Author: Thomas Corbett Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The additive manufacturing (AM) process opens up many opportunities for engineers to explore novel cooling designs that historically may have been costly or even impossible to manufacture. To leverage AM for cooling schemes effectively, engineers must first understand the impact of AM surface roughness on the performance of a variety of internal geometries. The goal of this dissertation was to assess a suite of cooling technologies that were made using AM by comparing the fluid dynamic and heat transfer performance as well as the ability to construct the designs. Specifically, the cooling schemes investigated included wavy channels, pin fin arrays, lattice structures, broken wavy ribs, and diamond pyramid surface features. All of these features were evaluated over a wide range of Reynolds numbers in the turbulent flow regime. The cooling schemes evaluated covered a range of friction factor augmentations from 2 to 500, and heat transfer augmentations between 1.2 and 6 relative to smooth cylindrical channels with no features. The heat transfer and pressure drop of wavy channels was found to be largely a function of the secondary flows with the augmentation scaling as a function of the relative waviness of the channel. Wavy channels were also identified to perform best, in terms of heat transfer, at low Reynolds numbers. Pin fin geometries induced greater heat transfer and pressure loss augmentations than the wavy channels as result of the enhanced surface area and turbulent mixing. Pin shape and spacings were the variables that dictated the pressure loss and heat transfer, though the addition of surface roughness enhanced both flow characteristics. Small surface protrusions such as diamond pyramid turbulators and broken wavy ribs had small performance augmentations relative to the pin fin and wavy channel designs, but these augmentations were found to be insensitive to Reynolds number. The surface features induced substantial near wall mixing with increases in both heat transfer and pressure loss but was further increased as the relative endwall surface roughness increased. Lattice structures had the most significant pressure penalty of all geometries that were considered despite offering only similar heat transfer enhancement to that of the pin fin arrays. Throughout these studies, variations in materials and machines used for the additive manufacturing were identified and related to the performance of internal cooling and pressure loss. These variations led to varying degrees of roughness and a range of surface morphologies. Highly rough wavy channels, for example, significantly increased pressure drop but did not produce an equivalent increase to heat transfer. While arithmetic mean roughness was the primary driver of cooling performance, the surface skewness and kurtosis were found to be key secondary variables. The work presented in this dissertation identified the key flow characteristics and impacts of surface roughness on a variety of internal cooling designs. The data and analyses presented bridge the gap in understanding the performance implications of a range of additively manufactured cooling features empowering designers to integrate new cooling technologies into practical applications.
Author: Alexander Wildgoose Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The opportunities for additive manufacturing (AM) methods to create novel cooling schemes has garnered significant attention by the heat transfer community, in particular the gas turbine field. Using AM to fabricate complicated gas turbine parts under load, such as blades and vanes, is challenging in high temperature environments due to creep strength relative to traditionally casted components. Instead, the additive process allows for the rapid prototyping of advanced cooling components, such as vanes and blades, during the component development phase because of the added design freedom relative to cast components. To unlock the full potential of metal AM for rapid prototyping of advance cooling schemes, such as vanes, a better understanding of the impact the build process has on the build quality and cooling performance of internal features (cooling passages) and external features (film cooling holes and airfoil shape) are essential. The work in this dissertation explores the impact AM build considerations have on the cooling performance and geometric tolerances of internal passages as well as the external build quality of an engine relevant turbine guide vane. A multitude of cooling channel coupons were fabricated using AM with varying build directions, locations on the build plate, channel sizes, cross-sectional channel shapes, and wall thicknesses. Geometric tolerances and surface roughness of the cooling passages were analyzed using computed tomography scanning. The roughness, specifically the arithmetic mean roughness, of the internal passages exponentially increases at build directions from 60° to 