bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Impact of Inlet Flow Angle on Turbine Vane Frame Aerodynamic Performance
Authors: Pramstrahler Simon , Peters Andreas , García De Albéniz Mikel Lucas , Leitl Peter Adrian , Heitmeir Franz , Marn Andreas 
Published: October 2022

Abstract
Modern aero-engines are designed for high efficiency and low weight to reduce fuel consumption and achieve reductions in CO2 emissions. According to the goals and roadmap of the “Flightpath 2050” report, the Strategic Research and Innovation Agenda (SRIA) demands a drastic reduction of emissions to balance further air traffic growth. Therefore, technologies and processes allowing for a 75 % reduction in CO2 emissions per passenger kilometer compared to the year 2000 technology standard must be available by 2050. Turbine Vane Frames (TVF) are one technology to increase the efficiency of aero-engines and can therefore help to reach this goal. Turbine Vane Frames are located in-between the high-pressure turbine (HPT) and the low-pressure turbine (LPT) of an aero-engine and have three major purposes: guiding the flow to higher radii, incorporating the function of stator guide vanes of the first stage of the LPT, and passing structural components and oil pipes through the flow channel. A TVF with aft-loaded wide-chord main vanes and splitter vanes was designed, which meets engine-representative mechanical and aerodynamic constraints. A test vehicle consisting of the TVF and a first-stage LPT rotor has been designed and is currently being tested in the subsonic test turbine facility for aerodynamic, aeroacoustic and aeroelastic investigations (STTF-AAAI) at the Graz University of Technology. In the engine, the TVF needs to function at high performance not only at the aerodynamic design point (cruise) but also at off-design conditions. A splittered TVF design features complex flow fields with strong secondary flow interactions, and because of the fundamental design differences, the flow field characteristics within a TVF are different from those in a conventional LPT vane row. This paper discusses the flow field in a splittered TVF with emphasis on secondary flow structures and their interaction with each other and the main flow. To examine the influence of different swirl angle levels on the flow field and loss generation mechanisms inside the TVF, the swirl angle upstream of the TVF is numerically changed in a wide range from positive to negative angles. The objective of this study is to examine the sensitivity of the splitter vanes to large flow angle deviations, as present in part-load operation. Additionally, the flow field downstream of the TVF and its influence on the LPT rotor performance is described in detail. The size and locations of separated flow regions resulting from the off-design incidence of the flow and their impact on the rotor are investigated and quantified. A loss breakdown is presented to discuss the impact of incidence variations on the performance of both the TVF and the LPT.
Influence of RANS Turbulent Inlet Set-Up on the Swirled Hot Streak Redistribution in a Simplified Nozzle Guide Vane Passage: Comparisons With Large-Eddy Simulations
Authors: Wingel Christopher , Binder Nicolas , Bousquet Yannick , Boussuge Jean-François , Buffaz Nicolas , Le Guyader Sébastien 
Published: October 2022

Abstract
A high-pressure turbine is a complex component of a gas turbine from a thermo-mechanical point of view. In modern lean-burn combustion chambers, this complexity is enhanced with the presence of hot streaks together with swirl components and high levels of turbulence coming from the combustion chamber. These radial and azimuthal velocities and temperature distortions have a substantial impact either on the aerodynamics inside the high-pressure turbine or on the aero-thermal behavior of the vanes and blades. It is thus clear that the early development of a high-pressure turbine using numerical simulations must take into account swirled hot streaks.
From a practical point of view, imposing the proper turbulence at the inlet boundary condition is not easy in classical Reynolds-Averaged Navier-Stokes (RANS) methods, where all the turbulence is modeled. This paper studies the redistribution of a swirled hot streak in the simplified case of a bent duct. This work focuses on turbulence modeling. High-fidelity Large-Eddy Simulation (LES) results are used as reference data to validate different RANS set-ups to predict the hot streak redistribution in terms of migration and diffusion.
Results show that imposing the turbulent quantities from a LES causes an immediate destruction of the swirl components and a too-high total temperature diffusion in a RANS approach. It is found that the turbulent length scale, expressed in terms of μT/μ, plays a significant role in the aerodynamic and aero-thermal behavior of the flow. The optimal range for the value of μT/μ differs from what is encountered in the literature on a high-pressure turbine configuration. Also, imposing quantities at the inlet consistent with the LES or measurements does not improve the prediction of the trajectory of the swirl jet or the total temperature distribution. The anisotropy of turbulence is suspected to explain the failure of the usual RANS models.
Pressure Losses Analysis in Two High-Pressure Steam Turbine Control Valves Situated in One Valve Chamber
Authors: Slama Vaclav , Rudas Bartolomej , Simurda David , Hala Jindrich , Luxa Martin 
Published: October 2022

