bluuebunny/crossref_metadata_2025_split huggingface dataset:
Economic Evaluation of Ceramic End Milling Tools for Rough Milling of Blisks Made of Inconel 718
Authors: Zimmermann Richard , Fricke Kilian , Ganser Philipp , Bergs Thomas 
Published: September 2023

Abstract
High-pressure compressor stages in modern aero-engines are commonly designed in the integral blisk (“blade-integrated disk”) configuration, due to their advantages regarding weight, blade density and freedom in airfoil design over conventional blade-disk assemblies. These components consist of thin-walled airfoils with high-aspect ratios, which result in a large weight percentage of the workpiece to be removed before achieving the final part. Because of their complex shape and tight dimensional tolerances, most of the machining is done by the conventional cutting technologies turning and milling. Thereby, first near-net-shape blanks are turned and then the blades are milled with end milling tools. As operating temperatures in the compressor section are rising to reach higher engine efficiencies, blisk components are increasingly made of heat-resistant superalloys (HRSA) such as Inconel 718. Machining processes for these components made of difficult-to-cut nickel-based alloys exhibit low productivity and high tool wear, which can be attributed to the conventionally used cemented carbide tooling. Innovative ceramic cutting materials such as SiAlON can be produced in the form of end milling tools and offer the potential to increase the productivity in the time-consuming roughing operation significantly. Due to the high hardness at elevated temperatures, the cutting velocity vc can be increased by a factor of 20 when using ceramic end milling tools compared to conventional strategies with cemented carbide. However, these innovative cutting tools are rarely applied in series production, which may be due to their high costs compared to cemented carbide tools. This study, therefore, aims at evaluating the economic potential of SiAlON end milling tools for roughing operations of blisk components made of Inconel 718. To reach this goal, a blisk milling process was designed and executed with both tool configurations, tool wear and machining times of all operations were measured and tool life as well as machine costs are evaluated.
Cooling and Sealing Design of Instrumentation Ferule for Annular Combustors
Authors: Rajesh Mavuri , Stefano Gori , Arun Ampi K 
Published: September 2023

Abstract
The Annular combustion system usually has an instrumentation system like flame detectors, spark plugs, and pulsation probes in the primary zone to investigate flame stability, ignition, and measuring the acoustic pulsations. The primary zone experiences the highest temperatures and sealing & cooling of an instrumentation system is critical to get timely combustion performance data. The location, and sizing of the instrumentation ferule that encompasses the instrumentation system are to be properly evaluated such that to avoid hot combustion gas injection in the ferule. The objective of the paper is to document the cooling and sealing requirements around the instrumentation ferule such that real-time data acquisition is maintained, and the structural integrity in terms of LCF/Creep life is the main design driver. System of flow, thermal, and structural is carried out to investigate unsteady flow recirculation/local peak temperatures to properly size the required cooling flow. The sealing flow injected around the ferule should be aligned with the core combustion flow to minimize the pressure drop. The first part of the paper presents the baseline configuration experiences the high static temperatures downstream of ferule system, then the thermal analysis process map is used to investigate different cooling schemes and impact on metal temperature reduction due to the conduction effect. The structural integrity of ferule system is also analyzed to verify the design requirements for various designs. To validate the numerical process, two potential configurations (Lifted ferule and Flat ferule) have been tested at high pressures and high temperatures keeping instrumentation around the ferule system. The numerical model is further tuned by implementing the film effectiveness and validated with test results. The flat and lifted ferule numerical results are quite aligned with the experimental data at most of the locations, however flat ferule shows a better cooling effect compared to the lifted system. Also, the paper presents the temperature spread on the ferule system from the experimental test data and presented it for all three configurations. The results indicate that the temperature spread is around 0 to 8% for the baseline and flat ferule cases, where the spread is high for the lifted ferule case. Due to limitation with current thermal process map inability to capture circumferential variation, only the test results (temperature spread) are presented.
Characteristic Secondary Flow Behavior in Ultra-Highly Loaded Turbine Cascade Under Transonic Condition
Authors: Tsujita Hoshio , Kaneko Masanao 
Published: September 2023

Abstract
A gas turbine is increasingly required to be enhanced in quick start capability as well as in aerodynamic performance to support variable energy output from renewable sources such as solar and wind powers. On the other hand, the diameter of core engine of a turbofan engine is demanded to be decreased for the improvement of propulsive efficiency by the increase of bypass ratio. Moreover, for the farther enhancement of the specific work output of micro gas turbines by the increase of the turbine inlet temperature, the application of a thick turbine blade will be required for the installation of any internal and external air-cooling system. These various requirements would be responded by an increase of blade loading of axial turbines.
In this study, the 3D computations were performed for the flows in an ultra-highly loaded linear turbine cascade (UHLTC) with the blade turning angle of 160 degrees under transonic condition with the assumption of steady compressible flow. The focus was on the characteristic secondary flow behavior and the associated loss generation. In the computations, the isentropic exit Mach number was varied in the range from 0.6 to 1.3 to examine the effects of the variation of shock wave formation on the secondary flow structure. The computed results for UHLTC were also examined by comparing with those observed in a typical transonic turbine cascade to highlight the characteristic secondary flow behavior caused by the increase of blade loading.
Prediction of the Influence of the Inlet End-Wall Boundary Layer on the Secondary Flow of a Low Pressure Turbine Airfoil Using RANS and Large-Eddy Simulations
Authors: Gisbert Fernando , Cadrecha David , Apoita Patxi 
Published: September 2023

