bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation on a Baseline Shaped Film Cooling Hole: One- and Two-Dimensional Cooling Performance
Authors: Jin Yejia , Dong Xuezhi , Sun Wenchao , Tan Chunqing 
Published: August 2024

Abstract
A recently proposed baseline shaped film cooling hole is numerically investigated on a flat plate at four blowing ratios (M), 0.5, 1.0, 2.0 and 3.0 and two density ratios (DR), 1.2 and 1.5. Results show that there exists an optimal blowing ratio and a best coolant operating condition in the current simulation set. The cooling effectiveness shows insensitivity to changes in density ratio for the same blowing ratio no higher than 1.0. A high density ratio effectively compensates for the negative impacts brought by a higher blowing ratio coolant than the optimal. It is also summarised that a velocity ratio (VR) around 1 should be a division point where the coolant flow behaviour differentiates and thus decides the cooling performance characteristics. Specifically, this paper proposes the idea of the quantification of two-dimensional film cooling performance, through three additional parameters: area-averaged adiabatic cooling effectiveness, standard deviation of adiabatic cooling effectiveness distribution and a defined distortion factor measuring the uniformity of adiabatic cooling effectiveness distribution. Different conclusions concerning the optimal coolant operating condition are drawn based on whether these two-dimensional cooling performance parameters or the commonly employed one-dimensional parameters, centreline and lateral-averaged adiabatic cooling effectiveness, are applied for evaluation. When using one-dimensional parameters, the DR = 1.5 M = 2.0 case is the best coolant operating condition, while using the two-dimensional parameters, the optimal condition changes to DR = 1.5 M = 1.0 and the optimal blowing ratio also changes from 2.0 to 1.0. Besides, the DR = 1.2 M = 3.0 case becomes the worst cooling performance working condition instead of the two M = 0.5 cases. In addition, VR is found to better scale and predict area-averaged cooling effectiveness. Some new information on the uniformity and the variation level of cooling effectiveness distribution under various coolant operating conditions is also revealed. Visualisation of the flow field structures shows that the two-dimensional cooling performance is decided by the offsetting results of the negative and positive influences from the counter-rotating vortex development in lateral, spanwise and streamwise directions.
Flow and Heat Transfer in Rotating Compressor Cavities With Inverted Shroud-Throughflow Temperature Differences
Authors: Pernak Mikolaj J. , Nicholas Tom E. W. , Carnevale Mauro , Lock Gary D. , Tang Hui , Scobie James A. 
Published: August 2024

Abstract
In an aero-engine compressor, co-rotating discs form cavities that interact with an axial throughflow of secondary air at low radius. In the high-pressure (HP) compressor the shroud is hotter than the throughflow (directed downstream to the turbine) and the radial temperature gradient creates buoyancy-induced flow at Grashof numbers ∼ 1013. Such flows can be unstable and typically take the form of counter-rotating vortex pairs separated by radial hot and cold plumes. However, in low pressure (LP) and intermediate pressure (IP) compressors the secondary air is directed upstream. In this inverse scenario, the axial throughflow is hotter than the compressor discs, reversing the disc temperature gradient and eliminating the fundamental driver for buoyancy. Despite its practical application and importance, this inverse scenario has not been previously investigated. The University of Bath Compressor Cavity Rig has been uniquely designed to simulate such flows, measuring temperature and unsteady pressure in the frame of reference of the rotating discs. Bayesian and spectral analysis have determined the radial distribution of disc heat flux, as well as the asymmetry of the rotating vortex structures and their slip relative to the discs. Unexpectedly, the new data reveal the flow structure in cavities with positive and inverted temperature differences are fundamentally similar (albeit with reversed radial-temperature profiles). Isothermal cases identified a critical Rossby number (Ro), above which the flow structure in the cavity was dominated by a toroidal vortex. At sub-critical Ro, the flow structure for the inverted temperature gradient continued to be governed by buoyancy due to disc heat transfer. Momentum exchange with the axial throughflow and the gradient of circumferential pressure combine to vary the slip and vortex symmetry. This paper provides the first data and analysis of flow and heat transfer during inverse throughflow conditions in LP and IP compressors. The new insights are of importance for the determination of the thermal stresses in discs, engine life, compressor blade clearance and efficiency.
The Impact of Different Equilibrium Hypothesis on the Non-Linear Response of Bladed Disks
Authors: Zara Gianmarco , Berruti Teresa Maria , Zucca Stefano 
Published: August 2024

