turbine engine phd thesis topics

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Children are naturally curious—they want to know "how" and "why. In this minilesson, students organize the information they have compiled through the research process by using sentence strips. Students first walk through the process using information on Beluga whales as a model. Students match facts written on sentence strips to one of four categories: appearance, behavior, habitat, and food. Sentence strips are color-coded to match each category. The sequence of notes sentence strips under each category are case studies page in an indented outline form, and regrouped so that similar facts are placed together.

Turbine engine phd thesis topics literature review book keeping

Turbine engine phd thesis topics

THESIS STATEMENTS COMPARING CONTRASTING ESSAYS

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Paxson, D. Subashki, G. Wang, V. Hall, D. Jedamski, D. Kiss, A. Lieu, M. Siu, N. Tiralap, A. Barile, K. Clifton, D. Espitia, A. Everitt, J. Palmer, T. Peters, A. Sorensen, W. Walton, E. Yang, D. Brand, M. Catafalmo, P. Grasch, A. Guo, W. Kottapalli, A. Mazur, S. Aubry, A. Baltadjiev, N. DiOrio, A. Lusardi, C. Sakulkaew, S. Sato, S. Colas, D. Cook, E. Garza, T. Defoe, J. Huang, A. Mulchandani, H. Zlatinov, M. Glass, B. Hanley, B.

Kerner, J. Weed, P. Benneke, B. Nolan, S. Ng, L. Patel, A. Reichstein, G. Tanaka, S. Walker, III, T. Botros, B. Chan, N. Jovanovic, S. Kiwada, G. Yen, B. Hill, IV, R. Mobed, D. Shah, P. Bert, J. Cohen, E. Gould, K. Le Floch-Yin, F. Lei, V.

Plas, A. Shinagawa, Y. Teo, C. Villanueva, A. Castiella Ruiz de Velasco, J. Dakhel, P. Freuler, P. Kambouchev, N. Klima, K. Liu, L. Parker, D. Sakaliyski, K. Sirakov, B. Smythe, C. Tournier, S. Ahsun, U. Bernier, M. Choi, D. Collin, J. Fitzgerald, N. Kountras, A. Lackner, M. Manneville, A. Park, S. Protz, C. Savoulides, N. Spadaccini, C.

Combining new physics-based tools with emerging tools based on artificial intelligence AI and machine learning would enable alloys such as those mentioned above to be examined in much more detail, at lower cost, and in less time that has been possible using traditional development processes and tools. Nickel-based superalloys have been used in gas turbines for more than 50 years. For much of this time, the aerospace industry has been able to rely on continued development of nickel alloy classes that are produced by directional solidification e.

These classes of alloys have reached their operational temperature limits with current gas turbine designs. As new requirements have been established to increase efficiency, decrease weight, and reduce emissions, it has become necessary to increase main gas path temperature.

The increase in temperature drives the need for alloy technologies that can operate at higher temperatures and still meet design life requirements. As the gas turbine industry utilizes CMCs for specific components to meet the higher operating temperature requirements of gas turbines with improved efficiency, it will become increasingly important to consider metallic gas turbine components that will also be required to operate at higher temperatures.

In order to take full advantage of the higher temperature capability of CMCs, the temperature of the entire hot gas path would increase. Most of the components in the hot gas path are currently fabricated from alloys. Advanced high-temperature alloy technology development has generally been focused on 1 directional solidification casting technology, 2 nickel-based superalloy chemical composition development for turbine blades and vanes, and 3 powder metallurgy-based superalloys for disk rotor applications.

Research and development to increase temperature capability has reached diminishing returns. Additive manufacturing and the ability to manufacture components with advanced cooling. Refractory alloys retain favorable mechanical properties at very high temperatures. Examples include tungsten, niobium, and molybdenum. Ramprasad, R. Batra, G. Pilania, A. Mannodi-Kanakkithodi, and C. Kim, , Machine learning in materials informatics: Recent applications and prospects, npj Computational Materials 3 54 , doi Issues with cracking, hot tearing, and the unique grain structures associated with the emerging suite of processes will need to be understood and addressed.

Future development required to allow CMC components to reach their full potential in terms of temperature capability will need to focus on increasing the temperature capability of a large number of the metallic components in the main gas path for which CMCs are unsuitable. These components include blades and vanes, rotors, cases, shafts, seals, and bearing materials. The most advanced high-temperature materials, such as single-crystal airfoils and advanced corrosion and thermal barrier coatings, are used in the high-pressure turbine and combustor, which are the highest temperature sections of the gas turbine.

As the temperature of the main gas path of the gas turbine increases, advanced high-temperature material technologies will be needed in additional areas of the gas turbine. The application of coatings to protect components such as cases and disks from corrosion will need to function for thousands of hours of operation without reducing the base alloy mechanical properties.

Gas turbine components have been largely limited to the production of components comprising a single alloy composition and single manufacturing process. A hybrid component is manufactured from materials that have dissimilar properties. The ability to use hybrid structures increases design options and flexibility by providing a component with more optimum, location-specific properties.

