One of the most innovative technologies of the last thirty years is undoubtedly Additive Manufacturing (AM). This new manufacturing technique has allowed engineers to rethink and create things that wouldn't be feasible with standard production methods, thanks to its working principle. Large energy companies often use AM to enhance the performance of engine components and as an alternative technology in the spare parts supply chain. For Gas Turbine (GT) Original Equipment Manufacturer (OEM) one of the most critical responsibilities, beyond developing new machines, is introducing innovation to legacy engines, some of which dated back to the 1960s. These models are still in operation and are still in demand worldwide due to their reliability. AM represents the perfect solution for this purpose, since it enables the complete redesign of a GT component to improve performance without altering the engine's basic layout, provided the original item's interfaces remain unchanged. Additionally, as already mentioned additive technology is also used by large energy companies as an alternative to Investment Casting (IC) in the spare parts supply chain. Maintaining an efficient supply chain based on IC can be very challenging and at the same time very expensive, as the casting tools age and can cost hundreds of thousands of dollars to produce and qualify new ones. On the other hand, AM allows multiple components for different machines to be manufactured simultaneously with the same printing machine and sometimes the costs can be equal to or even lower than those made by IC. This paper shows the redesign of a PGT5A nozzle made by additive as an alternative to the one made by IC focusing on all the design improvements developed to increase its performance.

Gas turbines play a critical role in industries such as power generation and aviation. Additive manufacturing has emerged as a game-changing technology for gas turbine components, offering superior design flexibility and performance enhancements. The present work provides an overview of a multistep approach for integrating lattice structures into a specific gas turbine component, the Nozzle Guide Vane (NGV), using additive manufacturing technology. The first step involves a comprehensive assessment of lattice structures’ influence on the mechanical and thermal properties of the exposed part of NGV. Through computational simulations and experiments, an ideal lattice geometry is determined, optimizing structural integrity and heat transfer properties while minimizing volume usage. The second step sets the baseline performances of the current NGV system components, which were investigated and selected for additive manufacturing analysis. The third step focuses on the overall effect of additive manufacturing capabilities in the NGV system. The fourth and final step optimizes the additive manufacturing process for fabricating gas turbine components with lattice structures. Laser Powder Bed Fusion (L-PBF) technology, united with advanced Topological Optimization analyses, and high-temperature alloys were selected to withstand the demanding gas turbine operating conditions. This multistep approach represents a significant step forward in gas turbine technology, capitalizing the advanced mechanical applications as lattice designs and additive manufacturing, aiming in enhanced performance, reduced weight, and improved efficiency. These developments hold the potential to achieve more sustainable and cost-effective energy generation and transportation systems.

Baker Hughes has been providing industrial gas turbines globally since the 1950s. Baker Hughes’s Frame 5/1 machine is well-known for its long-running performance in the field. After service life of parts are over, these parts are replaced with new parts. New technologies like Additive Manufacturing (AM) can reduce lead time and provide freedom to design engineers to explore designs that were not possible with conventional manufacturing in the past. This paper discusses the journey from conventional design to design for additive manufacturing for stage 1 nozzle (S1N) of the Frame 5/1 Machine. Direct Metal Laser Melting (DMLM), an AM technology, is considered for manufacturing of this nozzle. Furthermore, the extensive experience accumulated over the years from numerous 5/1 machines operating in the field is leveraged to enhance the optimization of nozzle design. Considering an in-house developed equivalent material in DMLM, the nozzle is redesigned to be compatible with the operating conditions of the current machine and its supporting structure without affecting performance. The structural integrity of the newly developed AM design of the S1N is validated by part life assessment, using the thermo-mechanical finite element Analysis (FEA), and compared against the product requirements. Based on the results of the part life assessment, further improvements were made through multiple design changes and iterations, resulting in the final design. The redesign leads to a significant improvement in the temperature gradient and lowers the metal temperature in S1N in comparison with conventional design. The analysis results demonstrate a significant improvement in overall stresses, plastic strains, creep strains and crack initiation life when compared to the conventional nozzle. Moreover, the predicted amount of oxidation for the new design is much lower than that for the conventional design.

