bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integrated Hybrid Air Foil-Magnetic Thrust Bearing (i-HFMTB) Part I: Preliminary Experimental Test for Rotordynamic Parameter Identification and Behavior With PD Control
Authors: Ha Yunseok , Kim Jungwan , Lee Yongbok 
Published: September 2023

Abstract
The selection of a thrust bearing for the operational reliability of turbomachinery is very important because it supports axial loads and influences the lateral vibration caused by the thrust collar tilt. A type of integrated hybrid air foil-magnetic thrust bearing (i-HFMTB) is hereby proposed to overcome the limitations of the air foil thrust bearing (AFTB) and the active magnetic thrust bearing (AMTB). The AFTB is composed of four top foils and three bump strips. It is spot-welded on a non-magnetic Inconel X-750 (relative permeability ≈ 1) pad so that it does not affect the magnetic flux when combined with AMTB. A slot is made so that the pad can be coupled to the outer pole of the AMTB, and the nominal air gap does not increase in the axial direction because of the inserted pad. i-HFMTB is used to design a different area to compensate for the slotted area and the nominal air gap. Moreover, it is unaffected by the flux imbalance owing to flux density differences because of the design. In the experiments involving the i-HFMTB, the test apparatus is supported by an active magnetic journal bearing (AMJB) to evaluate its performance. A PD (proportional and differential) feedback control system was applied to the i-HFMTB, and a Bode plot was obtained using an external excitation signal to determine the efficacy of the design. An experimental percentage overshoot method was used to validate the theoretical dynamic coefficient of the i-HFMTB. In addition, the effect of reducing the lateral vibration through the i-HFMTB at the critical speed of the rotor was experimentally determined. The proposed i-HFMTB can effectively control the rotor system.
PSP and LES Investigation on the Impact of Trench Depth on Flat Plate Film Cooling Through Shaped Holes
Authors: Abdeh Hamed , Barigozzi Giovanna , Zamiri Ali , Taek Chung Jin 
Published: September 2023

Abstract
To increase film cooling effectiveness levels downstream of film cooling holes, trenches manufactured in the thermal barrier coating can be adopted. The performance of this solution depends on the trench geometrical characteristics, namely its depth and width. A LES based numerical study has been performed at Korea University to investigate the effects of trench configuration on the thermal protection, resulting in a 22% increase in cooling performance compared to the reference case without a trench. The present paper reports the results of an experimental investigation carried out at Bergamo University on a Plexiglass flat plate model with a set of three fan-shaped holes incorporated into an existing wind tunnel, replicating the numerical setup. PSP technique was used to measure the adiabatic film cooling effectiveness. Besides the standard shaped hole case, the best and worst trench configurations coming from a DoE approach have been examined at various coolant to mainstream blowing ratios M in the range between 0.5 and 3. Cases at M = 1.5 were used to cross check the prediction capability of the LES numerical simulation for the selected trenched cases. PSP and LES result to be in good agreement, also with literature data. The high depth/low width trench was shown to give improved performance for M larger than 1.
Experimental Test on Centrifugal Pump Handling Mining Slurries
Authors: Zanini Nicola , Suman Alessio , Pinelli Michele 
Published: September 2023

Abstract
Non-Newtonian fluids are involved in many industrial processes, for example in food and Oil and Gas applications. Drilling operations require massive employment of drilling fluids, such as mixtures of water and bentonite, to maintain a cooling and lubricating environment. Centrifugal pumps are usually employed instead of positive displacement pumps in these applications due to the greater flow rates that can be provided. The viscosity of a non-Newtonian fluid varies with the imposed stress and rheology, and consequently, pumping this type of fluid can lead to a considerable variation in the pump performance. Both the pump head and particularly efficiency are adversely affected, and the performance of small pumps is impaired to the greatest extent. Previous experimental works with bentonite slurries reported that detrimental effects arise at low flow rates. Since most of the manufacturers test their pumps only with water, the selection of the appropriate slurry pump may result very challenging. As a consequence, oversized pumps are commonly installed. In this work, a small centrifugal pump handling mixtures of water and bentonite was tested on an on-purpose test loop. Different solid concentrations were considered during tests. A critical analysis was conducted to relate the pump performance drops with the slurry’s rheological properties.
Progress on the Complete and Low-NOx Combustion of Eco-Fuels Using a Thermo-Acoustically-Driven, Hydrogen-Powered Pilot Stage
Authors: Paulitsch Nina , Giuliani Fabrice , Hofer Andrea , Hofer Johannes , Andracher Lukas 
Published: September 2023

