bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bayesian Analysis of In-Situ High-Resolution X-Ray Diffraction Synchrotron Experiments of Ti-6Al-4V Specimens Undergoing Tensile Loading
Authors: Armstrong Nicholas , Lynch Peter A. , Kada Sitarama R. , Cizek Pavel , Kimpton Justin A. , Antoniou Ross A. 
Published: November 2019

Abstract
Linking the accumulation of microstructural damage prior to crack initiation to the lifing of aero-engines components would help to better predict the time that a component spends in this crack initiation stage.
We present the results and analysis of in-situ high-resolution X-ray diffraction (XRD) experiments of a Ti-6Al-4V specimen that experienced tensile loading using medium energy synchrotron X-rays (≤ 21 keV) carried out at the Australian Synchrotron. The XRD analysis characterised XRD line-broadening due to the build-up of dislocations and the formation of crystallites in α- and β-Ti-6Al-4V specimens. Using Bayesian XRD analysis methods, the density, spatial arrangement of dislocations, and crystallite size information for α- and β-phases of the Ti-6Al-4V was extracted from the XRD line-profiles, as a function of applied load. The XRD analysis was then compared and validated with transmission electron microscopy (TEM) analysis of the specimen before and after the loading. Comparison of the TEM and XRD analysis reveals broad agreement in terms of the microstructural damage of Ti-6Al-4V specimens.
Turning Dynamic Sensor Measurements From Gas Turbines Into Insights: A Big Data Approach
Authors: Karlstetter Roman , Widhopf-Fenk Robert , Hermann Jakob , Rouwenhorst Driek , Raoofy Amir , Trinitis Carsten , Schulz Martin 
Published: November 2019

Abstract
Gas turbine power plants generate an ever growing amount of high frequency dynamic sensor data. One of the applications of this data is the protection against problems induced by combustion dynamics, as, e.g., with the ArgusOMDS system developed by IfTA. In the light of digitalization, this data has the potential to also be used in other areas and ultimately transform maintenance, repair and overhaul approaches. However, current solutions are not designed to cope with the large time windows needed for a general analysis and this can hinder development of advanced machine analysis algorithms. In this work, we present an end-to-end approach for large scale sensor measurement analysis, employing data mining techniques and enabling machine learning algorithms. Our approach covers the complete data pipeline from sensor measurement acquisition to analysis and visualization. We demonstrate the feasibility of our approach by presenting several case studies that prove the benefits over existing solutions.
Numerical Investigations on the Power Generation of Turbo-Expander During the Propane De-Hydrogenation Process
Authors: Kwon Hwabhin , Park Heesung 
Published: November 2019

Abstract
A turboexpander for the propane de-hydrogenation process with blade and splitter has been numerically investigated. Since the turboexpander expands fluid from higher inlet pressure to lower discharge pressure, the kinetic energy of fluid is converted into useful mechanical energy. The efficiency and power generation with the designed turboexpander have been simulated with different operating conditions. The pressure ratio between inlet and outlet and rotational speed are varied to characterize the performance of the turboexpander as an electrical power generator. The numerical simulations have shown the vortex at the trailing edges of blade and splitter which decreases the efficiency. The rotational speed and the pressure ratio are parameterized to obtain operation conditions which achieve high power generation and efficiency. Consequently, the generated power from 614.12 kW to 693.45kW is obtained at the normal rotational speed and the pressure ratio between 1.75 to 2.22.
The Preliminary CFD Design of a Compressor and Combustor System Towards a 100 kW Hydrogen Fuelled Micro Gas Turbine
Authors: Devriese C. , Pennings W. , de Reuver H. , Bastiaans R. , De Paepe W. 
Published: November 2019

Abstract
Within the context of an ever-increasing share of wind, solar and emerging tidal power, the need to store energy, not only on the short term, but also in the medium to long-term to balance out the power grid will become more important in the near future. One of the most promising routes for this mid- to long term storage, is to produce hydrogen through electrolysis using excess electricity and store it. Instead of using this hydrogen then to generate electricity in a conventional, large, power plant, a more efficient route is to use it in a Decentralised Energy System (DES) using micro Gas Turbines (mGTs). Although the mGT presents itself as a promising option to convert pure hydrogen into electricity in this DES framework, several challenges, linked to the necessary increase of Turbine Inlet Temperature (TIT) for efficiency increase to make the unit compatible and the use of pure hydrogen in the combustor, still need to be overcome. In this paper we present the first steps towards a fully hydrogen fuelled mGT. Firstly, a full thermodynamic cycle analysis was performed to determine the optimal operating parameters, such as compressor pressure ratio and mass flow rate, air-to-fuel ratio and TIT. Secondly, a full CFD design and optimisation of the compressor and the combustion chamber was performed (steady and transient RANS and LES). CFD simulations of the compressor and combustion chamber matched the 1D performance calculations and also reached the desired performance goals. This CFD supported validation of the component performance shows that the design of a pure hydrogen combustion chamber for mGT applications is possible.
A Pneumatic Probe for Measuring Spatial Derivatives of Stagnation Pressure
Authors: Clark C. J. , Grimshaw S. D. 
Published: November 2019

