bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Parameterisation Setup on the Constrained Adjoint Optimisation of Transonic Fan Blades
Authors: John Alistair , Qin Ning , Shahpar Shahrokh 
Published: January 2021

Abstract
The power of adjoint optimisation is that the computational cost of the optimisation is almost independent of the number of design parameters. Thus, hundreds or even thousands of parameters can be used with relatively little increase in cost. But how much benefit does this provide, and is it always beneficial to increase the number of parameters? This work investigates the benefit achieved during the optimisation of transonic fan and compressor blades using various resolutions and layouts of Free Form Deformation grid. A method to constrain thickness throughout the blade span (to maintain mechanical integrity) during the optimisation is implemented and the effect of constraining thickness on the resulting blade designs demonstrated. It is shown that increasing the number of parameters generally leads to improved optimised designs, but that increasing the number of free-form parameters in the axial and circumferential directions is more beneficial than increasing the number of radial control parameters.
Prediction of the Acoustic Reflection in a Realistic Aeroengine Intake With Three Numerical Methods to Analyze Fan Flutter
Authors: Bontemps Thomas , Aubert Stéphane , de Pret Maxime 
Published: January 2021

Abstract
For a particular range of frequencies, an acoustic coupling between the fan and the air intake can modify fan stability regarding flutter. Previous works have shown that characterizing the reflection on the intake opening might be a crucial element to target operating points for which the risk of acoustic driven flutter is high. To do so, three methodologies are compared in this paper: an aeroelastic CFD simulation, an acoustic potential simulation and an analytical model. Each of them has a different fidelity level and computational cost, what makes their usage more beneficial at some step in the design process. It is shown that results of aeroelastic CFD and acoustic potential simulations are in excellent agreement. Fast acoustic simulations are then a good option in the early design process. The analytical model presents an important error mainly on the phase, and should be adapted before usage.
Aero Engine Concepts Beyond 2030: Part 1 — The Steam Injecting and Recovering Aero Engine
Authors: Schmitz Oliver , Klingels Hermann , Kufner Petra 
Published: January 2021

Abstract
Recognizing the attention currently devoted to the environmental impact of aviation, this three-part publication series introduces two new aircraft propulsion concepts for the timeframe beyond 2030. This first part focuses on the steam injecting and recovering aero engine concept. In the second part, the free-piston Composite cycle engine concept is presented. A third publication, building upon those two concepts, presents the project which aims for demonstrating the proof of concept with numerical simulation and test-bench experiments up to a technology readiness level of three.
In the steam injecting and recovering aero engine concept, exhaust heat generated steam is injected into the combustion chamber. The humidified mass flow contains significantly more extractable energy than air. Furthermore, the pumping of liquid water up to the necessary pressure requires a magnitude less power than the compression of air, which reduces the internal power demand. Both lead to a noticeable increase in specific power compared to a conventional gas turbine and, foremost, to a significant increase in thermodynamic efficiency. By use of a condenser, installed behind the steam generator, the water is recovered from the exhaust gas-steam mixture.
The proposed concept is expected to reduce fuel burn and CO2 emissions by about 15 % and NOx formation can be almost completely avoided compared to state-of-the-art engines of the same technology level. Moreover, the described concept has the potential to drastically reduce or even avoid the formation of condensation trails. Thus, the steam injecting and recovering aero engine concept operated with sustainable aviation fuels offers the potential for climate-neutral aviation.
Based on consistent thermodynamic descriptions, preliminary designs and initial performance studies, the potentials of the concepts are analyzed. Complementarily, a detailed discussion on concrete engineering solutions considers the implementation into aircraft. Finally, the impact on emissions is outlined.
Parallel Harmonic Balance Method for Analysis of Nonlinear Dynamical Systems
Authors: Blahoš J. , Vizzaccaro A. , Salles L. , El Haddad F. 
Published: January 2021

Abstract
Controlling vibration in jet engine remains one of the biggest challenges in aircraft engine design and conception. Methods dealing with vibration modelling usually rely on reduced order modelling techniques. This paper aims to provide a high fidelity method to solve vibration problems. It presents a parallel harmonic balance method applied to a full size problem. In order to be computationally efficient, a parallel harmonic balance method is used for the first time in solid mechanics. First, the parallel implementation of harmonic balance method is described in detail. The algorithm is designed to minimize communication between cores. Then, the software is tested for both beam and blade geometries. Finally, a scalability study shows promising acceleration when increasing the number of cores.
CFD Modelling Strategies for the Simulation of Roughness Effects on Friction and Heat Transfer in Additive Manufactured Components
Authors: Mazzei Lorenzo , Da Soghe Riccardo , Bianchini Cosimo 
Published: January 2021

