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Accepted Presentation Abstracts

The following Presentation Abstracts have been accepted for presentation at the AMRGT Symposium. Review the advanced manufacturing and the repair track accepted abstracts.


Design, Development, Testing and Validation of and Improved Lower Emission Additively Manufactured Combustor Pilot Nozzle for F Class Industrial Gas Turbine:
Gregory Vogel, PSM

Emerging additive manufacturing technology offers many opportunities for improved design in gas turbine components by enabling optimization of parts that are not manufacturable with conventional methods. The combustion components, for example, require complex fuel and air circuits to achieve best possible mixing and oxidation process for the lowest emissions possible. Thanks to the additive manufacturing, new combustor parts are making a break thru for improved capabilities in fuel flexibility and operating conditions. Also, quick turn around and modularity makes additive manufacturing a key enabler for fast validation of design concepts.

This technical presentation will describe the application of additive manufacturing technology in an F class industrial gas turbine including design, development and validation steps of a combustor pilot nozzle. A systematic design approach was undertaken to examine all aspects of combustion operation and testing, down-selecting the appropriate design, material and to productionize. Experiences gained from other AM production parts as well as testing coupons were leveraged to ensure a robust production process. Combustion atmospheric rig testing was conducted to validate emissions performance. Detailed thermal and structure analysis were performed and validated with testing experience.

The new design demonstrated a benefit in reducing by half the emissions in start-up emissions as well as improved combustion stability. In addition to the operability benefits, about 1/3rd reduction in cost of the production assembly was realized. A main cost advantage gained with the utilization of additive manufacturing was the reduction in part quantity from 7 individual components down to 1. Constraints typical of conventional manufacturing methods were avoided with the implementation of innovative geometries only achievable by additive manufacturing. In addition to combustor component reduction, the additive process was also leveraged to reduce the total number of fuel circuits in the combustion system, making the installation and control logic more straightforward.

Several sets were successfully installed in customer's engines, benefiting from an improved combustor pilot nozzle. Detail of the design and development steps as well as the results of combustion tests will be presented and discussed. It shows that with proper considerations of the additive manufacturing technology, very quick turn-around of improved combustions solutions implementation can be achieved: less than a year from development to production!


Design and Manufacturing of Micro-Turbine Recuperators With Advanced Additive-Manufacturing Techniques for Aerospace and Power Generation Applications:
James Zess, MCHX Technology

Gas turbine companies continue to focus on designing engines with reduced levels of fuel burn per unit power. With the operational demands in the rapidly growing general aviation, high-altitude drones, range extenders for hybrid-electric vehicles, and renewable energy sectors, it is recognized that high power density microturbines have many advantages, including fuel efficiency, fuel flexibility, low noise, low emissions, low maintenance, lightweight, and high reliability over other power plants. One way to increase the efficiency of a conventional gas turbine Brayton cycle, especially in microturbines, is by recovering the engine exhaust gas waste heat before it is released to the environment. A heat exchanger, also known as a recuperator, recovers heat from the engine exhaust gas to increase the temperature of the compressed air before combustion. As such, the amount of fuel that is required to reach the final combustion temperature is reduced. Thermodynamic cycle efficiency, and therefore fuel consumption, is directly proportional to the thermal effectiveness and pressure drop of the flow across the recuperator.

Despite many attempts, the recuperated cycle concept capable of meeting the size and weight limitations, aerothermal performance, endurance, and reliability has never been successfully implemented in aviation gas turbines. The challenging criteria needed to be met in the recuperator design for microturbines are largely the minimal pressure drop and maximum heat transfer effectiveness across the air and exhaust streams with minimal weight and size. Other challenges include structural integrity and flow leakage due to external forces imposed by severe flight maneuvers, and engine layout. In addition, improper positioning of the recuperator in a gas turbine could reduce the expansion ratio of the last turbine stage, hence limiting the turbine work coefficient and negatively impacting the engine performance. Higher recuperator thermal effectiveness either requires more exchange surfaces, resulting in a larger recuperator size, or higher heat transfer coefficients, which may result in a higher pressure drop. In general, microturbine recuperators are required to be compact and lightweight, highly effective in transferring heat with low-pressure fluid pressure drop and be manufactured at reasonable costs.

