bluuebunny/crossref_metadata_2025 huggingface dataset:
Applications and Recent Developments of the Open-Source Computational Fluid Dynamics High-Fidelity Spectral/Hp Element Framework Nektar++ for Turbomachinery Configurations
Authors: Vivarelli Guglielmo , Isler João Anderson , Montomoli Francesco , Cantwell Chris , Sherwin Spencer J. , Frey-Marioni Yuri , Vazquez-Diaz Raul
Published: August 2024

Reynolds-Averaged-Navier-Stokes (RANS) modelling has had a significant amount of success within the industrial setting. In fact, such techniques are used on a daily basis to compute the flow field around a broad spectrum of geometries in very different conditions. To this end, many codes have now reached a good level of maturity in terms of capabilities and robustness.

However, there is a growing need for more efficient designs and higher performance. Therefore, aspects that are either challenging or impossible to capture by means of standard second-order steady discretisations are starting to become of interest. The computational hardware improvements seen over the decades and the persistent development of high-order numerical techniques, are allowing Implicit Large Eddy Simulation (iLES) if not Direct Numerical Simulation (DNS). These would allow accurate capturing of unsteady flow phenomena that can be critical to properly understand aspects such as flow separation, reattachment and transition to turbulence in components relevant to the turbomachinery community.

The advantage that high-order solvers, such as Nektar++, have over their standard second-order discretisation counterpart, relates to their ability to reach higher fidelity solutions with a saving in terms of number of degrees of freedom and therefore computational cost.

In this paper, a detailed introduction to the characteristics and features of the open-source high-order Nektar++ Computational Fluid Dynamics (CFD) framework will be given. An initial discussion of the numerics will be provided, therefore explaining the main features of this solver, followed by a set of different capabilities that are of interest to the turbomachinery community, such as meshing, incompressible and compressible solvers and post-processing.

Examples of successful deployment of these features to jet engine components will then be presented. To start, preliminary design components, such as flat plates with different loadings will be discussed. In these cases, the effects of adverse and favourable pressure gradients representative of those seen on modern engine intakes and fan blades, respectively, on boundary layers will be studied. Following, a description on low and high pressure turbine components will be provided with a discussion relating to the relevant experimental comparison. Finally, future developments and improvements to the code will be detailed, such as new schemes and interfaces to hardware enhancements, i.e. Graphical Processing Units.
Detection of Flow Induced Aerodynamic Performance Characteristics of Centrifugal Compressors Using Acoustic Measurements
Authors: Srinivasan Anand , Fowler Edward , Fuzak Corey , Kurz Rainer
Published: August 2024

Inline centrifugal compressors are prevalent in the oil & gas industry. The process conditions for these compressors necessitate operation over a range of inlet flows, suction & discharge pressures and speeds. In many instances, operation is at high pressures in excess of 200 bar. The aerodynamic performance characteristics vary as a function of the inlet flow. The head versus flow map depicts the operating range of the compressor, with typical operation near a flow condition located in the mid portion of the map (i.e., the design operating point or the best-efficiency point). Upstream or downstream demand can necessitate changes to the flow conditions during operation. As flow is throttled, the compressor approaches the surge line. The onset of reversal of flow near surge can trigger flow induced characteristics in the downstream piping, which can result in elevated non-synchronous vibrations on the shaft displacement probes. On the high flow side, choking of the flow triggers flow induced characteristics that often result in super-synchronous vibrations on the shaft probes. In this paper, the use of acoustic microphones as a tool to aid in detecting flow induced characteristics at various locations on a head-flow map in a high pressure environment are presented. The influence of vaned diffusers on the flow induced characteristics is also presented. Case studies are presented in this paper that illustrate the use of acoustic devices in detecting flow induced vibration characteristics for centrifugal compressors, both in low pressure and high pressure conditions.
Development of an Additively Manufactured Stationary Diffusion System for a Research Aeroengine Centrifugal Compressor
Authors: Clement Jack T. , Coon Adam T. , Key Nicole L.
Published: August 2024

This paper introduces the next generation of the Centrifugal Stage for Aerodynamic Research (CSTAR) facility at the Purdue University Compressor Research Lab. The research centrifugal compressor is designed with an additively manufactured stationary diffusion system which comprises a vaned diffuser, a turn-to-axial bend, and deswirler vanes. The dimensional accuracy and surface finish of the diffusion system has allowed for rapid prototyping of several iterative diffusion system designs and has allowed for configuration of in-situ pressure and temperature measurements to experimentally evaluate the aerodynamics and performance of centrifugal compressor diffusion systems. The diffusion system is manufactured from a commercially available stereolithography (SLA) resin, and the design of the parts is adapted to the constraints imposed by current technological and material limits of resin 3D printing. The implementation of additive manufacturing in the prototyping of the diffusion system has allowed for decreased cost and lead time while allowing rapid turnaround to generate experimental data. Performance data have verified the repeatability and temperature independence of the additively manufactured diffusion system through several design iterations. A survey of candidate materials for additively manufacturing these parts is also presented, and the tradeoffs of their material properties discussed.
An Optimization Method for Stiffness and Damping Mistuning Identification From Blade Tip Timing Data
Authors: Krizak Troy , Kurstak Eric , D’Souza Kiran
Published: August 2024

