bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scaling of Lean Aeronautical Gas Turbine Combustors
Authors: Gövert Simon , Gruhlke Pascal , Behrendt Thomas , Janus Bertram 
Published: September 2023

Abstract
A numerical procedure is presented for the scaling of lean aeronautical gas turbine combustors to different thrust classes. The procedure considers multiple operating points and aims for a self-similar flow field with respect to a reference configuration. The developed scaling approach relies on an optimization-based workflow which involves automated geometry and numerical grid generation, unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and post-processing of the reacting flow field. Kriging is applied as a meta model to identify new sets of parameters for combustor geometry generation. A generic lean-burn high pressure aeronautical combustor has been designed to serve as a first verification test case with reactive flow characteristics comparable to real combustion chambers. The burner geometry is parameterized by 23 free parameters which are altered within the scaling process. The definition of a suitable scaling function is essential for the success of the scaling approach. A scaling function based on pressure loss, axial location of heat release, pilot air split and the temperature profile at the combustor exit is proposed. The developed procedure is tested and applied for the scaling of an internally-staged lean combustor to a lower thrust class considering multiple operating points simultaneously. In total, 65 different combustor variants have been evaluated by the scaling procedure. Simulations were performed for each of these configurations at take-off, approach and idle operating conditions. The final combustor configuration, scaled to a lower thrust class, shows good agreement to the reference configuration in terms of the scaling targets and reasonably resembles the emission indices. Integrating the scaling procedure into the design process of future combustion systems could reduce the required design iterations and thereby contribute to significantly reduced development times and costs.
Numerical Modelling of Swirl Stabilised Lean-Premixed H2-CH4 Flames With the Artificially Thickened Flame Model
Authors: Castellani Simone , Nassini Pier Carlo , Andreini Antonio , Meloni Roberto , Pucci Egidio , Valera-Medina Agustin , Morris Steven , Goktepe Burak , Mashruk Syed 
Published: September 2023

Abstract
The lean premixed technology is a very convenient combustion strategy to progressively move from natural gas to high hydrogen content fuels in gas turbines limiting the pollutants emissions at the same time. The enabling process that will allow the combustor to manage a full H2 operation requires relevant design modifications, and in this framework, the numerical modelling will be a pivotal tool that will support this transition. In this work, high-fidelity simulations of perfectly premixed swirl stabilized flames have been performed varying the H2 content in the fuel from 0 to 100% to investigate the effect of the hydrogen addition on the methane flame. The artificially thickened flame model (ATFM) has been used to treat the turbulent chemistry interaction. The numerical results have been compared with the detailed experimental data performed at Cardiff University’s Gas Turbine Research Centre. After the numerical model validation against experimental OH* chemiluminescence maps has been presented, a deep numerical investigation of the effect of the H2 addition on the flame has been performed. In this way, the work aims to highlight the good prediction capability of the ATFM, and, at the same time, highlight the change in the different contributions that govern the flame reactivity moving from 100% CH4 to 100% H2 in very lean conditions.
Multidisciplinary Optimization of a High-Speed Low Pressure Turbine Rotor Using 3D Inverse Design Method
Authors: Zhang Luying , Zangeneh Mehrdad 
Published: September 2023

Abstract
The design of high-speed low-pressure turbine (LPT) is challenging due to the mechanical constraints and the increased Mach number. A tradeoff has to be made between the aerodynamic performance and structural integrity. This was previously done through iterations with computational fluid dynamics (CFD) simulations and Finite Element Analysis (FEA). In this paper, a fast automated optimization workflow using a 3D inverse design method coupled with a multi-objective genetic algorithm is presented. The inverse design method generates the blade geometry for a given specification of blade loading parameters and spanwise work distribution. It can explore a large design space with fewer design parameters compared to direct design methods where the blade geometries are parameterized by geometrical variables. The maximum thickness and stacking can also be varied during the optimization. Both the blade geometry and the 3D inviscid flow field are provided by the inverse design solver. The aerodynamic performance can be related to the loss factors (such as profile loss, leakage loss and endwall loss) calculated from the blade surface velocities. The centrifugal and bending stresses are related to the blade geometry features. These can be optimized in the automated workflow without running time consuming CFD and FEA. This fast design optimization process is applied to a high-speed LP turbine for aeroengine applications. CFD and FEA are only used to validate the output from the fast optimization process and the results show improvement in efficiency without any increase in stresses.
Temperature Effect on Solid Deposit Formation in Turbine Lubricants
Authors: Juárez Raquel , Gutierrez Noble , Petersen Eric L. 
Published: September 2023

