bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Detailed Modelling of Deposition on Superheater Tubes to Enhance Boiler Flexibility
Authors: Thanganadar Dhinesh , Simms Nigel , Patchigolla Kumar , Mori Stefano , Kulkarni Anand 
Published: October 2022

Abstract
Biomass cofiring in coal-fired power plants is a promising way to reduce CO2 emissions from existing coal plants. However, the changes in the fuel composition influence the ash deposition mechanisms on superheater tubes, therefore negatively impacting the boiler efficiency, as well as promoting corrosion which compromises the life of the boiler tubes. The continuous fluid flow combined with the ash particle trajectories has been simulated using a Eulerian-Lagrangian model. A novel alkali vapour condensation model has been added to the previous in-house powdery dry deposition model. This paper describes the modelling methodology applied and the in-house user-defined functions. This work analyses the deposition flux, and deposit profiles around the superheater tubes for the changes in four different boundary conditions namely 1) flue gas temperature, 2) tube metal surface temperature, 3) flue gas inlet velocity, and 4) alkali vapour concentration from the flue gas by performing a series of sensitivity studies., revealing that flue gas temperature variation primarily influences the mean ash deposition flux. The tube-tube interactions were analysed in detail by simulating three rows of tube banks containing a total of six tubes arranged in a staggered manner, and results show that row 2 encounters the highest ash deposition flux.
Unsteady Effects of Casing Treatment on Tip Flow Structures in a Subsonic Compressor Rotor
Authors: Chi Zhidong , Chu Wuli , Zhang Haoguang , Luo Bo 
Published: October 2022

Abstract
With the help of the dynamic mode decomposition (DMD) analysis, the unsteady effects of casing treatment on tip flow structures in a subsonic compressor rotor were numerically studied. Taking the change of casing treatment geometric parameters into account, the frequency characteristics and dynamic modes were compared and discussed, for further revealing the stability enhancement mechanism of casing treatment. At smooth casing, the mode analysis showed that the tip flow structures were dominated by high absolute mode values alternately emerging along passage streamwise, which is consistent with the evolution of tip leakage vortex (TLV), and the mode frequency is 0.42 BPF. After applying casing treatment, the unsteady characteristics of tip flow fields changed significantly. The mode analysis indicated that the tip flow structures were dominated by intermittent high-energy excitation, which was caused by suction and injection actions of casing treatment. As a result, the relative position of slot and rotor determined the flow features inside casing treatment slots, and an significant induced vortex structure varied in one mode period. By comparing the casing treatment configurations with different slot number, it could be found that the suction and injection effects of casing treatment were closely related to the dominant frequency brought by the slots. When the slot number was not adequate (less than 2 per passage), the excitation energy of suction and injection effects on tip flow field were limited. With the slot number increasing, the excitation energy raised gradually, so the stability enhancement brought by casing treatment was better. This paper demonstrated the effectiveness of DMD method on investigating the unsteady effects of slot-type casing treatment, giving a encouraging prospect for the application of DMD in the internal flow fields with passive control strategies.
Research on Particle Motion and Erosion Characteristics in the Blade Passage of Multistage Axial Compressors
Authors: Cai Liu-xi , He Yao , Hou Yan-fang , Li Yun , Wang Shun-sen , Mao Jing-ru 
Published: October 2022

