bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on Aerodynamic Axial Force in Single Rotor-Stator Cavity of a Gas Turbine
Authors: Jia Xingyun , Hou Qiyang , Zhang Le 
Published: October 2022

Abstract
To reveal the mechanism of the effect of rotor-stator cavity on the aerodynamic axial thrust of gas turbine rotor, a test rig for aerodynamic axial thrust of the rotor-stator cavity and the corresponding numerical model are proposed in this research. The geometric parameters and boundary conditions of the rotor-stator cavity numerical model and test rotor-stator cavity are modeled by the thermodynamic parameters and operational conditions of the real marine gas turbine. In this research, the aerodynamic induced axial force of one rotor-stator cavity can be visualized, measured, and directly collected dynamically for the first time. Flow characteristics, pressure distributions in rotor-stator cavity are analyzed, and the reliability of the test method is verified.
Influence of Casing Groove on Rotating Instabilities in a Low-Speed Axial Compressor
Authors: Chen Xiangyi , Koppe Björn , Lange Martin , Chu Wuli , Mailach Ronald 
Published: October 2022

Abstract
Rotating instability (RI) can be regarded as a pre-stall signal because such phenomena are usually detected when a compressor operates at a near stall point. Since RI is closely relevant to aerodynamic, acoustic, and structural issues, its mechanism has attracted industrial concerns and in-depth analysis. In this paper, a low-speed axial single compressor rotor row is selected as the baseline research object. A circumferential casing groove is mounted over the shroud. The solid casing and the casing treated configurations were simulated using the zonal large eddy simulation model, and the simulations present remarkable predictions in capturing the averaged and the dynamic characteristics of the investigated compressor. By implementing a data-driven method called dynamic mode decomposition, the mode with the highest amplitude is proved to be correlated to the dominant RI frequency. The spatial and temporal property of the RI is visualized. The results show that the casing groove has limited influence on the averaged flow field but manipulates the dynamic features. The groove allows the RIs to shift from around 0.5 blade passing frequency to higher frequencies in the upstream region and effectively suppresses the unsteadiness in the zones under and downstream of the groove. The RIs are triggered by the flow interaction of the tip leakage flow at the front part of the blade. It can be depicted as pressure waves staggering with the rotor blade and propagating over the blade tip region at around half of the blade speed. With the existence of the casing groove, the dominant wavelength changes, and the fluctuation is damped under the groove, which finally modifies the properties of RIs.
High-Fidelity Simulations of the Flow Around T106C Cascade at Low Reynolds Number: The Effects of Freestream Turbulence and Stagger Angle
Authors: Dufau Antoine , Marty Julien , Man Daniel , Piot Estelle 
Published: October 2022

Abstract
Flows in low-pressure turbines are highly dependent on the laminar-turbulent transition of the boundary layer and the separation of the laminar boundary layer. This study focuses on the flow around the T106C low-pressure turbine cascade blade for a low Reynolds number 100,000 and a moderately low turbulence intensity 0.8%. For this paper, three direct numerical simulations (DNS) are carried out to understand the discrepancies observed between the simulations and the experimental data. To that end, the effect of freestream turbulence intensity and blade stagger angle are investigated. A first simulation is performed without freestream turbulence, then a second one is performed with a modified stagger angle, and finally a third one is performed with an injection of synthetic turbulence at the inlet plane based on the synthetic eddy method (SEM). The results are compared to experimental data and RANS simulations. These comparisons show that there are still discrepancies between the flow predicted by the DNS and the experimental measurements. A comparison between DNS and RANS simulations highlights some leads to better understand these discrepancies.
An Euler-Based Throughflow Approach for Centrifugal Compressors – Part B: Experimental Investigations and Validation
Authors: Doerr Tobias , Yildiz Attilla , Dolle Bastian , Brillert Dieter 
Published: October 2022

