Effects of Hole Pitch to Diameter Ratio P/D of Impingement and Film Hole on Laminated Cooling Effectiveness

2017 ◽  
Author(s):  
Weilun Zhou ◽  
Qinghua Deng ◽  
Wei He ◽  
Zhenping Feng
Keyword(s):  
Mass Flux ◽  
Pressure Loss ◽  
Pressure Ratio ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
System Pressure ◽  
The Difference

The laminated cooling, also known as impingement-effusion cooling, is believed to be a promising gas turbine blade cooling technique. In this paper, conjugate heat transfer analysis was employed to investigate the overall cooling effectiveness and total pressure loss of the laminated cooling configuration. The pitch to film hole diameter ratio P/Df of 3, 4, 5, 6, combined with pitch to impingement hole diameter ratio P/Di of 4, 6, 8, 10, are studied at the coolant mass flux G of 0.5, 1.0, 1.5, 2.0 kg/(sm2bar) respectively. The results show that overall cooling effectiveness of laminated cooling configuration increases with the decreasing of P/Df and the increasing of the coolant mass flux in general. However P/Df smaller than 3 may leads to a serious blocking in first few film holes at low coolant mass flux. The large P/Di that makes the Mach number of impingement flow greater than 0.16 may cause unacceptable pressure loss. The increment of overall cooling effectiveness depends on the difference between the deterioration of external cooling and the enhancement of internal cooling. Pressure loss increases exponentially with P/Di and G, and it increases more slowly with P/Df that compared to P/Di and G. The mixing loss takes up the most pressure loss at low coolant mass flux. With the increasing of the whole pressure loss, the proportion of throttling loss and laminated loss becomes larger and finally takes up the most of the whole pressure loss. When the sum of throttling loss and laminated loss is greater than mixing loss, the increment of system pressure ratio is unreasonable that compared to the increment of overall cooling effectiveness.

Conjugate Heat Transfer Analysis for Laminated Cooling Effectiveness: Part A — Effects of Surface Curvature

2016 ◽  
Author(s):  
Weilun Zhou ◽  
Qinghua Deng ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Film Cooling ◽  
Pressure Loss ◽  
Conjugate Heat Transfer ◽  
Convex Surface ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Blowing Ratio

The laminated cooling or multi-layered impingement-effusion cooling, which originates from combustor liner cooling, combines impingement jet, rib-roughed and film cooling and results in a high overall cooling effectiveness. It’s believed to be a promising gas turbine blade cooling technique. In this paper, conjugate heat transfer analysis that has been validated by the experimental results was carried out for five laminated cooling models with different surface curvatures at a certain range of blowing ratio. The numerical results show that the curvature and blowing ratio have crucial effects on laminated cooling effectiveness. High blowing ratio results in a better overall cooling effectiveness for flat plate and concave surface, while the moderate blowing ratio performances better on convex surface. Film cooling has an interaction with the internal convective and impingement cooling, thus the optimal cooling effectiveness of laminated cooling is achieved at the condition that the improvement of internal cooling counteracts the deterioration of film cooling, instead of the condition that film cooling or internal cooling reaches the maximum respectively. Moreover, concave surfaces have the higher pressure loss in the whole range of blowing ratio, while convex surfaces have lower pressure loss than flat plate due to the turbulence intensity of external flow.

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.

Effect of 45-Deg Rib Orientations on Heat Transfer in a Rotating Two-Pass Channel With Aspect Ratio From 4:1 to 2:1

2019 ◽  
Author(s):  
Izzet Sahin ◽  
Andrew F. Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Pressure Loss ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
First Passage

