Derivation of 2-D Empirical Correlations for Film-Cooling Effectiveness and Heat Transfer Augmentation From Spanwise Averaged Data and Correlations

2013 ◽  
Author(s):  
Peter T. Ingram ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Heat Transfer Augmentation ◽  
Cylindrical Holes ◽  
Compound Angle

In existing gas turbine heat transfer literature, there are several correlations developed for the spanwise-averaged film-cooling effectiveness and heat transfer augmentation for inline injection on flat plates. More accurate and detailed predictions of film-cooling performance, particularly 3-D solid temperatures are needed for design purposes. 2-D correlations where effectiveness and heat transfer augmentation are functions of streamwise and spanwise directions are necessary to satisfy this need. Previously developed 2-D correlations for single row of cylindrical holes with inline injection have been improved to include the effects of shaped holes such as hole breakthrough width (t/D) and area ratio (AR). The correlations are improved to better match spanwise effectiveness of a single row of shaped cooling holes using data and spanwise-averaged correlations. Modifications to the correlations to improve application to compound injection (β) have been implemented. The blowing ratio is modified to account for the compound angle effect. The spanwise location of maximum film-cooling effectiveness and heat transfer augmentation are obtained as functions of the streamwise coordinate. Iterative Conjugate Heat Transfer Reduced Order Film Model (ICHT-ROFM) was used to obtain 3-D conjugate temperature distribution in film cooled solids. The developed correlations predicted a relative cooling effect in the near hole region for shaped holes (24 K) and for compound angle injection (20K) compared to cylindrical holes. Spanwise variations in the solid temperature in the near hole region are between 40–50K for a temperature difference of 250K between the surface and the main stream and are quite significant, showing the need for 3-D simulations. Shaped and compound angle holes increase this temperature difference due to the increased cooling. The comparisons of solid temperatures for conjugate and non-conjugate heat transfer cases show about 13–18K or 8–10% of the local temperature difference of 180K. Therefore it can be concluded that the calculations of 3-D temperature distributions using conjugate heat transfer are very important for design purposes.

Calculation of 3-D Temperature Distribution in Film-Cooled Flat Plates Using 2-D Empirical Correlations for Film-Cooling Effectiveness and Heat Transfer Augmentation

2012 ◽  
Author(s):  
Peter T. Ingram ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Flat Plates ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Temperature Study ◽  
Heat Transfer Augmentation

In existing gas turbine heat transfer literature there are several correlations developed for the spanwise-averaged film-cooling effectiveness and heat transfer augmentation for inline injection on flat plates. More accurate and detailed prediction of film-cooling performance, particularly 3-D metal temperatures are needed for design purposes. 2-D correlations where effectiveness and heat transfer augmentation are functions of streamwise and spanwise directions would help to satisfy this need. Based on this fact, the current study extends the spanwise-averaged correlations into 2-D correlations by using a Gaussian distribution in the transverse direction. The correlations are obtained using limited spanwise data and more available spanwise-averaged data and existing spanwise-averaged correlations for a single row of holes with inline injection. These correlations presented in this paper are functions of different flow parameters such as mass flow ratio M, density ratio DR, transverse pitch P/D, and inline injection angle α, with ranges of M:0.2–2.5, DR: 1.2,1.5,1.8, P/D: 2, 3,5, α: 30, 60, 90 degrees. The developed correlations match existing spanwise-averaged correlations when averaged. These correlations are used to calculate solid flat plate temperatures for two well-documented cases of film-cooled flat plates. Spanwise variations in the metal temperature were calculated to be between 5–6K for a temperature difference of 40K and between 20–30K for a temperature difference of 250K, significant for design purposes. The study also contains the comparison of solid temperatures for conjugate and non-conjugate heat transfer cases using a Reduced Order Film Model (ROFM) which is implemented in a loosely coupled conjugate heat transfer technique called Iterative Conjugate Heat Transfer (ICHT)).The differences between conjugate and non conjugate simulations are about 6K or 2% of the local temperature for low temperature study and about 20K or 5% for high temperature study. The study showed that the difference between conjugate and non-conjugate solutions increases as the temperature levels increase. These differences are quite important and should be taken into account during design of turbine blades.

