bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Evaluation of Ammonia/Hydrogen Combustion on the H Permeation and Embrittlement of Nickel-Base Superalloys
Authors: Kovaleva Marina , Dziedzic Dominik , Mashruk Syed , Evans Sam , Valera-Medina Agustin , Galindo-Nava Enrique 
Published: October 2022

Abstract
Recent studies exploring ammonia as a green hydrogen energy carrier have established its suitability for a variety of combustion technologies including gas turbines, furnaces, and internal combustion engines. Of significant interest are ammonia/hydrogen blends, which possess combustion benefits over pure ammonia, including an extended stability range and higher laminar burning velocity. Despite extensive research characterising the flame properties of these blends, very few studies explore the suitability of existing materials for the manufacture of ammonia/hydrogen combustors. The present study evaluates the impact of ammonia/hydrogen flame chemistry on the H permeation and possible loss of ductility of nickel-superalloys through exposing the samples to pure methane and ammonia/hydrogen flames at atmospheric pressure for a 5-hour period. The effect of the two flame compositions on the materials are compared through thermal desorption analysis (TDA) and room temperature tensile testing. The results showed that exposure to an ammonia/hydrogen combustion environment led to hydrogen being absorbed by the nickel superalloys but a possible variation in ductility is influenced by the combustion conditions. Furthermore, the formation of an oxide layer was shown to likely impact the hydrogen absorption rate of the materials. This work shows that ammonia/hydrogen flame chemistry on combustor materials should not be ignored and warrants further studies on material’s mechanical and environmental stability controlled by nitrogen and hydrogen species permeating at industrially relevant conditions.
Numerical Investigation on Radial Turbines Aerodynamics Aimed at the Definition of Design Rules for Industrial Applications
Authors: Lottini Fabrizio , Marconcini Michele , Arnone Andrea , Biliotti Davide , Toni Lorenzo 
Published: October 2022

Abstract
The design of turbomachines is a long iterative process, which involves several teams and disciplines. Hence, a lot of efforts are put on making it as smooth and accurate as possible. This paper introduces a procedure aimed at improving the aerodynamic design process of radial turbines for industrial applications. The procedure is based on a Baker Hughes proprietary tool for the generation of the Turbo-Expander stage geometry. An extensive CFD campaign is used both to investigate the design space of the stage and analyze the performance while varying the geometry of the rotor. Three main geometrical parameters of the wheel are identified as the ones having the biggest impact on the stage performance: the stiffness (wheel hub outlet diameter-to-outer diameter ratio), the inlet metal angle and the outlet metal angle. An automatic procedure is developed in order to generate and calculate all the different stages, with the goal to find the values for stiffness, wheel inlet and outlet metal angles which maximize the total-to-static stage efficiency in a wide range of flow coefficients. More than 700 different geometries are ultimately generated and simulated with the TRAF code, a 3D flow solver developed at the University of Florence. The results of all these simulations describe response surfaces, which not only allow to define the optimum geometry, but also to understand the influence of the main input parameters on the stage performance. Finally, the procedure was tested on a few case studies, which confirm the validity of the rules even under different conditions from the ones studied in the activity. The main outcome of the activity is the release of a tool (property of Baker Hughes) able to generate an efficient turbo-expander in a short time. Furthermore, general considerations can be outlined about the effect of the stiffness, wheel inlet and outlet metal angles on the performance of the machine.
Advanced Combustion System for High Efficiency (ACE) of the New SGT5/6- 9000HL Gas Turbine
Authors: Krebs Werner , Schulz Anatol , Witzel Benjamin , Johnson Clifford , Laster Walter , Pent Jared , Schilp Reinhard , Wasif Samer , Weaver Adam 
Published: October 2022

