Predicting the Adiabatic Effectiveness of Effusion Cooling by the Convolution Modeling Method

2019 ◽  
Author(s):  
Li Yang ◽  
Yu Rao
Keyword(s):  
Gas Turbines ◽  
Thermal Load ◽  
Turbine Blades ◽  
Computational Time ◽  
Cooling Effectiveness ◽  
Proposed Model ◽  
Convolution Model ◽  
Adiabatic Cooling ◽  
Cooling Hole ◽  
Random Manner

Abstract Effusion Cooling has a strong potential in protecting hot section components of gas turbines engines such as turbine blades, endwalls and combustor liners. By carefully distributing the cooling holes adaptively to the external thermal load, effusion cooling can dramatically reduce the temperature and thermal stress for the protected components. However, the effectiveness for effusion cooling was not easy to correlate due to the numerous parameters to study and the significant variation from the upstream to the downstream. Conventional equations used in the literature were insufficient to express the complex mechanism for effusion cooling and consequently utilized averaged parameters as variables. This study proposed a convolution method to model the local adiabatic cooling effectiveness for the entire effusion cooled surfaces. The new model treated the cooling hole distribution as an input matrix and applied convolution networks to predict the cooling effectiveness. Compared with conventional correlations, this network based model provided extensive details of the cooling effectiveness distribution while consuming computational time as short as correlations. Training of the proposed model was based on the numerical simulation results of three geometries and the validation was conducted for two additional geometries. Results indicated high accuracy and high robustness of the convolution model. With the aid of this novel model, further designing could adjust hole distribution in a random manner instead of using rows and columns, and generate adaptive effusion cooling based on thermal load.

Implementation of Hole-Pair in Ramp to Improve Film Cooling Effectiveness on a Plain Surface

2020 ◽  
Author(s):  
Sadam Hussain ◽  
Xin Yan
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Density Ratio ◽  
Hole Pair ◽  
Cooling Effect ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Plain Surface

Abstract Film cooling is one of the most critical technologies in modern gas turbine engine to protect the high temperature components from erosion. It allows gas turbines to operate above the thermal limits of blade materials by providing the protective cooling film layer on outer surfaces of blade against hot gases. To get a higher film cooling effect on plain surface, current study proposes a novel strategy with the implementation of hole-pair into ramp. To gain the film cooling effectiveness on the plain surface, RANS equations combined with k-ω turbulence model were solved with the commercial CFD solver ANSYS CFX11.0. In the numerical simulations, the density ratio (DR) is fixed at 1.6, and the film cooling effect on plain surface with different configurations (i.e. with only cooling hole, with only ramp, and with hole-pair in ramp) were numerically investigated at three blowing ratios M = 0.25, 0.5, and 0.75. The results show that the configuration with Hole-Pair in Ramp (HPR) upstream the cooling hole has a positive effect on film cooling enhancement on plain surface, especially along the spanwise direction. Compared with the baseline configuration, i.e. plain surface with cylindrical hole, the laterally-averaged film cooling effectiveness on plain surface with HPR is increased by 18%, while the laterally-averaged film cooling effectiveness on plain surface with only ramp is increased by 8% at M = 0.5. As the blowing ratio M increases from 0.25 to 0.75, the laterally-averaged film cooling effectiveness on plain surface with HPR is kept on increasing. At higher blowing ratio M = 0.75, film cooling effectiveness on plain surface with HPR is about 19% higher than the configuration with only ramp.

Performance of Public Film Cooling Geometries Produced Through Additive Manufacturing

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Jacob C. Snyder ◽  
Karen A. Thole
Keyword(s):  
Additive Manufacturing ◽  
Film Cooling ◽  
Gas Turbines ◽  
Nickel Alloys ◽  
Cooling Effectiveness ◽  
Powder Bed ◽  
The Public ◽  
Hot Gas ◽  
Cooling Hole ◽  
Cooling Technology

Abstract Film cooling is an essential cooling technology to allow modern gas turbines to operate at high temperatures. For years, researchers in this community have worked to improve the effectiveness of film cooling configurations by maximizing the coolant coverage and minimizing the heat flux from the hot gas into the part. Working toward this goal has generated many promising film cooling concepts with unique shapes and configurations. However, until recently, many of these designs were challenging to manufacture in actual turbine hardware due to limitations with legacy manufacturing methods. Now, with the advances in additive manufacturing, it is possible to create turbine parts using high-temperature nickel alloys that feature detailed and unique geometry features. Armed with this new manufacturing power, this study aims to build and test the promising designs from the public literature that were previously difficult or impossible to implement. In this study, different cooling hole designs were manufactured in test coupons using a laser powder bed fusion process. Each nickel alloy coupon featured a single row of engine scale cooling holes, fed by a microchannel. To evaluate performance, the overall cooling effectiveness of each coupon was measured using a matched Biot test at engine relevant conditions. The results showed that certain hole shapes are better suited for additive manufacturing than others and that the manufacturing process can cause significant deviations from the performance reported in the literature.