Abstract
Thermo-acoustic forcing of premixed lean combustion of conventional, carbon-based fuels can increase — if well chosen — the mixing rate, energy density in the flame due to its deformation, and the combustion efficiency leading to reductions in CO and NOx emissions [GT2017-64429]. It was shown for instance that the flame appears more robust versus lean blowout when thermo-acoustically excited, while simultaneous improvements in the combustion performance take place.
The combustion of hydrogen is a key element of the energy transition. However, premixed hydrogen combustion is not trivial. In premixed burners, high hydrogen content tends to flashback, forms high amounts of thermal NOx and triggers combustion instabilities. To address these challenges the thermo-acoustic forcing was already applied on lean premixed hydrogen combustion in a previous study [GT2022-80886]. It could be shown that thermo-acoustic excitation can be a significant driver in terms of flame position and stabilization.
This follow-up paper reports on the progress on atmospheric combustion experiments performed with lean premixed hydrogen in the kW range using a pulsation device of type siren for thermo-acoustic forcing. A test case is presented, including robust hydrogen flame stabilization against flashback when thermo-acoustically excited via a siren. More exactly, the flame is forced to stabilize further away from the injection, and the drive effect is well-controlled and reproducible. Two experiments performed with hydrogen and with a blend of hydrogen and ammonia, respectively, show a significant decrease in NO emissions when thermo-acoustically excited at a certain frequency. The specifics of the two atmospheric test rigs used and a developed hydrogen fast premixer, as well as the sensing methods, are described. All experimental results are presented and discussed in detail. Furthermore, the early findings of staged combustion experiments with ammonia using the hydrogen-powered pilot stage are shown. This contribution ends with the projection of this principle for greater scales in the MW range.
LES of Hydrogen-Enriched Methane Flames in a Lean-Burn Combustor With Axial Air Injection
Authors: Ferrante Gioele , Doodeman Lennard , Rao Arvind Gangoli , Langella Ivan 
Published: September 2023

Abstract
Large eddy simulation (LES) paradigms are employed to analyse the internal flow field of a lean premixed swirl-stabilized combustor with axial air injection at both non-reacting and reacting conditions, for a methane and a methane-hydrogen fuel mixture. The thickened flame combustion model (TFM) with detailed chemical kinetic mechanism is employed to simulate the flow. An adaptive mesh strategy is used to maximise the mesh resolution in the flame and boundary layer regions. The numerical results for the methane flame are firstly validated against experimental velocity measurements obtained via particle image velocimetry (PIV). Subsequently the LES is employed to simulate hydrogen-enriched methane flames by keeping the same output power in the combustor, in order to obtain insights on the flow behaviour when hydrogen is added, in terms of flame stability and emissions. A POD analysis reveals the presence of a precessing vortex core (PVC) in both reacting and non-reacting conditions, and how this PVC is affected by the reactants mixture is discussed in the paper. Moreover, the flame is observed to propagate upstream in the jet core despite the use of axial air injection, although flashback is not observed. In terms of emissions, significant reduction in CO and NOx is observed when adding the hydrogen to the reactants mixture despite the higher flame speed, the reason for are discussed in the paper.
Empirical Loss Model Optimization for the Prediction of Centrifugal Compressor Off-Design Performance
Authors: Howard Jonathon , Knudsen Peter , Engeda Abraham 
Published: September 2023

Abstract
Certain critical process applications, such as sub-atmospheric re-compression of cryogenic helium gas supporting particle physics and other scientific research, require operating multi-stage centrifugal compressors over a wide operating range. Customarily, turbomachines are designed for a specified design condition, but in these applications it is essential that these machines behave stably at off-steady-state-design conditions due to actual processes conditions and requirements that are inherently transient. Predictive algorithms have been developed which adopt various empirical correlations that estimate individual losses, thus allowing the compressor performance to be estimated. Some of these algorithms require complete knowledge of the impeller geometry to enable performance estimation at varying process conditions. However, often such complete knowledge may not available for differing reasons, although basic dimensions and geometry information is obtainable. The objective of the present study is to examine the numerous loss correlations available in open literature and evaluate the effects of each proposed correlation on performance prediction accuracy, thereby permitting an accurate and robust method to predict compressor performance over a wide range of operation. This paper recommends a methodology and set of loss correlations to accurately predict the pressure ratio and isentropic efficiency of centrifugal compressors operating over a wide range of off-design conditions.
A Novel Multiaxial Strain-Life Approach for Nickel-Base Superalloys
Authors: Irmak Firat , O’Nora Nathan , Gordon Ali P. 
Published: September 2023

