bluuebunny/crossref_metadata_2025 huggingface dataset:
Challenges in the Production of Fuel Cells for Aviation
Authors: Sperling Patrick , Horstkotte Rainer , Sommer Jan , Gierlings Sascha , Janssen Henning , Herrig Tim , Bergs Thomas , Brecher Christian
Published: August 2024

The influence of increasing resource scarcity and climate change has a significant impact on aviation. Therefore, the European Commission has set ambitious goals with a 75 % reduction in CO2 and a 90 % reduction in NOX as part of the Flightpath 2050 vision. Achieving these goals requires the use of disruptive technologies in aviation, especially in propulsion. In addition to the use of Sustainable Aviation Fuel (SAF), the use of hydrogen is a promising alternative. There is the possibility of using a fuel cell which acts as an energy converter and powers the primary electric drives, offering the potential to fly emission-free, especially for short- and medium-range flights.

However, successful integration of the fuel cell into the aircraft’s powertrain requires a significantly increased gravimetric power density compared to the status quo. Furthermore, the fuel cell and the entire manufacturing process chain must fulfill the stringent safety requirements of aviation. Therefore, the bipolar plate and, respectively, its production process are key elements for the fuel cell.

This paper describes how to establish a basis for the production of the bipolar plate in accordance with aviation requirements. For this purpose, the process chain is explained step by step and for each process step different technology alternatives and corresponding challenges are identified. Finally, an aggregated view of the holistic process chain is given.
Foreign Object Damage of Environmental Barrier Coatings Subjected to CMAS Attack
Authors: Hoffman Leland , Stokes Jamesa L. , Setlock John
Published: August 2024

Foreign object damage (FOD) and attack by calcium magnesium aluminosilicates (CMAS) have been identified as two key damage and failure mechanisms in environmental barrier coatings (EBCs), which are being developed as an enabling technology for silicon carbide (SiC) based composites in gas turbine engines. CMAS exposure at elevated temperatures has been shown to cause premature failure in ytterbium disilicate (Yb2Si2O7) based EBCs. Previously, the effects of foreign object damage were studied on NASA’s Yb2Si2O7-based EBC deposited on SiC. This study aims to understand the synergistic effects of CMAS attack and FOD on the same EBC system. CMAS was loaded onto the EBC at either 2 mg/cm2 or 4 mg/cm2 prior to being fully reacted for 4 hours in a 1316°C furnace. Samples were then impacted at room temperature using a 1.59 mm hardened steel ball with projectile velocities of 50–100 m/s. The impact damage was characterized by depth of the impact crater and length of the EBC delamination as determined by optical profilometry and scanning electron microscopy (SEM) of the cross-sectioned samples. The results of the samples subjected to CMAS attack were then compared to that of the previous study on NASA’s baseline Yb2Si2O7-based EBC. A mechanical assessment of the coatings was also made. Vickers indentation was used to determine coating hardness as well as estimate indentation fracture toughness and nanoindentation was used to estimate the Young’s Modulus.
Effect of Ceramic Matrix Composites on the Thermal Efficiency of a Power Generation Turbine
Authors: Tayade Ashrit , Lynch Stephen
Published: August 2024

Ceramic Matrix Composites (CMCs) offer higher allowable temperatures and reduced weight, making them an attractive prospect for parts in the hot section of a gas turbine engine. As CMCs are increasingly adapted into aero and land-based engines, there is a need to quantify the performance increase based on potential for reduced cooling and increased firing temperatures. In this work, two static hot section components — the first stage turbine vane and the first stage turbine tip shroud (outer casing above the blade) — of a mid-sized power generation engine were modeled. Informed approximations about part geometry and cooling architectures were made to determine cooling requirements of each part. Thermal boundary conditions for the turbine tip shroud and turbine vane were generated as a function of coolant mass flow rate using data from literature and applied to a 2D finite element analysis of the parts to determine maximum temperatures for both metallic and ceramic materials. A gas turbine cycle model was developed to simulate the performance of a mid-sized power generation turbine, and used to determine increase in efficiency due to reduction in cooling requirement for the CMC part compared to a conventional metal superalloy-based part. Potential reduction in chargeable cooling seen for the tip shroud ring was between 0.09% and 0.4% of the compressor mass flow rate, which corresponds to an increase in thermal efficiency between 0.11% and 0.45%. A similar analysis of the turbine vane resulted in a cooling reduction of 10.71% at the maximum turbine entry temperature considered which corresponds to a 3.4% increase in thermal efficiency.
Performance and Control of the Primary Heat Exchanger in a Closed-Loop sCO2 Brayton Cycle With Solid Fuel Combustion
Authors: Schooff Brian , Roy Rajarshi , Smith Fletcher , Tree Daniel , Iverson Brian D. , Chiodo Andrew , Held Timothy J. , Miller Jason , Bowan Brett , Sedlacko Kyle , Johnson Michael , Montgomery Scott , Fry Andrew
Published: August 2024