Hybrid turbine disks, for example, are being developed that comprise alloys that have distinctly different alloy compositions and are produced by distinctly different manufacturing processes than each other. The hybrid turbine disk shown in Figure 3. The rim of the turbine disk consists of an alloy that is produced by a single-crystal casting process. The separately manufactured sections of the turbine disk are then bound to each other using a joining process such as inertia bonding.

The polycrystalline alloy bore would provide low-temperature burst strength where that property is required, and the single-crystal alloy rim would provide high-temperature creep strength where that property is required. Some alloy technologies have the potential to exceed the temperature capability of the latest generation of nickel-based superalloys.

Refractory alloys have the potential to provide both superior high-temperature mechanical properties and ductility. Niobium-based and molybdenum-based refractory alloys strengthened with intermetallic compounds have been developed. Thus far, however, high-temperature oxidation and significant processing challenges have prevented their use in gas turbines. New manufacturing technologies, such as additive manufacturing, may be used to fabricate unique microstructures that address previously identified shortfalls in properties for refractory alloys.

Because cobalt-based alloys have such a high melting point, they also have the potential to be used at temperatures exceeding those of current nickel-based alloys. Improving the capabilities of lower temperature alloy systems, such as those based on titanium, magnesium, and aluminum, would also be beneficial for fan and compressor components.

These materials offer strength-to-density ratios at high temperatures that exceed the capability of current state-of-the-art high-temperature composite materials. Development of processing models and integrated computational materials engineering tools 24 would further enable the use of materials in these classes while improving product yield and lowering purchase costs. Current approaches to material development are largely experiential driven.

The ability to establish new materials computationally using first principles calculations, physics-based models, and AI methodologies would allow engineers to design and mature materials that are optimized for specific applications much faster than is currently possible. This research topic could accelerate ongoing research by providing the technology that is required to operate gas turbines at main gas path temperatures required to meet thermal efficiency goals.

In addition, the successful development and utilization of advanced, high-temperature alloy technologies will be essential in meeting life-cycle cost goals by increasing gas turbine service life. Current gas turbine designs are limited by the maximum temperature at which available materials can be used and still meet life requirements. This research topic comprises many individual technologies related to the development of high-temperature alloy technologies.

Expertise and capability are in place in government laboratories, universities, and industry to make substantial advances by There is low technical risk in advancing the technologies applicable to hybrid disks to progress from the current TRL 3 to TRL 9 by The basic manufacturing processes required to make this technology successful are known. For technologies related to high-entropy alloys, much fundamental work needs to be done, and it is more realistic to predict that this technology could advance from TRL 1 to TRL 4 by Work in this area faces medium technical risk.

This research topic applies to gas turbine applications for power generation, aviation, and the oil and gas industry because of the similarity in the materials used and turbine component designs. Research areas that do not have a strong interrelationship with the structural materials and coatings research area are not shown. Research Area Summary Statement: Integrate model-based definitions of gas turbine materials those already in use as well as advanced materials under development , materials processes, and manufacturing machines with design tools and shop floor equipment to accelerate design and increase component yield while reducing performance variability.

As noted in Chapter 1 , additive manufacturing is a global technology trend that will benefit a wide array of industrial applications. This research area will develop turbine-specific design and manufacturing approaches for three-dimensional 3D -printed turbine components. Technology opportunities exist in integrated design of novel, cooled components, new high-temperature alloys, and morphological control of microstructure for tailored properties.

These advances are quite challenging because they must be implemented and ultimately qualified in the extreme conditions within a gas turbine. Key benefits for gas turbines are reduced weight, reduced part count, access to new design spaces, and reduced development time. Additive manufacturing has evolved dramatically over the past 30 years, and the rate of change continues to increase.

Additive manufacturing emerged commercially in with stereolithography from 3D Systems, a process that uses a laser to solidify thin layers of a liquid polymer that is sensitive to ultraviolet light. Selective laser sintering became available in , using heat from a laser to fuse powder materials. In , AeroMet developed a process called laser additive manufacturing that used a high-power laser to weld powdered titanium alloys, followed quickly by Optomec, which commercialized its laser powder forming system for fabricating metal parts based on technology developed at Sandia National Labs.

Extrude Hone now ExOne introduced another additive manufacturing process in with a system based on 3D inkjet printing technology from the Massachusetts Institute of Technology to build metal parts. In , Generis GmbH commercialized a system that used an inkjet printing technique to fuse sand to produce sand cores and molds for metal castings.

By , direct metal laser melting had evolved to include stainless steel and cobalt-chrome materials; and Arcam was distributing electron beam melting systems for metal powders. Concept Laser soon followed with the M2 system for processing reactive materials such as aluminum and titanium for direct metal laser melting. Direct metals processing technologies have garnered significant interest and growth based on the possibility of novel designs, combined with mechanical properties that are nearly equivalent to wrought alloys.

The adoption of metal-based additive manufacturing has continued to accelerate, with the biomedical and aerospace communities leading the way. Feature resolution and process controls have continually improved, with applications touching on a broad range of industries, including dental and medical, industrial, aerospace, jewelry, and even sand-casting molds.

Designers of industrial products generally leverage a full range of material and manufacturing options at their disposal for the development of cost-effective components with optimal performance characteristics. Additive manufacturing presents pathways to previously inaccessible design spaces, motivating the development of a new suite of responsive design tools that couple with manufacturing simulation in order to maximize the advantages of additive manufacturing.

