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.

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.

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.

Conjugate Heat Transfer Predictions of Effusion Cooling: The Influence of the Coolant Jet-Flow Direction on the Cooling Effectiveness

2012 ◽  
Author(s):  
H. I. Oguntade ◽  
G. E. Andrews ◽  
A. D. Burns ◽  
D. B. Ingham ◽  
M. Pourkashanian
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Flow ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Unexpected Result ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hot Gas

Effusion cooling of a flat wall was investigated using conjugate heat transfer CFD. The main variable investigated was the angle of the coolant jets relative to the crossflow. Experimental data for the overall cooling effectiveness using a metal effusion cooled wall was modelled for an X/D of 4.65, coolant to crossflow density ratio of 2.56, ten rows of holes in the crossflow direction and a blowing ratio M of 0.2–3.27 or mass flow per surface area, G, of 0.088–1.47 kg/sm2. The experimental data for 90° normal injection was modelled and then the influence of injecting each effusion hole 30° downstream and 150° downstream (or 30° upstream) was predicted. The coupled thermal mixing between the hot-gas and coolant jets and the heat transfer within the effusion walls were modelled using the ANSYS FLUENT code. The computational results of the overall cooling effectiveness of the validation case was of the order of about 8–12% less than the experimental data but the trend of the results was well predicted. A methane tracer gas was added to the coolant air and this enabled the adiabatic cooling effectiveness to be predicted as well as the overall cooling effectiveness. At high blowing ratios, the co-flow inclined and normal jets were characterised with kidney-shaped pair vortices which degrade the adiabatic film cooling effectiveness. The counteraction of the fluid dynamics between the oppose-flow jets and hot-gas momentum prevents the formation of the kidney-shaped pair vortices with the usage of opposed-flow wall. The oppose-flow jet was shown to be the best effusion cooling design with the greatest transverse spread of the film cooling at high blowing ratios. This was an unexpected result that has very few previous studies. The results show that significant reductions in coolant mass flow rate for the same wall temperature could be achieved or lower wall temperatures for the same coolant mass flow.

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 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 Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig, which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10–10–10 deg laidback fan-shaped cooling hole is discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near-hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

Measurement of Local Heat Transfer Coefficient and Film Cooling Effectiveness Through Discrete Holes

2000 ◽  
Author(s):  
R. F. Martinez-Botas ◽  
C. H. N. Yuen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Local Heat Transfer ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

An efficient steady-state wide band liquid crystal technique is used to study the film cooling performance of a variety of geometries in a flat plate: a single row of holes, a double row of holes (both in-line and staggered), and a single cooling hole. This method allows temperature information to be captured in one image, without the difficulty involved in a transient experiment. The streamwise inclinations tested are 30°, 60°, and 90°. The freestream is maintained at 13m/s, and at ambient temperature. The range of blowing ratios varied from 0.33 to 2.0. Both heat transfer coefficient and adiabatic cooling effectiveness are measured for all the cases. Air is used to produce a density ratio near unity. From the range of blowing ratios tested, the most effective film cooling is achieved at a value close to 0.5, for near unity density ratio. It has been revealed that film cooling effectiveness is improved when the jet remains attached to the surface, however, this is generally coupled with an augmentation in heat transfer owing to the disturbance the attached jet causes to the boundary layer. The 30° inclined holes show to be the most effective. Results demonstrate the full coverage capability of liquid crystal thermography.

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.

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.

scholarly journals Effects on Heat Transfer Coefficient and Adiabatic Effectiveness in Combined Backside and Film Cooling With Short-Hole Geometry

2019 ◽  
Author(s):  
Renzo La Rosa ◽  
Jaideep Pandit ◽  
Wing Ng ◽  
Brett Barker
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Transfer Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Adiabatic Effectiveness

Abstract Heat transfer experiments were done on a flat plate to study the effect of internal counter-flow backside cooling on adiabatic film cooling effectiveness and heat transfer coefficient. In addition, the effects of density ratio (DR), blowing ratio (BR), diagonal length over diameter (L/D) ratio, and Reynolds number were studied using this new configuration. The results are compared to a conventional plenum fed case. Data were collected up to X/D = 23 where X = 0 at the holes, an S/D = 1.65 and L/D = 1 and 2. Testing was done at low L/D ratios since short holes are normally found in double wall cooling applications in turbine components. A DR of 2 was used in order to simulate engine-like conditions and this was compared to a DR of 0.92 since relevant research is done at similar low DR. The BR range of 0.5 to 1.5 was chosen to simulate turbine conditions as well. In addition, previous research shows that peak effectiveness is found within this range. Infrared (IR) thermography was used to capture temperature contours on the surface of interest and the images were calibrated using a thermocouple and data analyzed through MATLAB software. A heated secondary fluid was used as ‘coolant’ in the present study. A steady state heat transfer model was used to perform the data reduction procedure. Results show that backside cooling configuration has a higher adiabatic film cooling effectiveness when compared to plenum fed configurations at the same conditions. In addition, the trend for effectiveness with varying BR is reversed when compared with traditional plenum fed cases. Yarn flow visualization tests show that flow exiting the holes in the backside cooling configuration is significantly different when compared to flow exiting the plenum fed holes. We hypothesize that backside cooling configuration has flow exiting the holes in various directions, including laterally, and behaving similar to slot film cooling, explaining the differences in trends. Increasing DR at constant BR shows an increase in adiabatic effectiveness and HTC in both backside cooling and plenum fed configurations due to the decreased momentum of the coolant, making film attachment to the surface more probable. The effects of L/D ratio in this study were negligible since both ratios used were small. This shows that the coolant flow is still underdeveloped at both L/D ratios. The study also showed that increasing turbulence through increasing Reynolds number decreased adiabatic effectiveness.

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