The supercritical carbon dioxide (sCO2) Brayton cycle has been studied for a variety of heat sources as a replacement for the steam-Rankine cycle with higher thermal efficiency in power plants. The lack of a phase change in this cycle enhances the energy efficiency but also increases the likelihood of overheating of the heat exchanger tubes, especially when using solid fuels. The rapid sensible heating of the working fluid requires careful management of the temperature profile of the heat exchanger tubes inside the boiler. It is necessary to identify the system response of the controlling parameters of the system on the temperature profile of the primary heat exchanger (PHX) which can be used in the development of a model predictive controller (MPC) to manage the PHX surface temperature. A 1500 kWth solid fuel furnace (L1500) was retrofitted with a PHX and turbomachinery to investigate the use of solid fuel combustion with the sCO2 Brayton cycle. The PHX design requires limiting the PHX to a maximum surface temperature of 1089 K (1500 °F) and a maximum rate of change of 100 K/h. CFD modeling and operational data of the L1500 system showed that the firing rate, sCO2 flowrate, and refractory wall temperature significantly impact the temperature profile of the PHX. It is also expected that the amount of excess air will be a critical controlling parameter. Operational data showed that handling measurement noise will be vital to developing a predictive model of the heat transfer to the PHX.
Performance Comparison of Different Leading Edge Cooling Layouts Considering Inlet Swirl
Authors: Hu Kexin , Zhang Zhen , Su Xinrong , Yuan Xin
Published: August 2024

In modern aero-engine and gas turbine, the interaction between the combustor and the turbine has a significant impact on both aerodynamic and cooling performance of the turbine. Due to the interaction between the combustor and the turbine, non-uniform distributions of temperature and velocity can be observed on the inlet surface of the turbine, which notably affect the performance of turbine blade. The primary research interest of this work is to improve the cooling performance by optimizing the layout of the cooling holes according to the researches on the influence of swirl. First, cooling performance comparison of different inlet swirl is conducted using the measurement based on Pressure-Sensitive-Paint (PSP) technology. The swirl generator with the swirl number 0.778 is used to simulate the non-uniform velocity inlet and the related distance of vane was changed. As the swirl which core has the same circumferential position with the leading edge caused the worst influence to film cooling and made the coverage of film become highly asymmetric, then asymmetric cooling hole layouts, which cooling hole distributions driven by sinusoidal function, were studied by numerical methods and find they can clearly improve the cooling performance on swirl condition. Lastly, based on the experimental results and the analyses, a new layout based on the stagnation line is proposed, which can increase the uniformity of film cooling effectiveness and the performance is verified by PSP experiment. The new layout can increase the area-averaged film cooling effectiveness up to 9.7% under high blowing ratio and reduce the standard deviation of film cooling effectiveness to 24.3% under low blowing ratio. Thus changing the layout of film holes especial the leading edge is an efficient and practical method to improve the cooling performance under swirl condition.
Experimental and Numerical Comparison of Two Turbine Vane Frame Designs
Authors: Krajnc Nicolas , Hafizovic Asim , Wiesinger Lukas , Mangini Francesco , Sterzinger Patrick Zeno , Patinios Marios , Göttlich Emil
Published: August 2024

This paper presents an experimental study supported by numerical simulations of the performance of two turbine vane frames (TVFs) at various purge and TVF inlet swirl conditions representing both on- and off-design operation. The turbine vane frame (TVF) serves as a structural link connecting the last high-pressure turbine stage to the first low-pressure turbine stage, functioning as a vane row for the latter. The two configurations considered share a common fully purged high-pressure turbine stage, followed by distinct TVF and LPT rotor setups. Of the two TVFs considered, TVF1 features a single-splitter, while TVF2 incorporates a twin-splitter architecture.

The experiments took place at Graz University of Technology’s Transonic Test Turbine Facility (TTTF). The steady RANS simulations use 2D inlet boundary conditions derived from measurements and provide additional insights into critical flow phenomena.

The dataset includes purge derivatives with three purge flow rates (PFR) of 0%, 50%, and 200%, the aero design point (ADP) with 100% PFR, and one swirl derivative with positive incidence for each case.

Both configurations exhibit unique flow phenomena, leading to distinct ‘regions of sensitivity’ for each duct design. Due to the positive incidence and low aspect ratio strut design, TVF1 demonstrates a pronounced UPV that affects almost the entire span at the duct exit. Additionally, the UPV is found to be enhanced by the radial pressure gradient imposed by the duct’s second bend.

In contrast, TVF2 experiences a region of low momentum flow at the hub, due to the combination of axial diffusion (as a result of area increase) and high flow turning. This low momentum flow region is manifested as a band of very low axial velocity, spread evenly around the circumference between the airfoil trailing edges and the LP-rotor.

