Keywords: Others (Materials and Manufacturing Technologies)
Abstract: There is increasing pressure on the aviation industry to prioritise investment in green technologies that firstly produce reductions in CO2 emissions, and secondly, reduce noise [1]. Modern gas turbines, notably high bypass ratio turbofan aircraft engines are continuously evolving to provide improved efficiencies for reducing fuel consumption and consequently, CO2 emissions [2, 3]. This presentation will focus on new advanced material and manufacturing technologies that enable efficiency improvements across a wide range of components for current and future large civil engines. One critical aspect is the use of high temperature materials and coatings for improvements in thermal efficiency. However, higher temperature operation, particularly for fast climb cycles can have adverse effects of component durability. The balance between efficiency and durability will be discussed with reference to intelligent cooling systems, robust component design and a full understanding of material behaviour. Other efficiency improvements will be highlighted such as those gained from advanced component manufacture, improved factory efficiency and a greater emphasis on sustainability through reduced material usage, improved material manufacturing yields, waste elimination, material recycling and component repair. Finally, a view of future green technologies for powering aviation will be shown.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Computational Fluid Dynamics, Combustion Phenomena
Abstract: Rotating detonation provides a new method for ammonia combustion in a gas turbine. In this work, single-wave mode rotating detonation is obtained in the annular combustion chamber using three-dimensional numerical simulation. It is difficult for ammonia and air to form stable detonation waves in the annular combustion chamber under conventional gas turbine inlet conditions, so a certain amount of hydrogen should be added to improve the activity of the fuel, so that the detonation waves can propagate self-sustaining.

Keywords: Combustor Development, Combustion Simulation
Abstract: Large eddy simulation (LES) using a flamelet model coupled with an artificial neural network (ANN), namely the LES/flamelet/ANN is applied to supercritical oxy-fuel combustion and its validity is investigated. A high-dimensional flamelet library for non-adiabatic three gas stream condition of the supercritical CO2 combustor requires a large memory size that can exceed the memory capacity of general computers. Therefore, an ANN is applied to reproduce the combustion properties by replacing conventional flamelet tabulation techniques, which significantly reduce the required memory size. The validation of LES/flamelet/ANN was previously investigated in our previous work [1]. In this study, the LES is applied to the supercritical CO2 combustor at the actual operation condition for further validation of the LES. The results show that the predicted combustor outlet temperature agrees with the measurement, which suggests that the LES/flamelet/ANN is capable of predicting the supercritical combustion behavior.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustor Development, Combustion Simulation
Abstract: To design a low-emission hydrogen-fired gas turbine combustor, prevention of flashback is one of key issues. However, the detailed measurement of flashback is difficult and expensive, especially at the actual operation condition. Therefore, the high-precision numerical simulation technology is important to study the mechanism and countermeasures of flashback. In this study, A large eddy simulation (LES) employing a non-adiabatic flamelet generated manifold (NA-FGM) approach, which can account for the effects of heat loss, is applied to hydrogen-air premixed flame propagates in a rectangular channel. Then, the validity of predicting flashback limits is examined. The results show that the NA-FGM approach captures the trends of flashback limits variation during the experiments. This suggests that capturing such a sensitive changes of flame behavior by heat loss is important for accurately predicting the flashback in developing a low-emission hydrogen gas turbine combustor.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustion Simulation
Abstract: This work presents a two-dimensional direct numerical simulation study (2D-DNS) on the auto-ignition behavior of oxygen-enriched ammonia non-premixed flames under gas turbine conditions. In particular, three different oxygen-enriched fractions (0.25, 0.3, and 0.35) in the oxidizer stream are considered, and air condition is also calculated as a reference. The detailed mechanism developed by Shrestha et al. (Shrestha et al., Pro. Combust. Inst. 38 (2) (2021) 2163-2174) is used to account for the gas-phase chemistry. Species diffusivity is considered a mixture-averaged approach. It is found that there are three phases in the auto-ignition process: inert mixing, pre-ignition, and flame propagating phases. Increasing oxygen concentration in the oxidizer stream can significantly shorten the periods of inert mixing and pre-ignition phases, resulting in an obvious reduction in the ignition time. In addition, the combustion intensity and the subsequent flame propagating process can also be enhanced.

Keywords: New Testing Technology, Axial Compressors, Others (Aerodynamics and Design)
Abstract: This paper presents the recently commissioned test rig for fan intake interaction at the propulsion test facility (PTF) of the “Institute of Jet Propulsion and Turbomachinery� (IFAS) at TU Braunschweig. The rig enables innovative research in propulsor aerodynamics of modern ultra-high bypass ratio (UHBR) engines in combination with the unique architecture and cross wind capability of the PTF. In the publication, the potential of the ”Integrated Nacelle Fan Rig assembly� (INFRa) is presented by comparing the design data with the first experimental results, which have been gathered during the commissioning campaign. Additionally, the approach of determining the fan pressure ratio and mass flow with the given instrumentation of the test vehicle is described.

Keywords: Acoustic Issues, Advanced Measurement Techniques
Abstract: Three-dimensional background-oriented schlieren (3D-BOS) is a technique for optically measuring instantaneous 3D density fields. Further understanding of the measurement characteristics of 3D-BOS, especially its spatial resolution, leads to detailed physical discussions based on the density distributions obtained. As an example of such studies, we report an investigation of the spatial resolution in 3D-BOS measurements of a supersonic round jet, which simulates the exhaust of jet or rocket engines. In experimental 3D-BOS measurements of the jet, fluctuations with azimuthal wavenumbers up to about 10 are observed on a cylindrical surface extended from the nozzle lip. We created model data of cylindrical distributions with various azimuthal wavenumbers, and conduct projection-and-reconstruction tests for the 3D-BOS layout used in the experiments. The results show that the present 3D-BOS layout can resolve fluctuations with the azimuthal wavenumbers up to about 20. This indicates that the observed jet fluctuations are within the range of the resolution capability of the current 3D-BOS system.

Keywords: Centrifugal and Mixed-Flow Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control, Advanced Measurement Techniques
Abstract: In a compressor, shock waves are generated when the impeller blade velocity reaches supersonic speed relative to the air drawn in from the air inlet. The shock interacts with the tip-leakage vortex and the boundary layer on the impeller blade surface. The interactions cause the pressure rise and the reverse flow. Thus, it is important to predict the formation of shock on the blades in compressor design. This study focused on a position of the shock in a centrifugal compressor. In general, simultaneous measurement by multiple pressure sensors is necessary to measure the angle of the shock formed near the leading edge of the impeller blade. In this study, a pressure history was measured at a single point near the leading edge of the blade using a semiconductor pressure transducer. The semiconductor pressure transducer has a diaphragm onto which a semiconductor strain gauge is glued. The pressure acting on the diaphragm is proportional to the strain at the center of the diaphragm. The direction of maximum principal strain of the diaphragm coincides with the direction in which the shock passes over the diaphragm or its perpendicular direction. The strains in three different directions on the diaphragm were obtained and the direction of maximum principal strain was calculated using Rosette analysis. Finally, the angle of formation of the shock wave generated in the centrifugal compressor impeller was estimated.

Keywords: Reliability and Maintenance
Abstract: The method of recording damage information on a two-dimensional (2D) exploded view, in general, has the advantage of allowing an inspection record to be easily prepared. On the other hand, it has issues in terms of the fidelity of damage positions recorded on the exploded view and the precision of ex-post analyses of damaged regions. As such, technology for saving inspection records as three-dimensional (3D) digital information is sought after. Mitsubishi Heavy Industries, Ltd. (MHI) has developed technology for obtaining and recording the areas and photograph textures of damaged regions by reproducing the position/orientation of the photo (camera) of an object to be inspected on a 3D CG (Computer Graphics) space and projecting the damaged regions indicated on the photo and the photo on the target 3D CAD (Computer Aided Design) model. This technology allows preparation of a 3D digital inspection record with the same workload and equipment as those required for preparation of a 2D inspection record, thereby improving quality control.

Keywords: Electric/Hybrid Propulsion, New Aircraft Propulsion Concepts, Others (Combustion, Fuel and Emissions)
Abstract: In this study, the potential of combining pressure gain combustion (PGC) and a hybrid electric propulsion system (HEPS) to improve the performance of a commercial aircraft engine is investigated. Various engine configurations based on a reference turboprop engine benchmarked against the PW127 by Pratt and Whitney are simulated. Fuel consumption, energy demands, and efficiency for different levels of hybridization and pressure gain parameters are analyzed accordingly. Results show that an increase in the degree of hybridization (DoH) leads to a more stable fuel consumption during takeoff, while a rotating detonation combustion (RDC), as a PGC, can contribute to a reduction in fuel and energy consumption throughout the mission. Furthermore, the combined application of PGC and HEPS results in reduced CO2 emissions. This research demonstrates the potential of these emerging technologies to enhance the efficiency and improve the environmental impact of aviation propulsion systems.

