bluuebunny/crossref_metadata_2025_split huggingface dataset:
Re-Oriented POD for Feature Extraction From Time Resolved Reacting Flow Datasets
Authors: Ek H. , Proscia W. , Lieuwen T. , Emerson B. 
Published: November 2019

Abstract
Recent improvements in computational and experimental combustion have led to an increased availability of high-fidelity data sets. With the surge of high-quality data, the reduction and analysis of this information become a key aspect in improving our understanding of highly dynamic, reacting flow fields. This work utilizes simultaneous high-speed stereoscopic particle image velocimetry (sPIV), OH-planar laser induced fluorescence (PLIF) and fuel-PLIF measurements in a high pressure, liquid fueled swirl combustor. This work extends one of the most commonly used modal analysis techniques, proper orthogonal decomposition (POD). Instead of decomposing the data as a series of time coefficients and spatial modes, which is the result of snap-shot POD, the data is re-oriented such that the coefficients are a function of the transverse distance and the modes are a function of axial distance and time. This reoriented POD method, referred to as spatio-temporal POD, allows us to directly target convective flow structures while still extracting the same types of information as from snap-shot POD. Additionally, since the modes contain temporal information, phase speeds associated with the convective structures can easily be calculated from the phase portraits. This paper presents results of this analysis, allowing us to track the growth of coherent structures, their phase speeds, and their subsequent decay.
Effect of Blade Row Interaction on Rotor Film Cooling
Authors: Brind James , Pullan Graham 
Published: November 2019

Abstract
The mechanisms of blade row interaction affecting rotor film cooling are identified in order to make recommendations for the design of film cooling in the real, unsteady turbine environment. Present design practice makes the simplifying assumption of steady boundary conditions, despite intrinsic unsteadiness due to blade row interaction; we argue that if film cooling responds non-linearly to unsteadiness, the time-averaged performance will then be in error. Non-linear behaviour is confirmed using experimental measurements of flat-plate cylindrical film cooling holes, main-stream unsteadiness causing a reduction in film effectiveness of up to 31% at constant time-averaged boundary condition. Unsteady computations are used to identify the blade row interaction mechanisms in a high-pressure turbine rotor: a ‘negative jet’ associated with the upstream vane wake, and frozen and propagating vane potential field interactions. A quasi-steady model is used to predict unsteady excursions in momentum flux ratio of rotor cooling holes, with fluctuations of at least ±30% observed for all hole locations. Computations with modified upstream vanes are used to vary the relative strength of wake and potential field interactions. In general, both mechanisms contribute to rotor film cooling unsteadiness. It is recommended that the designer should choose a cooling configuration which behaves linearly over the expected unsteady excursions in momentum flux ratio as predicted by a quasi-steady hole model.
Multidisciplinary Design Optimization of a Bladed Disc for Small-Size Gas-Turbine Engines
Authors: Salnikov Anton , Danilov Maxim 
Published: November 2019

Abstract
One of the most important units of small-size gas-turbine engines (GTE) is a turbine bladed disk, since it determines the total engine efficiency. Designing a turbine disks is a complex challenge due to the high loads and a large number of structural and technological constraints, as well as a variety of requirements to the bladed disks for small-size GTEs (higher efficiency, lower mass and adequate strength characteristics, etc.).
Diverse requirements to the turbine bladed disks mean that modifying the structure in order to improve some characteristics will degrade other characteristics. A standard solution to this problem is to use the iterative approach, which reduces the design process to a consecutive iteration of setting and solving design problems concerning the bladed disk elements (blade and disk) separately for different aspects. The main drawback of this approach is its tremendous labor intensity and inferior quality of design, as this procedure does not consider the design object as a single entity.
This paper proposes an approach to the turbine bladed disks design based on the use of a single multidisciplinary parametrized 3D model that contains several specialized submodels. These submodels define the essential computational regions, as well as the characteristics of the physical processes and phenomena in the object under study. The model also enables integration and interaction of the submodels in a single computational region.
The single multidisciplinary model is modified and analyzed automatically, so the design problem is transformed into a multi-criteria optimization problem where the weight, gas dynamic and strength characteristics are used as criteria or constraints, and they are improved by varying the geometric parameters of the blade and disk.
Each submodel simulates and analyzes the essential characteristics at the level comparable to the standard engineering calculations. Therefore, the designs obtained as a result of optimization do not need significant improvements, which facilitates and enhances the design process.
The development of an integrated model is time consuming, but since the design and operation of bladed disks are similar, the created parametrized multidisciplinary 3D model can be used in the design of other similar disks after minor alternations taking into account the specifics of the new task.
Scaling Flat Plate, Low Temperature Adiabatic Effectiveness Results Using the Advective Capacity Ratio
Authors: Fischer Jacob P. , Rutledge James L. , McNamara Luke J. , Polanka Marc D. 
Published: November 2019

