bluuebunny/crossref_metadata_2025 huggingface dataset:
Overall Cooling Effectiveness of Effusion Cooled and Thermal Barrier Coated Swirl Stabilized Liquid Fueled Combustor Liner in Reacting Flow Conditions With Infrared Thermography
Authors: Tin Ibrahim Edhem , Ural Muhammed Emin , Ozogul Hamdullah
Published: August 2024

Effusion cooling and thermal barrier coating have a crucial ability to cool down modern combustor liners and keep metal temperature below material maximum service temperature. Therefore this method has enabled high combustion temperature, which leads to powerful and more efficient gas turbine engines over the last decades. Effusion cooling method is obtained by arrays of holes settled all over a combustor liner to generate a uniform film layer at the hot gas side. Coupling of effusion cooling and thermal barrier coating provides high cooling effectiveness and low amount of coolant demand.

In this paper, experimental results of an effusion cooled and thermal barrier coated (TBC) combustion liner are presented. The rig was liquid fueled and swirl stabilized, in order to generate engine like reacting conditions. In this study, the overall cooling effectiveness of the liner has been examined under rich fuel conditions in different coolant-to-main air ratios. The combustion liner of a can combustor was laser drilled to provide 25 degrees inclined holes for an effective effusion cooling scheme. Thermal Barrier Coating has been applied equal to 40% off metal thickness of the liner. The effusion cooling scheme has been formed to have dense staggered array with s/d = 9. Infrared Thermography (IRT) was employed to measure the liner metal temperature and overall cooling effectiveness values were identified.
Noise Source Identification for the Unsteady Low Pressure Turbine Flow Fields
Authors: Yan Lanyi , Simoni Daniele , Luan Yigang , Sun Tao , Barsi Dario , Zunino Pietro
Published: August 2024

The paper presents a data processing methodology to identify the noise sources in low pressure turbine stages and their relative importance. Scale adaptive simulation (SAS) has been carried out on a geometry reproducing the midspan blade section of an entire LPT stage. The proper orthogonal decomposition (POD) is applied to data matrices constructed with the velocity and the pressure fields in order to distinctly extract the coherent structures responsible for velocity fluctuations and pressure waves (i.e. POD modes from the corresponding kernel), their temporal evolution and energies. The cross-correlation matrices of the pressure modes and the velocity modes reveal the degree of coupling between pressure and velocity oscillations, thus highlighting the modes linked to the same flow phenomena. The results show that the periodic vortex shedding at the stator trailing edge emits strong pressure waves, and the upstream propagating waves reflect against the adjacent stator suction surface. The POD modes related to the rotor-stator interaction show peak amplitudes at the blade passing frequency and its harmonics and their shapes mimic the potential interaction in the stator domain and the migration of viscous wakes in the rotor domain. The POD modes with lower energy content correspond to the stochastic turbulent structures originated from the turbulent boundary layers as well as those carried by the vane and blade wakes. The biggest noise sources of the current flow fields are identified to be the von Karman vortex street downstream the stator trailing edge and the rotorstator interaction.
The Effect of Air-Water Mixture on the Dynamic Response of a Hydrodynamic Journal Bearing With Inclined Grooves
Authors: Voitus Anthony , Arghir Mihai , Hassini Mohamed-Amine
Published: August 2024

Water lubricated hydrodynamic journal bearings with deep inclined grooves are often used to support radial loads and dampen pump vibrations in nuclear power plants. The inclined grooves increase the pumping effect of the lubricant thus reducing wear and friction during rotor start-up and coast-down. The deep grooves also facilitate the removal of debris without damaging the bearing. The load capacity and the stability of this type of bearing is studied in the present work. A sensitivity study of the impact of the number of grooves on bearing performance underlined the superiority of the journal bearing with two inclined grooves. Moreover, these journal bearings may operate with a mixture of water and air. This compressible two-phase lubricant will modify the load capacity and the stability of the journal bearing. The impact of the ingested volume fraction of air is therefore investigated. A physical model of the homogeneous air-water mixture linking the local air volume fraction with the pressure was used in conjunction with the numerical solution of the compressible Reynolds equation on an unstructured grid. It was found that the air ingestion in the 2-inclined grooves journal bearing decreases the load capacity but improves the stability for mild and low loads.
Preliminary Vibro-Acoustic Investigation of an Oil-Free Centrifugal Compressor
Authors: Krishna Karthik , Mendonca Fagundes Tadeu , Yan Jin , Richman Brenden , Dingman Ryan
Published: August 2024