Abstract
For turbomachinery design, manufacturers today need fast tools to predict the performance of an aerodynamic design with good accuracy. However, CFD tools are often cumbersome in terms of computation time and licensing costs for commercial solvers.
In this context, a quasi-three-dimensional solver, called tFlow, for centrifugal compressors is presented in Part A of this paper. To validate and calibrate the model, an experimental test rig is developed and presented in this paper. The setup consists of a single-stage centrifugal compressor with a shrouded impeller providing a pressure ratio up to 1.85. On the pressure side, the diffuser is followed by a volute and a throttle to capture the whole speed characteristic between surge and choke. Thermodynamic data, such as pressure and temperature upstream and downstream of the compressor, are recorded as well as torque and rotational speed at the shaft coupling. In addition, the test rig can also be used to investigate the effects of wet compression. For this purpose, a spray nozzle can be installed in front of the impeller’s bell mouth. In order to investigate the influence of temperatures on evaporation rates, a preheater in front of the compressor section is installed to heat the air up to temperatures of 80 °C.
In this paper, dry results are shown for inlet temperatures of 22, 30, 40 and 50 °C. To compare the characteristics at different preheated conditions, reduced rotational speed and air mass flow rate are kept constant. These resulting performance maps are in good agreement between each case. The numerical results of Part A are validated by the experimental data herein.
Machine-Learning Clustering Methods Applied to Detection of Noise Sources in Low-Speed Axial Fan
Authors: Tieghi Lorenzo , Becker Stefan , Corsini Alessandro , Delibra Giovanni , Schoder Stefan , Czwielong Felix 
Published: October 2022

Abstract
The integration of rotating machineries in human-populated environments requires to limit noise emissions, with multiple aspects impacting on control of amplitude and frequency of the acoustic signature. This is a key issue to address and when combined with compliance of minimum efficiency grades, further complicates the design of axial fans. The aim of this research is to assess the capability of unsupervised learning techniques in unveiling the mechanisms that concur to the sound generation process in axial fans starting from high-fidelity simulations. To this aim, a numerical dataset was generated by means of LES simulation of a low-speed axial fan. The data set is enriched with sound source computed solving a-posteriori the perturbed convective wave equation (PCWE). First, the instantaneous flow features are associated to the sound sources through correlation matrices and then projected on latent basis to highlight the features with the highest importance. This analysis in also carried out on a reduced dataset, derived by considering two surfaces at 50% and 95% of the blade span. The sampled features on the surfaces are then exploited to train three cluster algorithms based on partitional, density and Gaussian criteria. The cluster algorithms are optimized and their results are compared, with the Gaussian Mixture one demonstrating the highest similarity (&gt; 80%). The derived clusters are analyzed, and the role of statistical distribution of velocity and pressure gradients is underlined. This suggests that design choices that affect these aspects may be beneficial to control the generation of noise sources.
Experimental Flow Investigation Inside an Axial Compressor With Active Flow Control
Authors: Moubogha Joseph Moubogha , Joseph Pierric , Roussette Olivier , Dazin Antoine 
Published: October 2022

Abstract
This paper describes the experimental study of the flow behavior in a rotor blade channel of an axial compressor equipped with an Active Flow Control (AFC) system using Particle Image Velocimetry. The AFC system consists of 40 actuators connected to an auxiliary supply pressure system. It is used to extend the stable operating range and to improve the performance of the compressor. The system is able to generate high speed jets blowing just at the tip of the rotor blades. PIV data are obtained at three radial positions (at 18%, 51% and 79% of the blade height) in the inter-blade channel region. The PIV results are discussed to analyze the effect of the control system on the compressor internal flows.
Numerical Prediction of Heat Transfer Coefficient and Adiabatic Effectiveness on a Nozzle Guide Vane With Representative Combustor Outflow
Authors: Tomasello Stella Grazia , Andreini Antonio , Bacci Tommaso , Facchini Bruno , Cubeda Simone , Andrei Luca 
Published: October 2022