Purge variations exert differing impacts on the investigated geometries, with TVF2 showcasing greater robustness to purge derivatives.
Effects of Inlet Total Pressure Distortion on the Performance of a Two-Stage Transonic Fan
Authors: Qiu Jiahui , Zhao Hongliang , Yang Chen , Du Juan , Zhang Min , Qin Yaolong
Published: August 2024

Improving the understanding of the interaction between multistage fan and an inlet total pressure distortion is benefical to design an advanced compression system and stabilizing measures with strong anti-distortion ability. Full-annulus unsteady simulation is applied in a two stage fan to supplement the physic of distorted flow transfer that is difficult to measure in the experiment. The tip flow fields of Rotor 1 with distorted inflow obtained by unsteady computations agree well with experiment. Total temperature distortion generates as flow passes through the first stage. The results obtained by orbit-method show that the position of the second stage of maximum flow separation locates in where the rotor turns out the lowest total pressure region and turns into the highest total temperature region. The application of inlet distortion distinctly alters the blade loading of Rotor 1, while has negligible effect on Rotor 2 loading, resulting in the blade loading of R1 is greater than that of R2 above 75% span. The process of disturbance generation-development-suppression is captured by unsteady simulations, which is consistent with measurement data. The stall inception finally generates at the tip of Rotor 1, and its circumferential position locates in where rotor turns out of distortion. Distinct from previous studies, the total pressure distortion level, with a large enhancement by the first stage, progresses through the fan with a significantly attenuation by the second stage, and so is the total temperature distortion level.
Investigation on the Flow Mechanism and Dynamic Response Performance of Efficient Fluidic Thrust Vectoring Serpentine Nozzle
Authors: Shi Jingwei , Hui ZhongHao , Zhou Li , Wang Zhanxue
Published: August 2024

High maneuverability, wide speed range, and strong stealth are the key technical requirements for the exhaust system of advanced fighters. The main technical manifestation of high maneuverability and wide speed range is thrust vectoring technology, and the main technical manifestation of strong stealth is the serpentine nozzle. The efficient fluidic thrust vectoring (FTV) serpentine nozzle not only has the above advantages, but also has simpler structure, lighter weight, and quicker vector response. There are complex pressure gradients and strong swirl characteristics inside the serpentine nozzle, such that efficient FTV design of the serpentine nozzle faces greater challenges than conventional nozzles. Therefore, it is important to conduct in-depth study on the efficient FTV serpentine nozzle. This paper conducted a numerical investigation on the flow mechanism and dynamic response performance of an efficient FTV serpentine nozzle. Results show that the depth of the secondary injection can be effectively increased by setting an additional auxiliary injection in front of the secondary injection, which results in the increase of the angle of the induced shock wave and a more obvious deflection of the mainstream. For the high pressure ratio, the time of thrust vectoring formation of the efficient FTV serpentine nozzle is about 10ms, in which the sudden rise of the thrust vectoring angle occurs in 1.4ms. After about 12ms, the flow and thrust vectoring angle tend to be stable. The recovery time of the efficient FTV serpentine nozzle does not exceed 10ms, which is about half the time of the thrust vectoring formation. Generally speaking, the dynamic response of the efficient FTV serpentine nozzle can be completed in 20ms, which is faster than that of the conventional mechanical thrust vectoring nozzles, and its thrust vectoring response rate is about 20–50 times that of mechanical ones.
Investigation of the Heat Transfer Performance in a Double-Wall Cooling Configuration Under the Effect of Wall Curvature at Rotating Conditions
Authors: Wang Xianyu , You Ruquan , Li Haiwang
Published: August 2024

This paper presents an experimental investigation of a double-wall model derived from simplified real turbine blades. The study examines the influence of three distinct wall curvatures and rotation on the internal flow patterns and heat transfer characteristics within the double-wall cooling configuration. It elucidates the mechanisms by which wall curvature and rotation effects impact the performance of the double-wall cooling unit. Conducting flow characteristic experiments on three different wall curvature specimens (flat, convex curvature, concave curvature), experiments were carried out under stationary conditions and at different rotational speeds (30rpm, 60rpm, and 120rpm) for each respective condition. The Particle Image Velocimetry (PIV) experimental results reveal that the flow within the cavity of the double-layer wall cooling configuration is characterized by a complex, three-dimensional, multi-vortex flow, primarily dominated by impingement/effusion dynamics. Wall curvature modifies internal flow characteristics by altering the geometry of the impacted surface and the relative shock distance. Notably, this curvature has a substantial impact on mainstream flow rates and key vortex structures. Additionally, rotation induces centrifugal and Coriolis forces, which enhance the heat transfer capabilities of the double-wall cooling mechanism. The flow can reflect heat transfer, and the analysis of the results from the flow characteristic experiments reveals that, compared to the square double-wall structure, the double-wall structure with convex curvature overall exhibits better heat transfer efficiency, while the one with concave curvature shows poorer heat transfer performance. This is primarily due to the influence of wall curvature on the flow in the main flow region inside the cavity, as well as on vortex structures that play a crucial role in heat exchange. At lower rotational speeds, rotation enhances the heat transfer efficiency of the double-wall cooling structure.
Fatigue Crack Growth of Turbine Disc Part Considering Effect of Shotpeen Nonlinear Stress Gradients Using Finite Element Based and Numerical Methods
Authors: Ertekin Şevket , Yılmaz Adem
Published: August 2024

