bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Purge Flow Parameters on Heat Transfer and Film Cooling in Turbine Center Frames
Authors: Jagerhofer Patrick R. , Patinios Marios , Glasenapp Tobias , Göttlich Emil , Farisco Federica 
Published: September 2021

Abstract
Due to stringent environmental legislation and increasing fuel costs, the efficiencies of modern turbofan engines have to be further improved. Commonly, this is facilitated by increasing the turbine inlet temperatures in excess of the melting point of the turbine components. This trend has reached a point where not only the high-pressure turbine has to be adequately cooled, but also components further downstream in the engine. Such a component is the turbine center frame (TCF), having a complex aerodynamic flow field that is also highly influenced by purge-mainstream interactions. The purge air, being injected through the wheelspace cavities of the upstream high-pressure turbine, bears a significant cooling potential for the TCF. Despite this, fundamental knowledge of the influencing parameters on heat transfer and film cooling in the TCF is still missing.
This paper examines the influence of purge-to-mainstream blowing ratio, purge-to-mainstream density ratio and purge flow swirl angle on the convective heat transfer coefficient and the film cooling effectiveness in the TCF. The experiments are conducted in a sector-cascade test rig specifically designed for such heat transfer studies using infrared thermography and tailor-made flexible heating foils with constant heat flux. The inlet flow is characterized by radially traversing a five-hole-probe. Three purge-to-mainstream blowing ratios and an additional no purge case are investigated. The purge flow is injected without swirl and also with engine-similar swirl angles. The purge swirl and blowing ratio significantly impact the magnitude and the spread of film cooling in the TCF. Increasing blowing ratios lead to an intensification of heat transfer. By cooling the purge flow, a moderate variation in purge-to-mainstream density ratio is investigated, and the influence is found to be negligible.
On the Shaft Speed Selection of Parallel Hybrid Aero Engines
Authors: Sielemann Michael , Gohl Jesse , Zhao Xin , Kyprianidis Konstantinos , Valente Giorgio , Sumsurooah Sharmila 
Published: September 2021

Abstract
The boosted turbo fan or parallel hybrid is a promising means to reduce fuel consumption of gas turbines on aircraft. With an electric drive on the low-pressure spool of the gas turbine, it requires a trade-off between the characteristics of the gas turbine and the electric power sub-systems. Reducing specific thrust at a given thrust requirement results in a larger fan with a lower pressure ratio. This leads to improved propulsive efficiency but at the expense of increased weight and nacelle drag. At a given design relative tip Mach number, increasing fan size and hence tip diameter means the fan shaft speed will need to be reduced. This will, according to occasionally quoted ‘rules of thumb’, make the directly coupled electrical drive more efficient but heavier. The objective of this paper is to expose some key aspects of this trade-off in terms of efficiency and weight, and relate them to these guidelines. The paper applies sophisticated methodology in both addressed domains. For the gas turbine, multi-point design is used. Here, established synthesis matching schemes focusing on gas turbine performance parameters are extended with parameters from the sizing and weight estimation such as diameters and tip speeds. For the electrical machine, fully analytical sizing capturing the impact of cooling supply is used. The paper reports estimated gas path and machine geometries. It gives an understanding of the interactions between both sub-systems and allows concluding which low pressure spool speed gives the best instantaneous performance. It largely confirms the quoted rules of thumb but exposes that the factors affecting machine efficiency are more involved than implied for an integrated design.
Stability and Unbalance Analysis of Rigid Rotors Supported by Spiral Groove Bearings: Comparison of Different Approaches
Authors: Iseli Elia , Schiffmann Jürg 
Published: September 2021

