bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Head-End Fuel Staging on Combustion Characteristics in a Multi-Nozzle Array Combustor
Authors: Liu Zhigang , Wei Xiaopo , Xiong Yan , Lu Xinggang , Zhang Zhedian , Zhang Shijie , Xu Xiang
Published: August 2024

Due to the need for enhanced gas turbine efficiency, the outlet temperature of the combustion chamber is increasing. Micromixed combustion (MMC) technology has been widely adopted in gas turbine combustion chambers to achieve low NOx emissions. In order to improve the performance of load regulation and inhibit thermoacoustic oscillations, this study investigates the effect of head-end fuel staging on the combustion characteristics of a multi-nozzle array model combustor through numerical simulations and experiments. The results demonstrate that employing different nozzle spacings effectively enables stable combustion. When only the pilot nozzle is operational, ignition stability is ensured by local flue gas recirculation zones from unit nozzles, as well as a large recirculation zone at the center of the combustion chamber. However, when both pilot and main nozzles are operational, expansion effects caused by high-temperature flue gas compress the central large recirculation zone. There is no significant impact on local flue gas recirculation zones between the pilot unit nozzles. The fluid dynamics within the model combustor guarantee its combustion stability and uniformity in outlet temperature under rated load conditions. NOx emissions are controlled through localized flue gas recirculation and flame lift-off mechanisms, which reduce the maximum temperature within the combustion chamber. The NOx emissions from this model combustor were found to be less than 25 ppm @15%O2.
Development and Characterization of EB-PVD Thermal Barrier Coatings With Different Ceramic Materials for Turbine Blades
Authors: Korkmaz Hanifi Eray , Güven Gökhan , Dikbıyık Alican , Yücesan Güven , Kazmanlı Kürşat
Published: August 2024

Thermal barrier coatings (TBC) are expected to exhibit specific properties, including low thermal conductivity, high thermal expansion capabilities, and excellent resistance to corrosion. Presently, yttria-stabilized zirconia (YSZ) is the prevailing choice for thermal barrier coatings, owing to its low thermal conductivity (approximately 1.5 W/m.K) and superior thermal shock resistance. YSZ can effectively insulate components at temperatures of around 1400°C and is also compatible with various ceramic materials, including Gd2Zr2O7, Nd2Zr2O7, Sm2Zr2O7, and La2Zr2O7.

Enhancements to thermal barrier coatings offer the promise of increased efficiency in gas turbine engines, as well as the extension of the service life of high-cost materials. In pursuit of these objectives, this research initiative primarily focused on the production of diverse ceramic materials, namely 7YSZ, Gd2Zr2O7, Sm2Zr2O7, Nd2Zr2O7, and 4Gd2O3 + 4Y2O3SZ coating materials, characterized by optimized production parameters. These materials were synthesized from their oxide forms utilizing the solid-state method. To facilitate the adhesion of these coatings to the CMSX-4 superalloy substrate materials, a bond coat consisting of Pt-NiAl was applied using the pack cementation and VPA (Vapor Phase Aluminizing) methods. Subsequently, the synthesized ceramic materials were deposited onto the CMSX-4 superalloy substrates through the Electron Beam-Physical Vapor Deposition (EB-PVD) technique. Comprehensive characterizations were then conducted on these coating structures.

Following the coating processes, scanning electron microscopy (SEM) analysis was conducted to evaluate coating thickness and morphology. Additionally, thermal conductivity, scratch resistance, and hardness tests were performed on the coated samples.
Effects of the Blade Tip Loading Distribution on Transonic Centrifugal Impeller Stability
Authors: Yang Bijie , Cao Teng , Hayashi Yoshihiro , Kanzaka Tadashi , Tomita Isao
Published: August 2024

Blade loading distribution is a crucial parameter for a compressor design. This study investigates the impact of the blade tip loading on transonic centrifugal impeller stability, comparing front-loaded and rear-loaded impeller designs through full annulus URANS simulations. Key findings reveal that the overall stability of the compressor relies on the interaction between inducer and exducer behaviors. The front-loaded design strategically shifts the inducer’s instability point to a higher volume flow rate where the exducer is more stable. It helps enhance the overall impeller stability but at the cost of efficiency. This is because different blade loading designs influence workload distribution within the inducer and exducer. The front-loaded design imposes higher inducer loading with early work input rollover and increased losses. This design better shapes its pressure-rise characteristics and extends stability, albeit with efficiency trade-offs. Detailed flow analysis shows that the front-loaded design intensifies tip-leakage flow, accelerating interactions and leading to earlier leading edge flow spillover. In contrast, the rear-loaded design displays a more stable tip-leakage flow, delaying the spillover and inducing early overall pressure-rise drop when the exducer’s stability is weakened. However, both designs converge in flow fields and performance characteristics when significant reverse tip flow occurs at low flow conditions.
A Computational Study of Temperature Driven Low Engine Order Forced Response in High Pressure Turbines
Authors: Trafford Alexander , Stapelfeldt Sina
Published: August 2024

