An Investigation of the Effects of Film Cooling in a High-Pressure Aeroengine Turbine Stage

2005 ◽  
Author(s):  
Kam S. Chana ◽  
Mary A. Hilditch ◽  
James Anderson
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Phase Iii ◽  
Cooling Effectiveness ◽  
Aerodynamic Efficiency ◽  
Cooling Flow ◽  
External Cooling ◽  
Improved Design ◽  
Density Ratios ◽  
Cooling Air

Cooling is required to enable the turbine components to survive and have acceptable life in the very high gas temperatures occurring in modern engines. The cooling air is bled from the compression system, with typically about 15% of the core flow being diverted in military engines and about 20% in civil turbofans. Cooling benefits engine specific thrust and efficiency by allowing higher cycle temperatures to be employed, but the bleed air imposes cycle penalties and also reduces the aerodynamic efficiency of the turbine blading, typically by 2–4%. Cooling research aims to develop and validate improved design methodologies that give maximum cooling effectiveness for minimum cooling flow. This paper documents external cooling research undertaken in the Isentropic Light Piston Facility at QinetiQ as part of a European collaborative programme on turbine aerodynamics and heat transfer. In Phase I, neither the ngv nor the rotor was cooled; cooling was added to the ngv only for Phase II, and to the rotor and ngv in Phase III. Coolant blowing rates and density ratios were also varied in the experiments. This paper describes the ILPF and summarises the results of this systematic programme, paying particular attention to the variation in aerofoil heat transfer with changing coolant conditions, and the effects coolant ejection has on the aerofoil’s aerodynamic performance.

Nekomimi Film Cooling Holes Configuration Under Conjugate Heat Transfer Conditions

2014 ◽  
Author(s):  
Karsten Kusterer ◽  
Nurettin Tekin ◽  
Tobias Wüllner ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Secondary Flow ◽  
Flow Structure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling Effectiveness ◽  
Cooling Flow ◽  
Secondary Flow Structure ◽  
Cooling Air

In modern gas turbines, the film cooling technology is essential for the protection of the hot parts, in particular of the first stage vanes and blades of the turbine, against the hot gases from the combustion process in order to reach an acceptable life span of the components. As the cooling air is usually extracted from the compressor, the reduction of the cooling effort would directly result in increased thermal efficiency of the gas turbine. Understanding of the fundamental physics of film cooling is necessary for the improvement of the state-of-the-art. Thus, huge research efforts by industry as well as research organizations have been undertaken to establish high efficient film cooling technologies. Today it is common knowledge that film cooling effectiveness degradation is caused by secondary flows inside the cooling jets, i.e. the Counter-Rotating Vortices (CRV) or sometimes also called kidney-vortices, which induce a lift-off of the jet. Further understanding of the secondary flow development inside the jet and how this could be influenced, has led to hole configurations, which can induce Anti-Counter-Rotating Vortices (ACRV) in the cooling jets. As a result, the cooling air remains close to the wall and is additionally distributed flatly along the surface. Beside different other technologies, the NEKOMIMI cooling technology is a promising approach to establish the desired ACRVs. It consists of a combination of two holes in just one configuration so that the air is distributed mainly on two cooling air streaks following the special shape of the generated geometry. The NEKOMIMI configuration and two conventional cooling hole configurations (cylindrical and shaped holes) has been investigated numerically under adiabatic and conjugate heat transfer conditions. The influence of the conjugate heat transfer on the secondary flow structure has been analysed. In conjugate heat transfer calculations, it cannot directly derived from the surface temperature distribution if the reached cooling effectiveness values are due to the improved hole configuration with improved secondary flow structure or due to the heat conduction in the material. Therefore, a methodology has been developed, to distinguish between cooling effectiveness due to heat conduction in the material and film cooling flow over the surface. The numerical results shows that for the NEKOMIMI configuration, 77% of the reached overall cooling effectiveness is due to film cooling with improved flow structure in the secondary flow (ACRV) and 23% due to heat conduction in the material. For the cylindrical hole configuration, 10% of the reached overall cooling effectiveness is due to the film cooling flow structure and 90% due to heat conduction in the material.