Effects of Surface Deposition, Hole Blockage, and Thermal Barrier Coating Spallation on Vane Endwall Film Cooling

2006 ◽  
Vol 129 (3) ◽  
pp. 599-607 ◽  
Author(s):  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Thermal Barrier Coating ◽  
Film Cooling ◽  
Gas Turbines ◽  
Large Scale ◽  
Leading Edge ◽  
Thermal Barrier ◽  
Cooling Effectiveness ◽  
Barrier Coating ◽  
Cooling Hole ◽  
Alternate Fuels

With the increase in usage of gas turbines for power generation and given that natural gas resources continue to be depleted, it has become increasingly important to search for alternate fuels. One source of alternate fuels is coal derived synthetic fuels. Coal derived fuels, however, contain traces of ash and other contaminants that can deposit on vane and turbine surfaces affecting their heat transfer through reduced film cooling. The endwall of a first stage vane is one such region that can be susceptible to depositions from these contaminants. This study uses a large-scale turbine vane cascade in which the following effects on film cooling adiabatic effectiveness were investigated in the endwall region: the effect of near-hole deposition, the effect of partial film cooling hole blockage, and the effect of spallation of a thermal barrier coating. The results indicated that deposits near the hole exit can sometimes improve the cooling effectiveness at the leading edge, but with increased deposition heights the cooling deteriorates. Partial hole blockage studies revealed that the cooling effectiveness deteriorates with increases in the number of blocked holes. Spallation studies showed that for a spalled endwall surface downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio.

Conjugate Simulation of the Effects of Oxide Formation in Effusion Cooling Holes on Cooling Effectiveness

2009 ◽  
Author(s):  
Dieter Bohn ◽  
Robert Krewinkel
Keyword(s):  
Gas Turbines ◽  
Power Plants ◽  
Gas Flow ◽  
Combined Cycle ◽  
Reference Case ◽  
Flow Area ◽  
Cooling Effectiveness ◽  
Hot Gas ◽  
Barrier Coating ◽  
Cooling Hole

Within Collaborative Research Center 561 “Thermally Highly Loaded, Porous and Cooled Multi-Layer Systems for Combined Cycle Power Plants” at RWTH Aachen University an effusion-cooled multi-layer plate configuration with seven staggered effusion cooling holes is investigated numerically by application of a 3-D in-house fluid flow and heat transfer solver, CHTflow. The effusion-cooling is realized by finest drilled holes with a diameter of 0.2 mm that are shaped in the region of the thermal barrier coating. Oxidation studies within SFB 561 have shown that a corrosion layer of several oxides with a thickness of appoximately 20μm grows from the CMSX-4 substrate into the cooling hole. The goal of this work is to investigate the effect this has on the cooling effectiveness, which has to be quantified prior to application of this novel cooling technology in real gas turbines. In order to do this, the influence on the aerodynamics of the flow in the hole, on the hot gas flow and the cooling effectiveness on the surface and in the substrate layer are discussed. The adverse effects of corrosion on the mechanical strength are not a part of this study. A hot gas Mach-number of 0.25 and blowing ratios of approximately 0.28 and 0.48 are considered. The numerical grid contains the coolant supply (plenum), the solid body for the conjugate calculations and the main flow area on the plate. It is shown that the oxidation layer does significantly affect the flow field in the cooling holes and on the plate, but the cooling effectiveness differs only slightly from the reference case. This seems to justify modelling the holes without taking account of the oxidation.

