated plates can be exploited both for wall cooling and damping combustion instabilities. As a first step of a large experimental and numerical research program regarding multi-perforated liners, an investigation of different numerical methodologies to analyze acoustic damping is here reported. In particular three different numerical techniques to evaluate planar waves sound absorption of perforated plates are presented and validated with literature test cases. A quasi 1-D code, implementing the wall compliance concept, provides results for a large set of geometric and fluidynamic conditions. A large test matrix was investigated varying perforation hole angle and diameter with different overall porosities. The effect of bias and grazing flows Mach number was tested as well. A subset of considered geometries were then supported by a full reconstruction of the unsteady pressure field by means of a Large Eddy Simulation computed with an open-source code. Non-reflective boundaries with forcing term provide the wave to acoustically excite the perforated plate. Multi-microphone postprocessing technique allowed the reconstruction of a progressive and regressive planar wave to compute the reflection coefficient. All results were cross-checked with a Finite Element Model, able to solve the wave equation in the frequency domain with a background velocity field.

Energy Conversion and Management, Oct 1, 1997

An innovative gas turbine cycle is studied, which can offer several advantages from the point of ... more An innovative gas turbine cycle is studied, which can offer several advantages from the point of view of environmental friendship and peakload shaving capabilities. The basic idea of SCGT/CC is of cooling down the exhaust to temperatures as low as to allow full condensation of the water vapor; a large part of the exhaust gases is then recirculated to the compressor; the condensed water can be reinjected by means of a pump at compressor delivery. For maximum performance it is convenient not to inject this water flow, but rather to use it for other purposes; however, water injection produces a power boosting effect (at the expense of a small decrease in efficiency) which can be useful for peakload shaving applications. The working gas composition in the GT cycle is that corresponding to stoichiometric combustion, which opens the possibility of applying techniques for CO2 recycling and general exhaust gas treatment. The cycle guarantees a high level of efficiency, and its adoption should imply minor modifications to existing equipment.

... Thermoeconomic evaluation of cycle performance and of the water recovery process. Andrea Cort... more ... Thermoeconomic evaluation of cycle performance and of the water recovery process. Andrea Corti, Bruno Facchini, Giampaolo Manfrida, Umberto Desideri The 1998 International Gas Turbine & Aeroengine Congress & Exhibition, 1998. ...

Volume 5C: Heat Transfer, 2015

Volume 5C: Heat Transfer, 2015

ABSTRACT Over the last ten years there have been significant technological advances toward the re... more ABSTRACT Over the last ten years there have been significant technological advances toward the reduction of NOx emissions from civil aircraft engines, strongly aimed at meeting stricter and stricter legislation requirements. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern combustors is represented by lean burn swirl stabilized technology. The high amount of air admitted through a lean-burn injection system is characterized by very complex flow structures such as recirculations, vortex breakdown and precessing vortex core, that may deeply interact in the near wall region of the combustor liner. This interaction makes challenging the estimation of film cooling distribution, commonly generated by slot and effusion systems. The main purpose of the present work is the characterization of the flow field and the adiabatic effectiveness due to the interaction of swirling flow, generated by real geometry injectors, and a liner cooling scheme made up of a slot injection and an effusion array. The experimental apparatus has been developed within EU project LEMCOTEC and consists of a non-reactive three sectors planar rig; the test model is characterized by a complete cooling system and three swirlers, replicating the geometry of a GE Avio PERM (Partially Evaporated and Rapid Mixing) injector technology. The effusion geometry is composed by a staggered array of 1236 circular holes with an inclination of 30 degree, while the slot exit has a constant height of 5 mm. Tests have been carried out imposing realistic combustor operating conditions, especially in terms of pressure drop across the swirlers and effusion plate. Flow field measurements have been performed by means of a standard 2D PIV (Particle Image Velocimetry) technique, while adiabatic effectiveness maps have been obtained using PSP (Pressure Sensitive Paint) technique. PIV results show the effect of coolant injection in the corner vortex region, while the PSP measurements highlight the impact of swirled flow on the liner film protection separating the contribution of slot and effusion flows. Furthermore an additional analysis, exploiting experimental results in terms of heat transfer coefficient, has been performed to estimate the net heat flux reduction (NHFR) on the cooled test plate.