Abstract
This paper introduces a pneumatic 9-hole probe which can measure flow angles, stagnation and static pressures, and spatial derivatives of stagnation pressure. It does this through direct measurement at a single location, rather than empirical corrections using measurements at multiple points.
The new design resembles a 5-hole probe with 4 additional holes positioned around the side of the probe head. This arrangement enables the probe to distinguish between flows with stagnation pressure gradient and flows at an angle. Mapping between the inputs, the probe hole pressures, and outputs, the calibration reference measurements, is achieved with a trained neural network which takes the place of a conventional calibration map.
Measurements of an unknown wake are performed in a calibration tunnel. The 9-hole probe data is compared with measured reference data and a “conventional” analysis of the 5 forward facing holes. The 5-hole probe analysis results in a maximum yaw angle error of 8.4°, while the 9-hole probe matches the reference to within 0.8°. Mass-averaged stagnation pressure and kinetic energy loss coefficients, evaluated with the 5-hole probe analysis, result in errors of +2.8% and −48% respectively, while the 9-hole probe gives +0.5% and −4.5%.
The new probe is used to perform an area traverse of an inlet guide vane in a research compressor. The 5-hole probe analysis gives a ±5.5° variation in yaw angle across the wake and this reduces to ±1.0° when the 9-hole probe is used. Measurement of stagnation pressure gradient and curvature, based on single point measurements, is also demonstrated.
Using Machine Learning to Predict Core Sizes of High-Efficiency Turbofan Engines
Authors: Tong Michael T. 
Published: November 2019

Abstract
With the rise in big data and analytics, machine learning is transforming many industries. It is being increasingly employed to solve a wide range of complex problems, producing autonomous systems that support human decision-making. For the aircraft engine industry, machine learning of historical and existing engine data could provide insights that help drive for better engine design. This work explored the application of machine learning to engine preliminary design. Engine core-size prediction was chosen for the first study because of its relative simplicity in terms of number of input variables required (only three). Specifically, machine-learning predictive tools were developed for turbofan engine core-size prediction, using publicly available data of two hundred manufactured engines and engines that were studied previously in NASA aeronautics projects. The prediction results of these models show that, by bringing together big data, robust machine-learning algorithms and automation, a machine learning-based predictive model can be an effective tool for turbofan engine core-size prediction. The promising results of this first study paves the way for further exploration of the use of machine learning for aircraft engine preliminary design.
Enhancement of Film Cooling Effectiveness Using Dean Vortices
Authors: Chen Pingting , Wang Lang , Li Xueying , Ren Jing , Jiang Hongde , Simon Terrence 
Published: November 2019

Abstract
Film cooling technology is widely used in gas turbines. Improvement of gas turbine thermal efficiency, specific power and specific thrust can be achieved by reducing the use of cooling air by improvements on film cooling technology. Experimental and numerical efforts have demonstrated that cooling effectiveness is reduced when kidney vortices created as the emerging film cooling jet flow interacts with the passage flow resulting in coolant lift-off and mixing. With higher blowing ratios, M, these kidney vortices become stronger and effectiveness worsens. Different technologies have been developed to enhance film cooling effectiveness by manipulating the kidney vortices. Some reduce local blowing ratios and local injection angles with expanded hole exits, called shaped holes. Others are employing hole geometries in an attempt to establish anti-kidney vortices in the flow field to weaken the effects of kidney vortices. Most of these film cooling technologies focus on methods that are within the present limits of manufacturing technology. However, with the additive manufacturing anticipated in the future, there will be more freedom in film cooling hole design. Exploiting this freedom, the present authors tried using curved holes to generate Dean vortices within the delivery line. These vortices have opposite direction of rotation to the vorticity of the kidney vortices and, thus, there is interaction between these vortices in the mixing region. It is shown that as a result of the inclusion of Dean vortices, the curved hole delivery leads to enhanced film cooling effectiveness.
Numerical results, including film cooling effectiveness values, tracking of vortices in the flow field, heat transfer coefficients, and net heat flux reduction are compared between the curved hole (CH), round hole (RH) and a laidback, fan-shaped hole (SH) with blowing ratios, M, of 0.5, 1.0, 1.5, 2.0 and 2.5. The laidback, fan-shaped hole represents the state of the art in film cooling hole design. Another curved hole (RCH) with the opposite (to the CH hole) curvature of delivery line is checked for comparison, with M = 1.5. The comparison shows that film cooling effectiveness values with the CH curved hole are higher than those with cylindrical film cooling holes at every blowing ratio studied. The curved hole has lower film cooling effectiveness values than the laidback, fan-shaped holes when M = 0.5 and 1.0, but shows advantages when the blowing ratio is higher than 1.0. With the interaction between Dean vortices and kidney vortices when using curved holes, a large amount of coolant re-attaches to the wall after moving streamwise for some distance, providing improved downstream film cooling performance. There is heat transfer enhancement for the curved hole case due to a higher kinetic energy transferred to the near-wall region, however. Nevertheless, the curved hole still displays a higher net heat flux reduction (NHFR) when the blowing ratio is high.
Implementation of Adaptive Gaussian Quadrature for Improved Accuracy of Boundary Element Methods Applied to Three Dimensional Geometries
Authors: Davies Michael , Saverin Joseph 
Published: November 2019