The digital artifacts of this new design-for-manufacturing process 26 can be captured in a digital thread infrastructure, 27 which enables information sharing across the digital infrastructure to improve the performance of the product design and manufacturing process.

While there are many potential avenues for additive manufacturing, the design of new high-temperature materials compatible with these layer-by-layer manufacturing approaches promises improved system performance enabled by combining new materials with innovative component designs. Controlling local grain structure promises further optimization.

Advances in integrated sensing, autonomous analysis of sensor data, and process correction will be required to enable high-quality, high-manufacturing yields, and rapid feedback to the design process. Challenges for additive manufacturing of particular relevance to gas turbines include the ability to successfully manage potentially damaging process-induced phenomena such as increased distortion and cracking, print defects e.

Wohlers and T. Helu and T. Hedberg, Jr. This will require mastery of the complex physics of these printing processes, including high and rapidly varying temperature gradients, complex melt pool fluid flow phenomena, widely varying solidification morphologies, and residual stresses during the cooling process. Research Topic Summary Statement: Develop advanced methods for integrating models of materials, processes, machines, and cost with computer-aided design CAD software to create a complete digital engineering framework that accommodates the particular needs of gas turbine designers for additive manufacturing.

Expanding additive design aids and enhancing design practices will enable turbine-specific benefits in terms of reduced life-cycle costs by adapting general advances in the state of the art of additive manufacturing to issues specific to gas turbines, in part doing the following:.

Current design methodologies and design practices for product development have been optimized based on conventional manufacturing processes using primarily subtractive manufacturing techniques to post-process wrought or cast components. These methodologies do not allow the creative geometries and design options that have been enabled by additive manufacturing and that have begun to revolutionize much of the gas turbine design and manufacturing paradigm.

The process of building parts incrementally, layer by layer, reduces costs and weight, enables innovative designs, and challenges the order and speed of the traditional hardware development cycle. Gas turbines are already very complex machines, but their performance could in many cases be improved by the ability to incorporate parts with even higher levels of complexity, to the point that the parts are impossible to manufacture using conventional processes.

Additive manufacturing also offers a unique ability to substantially reduce the costs and cycle time of producing complex development hardware by enabling prototype hardware designs to be manufactured, tested, revised, and remanufactured much more quickly and inexpensively than is currently possible. This research topic could accelerate ongoing research in gas turbines by greatly enhancing the ability to design gas turbine components to improve their performance, affordability, and manufacturability.

This would reduce uncertainty in going from design to manufacture, leading to high-fidelity, location-specific designs for higher performance components with less rework. Additionally, advances in model-based engineering tools are essential to take full advantage of the design benefits offered by additive manufacturing.

Specific benefits will include the following:. This research topic could advance relevant technology from TRL 4 to TRL 6 by by improving component durability, increasing turbine efficiency, and reducing life-cycle costs. The research topic has medium technical risk primarily because of the broad spectrum of additive manufacturing processes and the need to control the process on a layer-by-layer basis.

Each additive process poses unique challenges and restrictions to the design community. Rapid solidification for laser powder beds, sintered powder removal, and build zone heat control for electron beam processes, and dimensional control during sintering and densification of binder jet additive processing all pose unique challenges for designers of additive manufacturing parts.

As a result, design aids and design practices need to be customized as a function of the additive process type. Regardless, the payoff is significant for each process that is targeted for use in high-temperature turbine applications.

Advances in model integration across disciplines are essential to more rapid, accurate, and complex design and manufacturing. These problems are challenging, but engineering has been on this trajectory for several years already. This research topic applies pervasively to gas turbines for power generation, aviation, and oil and gas applications because of the similarity in turbine component designs and the processes used to manufacture components.

Research Topic Summary Statement: Develop new high-temperature structural materials and advanced additive manufacturing equipment and processes in order to raise the thermal efficiency and operating temperature limits and increase the durability of gas turbine components produced using additive manufacturing; in addition, accelerate the qualification process for their application.

The gas turbine industry will drive the development of new high-temperature structural materials that can be used with additive manufacturing; and advances in additive manufacturing equipment will be required to process what is envisaged to be more refractory materials than are currently used today.

Greater coupling of computational and characterization tools is required to quickly identify new material compositions designed for additive manufacturing. These tools would support modeling of key phenomena and determine which combinations of processing and composition modifications can mitigate the driving forces for crack formation. Multiple conventional energy sources as well as new types of sources, such as femtosecond lasers, will be required to deliver energy in an ever more managed fashion to speed build rates and control distortion.

To ensure affordability of components produced with these new material compositions and additive techniques, this research topic would take advantage of the global technology trend in additive manufacturing see Chapter 1 , particularly with regard to the development of new, lower cost methods for powder production. The largest gains in the performance of gas turbines are likely to be achieved in the hottest sections of the gas turbine.

One approach for raising the operating temperature limits and increasing the durability of parts is through use of materials processed to a directionally solidified or single-crystal form. The development of new compositions, additive manufacturing methods, and models that enable the growth and repair of directionally solidified or single-crystal components would be game changing for both design and manufacturing.