This paper reports the results of computational studies of the effect of combustor exit temperature distortions on Low Engine Order (LEO) forced response of a High Pressure Turbine (HPT). Forced response of this kind occurs at frequencies below the Stator Vane Passing Frequency (SVPF) and can be a major cause of High Cycle Fatigue (HCF) in turbines due to its tendency to excite fundamental modes of vibration. This paper investigates the extent through which temperature distortions act as a forcing stimulus in HPT rotor rows, through measuring unsteady pressure and modal force magnitude recorded from full annulus unsteady simulations of the MT1 stage: a low temperature, unshrouded, HPT rig. Rotor relative incidence angle variations are shown to be the key mechanism through which temperature acts as a forcer in HPT rotor rows, whilst temperature driven forced response is shown to be dependent on the magnitude of the modal content of the upstream temperature waves. These findings are used to build a reduced domain tool for blocked burner forced response prediction, which is shown to be accurate to an RMS error of 2.66%, far beyond the current accepted standard for forcing prediction of this kind.
Numerical Demonstration for a Novel Design of High-Temperature Turbine Facility Enabled by Shock Tube
Authors: Fang Yizhi , Zeng Wei , Ma Haiteng
Published: August 2024

Reproducing the working environment of a gas turbine blade in laboratory has long been a challenge in the state of the art, but is crucial for scaling data from laboratory conditions to engine design point. Specifically, simultaneous matching of Reynolds number, Mach number and turbine inlet temperature in laboratory to those of engine design condition is scarcely achieved in the academic community. As an attempt to tackle this challenge, this paper introduces a novel design of high-temperature turbine cascade, whose mainstream gas is sourced from a shock tube so that high-enthalpy environment is fulfilled. To examine the feasibility of the rig design in obtaining reliable heat transfer data, numerical simulations are conducted, verified and validated against experimental data. Numerical results demonstrate that the new rig is able to produce a mainstream gas of 589±1 K for a test time of 9.5 ms. Nusselt number obtained during the test time agrees well the experimental data in VKI’s isentropic light piston tunnel. Besides, the test duration is sufficient for a steady boundary layer to establish. Furthermore, the new rig is shown to generate a total temperature of 1810±10 K at the cascade inlet for a test time of 1 ms. However, pseudo shock wave forms under this circumstance, greatly augmenting turbulence intensity at the cascade inlet and leads to an over-predicted Nusselt number compared to the experiment. Control of turbulence intensity at the cascade inlet (shock tube outlet) is required as a scope of the future work.
A Perspective on the Process and Turbomachinery Design of Compressed Air Energy Storage Systems
Authors: Maffulli Gianfranco , Grimaldi Angelo , McGillis Andrew , Succi Lorenzo , Przybytko Przemyslaw , Maceli Nicola , Brown David , Brook Graham , Earle Scott
Published: August 2024

The present paper will describe the Baker Hughes experience in the development of the turbomachinery equipment for Hydrostor’s Advanced Compressed Air Energy Storage A-CAES system.

At the core of a CAES plant there is an air compressing system, followed by an air expander used to recover the stored energy.

To achieve a reliable and effective solution, the expander is obtained from the architecture of Baker Hughes steam turbines, which was adapted to match the specific process needs. The criticalities that were addressed and solved to derive the expanders from the original steam turbine are presented.

Specifically, the paper describes the activities performed to optimize the inlet and exhaust sections of each segment, the development of the blades for high atmospheric volume flow, and the implications that thermal transients have on the machine reliability.

The inlet and exhaust sections were arranged according to the layout constraints, which were set to mitigate the effects of the thermal stresses and to reduce the weight to facilitate the machine transportation, while maintaining high aero-performance. As for the expander, a single-body configuration was selected to optimize capital expenditures and reduce leakage to atmosphere.

A new set of blades derived from Baker Hughes’s Steam Turbine stages were developed. This new stage is characterized by rotating blades with high radius ratio; therefore, an optimization strategy was adopted to include the mechanical constraints from the beginning of the design cycle and obtain a final geometry that can be used with different flow path and operating conditions. Finally, the 3D full Navier Stokes Computational fluid dynamics analysis was used to assess the performance of the new stages in nominal and off-design conditions.

A detailed analysis of the thermal transient of the expander parts with FEA methods was performed to assess the life expectations of the equipment. The FEA results are discussed in the paper to show the capability of the machine to sustain an extremely fast start up sequence.

Compressor train is characterized by a multiple body configuration. A detailed optimization was performed to improve the efficiency and the availability of the selected solution. The low-pressure axial compressor discharge section has been optimized to reduce losses and a detailed study of rotor has been performed to evaluate the capability to withstand a high number of start and stop cycles.
Residual Stress Optimisation for Manufacturing of a Nozzle Guide Vane in Mar-M-509 by Laser Powder Bed Fusion
Authors: Lani Sébastien , Pardhi Yogiraj , Ghasemi Hossein , Reinert Felix , Burn Andreas , Soothill Charles
Published: August 2024

This paper delves into the potential of Additive Manufacturing (AM) technologies, focusing on the utilization of Laser Powder Bed Fusion (LPBF) to optimize the manufacturing process for Mar-M-509, a Cobalt-based superalloy, in aeroderivative industrial gas turbine nozzle guide vanes. While Mar-M-509 offers exceptional properties for high-temperature applications, the rapid cooling rates inherent in LPBF introduce significant residual stresses, leading to poor success rates below 50%.