To that end, MCHX Technology has developed an ultra-compact micro-channel heat exchanger to provide highly effective heat transfer for a high thermal efficiency microturbine that is designed by Turbine Aeronautics. MCHX recuperators consist of assemblies of thin plates of high-temperature materials, such as stainless steel and Nickel-based alloys for stationary power generation, or lightweight Titanium and ceramics for aviation and transportation applications. The microchannel structures have been traditionally chemically etched or machined into each plate. These traditional chemical and mechanical manufacturing methods were considered for this design, but they are difficult and costly as a large percentage of the expensive alloy is lost during manufacturing. Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) has recently developed a three-dimensional metal screen printing fabrication process that is very well suited for large volume production of flat metallic or ceramic parts with high aspect ratio structures. This additive manufacturing technique has been applied to the MCHX recuperator plates to print geometrical accurate microchannels and provide significant saving in manufacturing costs.

This paper will first present the thermodynamic goals and layout limitations for compactness and weight in microturbines, with an emphasis on an aviation and a land-based microturbine. The recuperator design for traditional manufacturing methods differs from those designed for additive manufacturing. The IFAM manufacturing technique, that differs from the widely-known direct metal laser sintering (DMLS) will be explained. Practical limitations of the DMLS in microchannel recuperator manufacturing such as porosity, structural integrity, and fatigue life, especially in the context of gas turbines, will be discussed. The MCHX material selection and design with the IFAM additive manufacturing technique will be presented after that. In addition to the topics of de-binding, sintering and diffusion bonding, all being carried out in one operation, the effectiveness and pressure drop results will also be discussed in the full paper.


Long Term Exposure and Evaluation of Am Haynes 188:
Vamadevan Gowreesan, Sulzer

Additive Manufacturing opens opportunities to fabricate various replacement parts for turbo machinery repair. However, the response of the material to heat treatment and long-term thermal exposure may not be same as that of a conventionally processed wrought or cast component, of the nominally same alloy. Lack of such data for specific alloys could prevent us from fully utilizing the potential of additive manufacturing for the fabrication of high-performance turbo machinery components.

Haynes 188 is a Cobalt based superalloy commonly used in hot section of gas turbines. However only limited information is available in the literature on additively made Haynes 188. To address this, Sulzer performed an internal study on additively manufactured Haynes 188. This presentation discusses the results of the study.

The study consisted of three main tasks. The first task was to evaluate the response to heat treatment of AM Haynes 188 and to determine the optimized heat treatment. The second task was to generate mechanical properties of the optimally heat-treated samples. The third task was to subject some optimally heat-treated Haynes 188 AM coupons to long thermal exposure and then to evaluate them. The evaluation included testing of mechanical properties and metallurgical changes due to the long-term exposure. In addition, the response to the long-term exposure of conventional, wrought Haynes 188, was evaluated and compared with that of the AM coupons.


Modelling Techniques for Selective Laser Melting Technology:
Grzegorz Moneta, Lukasiewicz Research Network – Institute of Aviation

Selective Laser Melting (SLM) is driven by the need to manufacture multi-functional and complex components with high structural integrity and extended lifetime.

Because of the large energy density of the laser beam, problems like balling, high residual stresses and deformation occur. Elements processed by SLM often present imperfections which influence key properties, such as tensile yield strength, elongation, strain-to-failure, etc. Laser power, scan speed, hatch spacing, layer thickness, scanning strategy, powder material properties and chamber environment are the key SLM parameters, which can be the cause of defects such as keyholes, pores, lack of fusion holes, and cracks, in case they are improperly chosen or involuntary affected during the process.

In the turbomachinery industry, SLM is receiving more and more interest to produce complex, multi-functional and lightweight parts. The inherent presence of defects in SLM components has a significant impact on their reliability, durability and performance. Understanding of behaviour and ability to predict the state of SLM parts plays a key role in implementation of this manufacturing technology.

The presented work shows practical cases of numerical modelling and prediction of key challenges highlighted above: distortions, porosity, microstructure properties and residual stress distributions. Having validated models, the simulations can be iteratively repeated to determine optimum parameters, which will improve performance and fatigue life of parts. Additionally, development of manufacturing strategy, process parameters and numerical models can be aided by Artificial Intelligence to further reduce time and cost of implementation of SLM technology.