Keywords: Electric/Hybrid Propulsion, Reliability and Maintenance, Operational Flexibility
Abstract: This study aims at analysing hybrid-electric operation of a two-spool high-bypass turbofan for a narrow-body aircraft during the climb trajectory. Boundaries of safe hybrid-electric operation are investigated and methods for controlling the electric power along the trajectory are demonstrated. This is crucial, as hybrid-electric operation induces throttling of the low-pressure compressor and the effect intensifies with increasing altitude during climb. Furthermore, operational loads are extracted and applied to lifetime prognostics for the turbofan engine, electric machine and power electronic system.

Keywords: Electric/Hybrid Propulsion, Aircraft Electrified Propulsion, New Aircraft Propulsion Concepts
Abstract: This publication presents a comprehensive study on the potential of hybrid-electric propulsion systems for regional aircraft, with a focus on a design range of 400 nm. The study employs a multidisciplinary approach to analyze the hybrid-electric powertrain architecture, integrating different aircraft disciplines and their interrelationships. A conventional and a series hybrid-electric architecture are built and optimized using OpenConcept, an open-source aircraft conceptual design library. The study conducts mission-level assessments to calculate high-level objectives like fuel burn and energy consumption. Results show that the series-hybrid architecture is a promising solution to significantly reduce fuel and energy consumption, while meeting the regional traffic market's requirements. The study also examines different mission ranges to highlight the effect of energy storage technology maturity on the potential of hybridization. The findings provide valuable design insights, demonstrating the potential of hybrid-electric propulsion systems for regional aircraft in reducing environmental impact and improving efficiency.

Keywords: Electric/Hybrid Propulsion, Aircraft Electrified Propulsion
Abstract: Despite the impact of COVID19, the demand of global aviation is expected to increase in the long run. At the same time, however, there is an urgent need to reduce the emissions of carbon dioxide. A lot of researchers and companies around the world are proposing advanced technologies such as distributed propulsion, electric propulsion, boundary layer ingestion, blended wing body and aircraft concept using them. In our laboratory, research about all turboelectric has been conducted but it revealed that the requirement for electric component was severe. Therefore, the objective of this research is to move this research forward and find the feasible solution. The research about Partial Turboelectric was conducted. It turned out to have a potential to reduce 1~2% Mission Fuel Burn compared to Turbofan and All Turboelectric.

Keywords: Computational Fluid Dynamics, Axial Compressors
Abstract: This paper presents applications of an immersed boundary (IB) method for internal-flow problems at high Reynolds numbers. A hybrid mesh strategy, with a single-block and structured mesh to fit the physical domain and an IB method to model the internal walls, is adopted to the internal-flow problems. To achieve this, the IB method is modified to determine the forcing point locations when large-aspect-ratio cells are involved near the walls. This extends the IB method to curvilinear grids so that the domain boundaries can be resolved by a body-fitted mesh, which significantly reduces the total cell number needed to resolve the boundaries compared to the usage of a Cartesian grid, and thus improve the computational efficiency. The present methodologies are firstly validated by a 3D subsonic compressor cascade. This case study shows that the present method can achieve the same overall accuracy for the pressure distribution with the traditional body-fitted simulation at the attached-flow regions. Further, the method is employed to predict the aerodynamic damping of an oscillating cascade, and the results also show good agreement with the experimental data, indicating the present methodologies are also capable of dealing with moving-boundary problems in internal-flow conditions.

Keywords: Computational Fluid Dynamics, Axial Compressors
Abstract: The trend for the engine design goes to smaller core engines to increase the bypass ratio and reduce the weight. With the decrease of core engine size, also the Reynolds Number decrease locally.This leads the focus within the design process of the axial compressor on the accuracy of the numerical models which are used for the simulation. Therefore, an experimental and numerical study was carried out to evaluate the state-of-the art design process for axial compressor bladings concerning the low Reynolds number effects within the flow. As study approach a linear cascade was used. Whereby the experiments were performed at the Transonic Cascade Wind Tunnel TGK of the DLR in Cologne and for the numerical simulations DLR in-house flow solver TRACE was conducted. The investigation was carried out at an inlet Mach number of 0.60 and a Reynolds number of 150.000. The comparison shows a significant discrepancy which is based on the current weakness of the turbulence and transition modeling at a RANS simulation. This result is based on a detailed description of the detected flow effects and is extensive discussed in the paper. Finally, an LES simulation is used for comparison to evaluate the possibility of using scale-resolved simulation techniques in the design process.

Keywords: Computational Fluid Dynamics, Others (Aircraft Engines)
Abstract: Sand erosion occurs in compressors and severely deteriorates the aerodynamic performance due to the eroded surface shape. Therefore, numerical simulations of sand erosion by constant or distributed particle sizes have been conducted as well as experiments. However, the effect of particle fracture in the sand erosion phenomenon has not been clarified. This study performed numerical simulations of sand erosion with and without particle fracture in a multi-stage compressor using UPACS. As a result, we confirmed that particle fracture affects the erosion behavior and the particle trajectories in the downstream stator and rotor passages of the multi-stage compressor. The present study indicates that particle fracture is needed to improve the accuracy of erosion prediction.

Keywords: Acoustic Issues, Computational Fluid Dynamics, Axial Compressors
Abstract: In this study, the shock noise generated by the NASA rotor 37 is simulated with a computational aeroacoustic solver developed by the present authors. The high order spectra difference scheme on hexahedral element is used for spatial discretization, and the Low Dissipation Low Dispersion Runge-Kutta method is utilized for time marching. A sliding mesh method is adopted for the data communication between the rotating and stationary mesh. The pressure disturbances upstream of the rotor are sampled and analyzed. The characteristic of shock noise generated by the rotor is presented and analyzed.

Keywords: Axial Compressors, Others (Aerodynamics and Design), Computational Fluid Dynamics
Abstract: An efficient and reliable stall inception prediction model is estab-lished and integrated into the compressor design, which is employed to investigate the effects of rotor and stator blade loading distributions on compressor stability. Four single-stage compressors with different rotor/stator blade loading distributions are designed by redistributing the circulation at the blade region and keeping the total work un-changed during the through-flow design. The steady simulations for these cases show that the static pressure rise coefficient and adiabatic efficiency of the two compressors with aft-loaded stator blades are remarkably better than the others with fore-loaded stator blades at small mass flow points. The compressor with aft-loaded rotor has a slightly better performance compared with that with fore-loaded rotor. The stall inception prediction via the developed model indicates that the rotor loading distribution has a significant impact on compressor stability, while the stator loading distribution has little impact. What’s more, the stability of the two compressors with aft-loaded rotors is better that those with fore-loaded rotors. The theoretical conclusions and the model precision are validated by experiments.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control, Computational Fluid Dynamics
Abstract: In this paper, using a high-speed multistage compressor simulating the rear stage of a gas turbine compressor for power generation, the effects of three different rotor tip clearances on performance, operating range and internal flow structure were investigated by numerical analysis and experiments. Although spike-type stall inception was confirmed before surge, the generation of modal inception was confirmed before the spike generation in the condition with large tip clearance. The static pressure measurement on the stator surface by the metal 3D printer shows the tip suction surface separation. The unsteady numerical simulations also suggests that tip corner separation occurs at the stator suction surface, propagates in the direction of rotor rotation, and generates a modal waveform. The results of multi-point unsteady measurements on the rotor blade tip casing shows that spike occurs and propagates to adjacent blades, leading to the spike inception. These flow mechanism shows modal and spike stall inception.

Keywords: Unsteady Flow and Stability Enhancement in Compressor Flow Control, Computational Fluid Dynamics, Axial Compressors
Abstract: Recently, in response to the increasing environmental awareness and demands of operational flexibility, gas turbines for power generation must comply with exhaust gas regulations, not only at rated operation but also at partial-load conditions. To improve emission performance of constant speed single-shaft engines at partial-load conditions, compressors should be operated with low mass flow rate to optimize air-fuel ratio of combustors. Flow rate of constant speed compressors can be reduced by controlling angles of variable vanes. Under these conditions, flow separation can be induced and it causes flow induced vibration and noise. They limit stable operation range of gas turbines. Thus, in this study, the way to predict the unstable behavior of compressors is investigated using unsteady flow simulation. The accuracy of the simulation is validated by utilizing a gas turbine test-rig. The way to enhance the stable operation range by optimizing the angles of variable vanes is also investigated.

