bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Bayesian Approach for the Identification of Cascade Loss Model Strategy
Authors: Simoni Daniele , Lengani Davide , Petronio Daniele , Bertini Francesco 
Published: January 2021

Abstract
A Bayesian method has been used to identify the best model strategy to describe the profile losses of low pressure turbine (LPT) cascades operating under unsteady inflow. The model has been tuned with experimental data measured in a large scale cascade facility, equipped with a moving bar system. Tests have been carried out on two different cascades, investigating three different reduced frequencies, three mass flow coefficients and several Reynolds numbers (up to eight) per condition, accounting for an overall amount of 51 different combinations of these parameters for each cascade. The predictor functions included into the model have been varied starting from a classic polynomial formulation for each influencing parameter, and then with functional relationships mimicking physical constrains and loss tendencies.
Different combinations of the predictors, also including different types and orders of the cross-terms, have been evaluated by means of a Bayesian model selection method searching for the maximum probability of the model in fitting the cloud of experimental data. In particular, the evaluation of the Model Evidence (ME) using the Bayesian Information Criterion approximation (BIC) has allowed obtaining sufficient accuracy and avoiding overfitting at the same time.
The best model here identified will be shown to be able to well reproduce the loss surface of a third different cascade that does not participate to the model selection. Realistic profile loss evolutions outside of the design space tested are provided, thus also allowing for a generalization of the structure of the model for other applications and future works.
Compressed Air Energy Storage for a Small Size Standalone Plant Powered by a Solar Power Unit and a Gas Turbine
Authors: Arnulfi Gianmario L. , Croce Giulio 
Published: January 2021

Abstract
Energy storage can balance heat and power demand and production over different time scales, with both technical and economic benefit. Several devices have been proposed, but only two are really utilized: hydro-pumped storage, for large size plants, and electrochemical battery energy storage, for medium and small plants. Compressed Air Energy Storage (CAES) was proposed as an alternative, and two well-known plants, Hunthorf (Germany) and Mac Intosh (United States) have been successfully working for many years. However, due to the huge capital costs, this concept never became widely popular. Here, a bit different approach is proposed: one or more reciprocating compressors and pressurized reservoirs can supply an additional amount of air to a gas turbine. During the “charging” phase, the reciprocating compressors pump air into the reservoirs; during the “discharging” phase, the turbo-expander is fed by both the turbo-compressor and the reservoirs in parallel. The turbo-compressor is partially relieved and fuel can be saved for the same power. This paper focuses on a standalone small size user, served by a solar power unit coupled with a micro gas turbine. The aim is to lay down rules for a proper storage managing.
Template-Based Hexahedral Mesh Generation for Turbine Cooling Geometries
Authors: Hao Muting , Wang Feng , Hope-Collins Joshua , Rife Max E. , di Mare Luca 
Published: January 2021

Abstract
This paper describes a multiblock grid generation method for turbine cooling geometries. The method is based on the observation that cooling films are essentially branches inserted on a large trunk, represented by the passage or by the cooling duct. The small size of the films compared to the overall size of turbine blades allows simplifications to be introduced with respect to general-purpose trunk and branch algorithms. The grid generation starts from an existing layout for the passage or cooling duct grid and operates on a Cartesian patch of the trunk surface. The patch is hollowed and a templated branch layout is inserted. Padding blocks are created to connect the two layouts into a single, boundary conforming layout. The resulting multiblock grid is then smoothed using a modification of Thompson’s Poisson system. The boundary mesh distribution is not prescribed. Instead, boundary orthogonality is enforced and elliptic smoothing is performed on the boundaries as well as inside the volume. The grid size control relies on a novel Newton-like update for the control functions of the Poisson system. The smoothing step is essential in achieving good grid quality throughout and determines, in part, the template for a given configuration. The algorithm is particularly suitable for large arrays of films or other cooling decoration and results show that the proposed method can produce grids of better quality than existing methods.
Meanline Calculation of Surge Margin Loss due to Inlet Flow Distortion
Authors: Menegozzo Luca , Benini Ernesto 
Published: January 2021

Abstract
In the present work, a methodology for the preliminary analysis of axial compressors operating under clean and distorted inflow conditions is discussed. A 1D mean-line solver has been developed, and the validation has been carried out under clean conditions considering the datasets of the subsonic Rolls-Royce HP9, as well as the transonic NASA Rotor 37 and NASA Rotor 67. Numerical results have been reported together with experimental data in terms of performance maps and spanwise distributions. The ARP1420 procedure and the parallel compressor theory have been implemented for the impact assessment of inlet flow distortion on the compressor surge line. A full-annulus CFD simulation of the NASA Rotor 37 has been carried out, in order to generate high-fidelity benchmark results. A 180° circumferential distortion has been considered as inlet boundary condition, and the surge line has been calculated using the two numerical models.
Parameter Extension Simulation of Turbulent Flows in a Compressor Cascade With a High Reynolds Number
Authors: Jin Yan 
Published: January 2021