The study systematically addresses this challenge by proposing a comprehensive methodology to optimize LPBF parameters. By fine-tuning processing conditions, including elevating the powder bed and build chamber temperatures, the research achieved notable reductions in residual stresses by up to 55%. Computational simulations played a pivotal role in predicting deformations and thermal signatures, enabling proactive adjustments to process conditions, ultimately enhancing part quality and process reliability.

Validation through successful printing with a yield exceeding 75% underscores the effectiveness of this approach. Moreover, the study suggests the broader applicability of these optimization strategies beyond Mar-M-509, paving the way for advancements in AM techniques across diverse materials and industrial sectors.

This research not only presents a robust solution for mitigating residual stresses in LPBF-produced components but also showcases a proactive methodology that promises significant implications for additive manufacturing’s future advancements and applicability.
Unsteady Pressure Behavior on Blade Surface Induced by Wake-Blade Interaction in an Axial Compressor Stage
Authors: Zheng Xuedong , Wang Baotong , Li Jia’an , Yan Chuanxiang , Zheng Xinqian
Published: August 2024

Wake from upstream blades is a significant vibration excitation source in axial compressors. One needs to know how wake passing induces the unsteady pressure to design a more efficient and reliable compressor. This paper studies the pressure fluctuation caused by the wake of the upstream stator of an axial compressor stage using full annulus unsteady RANS (URANS) calculation. Wake-induced excitation is much stronger than downstream potential excitation and is more significant on the blade pressure surface. Along the chord length, near the leading edge, the noticeable unsteady pressure disturbance comes from a nonlinear interaction and propagates at 57% speed of the wake convective speed on the blade suction surface. The unsteady pressure at the suction and pressure surfaces are out of phase, which is believed to be induced by the incidence change from the negative jet effect; At the mid-chord, there are apparent unsteady pressure propagation patterns on both the pressure and suction surface, which are influenced by the blade number of rotor and stator. Moreover, the original case has a lump-shaped pressure disturbance distribution and propagates upstream. With the blade number changed, an obvious linear pressure wave pattern emerges, which is related to the cut-on/off condition between S0 and R1. When wake impinges on the downstream blade, the induced pressure disturbance will further cause the unsteady pressure fluctuation on the neighbor blade suction surface in the same row.

Based on these phenomena, it is concluded that the wake will input energy to the blade more efficiently through the leading edge. A large vibration amplitude near the leading edge should be avoided. Furthermore, reducing the leading edge separation bubble may mitigate the excitation. More importantly, the result indicates the nonlinear interaction induced by wake mainly happens near the leading edge, and the pressure interaction in the blade passage is almost linear.
Speed Strategy on High-Pressure Compressor for the Charging Process of Advanced Adiabatic Compressed Air Energy Storage During Dynamic Shutdown
Authors: Wang Yi , Qin Guoliang , Jia Cheng , Cui Qin
Published: August 2024

Advanced adiabatic compressed air energy storage (AA-CAES) starts and shuts down frequently. The default operation of the high-pressure compressor (HP) connected to the cavern is to reduce the speed of the inverter motor during shutdown. Whether or not the default speed strategy is safe has yet to be focused on. To this end, a detailed charging process comprising three series of centrifugal compressors with intercoolers was constructed within the framework of UniSim® Design. The safety measures were meticulously considered by integrating anti-surge circuits, vent valves, and check valves. PI controllers were allocated to the primary component to govern the shutdown procedure. The speed strategy of the HP inverter motor during the load shedding stage is the focus of research. Six speed strategies, including decreasing speed, constant speed, and increasing speed, were discussed, respectively. The discussion focused on changes made to air injection, inlet mass flow of the HP, inlet and outlet pressure of both the middle-pressure compressor (MP) and HP, and energy efficiency. The study found that implementing the minimum allowable speed for the inverter motor speed (IMS) and increasing speed during the load shedding stage can cause fluctuations in the air injection. As IMS increases at the end of the load shedding stage, the pressure anomalies at the MP outlet and the HP inlet weaken, and the shutdown process’s energy efficiency improves. The HP inlet flow fluctuations caused by various strategies were within an acceptable range. This study reveals that there is a mutual influence between components in the charging process of AA-CAES. An appropriate speed strategy for the HP inverter motor can mitigate the operational hazards. The results of this study can provide guidance for similar AA-CAES shutdowns.
Performance of Rough-Ribbed Low-Pressure Turbine Blades Under Varying Loading and Operating Conditions
Authors: S. M. Ananth , Nardini Massimiliano , Kozul Melissa , Vadlamani Nagabhushana Rao , Sandberg Richard D.
Published: August 2024

