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.

scholarly journals Full Coverage Discrete Hole Wall Cooling: Cooling Effectiveness

1984 ◽  
Author(s):  
G. E. Andrews ◽  
M. L. Gupta ◽  
M. C. Mkpadi
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Film Cooling ◽  
Test Facility ◽  
Coolant Temperature ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Full Coverage ◽  
Hole Wall

The development of a test facility for investigating full coverage discrete hole wall cooling for gas turbine combustion chamber wall cooling is described. A low temperature test condition of 750K mainstream temperature and 300K coolant temperature was used to investigate the influence of coolant flow rate at a constant cross flow Mach number. Practical combustion conditions of 2100K combustor temperature and 700K coolant temperature are investigated to establish the validity of applying the low temperature results to practical conditions. For both situations a heat balance programme, taking into account the heat transfer within the wall was used to compute the film heat transfer coefficients. The mixing of the coolant air with the mainstream gases was studied through boundary layer temperature and CO2 profiles. It was shown that entrainment of hot flame gases between the injection holes resulted in a very low ‘adiabatic’ film cooling effectiveness.

Heat Transfer Coefficients and Film Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade

2003 ◽  
Vol 125 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Rotor Blade ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio

Experimental investigations were performed to measure the detailed heat transfer coefficients and film cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film cooling holes on the pressure side near the tip region and the tip surface along the camber line. Hue detection based transient liquid crystals technique was used to measure heat transfer coefficients and film cooling effectiveness. All measurements were done for the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.9 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.

Effect of Internal Crossflow Velocity on Film Cooling Effectiveness: Part II — Compound Angle Shaped Holes

2017 ◽  
Author(s):  
John W. McClintic ◽  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary D. Webster
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Cooling ◽  
Velocity Ratio ◽  
Injection Rate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Crossflow Velocity ◽  
Film Cooling Holes ◽  
Compound Angle

In gas turbine engines, film cooling holes are commonly fed with an internal crossflow, the magnitude of which has been shown to have a notable effect on film cooling effectiveness. In Part I of this study, as well as in a few previous studies, the magnitude of internal crossflow velocity was shown to have a substantial effect on film cooling effectiveness of axial shaped holes. There is, however, almost no data available in the literature that shows how internal crossflow affects compound angle shaped film cooling holes. In Part II, film cooling effectiveness, heat transfer coefficient augmentation, and discharge coefficients were measured for a single row of compound angle shaped film cooling holes fed by internal crossflow flowing both in-line and counter to the span-wise direction of coolant injection. The crossflow-to-mainstream velocity ratio was varied from 0.2–0.6 and the injection velocity ratio was varied from 0.2–1.7. It was found that increasing the magnitude of the crossflow velocity generally caused degradation of the film cooling effectiveness, especially for in-line crossflow. An analysis of jet characteristic parameters demonstrated the importance of crossflow effects relative to the effect of varying the film cooling injection rate. Heat transfer coefficient augmentation was found to be primarily dependent on injection rate, although for in-line crossflow, increasing crossflow velocity significantly increased augmentation for certain conditions.

Prediction of Film Cooling Effectiveness and Heat Transfer due to Streamwise and Compound Angle Injection on Flat Surfaces

1995 ◽  
Author(s):  
S. Neelakantan ◽  
M. E. Crawford
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Momentum Flux ◽  
Flux Ratio ◽  
Equation Model ◽  
Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Flat Surfaces ◽  
Momentum Flux Ratio ◽  
Density Ratios

The distributed Yavuzkurt injection model is extended to predict the effectiveness and heat transfer coefficients for film cooling injection from a single row of holes, aligned both along the direction of the freestream and at an angle with it. The injection angles were 24° and 35°. The compound angles considered were 50.5° and 60°. The Yavuzkurt film cooling model is used in conjunction with a one-equation model to yield the effectiveness and heat transfer predictions. The density ratios considered were 1.6 and 0.95 for the effectiveness predictions and 1.0 and 0.95 for the heat transfer predictions. For the effectiveness predictions, the blowing ratios range from 0.5 to 2.5, and the momentum flux ratios from 0.16 until 3.9. The hole spacings were 3, 6, and 7.8 hole diameters. The Yavuzkurt model constants are seen to be definitely correlated with the momentum flux ratio. Correlations for the model constants are obtained in terms of the momentum flux ratio. For the heat transfer predictions, the blowing ratios ranged from 0.4 to 2.0, and the momentum flux ratios from 0.16 to 3.9. The spacing between the holes was 3, 6, and 7.8 hole diameters. The matching between the effectiveness correlations and the heat transfer predictions is done on the basis of the momentum flux ratio. Results indicate that the Yavuzkurt model predictions are best for the in-line round holes. Heat transfer predictions are close to the experimental results for lower blowing ratios, until the ratio exceeds 1. For higher blowing ratios, the predictions, though less accurate, follow the experimental trends.