Abstract
This paper analyses the effect of the inlet end-wall boundary layer on the secondary flow of a low pressure turbine airfoil cascade at Reynolds number 2 × 105 using RANS and implicit Large-Eddy Simulations. The results are compared against experimental data obtained at two low speed linear cascade facilities, one located at the Whittle Laboratory of the University of Cambridge and the other at the Polytechnic University of Madrid. The RANS turbulence model is the k-ω-γ-Reθt and no turbulence model has been used in the LES. An unstructured mesh of hexahedra and prisms is used, with high order elements used in the boundary layer region to better describe the airfoil shape in the LES. Two inlet end-wall boundary layers that produce different secondary flow patterns are analyzed: a laminar thin velocity profile and a turbulent thick velocity profile with several inlet turbulent intensities. The agreement between LES numerical predictions and experimental measurements of the position and intensity of the secondary vortices is excellent for both cases. RANS simulations are much cheaper in terms of computational cost and reasonably predict most of the flow features, except when the inlet turbulence is low and turbulent transition prediction becomes critical. The effect of the inlet velocity profiles and inlet turbulence on the secondary flow structure is quite pronounced. The velocity profile thickness determines the spanwise penetration of the passage vortex, and different inlet turbulence intensities modify its mixing. Higher inlet turbulence intensities lead to a decrease of the secondary losses due to the passage vortex and an increase of end-wall losses.
Overall Cooling Effectiveness of Effusion Cooled and Thermal Barrier Coated Swirl Stabilized Liquid Fueled Combustor Liner in Reacting Flow Conditions
Authors: Ozogul Hamdullah , Tin Ibrahim Edhem 
Published: September 2023

Abstract
The combination of effusion cooling and thermal barrier coating has enabled to reach higher combustor temperatures, hence more efficient and powerful gas turbine engines over the last two decades. Effusion cooling and thermal barrier coating are favored for their low amount of coolant demand, high effectiveness and uniform structure. Moreover, it is also utilized in afterburner systems to pursue desired thrust for sufficient time.
The main purpose of the present research is to provide overall cooling effectiveness and heat transfer calculation method for state-of-art effusion cooled and thermal barrier coated (TBC) gas turbine combustion chambers. The rig has been designed to run in a reacting flow and to provide realistic conditions of a swirl stabilized, liquid fueled can type combustor with TBC and effusion cooling. The test campaign covered equivalence ratio from 0.35 to 0.6 and with a static pressure drop of 1%. The liner is laser drilled to obtain shallow holes with an angle of 25 degrees to form the effusion cooling scheme. The hole density is set to have staggered arrays with s/d = 9, which is considered to be a high hole density for TBC coated liners. Metal temperature measurements are taken with thermocouples from five equidistant axial locations. To develop simple 1D heat transfer method, while Net Heat Flux Reduction coefficient is generated from test data, effective flow area of flame side is calculated from CFD analysis. 1D thermal solver and coefficients are validated by means of different equivalence ratio and adiabatic flame temperatures.
Analysis of the Bifurcating Duct of an Inlet Particle Separator in Transonic Flow Conditions
Authors: Castaldi Marco , Mayo Ignacio , Demolis Jacques , Eulitz Frank 
Published: September 2023

Abstract
To increase the reliability of turboprop and turboshaft engines in extreme operating conditions, filtering protections such as Inlet Particle Separators (IPS) can be installed at the intake. The flow inside an IPS is highly 3D and unsteady, with fluctuations especially pronounced when transonic conditions are reached. Locally, shocks can occur, increasing the pressure losses. In this paper, we aim at providing the transonic analysis of an industrial IPS designed for aerodynamic lab testing. As a first step, we define the threshold beyond which sonic conditions are reached in the boundary cross sections of the IPS, in terms of inlet total pressure and Reynolds number, by means of a 1D semi-empirical model. Second, we select a critical configuration, very close to these conditions, and we perform CFD simulations to analyze the locations and evolution of the transonic flow inside the IPS. Different models are presented, i.e. steady and unsteady Reynolds-Averaged Navier-Stokes, Detached Eddy Simulation and Large Eddy Simulation, characterized by three levels of resolution (based on the grid size). The results show the evolution of some transonic shocks: the steady-state model is only providing information on averaged quantities, while the time-resolved simulations offer a more precise overview in the time domain (velocity and Mach number fluctuations). The analysis in the frequency domain reveals the frequencies of the transonic fluctuations, which can negatively affect the IPS. Finally, we discuss three alternative designs to effectively improve the operating range and mitigate the risks related to the transonic instabilities, comparing the differences in separation efficiency with respect to the baseline case. The results prove that the optimal design choice is given by the trade-off between operating range, pressure losses and separation efficiency.
Effects of Ignition Position and Inlet Pressure on Ignition Performances of a Centrally Staged Combustor
Authors: Zhang Chi , Hu Yingqi , Wang Jianchen , Liu Yan 
Published: September 2023