Abstract
Steam turbines belong to the most important systems in power conversion. In order to control their power output at steady state base load or part load conditions, the use of control valves is a widely used method. The flow in a pair of high-pressure steam turbine control valves which are situated in one valve chamber is analyzed in this paper from the pressure losses point of view. The experiments were carried out on a valve model installed in a wind tunnel for high speeds in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences. The flow at different valve cone lifts in both control valves was investigated and results were generalized in the form of so-called valve characteristics. Investigations were carried out on the model with control valve strainers and without them. In order to further understand the reasons of detected pressure loss differences, the numerical simulations were carried out in the Doosan Skoda Power Company using ANSYS software tools. The comparison of results shows which cases of the valve setup are preferable with regard to pressure losses and thus efficiency. Furthermore, an existing pressure loss prediction model for valve pressure loss estimation for each investigated case was updated. This model helps to better design the valve geometry in order to increase overall turbine efficiency.
Assessment of the Impeller/Volute Relationship of Centrifugal Fans From an Aerodynamic and Aeroacoustic Perspective
Authors: Biedermann Till M. , Moutamassik Youssef , Kameier Frank 
Published: October 2022

Abstract
Heavy-duty centrifugal fans require high reliability and first-class performance. Besides, extreme conditions and harsh environments are often encountered, such as in the papermaking process, in steel or cement plants or the chemical and petrochemical industry. Therefore, the design of high performance heavy-duty industrial fans requires robust yet efficient solutions. Previous work indicates a high aerodynamic and aeroacoustic sensitivity concerning the specific position of the volute cut-off (tongue). This effect will be further investigated, not by directly changing the orientation of the cutoff, but by varying the position of the impeller relative to a fixed volute casing. The initial evaluation is done through a numerical study of three influencing parameters, which allows the aerodynamic dependencies to be modelled using low-layer artificial networks. Subsequently, extensive experimental studies were carried out to validate the aerodynamic dependencies and also to incorporate information on the aeroacoustic performance. The obtained results show that the operating point represents the key factor in determining the optimal positioning, with qualitatively comparable dependencies found for both tested fans. From an aeroacoustic point of view, the determined optimal configuration does not necessarily coincide with the observed aerodynamic desires, so careful analysis and a reasonable compromise are required, motivating for a multi-objective optimisation process.
A Comprehensive Analytical Model for Vortex Shedding From Low-Speed Axial Fan Blades
Authors: Daku Gábor , Vad János 
Published: October 2022