Abstract
The turbulent flow in a compressor cascade is calculated by using a new simulation method, i.e., parameter extension simulation (PES). It is defined as the calculation of a turbulent flow with the help of a reference solution. A special large-eddy simulation (LES) method is developed to calculate the reference solution for PES. Then, the reference solution is extended to approximate the exact solution for the Navier-Stokes equations. The Richardson extrapolation is used to estimate the model error. The compressor cascade is made of NACA0065-009 airfoils. The Reynolds number 3.82 × 105 and the attack angles −2° to 7° are accounted for in the study. The effects of the end-walls, attack angle, and tripping bands on the flow are analyzed. The PES results are compared with the experimental data as well as the LES results using the Smagorinsky, k-equation and WALE subgrid models. The numerical results show that the PES requires a lower mesh resolution than the other LES methods. The details of the flow field including the laminar-turbulence transition can be directly captured from the PES results without introducing any additional model. These characteristics make the PES a potential method for simulating flows in turbomachinery with high Reynolds numbers.
Prediction of Ventilation Effectiveness for LM9000 Package With Machine Learning
Authors: Corsini Alessandro , Delibra Giovanni , Giovannelli Marco , Lucherini Gabriele , Minotti Stefano , Rossin Stefano , Tieghi Lorenzo 
Published: January 2021

Abstract
Gas turbines usually are installed inside an enclosure, which is used as protection from the external environment and to provide an acoustic insulation. A ventilation system is required to control the temperature inside the enclosed volume and to dilute any potential gas leakage that may come from faulty pipes or flanges. The system has to be properly designed to avoid any unexpected explosion which would generate an overpressure not contained by enclosure walls. The most common approach to predict the effectiveness of the ventilation system requires to perform CFD analyses, which are very expensive in computational terms. A new approach has been proposed by authors, using machine learning and artificial neural networks (ANN) to identify the poorly ventilated zones. This methodology has been further developed, optimized and applied to a real gas turbine packages of new generation. In the present paper the authors will show the application of this procedure to the LM9000 package and the comparison with the results predicted using conventional CFD techniques. The tangible improvement introduced by this methodology is that the computational time is reduced from about three weeks with the common CFD approach to few minutes. The artificial neural network is developed in a Python environment that is applied during the CFX post-process phase of a steady state CFD simulation, providing results equivalent to unsteady CFD simulation. Besides the immediate benefits of this particular application, the suggested approach looks to be a great candidate to substitute the conventional and time-consuming CFD simulations with a fast post-processing algorithm that is able to learn and self-optimize as long as it is used.
Effect of Friction on the Structural Dynamics of Built-Up Structures: An Experimental Study
Authors: Fantetti Alfredo , Schwingshackl Christoph 
Published: January 2021

Abstract
Frictional contacts are a major source of uncertainty in the correct prediction of the dynamic response of built-up structures. This uncertainty is partially due to a limited understanding of the effects of friction on dynamic responses. Vice versa, dynamic responses can also affect the frictional behaviour of the interfaces in contact.
In the present study, the mutual relationships between frictional behaviour and structural dynamics are investigated by means of a high frequency friction rig. The rig is characterised by a simple and localised frictional contact that is needed to accurately measure hysteresis loops. Of course, the rig also has its own dynamic response, and consequently represents an excellent test case to gain a better understanding of the correlation between hysteresis loop shapes and their effect upon the dynamics.
Impact hammer tests and shaker tests were performed on the friction rig, and lead to changes in the damping and stiffness of its dynamic response, which were linked to variations in the frictional behaviour of the contact. Furthermore, there was some indication as to how certain resonances of the system might strongly affect the frictional behaviour. In particular, it was observed that full sliding causes excitation of structural modes that in turn lead to distortions in the measured hysteresis loops.
These findings confirm the strong relationship between friction and dynamics, thus highlighting the necessity to include a detailed frictional description of contacting interfaces for more accurate modelling of the dynamics of built-up structures.
Multi-Criteria Selection of Wind Turbine Using TOPSIS Approach
Authors: Rehman Shafiqur , Khan Salman A. , Alhems Luai M. 
Published: January 2021