Volume 5C: Heat Transfer, 2015

ABSTRACT Turbine entry conditions are characterized by unsteady and strongly non-uniform velocity... more ABSTRACT Turbine entry conditions are characterized by unsteady and strongly non-uniform velocity and temperature and pressure fields. The uncertainty and the lack of confidence associated to these conditions require the application of wide safety margins during the design of the turbine cooling systems, which are detrimental for the efficiency of the engine. These issues have been further complicated by the adoption of lean-burn technology in modern aeroengines, identified by many manufacturers as the most promising solution for a significant reduction of NOx emission. Such devices are in fact characterized by a very compact design, whereas the strong swirl component generated by the injector is maintained up to the end of the flametube due to the absence of dilution holes, which in conventional combustors provides the required pattern factor. Bearing in mind complexity and costs associated to the experimental investigation of combustor-turbine interaction, CFD has become a key and complementary tool to understand the physical phenomena involved. Due to the well-known limitations of the RANS approach and the increase in computational resources, hybrid RANS-LES models, such as Scale Adaptive Simulation (SAS), are proving to be a viable approach to resolve the main structures of the flow field. This paper reports the main findings of the numerical investigation of a hot streak generator for the study of combustor-turbine interaction. The results were compared to experimental data obtained from a test rig representative of a lean-burn, effusion cooled, annular combustor, developed in the context of the EU project FACTOR. Steady RANS and unsteady SAS runs were carried out in order to assess the improvements related to hybrid models. Additional simulations were performed to investigate the effect of the periodicity assumption and the impact of liner cooling modelling on the exit conditions.

AbstractÐCurrent research programmes such as the CAGT programme investigate the opportunity for a... more AbstractÐCurrent research programmes such as the CAGT programme investigate the opportunity for advanced power generation cycles based on state-of-the-art aeroderivative gas turbine technology. Such cycles would be primarily aimed at intermediate duty applications. Compared to industrial gas turbines, aeroderivatives oer high simple cycle eciency, and the capability to start quickly and frequently without a signi®cant maintenance cost penalty. A key element for high system performance is the development of improved heat recovery systems, leading to advanced cycles such as the humid air turbine (HAT) cycle, the chemically recuperated gas turbine (CRGT) cycle and the Kalina combined cycle. When used in combination with advanced technologies and components, screening studies conducted by research programmes such as the CAGT programme predict that such advanced cycles could theoretically lead to net cycle eciencies exceeding 60%. In this paper, the authors present the application of the modular approach to cycle simulation and performance predictions of CRGT cycles. The paper ®rst presents the modular simulation code concept and the main characteristics of CRGT cycles. The paper next discusses the development of the methane±steam reformer unit model used for the simulations. The modular code is then used to compute performance characteristics of a simple CRGT cycle and a reheat CRGT cycle, both based on the General Electric LM6000 aeroderivative gas turbine. # 1998 Elsevier Science Ltd. All rights reserved

Volume 3: Turbo Expo 2004, 2004

ABSTRACT

Volume 5C: Heat Transfer, 2014

ABSTRACT Many efforts have been devoted to develop methodologies based on film cooling modeling. ... more ABSTRACT Many efforts have been devoted to develop methodologies based on film cooling modeling. Among the approaches published in the literature, models based on local sources represent a good compromise between simplicity and accuracy, with the capability to automatically perform a Conjugate Heat Transfer analysis. This type of methodology has been already defined and validated by the authors, with comparison on effusion cooled plates in terms of experimental overall effectiveness measurements as well as the application on a tubular combustor test case. In the context of this work, the proposed approach has been applied to the analysis of a lean annular combustor with the purpose of investigating pressure losses, flow split and metal temperature field. The results obtained have been compared to experimental data and different numerical tools exploited during the preliminary design of these devices.

