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.

Performance of Public Film Cooling Geometries Produced Through Additive Manufacturing

2019 ◽  
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 towards 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 micro-channel. 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 literature.

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.

Highest-Efficient Film Cooling by Improved NEKOMIMI Film Cooling Holes: Part 2 — Hot Gas Flow Conditions

2013 ◽  
Author(s):  
Karsten Kusterer ◽  
Nurettin Tekin ◽  
Azadeh Kasiri ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Gas Flow ◽  
Flow Conditions ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hot Gas ◽  
High Efficient ◽  
Cooling Technology ◽  
Cooling Air

In modern gas turbines, the film cooling technology is essential for the protection of the hot parts, in particular of the first stage vanes and blades of the turbine, against the hot gases from the combustion process in order to reach an acceptable life span of the components. As the cooling air is usually extracted from the compressor, the reduction of the cooling effort would directly result to an increased thermal efficiency of the gas turbine. Understanding of the fundamental physics of film cooling is necessary for the improvement of the state-of-the-art. Thus, huge research efforts by industry as well as research organizations have been undertaken to establish high efficient film cooling technologies. It is common knowledge today that film cooling effectiveness degradation is caused by secondary flows inside the cooling jets, i.e. the Counter-Rotating Vortices (CRV) or sometimes also mentioned as kidney-vortices, which induce a lift-off of the jet. Further understanding of the secondary flow development inside the jet and how this could be influenced, has led to hole configurations, which can induce Anti-counter-rotating Vortices (ACRV) in the cooling jets. As a result, the cooling air remains close to the wall and is additionally distributed flatly along the surface. Beside different other technologies, the NEKOMIMI cooling technology is a promising approach to establish the desired ACRV. It consists of a combination of two holes in just one configuration so that the air is distributed mainly on two cooling air streaks following the special shape of the generated geometry. The original configuration was found to be difficult for fabrication by advanced machining processes. Thus, the improvement of this configuration has been reached by a set of geometry parameters, which lead to configurations easier to be manufactured but preserving the principle of the NEKOMIMI technology. Within a numerical parametric study several advanced configurations have been obtained and investigated under hot gas flow conditions. By systematic variation of the parameters a further optimization with respect to highest film cooling effectiveness has been performed. The best configuration outperforms the basic configuration by more than 20% regarding the overall averaged adiabatic film cooling effectiveness.

Experimental and Numerical Investigations of the NEKOMIMI Film Cooling Technology

2012 ◽  
Author(s):  
Karsten Kusterer ◽  
Nurettin Tekin ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
Ryozo Tanaka ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Film Cooling ◽  
Gas Turbines ◽  
Mixing Processes ◽  
Cooling Effectiveness ◽  
Numerical Investigations ◽  
Hot Gas ◽  
Cooling Technology ◽  
Lift Off ◽  
Cooling Air

The improvement of the thermal efficiency of modern gas turbines can be achieved by reducing the required cooling air amount. Therefore, it is necessary to increase the cooling effectiveness, so that the available cooling air fulfils the cooling task even if the amount has been reduced. Due to experimental and numerical efforts, it is well understood today that aerodynamic mixing processes are enhanced by counter rotating vortices (CRV) in the cooling jets and lead to jet liftoff effects. Novel film cooling technologies focus on establishing anti-counter-rotating-vortices (ACRV) inside the cooling jet that prevent the hot gas from flowing underneath the jet and, thus, avoid the lift-off effect. One of these technologies is the NEKOMIMI film cooling, which is derived from the original double-jet film cooling (DJFC).

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.

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.

Highest-Efficient Film Cooling by Improved NEKOMIMI Film Cooling Holes: Part 1 — Ambient Air Flow Conditions

2013 ◽  
Author(s):  
Karsten Kusterer ◽  
Nurettin Tekin ◽  
Frederieke Reiners ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Air Flow ◽  
Ambient Air ◽  
Flow Conditions ◽  
Test Rig ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Technology ◽  
Cooling Air

In modern gas turbines, the film cooling technology is essential for the protection of the hot parts, in particular of the first stage vanes and blades of the turbine, against the hot gases from the combustion process in order to reach an acceptable life span of the components. As the cooling air is usually extracted from the compressor, the reduction of the cooling effort would directly result to an increased thermal efficiency of the gas turbine. Understanding of the fundamental physics of film cooling is necessary for the improvement of the state-of-the-art. Thus, huge research efforts by industry as well as research organizations have been undertaken to establish high efficient film cooling technologies. It is a today common knowledge that film cooling effectiveness degradation is caused by secondary flows inside the cooling jets, i.e. the Counter-Rotating Vortices (CRV) or sometimes also mentioned as kidney-vortices, which induce a lift-off of the jet. Further understanding of the secondary flow development inside the jet and how this could be influenced, has led to hole configurations, which can induce Anti-Counter-Rotating Vortices (ACRV) in the cooling jets. As a result, the cooling air remains close to the wall and is additionally distributed flatly along the surface. Beside different other technologies, the NEKOMIMI cooling technology is a promising approach to establish the desired ACRV. It consists of a combination of two holes in just one configuration so that the air is distributed mainly on two cooling air streaks following the special shape of the generated geometry. The original configuration was found to be difficult for manufacturing even by advanced manufacturing processes. Thus, the improvement of this configuration has been reached by a set of geometry parameters, which lead to configurations much easier to be manufactured but preserving the principle of the NEKOMIMI technology. Within a numerical parametric study several advanced configurations have been obtained and investigated under ambient air flow conditions similar to conditions for a wind tunnel test rig. By systematic variation of the parameters a further optimization with respect to highest film cooling effectiveness has been performed. A set of most promising configurations has been also investigated experimentally in the test rig. The best configuration outperforms the basic configuration by 17% regarding the overall averaged adiabatic film cooling effectiveness under the experimental conditions.