Abstract
An adaptive Gaussian quadrature method for characterizing flow over three dimensional bodies via a boundary element method using isoparametric quadrilateral elements with non-constant source and dipole strengths has been developed and tested. This method is compared to state-of-the-art methods: flat elements with constant strengths, flat elements with bilinear strengths, and twisted elements with constant dipole strengths. As such, an overview of current boundary element methods is provided.
The method developed here for twisted elements with non-constant source and dipole strengths is advantageous in that it both better approximates the actual geometry of the surface and the distribution of the dipole and source strengths. The majority of current methods are lacking at least one of these attributes.
The developed method has been validated by comparison to two known analytical solutions: a non-lifting ellipsoid and a Kármán-Trefftz airfoil. The flexible and robust procedure presented here results in improved accuracy of the solution to the Laplace equation around three dimensional bodies.
Second Law Analysis of an Energy Storage System Consisting of an Electrolysis Plant and the Graz Cycle With Internal H2/O2 Combustion
Authors: Dybe Simeon , Tanneberger Tom , Stathopoulos Panagiotis 
Published: November 2019

Abstract
The expansion of renewable energy generation must go hand in hand with measures for reliable energy supply and energy storage. A combination of hydrogen and oxygen as storing media provided from electrolysis at high pressure and zero emission power plants is a very promising option. The Graz cycle is an oxy-fuel combined power cycle that can operate with internal H2/O2 combustion and steam as working fluid. It offers thermal efficiencies up to 68.5% (LHV). This work applies a second law analysis to the Graz cycle and determines its exergetic efficiency. Exergy destruction is broken down to the cycle’s components thus providing insights on the location and magnitude of the cycle’s inefficiencies. A sensitivity analysis identifies the cycle’s exergetic and energetic efficiency as a function of representative parameters, offering an approach for future improvements. The combination of the cycle with an electrolysis plant is subsequently analyzed as an electric energy storage system. The round trip efficiency of the storage and back conversion system is computed by taking into account the additional compression of the reactants. As part of this analysis, the effect of the electrolyzer’s operational pressure is studied by comparing several commercial electrolyzers.
Experimental Evaluation of Heat Transfer in a High Temperature High Pressure Test Facility
Authors: Ramesh S. , Robey E. , Straub D. , Black J. 
Published: November 2019

Abstract
Performance of film cooling holes is generally evaluated near ambient conditions, so scaling the film cooling performance from ambient to engine conditions is important. These performance metrics can be reported in terms of net heat flux reduction, heat transfer enhancement, and effectiveness. There are several challenges and penalties in conducting experiments on a real engine or even on a stationary flat plate test article at near engine conditions. In this study, an experimental methodology capable of delivering film cooling performance for the experiments conducted in the high-temperature high-pressure test facility at NETL will be explored. More specifically, this study focuses on various challenges that are present and how these concerns are addressed to evaluate the heat transfer coefficient on the test article. Steady state experiments were conducted on a flat plate test article whose surface temperature distribution was obtained using an IR camera calibrated with a combination of bench top experiments and in-situ calibrations based on embedded thermocouple measurements. A detailed radiation analysis is conducted to enable differentiation of heat transfer by convection from heat transfer by radiation. The estimated surface heat flux and heat transfer coefficient were found to be higher than the one obtained from flat plate correlation.
Demonstration of a Dynamic Clearance Seal in a Rotating Steam Test Facility
Authors: Messenger Andrew , Williams Richard , Ingram Grant , Hogg Simon , Reggentin Philip 
Published: November 2019