System identification of dynamic properties is of large interest in the turbomachinery industry to create more accurate computational models and more effective designs. Previous identification techniques were able to accurately capture the blade variability, known as mistuning, in the stiffness as well as the average damping of all the blades. Mistuning is vital to accurately identify and study because the symmetry of the system is broken and can lead to vibration localization and high amplitudes. In this work, a new method is proposed to not only capture the stiffness mistuning values, but also the blade-to-blade variability in damping. These damping mistuning values have been shown to have a significant effect on the dynamics of bladed disk systems. Incorporation of the damping mistuning into the computational model can be done utilizing an augmented component mode mistuning method with either structural or proportional damping. The mistuning values for this new identification method were compared to a well-established direct method and a previously studied optimization method. Blade responses were then found using a harmonic analysis and the newly identified mistuning values. These blade responses were then compared to experimental tip timing data from full scale rotating experiments. These comparisons show that the new model is able to better reproduce experimental data using computational models that incorporate both stiffness and damping mistuning values.
NASA HECC Geometry and Performance Review Part 2: Geometric Differences Between the As-Manufactured and Design-Intent Impeller Geometry and Their Effects on the Vaneless Diffuser Configuration Performance
Authors: Robles Vega Gregorio , Bosshart Alec J. , Ni Michael , Ni Ron-Ho , Harrison Herbert M. , Nguyen-Huynh Tammy
Published: August 2024

An investigation of the NASA High Efficiency Centrifugal Compressor (HECC) vaneless diffuser configuration was performed. This multipart investigation focused on validating the computational model against experimental data. The validated model was then used to explore the effects of observed geometric differences between the As-Manufactured and Design-Intent impellers. Lastly, the validated model was used for comparison against an experimental tip clearance study.

Part II of the investigation of the NASA HECC vaneless diffuser configuration focused on understanding the differences in geometry and performance between the As-Manufactured impeller and the Design-Intent impeller. This was achieved through comparison of the As-Manufactured HECC vaneless computational model, developed from the solid model of the impeller and validated in Part I, against a new model developed from the Design-Intent blade sections published in NASA/CR-2014-218114/Rev1. The 1D performance values showed that the As-Manufactured impeller underperformed compared to the Design-Intent for all four speedlines that were simulated. Further investigation of profiles, loading and contours showed consistent underperformance of the As-Manufactured relative to the Design-Intent. An investigation into the source of the performance differences led to the discovery of several significant variations in the impeller geometries. The differences that were observed can be summarized into four categories: fillets, trailing-edge exit radii variation, dissimilarity in the splitter leading-edge geometry and main blade thickness differences. The investigation then shifted its effort to quantify the performance effects caused by geometric differences. The investigation showed that out of the four geometric differences that were explored, the differences in the splitter blade had the largest impact. These differences most notably changed flow physics near the splitter leading edge, especially near the tip of the impeller.
Low Swirl Effect on Compact Spray and Combustion Systems Using Additive Manufactured Dual Airblast Injectors
Authors: Kang Yeonse , Ahn Jihwan , Hampp Fabian
Published: August 2024

Novel low swirl concepts provide a promising approach to ensure stable flame anchoring over an extensive operation condition range, necessary for optimising compact designs for liquid fuel combustors as used in hybrid aero-engine or micro gas turbines in terms of scalability and flexibility. The current study utilises seven different additive manufactured low swirler integrated into a dual airblast injection concept to delineate the influence of high momentum swirling air jet on spray atomization and combustion performance. The developed injector is designed for vane angles from zero to 45° for co- and counter-direction against the orientation of the liquid sheet ejected from the pre-filming pressure swirl injector. The spray atomization in swirl afflicted air jet is demonstrated by phase Doppler interferometry and shadowgraphy. The combustion process is analysed using OH*-chemiluminescence imaging and emission measurements. The results show that a circumferential gaseous flow acting on the wall-film amplifies the radial fuel penetration and atomization. The latter produces robust spray dispersion in response to variations of operational conditions. The effect of low swirl injection on combustion process of kerosene flames leads to a noticeably more compact and intensified heat release zone. In addition, non-monotonic decomposed mode energy with considerable NOx reduction is observed.
Data-Driven Turbulence Modeling for Film Cooling Heat Transport, Part I: Turbulent Heat Transport Property at Wide Flow Conditions
Authors: Zhang Zhen , Hu Kexin , Su Xinrong , Yuan Xin
Published: August 2024