Crack growth in mechanical components is affected by the residual stress gradient around the crack zone. Shot peen is one of the cold working processes used to generate compressive residual stress layer on gas turbine engine parts. The aerospace industry frequently uses shot peening to increase the fatigue life of mechanical components. In this study, mechanical properties of disc part made of nickel-base super alloy material are modified by applying shot peen residual stress parameters. Three-dimensional residual stress modification is transformed to finite element model of the uncracked area. Then, surface semi-elliptical crack introduced in the finite element model on the maximum principal stress orientation on the surface. One of the most recent, adaptive remeshing capabilities are used during simulations by using Ansys SMART. Crack front element division and incremental crack advance in each step of FEM are fine-tuned by different parameter sets. After each simulation step, new crack front is calculated, and finite element model is updated consequently. Then, crack growth is calculated using mixed-mode maximum circumferential stress criterion until the failure. Similar procedure is performed to create a numerical weight function solution by employing empirical formulas. Shot peen effect is converted into the residual stress intensity factor by using weight function method. Yau’s weight function formulation was used to calculate residual stress intensity values with Newman-Raju surface crack solution. This residual stress intensity profile mostly affects the stress distribution in a compressive stress manner causing lower crack growth rates. This yields a variation on SIF around the crack tip zone. At that point, fatigue crack growth is also calculated by numerical solutions. Results are compared with FEM based mixed-mode crack growth and differences in results are highlighted. Applicability of FEM based crack growth method on shot peen application is investigated. The role of the shot peen operations and consequence of surface residual stress during crack growth is emphasized.
Model Order Determination for Modal Parameter Estimation: Application to a Composite Fan Stage
Authors: Jorajuria Corentin , Gibert Claude , Esteves Cécile , Thouverez Fabrice
Published: August 2024

Experimental methods are necessary to quantify structural damping. Among these methods, modal testing of bladed disks are of particular interest because it provides an efficient experimental characterization of these structures which are critical parts of aeronautic turbojet engines. This work presents techniques to determine the optimal order of subspace state-space identification methods for modal parameter estimation of a realistic fan stage. Indeed, the order of the identification model is unknown during modal analysis requiring techniques to determine which model order should be used for parameter estimation. To investigate these techniques, several methods to estimate the optimal model order are reviewed. A specific focus is proposed on the determination of model order through statistical tests as these techniques have the benefits of providing indicators along with a threshold built over hypothesis testing and a probability of rejection. In order to further analyze model order determination techniques, some of these techniques are evaluated by means of a numerical model of a realistic fan stage, hence making possible to assess the performances of estimation methods close to experimental conditions. In particular, estimation in a context of high modal density as well as model order determination through “M-test” are addressed using this model. After assessing the implemented estimation method over the numerical model, this method is applied over experimental data obtained by performing modal tests over a full-scale composite rotating fan in vacuum condition.
Fuel Property Impact on Lean Blow Out for Sustainable Aviation Fuels in Gas Turbine Combustors
Authors: Dasgupta Debolina , Som Sibendu
Published: August 2024

Sustainable Aviation Fuels (SAF) offer a solution for lowering the carbon emissions produced by the aviation sector. However, these fuels have different properties than traditional jet fuels. In order to understand the effects of changes in fuel properties on the behavior of flames, Large-Eddy Simulations of the Referee Rig are performed under stable conditions. The fuel used in these simulations is the average jet fuel, A-2, which serves as the reference fuel. Perturbations are made to the fuel’s density, viscosity, and heat of combustion to determine the impact of each on the behavior of the flame. The combined effects of two or three properties are also analyzed. Changes in density and kinematic viscosity have an impact on secondary atomization and vaporization, which in turn modify flame symmetry and droplet sizes near the flame anchoring region. An increase in heat of combustion leads to an increase in heat release and temperature within the combustor. Overall, a reduction in density, kinematic viscosity, and an increase in heat of combustion increase flame resilience, which results in a reduction in the LBO GER.
The Axial-Throughflow Influence on the Taylor Vortices In Taylor-Couette-Poiseuille System
Authors: Li Siyi , Du Qiang , Xie Yaguang , Liu Guang , Lian Zengyan , Luo Yifu , Xie Lei
Published: August 2024