Recent research have demonstrated the effectiveness of riblets (streamwise aligned grooves) in reducing the profile loss of low-pressure turbine (LPT) blades under high-lift loading. In this research, we pursue the efficacy of riblets in reducing the blade profile loss under various design and off-design conditions. We adopt a strategy in which surface roughness is employed in the transitional regime to minimize the separation bubble-related losses and flush mounted riblets downstream to further mitigate the skin-friction drag and boundary layer losses due to an increase in the turbulent wetted area (TWA). Several high-fidelity scale resolving simulations are carried out to test the efficacy of this ‘rough-ribbed’ LPT blade for loadings ranging from low-lift (LL), high-lift (HL) and ultra high-lift (UHL) conditions. Furthermore, two exit Reynolds numbers - 83,000 and 166,000 pertaining to engine relevant design and off-design conditions, respectively, are considered. The streamwise evolution of skin-friction coefficient and boundary layer integral parameters are compared and contrasted among different test cases. The instantaneous flow features and second order statistics such as the Reynolds stress and turbulent kinetic energy are analyzed to determine the design and off-design performance of riblets. It is found that the efficacy of scallop-shaped riblets in reducing the profile loss improves with loading. Specifically, the net skin-friction reduction increases from 3.4% under LL to 8% under UHL loading at cruise Re. There is a corresponding reduction in the trailing edge momentum thickness (θTE) from 10% to 15%. A further reduction in θTE is attained from design to off-design Re under UHL loading. Thus the effect of riblets in reducing mixing losses improves with increasing Re. It is also found that the riblets reduce flow blockage due to boundary layers. Furthermore, the necessity to optimize riblet ramp to achieve skin-friction reduction under off-design conditions is highlighted.
Development and Validation of an Isolated Unsteady Diffuser Computational Model for a Vaned Centrifugal Compressor
Authors: Holtmann Benjamin , Shapochka Mark , Key Nicole
Published: August 2024

Recent advancements in computational technologies have greatly increased their ability to be applied to complex problems in aeroengine design. Computational Fluid Dynamics (CFD) is being applied to increasingly complicated systems, including centrifugal compressors, which are known for complex flow structures due to the compound curvature inherent in the flowpath. Modeling these flow fields is normally accomplished using mixing planes between the impeller and the diffuser, which are convenient due to their quick convergence and turnaround time needed for design iterations. However, the simplification of circumferentially uniform flow entering the diffuser of a centrifugal compressor may lead to incorrect design choices. In fact, the jet-wake characteristic of the impeller exit flow field leads to significantly unsteady nonuniform flow entering the diffuser.

While incorporating unsteady effects allows for greater accuracy, it is frequently not practical to run full-stage, unsteady simulations due to the significantly increased computational cost, especially when conducting multiple design iterations. Thus, the motivation of this paper is to develop a simplified diffuser model that incorporates unsteadiness from the impeller flow field without requiring a full-stage unsteady CFD simulation. Steady and unsteady isolated-diffuser computational models were developed for a vaned centrifugal compressor, which reduced the computational cost of unsteady CFD simulations, when compared to full-stage unsteady models. The isolated unsteady diffuser model used unsteady inlet boundary conditions from a full-stage, unsteady model. The model was validated with laser Doppler velocimetry (LDV) test data gathered from the Centrifugal Stage for Aerodynamic Research (CSTAR) facility in the High-Speed Compressor Lab at Purdue University. Validation of the isolated unsteady diffuser model showed it consistently performed similarly to the full-stage unsteady model when predicting total pressure, absolute velocity magnitude, and incidence. Additionally, both models closely matched LDV test data. Incidence at the shroud-side diffuser leading edge was still overpredicted. These results show promising signs of the isolated unsteady diffuser model to solve preliminary concepts in parallel, with good accuracy, before evaluating best performing ones in a more costly and high-fidelity, full-stage unsteady CFD model.
Evaluation of Data-Driven Classifiers for an Ignition Forecast of Large Gas Turbines
Authors: Lang Florian , Savtschenko Maximilian , Yadav Vikas , Ghani Abdulla
Published: August 2024

This paper demonstrates several supervised learning algorithms for ignition prediction of large stationary gas turbines (GTs), based on existing “real world” operational data. We obtain the data set from the mature SGTx-8000Hframe. In this work, we detect both successful and failed ignitions in advance based on various environmental changes. We test seven classification algorithms for their classification ability in the context of engine ignition: Random Forest (RF), Balanced Random Forest (BRF), Gradient Boost (GB), Gaussian Process Classifier (GPC), Multiple Logistic Regression (MLR), AdaBoost and Support Vector Machine (SVM). After a detailed pre-processing including data selection, cleaning and feature engineering, the modelling results are promising: The small fraction of 2% failed ignitions, in the presented data set, is correctly classified with high accuracy. In addition, we reduced the parameter space from 22 to 11 (for the fleet’s 60 Hz cohort) and to 14 (for the fleet’s 50 Hz cohort). In a further step, we reduced to 5 and finally to 2 features while maintaining the model’s accuracy, which boils down the model complexity by the application of 2 robust selection methods: The Pearson’s paired comparing of feature correlation and the Recursive Feature Elimination (RFE).