Film cooling is an important cooling technique used in modern gas turbines and air engines. It is a typical jet-in-cross-flow problem, where the jet interacts with the mainstream, leading to complex vortex structures and turbulence properties. In this paper, the deviation between RANS and LES data and the turbulent heat transport of film cooling problems are focused. A data-driven framework based on the physics-informed neural network (PINN) is proposed and used to calculate the distribution of the turbulent Prandtl number (Prt) based on the RANS flow field and the LES temperature field. This Prt is the target of a turbulence heat transport model, and the distribution of this Prt is analyzed in a wide range of film cooling flow conditions. A series of film cooling problems are studied with the variation of the hole geometry, the mainstream Mach number, and the blowing ratio. Results show that the turbulent Prandtl number largely deviates from the default value of 0.85 in most CFD solvers in all flow conditions and different turbulence models also lead to different Prt values, which means the turbulent heat transport model of Prt should be turbulence-model-related.
Simulation Validation of a Coupled Blade-Shaft System Including Non-Linearity and Gravity Effects
Authors: Exposito Iker , Martinez Aja Angel , Price Matthew , Rix Andrew , Schwingshackl Christoph
Published: August 2024

A shaft-bladed-disk rotor configuration has been experimentally subjected to synchronous and asynchronous dynamic excitation using the test rig named Asynchronous Rotor Excitation System (ARES). This work covers validation of an advanced dynamic simulation of the complete system that is formed by this rotor supported on a static frame that provides non-axisymmetric support stiffness. Different sensors have been placed in this installation: displacement sensors at bearings and shaft, and strain gauges at blade roots to derive blade tip displacements. Comparison of test sensors with regard to simulation model results, under prescribed synchronous and asynchronous excitations has been performed, resulting in a very good matching of resonance frequencies and response magnitudes at bearings and shaft. Resultant modes have a significant degree of coupling between blades and shaft.

Gravity load dynamic excitation has been also simulated to match blade tip displacement measurements. Gravity load is a non-axisymmetric static load that promotes dynamic excitation: a rotor blade experiences gravity load as an alternating load due to blade rotation. This type of loading is designated as 0EO (zero engine order) in the stationary frame as it remains at zero frequency at all rotor speeds.

Blade root attachment to disks include non-linear contact effects that can be observed from blade tip displacements obtained from tests. Non-linear modelling of this blade root is also covered with a simplified model in order to explain observed behaviour during testing.

In aircraft engines, due to flexibility of rotor blades and disks, critical modes can be coupled modes of disks and blades with shafts and, also, with static parts. Correct simulation of the complete system should include rotors and static parts in a single model. Rotors should include all steady-state rotatory effects: stress stiffening, spin softening and gyroscopic effect. This advance dynamic simulation technique of these systems has been validated in ARES. Also, specific non-axisymmetric static load conditions at aircraft engines i.e. cross wind scenarios (like gravity) can promote relevant vibrations. This 0EO excitation conducts to a specific dynamic solution that has been also validated in ARES rig through gravity load scenario.
Exergy-Based Analysis of the NASA SDT Configuration
Authors: Boniface Jean-Christophe , Petropoulos Ilias , Berhouni Ilyès
Published: August 2024

In the continuation of ongoing works at ONERA, aiming at performing exergy-based analyses of steady numerical solutions corresponding to complex internal or external flows, this paper presents a first application to the performance investigation of the NASA SDT configuration. Different operating conditions at take-off rotational speed were considered in the analysis. Links between losses and their physical origins are clearly highlighted in exergy-based analyses, which provide decompositions between reversible/irreversible losses and between mechanical/thermal effects. Attention is given to the decomposition of irreversible losses due to shock waves, viscous and thermal effects. In addition, it is shown that drastically lowering the numerical dissipation by strongly increasing the accuracy of the space discretization does not have a significant impact on the exergy balance in terms of mechanical and thermocompressible exergy outflow components, but has non-negligible effects on the anergy generation characterizing irreversible losses.
Collaborative Design in Context for Whole Engine Mechanical Design
Authors: Wang Leran , Toal David , Anobile Alessandro , Stanley Felix
Published: August 2024

Decomposition is often required to make the design of complex mechanical systems tractable. However, often the resulting sub-systems are designed in isolation with little indication as to the impact of design decisions on system level performance. The following paper demonstrates the increased risk of rework resulting from the naive recombination of such seemingly optimal sub-systems and goes on to demonstrate two approaches which can potentially help. The first proposes the adoption of a design in context based approach, where sub-systems are aware of the potential impact of their decisions on the wider system. The second augments this approach with a system level coordination step employing a surrogate model. The performance of each strategy is demonstrated using a realistic whole engine mechanical model for an ultra high bypass ratio (UHBR) gas turbine as a case study. The design in context approach is demonstrated to considerably reduce the level of infeasibility at the system level, while including some system level coordination not only reduces the level of infeasibility but improves the quality of the final system design and the rate of convergence towards it.
Dissipation in Skewed Boundary Layers
Authors: Peacock Robert , Pullan Graham , Folk Masha
Published: August 2024