Abstract
Nickel-base superalloys (NBSAs) are a group of materials that are extensively used in high-temperature applications such as aero and industrial gas turbine applications. These alloys can endure high temperatures and stresses for extended periods, they also exhibit excellent fatigue life and corrosion-resistant properties. Multiaxial states of stress and strain are very common in engineered parts. Components such as blades, crankshafts, pressure vessels, welded joints, heavy construction equipment, and the like experience external loads in multiple axes. Multiaxial approaches have been introduced to give improved predictions of fatigue life under complex states compared to what can be attained with uniaxial methods alone. A novel multiaxial strain-based life approach is developed in this study. Coffin-Manson and Basquin equation is modified to include multiaxial strain range values. In this approach, all the modeling parameters are obtained from uniaxial low-cycle fatigue (LCF) experiments. Generic modeling parameters are provided to ease the material characterization process of newly developed NBSAs. These parameters are optimized by a MATLAB function to achieve accurate fit. The goal is to reduce number of complex and costly multiaxial fatigue experiments for the material characterization process of NBSAs. A yield criterion, developed by the authors, is utilized to obtain effective strain values and to capture multiaxial state of strain. This criterion is a modified version of Hill’s yield approach. Certain parameters are added to include anisotropy of NBSA to the well-known Hill’s approach. The multiaxial strain life approach is exercised and compared with experimental data from various single crystal (SX) NBSAs. A comprehensive database is created to include all the available multiaxial fatigue data on NBSAs in literature.
Loss Reduction in an Ultra-High-Loaded Low Pressure Turbine Cascade by a Combined Flow Control Strategy
Authors: Xue Yapeng , Li Ziliang , Wu Yanhui 
Published: September 2023

Abstract
Modern low pressure turbines (LPT) always suffer from unexpected endwall flow losses due to the enhanced aerodynamic load. Thus, there is a demand for much more efficient methods to improve the endwall performance of modern LPT. In this paper, a novel flow control method (denoted by FILLET&NEC) which combines leading edge fillet configuration (denoted by FILLET) and non-axisymmetric endwall contouring (denoted by NEC) was applied to an ultra-high-loaded LPT cascade (denoted by REF, Zweifel = 1.59) to explore its flow control potential and underlying mechanisms for endwall secondary flow control. Numerical investigation verified by experiments was used to make comparisons of flow control effects in FILLET, NEC, and FILLET&NEC. Based on the coupled design of FILLET&NEC’s 5 design parameters, Latin hypercube sampling was used for parametric research to get the preferred model. The results show that the total pressure loss coefficient and non-dimensional secondary kinetic energy are reduced by 15.07% and 40.09%, respectively, with the application of FILLET&NEC. This coupled design significantly suppresses the development of passage vortex and wall vortex, while the overturning and underturning of outlet flow angle is reduced. The introduction of NEC effectively reduces the cross-passage pressure gradient near endwall, making up for FILLET’s shortcomings. Simultaneously, FILLET helps NEC decrease the size and strength of horseshoe vortex, improving the flow conditions in cascade passage. Coupled design FILLET&NEC fully highlights the advantages of FILLET and NEC, while avoids their own shortcomings when independently applied. This paper confirmed that the combined design of FILLET and NEC is effective in reducing the endwall secondary losses, providing a valuable reference for the coupled design applications and future advanced ultra-high-loaded LPT designs.
A Semi-Empirical Model for Conceptual Turbine Vane Cooling Design and Optimization
Authors: Schöffler Robin , Grunwitz Clemens , Brakmann Robin G. 
Published: September 2023

Abstract
Efficient turbine vane cooling designs are increasingly important to improve the thermal efficiency of gas turbines. Evaluating the performance of a cooling design requires the knowledge of the temperature distribution on the vane surface and the cooling air mass flow rate. The estimation of the vane temperature distribution is considered as a conjugate heat transfer problem, which usually requires a computationally intensive 3D CFD-FEM simulation. However, this approach is not suited for an early design phase, when the cooling design frequently changes. A simplified, yet physical approach is necessary to develop an initial cooling design, which can be used as a baseline for more detailed investigations. This paper presents a predictive model for turbine vane cooling and it’s integration into an optimization tool chain. The model uses a vane geometry model, the aerodynamic flow field and the coolant conditions from an in-house turbine design tool chain. The cooling geometry is divided into multiple interior sections with their own parameterizations, characterizing the cooling method and it’s geometric representation. Internal cooling, such as impingement or convective cooling, as well as external cooling, namely film cooling, is considered. Taking the material properties of the vane into account, the model calculates the temperature distribution on the vane surface and the coolant mass flow rate to identify critical hot spots and to evaluate a cooling concept. The capabilities of the model are demonstrated in an optimization process to improve the cooling design of a modern high pressure nozzle guide vane. Compared to a manually created cooling concept, the coolant mass flow rate was reduced by more than 20 % while simultaneously a more uniform metal temperature was achieved.
Analysis of Failure Forms of Bevel Gear, Shaft and Bearing Structure System Considering Multi-Mode Damage Accumulation
Authors: Han Xudong , Hong Jie , Chen Cheng , Chen Xueqi 
Published: September 2023