Abstract
Under the international climate pact (Paris Agreement), participants agreed upon a framework to reduce greenhouse gas emissions and cap the rise in global temperatures at “well below” 2°C above pre-industrial levels by 2100, with 1.5°C being the ideal scenario. To meet this goal, the development of highly efficient power plants fired with natural gas or blends of natural gas and increased share of H2 is a central cornerstone to provide controllable electrical power generation.
The new HL class addresses these needs by raising the combined cycle efficiency above 64% while offering high fuel flexibility with H2 blends up to 50% and significant turndown capability.
The new HL class is equipped with the new ACE combustion system which was developed over the last decade, and which has been successfully tested in the SGT6-9000HL at Lincoln County (North Carolina, USA). The ACE combustion system is a can annular design which is equipped with a jet stabilized main burner piloted by a central swirl burner and an axial stage which is turned on at higher loads. The paper describes the combustion technologies applied to offer stability and low emissions over a large engine operation envelope and the associated development steps. Finally, test results from rig and engine testing are presented.
Unpacking Inter-Mineral Synergies and Reactions During Dust Deposition in an Impingement Coolant Jet
Authors: Nied Eric P. , Bons Jeffrey P. , Lundgreen Ryan K. 
Published: October 2022

Abstract
This paper seeks to unpack the synergies that exist between minerals during deposition of the heterogeneous AFRL02 mixture in gas turbine engines and demonstrate that the contributions of each mineral cannot be considered independently of others. In each experiment, one gram of a mineral dust (0–10μm particle diameter distribution) was injected into an 894K, 57m/s coolant flow impinging normally on a Hastelloy X plate with a surface temperature of 1033K, 1144K, or 1255K. Capture efficiency measurements, deposit morphology analyses, and X-ray diffraction results are reported. Besides AFRL02, single mineral dusts, dual mineral dusts, and AFRL02-like dust blends lacking in one mineral were tested. The results of the experiments elucidate that the deposition behavior of single minerals indeed cannot explain the composite deposition of heterogeneous mixtures of minerals. For example, gypsum had the highest capture efficiency of any single mineral in ARFL02, and yet removing gypsum from AFRL02 counterintuitively raised the capture efficiency of that blend when compared to AFRL02. Quartz was found to erode albite deposits but stick to and build upon dolomite and halite deposits, even though quartz did not deposit significantly as a single mineral. Quartz also chemically reacted with gypsum and dolomite to form wollastonite and diopside, respectively. Finally, we found that the capture efficiency of each blend increased with plate temperature, but not according to the same trend. Results are interpreted through the lens of CaO-MgO-Al2O3-SiO2 eutectic chemistry, but the chemical pathways by which these eutectics come into existence is found to be of equal importance.
A Methodology for a Coupled Structural - CFD Analysis of Compressor Rotor Blades Subjected to Ice Impact With Uncertain Impactor Parameters
Authors: Böhm Holger , Hornig Andreas , Gude Maik , Högner Lars , Meyer Marcus 
Published: October 2022

Abstract
A method for a coupled structural – Computational Fluid Dynamics (CFD) analysis of a compressor rotor blade subjected to an ice impact scenario is investigated to assess the impact related blade deformations from a structural and fluid-dynamics perspective. On the basis of a probabilistic approach, in total 50 impact scenarios are derived for this study. In a first step the numerical structural model based on Finite Elements (FE) is discussed, including several parameter variations like impact location, ice diameter, ice density and rotor speed. Different analysis steps are subsequently carried out using LS-DYNA implicit / explicit on a high performance computing (HPC) cluster. Resulting blade deformations are evaluated in terms of local plastic deformation, cup size and modal parameters in comparison to the undamaged reference structure. The resultant post-impact blade geometry is extracted from the result data and passed to the CFD simulation setup in a fully automated manner. Based on this deformed structural mesh data, the fluid mesh is morphed via a radial basis function (RBF) approach and analysed with CFD. Finally, an uncertainty quantification study is performed to assess the variability of results with regard to the definition of the ice impactor.
Calibration of a CFD Methodology for the Simulation of Additively Manufactured Components Accounting for the Effects of Diameter and Printing Direction on Friction and Heat Transfer
Authors: Mazzei Lorenzo , Da Soghe Riccardo , Bianchini Cosimo 
Published: October 2022