The demand for HVAC chiller systems in commercial centers is ever-increasing. Chillers with centrifugal compressor units produce high-frequency noise, a significant problem that needs to be addressed. The blade passing frequency is the primary noise source a centrifugal compressor generates. The objective of this paper is to investigate the vibro-acoustic performance of an oil-free two-stage centrifugal compressor with magnetic bearings via numerical modeling. The noise source is obtained using the time-variant pressure data from the unsteady RANS simulation of the aerodynamic parts of the compressor. The unsteady pressure data produced is integrated onto the corresponding solid domain of the compressor, and a harmonic response analysis is carried out to quantify the vibration energy transferred through the compressor system at specific engine orders. Finally, the far-field sound pressure level generated by the compressor is quantified for all engine orders up to 10kHz. Additionally, experimental testing of the centrifugal compressor in a anechoic chamber is carried out to determine the sound pressure level and validate the numerical methodology. Results indicate that numerical findings are in good agreement with the test data, indicating that the developed methodology is capable of accurately predicting the tonal noise in the current application. Furthermore, results show the tonal noise generated is primarily dependent on the number of main blades and splitter blades of the impeller, revealing those components to be the primary source of compressor noise.
Experimental and Analytical Investigation of Labyrinth Seal Packing Ring Behavior in Contact With a Whirling Rotor
Authors: Tsukuda Tomohiko , Iwasaki Yoshifumi , Iwai Shogo , Tashima Tsuguhisa
Published: August 2024

Labyrinth seal packing ring behavior in case of contact with a whirling rotor which simulates the expected rotor vibration in an actual steam turbine was investigated experimentally and analytically. The labyrinth seal packing ring used in this study was designed to be supported to a casing with weak coil springs. The force of the coil springs is set to be slightly larger than the packing ring weight so that it escapes away from the rotor in case of contact with a rotor and the temperature rise of the rotor could be prevented.

Experimental investigation with a seal test rig was conducted with two different types of split structures of the packing ring. The effect of the split structure on the packing ring behavior and the rotor temperature rise in case of contact with a whirling rotor was investigated. The experimental results showed that the temperature rise of the rotor was smaller for the 3-split structure than the 2-split structure in case of contact with a whirling rotor. It also showed the amplitude and the dominant frequency of the vibration of the packing ring segment was different between the 3-split structure and the 2-split structure.

Analytical investigation using motion equations of a rigid body was carried out to understand the packing ring behavior. The difference of the segment behavior between the 2-split structure and the 3-split structure was explained by the solutions obtained from the motion equations. The difference of temperature rise of a rotor between the 2-split structure and the 3-split structure was discussed by simple evaluation of heat generation using the solutions of the equations.
Micro-PIV Investigation of Near-Critical and Liquid CO2 Conditions Inside a T-Channel Setup
Authors: Ghorpade Ritesh , Kim Gihun , Niazi Soroush , Peles Yoav , Vasu Subith
Published: August 2024

Supercritical CO2 (sCO2) has been proposed for a plethora of applications, such as power generation, air conditioning, and thermal management of electronic equipment. In proximity to critical conditions, the thermal and transport properties of the CO2 vary abruptly, promoting a significant heat transfer enhancement. Revealing the heat transfer processes associated with CO2 flows requires measuring fluid temperature, pressure, heat transfer coefficients, velocities, etc. However, fundamental knowledge about the heat transfer processes at near-critical conditions is not fully understood. An advanced optical technique with microparticle image velocimetry (PIV) was applied to measure the velocity flow field of liquid CO2 near critical thermodynamic conditions flowing through a T -channel. The captured flow field of the CO2 was processed using a micro-PIV 2D2C (Two Directional Two Component) cross-correlation method for obtaining the velocity vectors. Silver-coated hollow glass microspheres with a range of diameters of 5 microns to 30 microns were used as a tracer and mixed with CO2 to track the flow patterns. The experimental setup consists of the integrated manifold for CO2 flow, RTD probes for temperature measurements, digital pressure transducers for pressure measurements, and PIV arrangement with laser. The present experimental study is an initial step to fully reveal the velocity distribution of liquid CO2 inside a T-channel in near-critical thermodynamic conditions.
Improving Micro-Mixing Combustion Stability Using Fuel Preheating and Product Recirculation
Authors: Landry-Blais Alexandre , Bellavance Xavier , Dehue Mathilde , Plante Jean-Sébastien , Picard Mathieu
Published: August 2024

Micro-mixing is a promising combustion approach due to its inherent safety against flashback and autoignition, with multiple studies having demonstrated low NOx levels in the order of premixed combustion. Previous work has extended the operating limits of micro-mixing combustion to the design requirements of highly recuperated gas turbines, demonstrating low NOx performance at inlet temperatures of up to ∼1000 K with hydrogen and hydrocarbon-based fuels such as propane, natural gas, and jet fuel. Due to its highly reactive nature, micro-mixing combustion of hydrogen is very stable, but instabilities were observed with hydrocarbon-based fuels when operating near premixed levels of NOx due to their slower reaction rates, indicating that a trade-off exists between NOx emissions and combustion stability. This paper presents the experimental results of a new micro-mixing injector designed to improve combustion stability by 1) increasing the recirculation of combustion products to the flame zone, and 2) preheating the fuel by heat transfer from the combustion products to the injector. Although this configuration is still susceptible to instabilities, their amplitudes are much lower, with levels of < 10 dB compared to ∼20 dB for the standard micro-mixing injector. NOx emissions are similar for both injector configurations, indicating a better trade-off between combustion stability and emissions when operating near the levels of perfectly premixed combustion for the new injector configuration.
Understanding the Flow Field in a Highly Loaded Tandem Compressor Cascade
Authors: Tran Thanh-Son , Babin Cedric , Fontaneto Fabrizio , Coussement Gregory , Verstraete Tom
Published: August 2024