Effects of Surface Deposition, Hole Blockage, and TBC Spallation on Vane Endwall Film-Cooling

2006 ◽  
Author(s):  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Large Scale ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Barrier Coating ◽  
Cooling Hole ◽  
Endwall Film Cooling ◽  
Alternate Fuels

With the increase in usage of gas turbines for power generation and given that natural gas resources continue to be depleted, it has become increasingly important to search for alternate fuels. One source of alternate fuels is coal derived synthetic fuels. Coal derived fuels, however, contain traces of ash and other contaminants that can deposit on vane and turbine surfaces affecting their heat transfer through reduced film-cooling. The endwall of a first stage vane is one such region that can be susceptible to depositions from these contaminants. This study uses a large-scale turbine vane cascade in which the following effects on film-cooling adiabatic effectiveness were investigated in the endwall region: the effect of near-hole deposition, the effect of partial film-cooling hole blockage, and the effect of spallation of a thermal barrier coating. The results indicated that deposits near the hole exit can sometimes improve the cooling effectiveness at the leading edge, but with increased deposition heights the cooling deteriorates. Partial hole blockage studies revealed that the cooling effectiveness deteriorates with increases in the number of blocked holes. Spallation studies showed that for a spalled endwall surface downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio.

Effect of the In-Hole Vortical Structures on the Cylindrical-Hole Film-Cooling Effectiveness

2020 ◽  
Author(s):  
Shubham Agarwal ◽  
Laurent Gicquel ◽  
Florent Duchaine ◽  
Nicolas Odier ◽  
Jérôme Dombard
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Hairpin Vortices ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Vortical Structures ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Control Film ◽  
Cooling Hole

Abstract Understanding the flow from a cooling hole is very important to be able to properly control film cooling of turbine blades. For this purpose, large eddy simulation (LES) investigation of the flow inside a cylindrical film cooling hole is presented in this paper. Two different geometries, with different hole metering lengths, are investigated at a blowing ratio of 0.5. The main flow structure in the hole are the hairpin vortices that originate from a shear layer formed due to flow separation near the hole entry. The comparison of these hairpin vortices in the two cases with different hole metering length is presented in detail. The results show that in case of the hole with longer length the hairpin vortices dissociate within the hole itself. In such a case a uniform flow is seen at the hole exit. However, when the hole length is significantly decreased, it is shown that these vortices exit the hole and effect the vortex structures outside the hole, thereby accounting for the reduction in film cooling effectiveness. Overall, these results bring forth one other major reason for the reduction in film cooling effectiveness with reduction in hole length, i.e. the exit of in-hole hairpin vortices into the crossflow.

Parametric Study on Anti-Vortex Film Cooling Hole Arrangements

2014 ◽  
Vol 660 ◽  
pp. 664-668
Author(s):  
Kamil Abdullah ◽  
Hazim Fadli Aminnuddin ◽  
Akmal Nizam Mohammed
Keyword(s):  
Film Cooling ◽  
Thermal Protection ◽  
Turbine Blades ◽  
Vortex Pair ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Lateral Film ◽  
Lift Off

Film cooling has been extensively used to provide thermal protection for the external surface of the gas turbine blades. Numerous number of film cooling holes designs and arrangements have been introduced. The main motivation of these designs and arrangements are to reduce the lift-off effect cause by the counter rotating vortices (CRVP) produce by cylindrical cooling hole. One of the efforts is the introduction of newly found anti-vortex film cooling design. The present study focuses on anti-vortex holes arrangement consists of a main hole and pair of smaller holes. All three holes share a common inlet with the outlet of the smaller holes varies base on it relative position towards the main hole. Three anti-vortex holes arrangements have been considered; downstream anti-vortex hole arrangement (DAV), lateral anti-vortex hole arrangement (LAV), and upstream anti-vortex hole arrangement (UAV). In addition, a single hole (SH) film cooling has also been considered as the baseline. The investigation make used of ANSYS CFX software ver. 14. The investigations are made through Reynolds Average Navier Stokes analyses with the application of shear k-ε turbulence model. The results show that the anti-vortex designs produce significant improvement in term of film cooling effectiveness and distribution. The LAV arrangement shows the best film cooling effectiveness distribution among all considered cases and is consistent for all blowing ratios (BR). The results also unveil the formation of new vortex pair on both side of the primary hole CRVP. Interaction between the new vortices and the main CRVP structure reduce the lift off explaining the increased lateral film effectiveness.

