bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Fidelity Simulation Study of the Unsteady Flow Effects on High-Pressure Turbine Blade Performance
Authors: Leggett John , Zhao Yaomin , Sandberg Richard D. 
Published: October 2022

Abstract
Unsteadiness, in the form of both broadband background disturbances and discrete coherent wakes, can have a strong effect on the performance of turbomachinery blades. The influence of the state of the incoming flow has received much interest in turbomachinery research as it inevitably affects the state of blade boundary layers and develops as it passes through the machine. In the work presented here we build on this knowledge and further investigate the effect of unsteady flow on high-pressure turbines (HPT), using high fidelity data sets of an HPT stage produced using wall resolved large-eddy simulation (LES) (Zhao and Sandberg, GT2021-58995). The effects of incident wakes from an upstream stator, compounded by the presence of free-stream turbulence, on the performance of a downstream rotor are investigated. Based on analyzing cases for which the incoming turbulence is prescribed with different turbulence intensities and length scales, we show that changing the free-stream turbulence characteristics has a direct effect on the unsteady behavior of the stator wakes. As a result, the aerothermal performance of the rotor is also significantly affected. By detailing the influence of the wake-turbulence interaction on the performance of the rotor, we aim to distinguish driving forces on rotor performance, be it changes in the incident wakes or direct influence from the free-stream turbulence. Furthermore, the different aerothermal behaviours on the pressure-side and suction-side of the rotor blades have been extensively investigated, showing that the blade boundary layers on the suction and pressure sides respond differently to external disturbances. The insights gained can provide designers with guidelines in understanding the unsteady flow effects of a given flow state, and how the turbulence present, either broadband or deterministic, will affect the performance of downstream blades.
Transient Engine Condition Monitoring of Micro Gas Turbines in a Highly Dynamic Setting
Authors: Varchev Tihomir , Weiss Matthias , Staudacher Stephan , Koch Christian 
Published: October 2022

Abstract
Measurements recorded continuously throughout a flight at high sampling rates facilitate transient engine condition monitoring. This promises the generation of a large number of residual values resulting in improved detection and identification of engine component faults. The wavelet transformation is directly applied to residual values in a moving window followed by image classification using a Deep Convolutional Neural Network to detect and identify engine faults. This approach is demonstrated using simulated in-flight residual values considering Gaussian noise and measurement bias as well as engine deterioration. Three types of component faults were investigated. They are a change in efficiency, flow capacity and a combination of those two. The capability of the approach to detect and identify engine component faults was examined in three numerical experiments of increasing complexity. If a fault was detected, the approach was capable of correctly identifying the faulty engine component in all three numeric experiments. However, the ability of the approach to detect the presence of an engine component fault as well as its ability to correctly identify the particular fault type were shown to be affected by measurement uncertainty and engine deterioration.
Thermal Bowing of Steam Turbine Shafts: Prediction Methods and Field Data Matching
Authors: Vegesna Rama Raju , Checcacci Damaso , Girezzi Gabriele 
Published: October 2022

Abstract
The availability of steam turbines for prompt start-up, especially from hot or warm conditions, relies on the correct conditions for turbine cooldown, involving both the external casing and the shaft.
While several works are available about the prediction and optimization of cooling for steam turbines, with focus on casing temperature matching and shell thermal humping prediction, very little is available with reference to rotor bowing. Yet, in case the shaft is not maintained in slow turning during cooling, its bowing can very quickly lead to large unbalance and, eventually, to the impossibility of further turning, because of internal rubbing. These conditions may lead either to very high vibrations at restart or to the unavailability of the turbine, requiring its complete cooldown to fully recover the thermal bowing and allow a safe restart. In this work the modelling of thermal bowing of steam turbine shafts is presented. The bases of the adopted physical model are discussed, along with the necessary assumptions about transient fluid conditions around the hot shaft during its cooling at stand-still. The main model parameters affecting the shaft bowing are analysed and the transient displacements resulting from the thermal model are then quantitatively compared, for matching, with real field data. The best selection of model parameters and adopted assumptions are finally discussed.
Development, Atmospheric Testing and Field Operation of a Fuel Flexible Gas Turbine Combustion System for Crude Oil Volatile Organic Compounds
Authors: Bouten Thijs , Gralike Nick , Axelsson Lars-Uno 
Published: October 2022