Volume 3C: Heat Transfer, 2013

ABSTRACT Effusion cooling technology has been assessed in past years as one of the most efficient... more ABSTRACT Effusion cooling technology has been assessed in past years as one of the most efficient methods to maintain allowable working temperature of combustor liners. Despite many efforts reported in literature to characterize the cooling performances of those devices, detailed analysis of the mixing process between coolant and hot gas are difficult to perform especially in case superposition and density ratio effects become important. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes which showed higher sound absorption. This paper performs a CFD analysis of the flow and thermal field associated with adiabatic wall conditions to compute the cooling effectiveness. The geometry consists of an effusion cooling plate drilled with 18 holes and fed separately with a cold and hot gas flow. Two types of perforations equivalent in porosity and pitches are investigated to assess the influence of the drilling angle between 30 and 90 deg. The reference conditions considered in this work comprehend an effective blowing ratio ranging between 1 and 3 at isothermal conditions (reaching a maximum hole Reynolds number of 10000) and high inlet turbulence intensity (17%). This set of conditions was exploited to perform a validation of the numerical procedure against detailed experimental data presented in another paper. Inlet turbulence effects highlighted by measurements for the slanted perforation were also investigated simulating a low turbulence condition corresponding to 1.6% of intensity. Furthermore the nominal DR = 1.0 was increased up to 1.7 to expand the available data set towards typical working conditions for aero-engines. Steady state RANS calculations were performed with the commercial code ANSYS® CFX, modeling turbulence by means of the k — ω SST. In order to include anisotropic diffusion effects due to turbulence damping in the near wall region, the turbulence model is corrected considering a tensorial definition of the eddy viscosity with an algebraic correction to dope its stream-span components. Computational grids were finely clustered close to the main plate and inside the holes to obtain y+ < 1, to maximize solver accuracy according to previous similar analysis.

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1998

Volume 3: Heat Transfer, Parts A and B, 2006

... the doublewall technology, that allow to enhance the internal heat exchange optimising the co... more ... the doublewall technology, that allow to enhance the internal heat exchange optimising the cooling ... of different cooling technologies are actually available and used in turbine design based ... Many improvements were studied based on this classical solutions: ribbed channel have ...

Journal of Engineering for Gas Turbines and Power, 2014

ABSTRACT Effusion cooling represents the state of the art of liner cooling technology for modern ... more ABSTRACT Effusion cooling represents the state of the art of liner cooling technology for modern combustors. This technique consists of an array of closely spaced discrete film cooling holes and contributes to lower the metal temperature by the combined protective effect of coolant film and heat removal through forced convection inside each hole. Despite many efforts reported in literature to characterize the cooling performance of these devices, detailed analyses of the mixing process between coolant and hot gas are difficult to perform, especially when superposition and density ratio effects as well as the interaction with complex gas side flow field become significant. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes, which showed higher sound absorption. The objective of this paper is to investigate the impact of a realistic flow field on the adiabatic effectiveness performance of effusion cooling liners to verify the findings available in literature, which are mostly based on effusion flat plates with aligned crossflow, in case of swirled hot gas flow. The geometry consists of a tubular combustion chamber, equipped with a double swirler injection system and characterized by twenty-two rows of cooling holes on the liner. The liner cooling system employs slot cooling as well: its interactions with the cold gas injected through the effusion plate are investigated too. Taking advantage of the rotational periodicity of the effusion geometry and assuming axisymmetric conditions at the combustor inlet, steady state RANS calculations have been performed with the commercial code ANSYS CFX simulating a single circumferential pitch. Obtained results show how the effusion perforation angle deeply affects the flow-field around the corner of the combustor, in particular with a strong reduction of slot effectiveness in case of 90[deg] angle value.

