bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations in the High-Temperature Creep Performance of Diffusion Bonds for sCO2 Heat Exchangers
Authors: Shingledecker John , Kumar Vikash , Bridges Alex 
Published: September 2023

Abstract
In support of understanding the long-term performance of high-temperature diffusion bonded heat exchangers for sCO2 power cycle application, a commercially produced alloy 316 diffusion bonded block was characterized and subjected to uniaxial creep testing in air at temperatures of 600 to 750°C with varying sample sizes with some tests durations exceeding 7,000 hours. The results show a range of different behaviors when comparing between samples sizes and in comparison to wrought alloy 316. At lower testing temperatures, some sample sizes did not meet average rupture life predictions while others did. At intermediate and higher temperatures, sample size effects were not as prevalent. While measured ductility was large for the standard and larger samples, unique observations from post-test metallurgical analysis identified non-uniform strain distributions leading to sample ovality. Additionally, failures occurred on the bond lines with oxidation potentially impacting longer-term and higher-temperature tests. Overall, these results demonstrate that careful selection of sample size and test conditions is required for engineering studies on diffusion bond performance to ensure a relevant assessment of component performance. Furthermore, the results show microstructural texture effects in the starting sheet may persist after diffusion bonding and therefore should be explored in more detail as part of future research. Finally, pre and post-test characterization suggest that procedures to quantify grain growth and bond-line features (voids and oxides) which are not measured using the standard acceptance tests may be needed for further advancement of the technology.
Numerical Analysis to Optimize and Study the Impact of Area Profiling on the Performance of a Rotating Detonation Engine
Authors: Raj Piyush , Meadows Joseph 
Published: September 2023

Abstract
Current gas turbine technology utilizes deflagration combustion, but an rotating detonation engine (RDE), if integrated successfully, has the potential to significantly increase thermal efficiency. The shock-laden RDE exit flow is highly unsteady and spatially non-uniform (hydrodynamically and thermally), with a high degree of periodicity. In contrast, gas turbines are designed to operate with relatively small velocity and temperature fluctuations at the inlet. The objective of the current work is to optimize and study the impact of area profiling in an annular RDE configuration. A computational approach is used to condition the flow within the RDE channel by strategically constricting the flow area to convert the unsteady supersonic/subsonic flow exiting the combustor into a relatively uniform steady flow with minimum pressure loss. In the current work, a 3D non-reacting optimization methodology is developed for the wall profiling of the combustor. The emphasis is to reduce the computational cost needed for design optimization. A Design of Experiment (DoE) study is conducted, and the geometry is parametrized for the constriction on the inner wall. It consists of a constant area section up to the detonation wave height, followed by a parabolic area profile (rapid reduction in area), and finally linear profile (gradual reduction in area) till the RDE exit. Three geometric parameters are varied, which include the length of the parabolic section, the area ratio at the end of the parabolic section (with respect to the constant area section), and the throat area ratio (with respect to the constant area section) at the exit. The output parameters include three primary indicators: equivalent available pressure (EAP), axial velocity unsteadiness, and circumferential velocity unsteadiness. The initial points in the DoE are coarsely populated, and an initial response surface is generated using the Kriging method. Next, the response surface is refined based on the adaptive sampling technique. Finally, design optimization is performed to determine the optimal design configuration that maximizes the pressure gain and minimizes the unsteadiness. A CFD simulation with constant area cross-section for pure CH4 with enriched-oxygen air is validated with experimental data followed by the validation of the rapid to gradual area reduction (RTG) profile simulation with experiments. The benefits of the RTG profile are compared with a constant cross-section area to delineate the impact of area reduction on flow uniformity at the exit of the RDE.
Application of Machine Learning for Prediction of Turbofan’s Airflow
Authors: Rejeb Sara , Duveau Catherine , Rebafka Tabea 
Published: September 2023

Abstract
For an improved control of the production process of aircraft engines, a new databasis has been built containing a huge number of geometrical characteristics of the engine’s parts as well as performance measurements obtained during the final acceptance test of the engine. The goal is to use these data to build a new prediction model of the performance that has high accuracy and detects drifts at an early stage of the production process. More precisely, we are interested in the prediction of the engine’s total airflow and data are mainly about characteristics of the fan blades and conditions of the test bench.
In this work we present the database and illustrate its specific characteristics like strong correlations among some of the features, missing values and general temporal drifts. In addition, we explore classical machine learning models to determine the relationship between fan blade production and the engine’s total airflow. In a second step we apply different time series models to better model the dependencies, such as ARIMA and LSTM, for the prediction of the airflow. It turns out that it is particularly difficult to disentangle the impact of the geometric measurements and the production drifts on the performance. This calls for methods that go beyond conventional machine learning models and that are specifically designed for our data.
Numerical Prediction of the Heat Loads on a Non-Reactive Test Rig for Combustor-Turbine Interaction by Using Hybrid RANS-LES Approach
Authors: Tomasello S. G. , Andreini A. , Bacci T. , Facchini B. , Cubeda S. , Andrei L. 
Published: September 2023