Integrating axial throughflow into the Taylor-Couette systems enhances the complexity of the Taylor-vortices structure, which is a critical configuration positioned between the high-pressure and low-pressure shafts in aeroengines where there exists a rotational speed difference, referred to as Taylor-Couette-Poiseuille (T-C-P) system. The axial throughflow and temperature difference influence the characteristics of cooling airflow’s resistance and heat transfer, and consequently affects the rotor-stator’s axial/radial clearance, much further, hence, affects the performance and efficiency of the aero-engine. To investigate the impact of axial throughflow on the T-C-P system, we conducted direct numerical simulations (DNS) to analyze the axial-throughflow behavior within the T-C-P system. As the magnitude of axial throughflow increases, the initially uniform distribution of Taylor vortices becomes discontinuous and fragmented. With further enhanced throughflow, the entire Taylor vortices are propelled to downstream with an averaging axial velocity. Eventually, the Taylor vortices are expelled and fully disappeared as the axial throughflow becomes sufficiently large, resembling the flow characteristics of a Poiseuille system. The flow field is predominantly influenced by the rotating inner cylinder at the relatively lower magnitude of axial throughflow’s velocity. As the axial Reynolds number surpasses 100, the system transitions to being dominated by the axial throughflow. Therefore, this evolution highlights the profound influence of axial throughflow on the transition of Taylor vortices and lays the groundwork for subsequent research on the flow control and heat transfer in the T-C-P system.
A Holistic Conceptual Synthesis and Analysis of Fuel Cell System Architectures Using 1D Coupled Thermofluid and Electrochemical Lumped Parameter System Simulation
Authors: Goldenberg Vlad , Conser Ben , Joly Clement , Moroz Leonid
Published: August 2024

In this work, several fuel cell system architectures are described and analyzed. The architecture variability includes uncoupled/coupled cooling and aspirant systems, the inclusion or exclusion of an energy recovery turboexpander on the exhaust, and, for those that include a turboexpander, the inclusion or exclusion of thermal recuperation.

It is recognized a-priori that certain architectures will have specific advantages over others. It is also recognized that there are several performance metrics that may be sought. They include power system efficiency, gravimetric power density, volumetric power density, and specific cost per capacity. The analyses carried out in this work lead to a novel way to minimize the cost of a fuel cell power system. Specifically, knowing that the fuel cell proper represents the highest cost component of a fuel cell based power system, it is shown that one can optimize for maximum “bang for the buck” in a surrogate fashion in a holistic system analysis. The key to being able to achieve this is having a reliable electrochemical analysis model of a cell coupled with an overall system simulation model. Thus, for a variation of parameters, it can be predicted how relative fuel cell stack specific power density changes with parameter variation. The outcome of this paper is a documentation of several integrated fuel cell system architectures with a parametric analysis and resulting performance metrics of each system when independently optimized for efficiency, power density, and fuel cell specific power capacity, showing an improvement of about 15% over a simple baseline.
Implementation of Artificial Intelligence for Aircraft Engine Health Monitoring and Prognostics
Authors: Aditya Aditya , Nikolaidis Theoklis , Manuel Arias Chao , Togni Simone
Published: August 2024

Improving the availability and reliability of aircraft engines is paramount in managing the aircraft fleet’s efficiency. While previous efforts have primarily focused on condition-based monitoring and Remaining Useful Life (RUL) prediction based on physics-based models, this paper introduces a novel approach to Engine Health Monitoring (EHM) using deep learning models. In particular, this work leverages critical engine parameters such as surge margin and exhaust gas temperature margin for interpretable EHM and prognostics. We present three deep learning models, namely, the Multi-Layer Perceptron (MLP), Convolutional Neural Network (CNN), and Long-Short Term Memory (LSTM), optimized for these tasks. The models were trained using synthetic data of 100 CFM 56 5B Turbofan engine-inspired models, simulating various flight cycles at steady-state cruise conditions using TURBOMATCH software (Cranfield University in-house aircraft engine performance simulation tool). The degradation in each engine was based on mass flow capacity and efficiency variation in the fan, compressor, and turbine, which is the effect of fouling, erosion, corrosion, etc. Unlike the existing datasets, this study deployed full factorial degradation of engine components and a wide range of degradation scenarios.

Results demonstrate the competitiveness of the proposed models, as evidenced by low Root Mean Square Error (RMSE) values. The CNN model performs well in health monitoring, achieving an RMSE of 0.0148 health margin prediction. In contrast, the LSTM model proves most effective in predicting Remaining Useful Life, with an RMSE of 53.64 flight cycles. In conclusion, deep CNN and LSTM models showed a promising method for accurate engine condition monitoring and RUL predictions.
3D Temperature Evaluation of the Vane Based on Fluid-Network Method
Authors: Zhang Siyuan , Li Xueying , Ren Jing
Published: August 2024

With the continuous increase of inlet temperature of the gas turbine, the design of turbine cooling structures is facing great challenge. The fluid-network method is widely used in the initial stage of the turbine design due to its advantages of high speed and precision. However, this method is difficult to achieve 3D temperature evaluation of turbines and it fails to meet the demands of engineering specifications.