scholarly journals Aspects of Vane Film Cooling With High Turbulence: Part I — Heat Transfer

1997 ◽  
Author(s):  
Forrest E. Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Large Scale ◽  
Velocity Ratio ◽  
Transfer Coefficients ◽  
Suction Surface ◽  
Stagnation Region ◽  
Film Cooling Effectiveness ◽  
High Turbulence

A four vane subsonic cascade was used to investigate the influence of film injection on vane heat transfer distributions in the presence of high turbulence. The influence of high turbulence on vane film cooling effectiveness and boundary layer development was also examined in part II of this paper. A high level, large scale inlet turbulence was generated for this study with a mock combustor (12 %) and was used to contrast results with a low level (1 %) of inlet turbulence. The three geometries chosen to study in this investigation were one row and two staggered rows of downstream cooling on both the suction and pressure surfaces in addition to a showerhead array. Film cooling was found to have only a moderate influence on the heat transfer coefficients downstream from arrays on the suction surface where the boundary layer was turbulent. However, film cooling was found to have a substantial influence on heat transfer downstream from arrays in laminar regions of the vane such as the pressure surface, the stagnation region, and the near suction surface. Generally, heat transfer augmentation was found to scale on velocity ratio. In relative terms, the augmentation in the laminar regions for the low turbulence case was found to be higher than the augmentation for the high turbulence case. The absolute levels of heat transfer were always found to be the highest for the high turbulence case.

Heat Transfer and Film Cooling on a Contoured Blade Endwall With Platform Gap Leakage

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Vortical Flow ◽  
Leakage Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Manufacturing Assembly

Turbine blade components in an engine are typically designed with gaps between parts due to manufacturing, assembly, and operational considerations. Coolant is provided to these gaps to limit the ingestion of hot combustion gases. The interaction of the gaps, their leakage flows, and the complex vortical flow at the endwall of a turbine blade can significantly impact endwall heat transfer coefficients and the effectiveness of the leakage flow in providing localized cooling. In particular, a platform gap through the passage, representing the mating interface between adjacent blades in a wheel, has been shown to have a significant effect. Other important turbine blade features present in the engine environment are nonaxisymmetric contouring of the endwall, and an upstream rim seal with a gaspath cavity, which can reduce and increase endwall vortical flow, respectively. To understand the platform gap leakage effect in this environment, measurements of endwall heat transfer, and film cooling effectiveness were performed in a scaled blade cascade with a nonaxisymmetric contour in the passage. A rim seal with a cavity, representing the overlap interface between a stator and rotor, was included upstream of the blades and a nominal purge flowrate of 0.75% of the mainstream was supplied to the rim seal. The results indicated that the endwall heat transfer coefficients increased as the platform gap net leakage increased from 0% to 0.6% of the mainstream flowrate, but net heat flux to the endwall was reduced due to high cooling effectiveness of the leakage flow.

Comparison of Film Effectiveness and Cooling Uniformity of Conical and Cylindrical-Shaped Film Hole With Coolant-Exit Temperature Correction

2010 ◽  
Author(s):  
Cuong Q. Nguyen ◽  
Perry L. Johnson ◽  
Bryan C. Bernier ◽  
Son H. Ho ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Temperature Correction ◽  
Coolant Temperature ◽  
Transfer Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Film Cooling Holes

Data from conical-shaped film cooling holes is extremely sparse in open literature, especially the cooling uniformity characteristic, an important criterion for evaluating any film cooling design. The authors will compare the performance of conical-shaped holes to cylindrical-shaped holes. Cylindrical-shaped holes are often considered a baseline in terms of film cooling effectiveness and cooling uniformity coefficient. The authors will study two coupons with conical-shaped holes, which have 3° and 6° diffusion angles, named CON3 and CON6 respectively. A conjugate heat transfer computational fluid dynamics model and an experimental wind tunnel will be used to study these coupons. The three configurations: cylindrical baseline, CON3, and CON6, have a single row of holes with an inlet metering diameter of 3mm, length-to-nominal diameter of 4.3, and an injection angle of 30°. In this study, the authors will also take into account the heat transfer into the coolant flow from the coolant channel. In other words, coolant temperature at the exit of the coolant hole will be different than that measured at the inlet, and the conjugate heat transfer model will be used to correct for this difference. For the numerical model, the realizable k-ε turbulent model will be applied with a second order of discretization and enhanced wall treatment to provide the highest accuracy available. Grid independent studies for both cylindrical-shaped film cooling holes and conical-shaped holes will be performed and the results will be compared to data in open literature as well as in-house experimental data. Results show that conical-shaped holes considerably outperform cylindrical-shaped holes in film cooling effectiveness at all blowing ratios. In terms of cooling uniformity, conical-shaped holes perform better than cylindrical-shaped holes for low and mid-range blowing ratios, but not at higher levels.