Rapid qualification and certification methodologies will also be needed to accommodate the wide range of additive manufacturing techniques, structural material compositions, and gas turbine applications in order to cost-effectively produce components with higher temperature limits and durability. The harsh operating environments in gas turbines require a unique set of highly engineered properties. Limited efforts are already under way to expand the compositional range of structural materials specifically designed for additive manufacturing that can meet these harsh conditions.

The highly tailorable nature of the local processing conditions available in additive manufacturing will enable custom structural material compositions for additive manufacturing. It will be possible for compositions to be modified to enable higher yield through lower incidence of cracking phenomena and deleterious residual stress.

Thus, new strategies and methodologies for applying and managing energy will also be needed to accommodate new compositions. Additionally, new structural material compositions will benefit from advances in powder processing techniques aimed at producing higher temperature and higher quality powder in large quantities. The stringent performance requirements of gas turbines have consistently driven the design of structural materials to give at least equal weight to the precise tailoring of microstructures in order to maximize performance.

While novel processing of directionally solidified and single-crystal materials using advanced casting techniques is now an industry standard, precise control of microstructures in additively manufactured components remains a challenge. A new combined test and simulation-based analysis approach to part qualification has been elusive, but it is essential to the rapid and cost-effective employment of high-temperature materials for additive manufacturing.

This research topic could accelerate ongoing research in this area by focusing on the development of new additive manufacturing equipment capabilities and configurations. These new capabilities would enable the processing of new, higher temperature structural material compositions as well as novel methods for controlling microstructures. Additionally, these capabilities could enable the development of additive processes. Accelerating the development of rapid material and process certification and qualification methods will enable much more efficient and widespread application of additive manufacturing.

Advances in additive manufacturing equipment capabilities have a high probability of meeting the requirements for producing advanced structural material compositions in a production setting. New production paths to affordable, high-quality powder are also likely to be invented and introduced, although perhaps only on a small scale by The most challenging aspect of this research topic will be developing the ability to tailor microstructures during the manufacturing process to produce columnar-grained or single-crystal parts.

However, advances in risk assessment methodologies are likely to support the application of rapid qualification and certification methods. This research topic has medium technical risk because global advances in additive manufacturing are rapidly advancing the equipment design concepts and the understanding of fundamental processes that underpin this topic. This research topic applies to power generation, aviation, and oil and gas applications because of similarities in relevant materials and component designs.

Research Topic Summary Statement: Integrate models of physics-based composition, processing, microstructures, and mechanical behavior with artificial intelligence AI analysis and decision making of process signals into the manufacturing infrastructure to enhance process controls and first-time yields of gas turbine components.

The gas turbine industry already has great interest and robust research efforts under way in precision manufacturing and process controls because there are few other engineering applications of additive manufacturing that require such a high level of performance, reliability, and safety. This is especially challenging given the demanding operational environments within a gas turbine. Advances in precision manufacturing process control for gas turbine components will easily transition to other industries, resulting in higher product yields.

Physics-based process models and AI systems will need to be integrated with factory operational technology for real-time, intelligent control and for instantaneous feedback on manufacturing processes. This will require in situ sensing of material states and autonomous methods for real-time defect identification and repair during manufacture.

A digital record of the manufacturing process will need to be automatically placed in a digital thread infrastructure for further engineering use in the component life cycle. Additive manufacturing is an extraordinarily complex means of processing materials into a useful engineering component. Several additive manufacturing processes are being used or explored for their utility in the gas turbine industry, including powder bed fusion using either electron beam or laser heating sources and directed energy deposition using blown powder or wire fed processes.

While some of the parameters may not affect. With a goal of correcting defects in situ, analysis of process feedback on critical parameters will need to be immediate i. Complete, physics-based models for each of these methods is several years off, and even once developed, they will very likely be too complex to be integrated as part of a process control system.

A digital representation of the process will therefore be essential to inform material review boards, to improve additive manufacturing processes, and to identify potential in-service issues in a timely fashion. This research topic could accelerate ongoing research in this area by improving manufacturing quality, increasing product yields, reducing property distributions, and enabling more rapid qualification of additive manufacturing processes.

Additional benefits include the creation of a robust path to continuous process improvements while assisting scientists seeking to improve physics-based models of manufacturing processes. Many individual tools are now available and are beginning to be integrated. This will be a continuously evolving technology as additional advances in physics-based models, in situ sensing, and AI are made and integrated into process control systems. At present, these process control systems are quite rudimentary but are expected to make substantial gains given the current rate of progress being made in each of the supporting technologies.

As noted in Chapter 1 , global technology trends will ensure continued advances in autonomous systems, physics-based models, and AI apart from research that may be conducted as part of this research topic. This research topic has medium technical risk due to the difficulty in developing useful physics-based models and relevant in situ sensing methodologies given the sheer complexity of additive manufacturing, especially with regard to the more challenging aspects of gas turbine applications.

However, advances in materials characterization techniques to inform model development and relevant global technology trends will mitigate the risks associated with the complexity. This research topic applies to gas turbines for power generation, aviation, and oil and gas applications because of the similarity in turbine component designs and the processes used to manufacture components. The red arrow with an arrowhead at each end shows where two research areas are mutually supportive to a substantial degree.