Abstract
The employment of lean-premix combustors in modern gas turbines allows to reduce NOx emissions by controlling the flame temperature at the expense of highly unsteady and strongly non-uniform flow fields which are necessary to stabilize the flame. This highly complex swirled flow field characterized by evident temperature distortions alters the aerodynamics and heat transfer in the first high pressure turbine stator with potential detrimental consequences on engine life and efficiency. From a numerical point of view, the mutual combustor-turbine interaction has been studied by using standard turbulence modeling approaches, as commonly employed during the design phase, even if more advanced scale-resolving methods have been proven more reliable and benchmarked against various experimental findings.
From the experimental perspective, film-cooling adiabatic effectiveness and heat transfer coefficient (HTC) measurements on the external surface of the nozzle guide vanes, in the presence of representative combustor outflow characteristics, are not common since the relevant temperature distortions that are present make such kind of measurements really challenging to perform. For this reason, very limited assessment of such approaches regarding this aspect is available in literature.
In this study, an experimental test case with a combustor simulator and a nozzle cascade, where both adiabatic effectiveness and HTC measurements have been carried out, is investigated by carrying out a systematic computational study, through RANS calculations of the combustor-cascade integrated domain. The film cooling system performance has been predicted by meshing the whole vane internal cooling system, while the heat transfer coefficient is calculated using the conventional two-point method, normally adopted for heat transfer calculations in gas turbines.
The comparison between numerical predictions and experimental results was exploited to assess the capability of traditional modeling approaches in the characterization of both adiabatic effectiveness and heat transfer coefficient. This evaluation represents an effective means to assess if conventional/industrial approaches can be reliably used, when representative and highly unsteady combustor outflows are considered, or advanced and more time-consuming methods shall be adopted.
Additively Manufactured Guide Vane With Integral Measurement System for Validation on Engine
Authors: Naryzhnyy Oleg , Lindbaeck Martin , Laletin Petr , Rotar Alexander 
Published: October 2022

Abstract
Thermal validation of gas turbine components is one of the key activities performed for engine characteristics evaluation and verification of a newly developed product. There are several standard thermal validation methods: thermal paint, thermal crystals and thermocouples (TC). However, measurement results from all the above-mentioned techniques are affected by the design of the component or limited by the technological conditions of the application.
This article is related to the specific part design applied by additive manufacturing (AM) for the first-stage gas turbine vane. Validation is performed by thermocouple measurement technique. Thermocouple gauges are instrumented inside the additively manufactured turbine vane without any negative impacts on the part cooling system or key interfaces, such as hot gas surfaces, and as a result without impact on the operation of the entire turbine component.
Moreover, since guide vanes were covered with thermal barrier coating (TBC), and the metal temperature was recorded throughout the entire period of operation, it became possible to capture and analyze the effect of aging of the TBC. It is well known that the properties of TBC change over time and bring uncertainty into the component thermal state. This is due to the fact that the TBC conductivity value depends on the exposure time and the exposure temperature.
Thermal validation work shown in this paper was performed in frame of new AM product development and supports all stages of product development process in Siemens Energy.
Mixing Mechanism of Multi-Scale Flow in Tip Region of Turbine Rotor
Authors: Huang Lin , Zou Zhengping 
Published: October 2022