Large flow turning in compressor cascades with single airfoils requires an effective control of the boundary layer growth under the diffusing flow. An alternative approach consists of distributing the loading over two subsequent airfoils, using a so-called tandem blade, to, in some measure, restart the boundary layer before flow separation occurs. It is, however, not always clear whether the benefits of the two-blade setup justify the additional manufacturing complexity. The present work explores the tandem blade concept using a gradient-based optimization method to produce an efficient, highly loaded compressor cascade blade directly. A comparison between two-dimensional single and tandem configurations is first presented to clarify the benefits of one over the other. The geometry is optimized for each concept using a gradient-based optimization technique to improve the pressure loss coefficient at multiple operating points for a given flow-turning constraint. While the optimized single and tandem blade designs have similar performance, the lower solidity of the latter provides a lighter compressor stage for the considered operating range. A three-dimensional tandem compressor cascade based on the two-dimensional study is then optimized to account for secondary flows. The aerodynamic performance and the operating range are assessed and compared, along with a study of the physical phenomena surrounding the tandem configuration. The resulting geometry presents similar non-conventional features observed during the two-dimensional study that exploits the flow mechanism of two-airfoil configurations.
Numerical Analysis of the Effect of Geometric Variations on the Mass Flow Distribution for an Under-Race Lubrication System
Authors: Aguirre Bermudez Daniel Mateo , Abraham Aju , Joshi Shreyas , Schwitzke Corina , Bauer Hans-Jörg
Published: August 2024

Operating conditions of modern aero-engines place a significant demand on oil for the lubrication and cooling of roller bearings. The supply of the required lubricant is often achieved by a system consisting of an oil jet targeted onto a feed geometry machined into the shaft. This cavity leads the oil through a number of equispaced feed holes in the inner race of the bearing, allowing direct lubrication and cooling of the components. This lubrication technique is commonly known as under-race lubrication. Achieving uniformity is of crucial importance for efficient lubrication and cooling. This study explores the effect of key geometric parameters of the shaft cavity on the oil flow distribution for different operating conditions. The analysis is perfomed using Implicit Incompressible Smoothed Particles Hydrodynamics (I-ISPH) simulations, focusing on the variation of groove length, groove depth, groove taper, hole diameter and hole axial distance. The analysis of the results reveals that groove characteristics have a limited impact, while hole diameter and axial distance significantly influence the oil distribution. An investigation of the film thickness inside the cavity is performed, and its correlation with the oil mass flow through the feed holes is discussed.
Effect of Relative Location of Film Cooling Hole With Internal Angled Ribs on the Film Cooling Effectiveness of a Gas Turbine Blade
Authors: Kang Young Jun , Jeong Jin Young , Kim Hyeok Je , Kim Gi Mun , Kwak Jae Su
Published: August 2024

Film cooling effectiveness (FCE) is strongly influenced by film cooling hole geometry, mainstream boundary condition (boundary layer thickness and turbulence intensity), and coolant injection conditions (density ratio and blowing ratio). It is also shown that the flow structure of coolant at the inlet of a cooling hole also affects film cooling performance. In this study, the inlet flow structure resulting from the rib turbulators installed in the internal channel and its effects on the film cooling effectiveness were analyzed numerically. The numerical result was also validated with experimental result obtained with the pressure sensitive paint (PSP) technique. Studies were conducted at 25 relative locations of a fan-shaped hole on the 60-degree angle ribbed channel. Furthermore, the results were compared to cases that coolant was supplied through the plenum chamber. Results showed that the relative location of the film cooling hole with respect to the angled rib significantly altered the flow structure of coolant and the distribution of FCE. Also, FCE with the angled ribbed channel generally showed low FCE compared to the case with a plenum chamber.
Numerical Investigation of the Influence of Tyler-Sofrin Modes on the Increase in Blade Unsteady Pressure in a Subsonic Axial Compressor
Authors: Oshio Tetsuya , Aotsuka Mizuho , Kusuda Shinya , Tateishi Atsushi
Published: August 2024