Abstract
The recent revolution in the use of renewable energy worldwide has opened many dimensions of research and development for sustainable energy. In this context, the use of wind energy has received notable attention. One critical decision in the development of a wind farm is the selection of the most appropriate turbine compatible with the characteristics of the geographical location under consideration in order to harness maximum energy. This selection process considers multiple decision criteria which are often in conflict with each other, as improving one criterion negatively affects one or more other criteria. Therefore, it is desired to find a tradeoff solution where all selection criteria are simultaneously optimized to the best possible level. This paper proposes a TOPSIS (The Technique for Order of Preference by Similarity to Ideal Solution) based approach for multi-criteria selection of wind turbine. Three decision criteria, namely, hub height, wind speed, and net capacity factor are used in the decision process. A case study is shown on real data collected from the Aljouf region located at an altitude of 753 meters above sea level in the northern part of Saudi Arabia. Seventeen turbines with rated capacities ranging from 1.5 GW to 3 GW from various manufacturers are evaluated. Results indicate that Vestas V110 turned out to be the most appropriate turbine for the underlying site.
Identification of Losses in Turbomachinery With Machine Learning
Authors: Angelini Gino , Corsini Alessandro , Delibra Giovanni , Giovannelli Marco 
Published: January 2021

Abstract
One of the issues of handling large CFD datasets and process them to derive important design correlations is the limitation in automating the post-processing of data. Machine learning techniques, developed to process large unlabelled dataset, can play a key role on this subject.
In this work an unsupervised approach to isolate different flow features inside a 2D cascade is proposed and validated. The approach relies on machine learning methods and in particular on Exploratory Data Analysis (EDA) and Principal Component Analysis for the pre-processing of the data and on K-means clustering for the post-processing.
The K-means algorithm was trained on a Design of Experiments (DoE) of over 140 cases of 2D linear cascade configurations to identify the boundary layer on the profiles and the wake downstream. Validation resulted in a perfect capability of identifying the regions of interest.
Then a possible exploitation of this method is presented, to compute pressure losses downstream of the cascade and train an artificial neural network to make a regression able to extend data to all the possible combinations of geometrical and operating parameters of the cascade.
The same algorithm was applied to 3D flow cascades of profiles with sinusoidal leading edges to stress its extrapolation capability in case of flow regimes not present in the training DoE.
Heat Transfer Performance of Internal Cooling Turbine Blades Using Cutted-Root Rib Design
Authors: Dinh Cong-Truong , Vu Tai-Duy , Dinh Tan-Hung , Nguyen Phi-Minh 
Published: January 2021

Abstract
In gas turbines, the turbine blades are always working in the highly temperature overhead the permissible metal temperatures. To safe operation, the turbine blades are needed to cool. Many researchs in turbine cooling technology can be categorized as internal and external cooling. This paper presents an investigation of cutted-root rib design, where a part of rib was truncated below to create an extra-passage in the root rib applied in the internal cooling turbine blades of jet engine using three-dimensional Reynolds-averaged Navier-Stokes with the SST model. The object of this investigation is to reduce the vortex occurring near the rib for improving the performance of heat transfer, such as the Nusselt number and thermal performance factor. To investigate the heat transfer performance and fluid flow characteristics of internal cooling turbine blades, a parametric study of the cutted-root rib was performed using various geometric parameters related to the height and shapes of the extra-passage. The cutted-root rib geometry is designed in ANSYS DesignModeler, and then meshed by using ICEM-CFD, analysed and post-processed using Ansys-CFX. The numerical results showed that all heat transfer parameter with the cutted-root rib design was greater than the original case without cutted-root rib.
Root Cause Analysis of Torsional and Lateral Vibrations on a Compressor Test Rig
Authors: Rouwenhorst Driek , Jäger Daniel , Schmieder Marcel , Hermann Jakob 
Published: January 2021

Abstract
In this case study an extensive root cause analysis was performed on a compressor test rig following the observation of unexpected high amplitude vibrations during the rig commissioning. Typically, the location and the frequency of an observed vibration is not enough to pinpoint the cause of the behavior in a system with multiple components. The test rig comprising of an electric motor, gearbox and compressor rotor may be subject to rotordynamics, torsional dynamics, mechanical eigenfrequencies and fluid dynamics in the compressor.
In order to understand the source of the vibrations observed at the gearbox, lateral vibrations of the casing and torsional vibrations of the rotor were measured simultaneously. In parallel, the system was modeled in MADYN 2000 in order to match the observations with theoretical torsional eigenmodes of the drivetrain.
The modeling of the system resulted in a torsional eigenfrequency lying within 10% of the observed gearbox vibration, making it a viable candidate to excite gearbox vibrations through a varying torque. To be able to measure this mode shape, a temporal measurement setup for torsional vibrations had to be installed.
The measurements of the test campaign revealed that a torsional resonance is indeed present at the frequency of the observed vibrations. However, a lack of coherence between the torsional and lateral vibrations suggests that the torsional resonance is not the root cause of the gearbox vibrations. Two separate resonances were observed as the gear mesh frequency crossed the torsional eigenfrequency and the observed high amplitude gearbox vibration. Evidence of a structural eigenfrequency of the gearbox was found through an impact test. Although the torsional resonance is ruled out as the root cause, it is presumed that the two resonances do experience a positive coupling, causing the particularly high gearbox vibrations.
Synergistic Technology Combinations for Future Commercial Aircraft Using Liquid Hydrogen
Authors: Rompokos Pavlos , Rolt Andrew , Nalianda Devaiah , Isikveren Askin T. , Senné Capucine , Grönstedt Tomas , Abedi Hamidreza 
Published: January 2021