Abstract
In order to further improve gas turbine efficiency and performance and reduce NOx emissions, the ever-increasing employment of lean-premix combustors results in very severe, complex and unsteady conditions at the inlet of the first stage nozzle, introducing a possible alteration of the aerothermal behavior of the component. This is considered a recurring problem especially during the gas turbine engine design process and, for this reason, in the recent years, it has become an important and discussed topic in the framework of gas turbines design.
In the present study, an annular sector rig, made by a non-reactive, trisector combustor simulator and nozzle cascade, where both adiabatic effectiveness and HTC measurements had been carried out, is investigated by performing a systematic computational study by using a hybrid RANS-LES approach. Firstly, in accordance with the standard industrial design practice, a periodic configuration of the stand-alone NGV was created in order to evaluate HTC on the vane surface by performing RANS simulations and by using 1D profiles from the experiments as inlet boundary conditions. Then, in order to improve the accuracy and reliability of the prediction of the HTC on the NGV and of the flow field outgoing from the combustor, a fully integrated combustor-stator periodic domain has been investigated by performing a SBES simulation. Moreover, in order to carry out further analyses on the nozzle, in correspondence of the position of the interface plane between the combustor and the stator, a set of unsteady data have been extracted and stored from the fully integrated SBES calculation in order to generate realistic unsteady inlet boundary conditions for the non-cooled NGV configuration. In particular, the NGV has been then studied by carrying out RANS and SBES simulations as well by employing the k-ω SST and Transition SST to model the turbulence effects. Eventually, numerical results have been compared to the experiments in order to evaluate the discrepancies between different CFD approaches.
The comparison between numerical predictions and the available experimental results was exploited to assess the capability of advanced scale-resolving methods in the characterization of the mutual combustor-turbine interaction, along with the heat transfer coefficient behavior. This evaluation aims thus to assess if such more advanced and more time-consuming methods, including also turbulence models able to capture the transition, can be more reliably used for a proper prediction of the vane thermal loads.
Experimental Investigation of Synchronous Flow Induced Blade Vibrations on a Radial Turbine - Part 1: Nominal Inlet Guide Vane
Authors: Schafferus Markus , Sasakaros Marios , Wirsum Manfred , Zobel Arthur , Vogt Damian , Nakos Alex , Beirow Bernd 
Published: September 2023

Abstract
The service life of today’s turbochargers is limited among other things by the mechanical load caused by blade vibrations. In this context, the precise determination of the resonance operating points and the estimation of the vibration magnitudes are essential for an accurate assessment of the service life of the turbocharger components. Forced blade vibrations in radial turbines are primarily flow induced. Flow induced blade vibrations are caused by the nonuniform flow field in the circumferential direction which acts on the blades as a cyclic pressure fluctuation. Previous studies identified the inlet guide vane (IGV) as well as the spiral turbine housing as the primary sources of the non-uniform flow field.
In the present study a thorough experimental investigation of the synchronous blade vibrations of a radial turbine is performed. A detailed description of the experimental setup is given. In this setup the vibrations are captured with two redundant measurement systems during real turbocharger operation. Strain gauges, applied on certain blades, as well as optical tip-timing sensors distributed on the circumference of the turbine shroud are used. The advantages of the combined usage of these two measuring systems are shown in the paper.
Initially, the blade vibration modes are determined experimentally in stand still tests and numerically calculated through FEM models. This served for the creation of a Campbell diagram, which determined the speed ranges that are examined. The mistuning, which is not taken into account in the numerics, is therefore determined via the experiment. In addition, the experimental results are compared with those of numerics and the frequencies from standstill test. The first part of this two-part paper is focused on the vibrations caused by the “nominal” IGV. This “nominal” IGV has twice the number of blades compared to the rotor. Part 2 will analyze the changes of the blade vibrations due to the application of two different IGVs.
Development of Additive Manufacturing Gas Turbine Hot Gas Path Vanes at Baker Hughes
Authors: Cecconi Massimiliano , Giovannetti Iacopo 
Published: September 2023

