bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of the Convergent-Divergent Nozzles Arrangement Parameters on Aerodynamic Losses and Overall Supersonic Turbine Performance
Authors: Moroz Leonid , Burlaka Maksym , Yudin Aleksandr 
Published: October 2022

Abstract
Single-stage axial pressure compound and two-row velocity compound supersonic turbines have a very high specific work, which allows for high power levels at high-pressure ratios and small flow rates in a very compact dimensional envelope. The latter is extremely desirable in certain types of Liquid Rocket Engine (LRE) turbopumps. Besides, due to their compactness, mechanical simplicity, and low cost, such turbines are favorable in high-pressure ratio Organic Rankine Cycles (ORC), gas expanders in chemical and technological processes, various mechanical drive applications, etc. However, despite their mechanical simplicity, the supersonic aerodynamic effects in such turbines are very complex. There are a number of design and analysis methodologies for such turbines, which are currently used in the industry. Nevertheless, some important nozzles arrangement parameters are still insufficiently investigated. It is known that there is an influence of the principle of drilled nozzles arrangement in a cascade and (round cross-section) convergent-divergent nozzles overlapping on overall turbine efficiency. Though, the data were either not formalized in some sort of loss model or formalized in a simplified formula that does not take into account meridional nozzle angle and the diameter where the nozzles are arranged (turbine mean diameter). The paper describes the study of the qualitative and quantitative influence of the mentioned above parameters on aerodynamic losses in drilled convergent-divergent nozzles and overall supersonic turbine performance. Supersonic aerodynamic effects and their influence on turbine performance were determined by employing the state-of-the-art commercial CFD code. Respective mesh sensitivity studies and domains architectures selection considerations are presented. The formalization of the studied nozzle parameters is discussed. The methods used for the determination of the parameters dependencies minimizing the number of CFD calculations are explained. The figures with visualizations of the critical results and numerical values are provided. The obtained loss models are described. The obtained loss models were incorporated into a turbine design and analysis program and then compared with experimental data. The utilization of the improved loss model provides the opportunity to design high-efficient supersonic turbines with conical drilled nozzles and satisfy specific design constraints with the use of nozzle arrangement parameters.
An Improved Preliminary Design Tool for Turbomachinery Blades Using Van der Pol Based Reduced-Order Model for Non-Synchronous Vibrations
Authors: Hollenbach Richard , Kielb Robert , Hall Kenneth 
Published: October 2022

Abstract
Starting from an oscillating cylinder, this paper navigates the shift of a Van der Pol based Reduced-Order Model from that simple case to airfoil and turbomachinery blade. The structure will be free to vibrate under the influence of a von Karman vortex street. The first degree of freedom tracks the oscillatory motion of the vortex shedding utilizing a combined Van der Pol and a Duffing equation, previously shown to better match the flow physics. The other degree of freedom is a cylinder or pitching blade with stiffness, mass, and damping, making the coupled system one of fluid-structure interaction. A third degree of freedom is added in a separate configuration to provide the airfoil with both pitching and plunging motion. Using this model to study the time-history of the fluid and the structure oscillation, additional parameters are extracted to understand the underlying mechanisms of frequency lock-in and limit cycle oscillation. The coefficients in the model are tuned to match limit cycle oscillation data captured in experiments. Then, the phase shift between the vortex shedding and the structural motion is calculated when the former locks-on to the latter, and then unlocks. Also, the work done per cycle of vibration is analyzed from the contributions of the mass, spring, and damping forces to determine the dominant contributor when locking-in versus unlocking. This model is a more accurate case for turbomachinery applications compared to the previous models. This model, especially with the third degree of freedom, will serve as the preliminary design tool for engine manufacturers to use for preventing Non-Synchronous Vibrations in turbomachinery.
Design Optimization of Blade Tip in Subsonic and Transonic Turbine Stages - Part II: Flow Physics and Augmented Aerothermal Integral Objective Function
Authors: Duan Penghao , He Li 
Published: October 2022