The present paper describes an investigation on the increase in unsteady pressure on rotor blade due to Tyler-Sofrin modes generated by stator-rotor interaction. The investigation is conducted numerically using CFD, which is unsteady RANS calculation on a quasi-3D model of a single stage cascade extracted from a 3.5 stages subsonic axial compressor. Several parameters such as stator vane count, rotor speed and axial gap between stator and rotor are varied to change characteristics of Tyler-Sofrin modes. As a result, it is found that the pressure amplitude of the 1st-harmonic of vane passing frequency on the blade surface increases at some specific conditions of the vane count and rotor speed. The modal phase velocity of a Tyler-Sofrin mode is related to the pressure amplitude. A parameter called Phase Speed Ratio (PSR) is introduced to express the relationship between the modal phase velocity of Tyler-Sofrin modes and the velocity of acoustic propagation in the circumferential direction. In the region where the PSR is lower than 1.0, the pressure amplitude gradually increases ranging from around 0.5 and peaks around 0.9. Then, the pressure amplitude decreases in the range of PSR from 0.9 to 1.0. After the PSR exceeds 1.0, the pressure amplitude rapidly decreases. This result indicates that the pressure amplitude of the 1st-harmonic of vane passing frequency increases when the modal phase velocity approaches the velocity of acoustic propagation. It is also found that the pressure amplitude peaks close to PSR = 1.0 when the axial gap between stator and rotor is large. It suggests that the non-monotonically increase in the pressure amplitude on the rotor blade is influenced by upstream stator.
Manufacturing and Build Variations Modelling for Multi-Stage Axial Compressors: CFD Aerodynamic Predictions
Authors: Bruni Giuseppe , Krishnababu Senthil K.
Published: August 2024

The numerical prediction of multi-stage compressor flows has historically been a challenge for CFD models, due to their complex, turbulent and three-dimensional nature. High-fidelity models such as LES and DNS have shown promising results, but their application is limited by the high computational cost, while steady-state RANS simulations are still used for the majority of applications in the industry. Over the years, engine manufacturers have developed best-practices and guidelines for multi-stage axial compressor simulations, providing reliable CFD models capable of predictions comparable to test data, both with regards to performance and surge margin at different operating conditions. However, even with state-of-the-art models, several discrepancies can be observed and are generally addressed with calibration based on operational experience. These discrepancies are partially due to known limitations of steady-state CFD, as well as to modelling assumptions and the use of idealised geometries. This paper demonstrates how the accuracy of CFD predictions can be greatly improved by modelling the effect of manufacturing and build variations, such as tip clearances, surface roughness and in-tolerance geometry variations. The resulting engine-build specific models show greatly improved agreement with engine test data, with no increase in computational cost. These models can be used as part of the design process, to develop robust axial compressor designs desensitized to these variations. Moreover, the results from the analyses can be used to re-define tolerance ranges and drawing specifications, to reduce the potential impact on build-to-build engine performance scatter.
Analysis of the Instantaneous Film Cooling Effectiveness on Showerhead Film Cooling Using Fast Response Pressure Sensitive Paint (Fast-PSP)
Authors: Sounik Jeremy L. , Wright Lesley M.
Published: August 2024

The instantaneous effect of unsteady wakes on film cooling effectiveness using a fast response pressure sensitive paint (PSP) was studied. Testing was performed in a five passage, low speed wind tunnel using five times scaled versions of typical high pressure blades (axial chord of 17 cm). The blowing ratios studied include 0.8 and 1.2, with a density ratio of 1.0 and 1.5 at each blowing ratio. Upstream unsteady wakes were produced by a spoked wheel type wake generator. The wake generator, utilizing a varying number of rods and rotational speeds, produced Strouhal numbers of 0.1 and 0.3 while the wind tunnel inlet mainstream Reynolds number was held at a constant value of 300,000 (mainstream velocity of 21 m/s) for every test case. For each Strouhal number, blowing ratio and density ratio studied, several positions within the period between rods, and the resulting wakes, were recorded. Results show that the location of the wake along a blade’s surface had a significant impact on the film cooling effectiveness in the immediate location of the wake. An overall fluctuation of up to 69% in film cooling effectiveness was observed within the wake period. Conclusions also show that while mainstream flows with higher Strouhal numbers tend to decrease film cooling effectiveness, the fluctuation of film cooling effectiveness at higher Strouhal numbers was reduced when compared to results utilizing lower Strouhal numbers. A comparison of results from tests at different density ratios showed a much smaller change in the instantaneous film cooling effectiveness between test cases.
Flow Disturbance by Intrusive Instrumentation: Part 2 – Protrusions on the Suction Side of HP Compressor Vanes
Authors: Schäflein Lukas , Jung Daniel , Jeschke Peter , Wunderer Roland
Published: August 2024

In this study, we investigate the aerodynamic impact of spanwise pressure tubes located on the suction side of a high-pressure compressor stator vane. For our experiments in a linear cascade wind tunnel, we modeled the pressure tubes as simplified protrusions. The experiments were conducted at a Mach number of ∼0.5 and a Reynolds number of 790,000. By testing six configurations with protrusion widths between 8% to 24% of the chord lengths and heights of 33% and 66% of the maximum vane thickness, we find that increasing the protrusion height as well as reducing the protrusion width leads to an increase of the total pressure loss. Consequently, the narrowest and highest protrusion with a width of 8% and a height of 66% represents the worst case with a total pressure loss increase of factor 5.7 compared to a nominal vane. In the best case, the protrusion with a width of 24% and a height of 33% leads to an increase in the total pressure loss of factor 2.1 compared to a nominal vane. Oil flow visualization and CFD simulations reveal complete flow separation downstream of higher protrusions, creating large recirculation zones. For lower protrusions the flow mostly reattaches at the top of the protrusions. The study offers insights for engineers designing intrusive instrumentation on compressor vanes, enabling them to minimize additional total pressure loss.
Break-Up and Atomization Characteristics of N-Dodecane in High-Temperature Crossflow
Authors: Johny Tom , Bhatia Bharat , De Ashoke
Published: August 2024