Abstract
Effective design of film cooled engine components requires the ability to predict behavior at engine conditions. This is commonly accomplished through low temperature testing on scaled up geometries. The adiabatic effectiveness, η, is one indicator of the performance of a film cooling scheme. Performing an experiment to measure η in a low temperature wind tunnel requires appropriate selection of the coolant flow rate. Perhaps the most common flow rate parameter that is used to characterize the coolant flow relative to the freestream is the mass flux ratio, or blowing ratio, M. This is usually used in lieu of the velocity ratio to account for the fact that the density of the coolant is typically much larger than that of the hot freestream gas. Numerous studies have taken place evaluating the ability of M to properly scale the effects of density ratio and its performance has produced mixed results. The momentum flux ratio, I, is an alternative that is also found to have mixed success, leading some to recommend matching the density ratio to allow simultaneous matching of M and I. Nevertheless, widely varying results in the literature regarding the efficacy of these coolant flow rate parameters to scale the density ratio suggests there may be other largely ignored effects playing a role in the thermal physics.
In the present work, thermal experiments were performed to measure adiabatic effectiveness on a flat plate with a single 7-7-7 shaped hole. Various coolant gases were used to give a large range of thermodynamic property variations. It is shown that a relatively new coolant flow rate parameter that accounts for not only density variations but also specific heat variations, the advective capacity ratio (ACR), far exceeds the ability of either M or I to provide matched adiabatic effectiveness between the various coolant gases that exhibit extreme property differences. Particularly considering that the specific heat of the coolant in an engine is significantly lower than the specific heat of the freestream gas, ACR is shown to be appropriate for characterizing non-separating coolant flow situations.
Modelling the Transient Behaviour of Gas Turbines
Authors: Petkovic Djordje , Banjac Milan , Milic Srdjan , Petrovic Milan V. , Wiedermann Alexander 
Published: November 2019

Abstract
As a consequence of the increasing share of renewable energy sources in present-day electrical grid systems, time variations of the power demand for fossil fuel plants can become more sudden. Therefore, an ability to respond to sudden load changes becomes an important issue for power generation gas turbines. This paper describes a real-time model for predicting the transient performance of gas turbines. The method includes basic transient phenomena, such as volume packing and the heat transfer between the working fluid and the structural elements. The dynamics of components are quantified by solving ordinary differential equations with appropriate initial and boundary conditions. Compressor and turbine operating points are determined from corresponding performance maps previously calculated using sophisticated aerodynamic, through-flow codes. This includes a sufficient number of such characteristics to account for the variations in speed and machine geometry. The developed dynamic model was verified by comparison of simulation results with experimentally recorded operating parameters for a real engine. This includes the start-up sequence and the change of load. Additional simulation covers the system response to a step increase in fuel flow. The simulation is carried out faster than the real process.
Synchrotron XRD Measurements of Thermal Barrier Coating Configurations With Rare Earth Elements for Phosphor Thermometry
Authors: Haldar Sandip , Warren Peter , Fouliard Quentin , Moreno David , McCay Mary , Park Jun Sang , Kenesei Peter , Almer Jonathan , Ghosh Ranajay , Raghavan Seetha 
Published: November 2019

Abstract
The development of temperature sensing Thermal Barrier Coating (TBC) systems by phosphor thermometry has significant potential to achieve accurate non-destructive temperature measurement in the coating. The doping of coatings using rare earth elements is a viable option to enable the temperature measurement by the virtue of their luminescence. While facilitating the temperature sensing, however, the thermo-mechanical and thermo-chemical stability of the coating must be maintained under extreme operating conditions. In this work, TBC configurations including a doped layer placed at the top or the bottom of the top coat have been fabricated via Air Plasma Spray (APS) using Yttria-Stabilized Zirconia (YSZ) that contains Europium (Eu) dopant. The TBC configurations have been characterized using high energy synchrotron X-ray diffraction (XRD) at both room temperature and high temperature. The TBC samples have been subjected to a single cycle thermal load during XRD data collection. The residual strain in the top coats of the TBCs have been quantified using XRD data. Residual strain in the top coat of the regular TBC configuration has been measured to be in the range of −0.8 × 10−4 to −1.0 × 10−4 for out-of-plane strain (e11) and 0.5 × 10−4 to 2.0 × 10−4 for in-plane strain (e22). The doped layer above the top coat was found to most significantly affect the spatial strain distribution across depth in the YSZ layer by increasing the strain magnitudes closer to the bond coat. However, the difference in strain distribution due to doped layers was found to be less than 1.0 × 10−4, which is close to the experimental limit. Thus, the doped layer did not significantly alter the overall residual strain states of the coating.
Power-Density vs Efficiency Trade-Off for a Recuperated Inside-Out Ceramic Turbine (ICT)
Authors: Picard B. , L.-Blais A. , Picard M. , Rancourt D. 
Published: November 2019