Abstract
Underplatform dampers (UPDs) are widely used in bladed disks to mitigate blades’ vibration amplitude. Such devices introduce localized nonlinearities, whose modelling requires nonlinear solution techniques. When the Harmonic Balance Method (HBM) is used to compute the nonlinear forced response of blades with UPDs, two different implementations are available: i) the uncoupled approach, where the static equilibrium is determined in advance and used as input to determine the dynamic equilibrium; ii) the coupled approach, where the static and dynamic equilibria are determined simultaneously. A common issue for both approaches is the variability in the static tangential contact forces, when the Coulomb friction model is used, that can result in multiple static equilibria and in multiple vibration levels. In this paper, the two approaches are used to determine the variability in the response levels of blades with UPDs and results are compared and discussed. Due to the large computation times associated with optimization algorithms implemented to compute the response limits, lumped parameter models are used, nevertheless the main findings of the paper can be considered general. In particular, results show that the coupled approach systematically overestimates the uncertainty with respect to the coupled approach and that UPDs geometry affects the range of variability of the response.
Development and Application of a High-Fidelity Numerical Tool for Dynamic Analysis of Bladed Disc Systems With Underplatform Dampers in Aircraft Engine Turbines
Authors: Tüfekci Mertol 
Published: August 2024

Abstract
This study presents VIBRANT: VIbration BehaviouR ANalysis Tool, a numerical tool developed for analysing the dynamic behaviour of complicated mechanical systems. The tool uses Python and Abaqus, employing time-marching algorithms to perform individual time domain simulations under harmonic excitation of certain frequencies until a steady state is reached to predict frequency domain behaviour. Hence, each monoharmonic excitation can be performed independently; the tool can parallelise the computations to shorten the computational time. This software enables the handling of various systems modelled by Abaqus, adeptly addressing numerous nonlinearities and conditions, expanding the capabilities of the software significantly. Properties of interest are measured for each frequency step of the simulation set. To validate and illustrate the capabilities of VIBRANT, two examples are presented. The first example is a beam with a dry friction contact element attached, and the second is a bladed disc system with underplatform dampers in aircraft engine turbines. Parametric studies evaluate the influence of the variation of parameters, such as excitation amplitudes and coefficient of friction, on the system’s dynamics. This research extends the scope of computational modelling in mechanical and aerospace engineering and provides a foundational tool that can be implemented to validate future aircraft engine designs.
Passage Secondary Flow Effects on Turbine Endwall Discrete Hole Film Cooling - A Review With Unique New Evidence
Authors: Chen Ting-Wei , Stinson Matthew , Simon Terrence 
Published: August 2024

Abstract
Film cooling effectiveness measurement results for gas turbine endwalls are discussed with emphasis on the effects that complex near-endwall flows in the passage have on them. The complexity comes from the secondary flows naturally occurring in a turbine passage. Important is their influence on coolant migration and film cooling effectiveness distributions downstream of coolant injection. Film cooling holes are typically distributed over the upstream portion of the endwall surface or over the entire surface in an attempt for full coverage.
Endwall surface wall shear fields documented in the literature and the hole pattern design establish the angle between the near-wall flow approaching a selected coolant hole and the axis of the corresponding hole. Often, shear field data are not available; also, downstream injection would affect the shear field. Thus, approach flow directions can accurately be applied to only the most upstream rows of holes (particularly, upstream of any coolant injection).
Measurements of coolant coverage with discrete hole injection show migration of coolant on the endwall as it is affected by the momentum of injection, the passage main flow direction, and the effects of vortices in the vicinity of each hole. The latter provide some evidence regarding the effect of vortices near the endwall on coolant migration, giving a valuable description of vortex effects.
Results from recent studies in the literature that show interactions of emerging coolant flows and nearby vortices are applied to develop a description of the effects of passage vortices and other secondary flows on endwall coolant migration. One example is the discrete hole located under a vortex residing near the passage entrance where ejected coolant is swept by the vortex away from the endwall resulting in low local values of surface effectiveness. This leaves the upstream pressure and suction surfaces difficult regions to provide coolant coverage by discrete hole injection.
Cases discussed herein have no or low injection upstream of the passage inlet. Studies with high levels of injection upstream of the inlet (high ratios of passage inlet momentum flow near the endwall to passage average momentum flow) are not discussed herein. Such cases would have strong injection along the endwall immediately upstream of the passage inlet and, thus, would have a different passage secondary flow pattern, not discussed herein. Such a pattern is discussed in [21] as the “impingement vortex.”
Deep Learning Based Crack Detection in Inhomogeneous X-Ray Images for High Pressure Turbine Blades in Aviation
Authors: Kuhlgatz Timo , Ihler Sontje , Bonhage Marius , Seel Thomas 
Published: August 2024

