Investigation on Cooling Performance of Impingement Cooling Devices Combined With Pins

2005 ◽  
Author(s):  
Dongliang Quan ◽  
Songling Liu ◽  
Jianghai Li ◽  
Gaowen Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Film Cooling ◽  
Internal Heat ◽  
Cooling Effectiveness ◽  
Impingement Cooling ◽  
One Dimensional ◽  
Pin Fin ◽  
Cooling Devices ◽  
Internal Heat Transfer

Integrated impingement and pin fin cooling devices have comprehensive advantages of hot-side film cooling, internal impingement cooling, large internal heat transfer area and enhanced heat exchange caused by the pin fin arrays, so it is considered a promising cooling concept to meet the requirements of modern advanced aircraft engines. In this paper, experimental study, one dimensional model analysis and numerical simulation were conducted to investigate cooling performance of this kind of cooling device. A typical configuration specimen was made and tested in a large scale low speed closed-looped wind tunnel. The cooling effectiveness was measured by an infrared thermography technique. The target surface was coated carefully with a high quality black paint to keep a uniform high emissivity condition. The measurements were calibrated with thermocouples welded on the surface. Detailed two-dimensional contour maps of the temperature and cooling effectiveness were obtained for different pressure ratios and therefore different coolant flow-rates through the tested specimen. The experimental results showed that very high cooling effectiveness can be achieved by this cooling device with relatively small amount of coolant flow. Based on the theory of transpiration cooling in porous material, a one dimensional heat transfer model was established to analyze the effect of various parameters on the cooling effectiveness. The required resistance and internal heat transfer characteristics were obtained from experiments. It was found from this model that the variation of heat transfer on the gas side, including heat transfer coefficient and film cooling effectiveness, of the specimen created much more effect on its cooling effectiveness than that of the coolant side. The heat transfer intensities inside the specimen played an important role in the performance of cooling. In the last part of this paper, a conjugate numerical simulation was carried out using commercial software FLUENT 6.1. The domain of the numerical simulation included the specimen and the coolant. Detailed temperature contours of the specimen were obtained for various heat transfer boundary conditions. The calculated flow resistance and cooling effectiveness agree well with the experimental data and the predictions with the one-dimensional analysis model. The numerical simulations reveal that the impingement of the coolant jets in the specimen is the main contribution to the high cooling effectiveness.

Overall Cooling Effectiveness Characteristic and Influence Mechanism on an Endwall With Film Cooling and Impingement

2015 ◽  
Author(s):  
Mingfei Li ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Internal Heat ◽  
Main Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
One Dimensional ◽  
Influence Mechanism ◽  
Endwall Cooling ◽  
Internal Heat Transfer

The cooling system is required to ensure gas turbine can work at high temperature, which has exceeded the material limitation. An endwall cooling test rig was built up to conduct the endwall cooling research. A detailed work was done for analyzing characteristics of endwall heat transfer and discussing the multi-parameter influence mechanism of overall cooling effectiveness. The main flow side heat transfer coefficient, adiabatic film cooling effectiveness and overall cooling effectiveness were measured in the experiments. The effects of coolant mass flowrate ratio (MFR) were considered through the measurement. In order to analyze how each of the parameters works on overall cooling effectiveness, a one-dimensional correlation was developed. The results showed that obvious enhancement could be found in cooling effectiveness by increasing coolant MFR, and the film jet can be easily attached to the surface after the acceleration of the main flow in the nozzle channel. Comparing with film cooling effectiveness, overall cooling effectiveness distribution is more uniform, which is due to the influence of internal cooling. The verified one-dimensional analysis method showed that the improvement in film cooling would be most efficient to heighten overall cooling effectiveness. The improvement in film cooling would be more efficient when film cooling effectiveness is in high level than in low level. However, the enhancement of internal heat transfer is more efficient when internal heat transfer coefficient is low.

Influence of Pin Shape on Heat Transfer Characteristics of Laminated Cooling Configuration

2019 ◽  
Author(s):  
Lei Li ◽  
Honglin Li ◽  
Wenjing Gao ◽  
Fujuan Tong ◽  
Zhonghao Tang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Heat Transfer Performance ◽  
Internal Flow ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Cooling Effectiveness ◽  
Pin Fin ◽  
Blowing Ratio ◽  
Transfer Characteristics

Abstract The laminated cooling configuration can effectively enhance heat transfer and improve cooling effectiveness through combining the advantage of impingement cooling, film cooling and pin fin cooling. In this study, four laminated configurations with different pin shape including circular pin shape, curved rib pin shape, droplet pin shape and reverse droplet pin shape are numerically investigated. Extensive analysis are conducted within the blowing ratio range of 0.2–1.8 to reveal the influence of pin shape on heat transfer characteristics and cooling performance. Compared with circular pin shape, other three pin shapes can enable more complex internal flow field, which greatly affect the heat transfer performance. Among these shapes, the droplet pin shape presents the best capacity on improving heat transfer performance and distribution due to its stramlined shape and little upstream surface, especially at relatively high blowing ratio and the augmentation can be up to 7.91% under the blowing ratio of 1.7. Besides, results show that the cooling effectiveness can be enhanced by adopting curved rib pin shape and the enhancement monotonously increases as the blowing ratio increases. When blowing ratio is 1.7, the improvement can be 2.7%. The reason is that the large lateral blockage decreases the exhausted velocity and hence forms relative firm film coverage.