Research areas that do not have a strong interrelationship with the research area on additive manufacturing for gas turbines are not shown. Research Area Summary Statement: Develop advanced cooling strategies that can quickly and inexpensively be incorporated into gas turbines and enable higher turbine inlet temperatures, increased cycle pressure ratios, and lower combustor and turbine cooling flows, thereby yielding increased thermodynamic cycle efficiency while meeting gas turbine life requirements.

Given the importance of reducing CO 2 emissions, reducing fuel usage by increasing gas turbine efficiencies continues to remain of high interest to the gas turbine industry. As discussed in Chapter 1 , thermal efficiencies of gas turbines and, by extension, fuel burn, are directly related to the turbine inlet temperature.

The adiabatic efficiencies of compressors and turbines are also strong drivers of thermal efficiency. Two different approaches are typically employed in order to improve gas turbine thermal efficiency: 1 increase turbine inlet temperatures while maintaining the same cooling flow requirements, or 2 maintain the same turbine inlet temperatures while decreasing the cooling flow level.

Both approaches may reduce turbine life unless thermal management schemes increase overall cooling effectiveness. Increasing overall cooling effectiveness at a constant turbine inlet temperature reduces turbine component metal temperature and increases component life.

Alternatively, increasing the overall cooling effectiveness while increasing turbine inlet temperature may yield constant turbine component metal temperature, and by extension, turbine component life. Turbine inlet temperatures over time track well with the overall cooling effectiveness levels produced by advancing film cooling, as shown in Figure 3. Increasing cooling effectiveness reduces airfoil temperatures, thereby allowing higher turbine inlet temperatures.

Cooling concepts for the hot section of the gas turbine, which include the combustor and the turbine modules, were envisioned from the very beginning of gas turbine research and development. Blade cooling, however, did not appear in operational equipment until the s.

Blade cooling is achieved by extracting air from the compressor prior to entering the combustor and then routing the extracted air into components located in the combustor and turbine modules to cool those components. Modern gas turbines benefit from decades of impactful research on high-temperature alloys, advanced coatings, and improved cooling technologies.

Combining state-of-the-art nickel-based superalloys with the application of more advanced cooling technologies, such as micro-channel cooling also referred to as double-wall airfoils , has allowed for continual increases in turbine inlet temperatures. Concurrently, increases in thermal efficiencies have.

As cycle pressure ratios increase, the temperature of the air extracted from the compressor for cooling the combustor and turbine modules also increases. Since increased compressor discharge air temperature is a limiting factor in effectively cooling combustor and turbine hardware, developing thermal management techniques that enable higher coolant temperatures are integral to meeting hot section durability requirements.

State-of-the-art cooling flow requirements for components in the combustor and turbine modules reach as high as 25 percent of the air flow entering the compressor, depending on the application. Limitations exist in the current cooling strategies, however, from manufacturing constraints. For example, the shapes of film-cooling holes, which are placed in the turbine airfoils after casting, are limited by both the laser drilling and electro-discharge machining processes.

Past research has also identified some key subjects in which our fundamental physical understanding is lacking, thereby limiting the ability to advance gas turbine designs. One such subject is full conjugate heat transfer analyses, in which a single model examines heat transfer involving both fluids and solids in a particular system. Because existing models are not able to accurately capture the complex, 3D thermal energy exchange between cooling film flows and the main gas path, the optimization of combustor and turbine cooling configurations is limited.

Greater understanding is also needed regarding the effects of particle-laden flows entering the gas turbine from the external operating environment. For power generation as well as oil and gas applications, filters remove the large particles without significant pressure penalty; however, small particles can still exist in the supply air.

For propulsion applications, filters are not feasible due to the pressure drop penalty. In the case of propulsion, while on the ground the inlet supply air to the gas turbine can contain surrounding dirt and sand, while in the air, the inlet supply air can contain volcanic ash and other particulate matter found in the atmosphere.

Research Topic Summary Statement: Improve turbine component efficiencies through innovative cooling technologies and strategies. Research to develop innovative cooling strategies needs to address the high temperatures and high mechanical stresses that turbine components experience as well as specific material properties and manufacturing methods. Turbine aerodynamic performance and durability requirements drive increased geometric complexity for cooling the combustor walls as well as in the vane and blade hardware.

Effective turbine thermal management in future gas turbines is related to the technological capability to manufacture geometrically complex components comprising high-temperature materials. Because of increases in the cycle pressure ratio, the air extracted from the compressor outlet to cool components in the combustor and turbine modules is at a higher temperature than in earlier generations of gas turbines. As a result, in some cases innovations will be needed to cool the coolant air.

Turbine airfoils for power generation, propulsion, and oil and gas applications are typically manufactured using investment casting. Several steps are required for this process, starting with pouring wax into metal molds in the shape of the airfoil. Once each wax shape has set, it is removed from the mold and repeatedly immersed in a ceramic slurry bath, forming a ceramic coating that is then heated to further harden the ceramic and melt the wax.

The actual airfoil is formed by pouring molten metal into the hollow space left behind from the melted wax. The internal air-cooling passages within each blade are also formed during this stage of production by inserting ceramic cores into the wax pattern. After the blades are further machined, film-cooling holes are placed in the external walls of the airfoils that lead to the internal passages that supply the coolant. Once the cooling holes are manufactured, a thermal and environmental coating is applied to the external surfaces of the airfoils to improve resistance to corrosion and oxidation as well as insulate the airfoil from the hot main gas path flow.