This research develops a 3D evaluation method for the vane based on the fluid-network method. The method translates cooling structures into topological elements, which directly solves the momentum and energy equations. Correlations summarized from experimental data was combined to obtain the pressure, flow rate, temperature, and heat transfer coefficient distribution of the cooling elements quickly and accurately. This research compared the calculation results of the 3D evaluation method and Computational Fluid Dynamics (CFD) method with design prediction. The results show that the errors of the two methods are at the same level, and the 3D evaluation method has higher computational efficiency. It is proved that the 3D evaluation method can quickly predict the 3D temperature distribution and cooling efficiency of different cooling structure layouts in the initial stage of turbine design. Therefore, this research lays a foundation of the optimizing of cooling structures, which could support the design of the next generation high-performance turbine.
Film Superposition Characteristics With Laidback Fan-Shaped Holes Under the Influence of Internal Crossflow
Authors: Liu Haoyang , Du Qiang , Xu Qingzong , Xu Jiawei , Xu Guangyao , Li Hongye , Wang Pengfei
Published: August 2024

In the serpentine passage of actual rotor blades, the coolant at the inlet of the film hole has an internal crossflow. The internal crossflow significantly influences the film cooling effectiveness of multi-row film holes. This paper presents a numerical investigation of the superposition characteristics of multiple rows of laidback fan-shaped holes under the influence of internal crossflow. The numerical simulations utilize the RANS method considering the effects of blowing ratio, crossflow velocity ratio, arrangement patterns, and row-to-row spacing of the internal crossflow on the superposition characteristics of film holes. The results indicate that film cooling effectiveness exhibits a distinctly asymmetric distribution under crossflow conditions. At different blowing ratios, there exists an optimal crossflow velocity ratio, at which the laterally averaged film cooling effectiveness is maximized. The crossflow-to-jet velocity ratio (VRi) is utilized to comprehensively evaluate the impact of blowing ratios and crossflow velocity ratios, the range of high area averaged film cooling effectiveness is accurately captured. Regarding the study of arrangement patterns and row-to-row spacings, it has been found that under identical coolant mass flow rates, the staggered arrangement is better than the inline arrangement in both laterally averaged film cooling effectiveness and cooling uniformity. Meanwhile, reducing the row-to-row spacing leads to an improvement in laterally averaged film cooling effectiveness. Finally, an assessment of the Sellers model’s applicability under crossflow conditions revealed that it demonstrates good applicability in cases of staggered arrangement with lower blowing ratios.
Application of Deep Learning for Fan Rotor Blade Performance Prediction in Turbomachinery
Authors: Fesquet Jean , Bauerheim Michael , Rojda Ludovic , Bousquet Yannick , Binder Nicolas
Published: August 2024

Turbomachinery fan optimisation is a complex multidisciplinary process, which forces engineers to rely on strong theoretical assumptions and/or can be very computationally expensive. Additionally, with new constraints arising, such as distorted inflow in boundary layer ingestion cases, it is essential to find surrogate models able to account for the requirements and produce satisfying results, while capitalizing on the computational and experimental data already produced on other (e.g. previously developed) configurations. Towards this objective, the present study aimed at predicting the performance of the rotor of a turbomachine fan stage using Deep Learning (DL) techniques. These approaches have been showing increasingly convincing results in recent times, yet usually applied to toy problems or simplified configurations. Thus, this work evaluates the feasibility of applying DL models to optimise the shape of realistic fan rotor blades. To that end, a pipeline is presented to generate and mesh new geometries, run simulations, and finally train deep neural networks to be used as surrogates for performance prediction. In this framework, a u-net type deep neural network was used to predict 2D wake-flow fields of entropy and two 0D metrics, efficiency and pressure ratio, from the geometry of the blade and its operating conditions. To reduce the complexity of the predictive tasks, a transformative approach is used, by opposition to a fully generative one. For model testing and training, 75 geometries were built through interpolation of pre-existing, parametrised rotor blades. In turn, RANS computations at various operating points were performed. The model was compared to POD-Kriging techniques. Results showed that the neural network was only a slight improvement on an iso-geometry data-set, but widely outperformed the POD-Kriging model on the multigeometry data-set. As a conclusion, it provided a good proof of concept to learn flow field views and global performance metrics on realistic, 3D, fan rotor geometries to be later used for optimisation.
Development of Compact and Hermetic ORC Turbine Generator With Upgraded Cooling Capability
Authors: Tanaka Toshimitsu , Takata Ryo , Hirado Takuma , Kawanami Akira
Published: August 2024

In this paper, a hermetic and oil-free turbine generator for a cryogenic ORC is suggested and investigated. The generator mainly consists of a high-speed generator, a two-stage supersonic turbine, and magnetic bearings. Based on the hermetic design concept, these components are in a common casing. To upgrade the cooling capability of the generator, heat dissipation fins are installed between the 1st and 2nd stage of the turbine. Performance of the turbine generator was preliminarily investigated by CFD calculations. These results show that the turbine efficiency peaks at 16,000rpm under the design pressure ratio condition. Under the same condition, it is also predicted that comparatively high static pressure recovery coefficient and low total pressure loss can be obtained through the flow path with the fins. Moreover, a series of experimental campaign were conducted on an ORC test rig using −96 deg.C liquid nitrogen and 50 deg.C warm water as cold source and heat source, respectively. These results indicate that the target power output was achieved and the installed heat dissipation fins are effective to enhance the cooling capability of the generator. It was also indicated that under comparatively high loaded conditions, the turbine power output can be increased by heat transferred from the generator.
Navigating Technological Risks: an Uncertainty Analysis of Powertrain Technology in Hybrid-Electric Commuter Aircraft
Authors: Diamantidou Dimitra-Eirini , Soibam Jerol , Zaccaria Valentina , Kalfas Anestis
Published: August 2024