Abstract
The paper presents a comprehensive analytical model for the characterization of von Karman vortex shedding in the wake of models of low-speed axial fan blades. The elaborated minimal model is based on the Reynolds-averaged Navier-Stokes and continuity equations. For validation purposes, hot-wire measurements have been carried out in a wind tunnel on representative blade profiles. The measurement data obtained for various streamwise positions downstream of the blade trailing edge, i.e. transversal profiles of mean velocity as well as root-mean-square of fluctuating velocity, are evaluated. As the experimental validation demonstrates, the minimal model fairly localizes the transversal position of the vortex centres, and represents the motion of the vortices along the wake. The validated minimal model serves with the following benefits. a) An extensive understanding of the underlying physics related to the flow field featuring vortex shedding in the near-wake region. Easy-to-use quantitative correlation among the characteristics of wake flow affected by the shed vortices. b) Extension of the literature-based methodology for determination of the transversal distance between the shed vortex rows, being used as scaling parameter for the Strouhal number utilized in calculation of vortex shedding frequency. c) Modelling the behavior of rows of shed vortices farther away from the trailing edge. Such behavior may influence the acoustic signature of VS, and, as such, it is to be considered in fan noise modelling.
Effect of Twist Angle on the Performance of Darrieus Vertical Axis Wind Turbines
Authors: Saad Ahmed S. , Ahmed Mahmoud 
Published: October 2022

Abstract
Conventional straight-bladed Darrieus wind turbines have some drawbacks including large oscillations of coefficient of torque with negative values within a wide range of angle of rotation which decrease the self-starting abilities of the turbine and increase the mechanical vibrations. To solve these weaknesses, the current study proposes twisted-bladed Darrieus turbine instead of the conventional straight-bladed design to flatten the oscillations of torque coefficient in addition to enhancing the self-starting abilities of the Darrieus turbine. The studied angles of twisting are 45, 90, and 135 degrees in addition to the traditional untwisted Darrieus rotor. The trends of coefficient of power against ratio of rotor tip speed in addition to coefficients of dynamic and static torque over a complete cycle (360 degrees) are estimated for all studied twisted-bladed Darrieus turbines. Thus, three dimensional incompressible unsteady Reynolds-Average Navier-Stokes equations in conjunction with the k-ω shear-stress transport turbulence model is developed and numerically simulated utilizing ANSYS Fluent. The developed numerical model is validated using the available measurements from literature. The predicted characteristics of flow field around the proposed twisted-bladed Darrieus turbines are presented and compared with the traditional untwisted design.
Accordingly, results revealed a significant improvement of the coefficient of power is attained by increasing the angle of twisting from 0° to 90°. However, with an additional increase in the angle of twisting beyond 90°, the coefficient of power declined. The turbine with an angle of twisting of 90° attains the largest coefficient of power of 0.318 with a percentage increase of 13.2 % in comparison with the traditional straight-bladed Darrieus turbine which has a peak coefficient of power of 0.281. The traditional untwisted turbine has negative values of coefficient of static torque within a large range of angle of rotation. However, the proposed turbines with twisted blades exhibit lower torque fluctuations and positive static torque values at all angles of rotation resulting in enhancing the self-starting abilities of the Darrieus turbine.
Parameter Optimization of Combustor Dump Diffuser Based on RSM
Authors: Yan Yue , Suo Jianqin , Wu Yanhui 
Published: October 2022

Abstract
At present, dump diffuser is basically adopted in the combustion chamber of aeroengine. The total pressure loss in it may account for 30% or even higher in the combustion chamber. So it is necessary to optimize various geometric parameters in dump diffuser. In order to solve the problem of increasing experimental cost due to multi-parameter optimization, response surface method (RSM) was used to study the performance of dump diffuser’s three geometric parameters at three inlet Mach numbers (Ma = 0.27, 0.20 and 0.10), namely pre-diffuser expansion angle, dump gap ratio and side wall expansion angle. The ratio of static pressure recovery coefficient to total pressure loss coefficient was used to compare the performance of the diffuser. Also the distribution of entropy production rate was used to obtain the pressure loss in the diffuser and analyze the causes. Then the response model was established and the response equation was solved to obtain the combined parameters corresponding to the optimal solution. Finally, the optimization results were predicted and verified. We can see that the influence of three geometric parameters on the diffuser performance is the prediffuser expansion angle, dump gap ratio and the side wall expansion angle in descending order. Compared with the initial average performance, the optimized results under three working conditions are improved by 47.93%, 48.70% and 69.49%, and the relative errors are all less than 6.5%, showing high accuracy.
Investigation of Physics-Informed Neural Networks Based Solution Techniques for Internal Flows
Authors: Post Pascal , Winhart Benjamin , di Mare Francesca 
Published: October 2022