Abstract
The dynamic behavior of spiral-grooved gas bearing supported 4DoF rotors is investigated by means of linearized bearing force coefficients and full time-integrated transient analysis. The transient method consists of a state-space representation, which couples the equations of motion with the compressible thin film fluid equation. The linearized method is based on the perturbation analysis around a given eccentric shaft position ε, allowing to compute the static and linear dynamic bearing force coefficients at different excitation frequencies.
The two methods are compared for a variation of test rotors and bearing geometries in a given compressibility number interval of Λ = [0,40]. The limitations and weaknesses of the linearized model are presented. It is shown that shafts with two symmetric herringbone-groove journal bearings have their maximum stability and load capacity if the center of gravity lays in the middle of the two bearings. For symmetric rotors (la/lb = 1) the two rigid modes, cylindrical and conical, are present and are influenced by the mass and transverse moment of inertia independently. For asymmetric rotors (la/lb &lt; 1) the stability region decreases and the modes have a mixed shape. It is no longer possible to clearly distinguish between pure cylindrical and pure conical mode shapes. The two methods predict the critical mass and critical transverse moment of inertias within a difference of &lt; 7%.
A quasi-linear unbalance module for rigid gas bearing supported rotors is presented, which considers eccentricity dependent bearing force coefficients, allowing to speed up the unbalance response analysis by four orders of magnitude. The unbalance module is compared with the full transient orbital analysis, suggesting that the quasi-linear module predicts the non-linear unbalance response with &lt; 6 % deviation for amplitudes up to ε &lt; 0.5 within the complete compressibility number range.
The Effects of Forcing Direction on the Flame Transfer Function of a Lean-Burn Spray Flame
Authors: Treleaven Nicholas C. W. , Fischer André , Lahiri Claus , Staufer Max , Garmory Andrew , Page Gary J. 
Published: September 2021

Abstract
The flame transfer function (FTF) of an industrial lean-burn fuel injector has been computed using large eddy simulation (LES) and compared to experimental measurements using the multi-microphone technique and OH* measurements. The flame transfer function relates the fluctuations of heat release in the combustion chamber to fluctuations of airflow through the fuel injector and is a critical part of thermoacoustic analysis of combustion systems. The multi-microphone method derives the FTF by forcing the flame acoustically, alternating from the upstream and downstream side. Simulations emulating this methodology have been completed using compressible large eddy simulations (LES). These simulations are also used to derive an FTF by measuring the fluctuations of mass flow rate and heat release rate directly which reduces the number of simulations per frequency to one, significantly reducing the simulation cost. Simulations acoustically forced from downstream are shown to result in a lower value of the FTF gain than simulations forced from upstream with a small change in phase, this is shown to be consistent with theory. Through using a slightly different definition of the FTF, this is also shown to be consistent with measurements of the heat release rate using OH* chemiluminescence however these results are inconsistent with the multi-microphone method result. The discrepancy comes from not having an accurate measurement of the acoustic impedance at the exit plane of the injector and from certain convective phenomena that alter the downstream velocity and pressure field with respect to the purely acoustic signal. All simulations show a lower gain in the FTF than the experiments but with good reproduction of phase. Previous work suggests this error is likely due to fluctuations of the fuel spray atomisation process due to the acoustic forcing which is not modelled in this study.
Adjoint-Based Optimisation of Rocket Engine Turbine Blades
Authors: Sanghera Bhupinder Singh , Anand Nitish , Souverein Louis , Penin Loïc , Pini Matteo 
Published: September 2021

Abstract
Axial turbine stages for gas generator cycle type rocket engines typically employ highly-loaded supersonic stator vanes. Consequently, the flow pattern downstream of the vanes is characterized by shock waves which induce high-frequency excitation on the subsequent rotor. For this reason, the optimal design of the stator is crucial in the context of development of the next generation of high-performance rocket engines, where reusability is a principal design criterion. A thorough comprehension of the loss mechanisms combined with the adoption of automated optimisation techniques can therefore enable new stator designs that may provide large benefits in terms of overall turbine performance and lifespan.
The scope of this study stems from these considerations and its objective is twofold, namely i) the shape optimisation of a supersonic stator for rocket engines and ii) the investigation of the loss mechanisms in supersonic axial turbine stator vanes at on- and off-design conditions. The investigation is performed on stator vanes that are under development for the first turbine stage of a gas generator cycle type rocket engine. The stator vanes are therefore optimised in order to reduce the profile losses by exploiting a novel adjoint optimisation framework for turbomachinery implemented in the open-source code SU2. The effect on the resulting flow field and loss sources is finally investigated.
Results show that entropy based loss coefficient gains of 6% can be achieved via shape optimisation and that the fluid-dynamic performance of these vanes is less sensitive to changes in pressure ratio compared to the performance provided by the baseline configuration. Eventually, shock-waves remain the primary loss source.
Ancillary Services Potential for Flexible Combined Cycles
Authors: Vannoni Alberto , Garcia Jose Angel , Mantilla Weimar , Guedez Rafael , Sorce Alessandro 
Published: September 2021