Effect of Surface Roughness on Local Heat Transfer and Film Cooling Effectiveness

1995 ◽  
Author(s):  
Douglas N. Barlow ◽  
Yong W. Kim
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Smooth Surface ◽  
Rough Surfaces ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients

An experimental investigation of film cooling on rough surfaces has been accomplished at a Reynolds number and dimensionless boundary layer momentum thickness found in current high performance first stage turbine vanes. A transient experimental method using thermochromic liquid crystals is employed to determine both local heat transfer coefficients and film cooling effectiveness values on planar rough surfaces. Two surface roughness configurations are investigated with a single row of cooling holes spaced three diameters apart and inclined 30° to the mainstream flow. The mainstream turbulence level at the point of film injection is 8.5% and the density ratio considered is approximately 1.0. The influence of roughness on the centerline film cooling effectiveness, laterally averaged film cooling effectiveness, laterally averaged heat transfer coefficients, as well as area averaged values are presented. It is found that the presence of roughness causes a decrease in the film cooling effectiveness over that of the smooth surface for the range of experimental parameters considered in this study. In addition, significant lateral smoothing in film cooling effectiveness distribution is observed for the rougher surfaces. Measured heat transfer coefficients on rough surfaces show a trend of monotonic increase with blowing ratio. However, such increase is not as great as that for the case of smooth surface.

Numerical Prediction of Film Cooling and Heat Transfer With Different Film-Hole Arrangements on the Plane and Squealer Tip of a Gas Turbine Blade

2004 ◽  
Author(s):  
Huitao Yang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Heat ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Tip Leakage ◽  
High Heat Transfer

The blade tip is one area that experiences high heat transfer due to the strong tip leakage flow. One of the common methods is to apply film cooling on tip to reduce the heat load. To get a better film cooling, different arrangements of film holes on the plane and squealer tips have been numerically studied with the Reynolds stress turbulence model and non-equilibrium wall function. The present study investigated three types of film-hole arrangements: 1) the camber arrangement: the film cooling holes are located on the mid-camber line of tips, 2) the upstream arrangement: the film holes are located upstream of the tip leakage flow and high heat transfer region, and 3) two rows arrangement: the camber and upstream arrangements are combined under the same amount of coolant. In addition, three different blowing ratios (M = 0.5, 1 and 1.5), are evaluated for film cooling effectiveness and heat transfer coefficient. The predicted heat transfer coefficients are in good agreement with the experimental data, but the film cooling effectiveness is over predicted on the blade tips.

Film Cooling From a Row of Holes With Both Ends Embedded in Transverse Slots

2008 ◽  
Author(s):  
D. H. Zhang ◽  
L. Sun ◽  
Q. Y. Chen ◽  
M. Lin ◽  
M. Zeng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Aerodynamic Performance ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Discharge Coefficients ◽  
Cylindrical Holes

Embedding a row of typical cylindrical holes in a transverse slot can improve the cooling performance. Rectangular slots can increase the cooling effectiveness but is at the cost of decreasing of discharge coefficients. An experiment is conducted to examine the effects of an overlying transverse inclined trench on the film cooling performance of axial holes. Four different trench configurations are tested including the baseline inclined cylindrical holes. The influence of the geometry of the upstream lip of the exit trench and the geometry of the inlet trench on cooling performance is examined. Detailed film cooling effectiveness and heat transfer coefficients are obtained separately using the steady state IR thermography technique. The discharge coefficients are also acquired to evaluate the aerodynamic performance of different hole configurations. The results show that the film cooling holes with both ends embedded in slots can provide higher film cooling effectiveness and lower heat transfer coefficients; it also can provide higher discharge coefficients whilst retaining the mechanical strength of a row of discrete holes. The cooling performance and the aerodynamic performance of the holes with both ends embedded in inclined slots are superior to the holes with only exit trenched. To a certain extent, the configuration of the upstream lip of the exit trench affects the cooling performance of the downstream of the trench. The filleting for the film hole inlet avail the improvement of the cooling effect, but not for the film hole outlet. Comparing film cooling with embedded holes to unembedded holes, the overall heat flux ratio shows that the film holes with both ends embedded in slots and filleting for the film hole inlet can produce the highest heat flux reduction.

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