Abstract
Aviation and ground compressors are susceptible to the erosion of hard particles in the sandy environment, leading to lower performance and shorter service life of the equipment. Although many studies have been performed on this topic, current literature mainly focused on the steady ideal operating conditions of compressors. In this paper, particle motion behavior and erosion characteristics in the blade passage of a 3.5-stage axial compressor under actual service environment are investigated with the RANS numerical simulation method systematically. By comparing the particle trajectories, erosion rate density and other indicators, effect of particle diameter, particle mass concentration, compressor speed and inlet conditions on erosion characteristics are explored in detail.
Results show that the value of erosion rate density on the blade pressure side is overall higher than the suction side. The erosion area and intensity of the rotors are generally more serious than stators, especially on the first rotor blade. With variation in particle size, particle diameter of 100 μm becomes the turning point to change the erosion trend of the blades. Moreover, the overall erosion rates increase linearly with increasing mass concentration of inhaled particles. However, its impact on the erosion position and morphology are not obvious.
When the compressor speed increases from 6050 rpm to 6650 rpm, the eroded mass of R1 increases by 10.7%, and the casing erosion rate increases about 11 times. Compared with the winter condition, the overall erosion rate in summer increases by 62%. The results of this paper will provide a technology basis for the prediction on particle erosion behavior and formulation of operation and maintenance programs for aero engines and ground gas turbines under the actual service environment.
MRI Investigations of Internal Blade Cooling Flow and CFD Optimization Through Data Matching
Authors: Wüstenhagen Carolin , Domnick Clemens , John Kristine , Bruschewski Martin , Grundmann Sven 
Published: October 2022

Abstract
The optimal turbulence model to be used in a CFD simulation varies depending on the application and the scientific question at hand. It is always a difficult task to predict which model best represents reality. This study focuses on the internal cooling system of a high-pressure turbine airfoil. It presents a CFD validation routine, which includes a data matching process with experimental data as well as global and local error metrics to quantify the differences between the experiment and CFD. The experimental data of the time-averaged three-dimensional velocity field is obtained with Magnetic Resonance Velocimetry (MRV). The airfoil in question is a second stage blade of a small industrial gas turbine, consisting of a three-pass internal cooling serpentine. The three-dimensional three-component MRV data is compared to CFD using the data matching process and the error metrics. The simulations are performed with the eddy-viscosity based turbulence model k-ω SST and the Reynolds-Stress SSG, and BSL-EARSM turbulence models. The results indicate local differences between the examined turbulence models and the MRV results. Referring to the global and local error quantities presented in the study, the BSL turbulence model is identified as the optimal turbulence model for this specific high-pressure turbine airfoil.
Experimental Investigation of an Aggressive S-Shaped Intermediate Compressor Duct
Authors: Kasper A. , Dygutsch T. , Grund S. , Beversdorff M. , Hakansson S. , Nicke E. , Lejon M. 
Published: October 2022

Abstract
Reducing the fuel consumption of airplanes is one of the main research topics of the aero industry. Due to this, the bypass ratio in modern aero engines is increasing and the radial offset between the low pressure compressor (LPC) and the high pressure compressor (HPC) is getting larger. Motivated by shortening the length of the duct between the LPC and HPC, called the intermediate compressor duct (ICD), a workgroup from DLR Institute of Propulsion Technology, MTU Aero Engines AG and GKN Aerospace set up a measurement series in the new DLR ring cascade wind tunnel, that simulates a shorter and therefore aero-dynamically more aggressive s-shaped ICD. The setup consists of a full annulus channel. It provides 60 swirler blades which simulate the last rotor of the LPC, 120 LPC outlet guide vanes (OGV), 10 struts and 30 HPC inlet guide vanes (IGV). The airfoil counts are generic counts proposed for validation. Behind the OGV, there is a bleed air outlet which can be varied between 3% and 35% of the mass flow. This paper describes the highly instrumented test rig and its measurement techniques. We are able to analyze the specific flow behavior as well as determine the main ICD-performance parameter. Seven different measurement planes are located between the mentioned blade rows. The total state and the velocity (absolute value and directions) are among others measured in the plane. For each task and measurement location the best suited measurement method is selected. These are mainly multi hole probes in the main measurements planes, L2F in narrow places. The tests are conducted at eight different operating points, varying in Mach number, Reynolds number, bleed rate, stagger angle of swirler and HPC IGV. The high number of measurements leads to a profound understanding of the behavior of the ICD. The resulting conclusion is that in spite of the reduced axial length the flow through the aggressive s-shape of the ICD no separation occurs and therefore the desired performance is achieved.
The Interaction of Main Stream Flow and Cavity Flows in Turbine Center Frames and Turbine Vane Frames
Authors: Merli Filippo , Hafizovic Asim , Krajnc Nicolas , Schien Malte , Peters Andreas , Heitmeir Franz , Göttlich Emil 
Published: October 2022