A Novel Technique for the Internal Blade Cooling

1996 ◽  
Author(s):  
B. Glezer ◽  
H. K. Moon ◽  
T. O’Connell
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Swirling Flow ◽  
Internal Heat ◽  
Leading Edge ◽  
Manufacturing Cost ◽  
Air Cooling ◽  
Smooth Channel ◽  
Highly Effective ◽  
Internal Heat Transfer

Development of an adequate air cooling system for the thermally highly loaded leading edge and tip of the blade, that is cost effective and also relatively insensitive to manufacturing tolerances and operating environment continues to be one of the major challenges in advanced gas turbine design. Extensive studies on the convective (including impingement) and film cooling techniques produced remarkable progress in achieving a high cooling effectiveness level for turbine airfoils. However, in the case of turbine blades, application of these techniques has severe limitations. Highly effective impingement cooling needs to be combined with film discharge of the spent air to avoid a negative impact of crossflow on internal heat transfer and also provide additional thermal protection of the surface downstream of the discharge holes. Noticeable aerodynamic penalties, stress concentration and significant increase in manufacturing cost limit application of blade film cooling, particularly for moderately high operating temperatures. Search for a highly effective robust design of internal airfoil cooling which can delay the use of film cooling resulted in the creation of a new technique which is described in this paper. This technique is based on generation of a swirling flow structure in the blade internal leading edge passage. Significant heat transfer augmentation can be achieved when the cooling air is delivered into the leading edge plenum tangentially to the inner concave surface. The best results can be obtained when the swirling flow is allowed to move radially, creating a three-dimensional screw-shaped flow in the plenum. The presented results of the flow and heat transfer studies performed for the practical range of Reynolds numbers for the internal flow show that the leading edge screw-shaped cooling technique provides internal heat transfer rate comparable with impingement coupled with film discharge of the spent air, is more effective than impingement with cross flow and is almost five times higher than heat transfer in the smooth channel.

Aero-Thermal Design and Validation of an Advanced Turbine

2012 ◽  
Author(s):  
S. Naik ◽  
T. P. Sommer ◽  
M. Schnieder
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Speed ◽  
Internal Heat ◽  
Thermal Design ◽  
Operating Characteristics ◽  
Local Flow ◽  
Subsequent Performance ◽  
Computational Fluid Dynamics Analysis ◽  
Internal Heat Transfer

This paper describes the aero-thermal design and validation of an advanced axial flow turbine. This turbine, which has evolved from the existing and proven GT26/GT24 design consists of an optimised annulus flow path using high lift airfoil profiles and improved aerodynamic matching between the turbine stages. A major design feature of the turbine has been to control and reduce the aerodynamic losses, with particular attention being devoted to minimising the secondary, trailing edge and blade tip losses. The advantages of these design changes to the overall turbine efficiency has been verified by extensive controlled experimentation in high-speed cascade test facilities; by the utilisation of 3D multi-row computational fluid dynamics analysis tools, and via engine tests. In addition to the aerodynamic design modifications of the turbine, the thermal designs of the turbine vanes, blades and heat-shields were also optimised. For the first stage film cooled vane and blade airfoils and platforms, both the film cooling layout and operating characteristics were improved. And for all the internally cooled airfoils, the internal heat transfer design features were additionally optimised, which allowed for more homogenous metal temperature distributions on the airfoil and endwall surfaces. The verification and validation of the thermal designs of the turbine components was confirmed via extensive dedicated testing in high-speed cascades for the film cooling performances, and in scaled perspex models for the internal heat transfer coefficients and local flow distributions. The complete turbine was further tested and validated in the GT26 Test Power Plant in Birr, Switzerland via a dedicated turbine thermal paint test run and a subsequent performance and mapping testing phase.