Abstract
The tip leakage loss of freestanding turbine rotor with transonic flow conditions is one of the important sources of the internal loss of high-pressure turbine. It mainly includes the internal loss of the tip and the mixing loss of the leakage flow and the main flow. The latter is the main contributor of the tip leakage loss. The mixing between the leakage flow and mainstream flow is a complex physical process, which contains abundant multi-scale flow structures. Therefore, it is of great significance to understand the mixing mechanism of multi-scale flow in order to accurately evaluate the tip leakage loss and improve the aerodynamic performance of the turbine. In the present, the high-precision flow field in the tip region is obtained by Detached Eddy Simulation, and the multi-scale flow are decomposed by Kolmogorov Spectrum Consistent Optimization (KoSCO). Furthermore, the mixing coefficient is defined by combining Lagrange and Euler method. The contribution and physical mechanism of the local multi-scale flow to the mixing is studied carefully. Finally, the mixing coefficient is associated with the velocity field. The results show that the KoSCO method in this paper can effectively induce the multi-scale flow structure in the tip region of turbine rotor. The mixing coefficient defined in this paper can effectively evaluate the difference of the contribution of different scale flows to mixing. The contribution of different scale flows to mixing is scale dependent. The mixing coefficient decreases with the decrease of flow scale. However, when the flow scale is smaller than a specific value, the mixing coefficient is almost the same. The physical mechanism of flow mixing of different scale flow is quite different. The transport and diffusion dominate mixing process in large-scale flow and small-scale flow, respectively. Specially, both transport and diffusion impact the mixing process. The relationship between the mixing coefficient and the velocity gradient is found, and the correlation formula between the mixing coefficient and the velocity field gradient is established to evaluate the mixing strength.
Methanol Production by a Chemical Looping Cycle Using Blast Furnace Gases
Authors: Palone Orlando , Hoxha Arian , Gagliardi Gabriele Guglielmo , Di Gruttola Francesca , Borello Domenico 
Published: October 2022

Abstract
Steel mills are responsible for high direct CO2 emissions. To mitigate climate changes, carbon capture and utilization strategies (CCU) aiming at neutralizing such emissions should be employed. Currently, the most widespread technologies for carbon capture (CC) are represented by chemical/physical absorption, adsorption, membrane separation, calcium looping cycles (CaL). One promising pathway for carbon capture and utilization (CCU) is represented by the coupling of chemical looping cycles with liquid fuel synthesis processes, such as methanol synthesis. Methanol is an interesting low-cost fuel for gas turbines engines, due to its potential reduction of NOx and particulate emissions along with the absence of SO2 emissions. Furthermore, being one promising solution to store excess power production from renewables, its availability is expected to increase significantly with the years. In this work, methanol production from the syngas generated by a three-reactors chemical looping process (TRCL) is investigated by mass and energy balances. The TRCL cycle is composed by a reducer reactor, where Fe2O3 is reduced to FeO by an endothermic reaction occurring at high temperatures and promoted by biogenic carbon; an oxidizer reactor, where FeO reacts exothermically with a gas stream composed of CO2 and H2O in order to produce a syngas (CO + H2); a fuel reactor, where the non-reacted FeO is oxidized to Fe3O4 and subsequently the whole amount of Fe3O4 is regenerated to Fe2O3 by the interaction with ambient air. The produced syngas is then sent to a methanol synthesis plant modelled with the Aspen Plus software. Several syngas compositions, deriving from different oxidizer’s inlet CO2/H2O molar fractions, are investigated and the resulting methanol production rates are compared. A WGS unit is located at the plant inlet in order to increase the H2 molar fraction in the feed stream. Results indicate that methanol production is almost equal in all investigated configuration and amounts to about 0.35 ton/h. From an energy standpoint, global heating/cooling duty is almost equal in all cases, while the electric power required is greater for higher hydrogen contents in the syngas. However, the case with high H2 content (0.75 in molar fraction) is characterized by the greatest methanol yield (12.6%), carbon efficiency (23%) and a limited feed over recirculation ratio, thus representing the most indicated configuration among the investigated ones.
Numerical Investigation of a Coupled Blow-Off/Flashback Process in a High-Pressure Lean-Burn Combustor
Authors: Soli Alessandro , Langella Ivan 
Published: October 2022