Abstract
Additive manufacturing (AM) enables designs that are not manufacturable with conventional techniques and that offer reduced weight and better thermal performance. This is of particular relevance for gas turbine cooling as well, as proved by the first applications of combustors and turbine blades made entirely by AM.
Despite that, the effects of the increased surface roughness on friction and heat transfer are not fully understood yet and this hinders the design process demanding further characterization by means of experimental tests. Also the exploitation of CFD simulations is complicated by the current modelling approaches, still based on the equivalent sand-grain roughness (ks) that results in a velocity shift in the boundary layer. The estimation of such parameter is not straightforward and the approach leads to an unphysical overestimation of the heat transfer even using ks values calibrated with experiments.
This work represents the continuation of the benchmarking and calibration of a CFD methodology based on friction and thermal corrections proposed by Aupoix from ONERA. The results presented in the previous two papers focused on three literature test cases representative of straight and wavy additively-manufactured minichannels with circular and rectangular cross-section. In this paper a new dataset published by Penn State University is considered, investigating the effect of diameter and printing direction on the fluid-dynamical performance of circular straight minichannels. This work confirms the validity as a first approximation of a linear relation between ks/Dh and the relative arithmetic roughness Ra/D, provided that the build orientation is sufficient to avoid excessive channel deformation (i.e. greater or equal to 45°). On the contrary, a similar calibration for the heat transfer was unsatisfactory, suggesting a role of channel shape or other parameters not understood at the moment.
The Role of Endwall Shape Optimization in the Design of Supersonic Turbines for Rotating Detonation Engines
Authors: Mushtaq Noraiz , Persico Giacomo , Gaetani Paolo 
Published: October 2022

Abstract
Rotating detonation engines (RDE) are characterized by a thermodynamic cycle with an efficiency gain up to 15% at medium pressure ratios with respect to systems based on the conventional Joule-Bryton cycle. Multiple turbine designs can be considered and this paper deals with the supersonic inlet configuration. After having reviewed the main design steps of an exemplary RDE supersonic turbine, the paper focuses on the considerable effects that endwall losses have on the performance of supersonic-inlet turbines and on the reasons why endwall contouring is strongly recommended for an efficient design. Parametric analyses, carried out by a novel in-house mean-line code validated against CFD, reveal that endwall friction losses contribute significantly to the overall stage loss. Endwall boundary layers also reduce the effective area, which can be critical for the self-starting capability of the supersonic channel. Therefore, a variable blade height geometry is necessary to extend the design space and guarantee a higher efficiency with respect to a constant-span configuration. The in-house CFD-based evolutionary shape optimization code was adapted to search for the optimal endwall shape for these unconventional machines. The optimal shape reduces shock losses and deviation angles and provides a significant gain in efficiency and work extraction. Finally, a novel technique is proposed to design the three-dimensional shape of the rotor based on the method of characteristics and tailored on the flow delivered by the stator.
A New Interpretation of Hot Gas Ingress Through Turbine Rim Seals Influenced by Mainstream Annulus Swirl
Authors: Graikos Dimitrios , Tang Hui , Sangan Carl M. , Lock Gary D. , Scobie James A. 
Published: October 2022