Starting with seven applied classification algorithms on the whole GT fleet’s data set (both 50 Hz and 60 Hz cohorts) we reduced the data set length to a single engine and applied the most promising classifiers accordingly. To check the “real world” applicability and thus the classifier’s performance on unseen data, we apply two different test scenarios: Firstly, we transfer the prediction map for successful ignitions of a 50 Hz GT with good accuracy to unseen data of a different 50 Hz GT. Secondly, we assist the commissioning engineers for the recommissioning after an overhaul of a 60 Hz GT. The algorithm’s recommendation led to constant successful ignitions on this specific test site covering various boundary conditions over the observation period of 2 years.
Performance Analysis of a Self-Decarbonizing Combustor
Authors: Akojwar Kartikeya S. , Pawar Samadhan A. , Chaudhuri Swetaprovo
Published: August 2024

Hydrogen is envisioned to be a key decarbonization solution for fossil fuel-dependent power generation and aviation industries. At present, a significant fraction of the generated electrical power is derived from natural gas. As such, the external energy needed for hydrogen generation, often sourced from fossil fuels, results in CO2 emissions, compromising overall carbon neutrality. Instead, the processes of hydrogen generation can be energetically coupled with the combustion process, in-situ, to eliminate external energy requirements. To that end, a novel self-decarbonizing combustor has been conceptualized, integrating methane pyrolysis with the combustion process that can in principle decarbonize many contemporary power generation technologies. The underpinning methane pyrolysis process enables in-situ pre-combustion capture of solid carbon. Consequently, CO2 emissions resulting from the combustion of processed, hydrogen-enriched fuel are mitigated. This study provides a comprehensive analysis, delineating the operating principle and the effect of some of the important governing parameters on the performance of the self-decarbonizing combustor. These parameters including fuel temperature, residence time, pressure, and catalysis are studied in the context of potentially applying the proposed concept to natural gas-based decarbonized electrical power generation. Investigating fuel chemistry, combustion exhaust, carbon structure and morphology under varying process parameters enhances our comprehension of this prospective technology. Additionally, the self-sufficient nature of the system, eliminating the need for separate hydrogen production, storage, and transportation infrastructure, highlights its potential as a scalable and achievable technology.
Experimental and Numerical Investigation of the Counter-Rotating DLR Turbo Fan Stage CRISPmulti With Boundary Layer Ingestion
Authors: Lengyel-Kampmann Timea , Charroin Guillaume , Meyer Robert
Published: August 2024

Boundary Layer Ingestion (BLI) has gained significant attention as a potential aerodynamic concept for improving the performance and efficiency of modern aircraft. It can significantly reduce the total pressure losses and, as a result, increase the propulsion efficiency of the engine. Enhanced propulsion efficiency leads directly to reduced fuel consumption [1,2]. Besides these above-mentioned benefits, the BLI has also some undesirable effects, like inhomogeneous inflow in the engine intake. This distorted inflow interacts with the rotating blades, which leads to increased blade vibrations, additional noise sources and unfavorable aerodynamic properties [3,4,5]. This study investigates the impact of BLI on the characteristics of the fan, focusing on pressure, temperature and velocity field. The comprehensive investigation of the application of BLI through a combination of experimental and numerical approaches to assess its influence on the fan behavior is presented in this paper.
On Intake-Compressor Interactions Within an Integrated Propulsion System
Authors: Rademakers Rudolf P. M. , Stößel Marcel , Kožulović Dragan , Niehuis Reinhard
Published: August 2024

The integration of a propulsion system into the airframe can contribute to the overall aircraft performance and is beneficial for military applications due to a reduction of the aircraft radar cross-section. On the other hand, engine integration calls for serpentine engine intake systems in which generally combined pressure-swirl distortions are provoked, which affect the performance of the propulsion system. The Military Engine Intake Research Duct (MEIRD) was designed to provoke a large-scale flow separation as well as a combined pressure-swirl distortion. The serpentine research duct is tested in both a remote- and close-coupled setup with the Larzac 04 turbofan engine to assess the aerodynamic interactions between the flow within the intake duct and the compression system. The upstream effect of the compression system on the steady-state duct flow is within the range of expectations. Less is known from the open literature with regards to the unsteady character of the flow in such a setup. Three distinct unsteady flow phenomena caused by the serpentine shape of the duct are identified up- and downstream of the low pressure compressor in the remote-coupled setup. An additional distinct low frequency unsteadiness is provoked with a configuration which features vortex generators for flow control. All phenomena are largely attenuated by the upstream effect of the compressor in the close-coupled setup. Nonetheless, the surge margin is massively reduced due to the inflow distortion and stall cells within the first stage of the low pressure compressor are visualized at high thrust settings of both the remote- and close-coupled setup, which are expected to impact the durability of the compression system.
Film Cooling Effectiveness Measurements on a CMC-Simulated Flat Plate
Authors: Thurman Douglas , Poinsatte Philip
Published: August 2024