Abstract
This paper focuses on the interaction between the last high-pressure turbine (HPT) stage purge flows and the intermediate turbine duct (ITD) in modern turbofan engines. Two state-of-the-art ITD concepts are analyzed in this work: the Turbine Center Frame (TCF), which is supported by symmetric aerodynamic strut fairings and generally adopted in conventional dual-spool engines; the Turbine Vane Frame (TVF), which features turning struts and splitters and is typical of geared turbofan engines.
The measurement campaigns for both setups are carried out in the Transonic Test Turbine Facility (TTTF) at Graz University of Technology. The test vehicles consist of an HPT stage, the ITD (TCF or TVF) and the first LPT vane or blade row. The same HPT stage is used for both ducts, to enable consistent, engine-representative inlet conditions between the two solutions. All the HPT stator-rotor cavities are supplied with purge flows by a secondary air system, with independent mass flow and temperature control for each purge line. Five-hole probe data are acquired at the inlet and outlet sections of the ITDs, to characterize the aerodynamic flow field entering and leaving the duct. In addition to the pneumatic probe tests, seed gas concentration measurements are performed in the same planes, to track down the cavity air in the main stream and investigate its post-egress behavior. Finally, detailed post-test CFD results are presented to get additional insight into the flow phenomena developing through the strut passage.
The concentration effectiveness field at the inlet of the ducts shows the same characteristics in both configurations: the upstream purge flows are entrained in the HPT rotor secondary flows, leading to high-concentration spots that influence large portions of the channel. On the other side, the downstream purge air is confined into a thin concentration boundary layer in close proximity to the endwalls. The thickness of this boundary layer is affected by the circumferential pressure distribution from the HPT vanes and struts. At the TCF and TVF outlet, the upstream purge forms a circumferentially uninterrupted band, shaped by the secondary vortices evolving through the duct. The downstream purge interaction with such vortices leads to the formation of well-bounded lobes, whose size, count, and position are inherently related to the secondary structures and thus differ significantly between the two cases.
Unsupervised Feature Selection of Multi-Sensor SCADA Data in Horizontal Axis Wind Turbine Condition Monitoring
Authors: Miele Eric Stefan , Bonacina Fabrizio , Corsini Alessandro , Peruch Arianna , Cannarozzo Marco , Baldan Daniele , Pennisi Francesco 
Published: October 2022

Abstract
Wind power is one of the fastest-growing renewable energy sectors and is considered instrumental in the ongoing decarbonization process. However, wind turbines (WTs) present high operation and maintenance costs caused by inefficiencies and failures, leading to ever-increasing attention to effective Condition Monitoring (CM) strategies. Nowadays, modern WTs are integrated with sensor networks as part of the Supervisory Control and Data Acquisition (SCADA) system for supervision purposes. CM of wind farms through predictive models based on routinely collected SCADA data is envisaged as a viable mean of improving producibility by spotting operational inefficiencies. However, given the large number of variables monitored by SCADA systems, selecting those that contribute the most to the modelling of wind turbine health conditions is an open challenge. In this paper, we propose an unsupervised feature selection algorithm based on a novel multivariate Predictive Power Score (PPS). Unlike other approaches in literature that only consider relationships between pairs of variables, here we propose a Combined PPS (CPPS), where the information content of combinations of variables is considered for the prediction of one or more key parameters. The algorithm has been tested on 9 turbines belonging to the same wind farm located in the Italian territory. The results show that the proposed approach is more flexible and outperforms standard PPS.
Impact of Boundary Layer Ingestion on the Performance of Propeller Systems for Hybrid Electric Aircraft
Authors: Vouros Stavros , Hieb David , Kyprianidis Konstantinos 
Published: October 2022