Experimental and Numerical Film Effectiveness Downstream a Row of Compound Angle Film Holes

2003 ◽  
Author(s):  
A. Khanicheh ◽  
M. E. Taslim
Keyword(s):  
High Temperature ◽  
Film Cooling ◽  
Computational Study ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Film Cooling Holes ◽  
Compound Angle

High component lifetimes of modern gas turbines can be achieved by cooling the airfoils effectively. Film cooling is commonly employed on the airfoils and other engine hot section surfaces in order to protect them from the high thermal stress fields created by exposure to combustion gases. Complex geometries as well as optimized cooling considerations often dictate the use of compound-angled film cooling hole. In the present experimental and computational study, the effects that two different compound angle film cooling hole injection configurations have on film cooling effectiveness are investigated. Film cooling effectiveness measurements have been made downstream of a single row of compound angle cylindrical holes with a diameter of 7.5 mm, and a single row of compound angle, diffuser-shaped holes with an inlet diameter of 7.5 mm. The cylindrical holes were inclined (α=25°) with respect to the coverage surface and were oriented perpendicular to the high-temperature airflow direction. The diffuser-shaped holes had a compound angle of 45 degrees with respect to the high temperature air flow direction and, similar to the cylindrical film holes, a 25-deg angle with the coverage surface. Both geometries were tested over a blowing ratio range of 0.7 to 4.0. Surface temperatures were measured along four longitudinal rows of thermocouples covering the downstream area between two adjacent holes. The results showed that the best overall protection over the widest range of blowing ratios was provided by the diffuser-shaped film cooling holes. Compared with the cylindrical hole results, the diffuser-shaped expansion holes produced higher film cooling effectiveness downstream of the film cooling holes, particularly at high blowing ratios. The increased cross sectional area at the shaped hole exit compared to that of the cylindrical hole lead to a reduction of the mean velocity, thus the reduction of the momentum flux of the jet exiting the hole. Therefore, the penetration of the jet into the main flow was reduced, resulting in an increased cooling effectiveness. A commercially available CFD software package was used to study film cooling effectiveness downstream of the row of holes. Comparisons between the experimentally measured and numerically calculated film effectiveness distributions showed that the computed results are in reasonable agreement with the measured results. Therefore, CFD can be considered as a viable tool to predict the cooling performance of different film cooling configurations in a parametric study. A more realistic turbulence model, possibly adopting a two-layer model that incorporates boundary layer anisotropy, in the computational study may improve the predicted results.

Film Effectiveness Downstream of a Row of Compound Angle Film Holes

2005 ◽  
Vol 127 (4) ◽  
pp. 434-440 ◽  
Author(s):  
M. E. Taslim and ◽  
A. Khanicheh
Keyword(s):  
High Temperature ◽  
Film Cooling ◽  
Flow Direction ◽  
Cross Sectional ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Cylindrical Holes ◽  
Cfd Analyses ◽  
Compound Angle

Effects that two different compound-angle film-hole configurations have on film cooling effectiveness are investigated. Effectiveness measurements have been made downstream of a single row of compound-angle cylindrical holes with a diameter of 7.5 mm, and a single row of compound-angle, diffuser-shaped holes with an inlet diameter of 7.5 mm. Both geometries were inclined with respect to the coverage surface at an angle α of 25 deg. The cylindrical holes, however, were oriented perpendicular to the high-temperature airflow direction while the diffuser-shaped holes had a compound angle of 45 deg with respect to the high temperature air flow direction. Both geometries were tested over a blowing ratio range of 0.7 to 4.0 Surface temperatures were measured along four longitudinal rows of thermocouples covering the downstream area between two adjacent holes. The results showed that the best overall protection over the widest range of blowing ratios was provided by the diffuser-shaped film cooling holes, particularly at high blowing ratios. The increased cross-sectional area at the shaped hole exit lead to a reduction of the momentum flux of the jet exiting the hole. Therefore, the penetration of the jet into the main flow was reduced, resulting in an increased cooling effectiveness. CFD analyses were also performed to study the film cooling effectiveness downstream of the row of holes. Comparisons between the test and numerical results showed a reasonable agreement between the two, thus CFD can be considered a viable tool to predict the cooling performance of different film cooling configurations in a parametric study.