Static Load Characteristics of Additively Manufactured Hybrid Thrust Bearings: Measurements Versus Predictions:
Keun Ryu, Hanyang University

Process fluid turbomachinery implements hybrid fluid film thrust bearings, combination of hydrostatic and hydrodynamic to support axial load and control axial shaft motions. Hybrid fluid film bearings offer significantly enhanced durability with very low friction and wear while providing accurate rotor positioning as well as large load and static stiffness characteristics even working with low viscosity liquids.

Additive manufacturing allows cost-effective and time-saving fabrication for turbomachinery component testing and performance measurements. The current work aims to evaluate the static load performance of 3D-printed hybrid bearings lubricated with a compressible fluid. The test bearing, fabricated using Fused deposition modeling (FDM) technology and embedded with onyx and ~35% carbon fibers, has flat surfaces with inner and outer diameters equal to 63 mm and 145 mm, respectively. The bearing has uniformly distributed eight pockets on the bearing circumference with 90 mm in mean diameter, 20-degree in arc length, and 0.51 mm in depth. The simple component-level bearing test facility allows to test and evaluate the current bearing design with various load and fluid property conditions. The measured bearing static load characteristics are quite similar to the bearing fabricated with a subtractive manufacturing process. The measured static load performance of the test bearings is compared to experimental data.

The current predictions use measured bearing geometries and actual operating conditions. The future work accesses the feasibility of direct metal laser melting (DMLM) technology in the fabrication of complicated hybrid fluid film bearings with high load capacity and damping capabilities for cryogenic turbopumps in reusable and low-cost rocket engines. Experimentally validated predictive bearing models significantly reduce time and expenses in further developments of hybrid cryogenic bearings, and aid to reduce the variability in identically constructed test bearing units while also certifying their scalability.


Evaluation of Abd®-900am for Gas Turbine Additive Manufacturing & Repair:
John Shingledecker, Electric Power Research Institute

Most studies on the application of additive manufacturing (AM) of nickel-based superalloys for gas turbine hardware utilize traditional material compositions. In this work, the Electric Power Research Institute (EPRI) is evaluating a new alloy, ABD®-900AM, which was specifically developed for combined 'printability' as well as high-temperature performance.

Prior EPRI research on gas turbine guide vanes produced by Laser Powder Fusion Bed (LPFB) processes showed good tensile and fatigue behavior but significant debits in time-dependent creep strength reductions compared to traditional casting.

Detailed microstructural analysis on long-term creep tested samples identified specific microstructural features including grain size and carbide size and distribution which appear to be the source of the loss of long-term performance.

Thus, the focus of this work was to understand how process selection and post-process variables effect microstructure and high-temperature time dependent creep performance in ABD900AM with a focus on high-temperature applications with the potential for component repair and replacement.

Specifically, EPRI is evaluating both LPFB and Electron Beam (EB) processes and multiple sub and super-solvus heat-treatments. ABD900AM was selected for this study since it has demonstrated superior printability and repair potential for LPFB processes.

The EB process has the potential to grow 'directionally solidified' (DS) type structures which are known to improve creep performance. To date, creep tests have been conducted on 5 different processing and post-processing conditions showing a significant variation in microstructure and creep performance.

This talk will highlight the findings to date, comparisons of microstructures and data with traditional cast blade and vane materials, and provide a prognosis for future AM applications in gas turbine hot-section components.


A Simple Cost Model to Drive Design for Additive Manufacturing:
Timothy W. Simpson, Penn State University

Designing for additive manufacturing (AM) is as much about maximizing the value afforded by layer-wise fabrication processes that AM provides as it is about minimizing the costs associated with them. While our understanding of Design for AM (DfAM) has matured rapidly over the past decade as software tools and methods have evolved, we still struggle to translate this into direct economic benefit, which is key to successful implementation of AM.