Abstract
Combined Cycle Gas Turbines, CCGTs, are often considered as the bridging technology to a decarbonized energy system thanks to their high exploitation rate of the fuel energetic potential. At present time in most European countries, however, revenues from the electricity market on their own are insufficient to operate existing CCGTs profitably, also discouraging new investments and compromising the future of the technology. In addition to their high efficiency, CCGTs offer ancillary services in support of the operation of the grid such as spinning reserve and frequency control, thus any potential risk of plant decommissioning or reduced investments could translate into a risk for the well-functioning of the network. To ensure the reliability of the electricity system in a transition towards a higher share of renewables, the economic sustainability of CCGTs must be preserved, for which it becomes relevant to monetize properly the ancillary services provided. In this paper, an accurate statistical analysis was performed on the day-ahead, intra-day, ancillary service, and balancing markets for the whole Italian power-oriented CCGT fleet. The profitability of 45 real production units, spread among 6 market zones, was assessed on an hourly basis considering local temperature, specific plant layouts, and off-design performance. The assessment revealed that net income from the ancillary service market doubled, on average, the one from the day-ahead energy market. It was observed that to be competitive in the ancillary services market CCGTs are required to be more flexible in terms of ramp rates, minimum environmental loads, and partial load efficiencies. This paper explores how integrating a Heat Pump and a Thermal Energy Storage within a CCGT could allow improving its competitiveness in the ancillary services market, and thus its profitability, by means of implementing a model of optimal dispatch operating on the ancillary services market.
HCF Optimization of a High Speed Variable Geometry Turbine
Authors: Simpson Alister , Kim Sung in , Park Jongyoon , Kwon Seong , Yoo Sejong 
Published: September 2021

Abstract
This paper describes the structural optimization of a high speed, 35mm tip diameter radial turbine wheel in a Variable Geometry Turbine (VGT) system, subjected to the wide range of aerodynamic loads experienced during the full operating cycle. VGTs exhibit a wide range of unsteady flow features, which vary as the nozzle vanes rotate through different positions during operation, as do the magnitudes and frequencies of the resulting pressure fluctuations experienced by the downstream turbine blades. The turbine wheel typically passes through a number of blade natural frequencies over their operating cycle, and there are a number of potential conditions where these unsteady aerodynamic loads can lead to resonant blade vibration. The focus of this work is on the development of a pragmatic design approach to improve the structural characteristics of a radial turbine blade with respect to High Cycle Fatigue (HCF), informed by detailed time-accurate Computational Fluid Dynamics (CFD) prediction of the unsteady pressure loads, coupled with FE vibration analysis to quantify the resulting blade vibration magnitudes. Unsteady CFD simulations are performed to determine the time-accurate pressure loads on the blades, and the results are used as input to forced response analysis to determine the peak alternating stress amplitudes. The detailed analysis results are then used to guide a subsequent parametric study in order to investigate the influence of key geometric parameters on the structural performance of the blade, with the optimum design identified through the use of a Goodman Diagram. The results quantify the influence of both blade thickness distribution and hub fillet details on the vibration characteristics of radial turbines.
Two Phase Flow CFD Modeling of a Steam Turbine Low Pressure Section: Comparison With Data and Correlations
Authors: Maceli Nicola , Arcangeli Lorenzo , Arnone Andrea 
Published: September 2021