Energy Procedia, 2014

ABSTRACT Gas turbine performance improvement is strictly linked to the attainment of higher maxim... more ABSTRACT Gas turbine performance improvement is strictly linked to the attainment of higher maximum temperature, hence heat load man- agement becomes an essential activity. This paper presents a decoupled procedure aimed to predict cooling performances and metal temperatures of gas turbine blades and nozzles: needed inputs are evaluated by different tools (CFD, in-house fluid network solver, thermal FEM). The procedure is validated on two different test cases: an internally cooled vane, and an internally and film cooled vane. Metal temperature and adiabatic effectiveness distributions are compared against experimental data and results from a fully 3D coupled CHT CFD analysis.

Volume 3: Turbo Expo 2004, 2004

A 3D conjugate heat transfer simulation of a radially cooled gas turbine vane has been performed ... more A 3D conjugate heat transfer simulation of a radially cooled gas turbine vane has been performed using STAR-CD™ code and the metal temperature distribution of the blade has been obtained. The study focused on the linear NASA-C3X cascade, for which experimental ...

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 1998

Abstract A number of innovative gas turbine cycles have been proposed lately, including the humid... more Abstract A number of innovative gas turbine cycles have been proposed lately, including the humid air turbine (HAT) and the chemically recuperated gas turbine (CRGT). The potential of the CRGT cycle lies in the ability to generate power with a high efficiency and ultra-low NO ...

Journal of Turbomachinery, 2013

ABSTRACT In the course of the years several turbulence models specifically developed to improve t... more ABSTRACT In the course of the years several turbulence models specifically developed to improve the predicting capabilities of conventional two-equations RANS models have been proposed. However they have been mainly tested against experiments only comparing with standard isotropic models, in single hole configuration and for very low blowing ratio. A systematic benchmark of the various non-conventional models exploring a wider range of application is hence missing.This paper performs a comparison of 3 recently proposed models over three different test cases of increasing computational complexity. The chosen test matrix covers a wide range of blowing ratios (0.5–3.0)including both single row and multi-row cases for which experimental data of reference are available. In particular the well known test by Sinha and Bogard [1] at BR = 0.5 is used in conjuction with two in-house carried out experiments: a single row film-cooling test at BR = 1.5 and a 15 rows test plate designed to study the interaction between slot and effusion cooling at BR = 3.0.The first two considered models are based on a tensorial definition of the eddy viscosity in which the stream-span position is augmented to overcome the main drawback connected with standard isotropic turbulence models that is the lower lateral spreading of the jet downwards the injection. An anisotropic factor to multiply the off-diagonal position is indeed calculated from an algebraic expression of the turbulent Reynolds number developed by Bergeles [2] from DNS statistics over a flat plate. This correction could be potentially implemented in the framework of any eddy viscosity model. It was chosen to compare the predictions of such modification applied to two among the most common two-equation turbulence models for film-cooling tests, namely the Two-Layer (TL) model and the k–ω Shear Stress Transport (SST), firstly proposed and tested in the past respectively by Azzi and Lakeal [3] and Cottin at al. [4].The third model, proposed by Holloway et al. [5], involves the unsteady solution of the flow and thermal field to include the short-time response of the stress tensor to rapid strain rates. This model takes advantage of the solution of an additional transport equation for the local effective total stress to trace the strain rate history.The results are presented in terms of adiabatic effectiveness distribution over the plate as well as spanwise averaged profiles.

Volume 3: Turbo Expo 2003, 2003

ABSTRACT

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2012

ABSTRACT In new generation aero-engines based on the innovative lean combustion technology, therm... more ABSTRACT In new generation aero-engines based on the innovative lean combustion technology, thermoacoustic instabilities are one of the most important issues and their prevention and reduction are challenging goals. To achieve these targets, the use of multi-perforated liners, that have to primarily provide an efficient liner cooling, is very attractive because they are efficient passive dampers of pressure fluctuations, especially with bias flow. The design of multi-perforated liners for both thermal and acoustic purposes can be accomplished by selecting liner parameters, such as hole diameter, pattern and inclination, main and bias Mach numbers, fulfilling both requirements; this procedure requires to assess the effect of both geometrical and fluid-dynamic features. Thus, a specific research project is ongoing on the acoustic and thermal experimental characterization of selected multi-perforated liner geometries. In this paper, the complete experimental campaign on the acoustic behavior of the aforementioned liners has been carried out in the planar wave field range, that is of main concern in aero-engines. For this purpose, an innovative modular test rig has been designed to characterize test cases at ambient conditions, changing bias and main flows up to operating engine conditions. Liner geometries account for 3 different hole diameters, 5 different patterns and 2 hole inclinations, ranging within typical cooling system values; tests were performed with the two-source multi-microphone technique to evaluate global acoustic parameters independently from test rig boundary conditions. The acoustic performances of liners are discussed in terms of the energy dissipation coefficient.