One of the most critical phases of designing a competitive product such as a Gas Turbine is the conceptual phase, in particular the definition of the flow path, which decides the performance of the engine. Therefore, the ability to optimize the aerodynamic performance of the flow path has significant benefits, but, due to constraints related to the reduction of the time to market of new products, the optimization process is extremely limited. Typically, the definition of an acceptable flow path is an iterative process between the Aerodynamic and Structural teams, which requires a considerable amount of time leaving very little space for optimization. Considering the common architecture of a turbine, only the first stage nozzle can be supported both at inner and outer diameter, while all the other stages can be only supported at the outer. This leads to an extraordinarily strong structural and life constraint for airfoils definition because they must be properly seized to comply with creep requirements. According to the earlier design process, the aerodynamic optimization of the flow path was performed by means of a 1D tool, later on airfoils were built and analyzed from a structural standpoint to verify if they were complaint. The proposed function is based on a newly developed transfer function between the geometry parameters available from the 1D aero tool and the bending stress on the airfoils. Function has been trained on legacy engines and later verified and applied in ongoing studies. In this way the aerodynamic optimizer can obtain a preliminary mechanical assessment in real time on each configuration of the 1D flow path, allowing to generate only structurally verified configurations. The article explains how the tool works along with a case study highlighting its application. The findings confirm that this innovative tool can simplify and speed up the optimization of a 1D flow path.

Baker Hughes is providing gas turbine solutions and services across the world since 1950s. There are many legacy engines still working at customer sites requiring services every year. The different models/upgrades of Frame 3 and Frame 5 introduced to the market from 1950's to 1990's led to the existence of many parts resulting in complex supply chain management to maintain an active and high-quality production. This is true especially for the components which require an investment casting process, such as nozzle and blades. The investment casting tooling requires a minimum number of produced sets per year to ensure a high-quality production and so it needs to be re-qualified in case of low production. On the other side increasing the volume more than the requirements may lead to higher inventory management. In addition, conventional manufacturing processes need higher lead time to deliver the spare parts, that may cause the risk to not fulfill the customer expectations/needs. To avoid such challenges, additive manufacturing is introduced to move the manufacturing of service parts from external suppliers to inhouse, developing a full internal vertical capability through printing, post-processing, and final machining operations. This helps in improving the lead time as well as the part management and allowing the internal Product Leadership office to develop and speed-up the internal strategy for service parts. This paper explains the design considerations made during the introduction of additive manufacturing technology to produce nozzle spare parts for Frame 3 and Frame 5 machines. Material is selected for the printing, in such a way that the material property derived from a printed specimen is aligned or better than the material property of the original part. The design of the nozzles has been improved with changes at life critical locations, injecting the latest design technologies developed for new products inside the old nozzle layout and boundaries, taking advantage of huge fleet experience acquired in these years. The mechanical robustness of the innovative design has been verified according to the current analytical internal process and it has been proven through a field validation being several nozzles sets installed, operated, and inspected in Service fleet.