Abstract
Rim seals are fitted at the periphery of the stator and rotor discs to reduce the adverse effects of hot gas ingress on highly stressed turbine components limited by temperature. Ingress is induced by rotational effects such as disc pumping, as well as by asymmetric pressure-driven unsteady phenomena. These influences superpose to form a complex flow-physics problem that is a challenge for computational fluid dynamics. Engine designers typically use practical low-order models that require empirical validation and correlating parameters. This paper identifies the swirl ratio in the mainstream annulus as a dominant characterising parameter to predict ingress. This is a new interpretation that is supported by extending a low-order model based on turbulent transport using an effective eddy mixing length based on the difference in swirl between the annulus and seal clearance.
Experimental measurements were made using a 1.5-stage turbine rig at low Reynolds number. The influence of annulus swirl ratio was investigated over a range of flow conditions and two rim-seal geometries, with the ingress quantified using CO2 tracer concentration in the sealing flow. The concentration data were complemented by measurements in the annulus using a five-hole aerodynamic probe.
Highly Resolved Large-Eddy Simulations of a Transonic Compressor Stage Midspan Section - Part II: Effect of Rotor-Stator Gap
Authors: Przytarski Pawel J. , Leggett John , Sandberg Richard , Bode Christoph 
Published: October 2022

Abstract
The need for increased power density and reduced weight in modern gas turbines often leads to shorter inter-row distances. This translates into stronger blade-to-blade and row-to-row interactions. These interactions are particularly difficult to predict for low-order methods such as URANS due to the overlap between deterministic unsteadiness frequencies and stochastic unsteadiness frequencies. This lack of a spectral gap results in complex broadband energy spectra that necessitate the use of high-fidelity scale resolving simulations to predict such flows and understand how they affect the flow behavior of subsequent bladerows. In this study, wall-resolved large eddy simulations have been conducted of a transonic compressor stage at a realistic rotor Reynolds number of 1 × 106, varying the axial gap between rotor and stator. The analysis of the data focuses on the impact of the rotor-stator gap on the downstream stator boundary layer behavior and employs phase averaging to describe the flow in a detailed manner. We then report on how the rotor-stator gap affects loss generation and loss mechanisms. Overall, a 2.5% overall stage loss decrease was found when the gap size was reduced by 25%. This reduction nearly entirely stems from the stator bladerow, despite the stator contributing only 15% to the total stage loss. The high-fidelity simulations are complemented by unsteady RANS calculations of the same configuration, to assess how accurately current design tools capture the complex row-to-row interactions. Although the overall loss magnitudes were captured reasonably well, no significant variation with gap size were found with URANS.
Low Cycle Fatigue Characterization of Additive Manufactured Specimen With as Printed Surface Roughness Made From Multiple Nickel Based Super Alloys
Authors: Torkaman Alex , Keshava Bhattu Ramesh 
Published: October 2022

Abstract
Additive manufacturing is a transformative technology that can enable advanced designs for gas turbines that are not otherwise possible. While the expansion of design envelope can greatly contribute to improvement in efficiency and fuel flexibility of gas turbines, limitations in material properties can adversely affect durability of additively manufactured components if not properly characterized and accounted for in the design phase. An important consideration for durability of turbine components is the LCF (Low Cycle Fatigue) life, and it is influenced by the surface effects that are characteristic of the layer by layer build process of additive manufacturing. The influence of as printed surface texture on LCF properties of multiple additive manufactured alloys is evaluated in this work as part of a broader incorporation of additive alloys in gas turbines. Hastelloy-X is a commonly produced alloy that is utilized in combustion components, enabling state of the art fuel flexibility and hydrogen combustion. An Inconel-939 derivative alloy has been recently utilized in static turbine components due to its high temperature creep capability and oxidation resistance, resulting in improved cooling efficiency and increased turbine performance. In this paper, specimens with as printed and machined gauge (machined from additive manufactured bars) are produced with both Hastelloy-X and IN939 derivative alloys. Specimens are tested for LCF at multiple temperature and strain range conditions and comparisons between as printed (or rough gauge) versus machined gauge specimen are made to determine influence of as printed surface conditions. Results of the experiments for both alloys are presented in normalized form to evaluate performance of as printed versus machined surfaces at various test conditions. Fractographic analysis is conducted on IN939 derivative failed specimens and the influence of surface roughness on crack initiation at the microstructural level is discussed.
The Influence of Boundary Layer State and Trailing Edge Wedge Angle on the Aerodynamic Performance of Transonic Turbine Blades
Authors: Rossiter A. D. , Pullan G. , Melzer A. P. 
Published: October 2022