Abstract
When exposed to extremely high temperatures, oils in turbomachinery applications can degrade until they form solid, carbonaceous coke deposits that can cause serious operational issues. Three of the main factors that affect the coke formation process are temperature, residence time, and oil composition (basestock and additives). This study explored the effect of surface temperature on the coking induction time of four turbine oils. The induction time is defined as the amount of time required for deposits to start forming and accumulating under specific test conditions. Experiments were conducted at maximum measured surface temperatures that ranged between approximately 430°C to 540°C. It was confirmed that increasing the surface temperature results in an exponential increase of the oil degradation rate (or an exponential decrease in induction time). Using the Arrhenius relation, the ratio of apparent activation energy to ideal gas constant, Ea/Ru, was calculated for two different definitions of test temperature. These activation energies ranged from 12,900 to 46,800 K. These values, which are related to the oils’ resistance to thermal breakdown, may be used to predict how an oil will perform under specific operating conditions. It was found that three of the four oils performed similarly, while the remaining one had an inferior performance. Future studies should explore the effect of more factors, such as residence time, exposure to oxygen, and heated-surface geometry, on the induction time.
On the Influence of Bearing Modeling Details on the Dynamical System Effects of a Mid-Size Turbocharger Rotor
Authors: Zobel Arthur , Fuhrer Christopher , Vogt Damian M. , Nakos Alex , Beirow Bernd , Blessing Alexander , Zippack Carolin 
Published: September 2023

Abstract
The investigation of the excitation of turbocharger rotors to quantify the High-Cycle-Fatigue (HCF) risk is still a demanding task nowadays. The common way to investigate such phenomena is to look either at the turbine or the compressor rotor in an isolated manner. This approach gives mostly reliable results, if the investigated excitation pattern is stemming from the up- or downstream parts in the machine. However, there is a lack of studies on the existence of responses, which may exist due to the coupling between compressor and turbine. With the increase of computational capabilities and the improvement of FE tools, it is possible to create a full rotor model featuring the compressor and the turbine wheel as well as the bearings to investigate the dynamical behavior of the full rotor at different resonances.
To carry out such an investigation, both wheels and the shaft are modeled. The axial, as well as the radial bearings, are modelled realistically by suitable elements and values. Due to the asymmetry of damping and stiffness properties, the resulting system matrices are asymmetrical as well. The eigenfrequencies and mode shapes of such a system can be obtained in a reasonable time by carrying out a modal analysis using the QR damp eigensolver in Ansys APDL.
The present paper will show the differences in dynamical system effects of a mid-size turbocharger with different shaft support conditions. For this purpose, the FE simulation with the full rotor and fixed support at the radial bearing position, which is comparable to the isolated rotor consideration, will be compared to the model featuring the detailed bearing modeling with stiffness and damping values originating from the OEM. Besides the detailed process of modeling the bearings, the mutual influence of both rotor wheels at certain eigenfrequencies is analyzed. This allows to conclude on the level of detailing needed to ensure that dynamical system effects are properly accounted.
Pressure Actuated Leaf Seal Design and Test for sCO2 Applications
Authors: Grondahl Clayton , Armstrong Rich 
Published: September 2023

Abstract
Interstage shaft leakage in sCO2 turbomachinery is challenged by high differential pressure, high speed and relatively small shaft diameters where secondary seal leakage flow of conventional seals can adversely impact performance. With several programs now focused on sCO2 power conversion cycles, sealing solutions need to be advanced in their TRL to facilitate commercial applications. To this end, Sandia National Laboratories is working with industry partners to identify and test solutions. Pressure actuated leaf seals is one of the technologies identified with significant application potential. They are well suited to meet these challenges with designs capable of high differential pressure, high speed and favorable rotor dynamics owing to their short axial length without cross-coupled stiffness hazard. Thin sheet metal seal leaves passively close with system differential pressure after transition through shaft modes that can damage fixed seals. These seals have been applied in one sCO2 development application to date. To evaluate their use in sCO2 power conversion cycles with advanced nuclear reactors now under development two seal configurations were designed and fabricated for test in the Sandia Brayton Energy Laboratory at differential pressure of up to 3,000 psid (207bar) and maximum shaft speed of 40,000 RPM. Features of both configurations are discussed. Prior to dynamic testing at Sandia National Laboratories, a static test of each seal configuration was conducted at CMG Tech using high pressure water to confirm pressure actuated seal closure and assess interleaf seal leakage. Test results of measured seal leakage is discussed. Successful demonstration of pressure actuated leaf seal function and low leakage flow in static testing provides a confident starting point for dynamic testing in the Sandia sCO2 test facility. Demonstration of Pressure Actuated Leaf Seals technology readiness for extreme sCO2 conditions advances their consideration for use in a broad range of turbomachinery including gas and steam turbine shaft sealing, compressor interstage sealing, and pump wear rings.
The Effect of Trailing Edge Grid Resolution in Large-Eddy Simulations
Authors: Miki Kenji , Ameri Ali 
Published: September 2023