Abstract
Recuperated cycles can significantly increase the efficiency of small gas turbines that are today operating with low pressure ratios and uncooled or lightly cooled turbine blades. However, for mass-driven applications such as aeroengines, the efficiency benefit is typically outweighed by the increased weight associated with the heat exchanger (HX). Increase in specific power could overcome this penalty by reducing the mass flow through the system and therefore its weight and size. To do so, the Turbine Inlet Temperature (TIT) must be increased by ∼250 K over state-of-the-art small gas turbines. The Inside-out Ceramic Turbine (ICT) propose a new path to increase TIT of small turbines, where blade cooling schemes are impractical and costly. This new architecture increases the achievable TIT by using ceramic blades loaded in compression under centrifugal loads supported by an air-cooled rotating composite rim. This paper provides a system-level evaluation of the power-density to efficiency trade-off for the sub-megawatt class turbines using the ICT configuration. The numerical simulation includes 3 submodels to provide cycle efficiency and mass estimates for various cycle and HX design: (1) a station-based thermodynamic model; (2) a 1D-FEM HX model for a straight counterflow recuperator; and (3) a system-level mass model of the recuperated engine configured for a turboprop or turboshaft. At a TIT of 1550 K, the optimal ICT configuration provides a power density of 3 kW/kg and 40% thermal efficiency, which is 4 times lighter than recuperated turbines at 1300 K for the same efficiency level. Further increase in TIT to 1800 K would reach current state-of-the-art turboprop power densities (up to 5 kW/kg) while still achieving over 40% thermal efficiency or — for applications where power density can be traded for efficiency — up to 50% thermal efficiency while maintaining low pressure ratios and associated simplicity.
Surge and Stall Detection Using Acoustic Analysis for Gas Turbine Hybrid Cycles
Authors: Cabrera Cruz Keishaly , Pezzini Paolo , Shadle Lawrence , Bryden Kenneth M. 
Published: November 2019

Abstract
Compressor dynamics were studied in a gas turbine – fuel cell hybrid power system having a larger compressor volume than traditionally found in gas turbine systems. This larger compressor volume adversely affects the surge margin of the gas turbine. Industrial acoustic sensors were placed near the compressor to identify when the equipment was getting close to the surge line. Fast Fourier transform (FFT) mathematical analysis was used to obtain spectra representing the probability density across the frequency range (0–5000 Hz). Comparison between FFT spectra for nominal and transient operations revealed that higher amplitude spikes were observed during incipient stall at three different frequencies, 900, 1020, and 1800 Hz. These frequencies were compared to the natural frequencies of the equipment and the frequency for the rotating turbomachinery to identify more general nature of the acoustic signal typical of the onset of compressor surge. The primary goal of this acoustic analysis was to establish an online methodology to monitor compressor stability that can be anticipated and avoided.
A Statistical Imputation Method for Handling Missing Values in Generalized Polynomial Chaos Expansions
Authors: Andrews Mark , Jones Gavin , Leyde Brian , Xiong Lie , Xu Max , Chien Peter 
Published: November 2019

Abstract
Generalized Polynomial Chaos Expansion (gPCE) is widely used in uncertainty quantification and sensitivity analysis for applications in the aerospace industry. gPCE uses the spectrum projection to fit a polynomial model, the gPCE model, to a sparse grid Design of Experiments (DOEs). The gPCE model can be used to make predictions, analytically determine uncertainties, and calculate sensitivity indices. However, the model’s accuracy is very dependent on having complete DOEs. When a sampling point is missing from the sparse grid DOE, this severely impacts the accuracy of the gPCE analysis and often necessitates running a new DOE. Missing data points are a common occurrence in engineering testing and simulation. This problem complicates the use of the gPCE analysis.
In this paper, we present a statistical imputation method for addressing this missing data problem. This methodology allows gPCE modeling to handle missing values in the sparse grid DOE. Using a series of numerical results, the study demonstrates the convergence characteristics of the methodology with respect to reaching steady state values for the missing points. The article concludes with a discussion of the convergence rate, advantages, and feasibility of using the proposed methodology.
Fan Flow Field in an Installed Variable Pitch Fan Operating in Reverse Thrust for a Range of Aircraft Landing Speeds
Authors: Rajendran David John , Pachidis Vassilios 
Published: November 2019