Abstract
Liquid hydrogen (LH2) has long been seen as a technically feasible fuel for a fully sustainable greener aviation future. The low density of the cryogenic fuel would dictate the redesign of commercial aircraft to accommodate the large tanks, which are unlikely to be integrated within the whole internal volume of the wing.
In the ENABLEH2 project, the morphological aspects of a LH2 aircraft design are discussed and a methodology for rapid concept comparative assessment is proposed. An exercise is then carried on to down-select short-to-medium range (SMR) and long-range (LR) concepts, able to carry 200 passengers for 3000 nmi and 414 passengers for 7500 nmi respectively.
The down-selection process was split into two phases with the first considering 31 potential airframe architectures and 21 propulsion-system arrangements. The second phase made the final down-selections from a short-list of nine integrated design concepts that were ranked according to 34 criteria, relating to operating cost, revenue, noise and safety. Upon completion of the process, a tube and wing design with the tanks integrated into extended wing roots, and a blended-wing-body design were selected as the best candidates for the SMR and LR applications respectively. Both concepts feature distributed propulsion to maximise synergies from integrating the airframe and propulsion systems.
Experimental Analysis of Surge-Detection System Based on Pressure Derivatives at Part-Speed Operation
Authors: Liskiewicz Grzegorz , Kabalyk Kirill , Jaeschke Andrzej , Grapow Filip , Kulak Michał , Kryłłowicz Władysław , Ouyang Hua , Shen Xin 
Published: January 2021

Abstract
This paper presents tests of an anti-surge system based on pressure derivatives. The control algorithm was proven to work on different machines and with different unstable flow phenomena.
Compressors are known to be affected by unstable flow conditions appearing at low mass flow rate conditions. The best known and most dangerous phenomenon is surge, which is a global instability affecting the entire impeller and regions upstream and downstream from it. A list of identified local phenomena includes among others: impeller rotating stall, diffuser rotating stall and inlet recirculation. All have a specific pressure signature that is used for early identification.
The method presented in this paper is based on a control parameter named the Rate of Derivative Fluctuation (RDF). This approach involves a simple measure of flow instability that is universal and reacts to flow disturbances. RDF has been already confirmed to identify inlet recirculation and surge. The aim of this study is to conduct real-time tests of an anti-surge system implementing the RDF algorithm triggering the safety valve opening. The study confirmed the optimal position of the monitoring point. The results showed that the RDF is indeed sensitive to different types of flow instabilities appearing in different impellers, and that it provides efficient flow stability monitoring.
Acoustic Resonance in an Axial Multistage Compressor Leading to Non-Synchronous Blade Vibration
Authors: Fiquet Anne-Lise , Vercoutter Agathe , Buffaz Nicolas , Aubert Stéphane , Brandstetter Christoph 
Published: January 2021

Abstract
Significant non-synchronous blade vibrations (NSV) have been observed in an experimental three-stage high-speed compressor at part-speed conditions. High amplitude acoustic modes, propagating around the circumference and originating in the highly loaded Stage-3 have been observed in coherence with the structural vibration mode.
In order to understand the occurring phenomena, a detailed numerical study has been carried out to reproduce the mechanism. Unsteady full annulus RANS simulations of the whole setup have been performed using the solver elsA. The results revealed the development of propagating acoustic modes which are partially trapped in the annulus and are in resonance with an aerodynamic disturbance in Rotor-3. The aerodynamic disturbance is identified as an unsteady separation of the blade boundary layer in Rotor-3. The results indicate that the frequency and phase of the separation adapt to match those of the acoustic wave, and are therefore governed by acoustic propagation conditions.
Furthermore, the simulations clearly show the modulation of the propagating wave with the rotor blades, leading to a change of circumferential wave numbers while passing the blade row. To analyze if the effect is self-induced by the blade vibration, a noncoherent structural mode has been imposed in the simulations. Even at high vibration amplitude the formerly observed acoustic mode did not change its circumferential wave number.
This phenomenon is highly relevant to modern compressor designs, since the appearance of the axially propagating acoustic waves can excite blade vibrations if they coincide with a structural eigenmode, as observed in the presented experiments.