Influence of Coolant on Cooling Performance Sensitivity of Internally Convective Turbine Vane

2021 ◽  
Author(s):  
Thanapat Chotroongruang ◽  
Prasert Prapamonthon ◽  
Rungsimun Thongdee ◽  
Thanapat Thongmuenwaiyathon ◽  
Zhenxu Sun ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Film Cooling ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Turbine Engine ◽  
Performance Sensitivity ◽  
Turbine Vane ◽  
Cooling Air

Abstract Based on the Brayton cycle for gas-turbine engines, the high thermal efficiency and power output of a gas-turbine engine can be obtainable when the gas-turbine engine operates at high turbine inlet temperatures. However, turbine components e.g., inlet guide vane, rotor blade, and stator vane request high cooling performance. Typically, internal cooling and film cooling are two effective techniques that are widely used to protect high thermal loads for the turbine components in a state-of-the-art gas turbine. Consequently, the high thermal efficiency and power output can be obtained, and the turbine lifespan can be prolonged, also. On top of that, a comprehensive understanding of flow and heat transfer phenomena in the turbine components is very important. As a result, both experiments and simulations have been used to improve the cooling performance of the turbine components. In fact, the cooling air used in the internal cooling and film cooling is partially extracted from the compressor. Therefore, variations in the cooling air affect the cooling performance of the turbine components directly. This paper presents a numerical study on the influence of the cooling air on cooling-performance sensitivity of an internally convective turbine vane, MARK II using the computational fluid dynamics (CFD)/conjugate heat transfer (CHT) with the SST k-ω turbulence model. Result comparisons are conducted in terms of pressure, temperature, and cooling effectiveness under the effects of the inlet temperature, mass flow rate, turbulence intensity, and flow direction of the cooling air. The cooling-performance sensitivity to the coolant parameters is shown through variations of local cooling effectiveness, and area and volume-weighted average cooling effectiveness.

Experimental and Numerical Analysis of High Temperature Gas Turbine Nozzle Vane Convective and Film Cooling Effectiveness

2011 ◽  
Author(s):  
Victoria Krivonosova ◽  
Alexander Lebedev ◽  
Nicolay Simin ◽  
Michael Zolotogorov ◽  
Nicolay Kortikov
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Flow Model ◽  
Numerical Models ◽  
Internal Flow ◽  
Temperature Fields ◽  
One Dimension ◽  
Test Results ◽  
Cooling Effectiveness ◽  
Cooling Air

This paper presents the results of experimental and numerical investigations of cooling effectiveness of the film cooled turbine nozzle. The nozzle is with two internal cavities. Front cavity of the nozzle is fed with high pressure cooling air from compressor diffuser with minimal losses of pressure for ensuring film cooling of the leading edge. Rear cavity is with impingement tube for high effective convective cooling. Experimental measurements of cooling flow capacity and cooling effectiveness were carried out on experimental facility of OSC “NPO CKTI”. Investigations included isothermal internal flow tests and hot tests with internal flow and metal temperature measurements. Test results were compared with flow and thermal field CFD predictions. Temperature fields of body and platforms of nozzle were predicted by conjugate heat transfer simulation. Computation domain includes vane-to-vane path flow, vane solid body with shrouds and holes for cooling air injection. Heat transfer conditions inside vane were calculated with one dimension internal flow model. Isothermal internal flow test results were used to validate one dimension internal flow model. Comparison of the experimental and simulation results enabled to modify calculation models to obtain good agreement. Turbine vane temperature fields calculations in different operation conditions were carried out with validated numerical models.

The Influence of Rotating Speed on Film Cooling Characteristics on GE-E3 Blade Tip With Different Tip Configurations

2009 ◽  
Author(s):  
D. H. Zhang ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cooling Effectiveness ◽  
Rotating Speed ◽  
Tip Leakage ◽  
Blowing Ratio ◽  
Blade Tip ◽  
Cooling Air

The film cooling phenomenon of flat tip (with or without a trench) and squealer tip on GE-E3 blade in rotating state was numerically studied. The effect of tip configuration, rotating speed and blowing ratio on the blade tip flow and cooling performance was revealed. It was found that the squealer tip and the flat tip with trenched hole have comparability in configuration: both have a cavity at the end of the film hole. So the coolant momentum and the tip leakage flow velocity in the cavity are decreased, which contributes to the improvement of the cooling effect. Because of the bigger cavity of the squealer tip than that of the flat tip with trenched hole, the cooling air and the leakage flow mix adequately in the cavity, the squealer tip can get the highest cooling effectiveness and the lowest heat transfer coefficient value both in stationary and rotating state, and the flat tip with trenched hole follows. With the increase of rotating speed, for all the three configurations, the area-averaged cooling effectiveness decreases and the area-averaged heat transfer coefficient increases. At the same time, the tip leakage flow entraps the cooling air moving toward the leading edge. And with the increase of the blowing ratio, for all the configurations, the area-averaged cooling effectiveness increases while the area-averaged heat transfer coefficients decreases.

scholarly journals Effects of Various Modeling Schemes on Mist Film Cooling Simulation

2005 ◽  
Author(s):  
Xianchang Li ◽  
Ting Wang
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Turbulence Models ◽  
Cooling Effectiveness ◽  
Air Supply ◽  
Cooling Enhancement ◽  
Simulation Results ◽  
Density Ratios ◽  
Slot Film Cooling ◽  
Cooling Air