Abstract
Ceramic Matrix Composite (CMC) with environmental barrier coating can tolerate significantly higher temperatures compared with the conventional metal alloy blades and thus can help achieve higher thermal efficiency in gas turbine engines. Due to the complex fabrication process of CMC blades, larger blade trailing edge thicknesses and larger leading-edge radii of curvature are expected. These features significantly alter aerodynamic performance especially near the trailing edge and thus the loss profile. In previous studies, the authors used large eddy simulation (LES) as well as the Reynolds Averaged Navier-Stokes (RANS) coupled with an intermittency function-based transition model to simulate aerodynamic performance of three different CMC blades and compared the predictions against the data acquired at NASA Glenn Transonic Turbine Blade Cascade Rig. Although these were able to successfully predict different characteristics of aerodynamic performance among three different blades (e.g., pressure loading and integrated losses), LES consistently predicted a small recirculation bubble at the end of the suction side. This was not inconsistent with the physics of the flow, but the pressure loading, locally, near the trailing edge, and as a result, the measured wake profiles did not match the experimental data. To delve further into these issues, a new LES grid with a much finer mesh near the trailing edge was generated. The spanwise extent of the grid was increased by 50% at the same time to accommodate large vortices which might not have been captured by the original domain due to size limitations. An LES simulation for the CMC blade with the largest trailing edge thicknesses at the high-freestream turbulence (Tu = 13%) condition showed that using such a mesh is necessary for LES to accurately capture the transition phenomena on the suction side. The resulting total pressure coefficient profile and the shift of the wake profile were greatly improved. The increase in the span was found to be inconsequential.
Techno-Economic Analysis of a Physisorption-Based Hydrogen Storage System
Authors: Schueler Yannik , Otto Marcel , Kapat Jayanta , Schmitt Joshua 
Published: September 2023

Abstract
Alternative long-term storage of energy is becoming increasingly important due to climate change. Hydrogen-based storage technologies have long been considered promising alternatives to batteries. However, the different forms of hydrogen storage have various disadvantages and are still comparatively expensive. As an alternative, this paper deals with a new concept for hydrogen storage, the Cryogenic Flux Capacitor (CFC). It is intended as an intermediate between high-pressure and liquid storage to exploit the advantages and reduce the disadvantages. This paper ranks the CFC technology against the others. For this purpose, it investigates the economic viability and the specific application as a grid-connected system. A complete system from hydrogen production and storage to conversion into electrical energy is considered. In detail, the costs for storage and storage time are compared, and the size scaling of a CFC-based system as a grid-connected system is examined. The Levelized Costs of Energy (LCOE) is calculated and compared as a benchmark. It turns out that a CFC-based storage system also requires a tremendous amount of energy in the form of liquid nitrogen and the associated operational costs for cooling down the hydrogen. Nevertheless, the overall operating costs are between high-pressure and liquid hydrogen storage. Most surprising is the LCOE, which at 0.192 $/kWh-0.234 $/kWh, is well within the range of the other storage technologies. As a grid-connected storage system, CFC technology can be used as a small to a medium-scale energy storage system, e.g., to serve smaller neighborhoods.
Numerical and Experimental Evaluation of Noise and Performance in UAV Propellers
Authors: Serrano José R. , García-Tíscar Jorge , Quintero Pedro , Ramírez Federico N. 
Published: September 2023

Abstract
Due to the increasing use of unmanned air vehicles (UAVs) for civil and military purposes, accurate evaluation of this kind of aircraft is becoming a fundamental aim during their development. Particularly, propellers are often the most critical elements influencing a UAV’s performance and noise emission. Therefore, selecting the appropriate tools for modeling the behavior of this element becomes crucial, especially at the design stages, evaluating both their accuracy and cost. In this paper, we will test the suitability of different tools for numerical modeling and perform an experimental campaign to validate the numerical results.
Particularly, from the computational point of view, the performance of a typical propeller will be evaluated for various values of the advance ratio and various rotational speeds at hover, paying special attention to the thrust and thrust coefficient. Various modeling approaches will be analyzed in this sense, including low-order Blade Element Momentum Theory (BEMT) evaluation, Reynolds Averaged Navier-Stokes (RANS) methodologies (both stationary using a moving reference frame and transient), and transient Detached Eddy Simulations (DES), to analyze the turbulent structures arising in these devices. Noise emission will be evaluated at the most significant working conditions by applying a Ffowcs-William & Hawkings approach to the computed unsteady results and a simplified Farassat formulation to the BEMT results. These numerical calculations will be carried out using open-source software such as OpenFOAM and libAcoustics in the case of CFD modeling or in-house codes for low-order models.
Regarding experimental validation measurements, the hovering propeller’s thrust and far-field acoustic measurements will be performed in an anechoic chamber. The experimental setup will also be mounted in a wind tunnel for forward flight tests and to validate the performance results at different advance ratios. Furthermore, rapid prototyping is a necessary part of the development process for small propellers; thanks to progress in additive manufacturing (AM), this could even become the preferred way to manufacture in-house spares. In this paper, we will also assess the suitability of Fused Deposition Modeling — one of the most popular AM techniques — for manufacturing research propeller prototypes by comparing the propulsive and acoustic performance of a commercial propeller against its 3D-printed version.
Numerical Investigations of Transitional SBLI on a Highly Loaded Transonic Compressor Passage
Authors: Kahraman Selin , Bourgeois Jason A. , Janke Christian , Swoboda Marius 
Published: September 2023