Abstract The internal cooling passages of gas turbine blades mostly have varying aspect ratios from one passage to another. However, there are limited data available in the open literature that used a reduced cross-section and aspect ratio, AR, after the tip turn. Therefore, the current study presents heat transfer and pressure drop of three different α = 45° profiled rib orientations, typical parallel (usual), reversed parallel (unusual), and criss-cross patterns in a rotating two-pass rectangular channel with AR = 4:1 and 2:1 in the first radially outward flow and second radially inward flow passages respectively. For each rib orientation, regional averaged heat transfer results are obtained for both the flow passages with the Reynolds number ranging from 10,000 to 70,000 for the first passage and 16000 to 114000 for the second passage with a rotational speed range of 0 rpm to 400 rpm. This results in the highest rotation number of 0.39 and 0.16 for the first and second passage respectively. The effects of rib orientation, aspect ratio variation, 180° tip turn, and rotation number on the heat transfer and pressure drop will be addressed. According to the results, for usual, unusual and criss-cross rib patterns, increasing rotation number causes the heat transfer to decrease on the leading surface and increase on the trailing surface for the first passage and vice versa for the second passage. Overall heat transfer enhancement of the usual and unusual rib patterns is higher than criss-cross one. In terms of the pressure losses, the criss-cross rib pattern has the lowest and the usual rib pattern has the highest-pressure loss coefficients. When pressure loss and heat transfer enhancement are both taken into account together, the criss-cross or unusual rib pattern might be an option to use in the internal cooling method. Therefore, the results can be useful for turbine blade internal cooling design and heat transfer analysis.

Total Cooling Effectiveness on Laminated Multilayer for Impingement/Effusion Cooling System

2014 ◽  
Author(s):  
Seon Ho Kim ◽  
Kyeong Hwan Ahn ◽  
Eui Yeop Jung ◽  
Jun Su Park ◽  
Ki-Young Hwang ◽  
...  
Keyword(s):  
Cooling System ◽  
Plate Thickness ◽  
Laminate Plate ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Single Plate ◽  
Line Array ◽  
Cooling Intensity

The next generation aircraft combustor liner will be operating in more severe conditions. This means that the current cooling system needs significant amounts of cooling air to maintain cooling intensity. The present study investigates experimentally the total cooling effectiveness of an integrated impingement/effusion cooling system (thin perforated laminate plate) and effusion cooling system (single plate) at the same blowing ratio of 0.2 to 1.2. The infrared thermography method was employed to evaluate total cooling effectiveness and to determine the fully developed region of cooling performance. The holes arrays on both plates are 13 × 13 and the centers formed a square pattern (i.e., an in-line array). The perforated laminate plate is constructed of three layers and pins that were installed between the layers. In order to avoid increasing the thickness and volume, the layer thickness-to-hole diameter ratio was 0.29, and the pin height-to-hole diameter ratio, which is equivalent to the gap between the plates, was 0.21. The single plate had the same total plate thickness-to-hole diameter, but was composed of only one layer. As a result, the total cooling effectiveness of the laminate plate is 47% ∼ 141% better than single plate depending on the blowing ratio. Also, a fully developed region appears on the 2nd or 3th row of holes.

Effect of 45-deg Rib Orientations on Heat Transfer in a Rotating Two-Pass Channel With Aspect Ratio from 4:1 to 2:1

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Izzet Sahin ◽  
Andrew F Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Pressure Loss ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
First Passage

Abstract The internal cooling passages of gas turbine blades mostly have varying aspect ratios from one passage to another. However, there are limited data available in the open literature that used a reduced cross section and aspect ratio (AR), after the tip turn. Therefore, the current study presents heat transfer and pressure drop of three different α = 45 deg profiled rib orientations, typical parallel (usual), reversed parallel (unusual), and crisscross patterns in a rotating two-pass rectangular channel with AR = 4:1 and 2:1 in the first radially outward flow and second radially inward flow passages, respectively. For each rib orientation, regional averaged heat transfer results are obtained for both the flow passages with the Reynolds number ranging from 10,000 to 70,000 for the first passage and 16,000 to 114,000 for the second passage with a rotational speed range of 0–400 rpm. This results in the highest rotation number of 0.39 and 0.16 for the first and second passage respectively. The effects of rib orientation, aspect ratio variation, 180-deg tip turn, and rotation number on the heat transfer and pressure drop will be addressed. According to the results, for usual, unusual and crisscross rib patterns, increasing rotation number causes the heat transfer to decrease on the leading surface and increase on the trailing surface for the first passage and vice versa for the second passage. The overall heat transfer enhancement of the usual and unusual rib patterns is higher than the crisscross one. In terms of the pressure losses, the crisscross rib pattern has the lowest and the usual rib pattern has the highest-pressure loss coefficients. When pressure loss and heat transfer enhancement are both taken into account together, the crisscross or unusual rib pattern might be an option to use in the internal cooling method. Therefore, the results can be useful for the turbine blade internal cooling design and heat transfer analysis.

