Clocking Effects of Inlet Non-Uniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis

2015 ◽  
Author(s):  
Duccio Griffini ◽  
Massimiliano Insinna ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling System ◽  
Hot Spot ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis

A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and high-pressure vanes are then investigated considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first one where hot spot and swirl core are aligned with passage and the second one where they are aligned with the leading edge. Comparisons between metal temperature distributions obtained from conjugate heat transfer simulations are performed evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The leading edge aligned configuration is resulted to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage aligned case. A strong sensitivity of both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

Clocking Effects of Inlet Nonuniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Duccio Griffini ◽  
Massimiliano Insinna ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling System ◽  
Hot Spot ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis

A high-pressure vane (HPV) equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side, while the leading edge (LE) is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-averaged Navier–Stokes simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and HPVs are then investigated, considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first in which hot spot and swirl core are aligned with passage; and the second in which they are aligned with the LE. Comparisons between metal temperature distributions obtained from conjugate heat transfer (CHT) simulations are performed, evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The LE aligned configuration is determined to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage-aligned case. A strong sensitivity to both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

Film Cooling Performances at Different Turbulence Intensities Using Conjugate Heat Transfer Analysis

2017 ◽  
Vol 872 ◽  
pp. 271-278
Author(s):  
Prasert Prapamonthon ◽  
Hua Zhao Xu ◽  
Jian Hua Wang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Large Area ◽  
Cooling Effectiveness ◽  
Flowing Fluid

This study presents a numerical investigation of cooling performances of a modified vane of the film-cooled vane reported by Timko (NASA CR-168289) at different mainstream turbulence intensities (Tus). A 3D conjugate heat transfer (CHT) analysis with SST k-ω turbulence model in FLUENT V.15 is used. Three different mechanisms in CHT analysis, i.e. fluid flow, heat convection between solid surfaces and flowing fluid in an external mainstream and internal cooling passages, and heat conduction within the vane structure, are simultaneously considered. Numerical results are conducted in terms of overall cooling effectiveness at Tu=3.3, 10, and 20%. Comparison between overall cooling effectiveness and film effectiveness under adiabatic assumption is discussed at the three Tus, also. The findings of this research indicate the following phenomena: 1) overall cooling effectiveness decreases with Tu, and this effect on the pressure side (PS) is stronger than that on the suction side (SS) in general. 2) By comparison with adiabatic film effectiveness, the level of overall cooling effectiveness in most regions is higher and more uniform than that of adiabatic film effectiveness for all three Tus. 3) In the leading edge (LE), when Tu increases, near the exits of film holes overall cooling effectiveness deteriorates, but adiabatic film effectiveness improves. Furthermore, a large area with relatively low overall cooling effectiveness is able to move with Tu in the LE region.

Conjugate Heat Transfer Analysis to Assess Overall Cooling Effectiveness of High Pressure Turbine Nozzle With Optimized Film Cooling Hole Arrangements

2019 ◽  
Author(s):  
Young Seok Kang ◽  
Dong-Ho Rhee ◽  
Sanga Lee ◽  
Bong Jun Cha
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Baseline Design ◽  
Pressure Surface

Abstract Conjugate heat transfer analysis method has been highlighted for predicting heat exchange between fluid domain and solid domain inside high-pressure turbines, which are exposed to very harsh operating conditions. Then it is able to assess the overall cooling effectiveness considering both internal cooling and external film cooling at the cooled turbine design step. In this study, high-pressure turbine nozzles, which have three different film cooling holes arrangements, were numerically simulated with conjugate heat transfer analysis method for predicting overall cooling effectiveness. The film cooling holes distributed over the nozzle pressure surface were optimized by minimizing the peak temperature, temperature deviation. Additional internal cooling components such as pedestals and rectangular rib turbulators were modeled inside the cooling passages for more efficient heat transfer. The real engine conditions were given for boundary conditions to fluid and solid domains for conjugate heat transfer analysis. Hot combustion gas properties such as specific heat at constant pressure and other transport properties were given as functions of temperature. Also, the conductivity of Inconel 718 was also given as a function of temperature to solve the heat equation in the nozzle solid domain. Conjugate heat transfer analysis results showed that optimized designs showed better cooling performance, especially on the pressure surface due to proper staggering and spacing hole-rows compared to the baseline design. The overall cooling performances were offset from the adiabatic film cooling effectiveness. Locally concentrated heat transfer and corresponding high cooling effectiveness region appeared where internal cooling effects were overlapped in the optimized designs. Also, conjugate heat transfer analysis results for the optimized designs showed more uniform contours of the overall cooling effectiveness compared to the baseline design. By varying the coolant mass flow rate, it was observed that pressure surface was more sensitive to the coolant mass flow rate than nozzle leading edge stagnation region and suction surface. The CHT results showed that optimized designs to improve the adiabatic film cooling effectiveness also have better overall cooling effectiveness.