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011

ABSTRACT Multi-perforated liners, commonly employed in Gas Turbine combustors as cooling devices ... more ABSTRACT Multi-perforated liners, commonly employed in Gas Turbine combustors as cooling devices to control metal temperature, are recognized as very effective sound absorbers. Thus, in the innovative lean combustion technology, where the onset of thermoacoustic instabilities represents one of the most important issue, the multi-perforated plates can be exploited both for wall cooling and damping combustion instabilities. As a first step of a large experimental and numerical research program regarding multi-perforated liners, an investigation of different numerical methodologies to analyze acoustic damping is here reported. In particular three different numerical techniques to evaluate planar waves sound absorption of perforated plates are presented and validated with literature test cases. A quasi 1-D code, implementing the wall compliance concept, provides results for a large set of geometric and fluidynamic conditions. A large test matrix was investigated varying perforation hole angle and diameter with different overall porosities. The effect of bias and grazing flows Mach number was tested as well. A subset of considered geometries were then supported by a full reconstruction of the unsteady pressure field by means of a Large Eddy Simulation computed with an open-source code. Non-reflective boundaries with forcing term provide the wave to acoustically excite the perforated plate. Multi-microphone postprocessing technique allowed the reconstruction of a progressive and regressive planar wave to compute the reflection coefficient. All results were cross-checked with a Finite Element Model, able to solve the wave equation in the frequency domain with a background velocity field.

Energy Conversion and Management, Oct 1, 1997

An innovative gas turbine cycle is studied, which can offer several advantages from the point of ... more An innovative gas turbine cycle is studied, which can offer several advantages from the point of view of environmental friendship and peakload shaving capabilities. The basic idea of SCGT/CC is of cooling down the exhaust to temperatures as low as to allow full condensation of the water vapor; a large part of the exhaust gases is then recirculated to the compressor; the condensed water can be reinjected by means of a pump at compressor delivery. For maximum performance it is convenient not to inject this water flow, but rather to use it for other purposes; however, water injection produces a power boosting effect (at the expense of a small decrease in efficiency) which can be useful for peakload shaving applications. The working gas composition in the GT cycle is that corresponding to stoichiometric combustion, which opens the possibility of applying techniques for CO2 recycling and general exhaust gas treatment. The cycle guarantees a high level of efficiency, and its adoption should imply minor modifications to existing equipment.

... Thermoeconomic evaluation of cycle performance and of the water recovery process. Andrea Cort... more ... Thermoeconomic evaluation of cycle performance and of the water recovery process. Andrea Corti, Bruno Facchini, Giampaolo Manfrida, Umberto Desideri The 1998 International Gas Turbine & Aeroengine Congress & Exhibition, 1998. ...

