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.

Full Thermal Experimental Assessment of a Dendritic Turbine Vane Cooling Scheme

2012 ◽  
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 comparisons to the conventional cooling arrangement for these components. The dendritic cooling system consists of cooling holes with multiple internal branches which 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.

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.

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.

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

2012 ◽  
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 ◽  
Engine Components ◽  
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 CFD 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.

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.

Film Cooling Effectiveness and Heat Transfer Near Deposit-Laden Film Holes

2009 ◽  
Author(s):  
Scott Lewis ◽  
Brett Barker ◽  
Jeffrey P. Bons ◽  
Weiguo Ai ◽  
Thomas H. Fletcher
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Density Ratio ◽  
Flux Ratio ◽  
Deposition Pattern ◽  
Primary Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
The Impact

Experiments were conducted to determine the impact of synfuel deposits on film cooling effectiveness and heat transfer. Scaled up models were made of synfuel deposits formed on film-cooled turbine blade coupons exposed to accelerated deposition. Three distinct deposition patterns were modeled: a large deposition pattern (max deposit peak ≅ 2 hole diameters) located exclusively upstream of the holes, a large deposition pattern (max deposit peak ≅ 1.25 hole diameters) extending downstream between the cooling holes, and a small deposition pattern (max deposit peak ≅ 0.75 hole diameter) also extending downstream between the cooling holes. The models featured cylindrical holes inclined at 30 degrees to the surface and aligned with the primary flow direction. The spacing of the holes were 3, 3.35, and 4.5 hole diameters respectively. Flat models with the same film cooling hole geometry and spacing were used for comparison. The models were tested using blowing ratios of 0.5–2 with a turbulent approach boundary layer and 0.5% freestream turbulence. The density ratio was approximately 1.1 and the primary flow Reynolds number at the film cooling row location was 300,000. An infrared camera was used to obtain the film cooling effectiveness from steady state tests and surface convective heat transfer coefficients using transient tests. The model with upstream deposition caused the primary flow to lift off the surface over the roughness peaks and allowed the coolant to stay attached to the model. Increasing the blowing ratio from 0.5 to 2 only expanded the region that the coolant could reach and improved the cooling effectiveness. Though the heat transfer coefficient also increased at high blowing ratios, the net heat flux ratio was still less than unity, indicating film cooling benefit. For the two models with deposition between the cooling holes, the free stream air was forced into the valleys in line with the coolant holes and degraded area-averaged coolant performance at lower blowing ratios. It is concluded that the film cooling effectiveness is highest when deposition is limited to upstream of the cooling holes. When accounting for the insulating effect of the deposits between the film holes, even the panels with deposits downstream of the film holes can yield a net decrease in heat flux for some cases.

Heat Transfer Enhancement for Gas Turbine Internal Cooling by Application of Double Swirl Cooling Chambers

2013 ◽  
Author(s):  
Karsten Kusterer ◽  
Gang Lin ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
Ryozo Tanaka ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Gas Turbine ◽  
Internal Heat ◽  
Numerical Results ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Cooling Channels ◽  
Swirl Chamber ◽  
Internal Heat Transfer

Improvement of the gas turbine thermal efficiency can be achieved by reducing the cooling fluid amount in internal cooling channels with enhanced convective cooling. Nowadays the state of the art internal cooling technology for thermally high-loaded gas turbine blades consists of multiple serpentine-shaped cooling channels with angled ribs. Besides, huge effort is put on the development of more advanced internal cooling configurations with further internal heat transfer enhancements. Swirl chamber flow configurations, in which air is flowing through a pipe with a swirling motion generated by tangential jet inlet, have a potential for application as such advanced technology. This paper presents the validation of numerical results for a standard swirl chamber, which has been investigated experimentally in a reference publication. The numerical results obtained with application of the SST k-ω model show the best agreement with the experiment data in compare with other turbulence models. It has been found at the inlet region that the augmentation of the heat transfer is nearly seven times larger than the fully developed non-swirl flow. Within the further numerical study, another cooling configuration named Double Swirl Chambers (DSC) has been obtained and investigated. The numerical results are compared to the reference case. With the same boundary conditions and Reynolds number, the heat transfer coefficients are higher for the DSC configuration than for the reference configuration. In particular at the inlet region, the DSC configuration has even higher circumferentially averaged heat transfer enhancement in one section by approximately 41%. The globally-averaged heat transfer enhancement in DSC configuration is 34.5% higher than the value in the reference SC configuration. This paper presents the configuration of the DSC as an alternative internal cooling technology and explains its major physical phenomena, which are the reasons for the improvement of internal heat transfer.

A Novel Technique for Assessing Turbine Cooling System Performance

2009 ◽  
Author(s):  
S. Luque ◽  
T. Povey
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Steel Wire ◽  
Pressure Ratio ◽  
Wire Mesh ◽  
Coolant Temperature ◽  
Heating Process ◽  
Film Cooling Effectiveness ◽  
Turbine Vanes ◽  
Annular Sector

A new experimental technique for the accurate measurement of steady-state metal temperature surface distributions of modern heavily film-cooled turbine vanes has been developed and is described in this paper. The technique is analogous to the thermal paint test, but has been designed for fundamental research. The experimental facility consists of an annular sector cascade of HP turbine vanes from a current production engine. Flow conditioning is achieved by using an annular sector of deswirl vanes downstream of the test section, being both connected by a three-dimensionally contoured duct. As a result, a transonic and periodic flow, highly representative of the engine aerodynamic field, is established: inlet turbulence levels, mainstream Mach and Reynolds numbers, and coolant-to-mainstream total pressure ratio are matched. Since the fully three-dimensional NGV geometry is used, the correct radial pressure gradient and secondary flow development are simulated and the cooling flow redistribution is engine-realistic. To allow heat transfer measurements to be performed, a mainstream-to-coolant temperature difference (up to 33.5 °C) is generated by using two steel-wire mesh heaters, operated in series. NGV surface metal temperatures are measured (between 20 and 40 °C) by wide-band thermochromic liquid crystals. These are calibrated in situ and on a per-pixel basis against vane surface thermocouples, in a heating process that spans the entire colour play and during which the turbine vanes can be assumed to slowly follow a succession of isothermal states. Experimental surface distributions of metal effectiveness are presented in this paper. By employing resin vanes of the same geometry and cooling configuration (to implement adiabatic wall thermal boundary conditions) and the transient liquid crystal technique, surface distributions of external heat transfer coefficient and film cooling effectiveness will be acquired. By combining these measurements with those from the metal vanes, the results can be scaled to engine conditions with a good level of accuracy.

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.

Adiabatic Film Cooling Effectiveness From Heat Transfer Measurements in Compressible, Variable-Property Flow

1985 ◽  
Vol 107 (2) ◽  
pp. 313-320 ◽  
Author(s):  
P. M. Ligrani ◽  
C. Camci
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Velocity Ratio ◽  
Flux Ratio ◽  
Coolant Temperature ◽  
Transfer Coefficients ◽  
Constant Property ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Variable Property

A variable property correction is given for turbulent boundary layers that are film-cooled using staggered rows of injection holes inclined at 35 deg. With the correction, a relation is provided between the adiabatic film cooling effectiveness for constant property flow and heat transfer coefficients for variable property flow, which are based on the difference between the freestream recovery temperature and wall temperature. The variable property correction was determined from heat transfer measurements for a range of injection parameters at different values of the nondimensional coolant temperature and from results in the literature. Because the flow is compressible, the importance of the injection mass flux ratio, momentum flux ratio, and velocity ratio are considered in the determination of effectiveness.

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