Abstract
This paper reports on the latest phase of the development of a new rotating machinery sealing technology, which was a successful seal test in a high temperature steam test facility at TU Brauschweig in Germany.
The “Aerostatic Seal” is a dynamic clearance seal that is capable of maintaining very small clearances with a rotor and has the potential for a wide range of rotating machinery applications. It has been developed in recent years at Durham University, UK, in collaboration with a major OEM, with a focus on steam turbine sealing, and has previously been reported on in a number of ASME Turbo Expo papers. Previous work has reported on the design tool, and two air test facilities; testing in steam addressed the effect of high temperature components and the working fluid, and was an opportunity to verify the design system.
The seal is a development of a retractable gland seal and so in a low load condition it is retracted from the rotor with a large rotor clearance and then when the pressure ratio is sufficient moves to an operational small clearance. At its operational clearance the seal is capable of moving with rotor vibrations which means the design clearance can be smaller than any expected rotor movement. The benefits include a significant reduction in leakage when compared to conventional sealing technologies and also the ability to react to large transients or thermal growths caused by rapid changes in machine loads and speeds. The seal is shown to operate well in this environment and this work moves the technology closer to deployment in industry.
On the Effect of Inflow Disturbances on the Flow Past a Linear LPT Vane Using Spectral/hp Element Methods
Authors: Cassinelli Andrea , Xu Hui , Montomoli Francesco , Adami Paolo , Vazquez Diaz Raul , Sherwin Spencer J. 
Published: November 2019

Abstract
The recent development and increasing integration of high performance computing, scale resolving CFD and high order unstructured methods offers a potential opportunity to deliver a simulation-based capability (i.e. virtual) for aerodynamic research, analysis and design of industrial relevant problems in the near future. In particular, the tendency towards high order spectral/hp element methods is motivated by their desirable dispersion-diffusion properties, that are combined to accuracy and flexibility for complex geometries. Previous work from the Authors focused on developing guidelines for the use of these methods as a virtual cascade for turbomachinery applications. Building on such experiments, the present contribution analyzes the performance of a representative industrial cascade at moderate Reynolds number with various levels and types of inflow disturbances, adopting the incompressible Navier-Stokes solver implemented in the Nektar++ software framework. The introduction of a steady/unsteady spanwise-nonuniform momentum forcing in the leading edge region was tested, to break the flow symmetry upstream of the blade and investigate the change in transition mechanism in the aft portion of the suction surface. To provide a systematic synthetic turbulence generation tool, a parallelised version of Davidson’s method is incorporated and applied for the first time in the software framework to a low pressure turbine vane. The clean results of the cascade are compared to various levels of momentum forcing and inflow turbulence, looking at blade wall distributions, wake profiles and boundary layer parameters. Low levels of background disturbances are found to improve the agreement with experimental data. The results support the confidence for using high order spectral methods as a standalone performance analysis tool but, at the same time, underline the sensitivity at these flow regimes to disturbances or instabilities in the real environment when comparing to rig data.
A Design for Fouling Oriented Optimization of an HPT Nozzle
Authors: Friso R. , Casari N. , Suman A. , Pinelli M. , Montomoli Francesco 
Published: November 2019

Abstract
Fouling and erosion are two problems that severely affect gas turbines. The shape of the blade, its roughness, and its structural stability can vary as a consequence of these phenomena. The outcomes of this occurrence can span from the efficiency reduction to the engine shut down according to the nature of the material ingested, to the concentration of contaminants in the air, the cleanliness of fuel and to the particular design of the machine.
In this work, an axial turbine airfoil is modified according to the requirement of less sensibility to the phenomena above mentioned, utilizing an automatic optimization algorithm. An artificial neural network surrogate approach is used for searching the optimal shape, minimizing the computational cost of the entire process. The optimum design of the blade is therefore achieved, in order to reduce the effects of deposition on the performance.
The methodology here proposed is fully general and it is applied to an HPT nozzle in the present analysis.
An Experimental Study of Passage-to-Passage Flow Interactions in a Single Stage Axial Flow Research Turbine Rotor
Authors: Andichamy Veerandra C. , Camci Cengiz , Kim Yong W. 
Published: November 2019

Abstract
During the lifetime of a turbine stage, some of the blade tips may undergo changes due to mechanical rubbing with casing surface and also due to thermal oxidation. Understanding the effect these damaged blades have over the undamaged blades is essential to estimate the performance of the turbine stage in the operable tip clearance range. In this paper, the passage to passage aerodynamic interaction in a turbine stage is studied by modifying the tip gap of selected turbine blades and analyzing their effect on the neighboring blade passage flows. The experiments in this study are carried out in a single-stage low-speed axial turbine facility. All measurements are taken in the stationary frame of reference using a time-accurate differential dynamic pressure transducer mounted in a Kiel probe head. The experimental results from this study show that even with a significant increase on a selected blade’s tip clearance, its effect on the AFTRF turbine flow is only confined to its neighboring blade passage. The disturbances due to the altered tip clearance of one passage are not measurably propagated to its neighboring turbine passages. The changes made in one of the blades in a turbine stage do not significantly alter the aerodynamic performance of other blades. This result is particularly important for large-scale turbine research rigs such as AFTRF where the unsteady total pressure field is mapped in a time-efficient and phase-locked manner.