bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser Additive Manufacturing of Iron-Aluminum for Hybrid Steam Turbine Blades
Authors: Rittinghaus Silja-Katharina , Hama-Saleh Rebar , Brunn Oliver , Salit Victor , Mokulys Thomas 
Published: October 2022

Abstract
The optimization of steam turbine rotor blades is strongly restricted by centrifugal stresses. To reach higher rotational speed or to obtain larger airfoils it is desirable to realize blade designs with very light, but robust blade tips. Hence, the aim for a composite material design of a turbine blade is to investigate a new method of providing raw material for turbine blades which consists out of standard turbine steel around the root section and much lighter material on the outer diameter of the blade.
Iron aluminide alloys are of increasing interest as a structural material for lightweight construction in hot or corrosive environments due in part to the good and economical availability of the main alloying elements. Currently, the feasibility is being tested of replacing component areas with FeAl through hybrid construction, depending on local load requirements, and thus achieving effective weight reduction. The additive process laser-based direct energy deposition (L-DED) of Fe-28Al is investigated to produce hybrid material consisting of 12% Cr turbine steel and Fe-Al.
Parameters and build-up strategies are varied in order to produce a crack-free and low-stress connection of the material partners while complying with given thermal boundary conditions. Thermography is used to achieve homogeneous process conditions when scaling to component size. Microstructure, hardness and chemical composition of the hybrid material are investigated as well as mechanical strength. It is shown that crack-free machining of test specimens and a component blank is possible after heat treatment.
Towards Fast Prediction of Flame Stability and Emissions of mGT Combustion Chambers: a Chemical Reactor Network Approach
Authors: Savarese Matteo , Bompas Jérémy , De Paepe Ward , Parente Alessandro 
Published: October 2022

Abstract
Hydrogen as energy carrier, in combination with dry, low-NOx micro gas turbines (mGTs), is receiving increasing attention, since it can represent an attractive solution for a low-carbon, highly efficient and decentralized energy restitution system. However, accommodating hydrogen-enriched fuel blends in already existing combustion technologies is not an easy task, due to the increased reactivity of this fuel and the higher associated NOx emission. In this framework, reliable numerical models are needed to assist the industry towards the re-design of existing combustion assets. In particular, predicting thermal efficiency and pollutant emissions is of crucial importance for assessing the performances of a given system, since energy production facilities will have to cope with more stringent regulations. Alternative, physics-based modeling tools, such as Chemical Reactor Networks (CRNs), can represent an appealing solution for fast and reliable predictions of overall combustion efficiency and pollutants emissions. This tool allows to represent complex reactive flow fields as a series of idealized reactor models, thus drastically reducing the computational cost of the simulations. For this reason, detailed kinetic schemes can be employed. Detailed chemistry is crucial for reliable pollutants predictions, especially for NOx and CO, since the formation of those chemical species follows complex chemical pathways. The use of CRNs is quite frequent in literature, especially for performing parametric studies for gas turbines applications. The design of an equivalent CRN for a given combustor is based on the manual observation of the main flow-field features, which can be obtained from experiments or CFD data. The aim of this paper is to construct a highly simplified CRN of a typical mGT, Turbec T100 combustor, in order to perform design exploration studies. The effect of the main operating parameters, such as equivalence ratio, air inlet temperature and fuel composition was studied. Moreover, part load conditions were also simulated. Results highlighted that hydrogen addition does not systematically leads to increased pollutants emissions, since due to its higher reactivity, it offers the possibility to operate in leaner conditions, with respect to natural gas. The obtained results aim at providing useful guidelines for further experimental or detailed numerical design explorations for identified interesting conditions.
Computational Flow Field Assessment of the Inlet Region of Centrifugal Compressor Under Unsteady Flow Conditions Near Surge
Authors: Parikh Aakeen , Ale-Martos Pablo , Barrera-Medrano Maria Esperanza , Hayashi Yoshihiro , Martinez-Botas Ricardo 
Published: October 2022

Abstract
The centrifugal compressor of a turbocharger is affected by the opening and closing of the engine intake manifold and consequently experiences a pulsating backpressure. The imposed pulsating conditions generate internal losses and reduce the overall compressor performance and efficiency. However, previous studies have shown that these dynamic conditions can also lead to a surge margin improvement, benefiting the lower limit of stability, in certain conditions. The stability of the compressor arises from the flow behaviour in the inlet region and the interaction between the rotating and stationary components at the inlet. In this paper, the computational flow field of the inlet region of a centrifugal compressor under pulsating flow has been studied. A full stage, 3D URANS model of a compressor exposed to pulsating backpressure has been solved using ANSYS-CFX for the near surge operating point. The transient behaviour of this operating point has been studied at six instances in time within one cycle of the pulse. The flow field is assessed using Mach number, static entropy, static pressure and local flow direction in the inlet region. Flow separation regions have been identified. The authors propose that the variation in flow field at the inlet due to the dynamic response to the imposed boundary condition could explain the improvement in surge margin under pulsating flow conditions for this compressor system.
Design and Development of a Fast Response Torque Meter for Unsteady Flows in Turbocharger Applications
Authors: Parikh Aakeen , Singh Gunin , Noon Chris , Flora Harminder , Martinez-Botas Ricardo 
Published: October 2022