Gas turbine parts defining the flow-path of the turbine section are normally made of high-grade material due to its severe operating conditions. Transition duct which provides aerodynamic coupling between high-pressure and low-pressure turbine modules define the flow-path and thus are made of high-grade material fabrication. This part is typically subjected to huge thermal and mechanical loads requiring a thorough design assessment to verify the fulfillment with respect to the product requirement. Careful consideration of various design requirements in selection of the material is very vital in keeping the cost of the gas turbine under control while achieving the durability requirements. These parts defining the flow-path are designed in such a way that the thermal induced stress is within the material capability. To achieve this requirement, the part is restrained in such a way that it remains at the desired position during the operation. Despite this consideration, thermal induced stress is unavoidable due the internal constraints wherein one side is exposed to the flue-gas and the other side is exposed to the cooling medium to keep the part’s operating temperature within the material capability. This causes the thermal gradient across the part cross-section resulting in thermal induced stress. Adding to this, the fabrication requires material selection from wrought and cast form to minimize the cost while fulfilling the product requirements. Material capability of these two forms of the same material possess marginally differing material characteristics. Due to these dissimilar material characteristics and the presence of weld material is expected to result in differential thermal expansion and thus significant thermal induced stress at the interface. The stress induced thus poses a limitation and scope of material separation under the extended operation of the gas turbine. Sample case studies using finite element analysis are performed to understand the creep behavior at the interface before application into the finite element analysis of the design under consideration. All the probable combinations of materials and numerical simulations are verified in this case study for a better understanding. The understanding from this case study is applied into the finite element analysis of the transition duct with all the probable material combinations and studied its creep behavior. This structured approach facilitated in completing the design evaluation within the project schedule and keep the cost within the target. This paper is intended to describe the steps followed in studying the creep behavior of the gas turbine transition duct made in dissimilar material.

Currently the Energy Industry and Industrial Power Plants are committed to support sustainable development balancing environmental, economic, and social benefits. As the first two aspects are fully covered by environmental lifecycle assessment and life cycle costing, the third one is covered only for the portion regarding human health while other aspects, like local employment, contribution to economic development, supplier’s relationship, are not so easy to be measured. Social life cycle assessment (S-LCA) is considered a powerful tool to measure and improve a company’s sustainability. Yet there is not a unique way of measuring how a company or even a product is impacting on the well-being of the society. In general, S-LCA is seen as an opportunity to improve a company’s reputation, it can help handling social aspects in the lifecycle of a product or service. S-LCA methodology is evolving since 1996 when first attempt to evaluate the social impact of a product rose and many methodologies and databases are now available; at present the phase of S-LCA development is the research of standardization. A use case of S-LCA application to a gas turbine component will be presented comparing the impact of moving the production of one component from Investment Casting to Additive Manufacturing plus insourcing coating execution: proving the benefit of applying S-LCA to products. The findings allow comparing design and manufacturing alternatives to maximize sustainability of a product manufacturing.

The transition duct (TD) in a gas turbine (GT) twin shaft variant provides an aerodynamic coupling between its high-pressure gas generator module and low-pressure power module. Since the TD defines the flow passage, it interfaces with the high-pressure rotor and shroud at the forward end and the low-pressure rotor and stator at the aft end. Normally, the GT twin shaft variant is equipped with part-load capability. To fulfill this need and to comply with the emission norms, only desired number of burners, adjacent to each other, are used to burn fuel. Using some of the burners during the GT operation is referred to as staging. The GT operation under staging conditions result in non-uniform temperature distribution in the angular locations at any axial position and thus non-uniform thermal growth in the radial and axial directions. This non-uniform thermal growth in radial and axial direction leads to the interface definition very challenging. During the staging operation, the rotor parts experiences uniform radial and axial growth at all the angular locations. Whereas the interfacing stator parts experience temperature distribution like that of the TD and results in non-uniform thermal growth in the radial and axial directions. Appropriate interface definition is vital for efficient operation of the GT. Any interference condition of the TD with rotating parts result in rubbing and with stationary parts result in thermal binding, impacting the GT normal operation. Any generous gap adversely impacts the GT performance due to consumption of more cooling medium. Thus, an assembly gap which results in no interference and consumption of less cooling medium throughout the staging operation is considered as optimum assembly gap. Thorough gapping assessment is performed considering all the transient time points to ensure that the gap values are set optimally. This paper is intended to describe the steps followed in assessing the anticipated interference and gap situations at various interfaces.