In this talk, I will introduce a simple cost model for metal AM, specifically laser powder bed fusion, that can help drive DfAM decisions and enable DfAM trade studies. Despite its simplicity, the simple cost model provides a guide to identify profitable pathways to AM. If none of those pathways are immediately profitable, then the cost model provides insight into when the part will become viable as other economic factors (e.g., material costs, machine cost) or technical factors (e.g., laser powder, number of lasers) fluctuate in the market.

An example from an industry training exercise will be discussed to demonstrate application of the costing guide to achieve a viable AM part when using DfAM. The example also illustrates how DfAM is the “value multiplier” for AM, helping to achieve a profitable AM part faster and with more control than waiting for powder costs to come down or and machine prices to fall.

Generalizability of the costing guide to other AM processes will also be discussed.


Novel Ultrasonic Based Technology for Support Removal and Post-Processing for Additive Manufacturing:
Tomasz Choma, AMAZEMET

One of the most important steps in AM besides the printing itself is post-processing. Complex geometries often require a large number of support structures that may be problematic to remove mechanically after the printing process. This issue limits the design possibilities and highly increases the production cost of each part.

Automated support removal platform uses chemical etchants with ultrasonic agitation to dissolve support structures, remove leftover or not fully melted powder reducing the roughness of the surface, and penetrate inaccessible areas. The process is simple and does not require any additional wiring or set up of elements in the reactor. The system allows for quick support removal of multiple elements at the same time, thus it highly reduces the processing cost and time for each part in the manufacturing chain process.

The safeEtch allows users to automatically remove supports without mechanical treatment and polishes surfaces even in places inaccessible with classical tools. Technology is based on chemical reactions accelerated with high-intensity ultrasounds. Mass production with SLM/PBF/DMLS is often limited to a single layer of printouts while stacking has been an advantage of EBM technology. With safeEtch it is true no more. Having an effect of dissolvable supports we can freely stack multiple elements in the Z-axis without worrying about time consuming post-processing.


Applied Materials Corrosion:
lance Scudder, Applied Materials

Applied Materials specializes in solving exceptionally difficult materials engineering challenges in a high-volume manufacturing environment. Our solutions include coating deposition and removal, automation software, and metrology for productivity & performance.

Applied Materials has developed and commercialized a variety of barrier coatings for a range of end-market applications. Here, we demonstrate novel barrier coatings developed for the semiconductor industry that have applicability for aerospace & land-based gas turbine engine applications.

The barrier coatings described have several unique properties, including a high degree of conformality, the ability to coat blind passages, and significantly reduced corrosion rates on superalloy substrates. Applied Materials coatings are significantly thinner than an oxide scale at the spallation thickness threshold of 5-10 μm, so the coatings have minimal material impact on weight and geometric tolerances of finished components.

Applied Materials has developed a CVD deposition process that overcomes several process limitations of other corrosion protective coatings. The process results in a highly conformal coating at both the macro and microscale. In this presentation we will demonstrate coating the exterior and interior of a turbine blade with a 40:1 aspect ratio and a fully blind “U” turn. Coating thickness variation is less than ±13% on the interior of the component. In addition, the coating is able to conformally coat rough surface topology typically seen with as-cast or 3D printed surfaces.

We tested coated and uncoated CMSX-4 (SLS) nickle superalloy in high temperature Type I hot corrosion at 900 °C in air, with a deposit of a eutectic mixture of MgSO4-Na2SO4 salts. In this presentation, we detail mass change, optical top view and SEM cross-section characterization of samples used during corrosion testing. The overall time to failure is at least 2.5x longer with the Applied Materials coating vs. uncoated nickel superalloy.

Working with AERO OEM and MRO industry partners, we have successfully demonstrated application of this unique corrosion resistant coating in manufacturing integration testing with AERO turbine blades for use in aircraft engine hot sections.

Additive Manufacturing for Hybrid Repair of Turbine Components – a Review:
Dheepa Srinivasan, Adjunct Faculty, IIT, Ropar

Tremendous developmental efforts have gone to establish Additive manufacturing (AM) route ./as unique and viable solutions for repair applications, in gas turbines. Examples include, turbine blade tip and platform repair, seal teeth repair, structural casings and bolt hole repairs, vane coupon replacement and many others, including development of directionally solidified or single crystal blade repairs.