Combustor walls are typically constructed from relatively thin sheets of high-temperature metal in a double-wall configuration where the external surfaces are sprayed with thermal and environmental coatings. The cooling strategies used for the combustor walls are similar to those used for vanes and blades. Research for both the turbine and combustor modules are typically categorized as either internal cooling for surfaces inside the vane blade or between the combustor liner double-wall or external cooling for surfaces exposed to the hot gas path.

Internal cooling strategies could achieve high convective heat transfer coefficients through the use of highly turbulent flows and large surface areas, but only if geometric constraints can be overcome and if enough pressure. Typical internal cooling strategies for the leading edges of airfoils include impinging jets on the backside of the inside airfoil surface. For the main body of the airfoil, serpentine channels that contain ribs are used to increase surface area and flow turbulence. Near the trailing edge where the blade external heat transfer coefficients are very high and the passages are required to be very thin due to the narrow trailing edges of the airfoils, pin fins are often used for high convective cooling while enhancing structural integrity.

For the combustor walls, impingement cooling between the double-wall is commonly used along with pin fins between the two walls for increased surface area and turbulence while also improving structural rigidity. Advanced internal cooling strategies for vanes and blades are often limited by the design of the die for the ceramic cores or the ability to cast small features.

The tooling often restricts the designs of internal cooling passages. While there has been significant research on developing more effective ceramic cores for the casting, as discussed above additive manufacturing could open new opportunities. Another potential internal cooling strategy is to place microchannels in the skin of turbine airfoils to bring the cooling closer to the airfoil surface. After cooling the internal surfaces of the airfoils and combustor liners, the coolant flow is exhausted through film-cooling holes.

In the case of the airfoils, the coolant is also exhausted through slots in the trailing edge. On the external hot gas side of the airfoil and combustor walls, it is preferable to reduce convective heat transfer from the hot gas path. State-of-the-art manufacturing methods for film-cooling holes use either laser-drilling or electro-discharge manufacturing, which are processes completed after casting the turbine airfoil. In combustor walls, which are often double-wall designs, film-cooling holes are similarly either laser-drilled or electro-discharge machined.

Additive manufacturing methods can lead to complex film-cooling hole shapes that are better integrated with the internal coolant supply channels, which is particularly important for the entrances to the film-cooling holes. More complex film-cooling hole shapes may improve the quality of the film protection on combustor and turbine hardware.

New manufacturing methods can also lead to removing the limitation of requiring a line of site as well as improve the tolerancing. Integral to innovative cooling designs is the development of high-temperature materials used to make turbine airfoils.

This research topic could accelerate ongoing research in innovative cooling strategies that enable higher turbine inlet temperatures, resulting in increased thermal efficiency while meeting life-cycle cost requirements. This research addresses a gap in the development of advanced cooling innovations in light of new high-temperature materials and additive manufacturing methods.

Furthermore, research in this area will further reduce the cost and risk of large-scale adoption of additive manufacturing techniques and hot section cooling strategies in gas turbines. An example of what has happened in the past in terms of increased turbine inlet temperatures has demonstrated the impact of innovations in cooling strategies, particularly film-cooling.

A disruptive increase in thermodynamic cycle performance is expected with the large-scale adoption of innovative cooling strategies enabled by additive manufacturing techniques and high-temperature materials. This research topic could advance relevant innovative cooling technologies from TRL 1 to perhaps as high as TRL 6 by The high TRL is expected as a result of integrating additive manufacturing and advanced materials. The research topic has medium to high technical risk, depending on the technology, because of potential difficulties in scaling up cooling innovations for application in operational gas turbines.

The full extent of this risk will depend somewhat on the development of additive manufacturing capabilities to reliably make the innovative cooling features at a cost and durability that are beneficial to the industry. The successful accomplishment of this research topic is therefore closely linked to the success of additive manufacturing as well as the time and cost to develop new cooling strategies.

This research topic applies to power generation, aviation, and oil and gas. Reducing fuel burn for all three applications is an important goal, particularly for power generation and for aviation. Improving the efficiency of oil and gas turbines when they are operating at partial loads has also been established as a priority. Research Topic Summary Statement: Develop advanced full conjugate heat transfer techniques to enable the optimum design of combustor and turbine cooling configurations, which would minimize component cooling air flow, enable increased turbine inlet temperatures, and allow for higher cycle pressure ratios.

Conductive heat transfer is typically the dominant form of heat transfer in solids, while convective heat transfer typically dominates in liquids. A full conjugate heat transfer model analyzes heat transfer involving both solids and liquids in a particular system. Validated full conjugate heat transfer techniques enable advances in optimizing combustor and turbine cooling configurations.

Full conjugate techniques capture the complex, 3D thermal energy exchange between cooling film flows, main gas path flows, internal flows, and the solid components more accurately than the more commonly used loosely coupled conjugate analytical processes that consist of separate and sequentially executed lower fidelity submodels.