Abstract
To ensure safety in aviation, there are stringent requirements for aircraft components, not only in design and manufacturing but also their maintenance. For economic reasons, the maintenance process is intended to be as efficient as possible while still meeting required safety standards. The increase in automation level contributes to enhancing the economic efficiency of the maintenance process. A highly time-consuming step involves the manual assessment of X-ray images. Advances in deep learning algorithms suggest a promising prospect for employing these algorithms to automatically inspect X-ray images. This paper introduces a deep learning-based approach to enhance the level of automation in the inspection of X-ray images of high-pressure turbine blades by automatically detecting the presence of internal axial cracks. We encountered challenges posed by the heterogeneous X-ray images with very small and variable damage patterns, along with the issue of limited available data. To address these challenges, we applied damage mapping to define a region of interest and used the concept of transfer learning. Three different model architectures of deep neural networks (Resnet18, Inception-V3 and Densenet161) were compared, and it is demonstrated that all three are well-suited (average AUPRC &gt; 0.95 and average F2-Score &gt; 0.93) for our task. We are therefore able to help increase the degree of automation of the HPT blade X-rays’ inspection process and thus make the maintenance process more efficient.
Experimental Characterization of a Bladeless Air Compressor
Authors: Tiwari Ravi Nath , Reggio Federico , Ferrari Mario Luigi , De Paepe Ward , Traverso Alberto 
Published: August 2024

Abstract
The Tesla compressor is an innovative technology that offers a unique approach to fluid compression. Unlike traditional compressors that use rotating blades, bladeless compressors utilize closely spaced disks to create compression. The purpose of this article is to design a prototype Tesla air compressor with optimal design parameters and investigate the performance and loss characteristics based on numerical analysis and experimental demonstration. The prototype model has been numerically investigated at different rotational speeds and the results have been compared with those obtained in experiments. CFD simulations indicate that the rotor-only efficiency is greater than 90% at very low mass flow rates, while the coupling of the rotor and volute leads to a total-to-static efficiency of approximately 58 % (without losses) at 14 g/s. At a nominal mass flow of 4 g/s, the highest total to static pressure ratio would be around 1.27.
Experimental results indicate leakage losses greatly reduce net mass flow, while pressure ratio values are in good agreement with CFD predictions. During this experiment, a maximum isentropic efficiency of 32.4% is measured. Indeed, the prototype included ventilation and leakage losses, which were not modelled in the CFD analysis. It is remarkable that the compressor does not show any unstable behavior down to zero mass flow (closed valve test), where the CFD and the experiment show consistent pressure ratios. An estimation of the losses from end wall friction and leakage flow is carried out using numerical simulations at different exit radial clearances. Increasing radial clearance results in an increase in leakage and end wall power loss, the latter being driven mainly by the axial clearance with the casing, which remained unchanged. To minimize leakage, a Teflon ring has been used as a first measure. Numerical calculations have indicated that the leakage rate is approximately 6 g/s at design speed. A brush seal-type solution can improve the sealing system to reduce leakage.
Experimental Study on Friction Coefficient and Heat Transfer Characteristics of Elliptical Pin Fin Channel at Rotating State
Authors: Zhang Xuejiao , You Ruquan , Chen Wenbin , Li Haiwang 
Published: August 2024

Abstract
In this study, an elliptical pin-fins array is proposed to enhance the heat transfer coefficient (HTC) of turbine blade trailing edge channel. The friction coefficient (f) and HTC are obtained at the condition where inlet Reynolds number (Re) ranges from 10,000 to 70,000, rotation number (Ro) ranges from 0 to 1.0, temperature ratio (TR) ranges from 0.04 to 0.22, and Buoyancy number (Bo) ranges from 0 to 2.55. The streamlined design of the elliptical pin-fins allows the fluid to enter and pass through the channel more smoothly, thereby reducing flow disturbances at the inlet and minimizing the loss of heat transfer efficiency. Under low Re conditions, the pin-fins enhances fluid mixing, making the TR a significant factor affecting HTC. Under high Res, due to the complexity of fluid flow, the influence of the TR is relatively diminished. Similarly, under rotational conditions, the Coriolis force alters fluid flow direction and velocity distribution, increasing heat transfer intensity and making the impact of the TR more pronounced. The relationship between f and TR variation is not evident. The f is relatively small at lower Ro (0.1–0.3), then significantly increases as the Ro reaches 0.35. Subsequently, there is a slight fluctuation with the increase in Ro, exhibiting an overall trend of first decreasing and then increasing.
Centrifugal Compressor Preliminary Design Optimization for a Hydrogen Pipeline Compression Station
Authors: Jottrand Samuel , Hendrick Patrick 
Published: August 2024