Ceramic matrix composites (CMC) are high temperature materials that can allow higher operating turbomachinery engine temperatures with less coolant required. One method of fabricating ceramic matrix composites is by weaving fibers into the shape of an airfoil. Generally, CMC fiber tows are assembled with various weave patterns, but this uneven surface could introduce aerodynamic losses, and it will be necessary to determine the best film cooling hole arrangement for minimal thermal engine efficiency loss. As part of an effort to assess the impact of geometric constraints of CMC implementation relative to metallic high pressure turbine blades, an experimental study was performed to investigate the effect of film cooling on a CMClike surface roughened flat plate. Film cooling effectiveness measurements were acquired on a large-scale surface with a ceramic matrix composite weave pattern and on a smooth surface for comparison. A single row and a 2-row cooling hole arrangement were investigated with different hole sizes. Infrared thermography data was acquired at several Reynolds numbers and blowing ratios. Results showed that the effect on span averaged film cooling effectiveness was small between a weave surface pattern and a smooth surface, while hole spacing dependence had a much stronger effect.
Applying Rapid Qualification to Fatigue Assessment of a Binder Jet Superalloy
Authors: Scott-Emuakpor Onome , Johnson Philip , Forgiarini Mattia , Noronha Tim
Published: August 2024

A rapid fatigue testing capability is demonstrated as a viable qualification approach to expedite the development of materials and Additive Manufacturing (AM) processes. Specifically, this work explores accelerated vibration fatigue testing results of Binder Jet Mar M 247 specimens for short lead time decision-making associated with changes to a postprocessing step. Using a vibration bending fatigue test method, this study reached a conclusion on the effects of Tantalum getter contamination on fatigue performance in 34% of the time while covering a 5X greater cycles to failure range than standard axial test methods. Furthermore, comparisons show that the differences in the fatigue performances of the accelerated test method and standard tests can be quantified with a scalar factor. The results in this work and future development of low-cost accelerated testing products are promising for achieving rapid qualification of AM processes that benefits the advancement of gas turbine engine systems.
The Effect of Heterogeneous Natural Gas-Hydrogen Input Into F-Class Gas Turbine Combustor As a Combustion Optimization Method
Authors: Park Jungkeuk , Shin Jugon , Park Seik , Lee Sanghyup , Choi Nakjeong
Published: August 2024

The global push to combat climate change by transitioning to clean power generation is accelerating. One promising avenue involves utilizing low-carbon fuels like hydrogen and ammonia in place of conventional fossil fuels such as coal and natural gas, particularly in gas turbine-based combined cycle power plants. While hydrogen co-firing technology shows potential, its widespread adoption faces challenges like infrastructure readiness and cost. To address this, optimizing existing gas turbine engines for hydrogen compatibility becomes crucial. In our study, we propose a novel approach: varying hydrogen content between different nozzle groups in gas turbine combustors. Through experiments using the full-scale combustor of a commercialized F-class gas turbine model, we investigated the impact of heterogeneity or variations in hydrogen concentrations at the center and outer nozzles on combustion dynamics and emissions, comparing with the cases of the homogeneous natural gas only fuel and natural gas-hydrogen mixtures. Hydrogen co-firing increased NOx emission while decreasing CO2 emissions. The peak amplitudes of combustion dynamic pressure, especially in the frequency domain of 125∼245Hz, were linearly proportional to the co-firing ratio, with 41.2% increase observed for 30% co-firing ratio. To ensure stable gas turbine operation, the co-firing ratio should be limited. Our findings revealed a significant correlation between NOx emissions and combustion stability, and varying levels of heterogeneity. Moreover, under higher heterogeneity conditions with intensive hydrogen input into the center nozzle, improved hydrogen co-firing performance was observed, reducing the peak amplitude of the frequency domain limiting co-firing by 22% for 25% co-firing ratio. This potentially extended the critical hydrogen co-firing ratio. Thus, implementing heterogeneous natural gas-hydrogen inputs emerges as a promising method to enhance combustion stability and enable effective hydrogen co-firing, offering a pathway towards cleaner energy generation.
Potential of Pressure Slip Casted All-Oxide CMC Elements for Use in Gas Turbine Systems
Authors: Jung Fabian , Götte Johannes , Liu Yiou , Markus Timo , Gries Thomas
Published: August 2024

The progression of high-temperature materials for turbines is crucial for the more efficient combustion of conventional and synthetic fuels in modern gas turbines, which is key to enhancing plant efficiency and reducing exhaust gas emissions. In this context, all-oxide ceramic matrix composites stand out due to their superior oxidation stability and temperature resistance, essential for withstanding the demanding conditions in the hot gas sections of modern turbine systems. These materials offer advantages over their metallic counterparts, including reduced cooling requirements and extended operational lifetimes. However, adapting these ceramic composites for turbine applications requires the incorporation of complex continuous fiber reinforcements, significantly increasing the ceramic’s damage tolerance. The reinforcement architecture employed presents substantial manufacturing challenges, particularly in colloidal production processes. To address this, a novel 3D-braided reinforcement architecture has been developed, enabling a near-net-shape production of continuous fiber reinforced ceramics (CFCC) through pressure slip casting technology. This approach represents a diversion from conventional CFCC manufacturing, which typically involves single-piece productions, by integrating pressure slip casting with 3D braiding for improved scalability and flexibility.