0° (horizontal). Increasing the radial distance of the cooling passage from the laser source led to a 35% increase in roughness when moving the part from a radial distance of 0 mm to 145 mm. The arithmetic mean surface roughness did not change with channel size for build directions between 90° and 45°. Changes to the cross-sectional shape of a channel caused nonuniformity in roughness between surfaces as a result of differences in wall thickness. At wall thicknesses below 0.6 mm the surface roughness of the cooling passage increases, which is an important factor to consider since internal passages in turbine components contain a wide range of wall thicknesses. The surface roughness varied by 10% from part to part for multiple cooling passages printed on a build plate with the same radial location, build direction, and design intent. Surface roughness impacts the overall cooling performance of internal passages. To quantify these effects, an experimental rig was used to characterize the pressure loss and convective heat transfer performance of the various cooling coupons fabricated. Surface roughness was found to be linked to the friction factor of the coupons. Similar to roughness, the friction factor nonlinearly increased at build directions below 60°, while Nusselt number peaked between 30° and 45°. Increasing the radial distance of a part from the laser source caused an increase to the friction factor and Nusselt number. The difference in cooling performance for cooling coupons printed multiple times at a shared radial build location of 112.5 mm was 18% for friction factor and 5% for Nusselt number. Changes to the cross-sectional shape of a channel caused differences in secondary flows to have as much as a 31% difference in friction factor and 13% difference in Nusselt number. As result of the difference in surface roughness between channel shapes, there was no difference in scaling friction factor or Nusselt number when using the characteristic length scale of square root of cross-sectional area compared to hydraulic diameter. Using the cooling performance results from the different build considerations, a correlation was created that reduced the error in predicting friction factor and Nusselt number by half compared to correlations in literature. Using the created correlation, friction factor is able to be predicted within a maximum error of 25% and Nusselt number to within a maximum error of 39% regardless of changes to material or AM build parameters. The build quality of more complicated curved surfaces, specifically the external features of a vane (film cooling holes and airfoil shape) was characterized using a combination of CT scanning and optical profilometry. More specifically, an engine scale vane was fabricated at different build directions, locations on the build plate, and layer thicknesses. The differences in local surface orientations of a vane airfoil can result in variations in surface quality (as much as a 300% difference in surface roughness) between the suction side and pressure side. Orientating the geometric leading edge of the vane to a 120° build direction results in the lowest amount of surface quality variation between the pressure side and suction side. At the same 120° leading edge orientation, the first-row film cooling holes were found to be closest to their design intent relative to other vane orientations. Surface roughness increased 39% at the leading edge of a vane airfoil when increasing the radial location of 75 mm to 112.5 mm. Changes to the layer thickness from 80 microns to 40 microns increased the surface roughness of the pressure side and suction side. The work completed as part of this dissertation provides the foundational component design and AM build considerations needed for the AM process to be used as rapid prototyping in the development of advanced cooling designs, such as gas turbine components.
Author: Emma Veley Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Cooling of the high-pressure turbine in a gas turbine engine is essential for durability because the gas temperature entering the turbine exceeds the melting point of the hardware. Both internal and external cooling reduces the temperature of the blades and vanes. Using air that bypassed the combustor as coolant, the convective heat transfer from the hardware to this internal coolant is often augmented by ribs or a serpentine path. To cool the external surface, coolant passes through holes on the outer wall of airfoil. The coolant creates a protective film on the surface. The shape of the cooling hole influences the cooling effectiveness of this film cooling. Additive manufacturing facilitates rapid prototyping compared to traditional manufacturing methods, which can be exploited for designing and evaluating cooling schemes of gas turbine hardware. The work in this dissertation used additive manufacturing to investigate the cooling performance of several internal and external cooling schemes manufactured in at engine scale for the unique objective of