Abstract
A high-speed torque meter has been designed and tested for turbocharger applications in order to assess the effect of unsteady boundary conditions. The torque meter is designed using the shaft-twist method by measuring the change in relative angle between the two ends of the drive shaft. Two encoder wheels are mounted on either end of the shaft and a high-speed FPGA measures the variation of time between edges from optical switches. The angular twist in the shaft is calibrated against a reference torque transducer over a range of torque values. The torque meter is installed on an existing compressor rig testing facility at Imperial College London equipped with a pulse generator capable of producing different pulse frequencies and amplitudes. To test the response to unsteady conditions, a centrifugal compressor is driven under a pulsating backpressure while torque is measured at the drive shaft. The torque measurement is compared against static pressure measurements corresponding to the pulsating conditions. Twelve combinations of frequency and pulse amplitudes have been tested. Due to its simple construction and development, the authors believe that where high-speed measurement equipment is already in place, effective torque measurements of this kind can be added with a low cost to help explore unsteady performance in turbomachinery.
Optimization of a Turbomachinery Blade With Regards to Tip-Rub Events
Authors: de Cherisey Marin , Salles Loic , Renson Ludovic , Vizzaccaro Alessandra , Wong Chian 
Published: October 2022

Abstract
Tip-rub events, also called blade-casing interactions, are problematic structural phenomena that can lead to complete engine failure. They mainly occur in compressors when a blade tip touches the casing and starts vibrating. If one of the blade natural modes is excited by an engine order, this can lead to an uncontrolled resonance. Therefore, the understanding and the consideration of these interactions is crucial to the development of safe aircraft engines.
Various numerical models and dynamic simulators have been developed, including the in-house one, jm62. It implements a stick-slip model and considers a potential liner and casing wear. Even if it gives precise results, it is computationally expensive and needs a significant amount of post-processing. It is therefore not really adapted to early design stages or quick automated processes (parametric study or optimization).
An automated workflow using SALOME-MECA and its sub-modules had been developed and permits to perform simple and fast parametric studies and shape optimizations. The proposed tool has been used to study the influence of the twist, lean, sweep and tip thickness-to-chord ratio on a modified version of a NASA Rotor 37 blade. The risk of high-level vibration of a blade due to tip-rub events is assessed using the concept of clearance consumption. The clearance consumption is defined as the component of the linear or nonlinear mode shape that defines the distance between the tip of the blade and the casing. From the reference blade and the parametric study results, an optimized candidate was generated using the clearance consumption as the objective function to minimize This process resulted in a geometry with a lower twist angle and a significant forward sweep. Two scenario of tip rub events have been performed on the optimised blades. The testing relies on the in-house time integration software jm62. The candidate has showed a 85% reduction in the amplitude of the vibratory response for the first scenario, demonstrating that the clearance consumption can be used to perform successful shape optimizations for tip-rubbing.
Validation of New Numerical Analysis Tools for Nonlinear Forced Response in Anisotropy-Mistuned Bladed Disks With Friction Joints
Authors: Koscso Adam , Hartung Andreas , Petrov E. P. 
Published: October 2022

Abstract
New numerical tools ContaDyn and InterDyn have been developed at University of Sussex for the analysis of nonlinear forced response for tuned and anisotropy mistuned bladed disks with friction contact interfaces. The tools offer capabilities for calculating the nonlinear forced response and its sensitivity with respect to the anisotropy orientation variation of single crystal blades in tuned and mistuned bladed disk assemblies. The calculation method is based on the high-accuracy reduction techniques and the multi-harmonic balance method.
A comprehensive validation campaign has been done to validate these numerical capabilities. The calculated nonlinear forced responses are compared with the experimental values obtained for different bladed disk configurations and excitations. The friction contact interfaces at blade roots, blade shrouds and under-platform dampers are considered. For the validation, the measurement data, that were obtained earlier at MTU Aero Engines AG using their rotating test rig, are used. The vibratory measurements were carried out with the contact-less expected time-of-arrival method allowing capturing the vibratory amplitudes for all blades in a mistuned bladed disk assembly.
The nonlinear forced response for tuned and anisotropy mis-tuned bladed disks have been calculated for four different resonances and compared with the minimum, maximum and mean values of the measured amplitudes. Moreover, the individual blade forced response levels obtained from measurements and calculations are compared with the maximum amplitude distributions in the mistuned bladed disks. Parametric studies considering the number of harmonics used in the multiharmonic representation of periodic response, the number of mode shapes, the contact stiffness and friction coefficient values have been performed.
Flow Dynamics of a Subsonic Axial Compressor Rotor With Leaned Tandem Blades
Authors: Kumar Amit , John Jerry T. , Kumar Akshay , Chhugani Hitesh , Pradeep A. M. 
Published: October 2022