Gas turbine nozzles are static components that are meant to turn and accelerate high temperature, high pressure, and low-velocity flue gas into the downstream turbine row of buckets. During gas turbine operation, nozzles are subjected to high-pressure load due to the expansion of flue gases, in axial and tangential directions. This creates a tendency for nozzle movement in tangential direction which has potential to create flow disturbance and intersegment gap opening. To prevent this movement, it should be held in tangential direction firmly by introducing an anti-rotation feature. A slot is introduced in the nozzle outer sidewall and a pin connected with casing in such a way that the nozzle’s tangential movement is restrained. As the nozzle’ s outer sidewall experiences high thermal gradients in the operating condition, it induces high stress at the nozzle anti-rotation feature. There are many possible design options available to mitigate this challenge. In the present work, anti-rotation feature is integrated with the nozzle’s outer sidewall and a matching slot is provided in the casing. A detailed study is performed to optimize this anti-rotation feature to reduce high thermal-mechanical stress and thereby improve reliability. The low cycle fatigue life is one of the vital requirements in improving reliability. The low cycle fatigue life of the optimized anti-rotation feature is validated using the finite element analysis. This paper describes the process step details in optimizing the anti-rotation feature.

The energy industry is committed to support sustainable development, balancing environmental, social and economic benefits. Turbomachinery products, in particular gas turbines, have not only to overcome the barriers imposed by: performance, lifetime and costs requirements, but to be more environmentally sustainable. The goal of this work is to integrate quantitative analysis of sustainability, based on Life Cycle Assessment (LCA), with company costs assessment methods, to provide a new multicriteria optimization methodology. This has been applied to the single components of the gas turbine and has shown that the Second Stage Low Pressure Turbine (LPT) Case can be sourced from different suppliers, reducing both: the costs of supply and the Greenhouse Gases (GHG) emissions. The LCA analysis provides also an environmental characterization of materials, machining operations and coating processes, which are necessary to realize the gas turbine parts. The findings allow to compare conceptual design alternatives of gas turbines, according to the Design for the Environment principles and can be extended also to other industrial sectors.

Nowadays the Energy Industry and Industrial Power Plants are committed to support sustainable development balancing environmental, social and economic benefits. Turbomachinery products, in particular gas turbines design, have to overcome the barriers imposed by: performance, lifetime and costs requirements. A new approach based on Life Cycle Assessment (LCA) is needed to define the correlation between carbon footprint and costs for different materials, manufacturing processes and production regions. To develop a decision-making tool to design sustainable products in the gas turbine sector high quality data are needed to model what is the impact of: materials and operations. Manufacturing operations (like forging and casting) and machining operations (like drilling, milling, turning, together with coating operations) are taken into account in this study. These processes have been customized to model the processes of the real supply chains used in Baker Hughes to build up a database, which is more focused on gas turbines, respect to the ones which can be found in the commercial LCA databases.

The Power Sector is undergoing a rapid technological change with respect to implementation of low carbon technologies. The IEA Energy Outlook 2017 shows that the investments in Renewables for the first time are equal to those on the fossil sources. It is likely that the conventional gas turbines and internal combustion engines will need to be integrated in systems employing biofuels and/or CCUS (Carbon Capture Usage and Storage). Also, the European Union is moving rapidly towards low carbon technologies (i.e. Energy Efficiency, Smart Grids, Renewables and CCUS), see the Energy Union Strategy. Currently 28% of the installed power capacity in Europe is based on natural gas plants. Gas-based power capacity has reached 418 GW in 2016 and is likely to continue to grow in the future. To efficiently capture the carbon dioxide emissions generated by the combustion of natural gas in the combustion chamber a possible solution could be to adopt new combustion processes, like Chemical Looping Combustion. The combination of CLC and GTs can decrease the efficiency of a combined cycle power plant from 60% to about 40.34%. These performances influence costs and environmental burdens and this is also the same for oxyfuel combustion, which is a competing technology to realize CCS. This paper, starting from literature mass and energy balances of a conventional combined cycle, a combined cycle coupled with chemical looping combustor and a combined cycle coupled with oxyfuel combustion, calculates the reduction of CO2 emissions which can be achieved during the whole life cycle of the power plant and then identifies the value of the carbon credit which is needed to have an interesting payback period for such kind of investment.