In particular, it is attractive to use the technology as a hybrid solution during repair, either by direct part restoration or by building specific sections or coupons and by joining them via welding or brazing techniques. The structural integrity of these hybrid joints (having AM on conventional manufactured parts) is addressed via this review, via different examples of utilizing AM as a unique enabler for gas turbine repair applications.

The microstructure in the transition zone plays an important role in the joint mechanical behavior and long term stability. Examples include AM CoCrMo, SS316L, AlSiMg, and Ti64 alloys. The role of residual stresses, testing at small scales and the key challenges associated with hybrid manufacturing, will be addressed to bring out the true potential as a solution for repair and refurbishment for gas turbine components.

Long term stability of the hybrid repair will also be addressed in this review.


Recrystalization of Rene N4 and N5:
Hans Van Esch, TEServices

Recrystallization of equiaxed, directionally solidified and single crystal casted nickel base superalloys can occur during manufacturing and repair processes. While equiaxed, and to a lesser extent, directionally solidified casted nickel-based superalloys have grain boundary strengthening, this is nonexistent for single crystal superalloys. Therefore, it is especially important to avoid or limit recrystallization during manufacture and repair of nickel based single crystal gas turbine components.

This presentation provides the results of the study performed by EPRI, TEServices, MD&A and Sulzer concerning the effect of recrystallization when compressive stresses are introduced during manufacturing and repair processes (grit cleaning and shot peening) when followed by (full solution, partial solution and stress relieve) heat treatments of Rene N4 and N5.

This study concludes that for both single crystal alloys, Rene N4 and N5, introduction of less compressive stresses during manufacturing and repair, and a lower temperature exposure during follow up heat treatments, results in a lower recrystallization layer depth.

Note this study is part of EPRI study to be able to repair new design, AGP, components by development of stripping and re-application of the coating systems and inspection methods such as flow testing, to ensure that coating and cooling systems are properly functioning. The base materials of the AGP components are comparable to the older design and this allows repair methods developed for the older design to be used with exception to the Stage 1 Buckets (S1B). The F7FA AGP S1B are made from the single crystal nickel-based superalloy Rene N4 (note: F7FB S1B were made from Rene N5).


Data-Driven Remaining Useful Life Estimation for Predictive Maintenance of Gas Turbine Engines:
Giorgos Protopapadakis, Aristotle University of Thessaloniki

In predictive maintenance the schedule is planned based on the actual condition of the asset, and its life projection to the future. In order to implement predictive maintenance, the remaining useful life must be computed. An approach to do so, is via data-driven modelling. The reason behind predictive maintenance, is that a suitable maintenance schedule can reduce significantly the maintenance costs and use of material, by increasing the availability and the reliability of a gas turbine.

The objective of this work is to create a remaining useful life prediction model for gas turbines based on data-driven approach. Data-driven models rely on existing information analyzed using data-analytics. That be simple statistics or artificial intelligence. The benefit of this method is the exploitation of all the available data acquired by operators from the onboard sensors through the diagnostics system.

For this work an open-source database is used. The dataset is composed by virtual sensor measurements, computed through a thermodynamic model for a given turbofan engine. First the necessary data pre-processing is done, taking into account data corrections with respect to operating conditions. Noise reduction is performed via averaging methods such as moving mean average. Then feature selection takes place, based on the correlation matrix and the utility of each sensor for describing the physics of the problem.

The selection of algorithms tested is based on literature review. The selection of their hyperparameters is done using grid search and numerical optimization. The results are evaluated according to the guidelines provided by the authors of the dataset, more specifically, root-mean-square error (RMSE) and a given evaluation function.

An outcome of this work is the comparison between the methods considering both their evaluation score, and their training computational cost. The model is used to better predict the future condition of the engine and help assess the necessary actions that must be done for maintenance and repair in near and long-term future. This allows the optimization of the planification, which in its turn increases the availability. Importantly, it is possible to assess the condition of a component before the inspection, and thus focus on components that are predicted to be more degraded.