Keywords: Unsteady Flow and Stability Enhancement in Compressor Flow Control
Abstract: Compressor blades face various vibration problems during the operation process, such as flutter, forced response, and nonsynchronous vibration. These vibrations can cause blade fatigue, resulting in a shortened blade lifespan, which is well-known. However, there is little knowledge about the influence of blade vibration on near-wall flow. In this study, a controlled diffusion compressor blade was used as the research object, and the effect of vibration on the flow separation and transition on the blade surface was investigated through large eddy simulation (LES). The vibration perpendicular to the chord direction was actively applied to the blade in this study, and the flow behavior near the surface of the blade was compared at different vibration frequencies. Even in the case where the vibration amplitude is very small, the vibration perpendicular to the chord direction can still effectively suppress the flow separation on the pressure side of the blade.

Keywords: Centrifugal and Mixed-Flow Compressors, Structural Vibration and Damping, Performance of Turbocharger and Small Gas Turbine
Abstract: The reduction of vibratory stress induced by unsteady fluid-structure interactions in turbomachinery is indispensable to avoid high cycle fatigue. The purpose of this study is to discuss the reduction effect of blade vibratory stress in centrifugal compressors produced by changing geometric parameters, the radial distance between the impeller and the vaned diffuser, and the diffuser vane height. The reduction effect was evaluated experimentally and analytically. Moreover, the impact on aerodynamic performance changing the parameters was also investigated. The radial distance showed a larger effect on blade vibratory stress, which was approximately 50%. While, changing diffuser vane height showed nearly 20% of reduction effect. It was found that there is a trade-off relationship between aerodynamic efficiency and vibration reduction effect.

Keywords: Centrifugal and Mixed-Flow Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control
Abstract: The behavior of low frequency fluctuations occurring in a centrifugal compressor with vaned diffuser were investigated by experiment and numerical analysis. It was confirmed that low-frequency fluctuations occur before the stage stall occurred in the tested centrifugal compressor. Both experimental and numerical analysis reveals that five of these fluctuations occurs within the diffuser passages. The experimental investigation showed that these five disturbances rotated in the direction of impeller rotation at 1.8%N, and the numerical analysis showed that they rotated at 2%N. The experimental results showed that the radial velocity decreased at the hub and shroud sides and the incidence angle increased in the low mass flow region. These five rotating disturbances are caused by leading edge separation on the suction surface of the diffuser vanes, which causes blockage in the diffuser passage.

Keywords: Centrifugal and Mixed-Flow Compressors, Others (Aerodynamics and Design)
Abstract: The aerodynamic instability of a compressor has a strong relationship with both the characteristics of pipe system and the compressor itself. In this paper, an experimental study was carried out on a combined compressor consisting of an axial stage and a centrifugal stage. The unsteady flow behavior in the compressor at 90% design speed were obtained using fast-responding pressure probes. The results show that the compressor came into surge directly without rotating stall observed. Besides, a novel mild surge phenomenon can be observed with a coupled pressure oscillation including the low-frequency and high-frequency waves, rarely reported in the axial or centrifugal compressor. The frequency of the lower one has the order of Helmholtz frequency of the compression system, while the other has a higher order. Therefore, the coupled mild surge could cause wide-frequency aerodynamic loads on the blade and shaft system, which should be considered in the compressor system integrity design.

Keywords: Centrifugal and Mixed-Flow Compressors, Turbines, Gas Turbines for Electric Power Generation
Abstract: ABSTRACT The emergency gas turbine generator provided by IHI Power Systems is a device for instantaneously supplying a large amount of power in the event of a power outage. Installed in data centers, public facilities, water supply facilities, etc., they play an important role in delivering safety and security to people and society. In recent years, the need for large capacity is increasing. To address this, we have developed compressors and turbine blades for high output that can increase the output of 2MW class gas turbine engines by 25%. This paper describes the newly designed compressor and turbine to achieve higher output.

BASIC DESIGN CONCEPTS By increasing the air flow rate and pressure ratio and making the exhaust temperature the same as the conventional engine, the high-temperature durability of each component part is maintained, and the output is increased while ensuring reliability. Therefore, a large air capacity, high pressure ratio impeller and matching turbine blades are required.

COMPRESSOR DESIGN The design of low-pressure compressor (LPC) impeller increased the outer diameter of the inlet to increase the air flow rate. The design of high-pressure compressor (HPC) impeller has an outlet outer diameter that is larger than that of the current engine in order to increase the pressure ratio. In terms of structure, strength was evaluated by heat transfer analysis and static analysis using finite element analysis (FEA), and it was confirmed that there were no problems.

TURBINE DESIGN In the turbine design procedure, one-dimensional design is used to adjust the flow path and load, and two-dimensional design is used to adjust the throat in the spanwise direction and blade angle. Then adjust the airfoil in 3D design and check the aerodynamic performance with quasi three-dimension fluid analysis (Q3D) and computational fluid dynamics (CFD). Finally, we manufactured the turbine blades and mounted them on an actual engine to check the effect on the engine performance.

CONCLUSION In this paper, we have explained the compressor and turbine developed by our company, IHI Power Systems, which realizes even higher output of the emergency gas turbine generator. It was confirmed that the output of a 2MW class gas turbine engine could be increased by 25% through actual engine tests incorporating these parts. With this development, it is possible to meet the recent growing needs for space-saving and high power.

Keywords: Advanced Materials and Coatings, Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuels), Others (Industrial Gas Turbine and Power Systems)
Abstract: HAYNES® 282® alloy is a precipitation strengthened Ni-Cr-Mo-Co-Ti-Al alloy combining creep strength, fabricability and thermal stability. Recently ultra-thick 282 plate ~ 68 mm was produced with excellent properties in the principal directions, including short transverse through thickness, which could be an alternative to expensive processing technologies, such as close die forging. In addition, development efforts were also focused on producing fine grained (ASTM 4 or finer) large diameter bar (>125mm) that could offer significant benefits for gas turbine engine components. This paper will also report results from additive manufacturing showing the versatility of 282 alloy, which has been specified for different applications by multiple industrial gas turbine OEMs. HAYNES® 233™ alloy, based on Ni-Cr-Mo-Co-Al, is an alumina-former that offers exceptional oxidation resistance up to 1150C, while 282 alloy can be used up to 871C, so that combining both alloys could be of interest for combustor applications.

Keywords: Others (Materials and Manufacturing Technologies), Materials Degradation and Damage Mechanisms, Advanced Materials and Coatings
Abstract: Ni-base single crystal superalloy TMS-238 was used to investigate the effect of solution heat treatment on the oxidation resistance of the alloy. As-cast sample and sample heat-treated at 1335 °C for 20 h were prepared. Oxidation tests were conducted at 1100 °C, and samples were observed using FE-SEM and EPMA. The as-cast samples had lower oxidation resistance compared to the heat-treated samples. There were also clear differences in the structure of the oxide layers that had formed in the two samples. The heat-treated sample had continuous Al2O3 layer for both dendrite core and inter-dendrite regions. However, for the as-cast sample, the dendrite core region for the as-cast sample did not have continuous formation of the Al2O3 layer, and most of the oxide layer formed was spinel-like Cr2O3. Heat-treatment is necessary to evenly distribute the Al content, so it overcomes the threshold for Al necessary to form protective Al2O3 scale.

Keywords: Component Damage, Failure, and Life Assessment, General Heat Transfer, Film Cooling, Internal Cooling, Others (Materials and Manufacturing Technologies)
Abstract: Thermal deformation analysis plays a crucial role in the design of high-temperature components for gas turbine due to its impact on structural failure. Traditional methods of calculating thermal deformation through finite element analysis often require long computational times. However, the emergence of deep learning method presents an opportunity to achieve fast prediction of thermal deformation. We proposed a deep learning model based on convolutional neural networks (CNN) and residual connection methods to predicting the three-dimensional (3D) thermal deformation field of the double-wall cooling structure unit. By utilizing a dataset of 300 samples generated through computational fluid dynamics (CFD) and finite element analysis (FEA) numerical simulations, the model achieves a prediction accuracy of 97.5%. The deep learning method offers faster predictions than numerical simulations. By incorporating additional physical constraints, it is possible to further improve the accuracy of the deep learning model.

Keywords: Computational Fluid Dynamics
Abstract: CFD predictions are becoming increasingly important in the design of turbomachinery components because correlation-based methods are unable to further improve efficiency and laboratory experiments with the required fidelity are prohibitively expensive. First-principles based simulations are most accurate and have the potential to elucidate mechanisms that can be exploited for further efficiency gains. Their excessive computational cost, however, preclude their use in a design context and therefore modelling is required. Unfortunately, the inaccuracies introduced by RANS- or URANS-based CFD modelling approaches can limit the impact CFD can have on technology development. This presentation will present state-of-the-art high-fidelity simulations of blades and stages, including cases with fully resolved realistic roughness, and show how physical insight relevant to designers has been extracted. The talk will also introduce some of the inherent turbulence modelling errors and how those can be addressed with a novel machine-learning approach that can use both high-fidelity or sparse experimental data. It will be shown that closure models developed using the gene-expression programming approach, which are interpretable and easily implementable into CFD solvers, outperform traditional models both for the cases they were trained on and for cases not seen before.