Abstract
For higher diffusion, tandem blading has demonstrated performance superiority over a conventional blade. Modern compressor blades are often designed with three-dimensional blade shapes such as sweep, lean, dihedral, end bent etc., to achieve optimum performance. However, the performance benefit reported due to the three-dimensional blade shapes have been design-specific. Since a tandem rotor involves an unconventional design approach, each aspect of the 3D blade design needs to be looked at separately. The present numerical study aims to investigate the performance of a tandem rotor with lean. The performance of the leaned tandem rotor is also compared with the conventional leaned rotor. Positively leaned tandem configurations exhibited a higher total pressure rise than the other configurations, but at the expense of the operating range. On the other hand, a significant improvement in the operating range is observed for the negatively leaned tandem rotor. This, however, comes with a total pressure penalty. For the negatively leaned tandem rotor, a higher mass flow migration towards the tip region is observed. This reduces the effective incidence of the rotor tip. Therefore, a higher stall margin is observed for the negatively leaned tandem rotor. However, a higher tip incidence angle for the +20° leaned tandem rotor results in an early breakdown of the forward rotor tip leakage vortex, resulting in a lower stall margin. Although incorporating lean within the design of conventional rotor has certain performance benefits, it appears to be more beneficial for the tip sensitive tandem rotor design.
An Iterative Neural Operator to Predict the Thermo-Fluid Information in Internal Cooling Channels
Authors: Yang Li , Wang Qi , Rao Yu 
Published: October 2022

Abstract
The design of internal cooling channels played an important role in turbine cooling. Distributions of thermo-fluid information, including surface distributions, cross section distributions and projected distributions are common forms of data for internal cooling research. For over half a century since 2-D thermo-fluid data were obtainable, there were very few universal tools to regress images. While several mathematical methods worked well with regressing zero-dimensional data, they were hardly compatible with 2-D data. Recent progress in the deep learning domain provided capability for image regression by using a convolutional feature encoding-decoding process. However, deep learning models usually had a huge number of trainable parameters, which substantially reduced the generalization accuracy on small datasets. Therefore, the convective heat transfer field has been continuously searching for reduced ordered models to regress images that could generalize on an obtainable small dataset. This study proposed a reduced ordered model to regress thermo-fluid image data by integrating the physics nature of thermo-fluid problems with neural networks. This effort started from a general partial differential equation and utilized a series of derivation to convert the equations into a recurrent convolutional neural networks. By releasing the convolutional kernels to trainable parameters and using data to train the kernels, a single layer convolutional neural networks could accurately replace a spatial advancing step of the thermo-fluid image within an iteration step. The recurrent convolution neural networks were tested on a convective heat transfer dataset obtained from simulating a cooling channel with random surface patterns on one side. The tested data included the temperature distribution on the cooled solid surface, the projected heat flux image on the fluid-solid interfaces, and the pressure distribution in the middle cross section. Results indicated an excellent regressing accuracy of the presented model for the three types of data, which was elevated as compared with a widely used cGAN deep learning model. Most importantly, the proposed model only consumed 1/290 trainable parameters as compared with the cGAN model. The key features that led to the success of proposed reduced ordered model included: the matching between the differential nature of a convention-diffusion phenomenon and the convolution calculation process, the compliance of the time evolution nature of thermo-fluid images with the recurrent structure of the model, the embedding of boundary condition images into the inputs, and the introduction of hidden state images into the networks.
High-Order Spectral/hp Compressible and Incompressible Comparison of Transitional Boundary-Layers Subject to a Realistic Pressure Gradient and High Reynolds Number
Authors: Vivarelli Guglielmo , Isler João Anderson , Montomoli Francesco , Sherwin Spencer J. , Adami Paolo 
Published: October 2022