Abstract
The installed flow field for a Variable Pitch Fan (VPF) operating in reverse thrust for the complete aircraft landing run is described in this paper. To do this, a VPF design to generate reverse thrust by reversing airflow direction is developed for a representative 40000 lbf modern high bypass ratio engine. Thereafter, to represent the actual flow conditions that the VPF would face, an engine model that includes the nacelle, core inlet splitter, outlet guide vanes, bypass nozzle, core exhaust duct, aft-body plug and core nozzle is designed. The engine model with the VPF is attached to a representative airframe in landing configuration to include the effects of installation. A rolling ground plane that mimics the runway during the landing run is also included to complete the model definition. 3D RANS solutions are carried out for two different VPF stagger angle settings and rotational speeds to obtain the fan flow field.
The dynamic installed VPF flow field is characterized by the interaction of the free stream and the reverse stream flows. The two streams meet in a shear layer in the fan passages and get deflected radially outwards before turning back onto themselves. The flow field changes with stagger setting, fan rotational speed and the aircraft landing speed because of the consequent changes in the momentum of the two streams. The description of the installed VPF flow field as generated in this study is necessary to: a) qualify VPF designs that are typically designed by considering only the uninstalled static flow field b) choose the VPF operating setting for different stages of the aircraft landing run.
Modeling the Torsional Cyclic Response of Direct Metal Laser Sintered Inconel 718
Authors: Siddiqui Sanna F. , Irmak Firat , O’Nora Nathan , Gordon Ali P. 
Published: November 2019

Abstract
The aerospace propulsion industry has seen strides in the use of the additive manufacturing (AM) technology in the rapid prototyping and geometric design flexibility of aerospace parts, with concurrent efforts on 3D printing turbine engine blades of Inconel 718 material [1] for use in aircraft engines. The tensile, compressive and axial fatigue response of AM Inconel 718, along with associated constitutive modeling of the material response exhibited under these mechanical test conditions have been reported. However, in addition to understanding the axial behavioral response exhibited by this material, assessing the role of cyclic shear stresses, through experimental testing and constitutive modeling can provide preliminary insight into the mechanical behavior of AM Inconel 718 under multiaxial loading conditions. This study has presented a novel approach to constitutively model the experimental cyclic shearing deformation of as-built direct metal laser sintered (DMLS) Inconel 718, manufactured along varying build orientations in the xy, yz and xz planes, compared with wrought annealed Inconel 718. Specimens were subjected to completely reversible torsional fatigue tests at room temperature, under angle of twist control. The experimental cyclic shearing response was modeled through the use of the Chaboche model, from which optimized constants are reported with build orientation; and the specimen deformation, under angle of twist control, was captured through a finite-element simulation model of the cylindrical gauge section of the specimens. Overall this study yields a comprehensive understanding of the experimental and modeled cyclic shearing response of an additively manufactured metal, which is vital to develop these components to be conducive for the multiaxial fatigue conditions to which they are subjected to in the gas turbine industry.
Linear Cascade and Wind Tunnel Development for Turbine Blade Tip Heat Transfer Investigations With and Without Film Cooling
Authors: Sampson Michael , Fairbanks Avery , Moseley Jacob , Ligrani Phillip M. , Xu Hongzhou , Fox Michael 
Published: November 2019

Abstract
Currently, there is a deficit of experimental data for surface heat transfer characteristics and thermal transport processes associated with tip gap flows, and a lack of understanding of performance and behavior of film cooling as applied to blade tip surfaces. As a result, many avenues of opportunity exist for development of creative tip configurations with innovative external cooling arrangements. Overall goals of the present investigations are to reduce cooling air requirements, and reduce thermal loading, with equivalent improvements of thermal protection and structural integrity. Described is the development of experimental facilities, including a Supersonic/Transonic Wind Tunnel and linear cascade, for investigations of surface heat transfer characteristics of transonic turbine blade tips with unique squealer geometries and innovative film cooling arrangements. Note that data from past investigations are used to illustrate some of the experimental procedures and approaches which will be employed within the investigation. Of interest is development of a two-dimensional linear cascade with appropriate cascade airfoil flow periodicity. Included are boundary layer flow bleed devices, downstream tailboards, and augmented cascade inlet turbulence intensity. The present linear cascade approach allows experimental configuration parameters to be readily varied. Tip gap magnitudes are scaled so that ratios of tip gap to inlet boundary layer thickness, ratios of tip gap to blade axial chord length, and ratios of tip gap magnitudes to blade true chord length match engine hardware configurations. Ratios of inlet boundary layer thickness to tip gap range from 3 to 5. Innovative film cooling configurations are utilized for one blade tip configuration, and scaled engine components are modelled and tested with complete external cooling arrangements. Blade tip and geometry characteristics are also considered, including squealer depth and squealer tip wall thickness. With these experimental components, results will be obtained with engine representative transonic Mach numbers, Reynolds numbers, and film cooling parameters, including density ratios, which are achieved using foreign gas injection with carbon dioxide. Transient, infrared thermography approaches will be employed to measure spatially-resolved distributions of surface heat transfer coefficients, adiabatic surface temperature, and adiabatic film cooling effectiveness.