Gas Turbine shroud is a static component, which forms the outer flow path surface and sealing clearances to turbine blade tip. It also protects the casing from hot gases ingestion and radiation. Shrouds are segmented circumferentially to accommodate the large thermal gradients. The sealing between adjacent segments and the hook clearances play an important role in controlling hot gas ingestion and loss of efficiency. Heavy duty engine shrouds are typically bulky and machined from either forged ring or investment casting. They have tight tolerance-controlled hooks and hence controlled clearances with casing. It incorporates intersegment seals to control leakages between adjacent segments. On the other hand, Aero-derivative shrouds are typically thin and sheet metal fabricated. Tight tolerance control is not possible in sheet metal hooks and use of intersegment seal is also not feasible in these thin structures. Hence both the design features and approach to address sealing criteria will be different. In this article, it presents the challenges like manufacturing constraints and life requirements and the optimization study that was performed to meet the sealing criteria considering these challenges.

Industrial gas turbines (GTs) have advanced and numerous changes in both use, materials employed and design boundaries have occurred. The constraints aimed at lowering NOx emissions for improving the footprint, have driven designers to increase the firing temperatures and to look for improved cooling systems of GTs nozzles. These factors led to more severe operating conditions for hot gas path components and to the need for more accurate and comprehensive thermo-mechanical models for life assessment purposes. Within this context, a Lemaitre-Chaboche viscoplastic model has been coupled with a modified θ-projection creep model for MAR-M-247 material to account for steady-state creep effects in a finite element transient analysis (FEA). These material models have been applied on a cooled, first stage nozzle for a recently developed high-efficiency gas turbine. A verification assessment has been performed on a overfired, off-design transient analysis. The viscoplastic model developed showed the capability of predicting an accurate initiation zone of cracking. The FEA employing the captured inelastic behaviour predicted a high stress state in the location where an experimental crack nucleated. Furthermore, the model demonstrates the capability of using the Lemaitre-Chaboche plastic model coupled with the θ-projection creep model to predict reasonable inelastic strains for the entire lifetime of a gas turbine.

Nowadays a preliminary evaluation of environmental impact of a new product becomes more and more important, especially when the case study refers to an industrial gas turbine both for power generation and mechanical drive applications. The environmental impact evaluation, as well as the preliminary lifecycle cost analysis, will represent a critical driver to develop a competitive product during the conceptual design phase where the engine architecture is an outcome of different alternatives trade-offs. Scope of the following paper is the presentation of a set of Design-for-Environment considerations obtained through gas turbine functional decomposition in modules, identification of the most critical, assessment of their contribution compared to the whole engine in terms of environmental impact as well as the effect on the engine use depending on ambient and operating conditions. The outcome of this study is an approach to preliminarily evaluate the engine life-cycle impact as well as a set of indications to drive machine architecture, material selection and production processes towards the sustainability during manufacturing and operational phases.

Low cycle fatigue tests have been performed at 1038 degrees C on equiaxed MAR-M-247 under a mean compressive strain. Strain ranges assessed were 0.4, 0.6 and 0.8%, with this test program reflecting industrial gas turbine duty cycles. Fractographic analysis demonstrated transgranular crack propagation with intergranular fast fracture. Heavily oxidized secondary cracks were observed throughout. The details of a Lemaitre-Chaboche constitutive model that has been applied to the experimental stress-strain response are described. It was found that this model was capable of capturing both plastic shakedown and kinematic hardening effects with a high degree of accuracy (R-2 up to 0.997 and SSE up to 6E + 4). The suitability of extending this model to address different strain histories are detailed.