Abstract
It is well-known from the literature that surface roughness affects significantly friction and heat transfer. This is even more evident for additive manufactured (AM) components, which are taking an increasingly important role in the gas turbine field. However, the exploitation of numerical approaches to improve their design is hindered by the lack of dedicated correlations and CFD model developed for such high roughness conditions.
Usually the additive manufactured components are simulated considering the surfaces as smooth or applying an equivalent sand-grain roughness (ks) that results in a velocity shift in the boundary layer. However, determining a priori the most appropriate value of ks is challenging, as dozens of correlations are available, returning scattered and uncertain results.
The aim of this work is to benchmark some existing modelling strategies (among which the equivalent sand grain roughness) and test a numerical approach capable of narrowing the existing gap between simulated and tested thermal performance of additive manufactured devices. The technology enabler is represented by higher-fidelity CFD simulations accounting for the impact of real surface roughness on pressure drop and heat transfer.
At this purpose, an existing literature model for rough walls has been implemented in ANSYS Fluent and tested on a variety of AM mini-channels so as to determine the best-fitting values of ks and corrected wetted surface ratio Scorr that match the experimental data in terms of friction factor and Nusselt number. Knowing also the measured roughness descriptors of each component, it has been possible to derive valuable guidelines for an effective exploitation of CFD on additive manufactured components, thus allowing a more accurate estimation of the thermal performance in additive manufactured components.
Aeromechanical Characterization of a Last Stage Steam Blade at Low Load Operation: Part 2 — Computational Modelling and Comparison
Authors: Pinelli Lorenzo , Vanti Federico , Peruzzi Lorenzo , Arnone Andrea , Bessone Andrea , Bettini Claudio , Guida Roberto , Marré Brunenghi Michela , Slama Vaclav 
Published: January 2021

Abstract
This paper is part of a two-part publication that aims to experimentally and numerically evaluate the aerodynamic and mechanical damping of a last stage ST blade at low load operation. A three-stage downscaled steam turbine with a snubbered last stage moving blade LSMB has been tested in the T10MW test facility of Doosan Skoda Power R&D Department in the context of the FLEXTURBINE European project (Flexible Fossil Power Plants for the Future Energy Market through new and advanced Turbine Technologies).
Aerodynamic and flutter simulations of different low load conditions have been performed. The acquired data are used to validate the unsteady CFD approach for the prediction of the aerodynamic damping in terms of logarithmic decrement. Numerical results have been achieved through an upgraded version of the URANS CFD solver, selecting appropriate and robust numerical setups for the simulation of very low load conditions, such as increased condenser pressure at the exhaust hood outlet.
The numerical methods for blade aerodamping estimation are based on the computation of the unsteady pressure response caused by the row vibration. They are usually classified in time-linearized, harmonic balance and non-linear approaches both in frequency and time domain. The validation of all these methods historically started in the field of aeronautical low-pressure turbines and has been gradually extended to compressor blades and steam turbine rows.
For the analysis of a steam turbine last rotor blade operating at strong part load conditions, non-linear methods are recommended as these approaches are able to deal with strong nonlinear phenomena such as shock waves and massive flow separations inside the domain.
Experimental data have been used to separate the contributions of mechanical and aerodynamic damping, extrapolating to zero mass flow the total measured damping.
Finally, the comparisons between the aerodynamic damping coming from measurements and CFD results have been reported in order to highlight the capability to properly predict the last stage blade flutter stability at low load conditions. Such comparisons confirms the flutter free design of the new snubbered LSMB blade.
Part 1: A Swirl Vane Generation Code for Fuel Spray Nozzles
Authors: Andreou Thomas , White Craig , Kontis Konstantinos , Shahpar Shahrokh , Brown Nicholas 
Published: January 2021

Abstract
Achieving an optimal level of flow swirl is required for efficient mixing of air and fuel in order to realise lean combustion. A novel method is devised to achieve a necessary level of swirl, using NACA airfoil profiles as the baseline for swirl stator blades. Formulas for achieving a required level of swirl have been derived and implemented in a computer program that generates aerodynamic vanes which meet the specified swirl. The usability of the program over a broad range of Reynolds numbers is verified. A curve fitting method has been developed, taking into account the trailing edge angles and blade solidity, in order to speed up the iterative process. A significant computational speed-up is achieved from this approach, and an excellent initial preliminary vane design can be obtained, which can later be introduced inside an automated optimisation process.
Numerical Modelling of NOx Emissions and Flame Stabilization Mechanisms in Gas Turbine Burners Operating With Hydrogen and Hydrogen-Methane Blends
Authors: Meloni Roberto , Cerutti Matteo , Zucca Alessandro , Mazzoni Maurizio 
Published: January 2021