Keywords: Others (Materials and Manufacturing Technologies)
Abstract: In order to improve the efficiency of gas turbine engines, increase of turbine inlet temperature is most effective. Ni-base superalloys are applied to the high-pressure turbine blades and discs because of their excellent characteristics in high temperature mechanical properties and environmental properties, and increase of the temperature capability of superalloys is still necessary. National Institute for Materials Science (NIMS) has been developing world-leading Ni-base superalloys for the turbine blades and discs. In this presentation, the development of advanced single-crystal superalloys with the world's highest temperature capability and low-cost corrosion-resistant superalloys using “Alloy Design Program” are reported. Several trials for practical application of these alloys, such as research on "direct complete recycling" technology are also introduced.

Keywords: Combustion Simulation, Others (Aircraft Engines), Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuels)
Abstract: The demand for CO2-free transportation of persons and goods by air has become more urgent in recent years in order to meet the challenges of the global climate change. Future aircrafts are required to apply fuels which don’t leave a significant CO2 footprint behind. In order to reach a zero CO2-emission, Hydrogen based on regenerative energy sources (“Green Hydrogen”) is considered as an alternative fuel for the aero engines. One major challenge on the path of development for Hydrogen-fueled aero engines is the safe combustion of Hydrogen and with low NOx emissions at the same time. The MicroMix technology application to industrial gas turbine was researched and developed by Kawasaki Heavy Industries (KHI) and B&B-AGEMA. Therefore, this technology has a great potential for application in aero engines. Initial research and development of a MicroMix configuration applicable for aero engines have been started in a collaboration of both companies. In order to develop and investigate basic geometric configurations high level numerical combustion simulations including Large Eddy Simulation (LES) and complex chemistry combustion have been performed. The LES results in this paper show for an exemplary MicroMix configuration the impact of various numerical and geometrical parameters on the resolution of the numerical results, in particular on vortex interactions of neighboring configurations.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Emissions (NOx, SOx, Soot), Combustion Simulation
Abstract: This work mainly investigates the differential diffusion effect for the H2/NH3-fueled flame. A two-dimensional (2D) direct numerical simulation (DNS) has been implemented for a non-premixed turbulent flame by considering the detailed diffusion of every species in the chemistry mechanism. Based on the equations of mixture fraction and species mass fractions solved in the DNS, the chemistry states of the flame are also mapped through an a priori test. In the test, a flamelet library is established based unity Lewis number for every species. Considerable differences can be observed in terms of the chemistry states, which indicates that equal diffusivity is unacceptable for such H2/NH3-fueled flame, and for the flamelet model differential diffusion should be considered.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Emissions (NOx, SOx, Soot), Combustion Simulation
Abstract: Hydrogen combustion is one of the promising method to achieve net zero carbon emissions. One of the issues in hydrogen engines is NOx (nitrogen oxides) generation. The thermal NOx formation is strongly correlated to the temperature field and a thorough understanding of coupled temperature and NOx formation should be sought. In this study, a fundamental numerical analysis is conducted to understand the hydrogen combustion field. Computational fluid dynamics (CFD) is used to solve the governing equations with chemical reactions where the thickened flame approach is used to relax the grid resolution requirement in the large eddy simulation (LES) framework. The flame shape held by a swirler is well captured and the NO formation is clearly correlated to the local temperature and the residence time. The present method is effective in evaluating NOx formation and it will be extended to a more realistic complicated combustor configuration.

Keywords: Combustion Instability, Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustion Simulation
Abstract: The micromix (MMX) combustion principle is a dry combustion concept for high hydrogen fuels. Multiple miniaturized flames are based on jet-in-crossflow and are thus inherently safe towards flashback. NOx emissions are suppressed by short residence time due to short flame length. Recently, this combustion concept has been successfully demonstrated at a combined heat and power (CHP) generation plant in Kobe, Japan, using a Kawasaki M1A-17 gas turbine of 2 MW class. The objective of this article is the investigation of dynamic effects of the micromix flame at operating conditions beyond the rated power. Therefore, experimental investigations with high speed OH chemiluminescence measurements are carried out at an atmospheric test rig with generic micromix flames. We observe a longitudinal mode at moderate overload and strong transversal modes at high overload operating points. Moreover, the appearance of thermoacoustic oscillations is shifting to lower loads when reducing the fuel injection diameter. This is opposite behavior than the NOx emissions that are suppressed with smaller injection diameter, which results in a trade-off in the design of micromix combustors. Unsteady CFD has been used to simulate the longitudinal mode. The mean field of chemistry heat release rate and Rayleigh index reveals the oscillation amplification region being inside the region of highest chemical conversion. The discovered frequency of around 1000 Hz is slightly higher compared to the measured frequency of 875 Hz, however, the mode is confirmed to be a longitudinal mode like in the experiment.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation, Others (Heat Transfer)
Abstract: This study investigated effects of flow pulsation on the heat transfer performance of the surface with teardrop-shaped dimples. The flow structures and heat transfer characteristics were simulated by large eddy simulation (LES) with a Lagrangian dynamic sub-grid scale (SGS) model. The cases of steady flow and pulsating flow (the Strouhal number of 0.3 and velocity amplitude normalized by bulk velocity of 0.2) were examined for dimple inclination angle of 30deg with in-line arrangement and the Reynolds number of 25,000. Surface-averaged results indicated that the flow pulsation increased the Nusselt number ratio by 8%, the friction factor by 14%, and the heat transfer efficiency index by 8%. Using the phase-averaged results, it was clarified that the increased Nusselt number was due to the appearance and disappearance of flow-separation bubbles induced by the flow pulsation at the leading edge of inclined dimples.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Measurement, Heat Transfer Simulation
Abstract: Latticework cooling has been identified as a promising internal cooling technology for gas turbine blades. This study aims at elucidating the complex 3D flow structure within a dual lattice channel using both experimental and numerical approaches. Utilizing a combination of magnetic resonance velocimetry (MRV) and computational fluid dynamics (CFD), we show that there are three distinct flow regimes: main matrix, trailing edge matrix, and channel between the matrices. The flow structure within the individual matrices are complex, and flow interaction between these regimes also exists. In particular, the flow within the main matrix affects the trailing edge matrix. Understanding the flow structure provides insight into further development of lattice cooling, which can be used to improve the efficiency of gas turbines.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Measurement
Abstract: Film cooling is an essential technology in gas turbines for achieving high turbine inlet temperatures, leading to high thermal efficiency. However, due to the turbulent nature of film cooling near solid walls, it is inherently unsteady, and the complex motion of the coolant makes it challenging to measure the time-varying coverage rate on the surface accurately. To accurately measure such complex behavior of the coolant, high temporal and spatial resolution is required. In this study, a self-made fast-response PSP (Pressure Sensitive Paint) was used to measure the unsteady flow and elucidate the spatiotemporal variation of the coolant attached to the wall. Two types of film cooling holes, circular and shaped holes, were used as experimental conditions, with varying blowing ratios (BR) ranging from 0.25 to 2.0, and main flow turbulence levels of 1% and 5%. The change in film cooling efficiency was assessed using average film cooling efficiency and RMS (Root Mean Square) values to evaluate the changes in cooling effectiveness. The aim of this study is to clarify the spatiotemporal variation of the film coolant using a high-speed, high-sensitivity camera to measure the time-series of instantaneous adiabatic film cooling effectiveness.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Novel Cooling Technology, Heat Transfer Measurement
Abstract: In this study, a shelf-type squealer tip with opened rim was proposed to improve the cooling performance and reduce the aerodynamic loss on the blade tip. A linear cascade with an entrance Reynolds number of 100,000 was built to evaluate the cooling performance of the proposed geometry. The local heat/mass transfer coefficient and film cooling effectiveness on the blade tip floor were measured using the naphthalene sublimation method and pressure-sensitive paint, respectively. The coolant flow rate for film cooling was fixed at 0.6% of the mainstream flow rate, and the tip gap was set at 2% of the blade height. The flow structure and aerodynamic loss were analyzed through RANS simulation. The results showed that the proposed geometry showed a 16.6% reduction in thermal load on the tip floor and a 23.3% decrement in the total pressure loss compared to the existing blade design.