The present study numerically investigates the break-up and atomization characteristics of n-dodecane, a widely used surrogate for jet fuels and diesel, under high pressure and temperature conditions of crossflow. This research can provide valuable insight into optimizing fuel injection processes and reducing emissions in gas turbine engines. Simulated test conditions range from 3.8 to 10 bar and at temperatures of473K, varying the momentum flux ratios (q) in the range of 6–30 and Weber number (We) in the range of 100–1200. An OpenFOAM-based compressible VOF-LPT coupled framework is developed to simulate the high-temperature evaporating spray problem. Numerical validation of the developed framework is done based on the high-temperature experimental data from Amighi and Ashgriz [1,2] for water. It is further utilized to simulate n-dodecane injections in a crossflow. The validation is performed regarding liquid jet penetration and droplet sizes, finding accurate agreement with experimental data. The effect of temperature and pressure on break-up and atomization, liquid jet penetration, and droplet size characteristics are also discussed. An increased fine droplet production is observed for dodecane at high temperatures, potentially due to enhanced break-up and heat transfer rates. Further, the variation of droplet sizes downstream of injection for n-dodecane fuel under different pressure conditions is also discussed. Determination of quantitative droplet size distribution highlights the solver’s utility in understanding atomization, evaporation, and mixing under high-temperature crossflow environments.
Power Analysis of Wave Speed Coincidence Stability and the Effect of Asymmetry
Authors: Ma Chris , Garvey Seamus D. , Kamesh Punithavathy , Rix Andrew I. J.
Published: August 2024

This paper considers the interaction between a rotating bladed-disc and static casing, specifically a synchronisation phenomenon called wave speed coincidence. Through tip rub, travelling waves in the bladed-disc and casing can interact and cause large amplitudes of vibration. Previous work has analysed this phenomenon using time integration methods, which are often too computationally expensive for early design stages, and frequency domain approaches such as the harmonic balance method, which require simplification in the periodicity of the problem limiting the usefulness of such methods. This paper demonstrates the use of a power method and consideration of periodicity over a contact cycle. This allows the problem to still be considered as a periodic behaviour, but without the loss of generality associated with conditional harmonic balance methods. This is useful as a faster screening method for preliminary design stages and a way to down-select high risk cases, where further time integration analyses can be performed. The method is also applied to cases with asymmetric casings, allowing quantitative assessment of the effect of asymmetry in the future. In this case, as a result of the asymmetry, the interaction quickly became non-wave speed coincidence. Nevertheless positive power into the casing continued to be observed in some cases, suggesting potential instability from the subsequent blade rubs.
Research on Calculation Method of Variable Specific Heat Performance of Wide-Speed Range Aeroengine
Authors: Du Huipeng , Liu Chuankai
Published: August 2024

Given the escalating demand for hypersonic maneuverability in forthcoming times, it is imperative to advance wide-speed range engine technology, while acknowledging that diverse incoming flow conditions exert a substantial influence on aerothermal processes. The conventional method for calculating aerodynamic performance, which assumes constant specific heat and employs a velocity coefficient parameter, is no longer applicable to aeroengines operating across a wide range of speeds. Therefore, it is crucial to develop an appropriate calculation method for variable specific heat in this type of engine and establish a comprehensive physical property library based on object-oriented programming methodology to cater to the future calculation requirements of diverse engine components. The present study employs polynomial fitting to determine engineering thermodynamic properties, while incorporating the Qin Jiushao (or Horner) algorithm to enhance computational efficiency. The novel approach of utilizing energy conservation and isentropic process principles, in conjunction with numerical methods such as false position, has been employed to ensure the convergence of aerodynamic properties across a wide range of speeds. Subsequently, a novel algorithm is developed for two crucial processes within the intake and exhaust system: the stagnation process and expansion process. Furthermore, a comparative analysis is conducted to discern disparities between these algorithms. Concurrently, employing global sensitivity analysis methodology enables an examination of the impact of altitude and Mach number on the calculated total parameter results. The results indicate that during the stagnation process at 30km, 5Ma, there is an approximate temperature difference of 10% between the two algorithms, while the total pressure difference exceeds 25%. The impact of Mach number on the total temperature is significant, as is the influence of Mach number and altitude on the total pressure. During the expansion process, the critical temperature exhibit minimal difference, but exhaust velocity is dependent on the temperature difference.
High-Fidelity Simulation of an Industrial Low-Pressure Pump of Helicopter Using Coupled LES/CAA Method
Authors: Bénez Pierre , Moureau Vincent , Cailler Mélody , Ribert Guillaume , Mingret Pascal , Robin Marine
Published: August 2024