The entropy generation within a turbulent, collateral boundary layer is well understood and is characterised by a dissipation coefficient, Cd. However, it is common for the transverse pressure gradients in turbomachines to create highly skewed boundary layers, where the velocity varies in direction as well as magnitude. A combined experimental and high-fidelity computational approach is used to quantify the effect of skew on the dissipation coefficient for the first time. At a nominal condition of 14 degrees of skew and Reθ of 1000, the increase in dissipation coefficient is 20% as determined from direct numerical simulation, and 28% from experimental measurements, relative to the collateral boundary layer. Experimental data over a range of skew angles and Reθ values show that Cd increases approximately linearly with skew so that, at a skew of 25°, loss is 70% greater than in the collateral boundary layer. The implications for loss estimation are examined by evaluating boundary layer loss, in the Harrison turbine cascade, with and without the influence of skew on Cd. By accounting for the skew in the boundary layer, a new proposed model has been used to calculate the loss coefficient in the Harrison cascade to within 4% of the experimentally measured value.
Supersonic Convergent-Divergent Vaned Nozzles Design Algorithm and Respective Discharge Coefficient Model
Authors: Moroz Leonid , Burlaka Maksym , Frolov Borys , Dyzenko Tetiana
Published: August 2024

To continue the series of already published articles on supersonic drilled nozzles [GT2022-83387, GT2023-101760], this publication is devoted to another type of supersonic nozzles, which are formed by vanes providing an annular row of convergent-divergent supersonic channels. This type of supersonic vaned nozzles, as well as the drilled nozzles, are used in numerous high-loaded turbine applications. Published data on this type of nozzles and turbine stages with them have very limited information on both the design methodology and calculation methods and thus do not allow these data to be systematized and implemented into the turbine design and calculation tool. The work carried out in this direction includes all the algorithms and models required for the supersonic vaned nozzle design and calculations: (1) The design algorithm of a highly efficient supersonic vaned nozzle, (2) the discharge coefficient model, (3) loss model, (4) flow angle deviation model. In this article, we focus on design model (1) and discharge coefficient (2) items. A list of geometric parameters that uniquely determine the 3D geometry of the nozzle channel that is used in the design algorithm is discussed. The approaches to building convergent and divergent parts of the supersonic nozzle are elaborated. Besides, the model of the discharge coefficient through the critical section of the nozzle is described in detail. The developed discharge coefficient model demonstrated a maximal deviation of 0.6% and an average of 0.18% from CFD results in a wide range of configurations of the nozzle channel.
Operations Optimisation of a Gas-Lift Compression System Using a Digital-Twin Approach
Authors: Mucino Marco , Savage John
Published: August 2024

The Oil and Gas industry is facing complex challenges including spiralling exploration and development costs, aging assets, long lead times on equipment, shortage of skilled people, among others. As such, it is imperative existing assets are operated efficiently and properly maintained to maximise production. A typical approach to achieve this objective considers industry best practices, international standards, manufacturer recommendations and condition monitoring techniques such as oil analysis, vibration, thermography, ultrasound, etc.

However, the advent of Industry 4.0 has promoted the development and adoption of advanced techniques: a prominent example being the Digital-Twin concept. A Digital-Twin is a virtual model developed using advanced modelling and data handling techniques to replicate and predict the behaviour of individual equipment or entire production systems. A Digital-Twin approach can deliver predictive monitoring capabilities; analysis of complex systems; define solutions to operational issues; virtual testing and confirmation of proposed modifications; etc.

This paper presents the development of a Digital-Twin for troubleshooting and operations optimisation of a motor-driven three-stage gas-lift compression system with a long history of unstable operation, recurrent emergency shutdown events and low availability. The multidisciplinary approach includes analysis of the control system architecture, assessment of field instrumentation, data validation, performance benchmarking, dynamic modelling and off-line control system testing. A cost-effective solution with only minor software modifications was designed, tested and demonstrated before its implementation. The successful outcome of the project reduced the need for constant operator intervention, reduced emergency shutdown events, increased availability of the gas compression system from 86% to 98.2%, reduced gas imports, increased gas exports and enhanced oil production.
An Experimental Investigation of the Corner Separation Control in a Compressor Cascade Using Spatially Oscillating Jet
Authors: Yang Pengcheng , Chen Shaowen , Liu Guanyu , Wang Shiqi
Published: August 2024