Keywords: Others (Aircraft Engines), Propulsion/Aircraft Integration, Energy and Thermal Management, Acoustic Issues
Abstract: The acoustic liner is one of the most effective devices for suppressing fan noise emitted from aircraft engines. IHI and Japan Aerospace Exploration Agency (JAXA) have developed a resin-based acoustic liner for fan noise attenuation that is lighter than conventional acoustic liners. In this study, the component-technology demonstration for the full-scale resin-based acoustic liner was conducted on the turbofan engine testbed installed at the JAXA test facility to assess compatibility with production engines. Acoustic, engine performance, aerodynamic and structural measurements were performed during the test campaign. According to the test results obtained in the testbed, it was shown that the resin-based acoustic liner has good noise reduction performance as expected for typical acoustic liners. The resin-based acoustic liner showed little impact on the engine performance. Structural soundness for the loads and vibrations in actual operating environment was also demonstrated. The result is promising for the application to future production engines.

Keywords: New Aircraft Propulsion Concepts, Electric/Hybrid Propulsion, Aircraft Electrified Propulsion
Abstract: Distributed propulsion configurations are a promising concept for future aircraft systems. The main objective of the presented experiment is to investigate propeller-wing interactions in detail. An understanding of the interactions is deducted from the experiment. Furthermore, a data basis for numerical studies is created. In the work presented, the interaction between adjacent propellers as well as the two-way interaction of wing and propellers is studied. The designed wind tunnel model features a two element wing c = 0.8m with three co-rotating propulsion units with a diameter of D=0.6m or D=0.4m. They are mounted on a separate carrier, which is installed in the test section of the Propulsion Test Facility, TU Braunschweig. The outboard sections generate periodic boundary conditions, whereas the centre wing and propeller are subject of analysis. Both the centre wing and the centre propeller are instrumented for force and moment measurements. The flap of the wing is freely adjustable. The detached setup of wing and propeller allows a variable adjustment of the relative propeller position to the wing. This feature allows the propeller to be moved horizontally -0.77 < x/c < -0.1, vertically -0.2 < z/c < 0.2 and spanwise 0.025 < y/c < 0.6 in small increments. The effect of the wings upstream flow field on the propeller is compared and analyzed for different positions. In addition to the relative position, three different propeller blades are investigated, which differ in size and design. While two blades were designed for minimum induced losses, a third set of blades was designed for homogeneous induced velocity. A comparison for the isolated propeller and the DP configuration is shown. The thrust level is varied by blade pitching.

Keywords: Propulsion/Aircraft Integration, Energy and Thermal Management, General Heat Transfer, Film Cooling, Internal Cooling, Computational Fluid Dynamics
Abstract: The integrated strut flame stabilizer is in direct contact with high temperature flame. In order to prevent the wall surface from being ablated, a double-wall cooling structure is set on the wall surface. Cold air is introduced from the outer culvert to cool the strut. Under certain boundary conditions, the influences of single geometric parameters on the cooling performance of the double-wall were investigated by numerical simulation, including the diameter of the film hole, the diameter of the impact hole, and the impact distance. The results show that: The aerodynamic thermal environment behind the integrated strut is affected by many factors. The change of geometric parameters will affect the flow of cold air in the double-wall, and then affect the interaction between the film outflow and the mainstream. Therefore, with the increase of the geometric parameter value, the variation of the cooling performance of the double-wall is not linear, but fluctuating.

Keywords: Propulsion/Aircraft Integration, Energy and Thermal Management, Novel Cooling Technology, General Heat Transfer, Film Cooling, Internal Cooling
Abstract: This study introduces a novel printed circuit heat exchanger (PCHE) with airfoil fins for use in aero-engine cooling systems. The airfoil channel is based on the NACA0025 airfoil and has a heat transfer surface density of over 1500m^2/m^3 and a hydraulic diameter of 0.87 mm. An experimental system is developed to evaluate the thermal-hydraulic performance of the PCHE under high-temperature and high-pressure environments, similar to the conditions inside an aero-engine. Hydrocarbon fuel RP-3 and deionized water are used as the heat transfer medium. The results develop correlations for Nusselt number with a deviation less than 2%, and indicate the flow resistance losses on both sides is less than 1%. Provide a reliable guide for the development of compact heat exchangers in aero-engines and for the investigation of the heat transfer characteristics of hydrocarbon fuel like RP-3.

Keywords: Computational Fluid Dynamics, Others (Aerodynamics and Design)
Abstract: In cooperation with the Bundeswehr Technical Centre for Aircraft and Aeronautical Equipment in Manching, the Institute of Jet Propulsion (IJP) designed the highly bent, compact intake system MEIRD (Military Engine Intake Research Duct). The double-S-shaped intake duct prevents radar reflections and causes strong flow distortions due to its curvature. These flow distortions’ size, strength, and pattern can negatively affect the engine’s compressor. Previous investigations were primarily focused on distortion evaluation at the aerodynamic interface plane (AIP), and the characterization of the local assessment of the distortion was missed. In this work, the flow inhomogeneity progression through a highly bent intake is analyzed using CFD. The study is based on a prior investigation to preliminarily characterize the inhomogeneity by a newly defined cross-sectional loading parameter. The analysis of various parameters allows the detailed classification of the flow distortions through the intake. A direct dependence of the local pressure standard deviation between the calculation from the cross-sectional area and the wall pressure profile has been shown. Furthermore, mixing flow by the distance between intake and compressor has a widely differing influence on the observed parameters.

Keywords: Computational Fluid Dynamics, New Aircraft Propulsion Concepts, Propulsion/Aircraft Integration, Energy and Thermal Management
Abstract: Boundary Layer Ingestion (BLI) is one of the promising concepts being developed to reduce carbon dioxide emissions from aircraft. However, ingesting boundary layer causes inlet distortion that changes the fan-inflow and hence may decrease fan adiabatic efficiency. To mitigate this issue, the authors conducted numerical analysis of the TechClean fan and fans with skewed blades under both clean and distorted flow conditions. The analysis of the first configuration of skewed blades indicates that sweep may have a positive effect, while dihedral showed a negative effect due to an excessively large skew angle. Further analysis of fans with various configurations of sweep and dihedral blades has been conducted.

Keywords: Computational Fluid Dynamics, Others (Aerodynamics and Design), Axial Compressors
Abstract: The performance of an aircraft engine declines in the course of operation due to deterioration. Specifically, this leads to an increase in exhaust gas temperature (EGT) and thrust-specific fuel consumption. When a certain EGT limit is exceeded, the engine must be overhauled. During the repair process of fan and compressor blades, certain limits defined in the engine manual must not be exceeded. These limits ensure the continued safe operation of the blades. However, no evaluation criteria have yet been established concerning aerodynamic performance. Neither the range of variations in individual geometric parameters due to wear, such as leading and trailing edge thickness, chord length, and tip clearance, nor their effects on aerodynamic performance are determined. Thus, it is not possible for independent maintenance, repair and overhaul (MRO) organisations to draw any conclusions on the degree of engine performance impairment. To narrow this knowledge gap, this study investigates the aerodynamic performance of operationally used fan airfoils of a turbofan engine. Based on a set of 30 digitized fan blades consisting of new as well as operationally-used blades of a commonly deployed turbofan engine, typical blade profile geometries are identified and analyzed. The analysis results are then used to define the factor space for a subsequent Design of Experiments (DoE) of varying geometric profile parameters. The impact of individual parameters on the aerodynamic performance of selected profile sections is then investigated via computational fluid dynamics (CFD) analyses using the TRACE solver developed by the German Aerospace Center (DLR).

Keywords: Computational Fluid Dynamics, Heat Transfer Simulation
Abstract: Aircraft icing threatens navigation safety as it reduces aerodynamic performance. Although icing prediction is significant in an aircraft design phase, it is a challenging issue due to its multi-physics nature. In addition, in the glaze ice and supercooled large droplet (SLD) conditions, complicated ice shapes make the prediction very difficult. Then, we developed the coupling scheme composed of the grid-based and the particle-based methods to simulate icing on an airfoil. However, the previous study treated only conductive heat transfer from the ice and liquid layers on the airfoil for thermodynamics computation. This study conducted icing simulations on NACA0012 airfoil considering both convective and conductive heat transfers. The convective heat transfer was estimated by the grid-based method, and the thermodynamics of the icing process was simulated by the particle-based method. As a result, ice mass at 60 seconds increased by 7 % compared to the previous method. It was suggested that the convective heat transfer should be essential for the longer-term icing simulations.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control, Others (Aerodynamics and Design)
Abstract: In this study, transient behavior of axial compressor for industrial gas turbine shut down operation was investigated. Dynamic simulation model was improved to estimate compressor transient behavior. Gas turbine compressor has bleed system to obtain turbine cooling air, the bleed air is cooled at heat exchanger which has large volume. At shut down condition, pressure at compressor main flow decrease soon, however the pressure at the heat exchanger remains high. Thus, reverse flow occurs at high pressure bleed system from heat exchanger to compressor main flow. Reverse flow occurs temporary, high pressure air is injected in front of rear block of compressor from bleed chamber, pressure ratio of rear block is not increase with comparing to steady state. On the other hand, at middle block, pressure ratio increase and surge margin decrease. Volume of heat exchanger affect to compressor stage loading distribution, loading of middle and rear block increase on whole, not only rear block. The dynamic simulation is necessary to estimate surge limitation under transient condition.