Abstract
This paper describes the efforts, the lessons learned and the success that led, over a period of 5 years, to the development, validation and finally industrialization of high-pressure turbine vanes manufactured with additive Direct Metal Laser Melting (DMLM) technology.
The introduction of the study collects the requirements for gas turbine vanes in the range of F class and identify the material’s grade and chemical composition of the alloys. As well it is summarized the conflict among the processability and desirable mechanical properties of Nickel base alloys.
The paper explains the procedure used to simultaneously optimize the alloy and the DMLM process parameters for a Nickel based superalloy with high gamma prime content to manufacture complex geometries as high-pressure vanes in the turbine hot section. Metallurgical defects formation in additively manufacturing superalloys are strongly linked to process parameters, such as laser power, scan speed, layer thickness, scan strategy, etc. but are also directly linked to the specific geometry of the component to be processed.
Contouring parameters as downskin/upskin that have higher influence in the residual stresses of the parts and lead to a mechanical properties debit to fatigue resistance.
A “fast-work” approach was used starting with a limited validation of the components in a back-to-back comparison with the traditional technology in lab environment. Over the standard mechanical testing samples, it is introduced subsize component mechanical testing and full-scale component thermal cycle above 1’000°C.
A second step to mature the technology has been to produce and install a first set of vanes and shrouds to be tested in a real validation engine to verify resistance to the main failure modes, in particular cyclic type of damage as low cycle fatigue and crack propagation.
In the paper the final validation step is also presented. In this phase the components are installed in a production engine and monitored by periodic inspections. This allows to complete the durability assessment in real service environment.
The work is completed with an overview on the industrialization challenges of the technology. It has been provided guidelines in components design and printing strategy to mitigate macro cracks formation on high gamma prime content material, including post-print processes as EDM cut removal, thermal and surface treatments.
It is finally compared the CO2 footprint of additive technology versus investment casting, demonstrating a significative reduction in the CO2 emission in gas turbine vanes manufacturing process using additive technology.
Performance Enhancement Kit for Existing Heavy-Duty MS5001 Machines
Authors: Soman Abhimanyu , Santhana Gopalakrishnan Babu , Raghavan Srinivasan , Venna Sudha 
Published: September 2023

Abstract
A Performance Enhancement Kit is introduced to upgrade Fr5001 fleet, there by existing customers benefit from the opportunity for increased output or extended inspection intervals, improved reliability, and operability. The KIT includes advanced-technology combustion system with the new-technology turbine’s stage 1 nozzle and bucket. The components in the KIT are designed for 1) increased power output of 6% or 2) increased maintenance interval from 24 khrs to 35 khrs of mean time between maintenance. Increased power output has been achieved by increasing the firing temperature and improved maintenance has been achieved by new reduced constraint reactions using spring loaded liner and transition piece stops which reduce dynamic forces / displacements and usage of improved wear-resistant materials at sliding interfaces. As a result of improved dynamics and use of wear resistant materials, the overall reliability of the combustor is enhanced. In hot gas path component, stage 1 nozzle life has been improved by redesign of the nozzle’s cooling method and by changing the nozzle architecture, i.e., the cantilever support design of the nozzle to a simply support design. The interface components of the first stage nozzle are also redesigned to accommodate nozzle’s required design modifications. For the stage 1 bucket, the creep life has been improved to satisfy higher temperature or longer repair/replace intervals by the introduction of a high-grade nickel-based alloy, with better creep property. The above design modifications resulted in improved reliability as well as availability of the machine.
Reduced Order Models for Bladed Disks With Contact Mistuning at Blade Root Joints
Authors: Pinto Valeria , Battiato Giuseppe , Firrone Christian Maria 
Published: September 2023