Abstract
In Part I, a companion paper of the two-part article, two turbine stages working with the same Reynolds number (8.8 × 105), flow coefficient, loading coefficient and reaction, but the different exit Mach number (Mexit = 0.7 and Mexit = 1.1, respectively) are designed and optimized to provide a direct contrast between the high subsonic and the transonic turbine tip. In Part II, further analysis are carried out primarily aimed at addressing the issues of interest arising from Part I:
a) to understand the driving flow physics for the observed contrasting aerodynamic efficiency sensitivities of the two stages with respect to squealer height.
b) to seek a more suitable heat transfer objective function for the tip aero-thermal design optimization, given the seemingly strong conflicts among the heat transfer objective functions.
The advanced post-processing techniques are adopted to identify and quantify vortical structures in the rotor tip region. Two vortices, the Pressure Side Vortex (PSV) and the Casing-driven Cavity Vortex (CCV), are found to have major influence on the flow pattern within the squealer tip.
On the aerodynamic side, the transonic squealer is shown to be somewhat less effective than the subsonic one (Part I). The OTL mass flow rate in the transonic stage is less sensitive to the squealer height. The corresponding reduced blockage for the transonic squealer may be attributed to two factors: 1) the vena-contracta formed by the PSV as it leaves the squealer cavity induces smaller size of separation in the supersonic flow. Thus, the blockage effect and the mass flux deficit are reduced in the transonic stage; and 2) the choking of the OTL at the rear portion of the transonic tip acts as a limiter for the leakage mass flow. On the heat transfer side, the two vortices also have major signatures on the cavity surfaces, mainly by impingement. For the PSV, the impingement impact is mainly on the cavity floor. For the CCV on the other hand, its impact is mainly on the inner side wall of the suction side rim. The overall linear variations of the heat load with the squealer height primarily correspond to the linear increase of the cavity side wall surface. The vortical structure is found to be influential: the higher slope of increments in the transonic stage is due to the stronger and more persistent CCV with a clear signature on the large portion of the suction side cavity wall at a large squealer height.
In addressing issue b), the coolability weighted non-uniformity parameter is proposed to integrate the local heat transfer and the coolability. The proposed coolability augmented objective function is shown to provide more consistent Pareto fronts for heat transfer non-uniformity, than those adopted in Part I. It thus should serve well as an enabler to help practical applications of blade tip aerothermal design optimizations.
A Numerical Investigation of Sweeping Air/Mist Jet Film Cooling Through a Passive Fluidic Oscillator, Part I: Steady vs. Sweeping Air-Only Jets
Authors: Abdelmaksoud Ramy , Wang Ting 
Published: October 2022

Abstract
The sweeping jet can be a promising candidate in film cooling applications since it has a large lateral jet spreading which can be considered an advantage when compared to the regular steady jet film cooling. Fluidic oscillators can generate a sweeping jet without the need for any moving parts. In addition, they can be more conveniently manufactured by additive manufacturing techniques. This two-part paper presents a numerical study to investigate the application of using air/mist sweeping jets in film cooling for protecting turbine airfoils. Part I focuses on validating the computational mode by comparing the thermal-flow and heat transfer behavior between steady and sweeping air-only jets to ensure they are consistent with published information. Part II focuses on the mist behavior and its effect on heat transfer enhancement in the sweeping jet film cooling by adding micro-liquid droplets. An unsteady Reynolds Averaged Navier-Stokes (URANS) simulation accompanied by the k-ω SST turbulence model was used in this study. A comparison is made between steady and sweeping jets at two blowing ratios (BR = 1 and 2). The results show that the steady jet provided better film cooling performance along the centerline compared to that of the sweeping jet for both blowing ratios. However, the sweeping jet provided better and more uniform film cooling performance in the spanwise direction. Both jets experienced a significant jet-liftoff when the blowing ratio was 2. The entrainment was significant in the sweeping jet case for both blowing ratios. The sweeping jet caused an increase of 9.5% in total pressure losses compared to the steady jet. It was found that, for the sweeping jet, a pair of counter-rotating vortices is inward-rushing toward the wall in the center rather than outward-rushing as in a typical steady jet film cooling flow field. A detailed analysis is presented to understand the instantaneous vortex dynamics of the sweeping jet that leads to the inward rotating CRVP. The result shows that the pair of counter-rotating vortices is just a time-averaged image of a single vortex sweeping back and forth in the domain; it does not actually exist in real time.
Life Cycle Assessment of Innovative Concentrated Solar Power Plants Using Supercritical Carbon Dioxide Mixtures
Authors: Liao X. , Chalumeau S. , Crespi F. , Prieto C. , Lopez-Roman A. , Rodriguez de Arriba P. , Martínez N. , Sánchez D. , Paggini A. , David P. L. 
Published: October 2022