To evaluate the potential influence of pressure slip casted ceramic composites, comprised by an Al2O3-YSZ-RBAO matrix system and reinforcement by 3M Nextel 610 alumina fibers, on gas turbine systems, a thermomechanical model has been developed. This model is instrumental in calculating the material’s performance when applied to vital components of the gas turbine’s hot gas section. Therefore, it enables the prediction of the composite structure’s equivalent properties.
Reduced Order Model for Cavity-Based Combustors Describing Various Bifurcations As Cavity Size Is Varied
Authors: Singh Ashutosh , Nair Vineeth
Published: August 2024

In trapped vortex combustor (TVCs), where a cavity is used for flame stabilisation, large-amplitude periodic pressure fluctuations can occur at certain operating conditions due to flow-acoustics lock-in. In the present study, experiments were carried out in a laboratory-scale trapped vortex combustor by varying cavity sizes (L/D = 0.75–2.65). Unsteady pressure measurements reveal a bifurcation route of limit cycle → steeper limit cycle (with higher harmonics) → quasi-periodic → strange non-chaotic attractors (SNAs) → chaos as cavity size is increased (L/D). This overall transition leads to a 70% reduction in pressure amplitude and as such can be treated as a passive control strategy to mitigate unwanted oscillations. We employ a reduced-order model that incorporates this flow-acoustic lock-in. This model includes a feedback mechanism that accounts for the influence of acoustic modes on the vortex-shedding event. This feedback mechanism induces changes in the timescale of vortex impingement as cavity size varies, leading the system through the experimentally observed non-linear regimes. We validate our model by comparing its predictions with experimental results, highlighting its ability to capture the intricate dynamics observed in cavity-based combustors.
Retracted: “Quantitative Measurement of the Sauter Mean Diameter in Dense Fuel Sprays Using Simultaneous Planar-Laser-Induced-Fluorescence/Mie-Scattering Technique” [ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition, Volume 3B, June 24–28, 2024, London, United Kingdom, Conference Sponsors: International Gas Turbine Institute, ISBN: 978-0-7918-8795-0, Copyright © 2024 by ASME. Paper No: GT2024-128559, V03BT04A037, 9 pages; DOI: https://doi.org/10.1115/GT2024-128559]
Authors: Wu Guohua , Yu Xin , Peng Jiangbo , Cao Zhen , Song Yingjie
Published: August 2024

This paper was removed at the author’s request on December 9, 2024.
Experimental Investigation of Discharge Coefficients of Double Wall Cooling Systems
Authors: Xu Guangyao , Du Qiang , Xu Qingzong , Wang Pengfei , Li Hongye , Liu Haoyang
Published: August 2024

Double wall cooling technology is considered to be the most promising solution for next-generation gas turbine blade cooling, featuring enhanced cooling performance, reduced coolant air consumption, and a more uniform distribution of thermal stress. However, interactions in a double wall cooling system exist among the flow disturbance elements such as impinging jet, film cooling, and pin fins. Meanwhile, the arrangement and geometric parameters of the impingement/film in the double wall are different from those of traditional cooling. As a result, the flow resistance characteristics of each component are not independent of each other. Therefore, to accurately predict coolant air consumption within a double wall cooling system, this study focuses on the influence of geometric and flow parameters on the flow resistance of double wall effusion cooling system through experimental methods. The findings showed that the hole spacing, film hole inclination angle, and the number of pin fins have a significant impact on the discharge coefficient in double wall cooling. Furthermore, the internal crossflow severely affects the flow through the film cooling holes, resulting in a noticeable decrease in the overall discharge coefficient of the double wall system.
Thermodynamic Analysis and Optimization of an Innovative Closed Loop Brayton Cycle Fueled With Hydrogen
Authors: Ancona Maria Alessandra , Bianchi Michele , Cavuoti Bruno , De Pascale Andrea , Melino Francesco , Peretto Antonio
Published: August 2024

The growing attention to the reduction of fossil fuels dependency in the energy sector has led to an increase in the efforts to improve the renewable energy sources exploitation. Wind and solar generation is constantly growing worldwide but their fully exploitation is strictly dependent on the availability of efficient electrical storage systems.

In this context, hydrogen production, by the means of electrolysis processes powered by renewable generators, is an important option which is gaining increasing attention both from academia and industrial side. The conversion of hydrogen into electricity can be realized using fuel cells. However, these systems are not suitable for fast load changes. This aspect limits fuel cells’ ability to smooth out overgeneration issues.

In this paper, an innovative closed-loop Brayton cycle integrated with an electrolyser is presented and described. The whole system is conceived as an electrical storage device in which the closed-loop Brayton cycle represents the discharging phase of the electrical energy converted and stored into hydrogen. The paper analyses this novel cycle under the thermodynamic point of view performing the optimization of the main parameters and evaluating its efficiency and performance in comparison with others electrical storage devices. The innovative contribution of the paper, compared to available literature, lies in the valorisation of the oxygen stream (usually discharged into the ambient) from the electrolyser in the Brayton cycle and in the recovery of the water vapour from the gas turbine.
On Hysteresis in a Variable Pitch Fan Transitioning to Reverse Thrust Mode and Back
Authors: Vitlaris Dimitrios , Rajendran David John , Tunstall Richard , Whurr John , Pachidis Vassilios
Published: August 2024

A novel hysteresis phenomenon during the transition to and back from the reverse thrust mode in a Variable Pitch Fan (VPF) is identified and characterised in this work. This is done by using a three-dimensional (3D) fully transient Unsteady Reynolds-averaged Navier-Stokes (URANS) with the transitioning fan blade aerofoils simulated by an adaptation of the mesh displacement method. A “real-time” simulation of the complete VPF hysteresis loop is achieved by specifying a blade wall motion through an Eulerian rotation matrix in differential, gradual steps, that is combined with a mesh probe-and-update routine for improved numerical accuracy and stability. The VPF is modelled to be transitioning in a modern 40000 lbf geared high bypass ratio turbofan engine architecture at “Approach Idle” engine power setting in a typical twin-engine airframe with the flaps, slats, and spoilers set for an aircraft touchdown airspeed of 140 knots.