This study addresses the uncertainties in hybrid-electric powertrain technology for a 19-passenger commuter aircraft, focusing on two future Entry-Into-Service timeframes: 2030 and 2040. The methodology is split into a preliminary optimization of aircraft design based on nominal technology scenarios followed by Monte Carlo simulations to investigate the impact of diverse technology projections and distribution types. Advanced surrogate modeling techniques, leveraging deep neural networks trained on a dataset from an aircraft design framework, are employed.

Key outcomes from this work reveal a marked increase in computational efficiency, with a speed-up factor of approximately 500 times when utilizing surrogate models. The results indicate that the 2040 EIS scenario could achieve larger reductions in fuel and total energy consumption — 20.4% and 15.8% respectively — relative to the 2030 scenario, but with higher uncertainty. Across all scenarios examined, the hybrid-electric model showcased superior performance compared to its conventional counterpart. The battery specific energy density is proved to be a critical parameter of the aircraft’s performance across both timeframes. The findings emphasize the importance of continuous innovation in battery and motor technologies to target towards greater system-level efficiency and reduced environmental impact.
Optimal Part-Load Performance of Supercritical Carbon Dioxide Brayton Cycles During Inventory Control
Authors: Gupta Shrey Sahai , Kumar Pramod
Published: August 2024

Supercritical carbon dioxide (sCO2) cycles are gaining attention for their efficiency and low carbon footprint in power plants. This study focuses on optimizing the performance of a 5 MW simple recuperated sCO2 Brayton loop during inventory control, a recommended strategy for maximum part-load efficiencies. Variable speed operation of turbomachines is explored to enhance part-load efficiency across the operating range, contrasting with the baseline case of constant turbine and compressor speeds. The analysis, which is based on an analytical formulation and validated component models reveals that part-load efficiency can be improved by variable speed operation of the turbomachines. The decoupled shaft systems outperform coupled or single shaft systems. Further, part-load efficiency deterioration in case of constant speeds has been discussed in depth. A unique feature of this study is its modelling methodology. The compressor model is derived by modifying an ideal gas compressor model to account for the behavior of a real gas compressor. Component matching is performed systematically to estimate cycle conditions accurately. This work enhances our understanding of sCO2 cycle operation under part-load conditions, providing valuable insights on control strategy and inventory management system design for fast response and improved efficiency.
The Impact of Inflow Unsteadiness on Loss Prediction
Authors: Przytarski Pawel J. , Lengani Davide , Sandberg Richard
Published: August 2024

Stagnation pressure loss coefficient is still the most commonly used loss metric for performance evaluation and is routinely used to validate simulations. This is because it is easy to measure and readily available from the experiments. However, it was previously shown (GT2023-102767) that the stagnation pressure loss coefficient can become unreliable when high levels of inflow unsteadiness are present.

As the current design trends are moving towards more compact machines and higher work coefficients, the levels of unsteadiness are likely to increase. It is therefore desirable to assess how higher inflow unsteadiness levels affect the performance of new blade designs and what loss metrics should be used to reliably estimate it.

Motivated by the need to understand how performance prediction changes under highly unsteady inflow conditions, we perform a series of high fidelity scale resolving simulations. We use this data to construct energy budgets for a variety of mid-span compressor cases with varying Reynolds numbers and inflow turbulence intensities. This allows us to systematically assess the impact of inflow conditions on loss prediction when using stagnation pressure based loss metrics. Stagnation pressure loss coefficient was found to be least reliable for the high inflow turbulence intensities and at high Reynolds numbers.
Investigating the Impact of Steam Enhancement on Combustion in a Swirl-Assisted Jet-Stabilized Gas Turbine Combustor
Authors: Izadi Saeed , Kislat Oliver , Zanger Jan , Seliger-Ost Hannah , Kutne Peter , Aigner Manfred
Published: August 2024