Abstract
Boundary layer ingestion (BLI) has demonstrated potential for reduced thrust requirements, fuel consumption and environmental impact. An integrated approach is developed for evaluating the performance of propeller systems including BLI propulsors. A rotor model based on lifting-line theory is coupled with a high-order panel method and an integral boundary layer formulation. The impact of BLI on single propeller performance maps is quantified, with efficiencies up to 15% higher compared to uniform freestream conditions. A design space exploration framework is developed for the analysis of BLI effects at propeller system level, including the impact of weight differentiation, installation technology factors, thrust split between rotors and electrical transmission losses. A reference 19-passenger aircraft featuring two wing-mounter propellers is compared with a series of conceptual designs featuring an aft-fuselage BLI propeller and two wing-mounted propellers. A system-wide power saving coefficient is derived for the quantification of performance deltas between the conceptual and the reference system, including all propulsors. For systems with BLI aerodynamic benefits entirely negated by weight penalties, and electrical transmission losses of 10%, power savings of 1.5% are accrued. In a technologically advanced system with 2% reduced thrust requirements due to BLI and 3% transmission losses, power savings rise to 6.5%. This work reveals the anticipated performance potential and limitations of BLI propeller systems for the electrified future fleet.
Gas Turbine Combined Cycle Range Enhancer - Part 1: Cyber-Physical Setup
Authors: Reboli Tommaso , Ferrando Marco , Mantelli Luca , Gini Lorenzo , Sorce Alessandro , Garcia Jose , Guedez Rafael 
Published: October 2022

Abstract
Natural gas turbine combined cycles (GTCCs) are playing a fundamental role in the current energy transition phase towards sustainable power generation. The competitiveness of a GTCC in future electrical networks will thus be firmly related to its capability of successfully compensating the discontinuous power demands. This can be made possible by enhancing power generation flexibility and extending the operative range of the plant.
To achieve this goal, a test rig to investigate gas turbine inlet conditioning techniques was developed at the TPG laboratory of the University of Genoa, Italy. The plant is composed of three key hardware components: a micro gas turbine, a butane-based heat pump, and a phase-change material cold thermal energy storage system. The physical test-rig is virtually scaled up through a cyber-physical approach, to emulate a full scale integrated system.
The day-ahead schedule of the plant is determined by a high-level controller referring to the Italian energy market, considering fluctuations in power demands.
By using HP and TES, it is possible to control the mGT inlet air temperature and thus enhance the operational range of the plant optimizing the management of energy flows.
This article (Part 1) introduces the new experimental facility, the real-time bottoming cycle dynamic model, and the four-level control system that regulates the operation of the whole cyber-physical plant. The experimental campaign and the analysis of the system performance are presented in the Part 2.
Aerodynamic Assessment of Turbine Center Frames and Turbine Vane Frames Under the Influence of Purge Flows
Authors: Merli Filippo , Hafizovic Asim , Krajnc Nicolas , Schien Malte , Peters Andreas , Heitmeir Franz , Göttlich Emil 
Published: October 2022