In the present study, an actuator with the ability to generate spatially oscillating jets, known as the sweeping jet actuator (SJA), is employed to manage the corner separation in a CDA profile. Experiments were performed in a low-speed wind tunnel with an inflow Mach number of 0.23. Measurements using a five-hole probe, dynamic pressure sensors, and oil flow visualizations were carried out to get insight into the performance and physics of the flow field. SJA was integrated into the cascade endwall through 3D printing, with dimensions constrained within 15mm, and reaching a maximum operating frequency of approximately 1400Hz. Parameters such as axial injection location, jet momentum, and operating frequency were systematically investigated to determine the optimal active flow control strategy. The results show that the spatially sweeping jet significantly suppresses the migration of low-energy fluids on the endwall surface, leading to a reduction of more than 30% in the spanwise extent of corner separation and a 14.2% decrease in the integrated total pressure loss coefficient, with 0.13% of the cascade throughflow. The study of the influence of jet momentum on control effect indicates that the sweeping jet could enforce the low-energy fluids without a significant increase in mixing losses between jets and mainstream even at a large jet momentum, which is attributing to the rapid decay of the unsteady sweeping jet velocity in mainstream. The results highlight the superior characteristics of the SJA in managing the corner separation.
Performance of Heavily Loaded Textured Gas Foil Bearings Based on the Multigrid Method
Authors: Han Jiazhen , Zhang Guanghui , Xu Kefan , Gong Wenjie , Sun Wenlong , Huang Zhongwen
Published: August 2024

Surface texturing technology is a novel avenue for enhancing gas foil bearing performance. For the cases of heavily loaded foil bearing, the static equilibrium eccentricity ratio may exceed 1.0, even 4.0, which will result in poor convergence for the numerical algorithm. The introduction of textures and numerical calculations under heavy load conditions have heightened the complexity of the solution, and the multigrid method offers an efficient resolution to this challenge. This paper established the pressure governing equation considering the effects of gas rarefaction. The cumulative eccentricity method was applied to analyze the bearing’s behavior under heavy-load operating conditions. Additionally, the numerical solution efficiency of the direct, iterative, and multigrid methods was analyzed. Furthermore, the Newton-Raphson method and the perturbation method are utilized to determine the static and dynamic characteristics under large eccentricity conditions.

The results indicate that the multigrid method offers up to a 77% increase in computational efficiency compared to the direct solution method. The bearing exhibits maximum load capacity when the axial texture ratio is above 0.7 and the circumferential texture ratio is within the range of 0.3 to 0.4. As the eccentricity ratio increases from 0.1 to 4, the enhancing effect of surface texturing on load capacity decreases by 6.78%, while the friction-reduction effect increases by 4.25%. Furthermore, critical mass calculations indicate improved bearing stability with a large eccentricity. This study shows that suitable texture parameters effectively improve the bearing performance under heavy-load conditions, while the multigrid method can efficiently solve the above problems.
Analysis of Heat Transfer Within Buoyancy Dominated Rotating Cavities of H.P Compressors
Authors: Fazeli Seyed Mostafa , Kanjirakkad Vasudevan , Long Christopher
Published: August 2024

A detailed knowledge of the flow structure and the heat transfer within blade-disc cavities is required for designing safe and efficient aero-engine compressors with a useful operating range. This paper presents the results from temperature field measurements obtained from the Multiple Cavity test facility at the University of Sussex. This emulates part of the secondary air system in an aircraft engine high-pressure compressor. It comprises four externally heated disc-cavities and is supplied by a cool bore flow. The heat transfer is studied with the help of a finite-element method using measured temperatures as boundary conditions. A validated 2D steady-state heat conduction analysis methodology is presented. Results are presented for a range of values of Rossby number, rotational and axial Reynolds numbers and the buoyancy parameter. The curve-fit type that is best suited for the temperature boundary condition specification is established using an independent Ansys APDL based study. The sensitivity of the overall cavity heat transfer to major driving mechanisms has been described. The Monte-Carlo analysis is used to reveal how a ±0.5 K uncertainty in temperature affected the Nu estimation.
The Safety Design Method for the Rotor System With Fan Blade Off
Authors: Zhao Zhenyao , Zhang Dayi , Yang Cheng , Zhang Qicheng
Published: August 2024

A safety optimization design method for the rotor system with fan blade off is established by taking the time-varying parameters such as rotor speed and support stiffness as the optimization variables, and the vibration response at the key position of the rotor as the optimization objective. The reduction in the number of optimization objective functions is achieved through correlation analysis and influence rule analysis. The optimization problem of rotor system dynamics is addressed by employing finite element model and radial basis function response surface surrogate model, integrated with NSGA-II genetic algorithm. The results show that the optimization method based on the response surface surrogate model can greatly save the computational time and obtain a smoother Pareto frontier solution. The Pareto solution set of the rotor system with fan blade off can be divided into two regions, corresponding to the structural design ideas of “partial fusing design” and “complete fusing design” respectively. In addition to the steady-state amplitude of the fan disk, the other three objective functions can be reduced by more than 45.0% after optimization. In general, the optimal solution of the corresponding area of “complete fusing design” is better than that of “partial fusing design”.
Design Considerations for Directed-Lubrication Thrust Bearings Across a Wide Range of Operating Conditions With a Focus on Pressure Drop in the Oil Supply Path
Authors: Fabijonas Bruce R. , Krajewski Louis , Hegde Amruthkiran , Rodzwic Richard
Published: August 2024