Keywords: Axial Compressors, Computational Fluid Dynamics, Gas Turbines for Electric Power Generation
Abstract: This paper presents some numerical results demonstrating the effects of earlier blow-off valves closing and higher ambient temperature on the aerodynamic characteristics within an industrial heavy-duty gas turbine compressor. The prototype start-up process and two other schemes are simulated with steady 3D/1D numerical methods. The ambient temperature of scheme-1 is the same as that of prototype, but the blow-off valves closing GT speeds of scheme-1 are lower. The blow-off valves closing GT speeds of scheme-2 are the same as that of scheme-1, but the ambient temperature of scheme-2 is higher. The numerical results of prototype and two schemes are evaluated by analysing their aerodynamic stability. Special attention was paid to the effects of modulating the variable guide vanes on start-up characteristics, which play a key role in the stable operation of gas turbines. It is shown, that earlier blow-off valves closing and higher ambient temperature lead to the deterioration of compressor aerodynamic stability. And increasing the opening of variable guide vanes appropriately can improve this problem.

Keywords: Others (Aerodynamics and Design), Axial Compressors, Process Simulation
Abstract: Gas face seal, an advanced sealing technology, has found extensive applications in ground-rotating machinery. However, its utilization in aviation engines has been limited thus far. The gas face seal with three film thicknesses and five groove depths at high rotational speed and low inlet pressure of an aero-engine was simulated. The results revealed that the peak pressure occurs at the groove’s root, whereas the relative negative pressure zone (RNPZ) manifests itself at the groove’s inlet. The behavior of the RNPZ is influenced by both the radial and circumferential velocities. When the groove depth remains unchanged and the film thickness decreases, the RNPZ converges towards the inlet. When the film thickness remains constant, the RNPZ strength converges to the inlet weakens. The convergence of RNPZ towards the inlet has a certain inhibitory effect on the leakage rate. The RNPZ converges to the inlet to enhance the opening force and stiffness-leakage rate.

Keywords: Axial Compressors, Computational Fluid Dynamics, Others (Aerodynamics and Design)
Abstract: Seasonal variations of the ambient conditions affect the performance of turbomachines. Compressors are particularly sensitive towards these variations, which must be considered in order to obtain representative performance predictions. This paper investigates how variations in the inlet total temperature due to seasonal changes propagate and how this affects compressor performance predictions. The results show that the corrected mass flow rate, the total pressure ratio and the isentropic efficiency decreases with an increasing inlet total temperature. The total temperature ratio, in contrast, increases with an increasing inlet total temperature, with exception of the region near the choke limit. The propagation depends on the compressor operating point: the sensitivities of the corrected mass flow rate, total temperature ratio and isentropic efficiency with respect to the inlet total enthalpy increase with an increasing total-to-static pressure ratio. The sensitivity of the total pressure decreases with an increasing total-to-static pressure ratio.

Keywords: Others (Aerodynamics and Design), Centrifugal and Mixed-Flow Compressors, Computational Fluid Dynamics
Abstract: The primary focus of this study is to optimize the shape of the exhaust volutes of a particular type of mixed working fluid centrifugal compressor. The objective is to improve the aerodynamic performance of the volutes and enhance the overall performance of the compressor. To achieve this, both the adjoint method and parametric optimization approach are employed, and their results are compared to determine the optimal approach. The results indicate that after 65 iterations of parametric optimization, the total pressure recovery coefficient of the exhaust volute increased by 0.577%. Using 37 steps of adjoint optimization, the optimized total pressure recovery coefficient increased by 1.614%. Comparison between parametric optimization and adjoint optimization reveals that the latter resulted in more noticeable changes in the shape of the discharge volute, ultimately leading to significant improvements in its aerodynamic performance. Faster convergence is achieved by the adjoint optimization approach.

Keywords: Turbines, Others (Aerodynamics and Design)
Abstract: Robust aerodynamic optimization (RADO) considering the flow uncertainty is very important for turbomachinery design. In this study, a robust optimization framework coupled with discrete adjoint and polynomial chaos expansion (PCE) is developed to improve the robustness of turbomachinery. To avoid the “dimensional curse” caused by an increase in design variables, the optimization framework is based on gradient algorithms. Only once PCE model needs to be constructed in per optimization step, and the gradient of RADO objection is obtained by using chain rule. To verify the effectiveness of the RADO framework, a robust optimization of the transonic turbine cascade HS1A is implemented in this study. Monte Carlo simulation and finite difference PCE are used to verify the uncertainty quantification and gradient propagation methods respectively in this study. Comparison with deterministic aerodynamic optimization (DADO), the RADO method further reduces the standard deviation of the distribution of the DADO objective function.

Keywords: Unsteady Flow and Stability Enhancement in Compressor Flow Control, Computational Fluid Dynamics, Axial Compressors
Abstract: The design of high-loading and compact modern turbomachines results in strong interactions between two adjacent blade rows, which is found to have an impact on the aerodynamic performances of multi-row turbomachines. Therefore, it is necessary to consider unsteady effects coming from blade row interactions in multi-row turbomachinery aerodynamic analyses and design optimizations. In this work, three-dimensional multi-row unsteady design optimizations are performed using a full viscosity discrete adjoint solver developed by using the source code transformation automatic differentiation tool--Tapenade. An efficient time domain harmonic balance method analyzes the unsteady flow and adjoint fields. To reduce the computational cost required, a single-passage computational domain with the phase shift boundary condition used to deal with the geometric periodic boundaries is adopted in analyzing both unsteady flow and adjoint fields. Information exchange across an interface is realized by a rotor-stator coupling interface method, which uses coordinate and Fourier transforms to extract time and space modes. Then these extracted modes are matched at two sides of an interface together with one-dimensional non-reflective treatment. To stabilize the solution, the one-step Jacobi iteration combined with the Lower-Upper Symmetric Gauss-Seidel (LU-SGS) method is used for the implicit treatment of the unsteady flow and adjoint governing equations in harmonic balance form. The results from a single-stage transonic compressor demonstrate that, compared with the steady mixing plane approach, the multi-row unsteady approach can capture more real flow physics such as wake passing, and achieve more aerodynamic performance gains after optimization.

Keywords: Advanced Materials and Coatings, Manufacturing, Repair, and Refurbishment Technologies, Materials Degradation and Damage Mechanisms
Abstract: Thermal insulating property of TBC strongly depend on its topcoat thickness. However, the thicker the topcoat thickness, getting the less durability of thermal cycle property. Therefore, improving thermal cycle property of conventional porous TBC is important to obtain TBC which has good thermal insulating properties. In this paper, we present the porous and thick TBC with improved thermal cycle durability by modifying microstructure of the topcoat. While the developed TBC has almost as same topcoat porosities as conventional one in macrographic images, lamellar pores formed between splat is much less than the conventional. It was shown that thermal cycle property of the developed coating whose thickness of topcoat is 1.5mm was significantly improved in furnace thermal cycle test. It is considered that fractions of lamella pores in the top coating, which would be crack path under thermal cycle conditions, has influenced to thermal cycle durability.

Keywords: Others (Materials and Manufacturing Technologies)
Abstract: ABSTRACT

High-temperature thermo structural composites (C/C, C/SiC,

SiC/SiC), are manufactured by densely filling the voids within a preform with C and SiC. These composites are applied in space and aeronautics applications as well as propulsion systems [1-5]. DACC Carbon has researched and developed high-temperature composites since 1990. And also we improved the thermo-mechanical properties of these composites by modifying their manufacturing process. We have tested these composites' thermo-mechanical properties, and the results will be described.

INTRODUCTION

High-temperature thermo structural composites (C/C, C/SiC,

SiC/SiC) have many potential applications in space and aeronautics as well as propulsion systems, owing to their high specific strength/modulus at elevated temperatures, and thermal shock resistance. These composites also allow a reduction of mass in comparison with existing metallic systems [1-5]. DACC Carbon uses different reinforcements (carbon fibers, silicon carbide fibers) and several densification processes for either carbon or silicon carbide matrix to manufacture these composites. Recently silicon carbide fiber reinforced silicon carbide matrix composites (SiC/SiC) are becoming a major alternative for the next gas turbine engines’ parts. Considering this new target, R&D programs for development of gas turbine engine hot structural parts sponsored by government have been progressing from 2020 until 2024.