Abstract
Volatile Organic Compounds (VOCs) evaporate from crude oil due to their volatile characteristics. These VOCs are conventionally vented, thereby contributing significantly to the harmful emission in the crude oil loading, storage and transport on offshore platforms, ships, storage tanks, terminals and shuttle tankers. The VOCs can be captured by a VOC recovery system, thereby reducing the harmful emissions significantly. The heavier fractions (mainly C3+) out of VOCs can be stored as liquid VOC (LVOC). The non-condensable fraction is a surplus gas (SVOC) mainly consisting out of lighter hydrocarbons and inert gases. The composition of LVOC and SVOC significantly varies depending on the type of crude oil. The application of both LVOC is challenging due to the high volatility, high dew point and varying compositions, while the SVOC is challenging because of the high variation in inert gas concentration, which depends on the crude oil level in the cargo tank. This paper will present the development and testing of a new tubular combustion system that can operate on the LVOC and SVOC from a VOC recovery unit as well as on LNG in case the VOC recovery plant is not operational. The challenges of the high variety in fuels are mainly translated in a dedicated fuel nozzle for the low calorific fuel combustor. This novel nozzle allows for stable operation on a wide variety of fuels with limited supply pressure requirements.
The combustor has been tested in OPRA’s state-of-the-art atmospheric combustor test rig. Hereby various fuels have been supplied. The results presented in this paper focus on the validation of flame stability, operational window, turn down and emissions operating on different mixtures of low calorific gas (SVOC) and high calorific gas (LVOC, propane and natural gas).
After successful completion of the atmospheric testing, a full-scale engine test has been performed with the OP16 gas turbine in OPRA’s engine test cell. Multiple gensets are installed on shuttle tankers and have been successfully commissioned with the various fuels. Operational experience from these sea trials are discussed. It has been proven that the OPRA OP16 gas turbine can utilize 100% of the VOC emissions recovered from the shuttle tanker, whereby power is supplied to the vessel. This results in a significant reduction of the ship’s emissions.
Experimental Investigations of Hydrogen Fuelled Pulsed Detonation Combustor
Authors: Cojocea Andrei V. , Cuciuc Tudor , Porumbel Ionuţ , Gall Mihnea , Gherman Bogdan , Crunţeanu Daniel E. 
Published: October 2022

Abstract
Detonation combustion unveils avenues towards increased performances and efficiencies of classic deflagration architectures and enables opportunities for supersonic flight platforms. Furthermore, their primarily fuel candidate, Hydrogen, which is prone to detonation, has enormous potential in both industrial and mobility decarbonization. Nonetheless supersonic flame propagation is associated with disadvantages in terms of aerodynamic and thermal losses, which raises difficulties in achieving practical applications. Moreover, to achieve a safe and reliable energy conversion, Hydrogen combustion needs special attention. This paper addresses the analysis of a Hydrogen fuelled pulsed detonation combustor, to contribute to the understanding of the high-speed mixing performance and to improve the specific know-how regarding pressure gain combustors. By means of Z-type Schlieren visualization technique, the structure of the engine’s exhaust plume is determined to capture the intrinsic unsteady phenomena of the detonation process. Qualitative instantaneous static pressure results are presented and correlated to the Schlieren images to evaluate the cycle stages and its operating frequency.
A Linearization Method Based on 3D Contact Model for the Steady-State Analysis Towards Complex Engineering Structures Containing Friction
Authors: Xiao Fucai , Li Lin , Wu Yaguang , Fan Yu , Zhang Hui 
Published: October 2022

Abstract
In this paper, a linearization method based on 3D contact model for the steady-state response analysis of dry friction systems is proposed from the perspective of engineering application. The core is to equivalently express the nonlinear force described by the 3D contact model into distributed local linear damping and stiffness by means of linearization, and apply it to the finite element model of linear substructures with MATRIX 27 elements. In this way, the steady-state response can be calculated in ANSYS. The 3D contact model ensures the accuracy of the algorithm, and the linearization improves the efficiency. Besides, the stress can be directly displayed in ANSYS post-processing. The effectiveness and efficiency are verified both on the contact interface level and the structure level. Finally, the proposed method is applied to a real multi-stage stator casing with a friction ring damper. Results show that for this finite element model with 1944 nonlinear degrees of freedom, the average calculation time for one frequency is less than 5 s. The larger the scale of the model, the greater the benefit of efficiency.
Analysis of Cavity Leakage Effects on Coupled Non-Axisymmetric Endwall-Airfoil Optimization in a Low-Speed Compressor Tandem Stator
Authors: Straccia Mattia , Giannini Samuele , Gümmer Volker 
Published: October 2022