Directed-lubrication bearings require careful control of the oil flow through the bearing to optimize performance. To do this, an accurate model of the pressure drop within the bearing is needed. This paper presents an equation-based model to compute the pressure drop and compares the model against test data and computational fluid dynamic simulations. We use this model to demonstrate the effects machining tolerances have on the pressure drop within a directed-lubrication thrust bearing. Finally, we discuss the current trend among OEMs to have a single bearing satisfy a range of operating conditions rather than an application specific condition and how this trend dramatically alters directed-lubrication bearing design philosophy.
Effect of Geometry and Heat Flux on Turbine Over-Tip Flow Power Extraction
Authors: Inhestern Lukas Benjamin , Peitsch Dieter , Paniagua Guillermo
Published: August 2024

The tip leakage flow is known to be a substantial loss contributor. A precise local loss decomposition of the relevant laminar and turbulent terms for viscous losses and thermal losses is required to predict the impact of tip design modification and revise current design guidelines. While losses due to viscous shear stress cause an irreversible reduction from the theoretical maximum power output, tip leakage vortices also penalize the flow turning. This paper combines a novel method for calculating volume-based loss terms and power extraction with an approach to track the tip leakage flow and to analyze the effect of heat transfer and varying tip gap height. Three different flow topologies were categorized for relative tip gap sizes between 0.23% and 1.10% passage height. The contribution of the tip leakage flow to the overall losses could be quantified at each streamwise location. The prime driver for efficiency improvements with tight clearance is achieved by a reduction in turbulent losses in the tip leakage vortices. Of secondary importance, but ubiquitous for all the tip gaps is the laminar loss, occurring in the overtip region and the main passage. The wall heat flux causes a massive effect on the aerothermal efficiency, the internal heat transfer increases exponentially with increasing wall heat flux.
Technology Readiness Assessment of Thermal Energy Storage Integrated With Gas Turbine Power Plants
Authors: Angello Leonard , Perullo Christopher , Widener Stanley , Booras George , Prescott Eric
Published: August 2024

This paper presents an integration readiness assessment for Thermal Energy Storage (TES) concepts. TES’s primary motivation is to store surplus energy and release it as needed to balance demand. Within the broader energy market, TES seeks to capture arbitrage opportunities and enable higher capacity factors for Variable Renewable Energy (VRE) sources like wind and solar. The paper explores how integrating energy storage with gas-turbine-based power plants can enhance value and capacity while reducing CO2 emissions. Both simple cycle and combined cycle plants are considered.

The paper carries out an Integration and System Readiness Assessment (ISRA) for three specific TES technologies: Brenmiller Crushed Rock, Pintail Power Liquid Salt Combined Cycle (LSCC), and Redox Box Thermochemical storage. The ISRA’s objective is to systematically evaluate the system readiness level (SRL) to determine the current development status and potential risks. Early identification of these risks can guide targeted demonstrations to mitigate risk and validate the technology. ISRA has been carried out for other systems but is being applied to the problem of the integration of new storage technology with existing generating assets with a desire to derisk technology showstoppers earlier in the maturation process. This paper demonstrates how this process can be used to focus technology development efforts on derisking activities vs. demonstration for demonstration’s sake.

Interviews were conducted with the technology developers to evaluate their current status, challenges, and successes. The focus is not solely on the score but on using the method to identify the technologies’ development stage. This paper specifically addresses readiness for integration into gas turbine power plants. Controls and balance of plant challenges when integrating into existing power plants were a common area for development.
Effect of Labyrinth Seal Parameters on Leakage and Rotordynamics in a Centrifugal Compressor Supported by Active Magnetic Bearings
Authors: Choudhury Tuhin , Ranjan Gyan , Smirnov Alexander , Heikkinen Janne , Rauhala Lauri , Sopanen Jussi
Published: August 2024

Centrifugal compressors will play a key role in efficiency of energy transition from fossil fuels in commercial and district heating applications. The overall efficiency of such compressors can be further improved by incorporating active magnetic bearings and high-speed direct drives, especially in high temperature, high-capacity heat pumps. However, at high speeds, the sealing of the refrigerants can present several challenges related to leakage and rotordynamic instability. Typically, hermetically sealed compressor design provides a simple, cost-effective solution with radial or axial labyrinth seals to separate compressor stages from the motor components and bearings. However, significant leakage from labyrinth seals could have adverse effect on magnetic bearings, such as cooling loss, contamination and imbalance. Moreover, asymmetric pressure distribution across impeller back plate or shaft surface can often lead to large cross coupling dynamic coefficients, thereby increasing the chances of instability during operation. To that end, this paper investigates how different seal parameters affect the leakage and rotordynamics in a single stage compressor. For both axial and radial labyrinth seals, the study presents the correlation between seal parameters and leakage. Lastly, a rotordynamic model is developed for the rotor -magnetic bearing system, including the dynamic coefficients of the seals and the impeller, and any possible instability are investigated.
Damage to a High Bypass Ratio Fan During UAS Ingestions
Authors: D’Souza Kiran , Sirivolu Dushyanth , Gomez Luis , Olivares Gerardo
Published: August 2024