Numerical simulation is performed in this study to explore film-cooling enhancement by injecting mist into the cooling air with a focus on investigating the effect of various modeling schemes on the simulation results. The effect of turbulence models, dispersed-phase modeling, inclusion of different forces (Saffman, thermophoresis, and Brownian), trajectory tracking, and mist injection scheme is studied. The effect of flow inlet boundary conditions (with/without air supply plenum), inlet turbulence intensity, and the near-wall grid density on simulation results is also included. Using a 2-D slot film cooling simulation with a fixed blowing angle and blowing ratio shows a 2% mist injected into the cooling air can increase the cooling effectiveness about 45%. The RNG k-ε model, RSM and the standard k-ε turbulence model with the enhanced wall treatment produce consistent and reasonable results while the turbulence dispersion has a significant effect on mist film cooling through the stochastic trajectory calculation. The thermophoretic force slightly increases the cooling effectiveness, but the effect of Brownian force and Saffman lift is imperceptible. The cooling performance is affected negatively by the plenum in this study, which alters the velocity profile and turbulence intensity at the jet exit plane. The results of this paper can serve as the qualification reference for future more complicated studies including 3-D cooling holes, different blowing ratios, various density ratios, and rotational effect.

Film Cooling and Heat Transfer Performance of a Fully-Cooled Turbine Vane at Varied Density Ratios and Mass Flow Ratios

2020 ◽  
Author(s):  
Chun-yi Yao ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Bo-lun Zhang ◽  
Xin-lei Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Density Ratios

Abstract A number of experimental studies have been performed to study the effect of geometric and aerodynamic parameters on the film cooling performance on the flat plate and turbine blade, however, the experimental investigations on a fully-cooled turbine vane is limited, especially at different density ratios. Consequently, an experiment on a fully-cooled turbine vane with multi-row film cooling holes was carried out to investigate the effect of mass flow ratio and density ratio on the film cooling performance, in which the film cooling effectiveness and heat transfer coefficient was measured by transient liquid crystal. The mainstream inlet Reynolds number based on the inlet velocity and the true chord length is 120000 and the mainstream turbulence intensity is 15%, three mass flow ratios of 5.5%, 8.4% and 11% and two density ratios of 1.0 and 1.5 were tested. The air was selected as the mainstream, the air and carbon dioxide were independently selected as secondary flow to produce two density ratios of 1.0 and 1.5. The test vane is similar in geometry to a first stage turbine vane of a normal aeroengine. Two cavities were manufactured in the test vane to feed 18 rows of film cooling holes. Results show that with the mass flow ratio increasing for DR = 1.0 and 1.5, the film cooling effectiveness on pressure side gradually increases, however, that on the suction side gradually decreases. Generally, increased density ratio produces higher film cooling effectiveness because the injection momentum was reduced, however, the film cooling effectiveness on the suction side for DR = 1.5 is lower than that for DR = 1.0. The coolant outflow significantly enhances the surface heat transfer coefficient for 0 < S/C < 0.5 and S/C < −0.5. The heat transfer coefficient in the leading edge is less affected by the density ratio, however, the increase in density ratio reduces the heat transfer coefficient ratio in other regions, especially for large mass flow ratios.

Heat transfer characteristics analysis on a fully cooled vane with varied density ratios

2021 ◽  
pp. 1-19
Author(s):  
Chunyi Yao ◽  
Zheng Zhang ◽  
Bo-lun Zhang ◽  
Hui Ren Zhu ◽  
Cun Liang Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Coolant Injection ◽  
Density Ratios

Abstract The objective of this experimental investigation was to determine the cooling performance of a fully cooled vane with 18 rows of cylinder cooling holes. The exit Reynolds number in the wind tunnel normalized by the true chord was 500,000 with a turbulence intensity of 15%. The film cooling effectiveness and heat transfer coefficient distribution were obtained by the transient liquid crystal technology, three mass flow ratios (MFR=7.0%, 9.9%, 11%) and two density ratios (DR=1.0, 1.5) were tested. The results show that the film cooling effectiveness distribution on the suction side is more uniform and the coolant injection trajectory is much longer than that on the pressure side. As the density ratio increasing to 1.5, the more laterally uniform film cooling effectiveness contour on the pressure side is observed and the spatially averaged film cooling effectiveness is increased by 11%∼43%. For the MFR=7.0%, the coolant injection with low momentum thickens the boundary layer and reduces the heat transfer coefficient in the mid-chord region of the pressure side. Both the increased mass flow ratio and decreased density ratio result in a higher heat transfer coefficient, while do not alter the distribution trend. By calculating the heat flux ratio, the reduction in the heat flux at DR=1.5 is found to be within 20% in most areas than that of DR=1.0 on the vane surface.