Abstract
Mistuning occurring in bladed disks is a well-recognized problem in the turbomachinery industry, since it may significantly affect the dynamic behavior of the system by inducing localized amplification of the blade vibration when compared to the cyclically symmetric (tuned) configuration. Identifying the highest blade vibration amplitude requires the performance of a large number of simulations, which are usually run by introducing the mistuning in a Reduced Order Model (ROM), obtained from an initial very large Finite Element (FE) model. The traditional introduction of mistuning as blade frequency variation is being progressively replaced by methods that can correlate mis-tuning to a specific source (e.g.: geometric variations, changes in material properties, etc.). In this context, a novel reduction technique has been developed by the authors to take into account mistuning due to the contact uncertainties at the blade root joint, which can be caused by design tolerances, manufacturing processes, assembly procedures, and wear. The technique relies on the Craig-Bampton Component Mode Synthesis (CB-CMS) applied to the uncoupled blade and disk sector, which is usually included in most FE software. Afterward, the full set of master degrees of freedom is reduced using a suitable modal basis, according to the Gram-Schmidt Interface (GSI) method. The proposed reduction technique is firstly numerically validated in terms of modal parameters estimation and forced response computation. Afterward, the method is subjected to an experimental validation on a dummy bladed disk, which requires the previous estimation of the contact stiffness at the blade root-disk interface. Even if the contact stiffness parameter shows a limited influence on the system’s linear behavior, the choice of a suitable value of this parameter is deemed to become relevant when the nonlinear behavior of contact interfaces is studied through penalty contact methods. The ultimate goal of the introduced technique is to obtain a good estimation of the maximum forced response of the bladed disk with a limited computational cost and with sufficient accuracy, provided by appropriate modeling of the mistuning at the blade-disk contact interface.
sCO2 Based Pumped Heat Thermal Energy Storage Systems Valorizing Industrial Waste Heat Recovery: A Techno-Economic Analysis of the Role of High Temperature TES
Authors: Shamsi Syed Safeer Mehdi , Maccarini Simone , Trevisan Silvia , Barberis Stefano , Guedez Mata Rafael Eduardo 
Published: September 2023

Abstract
In the current renewable energy dominated power system, as power production is becoming more and more unpredictable, it would be important to act at two levels: integrating relevant power/energy capacity of energy storage and making demand more controllable. At this purpose, acting on industrial energy demand via integration of energy storage and electrification of local processes, could provide a significant contribution. At the same time, waste heat recovery (WHR) is quite a consolidated industrial practise. Nevertheless, WH valorisation is usually performed via bottoming cycles, such as steam, ORC or supercritical CO2 (sCO2) power cycles. The development of thermo-mechanical storages to be installed at industrial level, can contribute in this direction through the use of traditional technologies (rotating machinery) employed in power plants as well as in Waste-heat-to-power (WH2P) plants.
This paper presents a thermo-economic analysis of Pumped Thermal Energy Storages (PTES) for sCO2 cycles, comparing market available thermal energy storage materials for different temperature range of operation. The proposed system is purposefully designed to exploit the waste heat sources for the temperature ranges of 150–400°C, difficult to exploit for WH2P solutions and rarely addressed in literature so far. The use of sCO2 enhances the techno-economic features of these systems, the independent charging and discharging system proposed in this study can also provide a keen sense of flexibility especially for the upscaling of a PTES plant to reach an equal grid flexibility power for charging and discharging. At the same time, the valorisation of low temperature waste heat enables industries to enhance their energy efficiency, limit their operational costs and environmental impact, whilst becoming an active part in the regulation of the grid. At this purpose optimal system configurations and dispatch strategies are identified based on typical load curves of specific EU markets.
Starting from an identified reference case (a cement production plant with WH temperature to be valorized around 330°C), different PTES cycle layouts and TES technological solutions are compared on a techno-economic basis. The waste heat integration to the PTES system has been found to add satisfactory value in terms of RTE. On the other hand, it proves to be an optimal use case of waste heat valorisation than traditional waste heat to power cycles when compared in terms of exergy, capital cost and dispatchability in ever increasing RES penetration scenarios. The identification of the most optimal TES however is driven by economic factors too as presented in CAPEX and dispatchability analysis.
NASA Small Engine Components Compressor Test Facility: High Efficiency Centrifugal Compressor Vaneless Diffuser and Transition Duct Configurations
Authors: Harrison Herbert M. , McNichols Ezra O. , Blaha Matthew R. 
Published: September 2023

Abstract
The original vaned configuration of the High Efficiency Centrifugal Compressor (HECC) was developed with aggressive design targets to facilitate advancement of state-of-the-art technology in gas turbine compressors. This work documents modifications to the Small Engine Components Compressor Test Facility to support testing of the HECC vaneless diffuser and transition duct configurations, both of which are open geometries. These configurations were developed as follow-up studies to improve understanding of the differences between the predicted and actual performance of the original HECC vaned diffuser stage. Specifically, the vaneless diffuser was designed to provide the impeller with ideal exit conditions such that the impeller performance could be isolated from downstream stationary components, and the additively manufactured transition duct inlet configuration enables investigation into the effects of the inlet flow path on the stage performance. Features of note in the facility are active clearance control, bleed flow regulation, modular inlet configurations, and steady-state and fast-response instrumentation throughout the flow path. Details of the facility and instrumentation are presented as well as the baseline performance of the compressor stage. The geometry, performance, and detailed aerodynamic data have been made available to the public at https://storage.googleapis.com/hecc-data/NASA-HECC-Data-Archive.zip.