This paper is devoted to the simulation of an industrial hybrid regenerative liquid-ring pump in pure liquid conditions. An hybrid Large-Eddy Simulation (LES) / Computational AeroAcoustic (CAA) coupled method, based on the association between a low-Mach number flow solver and an implicit linear acoustic solver, is used to rebuild efficiently the hydro-acoustic pressure fluctuations generated by the flow. The acoustic effects are solved implicitly to avoid being limited by the acoustic time step at low-Mach number. This fully coupled strategy, already validated in a body-fitted formalism, is adapted here to an immersed-boundary formalism for the modeling of the pump rotor motion. The LES/CAA simulation of the pump is used to investigate the potential impact of the acoustics on the pump performances and the fuel vaporization risks.
Computational Study of Additively Manufactured Internally Cooled Airfoils for Industrial Gas Turbine Applications
Authors: Krull Matthew , Lynch Stephen , Searle Matthew , Floyd Timothy , Ames Forrest E. , Straub Douglas
Published: August 2024

Internal cooling features such as pin-fins, impingement jets, and rib-turbulators are necessary to keep turbine components cool, but if sufficiently advanced can potentially also eliminate the need for film cooling on turbine blades particularly in industrial gas turbines where temperatures are not extreme. Furthermore, by leveraging additive manufacturing (AM), other advanced designs such as lattice and incremental impingement configurations are possible and have recently been experimentally tested. While the performance of such configurations has been quantified recently through means of overall cooling effectiveness, it is not as clear why certain designs were better than others, or what the mechanisms were behind the observed external cooling patterns. The purpose of this study was to computationally analyze different advanced turbine blade internal cooling designs previously tested by the National Energy Technology Laboratory. Conjugate steady Reynolds Averaged Navier Stokes (RANS) simulations were performed on three symmetric blades with different internal cooling configurations: a baseline cooling design with pin-fin arrays, a double wall design with impingement jets and serpentine channels, and an incremental impingement design. The computational results were compared to previously obtained experimental data and were further studied to understand the advantages and disadvantages of different cooling configurations. This study found that the double wall design had better overall cooling than the baseline design, as found in the experiment, because of increased convective heat transfer in the double-wall region. However, the computational model based on design-intent geometry indicated a higher rate of coolant flow in the trailing edge as compared to the experiment resulting in an overprediction of cooling. Additionally, the incremental impingement design had the highest overall cooling effectiveness of the various designs. This was attributed to the impingement jets in the incremental impingement design that produced relatively uniformly distributed high internal heat transfer coefficients.
Unsteady Flow Simulations of a Transonic Low-Pressure Turbine Cascade
Authors: Hullin Liza , Gonzalez-Martino Ignacio , Bonnal Benoît
Published: August 2024

High-speed low-pressure turbine blades (HS-LPT) are a key component in the development of high-efficiency geared engine architectures. High-fidelity CFD simulations are progressively being integrated into the design process of engine components, to get a better insight in the complex flow behavior and guide the shape optimization process. The current study presents Very-Large Eddy Simulations (VLES) of the flow across a HS-LPT, using Lattice-Boltzmann Methods (LBM). Different solvers of the commercial software SIMULIA PowerFLOW® have been used for this study. The selected benchmark case is the SPLEEN cascade, a next-generation HS-LPT cascade rig developed by Von Karman Institute and Safran Aircraft Engines, as part of a large European collaborative project. A subset of the large amount of available test rig data has been used here to benchmark the CFD solver. Hence, the study aims at assessing the ability of this numerical methodology to predict several complex flow phenomena occurring at engine relevant Mach and Reynolds numbers. For instance, we observed (1) unsteady transonic flows, (2) laminar separation bubble, (3) natural laminar-to-turbulent transition, (4) unsteady bypass transition due to wake impingement coming from upstream turbulence, (5) endwall 3D effects, (6) corner stall separation and (7) fluctuation of the flow due to periodic wakes coming from translating bars representing wakes of upstream rotor.
Numerical Investigation of Two-Phase N-Decane/Air Rotating Detonation Engines With Different Numbers of Fuel Orifices
Authors: Shao Xiaofeng , Zhao Ningbo , Zhang Wei , Zheng Hongtao
Published: August 2024

In this study, n-decane/air two-phase rotating detonation is numerically investigated based on Eulerian-Lagrangian method. Three-dimensional rotating detonation chamber (RDC) with various numbers of fuel orifices (30, 45, 60 and 90) is considered. The effects of numbers of fuel orifices on the fuel mixing characteristics, the flow field structures and the propagation characteristics of the rotating detonation wave (RDW) are analyzed. The results show that the liquid fuel mixing is influenced by the fuel jets and the incoming air shear. The former mainly affects the mixing uniformity, while the latter has a great influence on the Sauter mean diameter. Specifically, increasing the numbers of fuel orifices improves the mixing uniformity but slightly rises the Sauter mean diameter. Besides, the number of fuel orifices has a significant impact on the propagation mode of RDW. Single-wave mode is established in RDC except for the 30 orifices. Furthermore, a dimensionless kinematic parameter (α) is used to represent the fuel reactivity and predict the propagation mode of RDW. Moreover, the propagation parameters of RDW vary greatly with different numbers of fuel orifices. As the number of orifices increased, the formation time to stable operation of RDW decreases. The research results can provide guidance for the design of two-phase RDE.
Generative Design of a Gas Turbine Combustor Using Invertible Neural Networks
Authors: Krüger Patrick , Gottschalk Hanno , Werdelmann Bastian , Krebs Werner
Published: August 2024