Abstract
Testing a sub-component or testing a scaled model are the approaches currently used to reduce the development cost of the new low-pressure (LP) section of a steam turbine. In any case, testing campaigns are run at a limited number of operating conditions. Therefore, some correlations are used to build a performance model of the LP module and expand the usage of a limited set of experimental data to cover the application range encountered in the steam turbine market. Another approach, which has become feasible during the last decade, is the usage of CFD calculations.
These two approaches include a certain amount of uncertainty in the performance of the LP section, mainly related to the losses caused by the moisture content in the flow.
In the present paper, the results of the analysis of a cutting-edge low-pressure section for small steam turbines are presented. The results are obtained by using a CFD commercial code with a set of user defined subroutines to model the effects of droplets nucleation and growth. Different operating conditions are considered, with different wetness at the exit and different pressure ratios, in order to clearly show the loss trend for different levels of exit moisture. The numerical results are compared with the experimental data, showing a significant improvement in the performance predictability for the considered case and demonstrating the benefit of using a CFD approach instead of using existing correlations.
Synchrotron X-Ray Diffraction to Quantify In-Situ Strain on Rare-Earth Doped Yttria-Stabilized Zirconia Thermal Barrier Coatings
Authors: Fouliard Quentin , Hernandez Johnathan , Ebrahimi Hossein , Vo Khanh , Ghosh Ranajay , Raghavan Seetha , Accornero Frank , McCay Mary , Park Jun-Sang , Almer Jonathan 
Published: September 2021

Abstract
The recent advancement in multifunctional thermal barrier coatings (TBCs) for temperature sensing or defect monitoring has gained interest over the past decade as they have shown great potential for optimized engine operation with higher efficiency, reduced fuel consumption and maintenance costs. Specifically, sensor coatings containing luminescent ions enable materials monitoring using integrated spectral characteristics. While facilitating sensing capabilities, luminescent rare-earth dopants ideally present minimal intrusiveness for the thermal barrier coating. However, the effects of rare-earth dopant addition on thermomechanical and thermochemical properties remain unclear. Our study intends to fill this knowledge gap by characterizing coatings’ internal thermomechnical properties under realistic gas turbine engine operating temperatures. In this work, TBC configurations including industry standard coatings and sensor coatings were compared to quantify dopant intrusiveness. The TBC configurations have been characterized using high-energy synchrotron X-ray diffraction while being heated up to gas turbine engine temperatures. The TBC samples have been subjected to a single cycle thermal load with multiple ramps and holds during XRD data collection. Depth-resolved XRD was used to obtain the 2D diffraction patterns corresponding to each depth location for the determination of strain distributions along the TBCs. Internal strains and stresses acting through the coatings were quantified mostly highlighting that there is negligible variation between the standard and novel sensor coatings. Thus, the thermal response at high temperature remains unaffected with addition of luminescent dopants. This evaluation of novel coating configurations provides valuable insight for future safe implementation of these temperature sensing coatings without performance reductions.
A Supercritical CO2 Brayton Cycle Micro Turbine for Waste Heat Conversion: Optimization Layout in Cogenerative Applications
Authors: Reale Fabrizio , Sannino Raniero , Tuccillo Raffaele 
Published: September 2021