determining the impacts of the internal cooling scheme on the external cooling. A variety of cooling hole shapes were investigated for this work: cylindrical hoes, meter-diffuser shaped holes, and novel optimized holes. Once additively manufactured, the as-built cooling hole surfaces were analyzed to determined their roughness and minimum cross-sectional areas. The arithmetic mean roughness of holes built at the optimal build orientation (perpendicular to the build plate) were on the order of 10 [mu]m; whereas those investigated at other build orientations had roughness values up to 75 [mu]m. For the holes built perpendicular to the substrate the minimum cross-sectional area was usually greater than the design intent but within 15%. The additive process also created an overbuilt lip on the leading edge (windward) side of the hole exit for these holes because of the thin wall thickness in the design. Using these cooling holes, the impact of rounding on meter-diffuser shaped holes and optimized holes on overall effectiveness was investigated. The rounding, which came in the form of inlet fillets on the meter-diffuser shaped holes, was found to decrease the required pressure ratio to obtain the same cooling effectiveness. The deviations from the design due to the additive process caused the novel cooling hole shapes designed through adjoint optimization to perform differently than anticipated. For example, the coolant jet from hole designed for co-flow did not bifurcate as the computational simulation showed. The cross-flow optimized hole outperformed the co-flow optimized hole for most of the tested blowing ratio when both holes were tested in a co-flow configuration. These results from the novel optimized holes proved the necessity of experimentally verifying new designs prior to incorporating into final cooling schemes. The effect of supply channel height, number of channels, ribs, and the cross-sectional shape of the supply channel was investigated to determine the impact of each on the overall effectiveness. Designs that had high overall effectiveness from only internal cooling had less augmentation in effectiveness from film cooling than designs with less effective internal cooling. For example, a ribbed channel typically had a lower film-cooling augmentation than the film-cooling augmentation for same supply channel without ribs. However, a highly effective feed channel can obtain a higher overall effectiveness without any film cooling than a poorly performing feed channel can obtain with film cooling. But the features that create a highly effective feed channel can also cause the cooling jet to lift-off the surface and mix with the hot gas path, which was seen with some rib and hole combinations and with the triangle -- vertex down supply channels. Therefore, the hole shape, the supply channel geometry, and the junction between the two all significantly contribute to a cooling scheme's performance and all three must be considered concurrently to create an optimal cooling design.
Author: Publisher: ISBN: Category : Languages : en Pages : 88
Book Description
The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.
Author: National Academies of Sciences, Engineering, and Medicine Publisher: National Academies Press ISBN: 0309664225 Category : Science Languages : en Pages : 137
Book Description
Leadership in gas turbine technologies is of continuing importance as the value of gas turbine production is projected to grow substantially by 2030 and beyond. Power generation, aviation, and the oil and gas industries rely on advanced technologies for gas turbines. Market trends including world demographics, energy security and resilience, decarbonization, and customer profiles are rapidly changing and influencing the future of these industries and gas turbine technologies. Technology trends that define the technological environment in which gas turbine research and development will take place are also changing - including inexpensive, large scale computational capabilities, highly autonomous systems, additive manufacturing, and cybersecurity. It is important to evaluate how these changes influence the gas turbine industry and how to manage these changes moving forward. Advanced Technologies for Gas Turbines identifies high-priority opportunities for improving and creating advanced technologies that can be introduced into the design and manufacture of gas turbines to enhance their performance. The goals of this report are to assess the 2030 gas turbine global landscape via analysis of global leadership, market trends, and technology trends that impact gas turbine applications, develop a prioritization process, define high-priority research goals, identify high-priority research areas and topics to achieve the specified goals, and direct future research. Findings and recommendations from this report are important in guiding research within the gas turbine industry and advancing electrical power generation, commercial and military aviation, and oil and gas production.