Foreign object ingestion into engines has been studied for many years, but the focus has been on soft bodies (i.e., birds, ice). Recently, there has been a dramatic increase of uncrewed aircraft systems (UAS) in the airspace that represent a new threat to aircraft engines due to key components like the motor, battery, and camera being composed of hard components. Due to the differences between hard bodies and soft bodies, studies are required to understand the new threat these UAS pose to aircraft. The objective of this study is to investigate the impact of various factors such as impact orientation, fan rotational speed, relative translational speed, and radial impact location on the damage caused to a representative fan assembly. This study aims to analyze the sensitivity of these factors and their influence on the overall damage to the fan. The ingestion simulations will use a representative fan assembly model and a UAS model that has been experimentally validated at the conditions of an ingestion. This work will identify critical parameters of the ingestion and then utilize them to anticipate the extent of damage that may arise during specific stages of a flight where an ingestion is most probable. Moreover, it also compares these cases with some known baseline cases, such as a fan blade out and bird ingestion of similar mass, to understand the likely severity compared to more studied common cases.
How Frictional Heat Affects the Performance of Underplatform Dampers: Interface Temperature and Dynamic Behaviors
Authors: Gao Qian , Fan Yu , Zucca Stefano , Wu Yaguang , Li Lin
Published: August 2024

Underplatform dampers (UPDs) not only dissipate vibration energy of turbine blades, but also generate substantial frictional heat. The heat may potentially elevate the interface temperature beyond the melting point. Moreover, the increased interface temperature can alter the friction coefficient and contact normal force, significantly affecting the damping performance of UPDs. Consequently, the blade dynamics are highly coupled with frictional thermal effect. The interface temperature and corresponding dynamic behaviors (e.g. forced response, nonlinear mode) should be assessed considering the effect of frictional heat. In this paper, we develop a multi-physics model of turbine blades with UPDs, which integrates the contact nonlinearity and frictional heat transfer. The thermomechanical contact constitutive relationship is modeled at the contact interface. Two numerical methods are improved and utilized: Dry Friction Thermo-Mechanical Coupling Response Prediction (DFTMCP) and Thermo-Mechanical damped Nonlinear Normal Mode (TM-dNNM). DFTMCP predicts the interface temperature rise and nonlinear forced response, while TM-dNNM facilitates the identification of nonlinear modal characteristics and predicts the detailed temperature distribution. Results indicate quantitatively that frictional heat has a significant effect on the interface temperature and damping performance of UPD.
Effects of Lattice Orientation Angle on TPMS-Based Transpiration Cooling
Authors: Son Juchan , Broumand Mohsen , Pyo Yeongmin , Richer Patrick , Jodoin Bertrand , Hong Zekai
Published: August 2024

Establishing a continuous cooling film is an effective way to thermally protect hot-gas path components of gas turbines. For aero-engines, effusion cooling is the state-of-the-art method for developing cooling films. However, the cooling film generated by this method is far from ideal, as discrete miniature cooling air jets exiting from effusion cooling holes leave large gaps between cooling holes without adequate cooling film protection. Furthermore, effusion cooling jets can experience strong lift-off from component surfaces and are subsequently diluted due to mixing with the main flow. Recent advances in additive manufacturing (AM) technologies have enabled the fabrication of porous materials with precisely engineered lattice structures, significantly enhancing the film cooling effectiveness of hot-gas path components through transpiration cooling. A prior study has demonstrated highly promising transpiration cooling results by using a family of lattice geometries referred to as triply periodic minimal surface (TPMS) lattices. The present study experimentally investigates the influence of various TPMS lattice orientations on the film cooling effectiveness. Three types of TPMS structures, namely Diamond, Koch and Gyroid, are compared to demonstrate that the TPMS lattice orientation angle affects transpiration cooling performance, with different levels of sensitivity according to the TPMS structure. The TPMS lattice structures studied in this investigation are fabricated by stereolithography (SLA) 3D printing. The adiabatic cooling film effectiveness (AFE) is measured using pressure sensitive paint (PSP).
A Wind Speed Forecasting Method Using a Gaussian Process Regression Model Considering Data Uncertainty
Authors: Chen Huize , Jiang Xiaomo , Hui Huaiyu , Zhang Kexin
Published: August 2024