Digitized Repair Process Chain – Communicating the Scan Requirements:
Sophie Babette Rees, Siemens AG

Many service offers for the repairing of damaged gas turbines parts are still handled like individual cases with an respectively high amount of manual operation, communication and handling. This is notable in the acquisition of information for the worn-out parts, the requirements definition for the scan order, the manual creation of the toolpaths and the data handling along the whole process. Every process step requires a lot of communication and exchange of data between the involved employees. Further there is no tracking of the parts, just very rare documentation about the repair process of the single component and data distributed in different systems. An overview about the repair process of a certain type of component is missing and therefor it is difficult to improve and scale the repair process. A comprehensive digitized repair process chain, the therein given possibility to automate the process and a centralized documentation of all repair processes have a great potential to save resources and time.

This paper proposes as a first step a method to communicate the scan requirements for a component in a formalized and digitized manner. The aim is to facilitate the communication between engineering and the scan operator and to document the requirements at the same time. The method is based on the result of interviews with different departments who work with the scan data. The requirements can be split into 3 different categories: formal information about the scanned part, the regions on the part to be scanned and further specifications for the scan. The method can be realized with a digital questionnaire, which allows the operator based on the answers to choose the right scan strategy, to scan the necessary areas and to store it on the requested location.

Because all involved departments work within the CAx-environment and are very familiar with it, it is an adequate place to include the method there. To overcome the problem of different CAx-Versions of NX (in the different remanufacturing sites) we made use of the cloud-based CAx-environment Nx 2Go. This cloud-based, pay per use CAx-solution allows access from all internet connected electronic devices and can be easily entered from the shop floor or the field, wherever the scan of the component should be realized.

As a next step it is planned to define scan specific features, like Product and Manufacturing Information (PMI) for GD&T, to facilitate the handling of scan data within the CAD-System.


A Primer on Reverse Engineering of Gas Turbine Components for Repair and Aftermarket Source Part Manufacture:
Justin Kuipers, Liburdi Turbine Services

This presentation will provide a primer on the opportunities and challenges of reverse engineering as it pertains to both repair and aftermarket source part manufacture. The availability of gas turbine components is of critical importance for operators' bottom line. With industry consolidations, obsolescence of legacy plants, and global supply chain upsets, the availability of components has never been more unsure.

Reverse-engineering of gas turbine components is a possible process to address these needs directly for operators, or, as a business opportunity for third party service providers and even OEMs. Successfully reverse engineered components can provide cost savings and/or alleviate limited supply chains. But before starting the processes, it is crucial to understand the key characteristics of a component, its production processes and the various costs and lead-times involved. Fortunately, the repair industry already has many of the skills needed.

Traditionally, the repair industry has utilized reverse engineering as a means of understanding a gas turbine component's design to address the repair needs and implement upgrades as appropriate. Discussion will cover options for reverse-engineering data collection and data reduction techniques. It will explain the importance of modelling, stress analysis, tolerances and damage modes to producing a viable and durable part. Selection of appropriate alloys and coatings as well as cost-effective production processes will be discussed.

Last but not least, business-planning, supply-chain management and manufacturing flow will be explored. It will be shown that, with the right timing, support and investment, reverse engineering can reduce the risks and costs to operators associated with parts replacement and provide a business opportunity in the segment.


Automated Digital Blue Light Scanning Inspection of Gas Turbine Parts:
Kamel Tayebi, GE Power

Blue light scanning (BLS) inspection is gaining ground in the turbomachinery manufacturing world as a key component of digital manufacturing. The General Electric Manufacturing & Technology Center (GEMTEC) is GE's largest repair facility located in Dammam, Saudi Arabia. This presentation describes GEMTEC's* experience with automated robotic BLS and specialized manual BLS investigations to digitally inspect gas turbine parts and assemblies for fast and accurate repair screening and for repair quality control.

The key features of our blue light scanning inspection process are:

  • Digital
  • Non-contact
  • Non-destructive
  • Highly Accurate
  • Covers the entire surface of the part (for future utilization)
  • Repeatable
  • Reproducible
  • Auditable
  • Automated
  • Fast
  • Efficient

We discuss relevant points related to machine set up, part preparation and process optimization as well as the impact on the repair process as we move away from manual inspection. This discussion is made in the context of GEMTEC’s wide and varied portfolio explained here briefly.