Abstract
This paper aims at describing the effects of the hub leakage flow on non-axisymmetric endwall contouring and airfoil optimization in a highly-loaded tandem vane, in order to give a better understanding of the potential of the approach, independently of the seal leakage. Since its first applications on highly-loaded compressor stages, it has been highlighted how the non-axisymmetric contouring can be effective in manipulating the secondary flow behavior close to the endwalls. Many cases have proven its positive influence on the flow field behavior for single and tandem vanes, drawing general guidelines for the preliminary design phase, thanks to the usage of optimization tools. An interesting question still to be addressed in a general sense is at which specific conditions designers should rely on endwall contouring and when they should not, considering the obvious additional manufacturing expenses associated. First studies on this subject, assumed the interchangeability of non-axisymmetric endwall contouring with radial stacking laws. Nowadays, fully 3D optimized airfoil geometries being state of the art, it appears evident that new general guidelines are needed. In this context, the influence of the hub leakage flow on the definition and effectiveness of the endwall contouring is investigated, isolating its beneficial influences, which will be described independently of the topology of the low momentum fluid present close to the endwalls. Therefore, the reference geometry is varied in mass leakage flow by varying the geometry of the cavity of the shrouded tandem stator arrangement. Then, the new configuration is optimized via non-axisymmetric endwall contouring and hub airfoil profile optimization, carried out by means of a meta-heuristic approach. The investigation based on total pressure losses and static polytropic efficiency will show the break-even point of the beneficial influence of the non-axisymmetric contour with respect to the reducing leakage mass flow. Moreover, the change of design strategies adopted by the optimizer among the different flow field configurations shall serve as a reference guide for every future design choice incorporating non-axisymmetric endwall contouring.
Estimation of Resultant Airframe Forces for a Variable Pitch Fan Operating in Reverse Thrust Mode
Authors: Rajendran David John , Tunstall Richard , Pachidis Vassilios 
Published: October 2022

Abstract
The resultant forces with a reverse thrust Variable Pitch Fan (VPF) during the aircraft landing run are computed from the installed reverse thrust flow field obtained from an airframe-engine-VPF research model. The research model features a reverse flow capable VPF design in a future, geared, high-bypass ratio 40000 lbf engine as installed onto a twin-engine airframe in landing configuration, complete with a rolling ground plane to mimic the runway. The reverse thrust flow field during the aircraft landing run is obtained from 3D RANS/URANS solutions of the model. The evolution of the installed dynamic reverse thrust flow field is characterized by the interaction of the VPF induced reverse flow with the free stream. Several flow features like reverse flow wash-down by the freestream, external swirling helical flow development, pylon flow obstruction, 180° flow turn into the engine, subsequent separated flows, wake interactions and multi-pass recirculating flows are observed.
The resultant airframe forces due to the reverse thrust flow field is estimated by adaptations of momentum based far-field and near-field methods. In the active thrust reverser engagement regime of 140 to 40 knots, the VPF generates a sufficient axial airframe decelerating force in the range of 45% to 8% of maximum take-off thrust. A drag decomposition study and a notional ‘blocked-fan’ analysis are described to understand the stack-up of the axial decelerating force. Additionally, the resultant force has a landing speed dependent lateral force component because of the pylon obstruction induced flow non-uniformity. A beneficial downforce component due to upward deflection of streamlines is also observed. The quantification of the resultant forces from the baseline installed airframe-engine-VPF reverse thrust flow field is a necessary step to explore the feasibility of the VPF reverse thrust system for future efficient turbofan architectures, understand force generation mechanisms and to identify areas for subsequent design improvement.
Assessment of Low Engine Order Excitation of a Contaminated Turbocharger Radial Turbine Stage Using a Nozzle Ring Only Computational Model
Authors: Beierl Michaela R. , Vogt Damian M. , Fischer Magnus , Müller Tobias R. , So Kwok Kai 
Published: October 2022

Abstract
The use of critical fuels such as Heavy Fuel Oil (HFO) usually leads to deposits of combustion residues in the turbocharger turbine stage, foremost in the nozzle ring where flow channels can get partially or completely clogged. The resulting change in geometry is heavily asymmetrical and therefore induces Low Engine Order (LEO) excitation, which may lead to resonant excitation of rotor blades and potentially to High Cycle Fatigue (HCF) failure. The accurate prediction of LEO excitation is computationally intensive especially in the context of a probabilistic analysis.
The current study investigates the suitability of using a simplified model that only contains the nozzle ring in the assessment of LEO excitation with the goal to reduce computational costs. The aerodynamic excitation is assessed from the circumferential variation of the nozzle ring outflow. The results obtained with this simplified model are compared to results of validated forced response analyses. Two deteriorated nozzle rings are used for validation purposes, a generic one having one passage blocked by 90 percent and a digital replica of a real contaminated nozzle ring. It is shown that the simplified model is suitable for the qualitative prediction of the aerodynamic excitation if the contamination patterns feature sufficiently large differences and that the computational costs can be greatly reduced.
Improving the Aerodynamic Performance of a High-Loading Turbine Blade by End-Wall Surface Structures
Authors: Xi Yueyun , Lu Shaopeng , Jiang Hongmei , Zhang Qiang 
Published: October 2022