Abstract
As the demand for hydrogen is expected to increase in the coming years, infrastructure requirements for the transport and storage of hydrogen should follow this trend to reduce its cost for users. For example, the European Hydrogen Backbone (EHB) represents a milestone toward a more accessible hydrogen network of pipelines. New compressors will be necessary to feed those pipelines, and for the volumes of hydrogen considered, only centrifugal compressors would be an adequate solution. But centrifugal compressors for hydrogen are a complex matter. Many technical issues are still under ongoing research, such as leakage through bearings and seals or materials problems due to hydrogen embrittlement.
This work introduces a method to optimize the preliminary design of a centrifugal compressor for hydrogen applications. This optimization is based on the variation of geometrical parameters of the impeller to minimize the energy required to power the compressor. This optimization can be applied for a steady state operation or for an unsteady set of operation. Furthermore, this optimization process of a centrifugal compressor stage extends to the optimization of multiple stages compressors, but also for the optimization of the arrangement in series and/or in parallel. This method is then applied to different case studies of a possible compression station pre-design for a hydrogen pipeline application. The compression station is tested under steady state conditions for a pressure ratio of 1.2 and a mass flow rate of 2.8 kg/s. Then it is tested on a transient flow, with variations of the mass flow rate of up to 10 percent.
Centrifugal Compressor Instrumentation for Developing an Anomaly Detection Method Using Vibration- and Acoustic Measurement Data
Authors: Linnemann Nick , Dolle Bastian , Brillert Dieter 
Published: August 2024

Abstract
In various industrial applications, acoustic measurement data is used for condition-based monitoring and predictive maintenance. These concepts enable the early detection of faulty machine behavior as well as the efficient planning of maintenance. Time-resolved measurements offer a promising approach for fault identification since every industrial process has a unique spectral fingerprint that allows for the differentiation between operating points as well as normal and faulty machine behavior. For this purpose, the acoustic reference state of the machine is determined and compared with measurement data obtained during operation to quantify the changes in the acoustic signal. In the field of turbomachinery, however, this method is not yet widely used due to the complexity of the process and the high overall noise level.
In this paper, a single-stage centrifugal compressor is equipped with high-frequency accelerometers and free-field microphones in addition to conventional process data instruments for anomaly detection. Time-resolved spectral evaluation methods and their advantages for gaining information about sequence of effects and distinguishing time-dependent phenomena are presented. Moreover, an approach for specifying a confidence interval to determine the degree of amplitude fluctuation in frequency domain between measurements is shown. In order to further verify the repeatability of the measurement result, the impact of material warming and compressor reassembly on the measurement data is examined statistically. Furthermore, a method for synchronizing time-resolved measurements in frequency domain is elaborated. Sensor positioning for optimal measurement results is discussed and the reference state with which future measurements will be compared with is determined using the above-mentioned techniques.
Assessment of Fatigue Interaction in Coated Superalloys
Authors: Moffat Andrew , Finley James M. , Alieninov Philipp , Meyer Christopher 
Published: August 2024

Abstract
Coatings are commonly used in industrial gas turbines to protect materials from oxidation when operating at high temperatures. However, coatings can be ignored when assessing the lives of critical components.
This study explores the influence of coatings on the fatigue lives of CMSX-4 single-crystal superalloy material via experiments and analysis. Experimental results show that coatings significantly reduce the fatigue life of the superalloy base material. Scanning electron microscopy of the failed specimens indicates that cracks initiate in the coating and propagate into the superalloy base material, leading to premature fracture.
Analysis results show that coating stresses are maximized at high temperatures and under compressive loading due to the dissimilar thermal expansion of the coating and the superalloy base material. Therefore, operation under these conditions leads to a higher likelihood of coating cracks. Analysis indicates notable stress concentrations occur in the base material in the region of coating cracks.
The Langer fatigue model is modified to consider the influence of coating cracks on fatigue life. The modified Langer model shows a general improvement in accuracy when predicting the fatigue lives of coated CMSX-4 material. These findings indicate that the influence of coatings should be considered when lifing critical gas turbine industrial components.