Abstract
The present paper focuses on the adverse effects caused by transitional shock wave boundary layer interaction (SBLI) on a highly loaded variable stator vane (VSV) at altitude. The VSV section under investigation is representative of business jet applications. A new design solution is proposed, which mitigates the limiting effects of transonic speeds. An optimization study has been carried out at multiple mission points. Reynolds numbers (Re) of 750k and 200k (respectively sea-level and altitude conditions) have been investigated numerically at multiple operating speeds. At higher Mach numbers, due to strong transitional SBLI effects, the vane passage is choked by the shock wave moving rearward at Re 200k. This phenomenon, which is only observed at altitude conditions, results in significantly increased losses and a reduced working range. The new section design alleviates these detrimental effects by decreasing the acceleration in the front portion of the suction surface, controlling the shock location. The losses are significantly reduced, and the choking limit is increased to M = 0.903 at over-speed. In this condition, amultiple-shock structure is introduced with high loading observed in the passage. This shock structure may strengthen oscillations and instability, which will be investigated via high fidelity methods in the future.
Impact of Liquid Properties on Flame Behavior for Sustainable Aviation Fuels in Gas Turbine Combustors
Authors: Dasgupta Debolina , Bhattacharya Chandrachur , Som Sibendu 
Published: September 2023

Abstract
Sustainable Aviation Fuels provide a means for decarbonization of the aviation sector. The properties of these fuels can be different from that of conventional jet fuels. To assess the impact of changes in fuel properties on the flame behavior, Large-Eddy Simulations of the Referee Rig are performed for a stable condition. The average jet fuel, A-2 is used as the reference fuel and density, viscosity and heat of combustion are perturbed to understand their individual impact on the flame behavior. Additionally, combined changes of two and all three properties are also assessed. Individual changes in density and viscosity have limited changes to the flame shape and flame stabilization. A decrease in viscosity leads to a more symmetric flame. Additionally, less larger droplets are seen due to increased secondary break-up. Heat of combustion shows a more pronounced impact with larger regions of higher temperature observed for a higher heat of combustion. A combined decrease of density and viscosity is shown to lead to a more symmetric flame with a more uniform distribution of higher temperature and OH regions. A combined decrease of these two quantities with a higher heat of combustion is shown to increase the local temperatures within the flame. These impacts on the flame shape are expected to have consequential changes to the off-stable performance of these fuels such as lean blow out.
Impacts of Superalloys on the Surface Quality of Additively Manufactured Channels
Authors: Corbett Thomas M. , Thole Karen A. , Ryan Daniel , Bollapragada Sudhakar , Kirka Michael , Ledford Christopher 
Published: September 2023

Abstract
Gas turbines feature many components that require superalloys capable of handling extreme thermal environments. Increasing the selection of materials available for these components is important to their use in these extremely high temperature environments. This study investigated two recently developed materials intended to be used for additive manufacturing (AM) with one superalloy based on Cobalt and the other on Nickel. Sets of four test coupons were built using the materials, in addition to the commonly used Inconel-718, on multiple laser powder bed fusion (L-PBF) machines. Several build conditions were varied between coupon sets including coupon orientation, contour settings, and upskin and downskin treatment. Each set of test coupons featured four unique cooling designs to explore how different cooling technologies would be impacted by the variations in build conditions. After being built, coupons were CT scanned to determine accuracy to design intent and quantify the surface roughness. The CT scans indicated that horizontally built test coupons had significantly higher deviation from design intent and higher surface roughness than those built vertically. Results also indicated that the Cobalt-based alloy consistently had a smoother surface quality with lower surface roughness compared to the nickel-based alloy. After geometric characterization, the cooling performance of the test coupons was measured experimentally. Pressure losses were found to correlate with increases in surface roughness; however, in some cases the convective heat transfer did not increase proportionally to the pressure loss as a result of surface features significantly blocking the flow without proportionally increasing convective heat transfer.