These full conjugate heat transfer techniques will have more influence during the engineering design process if they are validated with heat transfer data acquired from coordinated experiments on canonical geometries and flow conditions, with the support of industry, academia, and government stakeholders. As discussed above, state-of-the-art cooling strategies for combustor and turbine modules include but are not limited to closely packed arrays for film-cooling holes that generate low-temperature films that 1 insulate the underlying metal and protective thermal barrier coating from the high-temperature combustion products in the main gas path and 2 augment the rate of convective heat transfer between the cooling air flow in these holes and the surrounding metal.

Furthermore, wall-bounded film flows that rapidly mix with fuel-rich hot gases promote secondary chemical reactions in the film and diminish the intended benefit of film cooling. The complex physics associated with the above are currently not understood. Computational thermal models for predicting hot section metal temperatures typically use a loosely coupled conjugate heat transfer approach.

For a turbine blade, submodels that capture the heat transfer processes among the internal fluid flow, the external fluid flow, and the metal and thermal barrier coating system are separately and sequentially executed until the temperatures at the interfaces of these models converge to the same value. The aerothermal submodels for the external airfoil surface use a combination of empirically driven low-fidelity and advanced high-fidelity tools to capture the effects of film mixing and insulation, heat transfer augmentation,.

These submodels are typically validated with results from controlled experiments, during which the aforementioned effects are often measured separately. For cooling strategies that include closely packed arrays of cooling holes, however, the cooling films interact, the solid conduction pathways become more 3D, and the energy exchange between the external fluid flow and the blade solid becomes more complex.

These complex aerothermal interactions are better captured with full conjugate heat transfer modeling techniques. Validated, full conjugate heat transfer modeling techniques for combustors and turbines with complex cooling configurations could be used to improve the accuracy of metal temperature predictions by reducing the modeling error associated with the simplified aerothermal submodels that are typically used in the loosely coupled conjugate analytical process.

Enhanced predictive accuracy would increase the accuracy of hot section component life forecasts, improve hot section component durability, reduce combustor and turbine cooling air flows, and enable higher turbine inlet temperatures for greater thermodynamic efficiency while satisfying mission life requirements.

This research topic has a medium technical risk. Its success depends on 1 the generation of comprehensive data sets obtained from full conjugate heat transfer experiments on canonical combustor and turbine cooling configurations and flow conditions that are accessible by the technical experts in the gas turbine industry, academia, and government and 2 the validation of full conjugate heat transfer models with these publicly available data sets.

This activity would require careful coordination among these key stakeholders. This research topic applies to power generation, aviation, and oil and gas applications for gas turbines operating at full and partial load. Research Topic Summary Statement: Develop a fundamental understanding of the physics and modeling of particle-laden flows in gas turbines that result from their respective operating environments. Gas turbines in many geographic regions operate in increasingly challenging environments, where the concentration of particles such as sand or atmospheric particulates can significantly degrade gas turbine performance and often lead to shutdowns, especially for aircraft and the oil and gas industry.

The basic physics associated with these environments is not well understood and requires integrated study using high-fidelity simulations and experimental validation for relevant environmental conditions ranging from simple to complex phenomena associated with particle ingestion. Environmental particles can erode compressor blades. Within the hot sections of a gas turbine i. This can cause particles to adhere to component surfaces, thereby setting off a chain reaction of severe events.

When a particle adheres to a surface, the metal temperature generally increases by either reducing the coolant flow due to blocked internal passages or increases the thermal resistance between the wall and coolant air. Higher metal temperatures, in turn, lead to higher temperatures of the particles adhered to the wall, thereby increasing the likelihood that more particles will adhere to the surface.

Walsh, K. Thole, and C. This research problem is specific to gas turbines because of the particular external environments in which they operate as well as the high temperatures present in the turbine. Modeling the complexity of this problem requires an integrated approach using high-fidelity numerical simulations along with experimental validation. Defined test cases are needed that range from simple, fundamental benchtop simulations to more turbine-relevant complex cases to assess how to develop a better understanding of the various mechanisms affecting turbine operations.

As global flight patterns increasingly traverse developing nations and as power generation and oil and gas turbines continue to be installed in a wide range of environments, the threat of small-particle ingestion into gas turbines grows. For power generation, contaminants that can reduce gas turbine performance include rust from upstream components and unfiltered particulates from the surrounding environment. For aircraft propulsion, contaminates of interest include volcanic ash, fine sand particulate suspended in the atmosphere or ingested during takeoff and landing, and industrial pollutants such as those generated by coal-burning power plants.

Poor air quality affects the performance of each gas turbine module differently. In the compressor module, erosion is the concern: environmental particles drawn in by the fan can subsequently impact the compressor blades. Both the fan and compressor sections work to pulverize the particles. Once reaching the high-pressure compressor section, from which discharge air is bled to cool hot section components, the particles are small enough to be carried with the secondary cooling flows, where temperatures are much hotter, causing particle deposition.

The particle deposition can block internal passages and cooling holes. In the main gas path, particles may be deposited on external airfoil surfaces, which increases their roughness. Rough turbine airfoils cause increased aerodynamic losses and can lead to early boundary layer transition on the airfoil resulting in high external heat transfer from the hot gases passing along the airfoils.