Keywords: Manufacturing, Repair, and Refurbishment Technologies, New Testing Technology, Others (Combustion, Fuel and Emissions)
Abstract: The industry and the academy are continuously developing new technologies and approaches regarding the gas turbine manufacturing. Logically, sectors of turbomachinery and aerospace engineering are deeply focused on applying newer and even unconventional manufacturing process, aiming on cost reduction, reduced lead times and efficiency. In addition, it is conspicuous that metal additive manufacturing (AM) technologies can provide interesting possibilities for companies seeking to innovate and perfect existing components, with respect to reach better buy-to-fly ratios. In this paper, the authors developed a proposal for additively manufacturing a fuel swirler and evaluated in detail its process of fabrication in order to compare the results with the characteristic of a conventionally manufactured swirler. Furthermore, a dedicated review of the state-of-the-art related to the AM of fuel swirlers were realized to evaluate the relevance of this topic to conclude if the use of AM to fabricate this component can favor the aerospace industry.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustor Development, Emissions (NOx, SOx, Soot)
Abstract: Combustion technology has been developed for the use of ammonia as fuel in gas turbines. For the method of supplying ammonia to the combustor, a liquid ammonia direct spray method is adopted, in which ammonia can be supplied by a simple system. In previous developments, unburned NH3 and N2O were emitted under conditions with high ammonia mixing ratio, resulting in diminished GHG reduction. To resolve these issues and achieve stable operation of the gas turbine under liquid ammonia single-fueled combustion conditions, the two-stage combustor designed in the previous study is improved. 2MW-class Gas turbine tests results with the improved combustor show that the gas turbine can be operated stably by liquid ammonia firing, while at the same time N2O emissions are suppressed and GHG reductions of more than 99% are achieved.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Emissions (NOx, SOx, Soot), Gas Turbines for Electric Power Generation
Abstract: Renewable power generation capacities mostly underlay inherent fluctuations. To maintain the security of supply in a regenerative-dominated energy system, flexible components must be increasingly implemented for balancing the residual load. Among other things, gas turbines are also eligible for this grid-serving task. However, fuel utilization in gas-based power generation technologies is inherently linked to emissions.

This study investigates the impact of hydrogen employment in single-cycle gas turbine power plants on the emission behavior and the corresponding emission footprint. The emission formation in different operational regimes is quantified by linking part-load emission characteristics for different hydrogen admixing rates and time-resolved load profiles with emphasis on startups, part-load operation, and transient load changes.

The results show that the emission species associated with incomplete combustion, i.e., CO, CH_2O and CH_4, significantly increase when operating the gas turbine in lower part-load, while CO_2, NO_x and particulate matter (PM) emission can not be assigned to a specific load condition. Hydrogen admixing leads to a greater reduction of carbon-containing pollutants than the simple reduction of carbon-intense energy input (and therefore CO_2) due to enhanced chemical conversion rates. In contrast, NO_x emissions increase with hydrogen admixing dominantly via the thermal pathway. The environmental impact analysis shows that the impact of greenhouse gases is dominated by the CO_2 emissions and therefore decreases with hydrogen admixing, while the damage categories for human toxicity and photochemical ozone formation are dominated by the NO_x emissions and therefore increase with hydrogen admixing. The damage associated with respiratory inorganics remains approximately constant because the effect of PM reduction and NO_x increase cancel each other out.

Keywords: Others (Heat Transfer), General Heat Transfer, Film Cooling, Internal Cooling
Abstract: Labyrinth seals are widely used at the dynamic and static interface in turbine machinery to limit fluid leakage, such as in cooling air system in gas turbines. Due to the viscosity of gas, the viscous work generated by the rotating components of the seal not only represents a direct loss of power, but also causes an increase in the total temperature of the fluid (windage effect). The leakage flow and windage temperature increment characteristics of the labyrinth seal at low Reynolds number are studied in this paper. The leakage flow field of the labyrinth seal is analyzed, and the effects of Reynolds number, rotational speed and seal gap on the windage temperature increment characteristics of the labyrinth seal are studied. The research results show that: at low Reynolds number, the windage temperature increment of the labyrinth seal increases linearly with the increase of the rotational speed; the windage temperature increment coefficient decreases with the increase of the inlet Reynolds number, and the decreasing trend gradually weakens; Sealed windage temperature increment characteristics are less affected.

Keywords: Heat Transfer Simulation, Thermal Management of Structures, General Heat Transfer, Film Cooling, Internal Cooling
Abstract: Clearance prediction in rotating machinery is a complicated and interdisciplinary process that includes transient thermal-mechanical modeling of all components influencing clearance in one assembly model across a wide range of operational scenarios. This analysis process is typically referred to as a Whole Engine Model (WEM) within the aero and power generation gas turbine business. Understanding the transient evolution of the clearances enables manufacturers to optimize the performance and efficiency of an engine while reducing the risk of rubbing or other damage. The WEM can be utilized to understand not just the steady-state condition of a gas turbine engine when it is thermally soaked, but also the transient operations where thermal gradients and deltas and rotational loads have all a significant impact on the gap between the rotating and stationary parts. Some of the primary advantages of using a WEM for clearance predictions are as follows: a) reducing complexity and run time while maintaining accuracy b) accounting for asymmetric effects (casing distortion, airfoil twist, mass accumulation) c) updating the model based on new geometries and operating conditions d) referencing boundary conditions from upstream simulation models (i.e. secondary air systems, boundary condition interdependency/links) e) application of proprietary correlations for windage and heat transfer coefficients (HTC) f) ability to split the model and therefore the workload into sub-models and later merge into one large assembly Simcenter 3D, the tool used in this analysis, is a multiphysics platform which contains gas turbine specific tools and boundary conditions that enable analysts and engineers to capture relevant physics to ensure their clearance predictions are accurate across all operational scenarios. In addition, the CAD-centric approach to simulation allows users to quickly update their models when changes are required. This master model approach enables a true digital twin of the gas turbine engine. The CAD-centric approach is used to show how modifying the thickness of stationary components can be used to obtain tighter tip clearances in the turbine. In addition, the modification of engine operating parameters during shutdown is also shown to significantly improve baseload/steady state clearances.

Keywords: Heat Transfer Simulation, General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Measurement
Abstract: Maintaining and validating a digital twin for industrial applications is key to derive reliable lifetime and performance predictions. Usually, engineers and analysts use test data and validated models from prior programs to calibrate and enhance their digital twins. However, the calibration and validation procedures are generally manual and can take several months due to the number of parameters to adjust, the number of sensors used, and the multiple operating conditions to consider. To limit the optimization complexity, the actual workflow usually involves sub-modeling techniques. This is problematic as inter dependencies are ignored and often lead to divergence after reintegrating the sub models into the final digital twin. Optimization frameworks offer the possibility to automate and perform this validation procedure for the whole digital twin, but the computational cost associated is still extremely high and prevents the engineers to consider all the parameters and mission profiles. Maya HTT recently developed TMG Correlation, an adjoint-based solver that allows optimizing a digital twin using reference test or analysis data in a faster and more efficient way than classic optimization methods. This solver is implemented in Siemens Simcenter 3D and supports both steady-state and transient thermal correlation analyses with little overhead related to the number of design variables and sensors. This presentation focuses on the validation of a simplified and representative gas turbine whole engine model containing hundreds of boundary conditions and corresponding number of design variables, using virtual test data and TMG Correlation. The presentation will first focus on a description of the TMG Correlation tool and its associated adjoint-solver. Then, the whole engine model use case and the thermal correlation setup will be described. The performance of the tool and the results will be discussed on a simple case, followed by a real and more complex industrial use case currently being developed with Ansaldo Energia.