Wind speed forecasting has become an essential part of power forecasting, daily operation, and optimal scheduling of wind farms. However, due to the extreme randomness and unpredictability of wind resources, it’s still a very challenging task to accurately forecast wind speed considering data uncertainties. Most existing methods do not take into account the data uncertainty and randomness in wind speed forecasting, resulting in inaccurate results in practical applications. This paper proposes a hybrid intelligent model for wind speed forecasting under uncertainties by adeptly integrating Bayesian Discrete Wavelet Packet Transform (BDWPT) and Gaussian Process Regression (GPR). Firstly, the BDWPT method is applied to reduce the noise and randomness of raw data by taking advantage of its powerful adaptive denoising capability. Then, the GPR model is developed to model the randomness in wind speed forecasting. Finally, a comparison study with traditional methods by using the data collected from real-world wind farms is conducted to show the advantages of the proposed methodology in terms of one-step and multi-step cases. This study provides a promising approach to accurately forecast wind speed for turbine design and power management considering data uncertainties.
Preliminary Characterization of the Desolination Project Demo Plant: Design and Off-Design Operability
Authors: Morosini Ettore , Astolfi Marco , Doninelli Michele , Iora Paolo , Serret Damien , Hugo Jean-Michel , Manzolini Giampaolo
Published: August 2024

This work presents the preliminary performance of the simple recuperative transcritical power cycle of the DESOLINATION project demo plant. The cycle operates with the CO2+SO2 mixture and it is air-cooled, built in a CSP-like environment with high radiation and high ambient temperature. The axial turbine, with a flowrate of 0.2 m3/s at its inlet, imposes the size of the cycle at 1.8 MWel. Innovative recuperators and primary heat exchangers with internal gyroid structures are adopted, modelled with a simplified approach in MATLAB by fitting results of CFD simulations. By modelling the cycle offdesign in sliding pressure, cycle efficiencies above 30% can be obtained, even at part load. Fixing a high ambient temperature at design conditions, the cycle cannot operate with ambient temperatures below 30°C if the condenser fans work at fixed speed, whereas ambient temperatures of 10°C are possible modifying the air velocity. By preliminary sizing the system piping, it is determined that the overall cycle inventory depends only on the conditions in the condenser, determined by the ambient temperature. Accordingly, an inventory variation of around 300 kg must be handled to correctly operate in offdesign.
Influence of Baseplate Flexibility in Rotordynamic Analysis of Rotating Equipment
Authors: D’Addio Vincenzo , Gorgeri Alessio , Libraschi Mirko , Capanni Francesco
Published: August 2024

The aim of this study is to show how baseplate flexibility can be included in the rotodynamic analysis in an efficient yet accurate manner. Baseplate modal information is added into the classical rotodynamic system (rotor + bearings) using a proper modal condensation method. On the one hand, the relatively complex shape of the baseplate requires 3D modelling strategies, while rotodynamic analysis is normally conducted using 1D beam elements. The mono-dimensional approach is motivated by the axial symmetricity of the rotor, and it facilitates sensitivity analyses related to the microgeometry uncertainty of the fluid film bearing. The use of 1D approaches in rotodynamic is still a highly debated argument, especially due to the recent improvements of computer performance and the consequently increased viability of high-fidelity models. Nevertheless, the time consumption is not the only (nor most important) advantage of 1D approaches: a low fidelity model is better comparable to, and is more easily calibrated with, experimental test data (3D high fidelity models are often not verifiable by observations). There are several ways to include the baseplate dynamics on the rotodynamic system and in this paper three methods of representation will be presented and compared: State Space Matrices (SSM), Frequency Response Function (FRF) and Dynamic Stiffness & Damping Method (DSM).
Probabilistic Modelling Geometric Tolerance and LCF Life of Gas Turbine Compressor Blade
Authors: Meng Zhiqiang (David) , Bluck Richard , Sjödin Björn
Published: August 2024

This paper presents a probabilistic LCF assessment for geometric tolerances on high load contact surfaces of gas turbine compressor blades. The typical patterns of the geometric deviations for the root contact flank of the compressor blades are identified and characterized according to CMM measurements of the blade root. These typical patterns are closely related to the root form manufacture tools and process.

FE models for the typical geometric deviation patterns are created based on nodal coordinates transformation of the surface nodes on the blade root contact flanks and radius. An optimized blade root profile tolerance is established, which enables significant cost saving. The elastic-plastic FE analysis with nonlinear contact model, material strain-life test, response surface and constrained Monte Carlo simulation are used to create a probabilistic LCF life model for the optimized tolerance. The model quantifies the effect of the geometric deviations, blade mass and material property on the blade LCF life.

The result shows that with the optimized tolerance, the probability of blade LCF failure is very low and acceptable. It is also shown that the strain life material property is the most critical factor for the LCF failure. The root profile tolerance and blade mass are seen to have a much weaker effect on the blade LCF life.