A newly developed gas turbine combustor system based on the swirl-assisted jet-stabilized concept using Jet A-1 and natural gas as reference fuel is tested under wet conditions to evaluate its combustion characteristics in the presence of steam. The effect of steam injection into the gas turbine combustor under both spray and superheated liquid fuel injection conditions is studied experimentally on an atmospheric test rig. The experiments are conducted at atmospheric pressure and an elevated combustion air temperature of 305°C. To evaluate the effect of steam injection on combustion performance, the water-to-gas ratio (WGR) is varied from 0 to 32%. Even at very high WGR levels, the results show virtually no combustion thermoacoustic instability during operation. With increasing WGR = 0 to 16% and at stoichiometric condition, NOx reductions of −82% to −100% were observed during Jet A-1 and natural gas combustion, respectively. It is shown that the reduction of the combustion zone temperature due to the steam acting as a heat sink is the main cause of the NOx decrease. For both wet and dry conditions, CO levels remained fairly similar. Both flame length and flame height above the burner increased with increasing WGR. This is due to the reduced reactivity of the fuel-air mixture. The operating range of the burner remained fairly constant for Jet A-1 until WGR = 20%, while it decreased significantly with increasing WGR for natural gas combustion. While the effect of the WGR on CO was modest, the greatest effect of the WGR was on the heat release zone intensity at a constant air to fuel ratio. In reducing the NOx levels of Jet A-1 and natural gas combustion, both thermal and chemical effects of steam injection were observed. However, steam acting as a heat sink and lowering the flame temperature, thereby reducing the thermal NO formation rate, was the dominant factor in NOx reduction.
Joule Cycle-Based Waste Heat Recovery From Heavy-Duty Truck Engines
Authors: Kenkoh Kesty Yong , Kodaboina Raghu Vamsi , Gubba Sreenivasa Rao , Turner James W. G.
Published: August 2024

Growing global concern over the impact of carbon emissions has spurred many nations to aim to achieve net-zero carbon emissions within the 2030 to 2050 timeframe. A significant contributor to these emissions is the transport sector, responsible for a substantial 23% of total carbon emissions, with heavy-duty (HD) transport accounting for 40% of this cumulative figure. This study explores waste heat recovery (WHR) via the utilization of multiple working fluids in closed and open Joule cycles from the exhaust gas of the Volvo D13 truck engine operating on the European Stationary Cycle (ESC). Furthermore, this paper investigates the potential for recovering heat from the gases in the exhaust gas recirculation (EGR) circuit and examines the impact of pressure drops within the heat exchangers on the WHR process. The design and analysis of these cycles are executed using Aspen Plus, complemented by a one-dimensional D13 engine simulation model in GT-suite to provide the essential exhaust and EGR properties. This study also aims to offer more insight into the viability of pursuing WHR for truck applications using the Joule cycle.
A Numerical and Experimental Study of Five-Hole Probe Calibrations in Low-Speed Flows
Authors: Jeong Dahae , Guimarães Tamara
Published: August 2024

This study aims to establish fundamental steps for developing an optimal methodology to enhance experimental probe calibration. Multi-hole pressure probes have been extensively used to measure the airflow around airfoils, wings, and other surfaces in the field of fluid dynamics. Five-hole probes are broadly used in wind tunnel testing and aerodynamic survey to collect data on velocity, pressure distribution, and flow characteristics. These measurements help in understanding the aerodynamic performance of new aircrafts, planes, and aerospace vehicles to improve the efficiency and lower environmental costs, however, the calibration process for these probes conventionally demands considerable effort, time, and cost. The purpose of this study is to leverage advanced instrumentation and measurement techniques to ensure optimal calibration of probes, thereby minimizing data uncertainty and maximizing accuracy. The automated calibration facility for data acquisition secures outstanding repeatability. A computational study determined an optimal probe placement in a calibration jet to read accurate measurements by investigating the region around the probe surface and nozzle. To shorten the calibration time, experiments for finding an optimized measurement incremental step were implemented and discussed comparatively. Experimental calibration maps were generated using non-dimensional pressure coefficients to describe flow characteristics within predetermined flow conditions. The experimental calibration map was assessed by quantitative comparison, and compared to a high-resolution numerical calibration map. This methodology including research findings is expected to facilitate the study for investigating numerical and experimental calibration in subsonic flows by obtaining great insights into advanced calibration from the present study.
Showerhead Film Cooling Mechanism and Superposition Characteristics of Turbine Blade Leading-Edge
Authors: Li Bing-ran , Liu Cun-liang , Ye Lin , Zhang Fan , Zhou Tian-liang
Published: August 2024

Based on the turbine blade model, the film cooling effectiveness data of single rows of holes at different positions were obtained through numerical simulation, and the superposition characteristics of multiple rows of holes under different average blowing ratios were studied. The applicability of the Sellers superposition formula to the blade leading-edge is discussed. The showerhead film cooling effectiveness distribution of the leading-edge was studied through pressure sensitive paint (PSP) experimental measurement, and the numerical simulation method was verified. The results show that the Sellers superposition formula accurately predicts the average film cooling effectiveness on the leading-edge surface under small and medium blowing ratios. Under large blowing ratios, the prediction accuracy of the superposition formula is significantly reduced. The strong interference of the mainstream and secondary jet flow and the formation of a vortex tube between multiple rows of holes are the main reasons for the failure of the two-dimensional superposition formula and the formation of a sheet-shaped high-film cooling effectiveness area under a large blowing ratio. Changes in the row-of-holes layout have an impact on the film cooling effectiveness distribution but have little effect on the prediction of the area average by the Sellers superposition formula. The experimental measurement data of film cooling effectiveness at large blowing ratios combined with the Sellers superposition formula constitute a reference for designing leading-edge showerhead film cooling structures, which have important application value for engineering design.