Abstract
For a centrally staged swirl combustion chamber, ignition performance is a critical issue. Because of the significant influence of the main stage airflow located in the outer layer of the dome, fuel droplets are not easily transported to the tip of the igniter. Also, the outer air layer exerts a strong convective effect on the flame core. In this paper, we mainly explore the ignition performance of the centrally staged combustor under ambient temperature and low-pressure conditions. The effects of different spark axial positions on the ignition characteristics were experimentally investigated in the range of 30.8–70.3 kPa inlet pressure of the combustion chamber. The results of ignition fuel air ratio under different combustion chamber air pressure drop conditions were obtained.
The results show that the trend of ignition fuel air ratio with pressure drop is different under different inlet pressure conditions. When the inlet pressure was 35.7KPa and 30.8KPa, the ignition fuel air ratio increased with the pressure drop, while the trend became opposite when the inlet pressure increased to 70.1Kpa near atmospheric pressure. For the ignition position, when the igniter is located at different positions in the recirculation zone of the combustion chamber, it will directly affect the ignition fuel air ratio and even determine whether the ignition can be successful. The results showed that the best ignition performance was achieved when the igniter was located at 57.6 mm from the combustion chamber sleeve. In addition, CFD analysis was performed. The differences in ignition boundaries were further explained by analyzing the flow field and the propagation path of the ignition kernal. From the analysis results of numerical simulation, it can be concluded that when the ignition position is located in the middle of the edge of the recirculation zone, the flame propagation time to the dome of the combustion chamber can be shortened and thus a better ignition boundary can be obtained.
The Hybrid Pathway to Flexible Power Turbines: Part B, Fast Data Transfer Methods Between Varying Fidelity Simulations, to Enable Efficient Conjugate Thermal Field Prediction
Authors: Baker Mark , Rosic Budimir 
Published: September 2023

Abstract
The global drive towards renewable energy is imposing challenging operating requirements on power turbines. Flexible load-leveling applications must accept more frequent and demanding start-stop cycles. Full transient analyses are too computationally expensive for real-time simulation across all operating regimes so monitoring relies on sparse physical measurements. Alone, these sparse data lack the fidelity for real-time prediction of a complex thermal field.
A novel hybrid methodology is proposed, coupling data across a range of fidelities to bridge the limitations in the individual analyses. Combining several fidelity methods in parallel; low-order models, corrected by real-time physical measurements, are calibrated with high-fidelity simulations. A newly developed low-order thermal network code is used to predict the thermal field in real-time. High-fidelity flow characteristics are routinely transferred to the decoupled low-order solution. A critical enabling feature of this hybrid approach is the fast data interpolation between differing fidelity numerical simulations.
This paper evaluates a spatial Kriging method for robust data transfer between two different fidelity mesh, tested in the case of thermal profile prediction of a power turbine. Additionally, a novel coordinate-based hash mapping process is demonstrated for the fast high-to-low fidelity data transfer. Localized hashing allows independent, parallel, nearest neighbor search at significantly reduced computational cost. The demonstrated method facilitates fast mesh pairing, necessary to support the real-time hybrid method for thermal field prediction during turbine transient operation.
Experimental Evaluation of Damping for Torsional Dynamic Calculations of a Turbomachinery Shaftline
Authors: Carassale Luigi , Gillon Stephen , Pallini Giovanni 
Published: September 2023