Volume 5C: Heat Transfer, 2015

Volume 5C: Heat Transfer, 2015

ABSTRACT Over the last ten years there have been significant technological advances toward the re... more ABSTRACT Over the last ten years there have been significant technological advances toward the reduction of NOx emissions from civil aircraft engines, strongly aimed at meeting stricter and stricter legislation requirements. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern combustors is represented by lean burn swirl stabilized technology. The high amount of air admitted through a lean-burn injection system is characterized by very complex flow structures such as recirculations, vortex breakdown and precessing vortex core, that may deeply interact in the near wall region of the combustor liner. This interaction makes challenging the estimation of film cooling distribution, commonly generated by slot and effusion systems. The main purpose of the present work is the characterization of the flow field and the adiabatic effectiveness due to the interaction of swirling flow, generated by real geometry injectors, and a liner cooling scheme made up of a slot injection and an effusion array. The experimental apparatus has been developed within EU project LEMCOTEC and consists of a non-reactive three sectors planar rig; the test model is characterized by a complete cooling system and three swirlers, replicating the geometry of a GE Avio PERM (Partially Evaporated and Rapid Mixing) injector technology. The effusion geometry is composed by a staggered array of 1236 circular holes with an inclination of 30 degree, while the slot exit has a constant height of 5 mm. Tests have been carried out imposing realistic combustor operating conditions, especially in terms of pressure drop across the swirlers and effusion plate. Flow field measurements have been performed by means of a standard 2D PIV (Particle Image Velocimetry) technique, while adiabatic effectiveness maps have been obtained using PSP (Pressure Sensitive Paint) technique. PIV results show the effect of coolant injection in the corner vortex region, while the PSP measurements highlight the impact of swirled flow on the liner film protection separating the contribution of slot and effusion flows. Furthermore an additional analysis, exploiting experimental results in terms of heat transfer coefficient, has been performed to estimate the net heat flux reduction (NHFR) on the cooled test plate.

Volume 5C: Heat Transfer, 2015

ABSTRACT Turbine entry conditions are characterized by unsteady and strongly non-uniform velocity... more ABSTRACT Turbine entry conditions are characterized by unsteady and strongly non-uniform velocity and temperature and pressure fields. The uncertainty and the lack of confidence associated to these conditions require the application of wide safety margins during the design of the turbine cooling systems, which are detrimental for the efficiency of the engine. These issues have been further complicated by the adoption of lean-burn technology in modern aeroengines, identified by many manufacturers as the most promising solution for a significant reduction of NOx emission. Such devices are in fact characterized by a very compact design, whereas the strong swirl component generated by the injector is maintained up to the end of the flametube due to the absence of dilution holes, which in conventional combustors provides the required pattern factor. Bearing in mind complexity and costs associated to the experimental investigation of combustor-turbine interaction, CFD has become a key and complementary tool to understand the physical phenomena involved. Due to the well-known limitations of the RANS approach and the increase in computational resources, hybrid RANS-LES models, such as Scale Adaptive Simulation (SAS), are proving to be a viable approach to resolve the main structures of the flow field. This paper reports the main findings of the numerical investigation of a hot streak generator for the study of combustor-turbine interaction. The results were compared to experimental data obtained from a test rig representative of a lean-burn, effusion cooled, annular combustor, developed in the context of the EU project FACTOR. Steady RANS and unsteady SAS runs were carried out in order to assess the improvements related to hybrid models. Additional simulations were performed to investigate the effect of the periodicity assumption and the impact of liner cooling modelling on the exit conditions.

AbstractÐCurrent research programmes such as the CAGT programme investigate the opportunity for a... more AbstractÐCurrent research programmes such as the CAGT programme investigate the opportunity for advanced power generation cycles based on state-of-the-art aeroderivative gas turbine technology. Such cycles would be primarily aimed at intermediate duty applications. Compared to industrial gas turbines, aeroderivatives oer high simple cycle eciency, and the capability to start quickly and frequently without a signi®cant maintenance cost penalty. A key element for high system performance is the development of improved heat recovery systems, leading to advanced cycles such as the humid air turbine (HAT) cycle, the chemically recuperated gas turbine (CRGT) cycle and the Kalina combined cycle. When used in combination with advanced technologies and components, screening studies conducted by research programmes such as the CAGT programme predict that such advanced cycles could theoretically lead to net cycle eciencies exceeding 60%. In this paper, the authors present the application of the modular approach to cycle simulation and performance predictions of CRGT cycles. The paper ®rst presents the modular simulation code concept and the main characteristics of CRGT cycles. The paper next discusses the development of the methane±steam reformer unit model used for the simulations. The modular code is then used to compute performance characteristics of a simple CRGT cycle and a reheat CRGT cycle, both based on the General Electric LM6000 aeroderivative gas turbine. # 1998 Elsevier Science Ltd. All rights reserved