Abstract
Waste heat recovery (WHR) can represent a good solution to increase overall performance of energy systems, even more in case of small systems. The exhaust gas at the outlet of micro gas turbines (MGTs) has still a large amount of thermal energy that can be converted into mechanical energy, because of its satisfactory temperature levels, even though the typical MGT layouts perform a recuperated cycle. In recent studies, supercritical CO2 Brayton Cycle (sCO2 GT) turbines were studied as WHR systems whose thermal source was the exhausts from gas turbines. In particular, subject of this study is the 100 kW MGT Turbec T100.
In this paper, the authors analyze innovative layouts, with comparison in terms of performance variations and cogenerative indices. The study was carried out through the adoption of a commercial software, Thermoflex, for the thermodynamic analysis of the layouts. The MGT model was validated in previous papers while the characteristic parameters of the bottoming sCO2 GT were taken from the literature. The combined cycle layouts include simple and recompression sCO2 bottoming cycles and different fuel energy sources like conventional natural gas and syngases derived by biomasses gasification. A further option of bottoming cycle was also considered, namely an organic Rankine cycle (ORC) system for the final conversion of waste heat from sCO2 cycle into additional mechanical energy. Finally, the proposed plants have been compared, and the improvement in terms of flexibility and operating range have been highlighted.
Combustor Development and Engine Demonstration of Micro-Mix Hydrogen Combustion Applied to M1A-17 Gas Turbine
Authors: Horikawa Atsushi , Okada Kunio , Yamaguchi Masato , Aoki Shigeki , Wirsum Manfred , Funke Harald H.-W. , Kusterer Karsten 
Published: September 2021

Abstract
Kawasaki Heavy Industries, LTD. (KHI) has research and development projects for a future hydrogen society. These projects comprise the complete hydrogen cycle, including the production of hydrogen gas, the refinement and liquefaction for transportation and storage, and finally the utilization in a gas turbine for electricity and heat supply. Within the development of the hydrogen gas turbine, the key technology is stable and low NOx hydrogen combustion, namely the Dry Low NOx (DLN) hydrogen combustion.
KHI, Aachen University of Applied Science, and B&B-AGEMA have investigated the possibility of low NOx micro-mix hydrogen combustion and its application to an industrial gas turbine combustor. From 2014 to 2018, KHI developed a DLN hydrogen combustor for a 2MW class industrial gas turbine with the micro-mix technology. Thereby, the ignition performance, the flame stability for equivalent rotational speed, and higher load conditions were investigated. NOx emission values were kept about half of the Air Pollution Control Law in Japan: 84ppm (O2-15%). Hereby, the elementary combustor development was completed.
From May 2020, KHI started the engine demonstration operation by using an M1A-17 gas turbine with a co-generation system located in the hydrogen-fueled power generation plant in Kobe City, Japan. During the first engine demonstration tests, adjustments of engine starting and load control with fuel staging were investigated. On 21st May, the electrical power output reached 1,635 kW, which corresponds to 100% load (ambient temperature 20 °C), and thereby NOx emissions of 65 ppm (O2-15, 60 RH%) were verified. Here, for the first time, a DLN hydrogen-fueled gas turbine successfully generated power and heat.
Turboprop Engine Loading During High and Low Maneuver Intensity Flight Mode
Authors: Templalexis Ioannis , Giachalis Lambros , Lionis Ioannis 
Published: September 2021

Abstract
The life consumption rate of the aircraft engine is a vital input for aircraft operators who aim to an efficient fleet management. T6 aircraft, propelled by the PT6 turboprop engine, is operated by the Hellenic Air Force, both for training and aerobatic purposes. The current study focuses on quantifying and comparatively assessing the engine life consumption rate for the following missions: i) An “aerobatic” mission which is a typical high intensity maneuver flight and ii) a “training for patrol” mission, representing a typical low intensity maneuver flight. Missions were selected with the criterion of setting the lowest and the highest possible engine loading during a certain mission. In other words, the goal of the study is to define the extent of the loading the engine can encounter as a propulsion system of the T-6 aircraft during a certain mission. This is the first step before proceeding in setting up a methodology for continuously monitoring the engine life consumption rate in support of the squadron flight management plan. The study was based on real time data recorded during the respective flights. An engine model built using “GasTurb” gas turbine simulation software was used to fill in engine operating data at stations where recordings have not been taken. Engine life consumption was based on creep and low cycle fatigue failure mechanisms of the first gas generator turbine stage. Creep life fractions were calculated based on the Larson-Miller parameter curves and the fatigue cycles were counted using the rainflow method. The study showed that the life consumption is about 10 times lower when the aircraft is operated at a low loading mode as opposed to a high loading mode.