Abstract
The SCARABEUS project, funded by the European Commission, is currently investigating the potential gains brought about by the utilization of carbon dioxide mixtures in supercritical power cycles of Concentrated Solar Power plants, in lieu of the common Rankine cycles based on steam turbines or even pure carbon dioxide cycles. The analysis has already confirmed that it is possible to attain thermal efficiencies higher than 51% when ambient temperatures exceed 40°C, which is unheard of when conventional technology or standard CO2 technology is used. Additionally, this extraordinary performance is achieved with simpler cycle layouts, therefore with lower capital costs. The additives considered include organic and inorganic compounds which are added to the raw carbon dioxide in a variable proportion, depending on the composition of the additive and on ambient temperature. Regardless, it is important to assess whether or not there is an additional environmental advantage in terms of carbon dioxide and other potential hazards brought about by the new chemicals in the system. This is presented in this paper where the results obtained so far by the consortium for the carbon footprint from a Life Cycle perspective are discussed. Along with the assumptions and methodology, the results are compared for three reference plants: state-of-the-art CSP plant based on steam turbines, innovative CSP plant using pure supercritical CO2 technology, and the SCARABEUS concept using supercritical CO2 mixtures. The results are promising as they suggest that it is possible to reduce the carbon footprint of a 110 MWe CSP plant to be significantly less than 27kgCO2/MWh from the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC AR5).
Compressor Maps and Coupling: Symmetry, Geometry, and Universality
Authors: Iwrey Benjamin , Johnson Paul K. 
Published: October 2022

Abstract
The predecessor of this paper (GT2021-60012) introduced the Symmetry (S’-) framework of compressor map representation. This framework exhibits a natural simplicity of expression in comparison with the common BETA framework, enables relatively simple coupling of an arbitrary number of maps in series, and posits a novel instability mechanism termed “snap equilibrium.” A one-dimensional numerical simulation is constructed to simulate snap equilibrium and its associated hysteresis, exactly as predicted in the S’-framework by inspecting the maps at their interface. Both two-map and three-map snap equilibria are simulated, the latter demonstrating that snap equilibrium may be triggered between two maps by the presence of a third.
The geometrical structure of the S’-framework is then explored in depth. Any given constant-geometry map can be expressed completely as either of two related vector fields — inlet-exit and input-output — in the corrected speed-corrected flow abstract space. The geometry of these vector fields is examined, and the nature of speedlines themselves is reinterpreted. The possibility of breaking a given map into its constituent maps is explored. Finally, a set of features common to all constant-geometry maps is identified in corrected speed-corrected flow space, and their implications are discussed.
New Concept for Design in Turbomachinery Applications using Full RANS Gradient Methodology
Authors: Del Rio Armando , Casartelli Ernesto , Fleischli Benno , Mangani Luca 
Published: October 2022