Abstract
In this work, we explore for the first time the possibility and potentials of employing the emerging PINNs approach in internal flow configurations, solving the steady state Euler equations in two dimensions for forward and inverse problems. In addition to a simple bump test case, the PINNs results of a highly loaded transonic linear turbine guide vane cascade are presented. For forward problems, we investigate different formulations of the transport equations and boundary conditions. Overall, PINNs approximate the solution with acceptable accuracy; however, conventional CFD methods are far superior in forward settings. Finally, we demonstrate the capabilities and the tremendous potentials of PINNs regarding hidden fluid mechanics in two distinct inverse settings, intractable for conventional CFD methods. Firstly, we infer complete flow fields based on partial, possible noisy, solution data, e.g., partial surface pressure and velocity field data; even approximating the exit condition of the cascade using only the measured blade pressure distribution is possible. Secondly, we also infer an unknown parameter of the governing equations.
A Computational Investigation of Wall-Film Formation by an Impinging Liquid Jet in Crossflow
Authors: Magnotti Gina M. , Sforzo Brandon A. , Powell Christopher F. 
Published: October 2022

Abstract
Accurate fuel injection modeling remains of critical importance to the simulation of gas turbine engines as the predicted spray structure dictates fuel-air mixing, combustion, and emissions in the combustor. The prefilming airblast atomizer relies on the formation of a thin conical sheet of fuel, which breaks up due to its interaction with the counter-swirling airstreams. Recent x-ray imaging performed at Argonne National Laboratory’s Advanced Photon Source of a prefilming airblast atomizer revealed the formation of a frothy film, which is comprised of both liquid and bubbles. This finding challenges the inherent assumption for existing spray models, which assume that the film is only comprised of liquid fuel, and motivates the detailed investigation of the film formation process. To investigate the physics governing the impingement of a liquid jet in crossflow on a plate, a computational study was carried out. Large Eddy Simulations (LES) coupled with an algebraic volume-of-fluid (VOF) approach were performed to model a liquid water jet interacting with a subsonic crossflow and subsequently impinging on an aluminum plate. For the condition studied, a grid convergence study revealed that a minimum cell size of 25 μm was sufficient to adequately resolve the jet-wall interaction and film formation process, with good agreement with the x-ray measurements. These simulations also predicted the formation of bubbles within the film due to the entrainment of air. The influence of adhesion on the film characteristics and bubble distribution was explored using two different contact angles representing water on polished and unpolished aluminum plates. Although an increase in contact angle was not observed to affect the average film thickness, the lower interfacial tension reduced the number of bubbles that were formed, but increased the average size.
Numerical Investigation of Particle Deposition in Double Wall Effusion Cooled Systems
Authors: Villain Florian Y. A. , Vadgama Nikul , Gaskell Jack G. , Ireland Peter T. , McGilvray Matthew , Gillespie David R. H. 
Published: October 2022

Abstract
In the pursuit of ever-higher thermal efficiency, aero-engines have seen their turbine entry temperatures rise steadily, driving the need for highly effective cooling systems. Double-walled, effusion-cooled turbine blades, which combine arrays of impingement holes and pedestals, with full-coverage external film cooling offer the potential for significantly better cooling than conventional multi-pass blade cooling systems. However, this technology includes intricate geometric features with high curvature which are susceptible to blockage from dust and sand. Such deposition has the potential to compromise the flow and cooling performance.
In this paper, the vulnerability of two generic double-walled cooling schemes, incorporating diamond pedestals, is predicted using Arizona Road Dust as test contaminant and nickel superalloy as substrate. Conducting simulations in commercial CFD software, a bespoke Continuous Random Walk (CRW) turbulent tracking model predicts the arrival of particles at the blade surface. It is combined with a Discrete Element Methods (DEM) based bounce stick model, to predict particle sticking and rebound.
Bulk and spatially resolved deposition statistics are reported for each of the cooling system components. The results are used to investigate the susceptibility of the system to particle blockage and to develop a reduced-order model able to predict deposition fractions based on a newly formulated generalised Stokes number.
Analyses of Damping Sustainability of Additively Manufactured Nickel Alloy Components Subjected to High Strain Loading Cycles
Authors: Hollkamp John P. , Scott-Emuakpor Onome , Celli Dino 
Published: October 2022