Abstract
In turbomachinery, the end-wall secondary flow introduces significant aerodynamic penalty, especially for high-loading turbine blade designs. The advances in manufacturing technology offer increased design flexibility, especially on surface structure design and fabrication, opening a new option for secondary flow control. The present combined experimental and numerical study explores the potential aerodynamic performance benefit of end-wall surface structures. Aerodynamic loss measurements were performed by using a five-hole probe in a low-speed wind tunnel. The secondary flow structures of blades with normal and high loading were studied. End-wall surface structures were added to the high-loading blade design to mitigate the secondary flow developments. RANS CFD was conducted with the same inlet and exit boundary conditions measured in the experiments. Both the numerical and experimental results demonstrate that the end-wall surface structures can effectively reduce the secondary flow loss and alleviate the lift-off motion of passage vortex. The working principle of the end-wall structures is revealed through detailed analysis of the end-wall region flow structure. The end-wall structures have to be carefully designed according to the local development of secondary flow, and there is a large space for design optimization.
Mitigation of BLI Circumferential Distortion Using Non-Axisymmetric Fan Exit Guide Vanes
Authors: Hall David , Greitzer Edward , Tan Choon 
Published: October 2022

Abstract
This paper presents an assessment of the effect of non-axisymmetric fan exit guide vanes (FEGVs) to mitigate, or even reduce to zero, the impact of circumferential flow distortion — such as created by boundary layer ingestion (BLI) — on fan rotor efficiency and vibratory structural forcing. The fan response to circumferential non-uniformities is characterized, for two-dimensional flow, in terms of the variations in incidence angle and unsteady rotor forces. FEGV designs with non-axisymmetric exit flow angle perturbations can eliminate either of these. More importantly, non-axisymmetric stator row designs can reduce both non-uniformities relative to the influence of an axisymmetric stator row. This suggests that design for distortion need not involve a trade-off between performance and aeromechanics; a non-axisymmetric aerodynamic design approach can improve both simultaneously. Analysis of the impact of stage design parameters has been carried out to determine FEGV exit flow angle variations that shield the rotor from the adverse effects of circumferential distortions representative of BLI. The results indicate inlet distortion effects can be mitigated with realizable non-axisymmetric FEGVs. The magnitude of the geometry variations required decreases with decreased axial rotor-stator spacing and increased flow coefficient.
On the Scatter of Creep Data: Methods to Increase Modelling Accuracy Accounting for Batch-to-Batch Dispersion
Authors: Riva Andrea 
Published: October 2022

Abstract
Gas turbine components and many industrial high temperature components suffer from creep, a viscous effect of the material that induce irreversible deformation, microstructural damage, and eventually failure. Creep strain (where the creep strain εcr is a function of time, stress, temperature) and creep rupture models (where the rupture time texp is a function of stress and temperature) are fitted to the results of expensive and time-consuming experimental tests, which can last for several years (e.g. test duration up to 100kh – 200kh). At longer times, in the range of components expected life target, when it is more likely to observe creep damage, the accuracy of creep models is required to be as high as possible. It is therefore crucial to optimize the model fitting process in order to minimize the error and reduce the number of tests required. To achieve such results the experimental result dispersion needs to be properly addressed. In particular, the differences between the different heats of the same material are known to be a dominant source of uncertainty in the experimental results. The differences are mainly linked to small variations in the fabrication process or chemical composition (even within the allowed variations of the purchase specification or standard recommendations), which can generate different microstructures and mechanical behavior. This is known as batch-to-batch dispersion and this phenomenon is responsible for significant creep strength differences between heats.
It is essential for the model reliability to gain the best possible insight of how the model itself can be influenced by the peculiarities and homogeneity of the available data. In order to achieve such goal, many analyses can be performed: quantitative identification strong/weak batches, analysis of the dataset inhomogeneity (i.e. a predominance of weak batches at a certain temperature or times), identification of correlations (e.g. tensile strength and chemistry, etc.), identification of creep mechanisms transitions that affect the applicability range of the model.
A statistical analysis of the test results is conducted in order to enable a non-deterministic modelling of creep rupture and strength, separately accounting for in-batch and batch-to-batch sources of dispersion. The soundness of the proposed probabilistic framework is validated via Monte Carlo simulation.
The paper is intended to provide an overview of the most recent proposals and progresses of the existing methods to deal with the problem and propose additional original methods to improve the analysis and the fitting procedure.