A Superposition Technique for Multiple-Row Film-Cooling for Calculation of 2-D Effectiveness and Heat Transfer Coefficients

2015 ◽  
Author(s):  
Peter T. Ingram ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Reduced Order ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Augmentation ◽  
Superposition Technique

A superposition technique for multiple-row film-cooling heat-transfer augmentation and effectiveness is investigated. The technique is developed for use with 2-D correlations of film-cooling properties such as film cooling effectiveness and heat transfer coefficients. The method proposed is for implementations with Iterative Conjugate Heat-Transfer using a Reduced Order Film Model (ICHT-ROFM). The superposition technique is used in conjunction with 2-D correlations developed in a previous study for single row of holes to obtain the heat transfer augmentation and film-cooling effectiveness for two staggered rows for dustpan shaped holes. The results are compared to data for multiple-row film-cooling. The results for effectiveness were within 15% of empirical data. The results obtained from using the current technique are compared to spanwise-averaged superposition techniques, which had errors nearing 50%, and it was found to be more accurate.

Conjugate Heat Transfer and Film Cooling of a Multi-Stage Cooling Scheme

2008 ◽  
Author(s):  
M. Ghorab ◽  
S. I. Kim ◽  
I. Hassan
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Design Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Multi Stage ◽  
Internal Gap

Cooling techniques play a key role in improving efficiency and power output of modern gas turbines. The conjugate technique of film and impingement cooling schemes is considered in this study. The Multi-Stage Cooling Scheme (MSCS) involves coolant passing from inside to outside turbine blade through two stages. The first stage; the coolant passes through first hole to internal gap where the impinging jet cools the external layer of the blade. Finally, the coolant passes through the internal gap to the second hole which has specific designed geometry for external film cooling. The effect of design parameters, such as, offset distance between two-stage holes, gap height, and inclination angle of the first hole, on upstream conjugate heat transfer rate and downstream film cooling effectiveness performance are investigated computationally. An Inconel 617 alloy with variable properties is selected for the solid material. The conjugate heat transfer and film cooling characteristics of MSCS are analyzed across blowing ratios of Br = 1 and 2 for density ratio, 2. This study presents upstream wall temperature distributions due to conjugate heat transfer for different gap design parameters. The maximum film cooling effectiveness with upstream conjugate heat transfer is less than adiabatic film cooling effectiveness by 24–34%. However, the full coverage of cooling effectiveness in spanwise direction can be obtained using internal cooling with conjugate heat transfer, whereas adiabatic film cooling effectiveness has narrow distribution.

Influence of Coolant Density on Turbine Platform Film-Cooling With Stator–Rotor Purge Flow and Compound-Angle Holes

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Kevin Liu ◽  
Shang-Feng Yang ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Fundamental Parameters ◽  
Blowing Ratio ◽  
Purge Flow ◽  
Cylindrical Holes ◽  
Exit Mach Number ◽  
Compound Angle

A detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform. The platform was cooled by purge flow from a simulated stator–rotor seal combined with discrete hole film-cooling. The cylindrical holes and laidback fan-shaped holes were accessed in terms of film-cooling effectiveness. This paper focuses on the effect of coolant-to-mainstream density ratio on platform film-cooling (DR = 1 to 2). Other fundamental parameters were also examined in this study—a fixed purge flow of 0.5%, three discrete-hole film-cooling blowing ratios between 1.0 and 2.0, and two freestream turbulence intensities of 4.2% and 10.5%. Experiments were done in a five-blade linear cascade with inlet and exit Mach number of 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 750,000 and was based on the exit velocity and chord length of the blade. The measurement technique adopted was the conduction-free pressure sensitive paint (PSP) technique. Results indicated that with the same density ratio, shaped holes present higher film-cooling effectiveness and wider film coverage than the cylindrical holes, particularly at higher blowing ratios. The optimum blowing ratio of 1.5 exists for the cylindrical holes, whereas the effectiveness for the shaped holes increases with an increase of blowing ratio. Results also indicate that the platform film-cooling effectiveness increases with density ratio but decreases with turbulence intensity.

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.

Effect of Density Ratio on Film-Cooling Effectiveness Distribution and Its Uniformity for Several Hole Geometries on a Flat Plate

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Jiaxu Yao ◽  
Jin Xu ◽  
Ke Zhang ◽  
Jiang Lei ◽  
Lesley M. Wright
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spread ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
Density Ratios ◽  
Compound Angle

The film cooling effectiveness distribution and its uniformity downstream of a row of film cooling holes on a flat plate are investigated by pressure sensitive paint (PSP) under different density ratios. Several hole geometries are studied, including streamwise cylindrical holes, compound-angled cylindrical holes, streamwise fan-shape holes, compound-angled fan-shape holes, and double-jet film-cooling (DJFC) holes. All of them have an inclination angle (θ) of 35 deg. The compound angle (β) is 45 deg. The fan-shape holes have a 10 deg expansion in the spanwise direction. For a fair comparison, the pitch is kept as 4d for the cylindrical and the fan-shape holes, and 8d for the DJFC holes. The uniformity of effectiveness distribution is described by a new parameter (Lateral-Uniformity, LU) defined in this paper. The effects of density ratios (DR = 1.0, 1.5 and 2.5) on the film-cooling effectiveness and its uniformity are focused. Differences among geometries and effects of blowing ratios (M = 0.5, 1.0, 1.5, and 2.0) are also considered. The results show that at higher density ratios, the lateral spread of the discrete-hole geometries (i.e., the cylindrical and the fan-shape holes) is enhanced, while the DJFC holes is more advantageous in film-cooling effectiveness. Mostly, a higher lateral-uniformity is obtained at DR = 2.5 due to better coolant coverage and enhanced lateral spread, but the effects of the density ratio on the lateral-uniformity are not monotonic in some cases. Utilizing the compound angle configuration leads to an increased lateral-uniformity due to a stronger spanwise motion of the jet. Generally, with a higher blowing ratio, the lateral-uniformity of the discrete-hole geometries decreases due to narrower traces, while that of the DJFC holes increases due to a stronger spanwise movement.

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.

Influence of Two Rows Compound and Simple Angle Holes in Inline and/or Staggered on Film Cooling and Heat Transfer

2005 ◽  
Author(s):  
Bilal Y. Maiteh
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Film Cooling ◽  
Pressure Gradients ◽  
Heat Transfer Characteristics ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Mainstream Flow ◽  
Favorable Pressure Gradient ◽  
Compound Angle

This paper describes the results of an experimental investigation into the effect of the mainstream flow history on the film cooling effectiveness and the heat transfer characteristics from the combination of one row of simple angle holes and one row of compound angle holes. The mainstream flow history includes: favorable pressure gradient factors in the range −1.11 × 10−6 to +1.11 × 10−6 and turbulence intensity in the range 0.3% to 4.7%. The presence of favorable pressure gradients in the flow reduces the film cooling protection of the surfaces from both compound angle holes or combination of simple and compound angle holes, while the presence of adverse pressure gradients increases the film cooling effectiveness at low blowing rate and decreases it at high blowing rate. Increasing the turbulence intensity reduces the film cooling effectiveness from compound angle holes or combination of simple and compound angle holes.

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