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.

Robust Optimization of the HPT Blade Cooling and Aerodynamic Efficiency

2016 ◽  
Author(s):  
Kirill A. Vinogradov ◽  
Gennady V. Kretinin ◽  
Kseniya V. Otryahina ◽  
Roman A. Didenko ◽  
Dmitry V. Karelin ◽  
...  
Keyword(s):  
Robust Optimization ◽  
Gas Turbine ◽  
Film Cooling ◽  
Gas Turbines ◽  
Leading Edge ◽  
Operational Parameters ◽  
Cooling Effectiveness ◽  
Aerodynamic Efficiency ◽  
Hot Gas ◽  
Blade Tip

Constant rise of hot gas temperature is crucial for the creation of modern gas-turbines engines requiring considerable improvement of cooling configurations. A high pressure turbine blade is one of the most crucial and loaded details in gas-turbine engines. A HPT blade is affected by different operational deviations: stochastic fluctuations of inlet parameters and difference in operational parameters for manufactured engines. Combination of these factors makes the task of uncertainty quantification and robust optimization of the HPT blade relevant in modern science. The authors make an attempt to implement robust optimization to the HPT blade of the gas-turbine engine. The two most important areas of the cooling blade (the leading edge (LE) and the blade tip) were taken into account. The operational and the aleatoric uncertainties were analyzed. These uncertainties represent the fluctuations in the operational parameters and the random-unknown conditions such as the boundary values and or geometrical variations. Industrial HPT blade with a serpentary cooling system and film cooling at the LE was considered. Results of many engine tests were applied to construct probability density function distributions for operational uncertainties. More than 100 real gas-turbines were examined. The following operational uncertainties were reviewed: inlet hot gas pressure and temperature together with cooling air pressure. The tip gap was used as geometrical variation. Conjugate Heat Transfer computations were carried out for the temperature distribution obtained. Geometrical variations of the LE film cooling rows and the tip gap are variables in the robust optimization process. The authors developed a special technology for full parameterization of the LE film-cooling rows only by two parameters. A surrogate model technique (the response surface and the Monte-Carlo method) was applied for the uncertainty quantification and the robust optimization processes. The IOSO technology was employed as one of the robust optimization tools. This technology is also based on the widespread application of the response surface technique. Robust optimal solution (the Pareto set) between cooling effectiveness of the leading edge and the blade tip and aerodynamic efficiency was obtained as the result. At chosen point from the Pareto set (angle point) we calculated necessary levels of robust criteria characterized LE and blade tip cooling effectiveness and kinetic energy losses.

Double-Jet Ejection of Cooling Air for Improved Film-Cooling

2006 ◽  
Author(s):  
Karsten Kusterer ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
Ryozo Tanaka
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Gas Flow ◽  
Operating Conditions ◽  
Cooling Effectiveness ◽  
Equal Distribution ◽  
Cooling Fluid ◽  
Film Cooling Effectiveness ◽  
Conventional Film ◽  
Cooling Technology

Film-cooling in gas turbines leads to aerodynamic mixing losses and reduced temperatures of the gas flow. Improvements of the gas turbine thermal efficiency can be achieved by reducing the cooling fluid amount and by establishing a more equal distribution of the cooling fluid along the surface. It is well known that vortex systems in the cooling jets are the origin of reduced film-cooling effectiveness. For the streamwise ejection case, kidney-vortices result in a lift-off of the cooling jets; for the lateral ejection case, usually only one dominating vortex remains, leading to hot gas flow underneath the jet from one side. Based on the results of numerical analyses, a new cooling technology has been introduced by the authors, which reaches high film-cooling effectiveness as a result of a well-designed cooling hole arrangement for interaction of two neighbouring cooling jets (Double-jet Film-cooling DJFC). The results show that configurations exist, where an improved film-cooling effectiveness can be reached because an anti-kidney vortex pair is established in the double-jet. The paper aims on following major contributions: • to introduce the Double-jet Film-cooling (DJFC) as an alternative film-cooling technology to conventional film-cooling design. • to explain the major phenomena, which lead to the improvement of the film-cooling effectiveness by application of the DJFC. • to prove basic applicability of the DJFC to a realistic blade cooling configuration and present first test results under machine operating conditions.

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