Abstract
Main objective of this paper is to assess the capability of numerical models in predicting NOx emissions and flame stabilization mechanisms of a heavy-duty gas turbine burner when operated with hydrogen and hydrogen-methane blends.
Effort focused on the selection of the proper input to pre-tabulated Flamelet Generation Manifold combustion model. A dedicated sensitivity to laminar flame speed formulation has been performed as well, since it primarily affects flame stabilization through the closure term of the progress variable transport equation.
Available NOx emissions data from full scale annular combustor rig test with hydrogen-air mixtures are presented first in this paper: test results have been used to validate the numerical setup for the reference geometry. Then, the model has been used to predict NOx emissions of alternative geometries in case of pure hydrogen, allowing screening of viable options to reduce the scope of a dedicated test campaign.
Concerning flame stabilization mechanisms, simulations have been carried out for a reference geometry first: data from dedicated tests have been used to specialize the tool. Results of modified geometries are shown, to explore the effect of different fuel injection patterns or internal channel modifications.
Based on the analysis outcomes, a discussion is provided regarding advantages and drawbacks of each proposed solution, as well as the ability of modelling setup in catching varied flame stabilization mechanisms.
Design and Performance of a Boundary Layer Ingesting Fan
Authors: Mårtensson Hans , Laban Martin 
Published: January 2021

Abstract
A Boundary Layer Ingesting fan is designed to function in a tail cone thruster configuration on an existing aircraft. This means that the fan ingests part of the boundary layer developing over the fuselage all around the circumference. While the fuselage drag induced on the ingested flow makes it possible to obtain a higher propulsive efficiency, it also means that the fan will operate in a severely distorted flow. In the configuration studied here the incoming flow will generally have a lower impulse near the hub, but also substantial non-axisymmetric components. The incoming flow profile is evaluated from a CFD model of a complete Fokker 100 aircraft modified with a tail cone thruster installed. Having the aircraft modeled in detail allows the extraction of the flow entering the fan inlet, which makes up the inlet boundary condition to design for. In order to make a rational design of the fan, the incoming flow is circumferentially averaged at each radial location to form the radial profile used in the design. A fan map is created to evaluate critical points in the operating envelope in order to demonstrate that the given design is stable in operation. Operation of the fan in static ground conditions is within the operating envelope of the fan without variable nozzle area.
Influence Mechanisms of Manufacture Variations on Supersonic/Transonic Blade Aerodynamic Performances
Authors: Liu Baojie , Liu Jiaxin , Yu Xianjun , Meng Dejun , Shi Wenbin 
Published: January 2021

Abstract
The results of previous studies have proved that manufacture variations can cause a noticeable influence on compressor aerodynamic performance. The main objective of this paper is to investigate the influence rules and mechanisms of manufacture variations on supersonic/transonic blades aerodynamic performance. The variations used in this study were measured from some newly manufactured high-pressure compressors.
In the present study, several blade sections with different design Mach number conditions are selected for further statistical analysis of measured deviation data. Therefore, some systematic errors in the deviation data have been revealed. Based on these data, the computational fluid dynamics (CFD) method has been used to obtain the aerodynamic performances of a large number of the measured blade elements. And then, the analysis of the influence rules of manufacture variations on blade aerodynamic performance in different Mach number conditions has been carried out. The present results indicate that the effects of manufacture variations on blade aerodynamic performance in the lower Mach number (0.8) condition are much more significant comparing to that in the higher Mach number (0.9∼1.2) conditions. Based on this, influence mechanisms of manufacture variations on positive incidence range and negative incidence range have been analyzed. The differences of influence mechanisms in different Mach number conditions are the focus of research.
Model-Based Thermodynamic Analysis of a Hydrogen-Fired Gas Turbine With External Exhaust Gas Recirculation
Authors: Bexten Thomas , Jörg Sophia , Petersen Nils , Wirsum Manfred , Liu Pei , Li Zheng 
Published: January 2021