GEMTEC supports the power generation, oil and gas, and water needs of Saudi Arabia, the middle-east region and serves more than 70 customers from 40 countries around the world, including large fleet operators such as the Saudi Electricity Company, ARAMCO, and ENGIE to name a few. In serving this massive gas turbine hub, GEMTEC specializes in the following repairs:

  • Fr5, B&E, 7F/9F combustion inspection and repair
  • Fr5, B&E, 7F power nozzles and shrouds inspection and repair
  • Fr5, B&E, 7F/9F gas turbine rotor inspection and repair
  • Fr5, B&E, 7F/9F bearing inspection and repair
  • Fr5 and B&E turbine blades inspection and repair
  • Generator rotor inspection and overhauling
  • Legacy Alstom Fr9/Fr11D Combustion
  • Rotor life extension


Automated Turbine Blade Repair Planning and Execution:
Joerg Seume, Leibniz Universitaet Hannover

The authors' team has devised an Automated Turbine Blade Repair Planning and Execution system which measures 1st stage turbine blades' geometry during inspection creates a digital twin of the blade, and then automatically decides which of several repair (e.g. braze cracks or single crystal weld repair) options to apply. The decision is based on a comparison of the impact, which the repair options have on engine performance and life. This comparison is in turn based upon reduced order models of the engine, which include predictions of roughness-dependent aerodynamic performance, fracture mechanical prognoses of crack propagation, and many other analyses.

A demonstrator set-up in the machine tool laboratory connects the analysis cells (e.g. multi-scale geometry measurements) with the repair cells (e.g. single-crystal welding, milling, among others) through a flexible transportation system in order to guide the part through the cost-optimized logistical sequence. Programming and building the demonstrator shows that the automated process is possible. It also brought to light remaining challenges in implementing this process in industry. The paper will discuss these challenges and the path towards their solution will be discussed in the paper. The presentation will include a movie demonstrating the material flow and work flow as well as the processes involved and already automated to date.


Data-Driven Digital Twins for Predictive Maintainance of Gas Turbine Hot Operation Components:
Jaroslaw Szwedowicz, Siemens Energy AG

Accurate prediction of the Remaining Useful Life (RUL) is a crucial task for the economical operation of rotating equipment in power plants, such as gas turbines. For the life cycle prediction of hot components in a gas turbine, computations are performed using a high-fidelity Finite Element Method (FEM). The FEM leads to infeasible computational requirements under real-time constraints. Therefore, for predicting the failures at critical locations and devising a predictive maintenance, a digital twin of each component can be developed by knowing both operational history and simulation data. A fast digital twin of a component of the engine can estimate the evolution of specific parameters and states for actual operating conditions. This allows for a more flexible reaction to service demand, than it would be possible by the initial design only, employing coded safety factors and pure assumptions about uncertainties.

These mechanical and thermal stresses as well as environmental damage mechanisms are not only transient, but also depend on the operational scenario. Furthermore, they are spatially distributed over the structure. This presentation describes two different case studies involving data-driven digital twins to predict stresses at critical locations in hot operation components of a gas turbine.

  1. In the first case study, there is considered the outer casing of a large gas turbine. A digital twin is developed to predict the stresses at critical locations of casing in terms of Low Cycle Fatigue (LCF). These stresses are primarily driven by secondary stresses and result from thermal gradient during start-up and shut down of the engine that are of interest of peaking operation regime. By utilizing the temperature data for such specific locations, for different ramp-ups and loading ratios of operation, the developed nonlinear dynamic ROM (Reduced Order Model) predicts the stress-induced damage in real-time at the chosen locations. These predictions help for making decision about the casing intervals.

  2. In the second case study, a novel approach is presented for combining static field meta-model of stress or temperature fields and dynamic (transient) reduced-order modelling technique to develop a 4-dimensional (4D) digital twin of stress evolution in a rotor-disc. For the modelling purpose, training data were obtained by performing multi-physics simulations using high-fidelity models for a few operating scenarios only. The 4-D ROM approach's advantage is to give new scenarios, transient temperature or stress fields. Then, these data can be predicted quickly with very low computational effort by applying this 4-D ROM.

A long-term outlook for this research direction is to have real-time condition-based maintenance of gas turbine components using a family of ROMs. This will reduce the service cost for the customers and be used to reduce the cycle time for engine upgrades.