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.

The Comparison of Two Species Film Cooling Characteristics Between Trenched and Shaped Holes

2008 ◽  
Author(s):  
D. H. Zhang ◽  
Q. Y. Chen ◽  
L. Sun ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Film Cooling ◽  
Volume Fraction ◽  
Aerodynamic Performance ◽  
Diameter Ratio ◽  
Vapor Film ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Shaped Hole ◽  
The Difference ◽  
Length To Diameter Ratio

The exit-shaped holes can result in lower coolant momentum injection with greater surface coverage. The exit-trenched holes can also lower the coolant momentum. Thus, the cooling and aerodynamic performance of laterally diffused shaped holes and laterally trenched holes were numerically compared with same depth and same hole length and the reasons for the difference were also analyzed from the viewpoint of flow mechanism. The both end-shaped holes and both end-trenched holes were also compared to the exit-shaped holes and exit-trenched holes respectively. Owing to the better heat transfer performance of steam than that of air, the cooling characteristics of super heated vapor film and pure air film were numerically investigated using the multi phase model of FLUENT to study the effect of different vapor volume fraction on film cooling characteristics. It appears that the shaped holes is superior to the trenched holes in cooling and aerodynamic performance for the cases in the present study; for shaped holes, the difference between the exit-shaped hole and both end-shaped hole is negligible; But for trenched holes, the cooling effectiveness of both end-trenched hole and the exit-trenched holes is heavily dependent on the hole length to diameter ratio; for shorter hole length to diameter ratio, the cooling effectiveness of both end-trenched hole is superior to that of exit-trenched hole. For all the cases studied, the mixture injectant is better than pure air coolant, and the mixture exhibits greater cooling advantage in the far downstream region of the holes than in the near hole region. The super heated vapor film can improve the film cooling effectiveness; the vapor volume fraction increased by 20%, and the area average cooling effectiveness can increase by 5%.

Fine Particulate Deposition in an Effusion Plate Geometry

2019 ◽  
Author(s):  
B. Varney ◽  
B. Barker ◽  
J. P. Bons ◽  
T. Wolff ◽  
P. Gnanaselvam
Keyword(s):  
Constant Pressure ◽  
Pressure Ratio ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Gas Turbine Combustor ◽  
Plate Temperature ◽  
Test Fixture ◽  
Fine Particulate ◽  
Inclination Angles ◽  
Compound Angle

Abstract Fine particulate deposition testing was conducted with an effusion plate film cooling geometry representative of a gas turbine combustor liner. Preheated coolant air with airborne particulate (0–10 μm Arizona Road Dust) was fed into an effusion plate test fixture with the flow parallel to the target plate. The test fixture was located in an electric kiln that establishes the elevated plate temperature, similar to a gas turbine combustor. Experiments were conducted at constant pressure ratio (1.03) across the effusion plate which consists of an array of approximately 100 effusion holes. Test variables include hole diameter, length/diameter ratio, inclination angle and compound angle. In addition, coolant temperature and plate temperature were varied independently to determine their influence on in-hole deposition. All tests were continued until the effusion holes had blocked to produce a 25% reduction in mass flow rate while maintaining constant pressure ratio. The blockage was found to be more sensitive to flow temperature than to plate temperature over the range studied. Blockage was insensitive to effusion hole diameter from 0.5 to 0.75 mm, but increased dramatically for hole diameter below 0.5mm. Blockage shows a moderate increase with hole length/diameter ratio. The strongest dependency was found with the inclination angle; roughly an order of magnitude increase in deposition rate was documented when increasing from a 30° to 150°. A compound angle of 45° caused a negligible change in blockage, while a compound angle of 90° increased blockage for low inclination angles while decreasing it for high inclination angles. For the flow angle dependency, interpretation is provided by means of CFD simulations of the particulate delivery and initial deposition location prediction using the OSU Deposition Model.