Recent Advances in the Study of High Efficiency Novel Film Cooling Holes

2013 ◽  
Vol 740 ◽  
pp. 830-835
Author(s):  
Ping Dai ◽  
Nai Yun Yu
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
High Efficiency ◽  
Turbine Blades ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
New Generation ◽  
Film Cooling Holes ◽  
Air Film

The development of a new generation of high performance aircraft turbine jet engine desires gas turbines to be operated at very high rotor inlet gas temperatures. This brings a problem on the effective cooling of turbine blades. Up to now, modified film cooling is still an effective cooling technique. The influence of air-film hole structures on the air-film cooling efficiency cant be ignored. A survey of the research results concerning novel air-film cooling hole about home and abroad were given and high efficiency crescent air-film hole geometry was put forward. Through a comparative study of film cooling characteristic with cylindrical air-film hole and forward diffused air-film hole and crescent air-film hole found effectiveness of the crescent air-film hole was superior to other air-film holes in various blowing ratios. The crescent air-film hole could greatly reduce the kidney vortex intensity, and then enhanced the air-film cooling effectiveness.

CFD Simulations for Film Cooling Holes: Comparison Between Different Isotropic and Anisotropic Eddy Viscosity Models

2018 ◽  
Author(s):  
Jens Dickhoff ◽  
Karsten Kusterer ◽  
Santhosh Kumar Bhaskar ◽  
Dieter Bohn
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Constitutive Relations ◽  
Turbulence Models ◽  
Lateral Direction ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Acceptable Accuracy ◽  
Cooling Hole

In modern gas turbines, film cooling technology is essential for the protection of hot parts. Today, shaped holes are widely used, but besides others, the NEKOMIMI-shaped cooling holes have shown that there is still potential to increase the film cooling effectiveness significantly by generation of Anti-Counter-Rotating Vortices (ACRV). Within the past decade, the technology has been improved step by step at B&B-AGEMA and Kawasaki Heavy Industries Ltd.; mainly by means of numerical simulations. The laterally averaged film cooling effectiveness is typically captured with acceptable accuracy, but the experimental measurements still show a deviation from the numerically obtained results with respect to the local film cooling effectiveness distribution behind the film cooling hole. Nevertheless, the film cooling air spread out in the lateral direction is one of the keys for enhancement of the film cooling performance. Thus, more precise simulations are consequently necessary for improvement of the hole shape configuration. The present study involves simulations of a baseline fan shaped hole configuration (“777 hole” investigated by Schroeder and Thole [1][2]) using different turbulence models available in STAR-CCM+ with isotropic and anisotropic turbulence consideration (constitutive relations). Distinct differences with respect to flow phenomena (detachments and vortex creation) can be observed depending on the applied turbulence model. In total, the results show that anisotropic viscosity strongly influences the film cooling performance prediction by CFD for prediction of the film cooling effectiveness, but none of the models provides acceptable accuracy in this regard.

Enhanced Film Cooling Effectiveness With New Shaped Holes

2010 ◽  
Author(s):  
Jong S. Liu ◽  
Malak F. Malak ◽  
Luis A. Tapia ◽  
Daniel C. Crites ◽  
Dhinagaran Ramachandran ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Area Ratio ◽  
Heat Fluxes ◽  
Geometrical Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hot Gas ◽  
Ansys Cfx ◽  
Cooling Hole

Gas Turbine Engines operate at temperatures higher than current material temperature limits. This necessitates cooling the metal through internal or external means and/ or protecting the metal with coatings that have higher material limits. Film cooling is one of the major technologies allowing today’s gas turbines to operate at extremely high turbine inlet temperatures, consequently higher power density, and extend the cooled components life. Film cooling is a technique where a coolant is blown over the surface exposed to hot gas and a film of low temperature gas is maintained that protects the metal surface from the hot gas. The application of effective film-cooling techniques provides the first and best line of defense for hot gas path surfaces against the onslaught of extreme heat fluxes, serving to directly reduce the incident convective heat flux on the surface. The effectiveness of film cooling methods depends on the blowing ratio, shape of the cooling holes, and geometrical parameters such as the area ratio and diffusion angle. Film cooling is performed almost exclusively through the use of discrete holes. The holes can be of round or other shaped. A detailed study of the literature shows that the fan shaped has higher effectiveness when compared to other shapes. In this study a number of cooling hole shapes are evaluated numerically using the Computational Fluid Dynamics (CFD) tool ANSYS-CFX-11.0 with the objective of improving cooling effectiveness under a favorable pressure gradient main flow. In order to delineate the effects of shape from that of diffusion, a constant area ratio is assumed first. In the next set of analyses the effect of hole exit diffusion is considered. Results are presented in terms of surface temperatures and adiabatic effectiveness at three different blowing ratios for the different film cooling hole shapes analyzed. Comparison is made with reference to the fan shaped film cooling hole with forward and lateral angles of 10/10/10 degree respectively. Hole shapes that show improvement over the fan shaped hole are identified and optimized.

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