Abstract
Large eddy simulation is used to investigate the flashback mechanism caused by the combustion-induced vortex breakdown (CIVB) in a high-pressure lean-burn annular combustor with lean direct injection of kerosene. A single sector of the geometry, including a central pilot flame surrounded by a main flame, is simulated at take-off conditions. A previously-developed flamelet-based approach is used to model turbulence-combustion interactions due to its relatively low cost, allowing to simulate a sufficiently long time window. In stable operations, the flame stabilises in an M-shape configuration and a periodic movement of the pilot jet, with the corresponding formation of a small recirculation bubble, is observed. Flashback is then observed, with the flame accelerating upstream towards the injector as already described in other studies. This LES, however, reveals a precursor partial blow-out of the main flame induced by a cluster of vortices appearing in the outer recirculation region. The combined effect of vortices and sudden quenching alters the mixing level close to the injector, causing first the main, then the pilot flame, to accelerate upstream and initiate the CIVB cycle before the quenched region can re-ignite. Main and pilot flames partly extinguish as they cross their respective fuel injection point, and re-ignition follows due to the remnants of the reaction in the pilot stream. The process is investigated in detail, discussing the causes of CIVB-driven flashback in realistic lean-burn systems.
High-Fidelity CFD Analysis of In-Serviced Shrouded High-Pressure Turbine Rotor Blades
Authors: Carta Mario , Ghisu Tiziano , Shahpar Shahrokh 
Published: October 2022

Abstract
In-service deterioration can lead to undesired shape variations on high-pressure turbine rotor blades. This can have a significant impact on efficiency, power generation and component life. Loss of power production from the high-pressure turbine rotor causes engine over-throttling to compensate for the lower performance. This will in turn worsen the operating conditions and ultimately reduce the life of the component. The aim of this study is to provide a high-fidelity flow simulation of in-serviced shrou ded High-Pressure Turbine (HPT) blades of a modern Jet Engine. Shape variations effects on the aerodynamic performance of several shrouded HPT blades with different number of in-service hours have been investigated. In order to establish a digital model of the shape variation, a novel reverse engineering procedure is carried out, to come up with a parametrized definition of each blade’s variations from nominal including any observable damage. The investigation is conducted by means of an in-house, full 3D steady-state RANS simulation of the flow around a series of damaged rotor blade geometries, which are obtained through high-resolution GOM scans. The analysis shows that the aerodynamic performance of the HPT rotor blades under investigation is primarily sensitive to shroud damage, which is found to account for efficiency losses often greater than 3%, and for more than 80% of the total performance loss. A secondary role on efficiency is found to be played by the blade shape deviation. A highly linear correlation is found between HPT stage efficiency and a combination of shroud damage parameters.
Computational Investigation of Using Emulsified Fuels in Heavy Duty Gas Turbines
Authors: Suleiman Baha , Selim Hatem , Dawood Alaaeldin , Khalidi Abdurrahman , K. Vasudevarao , Goldmeer Jeffrey , Al-Ahmadi Kamal , Al-Ghamdi Ibrahim , Badr Eid , Al-Gahatani Mohammed 
Published: October 2022

Abstract
Gas turbines operating on liquid fuels may produce higher NOx and soot emissions and may suffer from reduced combustion part durability, as compared to gas turbines operating on gaseous fuels. With some fuels, like diesel (aka light distillate), the NOx emissions increase is related to the liquid fuel spray atomization process, which plays a vital role in the combustion process.
A promising technology for enhancing fuel atomization in a combustor is water-fuel emulsion technology. Injecting a water-fuel emulsion into a gas turbine combustor may lead to favorable effects. Since fuel atomization should be enhanced, combustion should occur at lower local equivalence ratio values, thus reducing the creation of NOx and soot emissions. Moreover, the presence of water in the combustion mixture decreases the average temperature of the combusting mixture due to the high latent heat of vaporization of water, which in turn should reduce NOx.
In this study, a numerical investigation is conducted to quantify the impact of the water-fuel emulsion technology on gas turbine combustors operating on diesel fuel. The objective is to determine if NOx and soot emissions are improved, and if flame structure changes when the emulsion technology is utilized at different water to fuel ratios.