Experimental Study on the Cooling Performance of a Turbine Nozzle With an Innovative Internal Cooling Structure

2009 ◽  
Author(s):  
Shu Fujimoto ◽  
Yoji Okita ◽  
Chiyuki Nakamata
Keyword(s):  
Film Cooling ◽  
Pressure Loss ◽  
Performance Test ◽  
Internal Cooling ◽  
Basic Design ◽  
Design Data ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Conventional Cooling

An innovative cooling structure named multi-slot cooling was invented for high-pressure turbine (HPT) nozzles and blades. This cooling structure has been designed to be simple, inexpensive, and to exhibit good cooling performance. In a previous study (GT2008-50444), the basic design data on the cooling effectiveness and pressure loss coefficients for HPT cooling design were obtained by using simple test pieces. In this study, the cooling performance of the HPT nozzle with a multi-slotted cooling structure in a cascade was reported. First, the HPT nozzle with a multi-slotted cooling structure and its outer profile were selected; its cooling structure was designed by using the data in the previous study and trial-and-error method. Subsequently, ceramic casting cores and casting nozzles were manufactured by way of trial. Furthermore the cooling performance test for the multi-slotted cooling nozzle (TEST #1) in an annular sector cascade test rig was conducted, and the cooling effectiveness fields and pressure loss data were obtained. In addition, the measurement test for determining the heat transfer coefficient on the nozzle (TEST #2) and that for determining the film cooling effectiveness on the nozzle (TEST #3) were conducted. And then, cooling performance of the multi-slotted cooling nozzle was evaluated by using these data. As a result, for the typical configuration, it was confirmed that the basic design data obtained in the previous study are applicable to designing nozzles with multi-slot cooling by introducing a minor modification and the cooling performance of multi-slot cooling is equivalent to that of the conventional cooling under the test condition; consequently, it was confirmed that the multi-slot cooling is well applicable to the cooling of actual HPT airfoils except in the case that its configuration is significantly changed.

Conjugate Heat Transfer Analysis of Military Aero Engine Combustor Liner With Impingement and Effusion Cooling

2019 ◽  
Author(s):  
Batchu Suresh ◽  
Chinmayee Panigrahi ◽  
Antonio Davis ◽  
V. Kesavan ◽  
D. Kishore Prasad
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Hole Diameter ◽  
Heat Transfer Analysis ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Impingement Plate ◽  
Aero Engine ◽  
Combustor Liner

Abstract Improvement in specific thrust is one of the desirable requirements for Military aero-engine which has led to a tremendous increase in turbine inlet temperatures. This has resulted in combustion chambers to operate at a gas temperature of the order of 2100K, making it difficult for the thermal designers to design a liner cooling configuration to bring down its metal temperature within allowable limits with available coolant air. The present study highlights the computational prediction of cooling effectiveness for impingement-effusion cooled combustor liner. The impingement cooling is adopted to the effusion cooled liner in order to enhance its coolant side heat transfer. 1-Dimensional (1-D) analysis is carried out to obtain a suitable impingement geometry to improve the coolant side heat transfer. Suitable geometrical features like impingement hole diameter (di) and distance of the impingement plate from effusion liner (z) are arrived for enhancement of coolant side heat transfer. Conjugate Heat Transfer analysis (CHT) is carried out for three cooling configurations with different impingement hole diameter. Effusion cooled liner with porosity 1% and holes inclined at 22° and for impingement plate hole porosity of 1.6% is maintained for all the configurations. CHT analysis is carried out for effusion cooled liner using ANSYS Fluent ver.14.5. The film cooling predictions are in good agreement for effusion cooled liner plate with measurements. SST k-ω turbulence model with enhanced wall function predicted well. The effectiveness obtained for effusion cooled liner and impingement-effusion cooled liner are compared. There is an improvement of 34% in effectiveness for impingement-effusion cooled liner compared to effusion cooled liner with a reduction of coolant air mass flow by 10%. The variation of temperature for the impingement-effusion cooled liner is lower. Parametric analysis is also carried out to study the effect of blowing ratio and metal thermal conductivity on the film cooling effectiveness for impingement-effusion cooled liner.

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