Abstract
Centrifugal compressors are mainly designed with the best efficiency point in mind and the focus oriented towards the impeller. The vaned diffuser geometry is usually developed using simple shapes, such as prismatic blades or wedges, which are unable to account for the flow distortion at the impeller outlet. Investigations of diffuser modifications using CFD during the design phase can help to extend the operating range. In order to assess the effect of such modifications, simulations in off-design conditions need to be performed. Accurate predictions of local flow structures at such conditions require a robust flow solver with mixing-plane interfaces and advanced turbulence modelling capabilities. In recent years diffuser modifications were performed mainly based on manual trial-and-error approaches and show considerable potential for improvements. To accelerate the process and allow automation, which is crucial in industrial applications, it is suggested to use an adjoint-based optimization algorithm for diffuser shape design. In this work a discrete adjoint solver implemented into a robust pressure-based CFD framework was used. While many optimization studies follow the frozen-turbulence approach, which essentially ignores the dependency of the sensitivity on the turbulence quantities, the present adjoint solver fully includes such effects. Automatic differentiation even allows for flexibility with respect to the choice of turbulence model: Any model available in the primal solver can also be used in the adjoint solver. In this particular case the k-ε EWT model was used, since it shows good convergence behavior and is capable of predicting the machine characteristic even at off-design conditions. Mesh morphing was realized via the Free Form Deformation method, which provides stable mesh deformation and offers a simple and fast set-up procedure. Several optimizations were conducted for the RWTH Aachen “Radiver” centrifugal compressor case with vaned diffuser. It was shown that an optimization strategy using a multi-operating-point approach, considering part- and overload conditions, is capable of improving the peak efficiency as well as the overall shape of the machine characteristic.
Investigation of Impeller Backface Cavity Flowfield Using CFD and a One-Dimensional Flow Solver
Authors: Erdem E. , Sertcakan M. C. , Sal S. , Dogu Y. , Yalcinkaya A. 
Published: October 2022

Abstract
This article aims at the investigation of impeller backface cavity flowfield using Computational Fluid Dynamics (CFD) and one-dimensional flow solver for a representative backface cavity. For initial validation the test rig data from Hart and Turner [5 and 6] is employed at various leakage flows and inlet swirl ratios. For impeller backface cavity in consideration, rather than covering a wide range of impeller leakage flows, which is irrelevant for engine operations, different rotational speeds representing different phases of engine running conditions are varied. The cavity flowfield is composed of two flows entering the cavity, impeller leakage and Compressor Discharge Pressure (CDP) seal leakage flows. The flowfield displays the dominant character of torques induced by the stator and the rotor for the majority of the cavity, towards the lower radii radially inward flow starts to gain swirl and when CDP seal leakage flow mixes with this flow, swirl ratios reach nearly unity. A fraction of mixture flow leaves the cavity thru the outlet and remaining circulates at bottom left corner and gets pumped up by the backface surface.
Design Sensitivity of a 1-1/2 Stage Unshrouded High Work Turbine Using Very-Large Eddy Simulations
Authors: Gonzalez-Martino Ignacio 
Published: October 2022

Abstract
A numerical study has been conducted to assess the performance sensitivity of a 1-1/2 stage turbine to variations in design or operating conditions. The impact of the rotor tip gap, blade and vane fillets, and upstream boundary layer turbulence are assessed with respect to a baseline model and a comprehensive set of experimental data. Global stage performance, radial distribution of relevant quantities such as pressure and turning angles, as well as unsteady pressure distributions in the planes between rows were available as reference data.
Very-large eddy simulations using time-marching Lattice-Boltzmann methods are performed here to analyze in detail the compressible and highly turbulent flow features. In the present work, the complete 1-1/2 stage turbine with time-accurate moving rotor geometry has been simulated. This means that no blade reduction technique or almost-periodic flow hypothesis have been used in the simulation. This will help in providing a better understanding of the complex mechanisms occurring in the turbine channel, for the different numerical models. Moreover, thorough comparisons to experimental data will help in validating the numerical approach for future similar turbomachinery cases.
About the bosonic decays of heavy Higgs states in the (N)MSSM
Authors: Domingo Florian , Paßehr Sebastian 
Published: October 2022

AbstractThe heavy, doublet-dominated Higgs bosons expected in Two-Higgs-Doublet-Model-like extensions of the Standard Model are obvious targets for searches at high-energy colliders, and considerable activity in this sense is currently employed in analyzing the results of the Large Hadron Collider. For sufficiently heavy states, the $$SU(2)_\textrm{L}$$