Abstract
While integrally bladed rotors in turbine engines have multiple benefits, they are more susceptible to vibration and as a result, high cycle fatigue failure. In response, damping treatments such as viscoelastic layers, hard coatings, and particle dampers have been utilized to reduce vibration of integrally bladed rotors and promote longer service life. In recent experiments, nickel-based alloy 718 structural beams representative of turbine blades were manufactured via laser powder bed fusion (LPBF) with internal geometries containing unfused powder. Compared to fully fused beams, these beams with internal particle dampers have demonstrated a significant improvement in damping performance, suppressing vibrations by as much as 95%. However, the inherent damping of the particle dampers decreases as the strain amplitude increases when some of the unfused powder fuses to the walls of the pockets. This study investigates the effect of the location of the particle dampers within the beam on the sustainability of its damping performance. To compare the effect of the particle damper’s location, the LPBF nickel-based alloy 718 beams are subjected to successive resonance dwells with increasing strain amplitude. After each dwell, the damping performance is assessed via the half-power bandwidth method of the frequency response function. Results from this study indicate that while the location of the particle dampers within the specimen does influence when the damping begins to degrade, it is not the optimal parameter for damping sustainability. The aim of this and future work is to improve the long-term damping performance and viability of the internal particle damper so that it can be more effectively utilized to extend the lifetime of turbomachinery components.
Application of a Distributed Element Roughness Model to Additively Manufactured Internal Cooling Channels
Authors: Altland Samuel , Yang Xiang , Thole Karen , Kunz Robert , McClain Stephen 
Published: October 2022

Abstract
Design for cooling effectiveness in internal flow systems relies on accurate models for dynamic losses and heat transfer. In these systems (e.g., gas turbine blades, intercoolers, heat exchangers), thousands of individual passages of varying configuration and roughness morphology can be present. In recent years, additive manufacturing (AM) has further expanded the design space, but can give rise to large-scale roughness features, whose sizes are comparable to the channel height. The range of roughness length scales in these systems makes CFD of the resolved rough surfaces impractical at a design level. Alternately, volumetric roughness modeling approaches, such as distributed element roughness models (DERM) can be leveraged, as they have computational costs orders of magnitude lower.
In this work, a DERM model based on the Double Averaged Navier-Stokes (DANS) equations is presented and applied to additively manufactured rough channels, representative of gas turbine blade cooling passages. Unique to this formulation of DERM is the specific treatment of the DERM drag coefficient and the spatially averaged Reynolds stresses. This generalized formulation of the drag coefficient allows for improved model accuracy across a wider array of potential roughness fields, without having to rely on calibration for each morphology. A novel two-layer approach to modeling the spatially averaged Reynolds stress is also proposed.
Three different AM rough surfaces documented by McClain et al. [1] were configured opposite smooth walls as well as each other to create a total of six channel configurations. Across the six cases, th roughness trough to peak size ranges from 0.15δ to 0.66δ, where δ is the channel half-width, and the roughness Reynolds number ranges from Rek = 60 to Rek = 300.
DERM predictions for spatially and temporally averaged mean flow quantities are compared to previously reported DNS results. Specifically, we observe good agreement in the mean velocity profiles, stress balances and drag partitions across the case matrix.
While DERM models are typically calibrated to specific deterministic roughness shape families at comparatively small roughness Reynolds numbers, these results demonstrate a wider range of applicability for the present, more generalized formulation. It is demonstrated that the proposed model can accommodate random roughness of large scale, typical of AM.