Keywords: Axial Compressors
Abstract: In order to improve the efficiency of modern turbomachinery, the simulation setups in design processes become increasingly detailed, and thus computationally more expensive. This paper aims to quantify the numerical influence of squealer tips on the performance of a 4½-stage axial compressor. For this purpose, the performance map, obtained by steady-state calculations using the k-ω SST turbulence model and the TRACE flow solver, is simulated for two setups: the reference setup and a setup with squealer tips added. The inclusion of squealer tips enhances the stage-wise compressor performance by reducing secondary flow and flow separation at the casing. This improvement results from the change in blade-tip geometry. The stage total-pressure ratio is thus improved by up to 0.28%. However, a deterioration of the fourth-stage flow as a result of the squealer tips prevents these improvements from enhancing the overall compressor performance.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control
Abstract: Circumferential inlet distortion often occurs on the condition when aircrafts takeoff with high angle of attack or crosswind, which is generally detrimental to aeroengine. The purpose of this paper is to develop the stabilization method based on foam metal casing treatment (FMCT) under circumferential inlet distortion. Steady and transient data are measured in an axial fan. The experimental result shows that the stall margin is greatly recovered by FMCT, and the efficiency loss is less than 1% under a certain degree of distortion. The mechanism of FMCT is discussed based on the analysis of pre-stall behavior and perturbation energy. Comparison of rotor tip flow field on distortion regions and non-distortion regions is evaluated and the physical mechanism of stabilization is validated further.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control
Abstract: An experimental investigation has been carried out on the effect of foam metal casing treatment on the stall margin of an axial flow fan. Tests were conducted with two rotors with different loading mode: one is a fore-loaded rotor and one is an aft-loaded rotor. It was found that the casing treatment can improve the stall margin of the fan with both rotors. There is a relation between the stall margin improvement (SMI) and the axial location of the casing treatment. The maximum SMI is achieved at location 7 for the two rotors. Detailed measurements were also taken in the present experiment. There showed that the blade tip loading is reduced in the area affected by the casing treatment.

Keywords: Axial Compressors, Computational Fluid Dynamics, Unsteady Flow and Stability Enhancement in Compressor Flow Control
Abstract: Counter-rotating axial compressor (CRAC) has great potential in improving the thrust-to-weight ratio of aero-engines. The revelation of the internal physical flow mechanism of counter-rotating compressors can guide the flow control design. A data-driven dynamic mode decomposition (DMD) method is introduced to investigate the physical flow mechanism and the stall inception mechanism under the near-stall condition in a two-stage counter-rotating compressor. The results show that the multi-order low-frequency unsteady oscillation rather than the blade passing frequency (BPF) presented by the tip leakage flow becomes the dominant frequency inducing the flow unsteadiness. The main frequency of the front rotor (R1) is 1.0 times the blade passing frequency (1.0BPF), while the dominant frequency in the rear rotor (R2) is the unsteady frequency of the tip leakage flow, which is 0.81BPF.

Keywords: Centrifugal and Mixed-Flow Compressors, Others (Aerodynamics and Design), Computational Fluid Dynamics
Abstract: Centrifugal compressors are subject to uncertainties during their manufacture and operation, leading to reduced efficiency and performance dispersion. However, uncertainty quantification and robust design of compressors remain challenging due to the complex structure and internal flow. This study proposes an automated framework for uncertainty quantification and aerodynamic robustness optimization of centrifugal compressors. The manufacturing error distribution is obtained from measured data of machined compressor blades, and a total of ten geometrical uncertainties are propagated for the nominal design point. The main objective of the robust optimization is to minimize the standard deviations of the compressor aerodynamic performances at three operating points and to preserve the mean values of these performances. The sparse grid-based probabilistic collocation method is used to propagate these uncertainties, and a multi-objective genetic algorithm is adopted to perform this robust optimization based on a coupled surrogate model. The results show that the optimized compressor exhibits an increase in mean isentropic efficiency and pressure ratio, respectively, compared to the prototype compressor. Furthermore, the standard deviation of isentropic efficiency, pressure ratio, and mass flow rate significantly decrease. This study provides valuable insights into uncertainty quantification and robust optimization of advanced micro turbomachinery.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuels), Aircraft Electrified Propulsion, Emissions (NOx, SOx, Soot)
Abstract: Hydrogen-based propulsion for aviation has been a subject of research since the 1950s with the main focus of interest being high-altitude aircraft with hydrogen-combustion turbojet engines. With the recent growth in economical and ecological interest in the application of hydrogen in the transportation sector, both as energy storage and jet fuel, its application is extending towards fuel cells and in particular proton exchange membrane fuel cells (PEMFC). As stated by Leipold (2021), the increase in take-off weight for purely battery-powered aircraft does not result in feasible designs. Hence, regional aircraft for up to 70 PAX could be driven by fuel cell/battery hybrid propulsion systems while longer range would have to rely on new engine options and other technology improvements. The short range sector is of special interest since about one third of the overall passenger CO2 emissions originate from flights shorter than 1500 km and 43% from flights under 2000 km. The majority of these flights can be covered by regional aircraft such as the current ATR 72-600 with 70 seats, which is therefore the market area of the present study. The project DEFCA (Design-space-evaluation of the air, heat and power management of fuel cells for aviation) within the cluster of excellence SE2A aims at investigating the cathode gas supply system of future fuel cell systems, adressing both the integral performance analysis as well as the design of required turbomachinery components. The focus of this paper lies on the elaboration of feasible hydrogen-based propulsion systems and their operating range for the regional aircraft sector. In particular, fuel cell-based propulsion systems and their cathode air supply system, which is a main parasitic power consumer, will be investigated. Initially, the outline of the project and the methods and tools to be used will be presented. Next, the design space for an electrically driven cathode gas supply system is investigated to highlight the constraints that apply to the technology in an aircraft scenario. Second, the impact and constraints of the operating range are investigated. Third, the impact of a turbine on the operating parameters is shown. Finally, the impact of the chosen design point on the overall performance will be investigated.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuels)
Abstract: The de-carbonization process is impacting many industrial sectors in which new energy sources and vectors have been identified and are nowadays being implemented. Hydrogen is well established as a carbon-neutral energy carrier that, thanks to its mass energy content, can be applied in many energy-consuming processes. In the next years it is expected that hydrogen will play a major role in the de-carbonization process of applications and industries located in remote areas where renewable sources or stable and developed electrical networks are not available or difficult to realize and maintain. Although the mass energy density is favorable for hydrogen, the hydrogen transport poses some challenges due to its low mass density, usually requiring high pressure transport or liquid transport that are associated with high costs and technical complexity. Ammonia (NH3) is a carbon-free molecule with high hydrogen content that can be used as carbon-free hydrogen carrier, in fact it can be produced without C02 emissions through the use of electrolyzers, air separation processes supplied with renewable power. Moreover a molecule of ammonia is characterized by a volumetric energy density 70% higher than liquid hydrogen whose transport and storage is characterized by a simple and consolidate processes. The main challenge in the utilization of ammonia as fuel is the extraction of hydrogen from the ammonia molecule. The main two processes are the ammonia burning or the ammonia cracking. While the low-emission direct burning of ammonia is currently being studied and developed and in the long term may be the most indicated approach for the power generation, the ammonia cracking is a technology currently available. In this work an efficient ammonia cracking process is discussed. In the process a 100% hydrogen ready gas turbine engine has been used as heat source for the dehydrogenation process. Cracking process has been enhanced by burning and/or recycling the unreacted ammonia minimizing relevant heat/energy consumption, with the target of obtaining green energy without additional losses. The paper shows and discuss in detail how the global energy balance of this solution is preferrable when compared with a stand-alone cracking system where additional (external) heat source is used. The process will be also compared with the direct ammonia burning.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuels)
Abstract: The global de-carbonization effort requires the scouting and development of new technologies as long as dedicated infrastructures that allow the reduction or the elimination of carbon dioxide emissions in such processes. In the area of energy transport and distribution, hydrogen has widely been recognized as a carbon-free energy carrier, whose development in terms of technology and infrastructure will provide significant benefits in the de-carbonization process. Although widely accepted, the use of hydrogen in the power generation is still under development due to the need for dedicated technology able to dispatch and utilize and integrate hydrogen in the current processes and energy supply chains. In particular, current gas turbine technologies that could already utilize hydrogen blends, will require dedicated technology developments to be suitable to be fed with 100% hydrogen. In particular, the use of H2 with current combustion chambers technology requires dedicated auxiliary systems suitable for H2 application, together with combustion systems able to utilize H2 with an optimal control of NOx emissions. The Baker Hughes NovaLTTM has been developed in order to be able to operate with fuel contents of H2 up to 100% in the whole operating range, including start-up and shut-down. In this work the development, testing and validation of this gas turbine technology is discussed in detail focusing on the combustion design and performance, on the testing and validation campaign and on the specifications of a whole package suitable for H2. The combustion system has been developed to improve the component performance and reliability and has been based on new burner technology design criteria that have been validated through numerical analyses and tests. Validation of the advanced H2 combustion system has been performed through extensive testing campaign: first the combustor components have been tested, then a full-scale combustion system test has been performed, concluding with a full-size gas turbine engine test. Through the gas engine test, a wide range of operating conditions at various loads have been verified and assessed. The design development and testing has been applied also to the gas turbine package, ensuring auxiliaries compatibility and performance with 100% H2 and focusing on the safe and reliable engine operation by selecting proper safety features (i.e. gas detection and firefighting systems). The NovaLTTM testing with 100% H2 fuel required al