S
U

(
2
)

L

symmetry drastically constrains the decays of these new scalars. In models that contain only additional Higgs doublets, fermionic decay channels are expected to dominate, although some bosonic modes may lead to cleaner signals. The situation is very different if the Higgs sector is further extended by singlet states and the singlet-dominated scalars are kinematically accessible, in which case the Higgs-to-Higgs widths may even become dominant. Yet, a quantitative interpretation of the experimental data in terms of a specific model also runs through the control of radiative corrections in this model. In this paper, we examine the bosonic decays of the heavy, doublet-dominated Higgs states in the MSSM and the NMSSM at full one-loop order, insisting on the impact of the $$SU(2)_\textrm{L}$$

S
U

(
2
)

L

symmetry and the effects of infrared type, in particular, the emergence of sizable non-resonant contributions to the three-boson final states.
Coincident gauge for static spherical field configurations in symmetric teleparallel gravity
Authors: Bahamonde Sebastián , Järv Laur 
Published: October 2022

AbstractIn symmetric teleparallel gravities, where the independent connection is characterized by nonmetricity while curvature and torsion are zero, it is possible to find a coordinate system whereby the connection vanishes globally and covariant derivatives reduce to partial derivatives – the coincident gauge. In this paper we derive general transformation rules into the coincident gauge for spacetime configurations where the both the metric and connection are static and spherically symmetric, and write out the respective form of the coincident gauge metrics. Taking different options in fixing the freedom in the connection allowed by the symmetry and the field equations, the Schwarzschild metric in the coincident gauge can take for instance the Cartesian, Kerr–Schild, and diagonal (isotropic-like) forms, while the BBMB black hole metric in symmetric teleparallel scalar–tensor theory a certain diagonal form fits the coincident gauge requirements but the Cartesian and Kerr–Schild forms do not. Different connections imply different value for the boundary term which could in principle be physically relevant, but simple arguments about the coincident gauge do not seem to be sufficient to fix the connection uniquely. As a byproduct of the investigation we also point out that only a particular subset of static spherically symmetric connections has vanishing nonmetricity in the Minkowski limit.
Observational constraints on the fractal cosmology
Authors: Asghari Mahnaz , Sheykhi Ahmad 
Published: October 2022

AbstractIn this paper, we explore a fractal model of the universe proposed by Calcagni (J High Energy Phys 03:120, 2010) for a power-counting renormalizable field theory living in a fractal spacetime. Considering a timelike fractal profile, we derived field equations in fractal cosmology, in order to explore the structure formation and the expansion history in fractal universe. Numerical investigations based on matter power spectra diagrams report higher structure growth in fractal cosmology, being in contrast to local galaxy surveys. Additionally, according to the evolution of Hubble parameter diagrams, it can be understood that Hubble constant would decrease in fractal cosmology, which is also incompatible with low redshift estimations of $$H_0$$

H
0

. So, concerning primary numerical studies, it seems that fractal cosmology is not capable to alleviate the tensions between local and global observational probes. Then, in pursuance of more accurate results, we constrain the fractal cosmology by observational data, including Planck cosmic microwave background (CMB), weak lensing, supernovae, baryon acoustic oscillations (BAO), and redshift-space distortions (RSD) data. The derived constraints on fractal dimension $$\beta $$
β
indicate that there is no considerable deviation from standard model of cosmology.
Aristotle’s Metaphysics Z as First Philosophy
Authors: Meister Samuel 
Published: October 2022

Abstract
Discussions of Aristotle’s Metaphysics Z tend to treat it either as an independent treatise on substance and essence or as preliminary to the main conclusions of the Metaphysics. I argue instead that Z is central to Aristotle’s project of first philosophy in the Metaphysics: the first philosopher seeks the first causes of being qua being, especially substances, and in Z Aristotle establishes that essences or forms are the first causes of being of perceptible substances. I also argue that the centrality of Z to first philosophy is compatible with its status as theology.