Abstract
During the working process, the structural system, including bevel gear, shaft and bearing, located in the front journal of the high pressure compressor of the aeroengine rotor is affected by various loads such as assembly load, centrifugal load, temperature load and meshing excitation, and it leads to different modes of interface damage, for example, wear, slip and fatigue. With the increase number of working cycles, different interface damage modes affect each other and damage gradually accumulates, which leads to the degradation of the mechanical properties of each component. Finally, the function of the weakest component is lost, resulting in the failure of the structural system. Consequently, the comprehensive influence of multiple failure forms caused by interface damage at different positions results in the failure of the structural system, where the damage position and the failure position are different, and the final failure form is uncertain. In this paper, a damage accumulation mechanical model considering multi-mode damage interaction is established for bevel gear, shaft and bearing structure system. And the damage-failure mechanical process of the structural system and its key influencing factors under complex environment loads are studied. The results showed that the failure forms of the structural system were closely related to the assembly and load characteristic parameters of the components. Therefore, considering the randomness of the initial assembly state and environment loads, the damage accumulation mechanical process and the final failure forms of the structural system have significant uncertainty.
Acoustic and Aerodynamic Performance of Serrated Leading Edges on the Bypass Outlet Guide Vanes
Authors: Cuciumita Cleopatra , Qin Ning , Shahpar Shahrokh , Namgoong Howoong 
Published: September 2023

Abstract
The reduction of noise for commercial aircraft has become an important challenge for engineers, with engine noise being one of the major contributors to the overall sound levels near airport. For modern turbofan engines, characterized by high bypass ratios, one of the main noise sources is the interaction between the turbulent rotor wake and the leading edge of the downstream outlet guide vanes. A passive noise control method that has been gaining interest in the research community is the use of serrated leading edges for the vanes. Studies done on flat plates and airfoils with serrated leading edges showed a reduction in airfoil turbulent flow interaction noise, with an increased benefit when increasing the serrations amplitude and the existence of an optimal wavelength. From an aerodynamic standpoint, some studies show that serrations delay stall, but with a cost in aerodynamic performance at design point. Very little data exists for assessing the acoustic benefits of serrations on the leading edge of outlet guide vanes, where the noise predictions require addressing both the broadband and tonal noise. Preliminary results indicate some noise reduction, but without quantifying the benefits against the serrations parameters. It is also unclear how the total pressure losses in the outlet guide vanes row are affected by the presence of serrations. In this paper, we report a parametric study based on leading edge serrations to investigate the effect of the amplitude and wavelength on noise levels, as well as on aerodynamic performance. The NASA source diagnostic test (SDT) fan with swept outlet guide vanes was used as the test case, being representative of a modern turbofan. The unsteady flow and radiated noise were computed using a hybrid Lattice-Boltzmann/very-Large-Eddy-Simulation model implemented in the PowerFlow computational fluid dynamics solver. The flow characteristics and the noise levels were validated for the datum geometry against existing experimental data. Correlations for the far-field overall sound pressure level and the total pressure loss coefficient were built in relation to the serration parameters and a discussion on the best combination of serrations amplitude and wavelength has been given. These correlations can be further used in a multidisciplinary optimisation process.
Dynamic Characterization of an Adaptive Film-Riding Seal
Authors: Bird Joshua , Keogh Patrick , Sangan Carl , Bowsher Aaron , Crudgington Peter , Scobie James 
Published: September 2023

Abstract
Shaft seals control the leakage of fluid between areas of high pressure and low pressure around rotating components inside turbomachinery. Static seals are often subject to damaging rubs with the shaft, caused by assembly misalignments and rotordynamic vibrations during operation. Adaptive seals aim to reduce leakage flows whilst minimizing wear. The Film Riding Pressure Actuated Leaf Seal (FRPALS) is one such design which utilizes a large installation clearance and is blown down towards the shaft under pressure.
This paper presents a numerical model which can be used in the design and development of adaptive shaft seals, validated by experimental data from the literature. The model uses a modified version of the Reynolds equation to predict the dynamic, frequency-dependent stiffness and damping coefficients of the fluid film. The dynamic coefficients have been solved for different operational clearances and pressure differences to generate coefficient maps. These maps have been incorporated into a blow down model with compliant mechanical leaves to predict the transient translational and angular displacement paths of the FRPALS when subject to an increasing pressure drop.
The blow down model has been compared against experimental measurements collected from a specially designed test facility for the characterization of shaft seal performance. Eddy current probes were used to measure the displacement paths of the FRPALS with the experimental values showing that the model can accurately predict the dynamic movement of the seal when subject to a pressure difference.