Effects of Internal and Film Cooling on the Overall Effectiveness of a Fully Cooled Turbine Airfoil With Shaped Holes

2016 ◽  
Author(s):  
Kyle Chavez ◽  
Thomas N. Slavens ◽  
David Bogard
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Film Cooling ◽  
Internal Heat ◽  
Transfer Coefficients ◽  
Engine Component ◽  
Adiabatic Effectiveness ◽  
Internal Heat Transfer ◽  
Effectiveness Data ◽  
Overall Effectiveness

Adiabatic and overall effectiveness levels were measured in a closed loop linear test section using an inlet Reynolds number of 120,000 for an airfoil model at its designed inlet angle of −30.1°. Two models were used in the study — one made of a low thermal conductivity foam, and one of a higher thermal conductivity material which allowed for the Biot number of the second model to match that of the engine component. Since the ratio of the external to internal heat transfer coefficients were also matched to the engine component, the second model was thermally scaled to the actual engine component, allowing for the measurement of the overall effectiveness of the airfoil. The effects of the internal and film cooling on the overall effectiveness were examined in detail. The cooling configuration consisted of 9 rows of shaped holes, with 5 rows of conical shaped holes at the leading edge, one laidback fan-shaped gill-row, and three laidback fan-shaped holes positioned farther downstream. Furthermore, the model contained three internal coolant passages including an impingement cavity and a serpentine passage. The internal passages were lined with internal rib turbulators to enhance the internal heat transfer coefficient. This study had two main goals. First, assess the performance of a fully-cooled airfoil with shaped holes through measurements of adiabatic, internal, and overall effectiveness levels. Second, examine the effects of shaped holes and the utilization of a conduction correction on the capability to predict overall effectiveness with a simple 1D model. It was found that although the large spacing of the holes in the showerhead region produced low adiabatic effectiveness levels, the through-hole convection and impingement provided adequate levels of cooling, resulting in relatively uniform overall effectiveness levels. It was also found that although the shaped film-cooling holes have a significant effect on the 3D conduction throughout the model, the overall effectiveness is still well predicted between rows of holes, but only when a significant conduction correction to the adiabatic effectiveness data is applied. This study highlights the necessity of applied conduction corrections to adiabatic effectiveness data collected with IR thermography, highlights the use of shaped holes in the showerhead region, and confirms the utility of 1D predictive models for overall effectiveness, even for models utilizing shaped holes.

Cooling Performance of an Integrated Impingement and Pin Fin Cooling Configuration

2003 ◽  
Author(s):  
Shigemichi Yamawaki ◽  
Chiyuki Nakamata ◽  
Ryouji Imai ◽  
Shinsuke Matsuno ◽  
Toyoaki Yoshida ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Unit Area ◽  
Rapid Prototype ◽  
Cooling Effectiveness ◽  
Impingement Cooling ◽  
Casting Technique ◽  
Fin Efficiency ◽  
Pin Fin ◽  
Pin Geometry ◽  
Efficiency Theory

The cooling configuration adopted in this study integrates impingement cooling and pin fin cooling devices into one body, the aim being enhancement of the effective heat transfer area. The purpose of the study is to confirm improvement of cooling effectiveness for two different pin density configurations by experimental verification. Experiments were conducted in similar conditions to actual engines using large-scaled flat-plate specimens manufactured by a new rapid prototype casting technique. The results were compared with predictions by one-dimensional analysis adopting the fin efficiency theory. Although the coarse pin density, one pin in a unit area, shows good agreement with the prediction, the fine pin density, four pins in the unit area, was overpredicted. It was found by numerical analysis that heat transfer of the new pin geometry did not increase, so that its surface area increased. CFD-aided prediction was proposed and validated with two specimen’s data.

Full Thermal Experimental Assessment of a Dendritic Turbine Vane Cooling Scheme

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
S. Luque ◽  
J. Batstone ◽  
D. R. H. Gillespie ◽  
T. Povey ◽  
E. Romero
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Pressure Ratio ◽  
Internal Heat ◽  
Flux Ratio ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Experimental Assessment ◽  
Film Cooling Effectiveness ◽  
Internal Heat Transfer

A full thermal experimental assessment of a novel dendritic cooling scheme for high-pressure turbine vanes has been conducted and is presented in this paper, including a comparison to the current state-of-the-art cooling arrangement for these components. The dendritic cooling system consists of cooling holes with multiple internal branches that enhance internal heat transfer and reduce the blowing ratio at hole exit. Three sets of measurements are presented, which describe, first, the local internal heat transfer coefficient of these structures and, secondly, the cooling flow capacity requirements and overall cooling effectiveness of a highly engine-representative dendritic geometry. Full-coverage surface maps of overall cooling effectiveness were acquired for both dendritic and baseline vanes in the Annular Sector Heat Transfer Facility, where scaled near-engine conditions of Mach number, Reynolds number, inlet turbulence intensity, and coolant-to-mainstream pressure ratio (or momentum flux ratio) are achieved. Engine hardware was used, with laser-sintered metal counterparts for the novel cooling geometry (their detailed configuration, design, and manufacture are discussed). The dendritic system will be shown to offer improved overall cooling effectiveness at a reduced cooling mass flow rate due to a more uniform film cooling effectiveness, a decreased tendency for films to lift off in regions of low external cross flow, improved through-wall heat transfer and internal cooling efficiency, increased internal wetted surface area of the cooling holes, and the enhanced turbulence induced in them.