Author: Francis H. Froes Publisher: Elsevier ISBN: 0128140631 Category : Technology & Engineering Languages : en Pages : 482
Book Description
Additive Manufacturing for the Aerospace Industry explores the design, processing, metallurgy and applications of additive manufacturing (AM) within the aerospace industry. The book's editors have assembled an international team of experts who discuss recent developments and the future prospects of additive manufacturing. The work includes a review of the advantages of AM over conventionally subtractive fabrication, including cost considerations. Microstructures and mechanical properties are also presented, along with examples of components fabricated by AM. Readers will find information on a broad range of materials and processes used in additive manufacturing. It is ideal reading for those in academia, government labs, component fabricators, and research institutes, but will also appeal to all sectors of the aerospace industry. Provides information on a broad range of materials and processes used in additive manufacturing Presents recent developments in the design and applications of additive manufacturing specific to the aerospace industry Covers a wide array of materials for use in the additive manufacturing of aerospace parts Discusses current standards in the area of aerospace AM parts
Author: Ian Gibson Publisher: Springer Nature ISBN: 3030561275 Category : Technology & Engineering Languages : en Pages : 685
Book Description
This textbook covers in detail digitally-driven methods for adding materials together to form parts. A conceptual overview of additive manufacturing is given, beginning with the fundamentals so that readers can get up to speed quickly. Well-established and emerging applications such as rapid prototyping, micro-scale manufacturing, medical applications, aerospace manufacturing, rapid tooling and direct digital manufacturing are also discussed. This book provides a comprehensive overview of additive manufacturing technologies as well as relevant supporting technologies such as software systems, vacuum casting, investment casting, plating, infiltration and other systems. Reflects recent developments and trends and adheres to the ASTM, SI and other standards; Includes chapters on topics that span the entire AM value chain, including process selection, software, post-processing, industrial drivers for AM, and more; Provides a broad range of technical questions to ensure comprehensive understanding of the concepts covered.
Author: Chaitanya D Ghodke Publisher: SAE International ISBN: 0768095026 Category : Technology & Engineering Languages : en Pages : 238
Book Description
Gas turbines play an extremely important role in fulfilling a variety of power needs and are mainly used for power generation and propulsion applications. The performance and efficiency of gas turbine engines are to a large extent dependent on turbine rotor inlet temperatures: typically, the hotter the better. In gas turbines, the combustion temperature and the fuel efficiency are limited by the heat transfer properties of the turbine blades. However, in pushing the limits of hot gas temperatures while preventing the melting of blade components in high-pressure turbines, the use of effective cooling technologies is critical. Increasing the turbine inlet temperature also increases heat transferred to the turbine blade, and it is possible that the operating temperature could reach far above permissible metal temperature. In such cases, insufficient cooling of turbine blades results in excessive thermal stress on the blades causing premature blade failure. This may bring hazards to the engine's safe operation. Gas Turbine Blade Cooling, edited by Dr. Chaitanya D. Ghodke, offers 10 handpicked SAE International's technical papers, which identify key aspects of turbine blade cooling and help readers understand how this process can improve the performance of turbine hardware.
Author: Amit Bandyopadhyay Publisher: CRC Press ISBN: 1498766706 Category : Technology & Engineering Languages : en Pages : 547
Book Description
The field of additive manufacturing has seen explosive growth in recent years due largely in part to renewed interest from the manufacturing sector. Conceptually, additive manufacturing, or industrial 3D printing, is a way to build parts without using any part-specific tooling or dies from the computer-aided design (CAD) file of the part. Today, mo
Author: Ian Gibson Publisher: Springer ISBN: 1493921134 Category : Technology & Engineering Languages : en Pages : 509
Book Description
This book covers in detail the various aspects of joining materials to form parts. A conceptual overview of rapid prototyping and layered manufacturing is given, beginning with the fundamentals so that readers can get up to speed quickly. Unusual and emerging applications such as micro-scale manufacturing, medical applications, aerospace, and rapid manufacturing are also discussed. This book provides a comprehensive overview of rapid prototyping technologies as well as support technologies such as software systems, vacuum casting, investment casting, plating, infiltration and other systems. This book also: Reflects recent developments and trends and adheres to the ASTM, SI, and other standards Includes chapters on automotive technology, aerospace technology and low-cost AM technologies Provides a broad range of technical questions to ensure comprehensive understanding of the concepts covered
Author: Thomas Corbett
Author: Alexander Wildgoose
Author: Emma Veley
Author: 
Author: National Academies of Sciences, Engineering, and Medicine
Author: Francis H. Froes
Author: Ian Gibson
Author: Chaitanya D Ghodke
Author: Amit Bandyopadhyay
Author: Ian Gibson