Volume 3: Turbo Expo 2004, 2004

ABSTRACT

Volume 5C: Heat Transfer, 2014

ABSTRACT Many efforts have been devoted to develop methodologies based on film cooling modeling. ... more ABSTRACT Many efforts have been devoted to develop methodologies based on film cooling modeling. Among the approaches published in the literature, models based on local sources represent a good compromise between simplicity and accuracy, with the capability to automatically perform a Conjugate Heat Transfer analysis. This type of methodology has been already defined and validated by the authors, with comparison on effusion cooled plates in terms of experimental overall effectiveness measurements as well as the application on a tubular combustor test case. In the context of this work, the proposed approach has been applied to the analysis of a lean annular combustor with the purpose of investigating pressure losses, flow split and metal temperature field. The results obtained have been compared to experimental data and different numerical tools exploited during the preliminary design of these devices.

Volume 3C: Heat Transfer, 2013

ABSTRACT Effusion cooling technology has been assessed in past years as one of the most efficient... more ABSTRACT Effusion cooling technology has been assessed in past years as one of the most efficient methods to maintain allowable working temperature of combustor liners. Despite many efforts reported in literature to characterize the cooling performances of those devices, detailed analysis of the mixing process between coolant and hot gas are difficult to perform especially in case superposition and density ratio effects become important. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes which showed higher sound absorption. This paper performs a CFD analysis of the flow and thermal field associated with adiabatic wall conditions to compute the cooling effectiveness. The geometry consists of an effusion cooling plate drilled with 18 holes and fed separately with a cold and hot gas flow. Two types of perforations equivalent in porosity and pitches are investigated to assess the influence of the drilling angle between 30 and 90 deg. The reference conditions considered in this work comprehend an effective blowing ratio ranging between 1 and 3 at isothermal conditions (reaching a maximum hole Reynolds number of 10000) and high inlet turbulence intensity (17%). This set of conditions was exploited to perform a validation of the numerical procedure against detailed experimental data presented in another paper. Inlet turbulence effects highlighted by measurements for the slanted perforation were also investigated simulating a low turbulence condition corresponding to 1.6% of intensity. Furthermore the nominal DR = 1.0 was increased up to 1.7 to expand the available data set towards typical working conditions for aero-engines. Steady state RANS calculations were performed with the commercial code ANSYS® CFX, modeling turbulence by means of the k — ω SST. In order to include anisotropic diffusion effects due to turbulence damping in the near wall region, the turbulence model is corrected considering a tensorial definition of the eddy viscosity with an algebraic correction to dope its stream-span components. Computational grids were finely clustered close to the main plate and inside the holes to obtain y+ < 1, to maximize solver accuracy according to previous similar analysis.

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1998

Volume 3: Heat Transfer, Parts A and B, 2006

... the doublewall technology, that allow to enhance the internal heat exchange optimising the co... more ... the doublewall technology, that allow to enhance the internal heat exchange optimising the cooling ... of different cooling technologies are actually available and used in turbine design based ... Many improvements were studied based on this classical solutions: ribbed channel have ...

Journal of Engineering for Gas Turbines and Power, 2014

ABSTRACT Effusion cooling represents the state of the art of liner cooling technology for modern ... more ABSTRACT Effusion cooling represents the state of the art of liner cooling technology for modern combustors. This technique consists of an array of closely spaced discrete film cooling holes and contributes to lower the metal temperature by the combined protective effect of coolant film and heat removal through forced convection inside each hole. Despite many efforts reported in literature to characterize the cooling performance of these devices, detailed analyses of the mixing process between coolant and hot gas are difficult to perform, especially when superposition and density ratio effects as well as the interaction with complex gas side flow field become significant. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes, which showed higher sound absorption. The objective of this paper is to investigate the impact of a realistic flow field on the adiabatic effectiveness performance of effusion cooling liners to verify the findings available in literature, which are mostly based on effusion flat plates with aligned crossflow, in case of swirled hot gas flow. The geometry consists of a tubular combustion chamber, equipped with a double swirler injection system and characterized by twenty-two rows of cooling holes on the liner. The liner cooling system employs slot cooling as well: its interactions with the cold gas injected through the effusion plate are investigated too. Taking advantage of the rotational periodicity of the effusion geometry and assuming axisymmetric conditions at the combustor inlet, steady state RANS calculations have been performed with the commercial code ANSYS CFX simulating a single circumferential pitch. Obtained results show how the effusion perforation angle deeply affects the flow-field around the corner of the combustor, in particular with a strong reduction of slot effectiveness in case of 90[deg] angle value.