The need to burn 100% H2 in high efficient gas turbines featuring low NOx combustion in premix mode require the complete redesign of the combustion system to ensure stable operation without any flashback. Since all engine frames featuring a power range from 4 MW up to 600 MW are affected, a huge design effort is expected. To reduce this effort, especially to transfer knowledge between the different engine classes, generative design methods using latest AI technology will provide promising potential.

In this work, this challenge is approached utilizing the current advances in generative artificial intelligence. We train an In-vertible Neural Network (INN) on an expandable database of geometrically parameterized combustor designs with simulated performance labels. Utilizing the INN in its inverse direction, multiple design proposals are generated which fulfill specified performance labels.
Enhanced Modelling of the Phenomenon of Vortex Shedding From a Low-Speed Axial Flow Rotor Blade Profile
Authors: Daku Gábor , Vad János
Published: August 2024

The paper presents CFD case studies on vortex shedding from an asymmetric RAF-6E airfoil profile being a representative of low-speed axial fan rotor blades, for angles of attack of α = 0.0°...2.7°, and chord-based Reynolds numbers Rec = (0.6...1.0) · 105. The shed vortices were identified on the basis of Lagrangian-averaged vorticity deviation. An organized dataset has been established for a comprehensive overview of the profile vortex shedding (PVS) phenomenon, enabling order-of-magnitude estimation of data and trends related to the size, rotation, circulation, and travelling velocity of the vortices. Literature-based rotationally symmetric aerodynamic models, as well as a simplified description of source term of vortex sound were applied to the shed vortices. On this basis, an enhanced modelling of PVS has been carried out for a straightforward and yet adequate consideration of the concerted aerodynamic and aeroacoustic aspects of PVS. Such modelling can give a contribution to preliminary fan design by taking the effects of PVS into account on blade vibration and fan noise.
Rejuvenation Heat Treatment Development to Extend the Service Life of René N4 Single Crystal Gas Turbine Blades
Authors: Motta Cristina , Mastromatteo Francesco , Gariboldi Elisabetta , Cappuccini Filippo
Published: August 2024

Single crystal superalloys are widely used for gas turbine blades exposed to high stresses, high temperatures in aggressive environments. When these components reach their serviceable limit, they must be replaced by new ones, with an important impact in terms of maintenance costs. Significant savings can be achieved through the application of a rejuvenation heat treatment, able to extend the life of a serviced turbine blade beyond its original design intent and avoid parts scrap.

The success of such a technology for SX-superalloys is related to the effective restoration of the original γ/γ’ microstructure, which is linked to the material mechanical properties, without impairing the original single crystal structure. Indeed, one challenge in designing a rejuvenation heat treatment for single crystal superalloys is the risk of recrystallization, which must be kept under control. This work is focused on the development of a rejuvenation heat treatment for René N4 alloy. Different rejuvenation cycles have been explored through an in-depth material characterization, using samples taken from both new material and real serviced gas turbine blades. Several solutioning heat treatments have been investigated in a window ranging from the theoretical γ’ solvus temperature and the original solutioning temperature used during blades manufacturing.

The assessment of the candidate rejuvenation heat treatments effectiveness is based on the evaluation of microstructure γ/γ’ restoration and the presence of recrystallized grains.
Numerical Method for Investigating Non-Ideal Flow Demonstrated on a Centrifugal Compressor Operating Near the Critical Point of CO2
Authors: Tegethoff Katharina , Borges de Almeida Carolina , Schuster Sebastian , Brillert Dieter
Published: August 2024

This paper focuses on the numerical investigation of the flow of CO2 in the so-called supercritical state (sCO2) through a centrifugal compressor by means of Computational Fluid Dynamics (CFD). The thermodynamic state of the fluid at the inlet of the compressor is characterised by its close vicinity to the critical point and the two-phase region. The low compressibility factors and high gradients of the flow variables marking this state region place high demands on the numerical methods used. First, a high accuracy in the description and evaluation of the thermodynamic state variables must be ensured. For this purpose, the modelling of the fluid as non-ideal is indispensable. Second, the numerical scheme must be robust against oscillations of the changes of state occurring in the course of the iterative solution, otherwise no converged solution can be obtained. This paper aims to contribute to the selection and utilisation of numerical solution methods for sCO2 applications in terms of stability and computing time efficiency. For this purpose, the flow solver TRACE, developed by the German Aerospace Center (DLR), was enabled to compute non-ideal compressible flows. By implementing an adapted Roe scheme, the GIRoe scheme, which is applicable to arbitrary equations of state, a converged solution can be achieved despite high gradients in the flow field and compressibility factors in the order of magnitude of 0.2. The use of state variables stored in the form of tables, which are evaluated based on the Tabular Taylor Series Extrapolation, leads to a reasonable computing time even for industrial applications. The presented methodology thus has the potential to enable the numerical investigation of single-phase turbomachinery flows of arbitrary working media and fluid states in a computationally efficient and numerically stable way.
Effect of Operational Pressure Reduction on Axial Compressor Performance by Means of 3D CFD Modeling at Nominal Operating Speeds
Authors: Galindo José , Navarro Roberto , Pallás Borja , Torres Germán , Lluesma-Rodríguez Federico , Antoranz Antonio
Published: August 2024