scholarly journals Effects of Various Modeling Schemes on Mist Film Cooling Simulation

2007 ◽  
Vol 129 (4) ◽  
pp. 472-482 ◽  
Author(s):  
Xianchang Li ◽  
Ting Wang
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Cooling Effectiveness ◽  
Air Supply ◽  
Cooling Enhancement ◽  
Simulation Results ◽  
Density Ratios ◽  
Cooling Air

Numerical simulation is performed in this study to explore film-cooling enhancement by injecting mist into the cooling air with a focus on investigating the effect of various modeling schemes on simulation results. The effect of turbulence models, dispersed-phase modeling, inclusion of different forces (Saffman, thermophoresis, and Brownian), trajectory tracking, and mist injection scheme is studied. The effect of flow inlet boundary conditions (with/without air supply plenum), inlet turbulence intensity, and the near-wall grid density on simulation results is also included. Simulation of a two-dimensional (2D) slot film cooling with a fixed blowing angle and blowing ratio shows a 2% mist (by mass) injected into the cooling air can increase the cooling effectiveness about 45%. The renormalization group (RNG) k-ε model, Reynolds stress model, and the standard k-ε turbulence model with an enhanced wall treatment produce consistent and reasonable results while the turbulence dispersion has a significant effect on mist film cooling through the stochastic trajectory calculation. The thermophoretic force slightly increases the cooling effectiveness, but the effect of Brownian force and Saffman lift is imperceptible. The cooling performance deteriorates when the plenum is included in the calculation due to the altered velocity profile and turbulence intensity at the jet exit plane. The results of this paper can provide guidance for corresponding experiments and serve as the qualification reference for future more complicated studies with 3D cooling holes, different blowing ratios, various density ratios, and rotational effect.

Conjugate Heat Transfer Predictions of Effusion Cooling With Shaped Trench Outlet

2014 ◽  
Author(s):  
H. I. Oguntade ◽  
G. E. Andrews ◽  
A. D. Burns ◽  
D. B. Ingham ◽  
M. Pourkashanian
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
Conjugate Heat Transfer ◽  
Vertical Wall ◽  
Superior Performance ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Air

The influence of the application of a filleted shape trench hole outlet on the overall cooling effectiveness of a flat hot effusion Nimonic 75 metal wall with a 770K hot gas crossflow was investigated using conjugate heat transfer (CHT) CFD and the Ansys Fluent code. The baseline effusion wall had ten rows of holes with an X/D of 4.65 and a wall thickness of 6.35mm with normal injection holes. This was modelled and showed good agreement with the experimental results for overall cooling effectiveness. The aim of the work was to use these validated CHT CFD procedures to investigate improved hole outlet designs with 30° inclined effusion of X/D = 4.65 with improved hole outlet designs using various trench designs. The predictions involved the use of a gas tracer in the cooling air to simultaneously separate the predicted adiabatic film cooling effectiveness from the overall cooling effectiveness. The shaped trench outlet effusion wall designs were predicted to have a superior performance compared with the 90° effusion wall cooling design. This was due to the improved adiabatic film cooling. An increase in the trailing edge vertical wall depth of the trenched effusion wall design from 0.5D to 0.75D increased the overall and adiabatic cooling effectiveness. The filleted shaped trench outlet effusion wall only required a small amount of cooling air to achieve a satisfactory cooling performance. It was predicted that this new effusion wall design could enable a significant reduction in the coolant mass flow for cooled metal surfaces in in future high performance gas turbines.

Time-Resolved Film-Cooling Flows at High and Low Density Ratios

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Molly K. Eberly ◽  
Karen A. Thole
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Particle Image Velocimetry Data ◽  
Round Hole ◽  
Cooling Effectiveness ◽  
Time Resolved ◽  
Cooling Flow ◽  
Image Velocimetry ◽  
Cooling Hole ◽  
Density Ratios

Film-cooling is one of the most prevalent cooling technologies that is used for gas turbine airfoil surfaces. Numerous studies have been conducted to give the cooling effectiveness over ranges of velocity, density, mass flux, and momentum flux ratios. Few studies have reported flowfield measurements with even fewer of those providing time-resolved flowfields. This paper provides time-averaged and time-resolved particle image velocimetry data for a film-cooling flow at low and high density ratios. A generic film-cooling hole geometry with wide lateral spacing was used for this study, which was a 30 deg inclined round hole injecting along a flat plate with lateral spacing P/D = 6.7. The jet Reynolds number for flowfield testing varied from 2500 to 7000. The data indicate differences in the flowfield and turbulence characteristics for the same momentum flux ratios at the two density ratios. The time-resolved data indicate Kelvin–Helmholtz breakdown in the jet-to-freestream shear layer.

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