Nowadays a preliminary assessment on environmental impact of a new product is becoming more and more important. It is useful for a designer to access to a comprehensive methodology that supports configuration assessments taking into account the whole product lifecycle from the beginning of conceptual phase. To develop a competitive product, and particularly a gas turbine, each design trade-off needs to be performed considering not only the typical parameters such as performances, life and costs but also the cradle-to-grave environmental impact. Scope of the following paper is the application of design-for-Environment methodology to different architectures of GT compressor rotor module. Three design alternatives are analyzed and compared in terms of ELCA considering their design, material selection, manufacturing process and operating life. Specific considerations are proposed as a result of the combination of traditional design practices with environmental assessment. This study highlighted that number of parts, weight and amount of material removed or scraped that is, in other words, the level of production process optimization, are the key factors to control the environmental impact of a product.

Nickel-based superalloy MAR-M-247 creep curves obtained from constant stress testing have been analyzed within a modified Evans-Wilshire theta projection approach. Model parameters have been optimized to cover a range of stresses and temperatures. Experimental range of temperatures and stresses was 150, 190, 220 and 250 MPa at 870 degrees C; 80, 100, 120 and 140 MPa at 980 degrees C; and and 50, 70, 90 and 110 MPa at 1038 degrees C. This approach predicts the onset of tertiary creep and estimates the stress rupture life under temperature/stress conditions characteristic of gas turbine components. The creep parameters for the modified approach are a function of stress and temperature and once fitted allow the creep strain to be predicted up to the onset of tertiary creep stage with an R-2 accuracy of 0.85. The developed creep model is compared to a Norton-Bailey approach to demonstrate the current model's ability to formulate a criterion capturing the onset of tertiary creep.

The requirements for cleaner energy have driven industrial gas turbines manufacturers to increase firing temperatures and improve cooling of nozzles. The application of high temperature alloys having adequate thermo-mechanical requirements is critical, as assessed by low cycle fatigue performance. The effect of higher firing temperatures combined with higher cooling efficiencies has lead to operating cycles where the level of plastic strain imparted define component life. The capability of material models to account for non-linear effects such as ratchetting or shakedown, cyclic hardening or softening as well as Bauschinger or relaxation effects have been highlighted in this context. Neglecting these effects can lead to over and under-conservative life assessment analysis, while accounting for them using standard multilinear material models lead to convergence issues in finite element analysis. In this paper, Chaboche viscoplastic model has been applied to a transient structural of a first stage gas turbine nozzle. Fitting of the model based on experimental mechanical test data on MAR-M-247 alloy will be described, followed by an overview of how the model may be implemented to a benchmark nozzle thermo-mechanical transient analysis. Finally the details how the Chaboche-type model has provided up to 50% decrease in computation time when compared to using a standard multi-linear material modelling approach.

Some of twin shaft gas turbines models of GE are equipped with Variable Area Turbine Nozzle (VATN), also called Nozzle Guide Vane (NGV) as the first stator stage of Low Pressure Turbine (LPT). By varying the throat area, VATN controls the. energy split between the High Pressure Turbine (HPT) and Low Pressure Turbine, allowing higher operational flexibility and higher efficiency at partial load/speed. This flexibility is an important requirement for gas turbine in mechanical drive applications.This paper is focused on the design, development and optimization of a numerical Finite Element (FE) model of the kinematic chain implemented to actuate the variable area turbine nozzles, in order to evaluate the required force as input to size and design the actuator. The kinematic chain is composed of an arrangement of linkage components that transfer the load provided by the actuator to the VATN and achieve a desired rotation of VATN airfoil around its axis. The load provided by actuator has to balance the aerodynamic load taking into account the contribution of friction developed inside the kinematic chain. The FE model has been specifically developed to evaluate the effects of different parameters, such as manufacturing tolerances and assembly clearances, in terms of total actuation force requirement, stress/life of the components and friction distribution.The additional scope of the detailed FE model is to represent an analytical validation criterion of the results obtained through a simplified spreadsheet-based tool which aims to be a reliable and quick responding system both for new product design phase and for implemented fleet issues resolution.