The transition to reverse thrust mode involves flow starvation into the engine, formation of recirculation zones in the bypass duct and the establishment of the reverse stream, all of which occurs in the opposing presence of the free stream flow at aircraft touchdown velocity. The transition back to forward flow mode involves the gradual re-establishment of the free stream which is opposed by the presence of the reverse stream within the engine. It is quantified that in the transition to reverse thrust, the blockage develops with a larger time delay than the disappearance of the blockage during the transition back due to the interplay of the temporal dynamics of fan blade motion and flow field response. The details of the changes in the flow field behaviour, the effect of engine power setting and aircraft touch down velocity on the hysteresis behaviour are explained in detail in the paper. Additional manifestations of the hysteresis phenomena at reverse thrust involving engine spool-up and down, and aircraft acceleration-deceleration manoeuvres are also explored. The hysteresis phenomena described in this work are critical in properly developing control schedules to adapt for potential bi-stable flow field development during the landing run. The study addresses another part of the puzzle in exploring the feasibility of reverse thrust capable VPF engines for future sustainable aircraft to reach aviation climate neutrality.
On Leakage Flows in a Liquid Hydrogen Multi-Stage Pump for Aircraft Engine Applications
Authors: Lamprakis Dimitrios , Rajendran David John , Santhanakrishnan Mani , Coskun Seyfettin , Roumeliotis Ioannis , Pachidis Vassilios , Yates Martin
Published: August 2024

A comprehensive operational characterisation of a representative, Liquid Hydrogen (LH2) aircraft engine pump, a key enabler for future hydrogen aviation, is presented in this work. The implications of leakage flows are investigated in a 2-stage, high-pressure pump for a wide range of flow rates and rotational speeds, through 3D (U)RANS simulations. The study compares two configurations: a baseline model comprising the primary flow path components — inducers, impellers and volutes and a realisable pump hardware that includes hub, shroud and power unit cavities. Performance metrics, including head changes and efficiencies, are extracted both at a component and system level. Leakage flow rates of 27.6% and up to 92.9% of the overall pump flow rate are recorded at design and lowest flow points respectively. The head loss in the mid to low flow rates does not exceed 4.5%, but the efficiency diminishes by up to 13.5% at off-design operation. The component analysis indicates significant penalties in impeller efficiency. At high flow rates, the presence of leakage flows improves the overall pump performance by 43% and 27% in head rise and efficiency, due to reduced losses in volutes and connecting ducts. The detailed characterisation of pump behaviour described in this work is of importance in development of safe, reliable and predictable design of aircraft LH2 pumps. These aircraft pumps are different from LH2 pumps utilized in rocketry and for cooling in nuclear industry due to the requirement to operate with wider turn-down ratios and often at low specific speeds. Therefore, this study addresses design considerations in this enabling technology that ensures the delivery of pre-conditioned fuel according to the aircraft operating conditions.
Creep Properties of Nickel Alloys - Comparison Between Conventional and Laser Powder Bed Fusion Manufacturing Routes
Authors: Megahed Sandra , Okabe Erina , Kraemer Karl Michael , Kontermann Christian , Heinze Christoph , Oechsner Matthias
Published: August 2024

PBF-LB/M (Metal Laser Powder Bed Fusion) is a commonly used additive manufacturing process for gas turbine parts. This manufacturing method allows for small quantity batches with complex part designs. The mechanical behavior of PBF-LB/M components is strongly influenced by manufacturing process parameters, such as component geometry, build orientation and post-processing steps. However, these complex correlations are not completely understood — especially not for high temperature applications. The number of publicly available publications on creep properties of nickel-based alloys is limited. This knowledge gap affects the design and qualification effort of PBF-LB/M gas turbine components.

This study compares the creep properties of conventionally and additively manufactured IN738LC and IN718. The assessment of PBF-LB/M additively manufactured samples includes experimental data from two types of specimens (witness and extracted samples) in three build orientations. Extracted samples out of additively manufactured components allow the investigation of application relevant mechanical properties. Build directions studied are 0° (perpendicular to build direction), 45° (diagonal) and 90° (parallel to build direction).

The results show that the creep properties of PBF-LB/M manufactured IN738LC at 850 °C are affected by build orientation. Samples oriented parallel to the build direction show favorable creep properties, especially 45° build orientations have reduced creep life properties.

In comparison, the influence of build orientation is not as critical in IN718 and creep life properties at 650 °C are slightly superior to conventionally manufactured samples.