Where and how the particles deposit within a hot section component strongly depends on their size, composition, temperature, the internal cooling geometry, and the method of introduction. The mechanisms of particle transport and deposition within gas turbines are not well understood because all of the relevant conditions are nearly impossible to simulate in a controlled experimental environment.

In the turbine module, the friction drag from the high-speed coolant can keep particles in an aerosol state where the particles track the flow. However, given the particle mass and momentum, the particles do not necessarily follow the streamlines through the turns or various cooling features. Instead, the particles impact surfaces where there are several forces, which are not well understood, that will dictate whether the particle will adhere to the surface.

This research topic could accelerate ongoing research by identifying the principal mechanisms that drive the degradation of turbine durability from particle-laden flows. Once identified, these mechanisms would then be captured in experimental and numerical turbine simulations. The ultimate benefit of this research area is to provide a physics-based understanding of particle transport and deposition in high-pressure turbines that can be used to drive conceptual, particle-tolerant turbine cooling designs and to improve the quality of turbine component lifing forecasts in particle-laden flows.

The latter will enable expanded operational limits. Currently, there are. Basic, fundamental test cases are nonexistent, resulting in an inability to execute integrated, methodical experiments that enable the validation of low- and high-fidelity particle transport and deposition models relevant to turbine operations in particle-laden flows.

Physics-based models could be developed to drive various advanced, particle-tolerant turbine designs by Achieving a high-level of certainty in turbine lifing predictions would require significant breakthroughs in particle transport and deposition research and particle-tolerant turbine design concepts. This research topic has high technical risk because the models may need to be tailored to the specifics of each case because of the complex interactions.

The test cases to fully replicate gas turbine conditions at high pressures and temperatures are difficult at best. This research topic applies to aviation, power generation, and oil and gas applications, by providing a better understanding of how turbine operations are affected by particle-laden flows, which improves turbine cooling designs as well as lifing models needed.

For the aviation applications, particle-laden flows can disrupt operations by requiring aircraft to detour around regions such as volcanic plumes or over developing countries with an especially high concentration of particles, increase engine wear, and possibly lead to a loss of propulsion in flight.

For power generation and oil and gas applications, particle-laden flows increase the frequency of maintenance and reduce the overall efficiency of the gas turbines. Research areas that do not have a strong interrelationship with the thermal management research area are not shown. Research Area Summary Statement: Develop and validate physics-based, high-fidelity computational predictive simulations that enable detailed engineering analysis early in the design process, including virtual exploration of gas turbine module interactions and off-design operating conditions.

Computational fluid dynamics CFD has been an important tool in aerospace engineering over the past four decades, and it has lowered development costs by reducing the number of physical tests required in the design process. The predominant CFD tool has been based on Reynolds averaged Navier Stokes RANS equations, which contain calibrated phenomenological models to represent the effect of turbulence fluctuations on the averaged flow quantities.

The accuracy of RANS is limited by phenomenological modeling assumptions. There are several flow features in the flow path of a gas turbine that RANS models have difficulty predicting, including 1 flow separation and turbulent mixing and 2 quantities such as thermoacoustic oscillations and fluctuations of pressure and temperature that require accurate prediction of unsteady turbulence fluctuations. Large eddy simulations are high-fidelity computations that attempt to capture most of the energetic unsteady 3D flow features in flows such as those in the interior of a gas turbine.

Subgrid-scale models are used to account for the effects of unresolved small-scale turbulent flow motions. This is in contrast to the RANS approach, for which the effect of all turbulence scales on the mean flow are modeled. Research Topic Summary Statement: Develop advanced, high-fidelity, predictive numerical simulations to permit expanded exploration of design spaces and to enhance system-level optimization to support the development of gas turbines with higher efficiencies, reliability, and durability, and with lower development costs.

Integrated numerical simulations can capture interactions among gas turbine modules. Interactions of interest include dynamic couplings, flow distortion, unanticipated heating or loading, 38 and thermoacoustic instabilities that manifest only when the system is integrated. Greater insight into system coupling yields more accurate aerothermal and structural boundary conditions and, by extension, more realistic module predictions than single-module models with simplified boundary conditions applied at the interfaces between modules.

Applying validated computational models could yield improved learning outcomes from subsystem rig and full engine tests, permit faster engineering design optimization, and reduce engineering development costs. It is related to pressure ratio across the stage. The first integrated multifidelity simulation 39 of an annular sector of a realistic gas turbine engine PW was demonstrated a decade ago.

The integration effort lacked robustness, as boundary conditions at the module interfaces had to be improvised. In the ensuing decade, computational power has increased by more than three orders of magnitude, and significant strides have been made in the development of accurate and efficient numerical methods that are especially suitable for prediction of the multiphysics turbulent flows 41 encountered in gas turbines.

This combination of advances in hardware and software have opened new opportunities for detailed engineering analysis in the design process, resulting in reduced design cycle time, avoidance of costly time and potential engineering rework, and more optimally designed gas turbine components. High-fidelity simulation capabilities have recently been used to study combustion instabilities in the GE 7HA heavy-duty gas turbine.

This research topic could accelerate ongoing research in this area by leveraging the significant advances made over the past decade in high-fidelity numerical simulation capabilities for analysis and design of the next-generation gas turbines, and provide a cost-effective means of assessing integration effects early in the design process.

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