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.

Heat Transfer Analysis Over a Film Cooled Platform of a Vane Cascade With a Non-Uniform Inlet Flow

2017 ◽  
Author(s):  
G. Barigozzi ◽  
S. Ravelli ◽  
H. Abdeh ◽  
A. Perdichizzi ◽  
M. Henze ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Leading Edge ◽  
Heat Transfer Analysis ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Flow Distortion

This paper reports on heat transfer measurements performed on the film cooled platform of a linear nozzle vane cascade, subject to non-uniform inlet flow conditions. An obstruction, installed upstream of the cascade at different tangential positions, was responsible for inlet flow distortion. The platform cooling system included both purge flow from a slot located upstream of the leading edge and coolant ejection from a row of cylindrical holes located upstream of the slot. Testing was performed at inlet Mach number of Ma1 = 0.12 with both slot and combustor holes blowing at nominal conditions. Measured values of adiabatic film cooling effectiveness on the platform were used to obtain a detailed map of the convective heat transfer coefficient. The final goal was to compute the net heat flux reduction (NHFR), due to film cooling, when varying the relative position between obstruction and airfoil. Aligning the inflow non uniformity with the vane leading edge leads to a detrimental increase in the heat flux into the platform, within the vane passage. Conversely, positive NHFR values are observed over most of the platform surface if the inlet flow distortion is moved toward the suction side of the adjacent vane.

scholarly journals Film Cooling Performance in a Transonic High-pressure Vane: Decoupled Simulation and Conjugate Heat Transfer Analysis

2014 ◽  
Vol 45 ◽  
pp. 1126-1135 ◽  
Author(s):  
Massimiliano Insinna ◽  
Duccio Griffini ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Analysis ◽  
Cooling Performance

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

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Tommaso Bacci ◽  
Riccardo Becchi ◽  
Alessio Picchi ◽  
Bruno 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 (PSP) 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 behavior. 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.

Overall and Adiabatic Effectiveness Values on a Scaled Up, Simulated Gas Turbine Vane: Part II—Numerical Simulations

2011 ◽  
Author(s):  
Gustavo A. Ledezma ◽  
Gregory M. Laskowski ◽  
Jason E. Dees ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Film Cooling ◽  
Gas Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Fluxes ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Overall Effectiveness

Conjugate heat transfer (CHT) calculation techniques for the heat transfer analysis of high-pressure turbines (HPT) have been developed during the past few years. Thus, it has become possible to take into account the coupling of the film, internal cooling, external gas flow and the metal diffusive heat transfer. The coupling problem may become extremely important in regions such as the airfoil leading edge and the vicinity of film hole breakout region where heat fluxes and thermal gradients are high. This article presents the results obtained using fully coupled 3D CHT simulations of a simplified film-cooled leading edge model and a NASA C3X vane with suction side film cooling. The results for the two cases are compared against experimental data obtained at University of Texas at Austin. The numerical simulations were conducted using the k-ω turbulence model. The leading edge model overall effectiveness predictions are in good agreement with the experiments, especially in the low blowing ratio range (1≤M≤2). For the C3X vane, the CHT results tend to underpredict the midspan and laterally averaged effectiveness due to film liftoff. However, the quantitative agreement is still reasonably good. The different levels of overall effectiveness agreement found between all cases are discussed.

Conjugate Heat Transfer Analysis of a Film Cooled High-Pressure Turbine Vane Under Realistic Combustor Exit Flow Conditions

2014 ◽  
Author(s):  
Massimiliano Insinna ◽  
Duccio Griffini ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Boundary Conditions ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Analysis ◽  
Annular Combustor ◽  
Turbulent Closure ◽  
High Pressure Stage ◽  
Turbulence Length

In this paper conjugate heat transfer analysis of the cooled vane of the MT1 research high-pressure stage is presented. Inlet boundary conditions (including non-uniform total temperature, non-uniform total pressure, swirl, turbulence intensity and turbulence length scale) are obtained considering the exit flow field of a reactive annular combustor simulator. The combustor model has been designed in order to reproduce data available in literature about exit profiles of real combustion chambers and other combustor simulators. Steady simulations are performed on a hybrid unstructured grid obtained from a grid dependence study. The transitional kT-kL-ω model by Walters and Cokljat is used as turbulent closure. Thermal fields obtained from CHT analysis of the vane considering two different clocking positions with respect to the combustor are compared. Results, including film cooling parameters and High-Pressure Vane aerodynamics, are also compared with a uniform inlet case showing the crucial importance of considering realistic boundary conditions for thermal analysis of turbine components.

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