Abstract
Climate science shows that the limitation of global warming requires a rapid transition towards net-zero emissions of green house gases (GHG) on a global scale. Expanding renewable power generation in a significant way is seen as an imperative measure within this transition. To compensate for the inherent volatility of wind- and solar-based power generation, flexible and dispatchable power generation technologies such as gas turbines are required. If operated with CO2-neutral fuels such as hydrogen or in combination with carbon capture plants, a GHG-neutral gas turbine operation could be achieved. An effective leverage to enhance carbon capture efficiency and a possible measure to safely burn hydrogen in gas turbines is the partial external recirculation of exhaust gas. By means of a model-based analysis of an industrial gas turbine, the present study initially assesses the thermodynamic impact caused by a fuel switch from natural gas to hydrogen. Although positive trends such as increasing net electrical power output and thermal efficiency can be observed, the overall effect on the gas turbine process is only minor. In a following step, the partial external recirculation of exhaust gas is evaluated and compared both for the combustion of natural gas and hydrogen, regardless of potential combustor design challenges. The influence of altering working fluid properties throughout the whole gas turbine process is thermodynamically evaluated for ambient temperature recirculation and recirculation at an elevated temperature. A reduction in thermal efficiency can be observed as well as non-negligible changes of relevant process variables. These changes are are more distinctive at a higher recirculation temperature.
Squeeze Film Damper Bearing With Double-Ended Beam Springs: Part II — Experimental Validation
Authors: Li Wei , Braman Christopher , Hantz Brian , Thorat Manish , Pettinato Brian 
Published: January 2021

Abstract
To validate a new squeeze film damper (SFD) bearing design introduced in [1], a pair of 3.5 inch SFD bearings were manufactured and tested. Static spring compression test was conducted to prove the spring design stiffness calculated through the geometry parametric spring model. High cycle loading fatigue testing of the spring was conducted to validate the design spring fatigue limit. The entire SFD bearing assembly was inspected and checked through a SFD centering bench test before the rotor dynamic test.
Unbalance response correlation and logarithmic decrement (Log. Dec.) measurement using the operational modal analysis (OMA) method were employed for the rotor-dynamic tests. An agreement was seen between the analysis and the experimental measurement. It was seen that the SFD bearing provided the extra damping as expected to suppress the unbalance vibration when passing through the critical speed and also improve the stability (Log. Dec.) of the rotor. It was found that the measured SFD damping was closer to the full film damping model when the squeeze oil film was sealed with O-rings. The SFD improved the logarithmic decrement of the rotor-bearing system from 0.07 to more than 0.21 as compared to the system without SFD.
Study of Buoyancy Effects on Supercritical CO2 Heat Transfer in Circular Pipes
Authors: Khadse Akshay , Vesely Ladislav , Sherwood James , Curbelo Andres , Goyal Vipul , Raju Nandhini , Kapat Jayanta S. , Kim Wanjae 
Published: January 2021

Abstract
Supercritical CO2 (sCO2) can be utilized as a working fluid in various systems including high scale power cycle, portable power production unit, centralized cooling system and standalone cooling device. Lack of accurate predication tools such as heat transfer coefficient correlations and insufficient knowledge behind fundamental heat transfer processes can hinder its practical realization in key energy and cooling systems. The overall objective of the proposed study is to extend fundamental knowledge about heat transfer and fluid flow processes in conduits pertinent to sCO2 power cycle with an emphasis on buoyancy effects. Operational requirement of high pressures and temperatures for intended applications put a significant amount of constraints on measurement strategy and instrumentation. For this paper, experiments were conducted with uniform volumetric heat generation within pipe wall, for a single Reynolds number of 16,600 at test section inlet. The designed test apparatus and data reduction process are validated with high pressure air experiments, complemented by companion computations. Nusselt number was found to be within 10% of conventional correlations.
For the test parameters and pipe size selected, factors of 2 to 4 variations in circumferential Nusselt number distributions are observed in sCO2 flow. Richardson number and other similar parameters to indicate importance of buoyancy-driven flow phenomena suggest that buoyancy forces caused by large density variation of sCO2 in flow cross-sections may cause the observed circumferential variations in Nusselt number.
Aero-Thermal Optimization of Bladeless Turbines
Authors: Braun James , Paniagua Guillermo , Falempin Francois 
Published: January 2021

Abstract
The harnessing of mechanical power from supersonic flows is constrained by physical limitations and substantial aerodynamic losses. Bladeless axial turbines are a viable alternative to extract power in such harsh conditions without restricting the operating conditions. In this paper, we present a shape optimization of the wavy surface of bladeless turbines to maximize the power extraction, while minimizing convective heat fluxes and pressure losses. First, a baseline geometry was defined and an experimental campaign was carried out on the baseline wavy surface of the bladeless turbine at supersonic conditions in the Purdue Experimental Aerothermal Lab. Pressure, heat flux and skin friction measurements were compared with the Reynolds Averaged Navier Stokes results. Afterwards, the evaluation routine which consisted of the blade generation, grid generation, solving, and post-processing was implemented within an evolutionary optimizer with a multi-objective function to maximize the pressure force and minimize heat flux and pressure loss. Finally, a three-dimensional assessment in terms of power, heat load and pressure drop was performed for the best performing geometry with the commercial solver CFD++ of Metacomp. Turbulence closure was provided with the k-omega-SST turbulence model. The annular chamber of the bladeless turbine consisted of an unstructured mesh of approx. 8–10 million grid points.