Abstract
Within the literature, there are limited high-order results concerning large Reynolds number flows under the influence of strong adverse pressure gradients, mainly due to the computational expense involved. The main advantage in employing high-order methodologies over standard second-order finite-volume solvers, relates to their ability to increase accuracy with a significantly lower number of degrees of freedom. In theory, this would permit Direct Numerical Simulation sort of analysis. Yet, there is still a significant computational cost involved. For this reason, an efficient approach to analyse such flows by means of a Nektar++ high-order Implicit Large Eddy Simulation is proposed.
The flow conditions considered in this case cause a separation bubble to form with consequent turbulent transition. In particular, Tollmien-Schlichting instabilities trigger Kelvin-Helmholtz behaviour, which in turn cause the turbulent transition.
The bulk of the study will be carried out with the incompressible flow solver, as it is assumed that compressibility effects are negligible within the boundary layer. An initial 2D analysis will be conducted to determine the necessary spatial resolution and whether it is possible to consider a subset of the overall simulation domain to reduce the computational expense. Once this will have been established, the 3D results will be achieved by Fourier expansion in the cross-flow direction. These results will prove the cost-effectiveness of the methodology, that could be used within an industrial setting with a limited turn-around time. Additionally, a comparison between the results achieved by means of the Nektar++ compressible flow solver in 2D and 3D will be provided, to assess any differences that may be present.
Assessment of Thickened Flame Model Coupled With Flamelet Generated Manifold on a Low-Swirl Partially Premixed Gaseous Lifted Flame
Authors: Langone Leonardo , Amerighi Matteo , Mazzei Lorenzo , Andreini Antonio , Orsino Stefano , Ansari Naseem , Yadav Rakesh 
Published: October 2022

Abstract
The present work focuses on the numerical modeling through Large Eddy Simulations (LES) of a low-swirl partially premixed lean flame operated with gaseous fuel using a hybrid Thickened Flame (TF)-Flamelet Generated Manifolds (FGM) combustion model. This approach aims to overcome the challenges of modeling the flame lift-off in this burner and the stabilization of the reaction zone at a remarkable distance from the nozzle outlet section, for which the reproduction of finite rate effects on combustion physics is crucial. The underlying strategy consists of applying the artificial thickening to the scalar equations required for the query of the look-up table computed a priori. The mentioned combustion model has been implemented in a general-purpose commercial CFD solver and Non-Adiabatic Flamelets have been employed for the look-up table computation. The goal is to include a detailed chemistry description while maintaining a cost-effective approach and improving the reproduction of the turbulence-chemistry interaction. Results are validated with experimental data in terms of temperature and chemical species concentration maps, showing the potential of the coupled TF-FGM approach for describing this type of flame.
Integration of Secondary Airflow Modeling Into Synergetic Cycle Calculation of F Class Industrial Gas Turbine
Authors: Staple Shanel , Vogel Gregory , Torkaman Alex , Khandrymailov Andrii , Yevlakhov Viktor 
Published: October 2022

Abstract
Industrial gas turbines are complex systems, and their proper analysis requires specific knowledge of the different components interacting with each other. One of the challenges is to accurately predict the overall performance of the system. To do so, a performance analysis tool can be used but it needs to rely on representative characteristics from the different elements. One of the key items required for the performance derivation is the understanding of the total cooling and leakage air (TCLA) and its distribution within the machine. A secondary air flow (SAF) tool is used to evaluate TCLA, but it needs to be “connected” with the overall performance model. The source locations of the SAF system are relatively straightforward to handle, but the sink (or dump) locations occurring in the turbine section require a detailed understanding of the pressure distribution within the flowpath. As a matter of fact, a change in SAF distribution to the turbine yields a change in turbine work output and load distribution that needs to be captured in the overall engine performance assessment. Furthermore, a change in turbine inlet boundary conditions also yields a change in pressure values for the SAF system. For these reasons, an accurate performance modeling of a gas turbine requires a so-called Synergy Loop to converge the overall boundary conditions of all its interacting modules and sub-models. This paper will describe the method used to integrate different commercial and in-house software to complete the Synergy Loop. The authors will also describe the different iteration steps possible between the specific components and the recommended iteration loop sequence for fast convergence.
Effect of Location and Rotational Reynolds Number on Film Cooling of Rotating Blade Pressure Side
Authors: Long Meng , Haiwang Li , Gang Xie , Zhiyu Zhou 
Published: October 2022

Abstract
The film cooling performance on the pressure side of turbine blades with single-row film holes is experimentally investigated. Three blades with single-row film holes at three locations (x/S = 10%, 29%, and 48%) of the pressure-side are studied at three rotating Reynolds numbers of 3.6 × 105, 5.4 × 105, and 7.2 × 105 (i.e., the rotational speeds of 400 rpm, 600 rpm, and 800 rpm). The pressure-sensitive paint (PSP) technology is used to measure the film cooling distribution at three blowing ratios (BR = 0.50, 1.00, and 1.50). The results indicate that the film cooling performance varies with the location of pressure side. Upstream of the pressure side, the film cooling performance is poor, with the film trajectories deflecting mainly upward. Downstream of the pressure side, the cooling effectiveness is higher, with the film trajectories deflecting upward and downward. The film trajectories closer to the downstream location are longer than those upstream, and are more prone to detach from the wall at higher blowing ratios. Moreover, the cooling performance slightly improves as the rotating Reynolds number increases.