Abstract
Standard torsional rotordynamics modelling of large turbines considers steady state frequency response calculations with assumed damping values for torsional natural frequencies. A degree of conservatism is applied since torsional vibration is rarely monitored or evaluated in a commercial engine. Of particular interest, and the primary focus of [1], are torsional modes in the vicinity of 1x and 2x line frequency, which are potential sources of torsional excitation in the event of an electric fault. Typical blade-rotor interaction (BRI) torsional modes for large turbine – generator shaftlines can occur close to these frequencies, requiring significant effort during the design phase to ensure adequate separation. [1] acknowledges that while significant steps have been made in recent decades to enhance prediction of torsional natural frequencies for coupled blade-rotor systems, challenges remain in estimating torsional damping, particularly for BRI modes. This paper aims to re-examine the assumed damping values currently applied.
Torsional vibration data recorded during steady state operating conditions in Ansaldo’s gas turbine test centre have been used to estimate damping of torsional modes through an algorithm involving the spectral estimation by the wavelet transform, the system identification by the eigensystem realization algorithm and an iterative clustering procedure. This paper presents a description of the test facility and torsional vibration measurements, description of the algorithm, and damping results harvested from its application for the first seven modes of the shaftline for various load conditions. Several aspects of the results are discussed, notably a comparison between measured and assumed damping and dependence of torsional damping on generator active load.
Tuning Modal Behaviour of Additively Manufactured Lattice Structures
Authors: Beghini Marco , Grossi Tommaso , Macoretta Giuseppe , Monelli Bernardo Disma , Senegaglia Ivan , del Turco Paolo , Fardelli Andrea , Morante Francesco 
Published: September 2023

Abstract
Thanks to the increasingly widespread additive manufacturing technology and promising properties, the use of Lattice Structures (LS) is becoming increasingly frequent. LS allows the components to be designed with tunable stiffness, which can unlock the control of natural frequencies. However, crucial challenges must be faced to integrate LS into the typical design process. In the present work, an experimental and numerical study of LS-enabled tuning of natural frequencies in mechanical components is proposed. In a first step, the difficulties arising with the large amount of FEM nodes, that are required to predict LS complex shapes in detail, are overcome by modeling LS with an elastic metamaterial whose stiffness properties are determined through ad hoc finite element analyses. After that, a simplified investigation can be conducted on the modal properties of components with fixed external shape and variable internal LS filling, based on Triply Periodic Minimal Surfaces (TPMS) lattices. In those conditions, the parameters of the LS core can be tuned to control and optimize the global modal frequencies of the entire geometry. In addition, the admissible range of frequencies can be estimated. Optimized plates results are validated through an experimental test campaign on additively manufactured specimens made with Selective Laser Melting (SLM) technology. The samples are hammer-tested with various boundary conditions while laser sensors measure the oscillation data of selected points. Finally, estimated and identified natural frequencies were compared. The described model is suitable to be implemented in an automated tool for designers.
Evaluation of Empirical Loss Models for Base Drag Prediction of sCO2 Axial Turbine Aerofoils
Authors: Kumaran R. Senthil , P. P. Sharath , Alone Dilipkumar B. , Kumar Pramod 
Published: September 2023

Abstract
Axial flow turbines can be efficiently designed and used in megawatt scale sCO2 closed Brayton power systems. Empirical loss models are required for design and optimization of axial turbines. Ample loss models are available in the open literature for air and steam based axial turbines. But no loss models have been reported so far exclusively for sCO2 applications. Constructing a complete loss model for sCO2 turbomachinery is farfetched until loads of data are generated from cascade tunnels and turbomachinery test rigs with sCO2 as the operating fluid medium. Unlike air and steam, which are approximated as ideal gases, sCO2 is a real gas. Nevertheless, designers and commercial turbomachinery design softwares use corrected versions of these existing loss models for sCO2 turbine design. The profile loss / base drag contributes to 50–60 % of overall losses in an axial turbine. Estimation of base profile drag is important at the beginning of the design phase of the turbine in order to maximize the power output and efficiency. An attempt has been made in this paper to evaluate some of the well proven axial turbine loss models like Ainley & Mathieson, Dunham & Came, Kacker & Ockappu, Aungier etc. for estimating base profile drag of an sCO2 axial turbine aerofoil. The aerofoil investigated in the present study has been designed for a 10 MW sCO2 axial turbine stator. Profile drag of the aerofoil was computed from full turbine 3D CFD and 3D cascade CFD simulations with sCO2 fluid medium. Turbine CFD simulations were carried out using pressure based ANSYS CFX RANS solver with SST turbulence model. 3D cascade CFD simulations were carried out using pressure based ANSYS Fluent RANS solver with SST k-ω turbulence model. sCO2 fluid properties were modelled using Refrigerant Gas Property tables generated from NIST Refprop database. It would of great interest to see if cascade wind tunnel data generated with air can be applied to sCO2 turbine design. In this context, cascade test experiments were carried out for a 10 bladed linear cascade model of the aerofoil in a high-speed cascade wind tunnel at CSIR-NAL. The aerofoil performance was investigated at the design condition and over a range of off-design conditions. The base profile drag data obtained using the loss models, CFD simulations and cascade test experiments are compared and discussed in detail. This study shows that loss models developed for air-based turbines can be efficiently used to predict base profile drag of sCO2 turbines with corrections. It is also inferred that the cascade wind tunnel data can be a useful tool to study sCO2 aerofoils.