Film Cooling Characteristic of Double-Fan-Shaped Film Cooling Holes

2009 ◽  
Author(s):  
Jiang-Tao Bai ◽  
Hui-ren Zhu ◽  
Cun-liang Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Diameter Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
Film Cooling Holes

The film cooling performance downstream of a single row of double-fan-shaped film cooling holes in a flat plate have been investigated by experimental measurements and numerical simulation. The entrance and exit of double-fan-shaped holes are comprised of a lateral expansion of 15° from the original simple cylindrical shape with stream-wise inclination of 45°. The width of the exit face to cylinder diameter ratio is 1.5; the length-to-diameter ratio is 4.24 and the pitch-to-diameter ratio is 3. The experimental method used to obtain the adiabatic film cooling effectiveness values and the heat transfer coefficient is a transient narrow band liquid crystal technique. Both film cooling effectiveness and heat transfer coefficient are measured at three momentum ratios (I = 0.5, 1, 2) at constant Reynolds number (Re = 10000) and free stream turbulence (Tu = 2%). The film cooling effectiveness, heat transfer coefficient and Net Heat Flux Reduction (NHFR) are presented for detailed distribution and span-wise averaged values. Discharge coefficients are also measured in the experiment. A commercial package is used to numerically simulate the flow and heat transfer of double-fan-shaped holes; simple cylindrical holes are also simulated for comparison. Numerical simulation use RNG turbulence model with a standard wall function for near wall region. Experimental and Numerical simulation results show that: 1) the double-fan-shaped holes present higher discharge coefficient than simple cylindrical holes at respective momentum ratio; 2) the numerical simulation film cooling effectiveness results of double-fan-shaped holes accord well with the experimental results; 3) at measured three momentum ratios, the double-fan-shaped holes demonstrate better film cooling performance (higher NHFR) than simple cylindrical holes, better film cooling expansion on span-wise; 4) the best momentum ratio of double-fan-shaped holes is 0.5.

Adiabatic and Overall Effectiveness for the Showerhead Film Cooling of a Turbine Vane

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Marc L. Nathan ◽  
Thomas E. Dyson ◽  
David G. Bogard ◽  
Sean D. Bradshaw
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Internal Heat ◽  
Flux Ratio ◽  
Coolant Temperature ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Turbine Vane ◽  
Dynamics Simulations ◽  
Overall Effectiveness

There have been a number of previous studies of the adiabatic film effectiveness for the showerhead region of a turbine vane, but no previous studies of the overall cooling effectiveness. The overall cooling effectiveness is a measure of the external surface temperature relative to the mainstream temperature and the inlet coolant temperature, and consequently is a direct measure of how effectively the surface is cooled. This can be determined experimentally when the model is constructed so that the Biot number is similar to that of engine components, and the internal cooling is designed so that the ratio of the external to internal heat transfer coefficient is matched to that of the engine. In this study, the overall effectiveness was experimentally measured on a model turbine vane constructed of a material to match Bi for engine conditions. The model incorporated an internal impingement cooling configuration. The cooling design consisted of a showerhead composed of five rows of holes with one additional row on both pressure and suction sides of the vane. An identical model was also constructed out of low conductivity foam to measure adiabatic film effectiveness. Of particular interest in this study was to use the overall cooling effectiveness measurements to identify local hot spots which might lead to failure of the vane. Furthermore, the experimental measurements provided an important database for evaluation of computational fluid dynamics simulations of the conjugate heat transfer effects that occur in the showerhead region. Continuous improvement in both measures of performance was demonstrated with increasing momentum flux ratio.

scholarly journals Gas Turbine Studies at Oxford 1969–1987

1988 ◽  
Author(s):  
T. V. Jones
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Film Cooling ◽  
Internal Heat ◽  
Simulation Experiments ◽  
Transient Techniques ◽  
Oxford University ◽  
Gas Turbine Heat Transfer ◽  
Transfer Testing ◽  
Internal Heat Transfer

Gas turbine heat transfer studies commenced at Oxford University in 1969 when transient techniques previously used for measurements in hypersonic flows were applied to the gas turbine environment. Shock tubes were employed and subsequently a new form of transient tunnel, the Isentropic Light Piston Tunnel, was developed specifically for turbine heat transfer testing. During the following years further short duration facilities were developed to study blade and vane external aerodynamics and also the heat transfer in cooling passages was examined using liquid crystal techniques. All these transient facilities are described and the development of the instrumentation peculiar to these is explained. The results of the work on external and internal heat transfer are summarised. In particular, the film cooling studies, the blade and vane external heat transfer work and the wake simulation experiments are outlined. This paper is dedicated to the late Don Schultz.

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