Abstract
This paper investigates and compares the aerodynamics of two state-of-the-art configurations for the intermediate turbine duct (ITD) in a turbofan engine: the turbine center frame (TCF), which is typical of conventional dual-spool engines and features symmetric aerodynamic strut fairings, and the turbine vane frame (TVF), which integrates a set of turning struts and splitters directly in the duct, thus enabling length and weight benefits at engine system level.
The measurement data utilized for the analysis are a product of almost ten years of research at Graz University of Technology, involving multiple test campaigns with either TCF or TVF setups at consistent inlet conditions. The experimental tests are carried out in the Transonic Test Turbine Facility at the Institute of Thermal Turbomachinery and Machine Dynamics (Graz University of Technology). All test vehicles include not only the ITD (TCF or TVF), but also the last High-Pressure Turbine (HPT) stage and the first Low-Pressure Turbine (LPT) vane or blade row, in order to ensure engine-representative conditions at the duct inlet and outlet sections. For the same purpose, the test facility supplies all the stator-rotor cavities with purge air, with independent control of temperature and mass flows for each cavity.
The measurements are performed with pneumatic probes (five-hole probes, Kiel-head rakes) at the inlet and outlet of the ITDs, for three different HPT purge flow rates. The aerodynamic comparison between TCF and TVF setups is based on three key topics: duct inlet and outlet flow fields, duct total pressure losses and duct aerodynamic excitation on the LPT rotor blades. For each one of them, the sensitivity to HPT purge variation in both configurations is evaluated.
Due to the presence of turning struts and splitters inside the ITD, the TVF shows a more complex outlet flow field than the TCF, characterized by the interaction of HPT and TVF secondary phenomena. The TVF total pressure loss is less sensitive to purge variation compared to an advanced TCF design with high casing slope. While the weaker TVF loss derivative to HPT purge may provide off-design operating point benefits relative to a TCF-based engine, the increased level of flow nonuniformity at the TVF exit, distributed over a wider range of engine orders, represents a design challenge for the first-stage LPT rotor.
Aerodynamic Optimization of the SRV2 Radial Compressor Using an Adjoint-Based Optimization Method
Authors: Châtel Arnaud , Verstraete Tom 
Published: October 2022

Abstract
The design of radial compressors is typically a trade-off between peak performance at the design conditions and maintaining a good efficiency over a wide operating range. In the present paper, a gradient-based optimization of the well-known SRV2 radial compressor is presented. The optimization problem is formulated to increase the total-to-total efficiency of the compressor at peak efficiency while maintaining a wide operating range. To achieve an efficient optimization strategy, a gradient-based optimization method is used. Gradients of the RANS solver are obtained through the adjoint approach, leading to a computational cost that is almost independent of the degrees of freedom. A total of 44 design parameters are used to define a rich design space for the radial compressor impeller. A Sequential Quadratic Programming algorithm is used as optimizer and achieves an optimal design in less than 20 major iterations. The optimization process allows to significantly increase the efficiency of the SRV2 compressor at peak efficiency while maintaining the operating range of the baseline. Detailed analysis of the flow field in baseline and optimized compressors reveal the mechanisms which allow to improve the performance of the baseline compressor.
Development of Machine-Learnt Turbulence Closures for Wake Mixing Predictions in Low-Pressure Turbines
Authors: Frey Marioni Yuri , Adami Paolo , Vazquez Diaz Raul , Cassinelli Andrea , Sherwin Spencer , Montomoli Francesco 
Published: October 2022

Abstract
In this work, a DNS – Machine Learning (ML) framework is developed for low-pressure turbine (LPT) profiles to inform turbulence closures in Reynolds-Averaged Navier-Stokes (RANS) calculations. This is done by training the coeffcients of Explicit Algebraic Reynolds Stress Models (EARSM) with shallow artificial neural networks (ANN) as a function of input flow features. DNS data are generated with the incompressible Navier-Stokes solver in Nektar++ and validated against experiments. All calculations include moving bars upstream of the profile to capture the effect of incoming wakes. The resulting formulations are then implemented in the Rolls-Royce solver HYDRA and tested a posteriori. The aim is to improve mixing predictions in LPT wakes, compared to the baseline model, Wilcox’s k-ω SST, in terms of velocity profiles, turbulent kinetic energy (TKE) production and mixing losses. LPT calculations are run at Reynolds numbers spanning from ≈ 80k to ≈ 300k, to cover the range of aircraft engine applications. Models for the low and high Reynolds datasets are trained separately and a method is developed to merge the two together. The resulting model is tested on an intermediate Reynolds case. This process is followed for two computational domains: one starting downstream of the profile trailing edge and one including the last portion of the profile. Finally, the developed closures are tested on the entire profile, to confirm the validity of the improvements when the additional effect of transition is included in the simulation. This work explains the methodology used to develop ML-driven closures and shows how it is possible to combine models trained on different datasets.