Energy Procedia, 2014

ABSTRACT Gas turbine performance improvement is strictly linked to the attainment of higher maxim... more ABSTRACT Gas turbine performance improvement is strictly linked to the attainment of higher maximum temperature, hence heat load man- agement becomes an essential activity. This paper presents a decoupled procedure aimed to predict cooling performances and metal temperatures of gas turbine blades and nozzles: needed inputs are evaluated by different tools (CFD, in-house fluid network solver, thermal FEM). The procedure is validated on two different test cases: an internally cooled vane, and an internally and film cooled vane. Metal temperature and adiabatic effectiveness distributions are compared against experimental data and results from a fully 3D coupled CHT CFD analysis.

Volume 3: Turbo Expo 2004, 2004

A 3D conjugate heat transfer simulation of a radially cooled gas turbine vane has been performed ... more A 3D conjugate heat transfer simulation of a radially cooled gas turbine vane has been performed using STAR-CD™ code and the metal temperature distribution of the blade has been obtained. The study focused on the linear NASA-C3X cascade, for which experimental ...

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 1998

Abstract A number of innovative gas turbine cycles have been proposed lately, including the humid... more Abstract A number of innovative gas turbine cycles have been proposed lately, including the humid air turbine (HAT) and the chemically recuperated gas turbine (CRGT). The potential of the CRGT cycle lies in the ability to generate power with a high efficiency and ultra-low NO ...

Journal of Turbomachinery, 2013

ABSTRACT In the course of the years several turbulence models specifically developed to improve t... more ABSTRACT In the course of the years several turbulence models specifically developed to improve the predicting capabilities of conventional two-equations RANS models have been proposed. However they have been mainly tested against experiments only comparing with standard isotropic models, in single hole configuration and for very low blowing ratio. A systematic benchmark of the various non-conventional models exploring a wider range of application is hence missing.This paper performs a comparison of 3 recently proposed models over three different test cases of increasing computational complexity. The chosen test matrix covers a wide range of blowing ratios (0.5–3.0)including both single row and multi-row cases for which experimental data of reference are available. In particular the well known test by Sinha and Bogard [1] at BR = 0.5 is used in conjuction with two in-house carried out experiments: a single row film-cooling test at BR = 1.5 and a 15 rows test plate designed to study the interaction between slot and effusion cooling at BR = 3.0.The first two considered models are based on a tensorial definition of the eddy viscosity in which the stream-span position is augmented to overcome the main drawback connected with standard isotropic turbulence models that is the lower lateral spreading of the jet downwards the injection. An anisotropic factor to multiply the off-diagonal position is indeed calculated from an algebraic expression of the turbulent Reynolds number developed by Bergeles [2] from DNS statistics over a flat plate. This correction could be potentially implemented in the framework of any eddy viscosity model. It was chosen to compare the predictions of such modification applied to two among the most common two-equation turbulence models for film-cooling tests, namely the Two-Layer (TL) model and the k–ω Shear Stress Transport (SST), firstly proposed and tested in the past respectively by Azzi and Lakeal [3] and Cottin at al. [4].The third model, proposed by Holloway et al. [5], involves the unsteady solution of the flow and thermal field to include the short-time response of the stress tensor to rapid strain rates. This model takes advantage of the solution of an additional transport equation for the local effective total stress to trace the strain rate history.The results are presented in terms of adiabatic effectiveness distribution over the plate as well as spanwise averaged profiles.