The hyperloop system constitutes one of the most promising alternative means of transportation for the next years. Nevertheless, there are still some challenges to face, such as the blockage of the air surrounding the pod inside the tube. To solve that, one proposal consists of including a compressor that helps to relieve the pressure conditions between the pod and the tube. Thus, this work makes, for the first time in this context application, a numerical analysis with CFD tools of the performance of the compressor under low Reynolds conditions by decreasing the pressure of the system until hyperloop operation values. By doing so, it is observed how the compressor performance slightly decreases with the pressure. From this point, the efficiency is severely affected until the point where the compressor is totally lost. The flow analysis supported this idea. Initially, at high Reynolds, the flow behaved completely turbulent, and almost no separation was observed in the boundary layer. Later, some separation started to appear, but the turbulent nature of the boundary layer allowed the reattachment of it. Eventually, it was observed how the laminar conditions of the boundary layer at low Reynolds constitute the main reason for the huge detachments that appear. Other aspects were also explored, such as the interstitial losses at the tip, which seemed to work in the opposite direction, that is, decreasing with the lower pressures, but being globally way less important than the losses generated by the flow detachment.

Therefore, this work suggests that decreasing the pressure could have a big impact on the propulsive system of a hyperloop vehicle, even opening the door to develop an ad hoc turbomachine for its purpose.
Performance Modeling and Analysis of Hydrogen-Fueled Aero-Engines
Authors: Wang Xiting , He Ai , Chen Zhixiong , Jiang Jincen , Liu Yuan , Hu Zhongzhi
Published: August 2024

Amid increasing global demands for carbon neutrality, hydrogen-fueled aero-engines are drawing significant attention due to their zero carbon emissions. To fully harness the advantages of hydrogen-fueled aero-engines, it is essential to design appropriate configurations, including the selection of combustion chambers and the placement of heat exchangers. To investigate this issue, this paper initially surveys ongoing global research programs in hydrogen-fueled aero-engines, summarizing the demands of hydrogen-fueled aircraft and the prevalent configurations of hydrogen aero-engines. Subsequently, to evaluate the merits and limitations of various engine configurations, a specialized simulation platform dedicated to the performance analysis of hydrogen-fueled engines was developed. This platform is equipped with modules specifically designed for hydrogen-fueled aero-engines, including hydrogen fuel, steam injection combustor, and hydrogen fuel heat exchanger modules. These components facilitate the modular assembly of diverse engine configurations, thereby enabling preliminary selection and optimization of engine configurations. Ultimately, employing this platform, the study constructs models of three prevalent hydrogen-fueled aero-engine configurations and undertakes a comparative performance analysis, assessing the relative strengths and weaknesses of each configuration under varied operational conditions, thus providing a robust foundation for future engine configuration design.
Impact of High-Temperature Radiation on the Heat Transfer Characteristics of Film-Cooled Guide Vanes in Gas Turbines
Authors: Wang Meng , You Ruquan , Li Haiwang
Published: August 2024

With the increase in pre-turbine temperatures and the development of cooling technologies, radiation is crucial in vanes’ designs. The present work investigated the radiative transfer of film-cooled guide vanes. Firstly, the impact of radiation on the optically thin and thick thermal boundary layers (TBL) was analyzed using the derived formulas from the microscopic perspective. The findings confirmed that radiation can significantly increase the TBL thickness and the heat transfer rate. When the radiation-convection dimensionless parameter was equivalent to one, the total heat transfer coefficient was approximately 3.76 times higher compared to the case of pure convection. Secondly, the heat loads on the guide vane were numerically solved from the macroscopic perspective, considering the radiation behaviors of the absorbing gases based on the wide band K-distribution model. The findings indicated that the cooling films not only acted as barriers to hot gases but also resulted in convective cooling of the guide vanes in adiabatic conditions. Surrounded by a 1800K environment, radiation can reduce the cooling effectiveness by up to 40%. In addition, the radiation had the most significant impact on the leading edge, and radiation protection at the leading edge is imperative to ensure optimal safety and performance. Subsequently, the measurement procedures for the environmental radiation heat flux on the test plate was first proposed to help quantifying the radiation influence. The conclusions of this work will assist in a clearer understanding of the radiative heat transfer behavior in film-cooled guide vanes.