Abstract
Trailing edge loss typically accounts for a third of the profile loss of a transonic turbine blade. In this paper, two dominant influencing factors — boundary layer state and trailing edge wedge angle — are quantified using a combined experimental (single airfoil transonic tests) and computational (wall resolved LES) approach. Three key findings are reported. First, the switch between two flow regimes — detached vortex shedding and transonic vortex shedding — as the Reynolds number is increased, is identified and explained. It is shown that the transition of the pressure surface boundary layer drives the switch from the former to the latter; this change is associated with a jump in loss of close to 100%. The switch is also shown to affect the base pressure distribution around the trailing edge, changing it from uniform, with an isobaric dead-air region, to non-uniform. Second, the influence of the trailing edge wedge angle is explored. It is found that higher wedge angles can offer performance benefits in both loss and base pressure — with a change from an 8° to 14° geometry providing up to a 29% reduction in overall loss for the geometry tested. Finally, as these findings are the result of changes to the unsteady flow phenomena around the trailing edge, they would not be picked up by current low-fidelity, steady design tools. A method is proposed to use data, such as that presented in this paper, to improve low fidelity modelling.
Computational Modeling of the Effects of Rain on Wind Turbine Performance
Authors: Gahlot Aishwerya , Sankar Lakshmi , Pichitkul Auraluck 
Published: October 2022

Abstract
Wind turbines often operate under misty or rainy conditions. There is a considerable body of experimental evidence on the adverse effects of rain on wind turbine power production. Physical understanding of these effects, guided by quantitative modeling, is necessary to fully understand the effects of rain power production. This work presents an application of a two-way coupled computational fluid dynamics approach to the modeling of the effects of rain on airfoil and rotor performance. The aerodynamics is modeled by solving the Reynolds averaged Navier-Stokes equations with a suitable turbulence model. The droplet transport is modeled using an Eulerian approach that allows droplets of different diameters to be treated as individual/independent species, although all the studies presented here were for specified droplet sizes. The external flow exerts a drag force on the water droplets, and a reaction force is exerted by the droplets on the airflow.
2-D viscous flow simulations are presented for a representative wind turbine airfoil for several angles of attack under wet and dry conditions. Regression fits of these drag polars have been used in a combined blade element-momentum analysis for the NREL Phase VI rotor. The calculations indicate a loss of 30% to 40% in power production, attributable to rain, over a range of wind speeds.
Accurate Prediction of Confined Turbulent Boundary Layer Flashback Through a Critically Strained Flame Model
Authors: Novoselov Alex G. , Ebi Dominik , Noiray Nicolas 
Published: October 2022

Abstract
A promising path forward for power converting gas turbines that must produce low-to-no carbon emissions is the transition from burning pure natural gas to a mixture that includes cleanly produced hydrogen. However, such a transition also modifies the flame dynamics within the burner and so must therefore be studied. One important change that occurs with increased hydrogen content is the heightened propensity of boundary layer flashback, wherein the flame propagates upstream through the low velocity region near the wall. Propagation of the flame into the poorly shielded mixing section can have disastrous results, and therefore must be avoided. In this work, a newly developed model to predict the boundary layer flashback limits based on a balance between the extinction limit flame speed and the near-wall velocity is presented. The model is capable of accurately predicting flashback limits in non-swirling burners and can be extended to swirling burners using information about a single flashback event. In addition, inclusion of a mean non-reacting velocity field computed via Large Eddy Simulation allows for a significant increase in the accuracy of the model when applied to swirling flows. Ultimately, this model provides a new pathway for the design of flashback resistant gas turbines, even with the addition of new fuels like hydrogen.