bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Reduced Order Model Based on Aerodynamic Influence Coefficients for Aeroelastic Computations in Transonic Compressors
Authors: Casoni Marco , Klausmann Fabian , Benini Ernesto 
Published: August 2024

Abstract
Reliable and computationally affordable aeroelastic simulations of compressor blades are of capital relevance today, as modern turbomachinery for aircraft propulsion are expected to meet stricter goals on weight saving and fuel efficiency through slender and highly-loaded geometries with a reduced number of blades, that may ultimately lead to a higher flutter susceptibility. In this paper, an aeroelastic reduced order model (ROM) based on the aerodynamic influence coefficient (AIC) technique for flutter simulation in transonic compressor blades is adopted to compute the aerodynamic damping for two resonance conditions. The ROM is capable of performing flutter simulations in both an uncoupled and a coupled way. In the former, the motion of blades is imposed as a travelling wave vibration pattern, with constant amplitude, frequency and phase, and the exchanged work between the fluid and the blade is used to assess stability; in the latter, a structural and an aerodynamic subsystem are built for each blade, exchanging displacements and forces respectively at the blade surface in a time-marching model. The key point in model order reduction is the accurate representation of unsteady aerodynamic forces. To this purpose a training simulation is setup, which relates the displacement of a blade to the induced aerodynamic loads on the neighbouring ones, called aerodynamic influence coefficients. In the uncoupled model the unsteady pressure field on the blade surface is adopted as AIC, while in the coupled version the AIC are the modal aerodynamic forces, related to the motion of blades with system identification techniques. The ROM is applied to the TU-Darmstadt Open Test Rotor geometry, a representative case of modern transonic compressor designs. Two resonance conditions are selected, where the crossing between a natural frequency and the rotational speed allows the experimental measurement of aerodynamic damping of the selected mode at several mass flows through a blade tip-timing system. Validation of the CFD model is performed by computing the compressor map in steady conditions and comparing the data against experimental measurements. After that, the uncoupled ROM accuracy is assessed, by comparing the aerodynamic damping for the two resonances at different mass flows and IBPA to full order flutter simulations adopting Fourier transformation and harmonic balance methods. The coupled ROM is then setup and compared to experimental data on damping ratio at the same conditions. The results prove the accuracy of the developed ROM, as well as a consistent reduction in computational cost compared to full order calculations.
Novel Microturbine Engine Test Stand for Rapid Assessment of New Materials and Manufacturing Procedures
Authors: Krizak Troy , Scott-Emuakpor Onome , Johnson Philip , D’Souza Kiran 
Published: August 2024

Abstract
New materials and advanced manufacturing techniques are essential for creating more effective, efficient, and innovative turbomachinery systems. The current process for developing these new components has many lengthy and costly steps, which slows the adoption of new designs and materials. This work outlines a new, easy to assemble and operate microturbine engine test stand that will allow for rapid testing of new turbomachinery component prototypes, materials, and manufacturing techniques. The goal for this test stand is to allow for quick proof of concept testing that can then be used to determine if full system demonstrations of the new technologies are desirable. The engine test stand will be implemented to demonstrate the performance of the newly designed, manufactured, and/or novel material hardware and their effects on engine performance at design speeds. In addition, the test stand will be supplemented by computational analysis tools that reduce the risk of catastrophic events. Moreover, these tools will be able to accurately predict failure to assure safe demonstrations while still gathering essential performance information. Analyses include, but are not limited to, understanding stage efficiency, total engine efficiency, structural dynamic responses, and rotordynamic assessments. This work discusses the key characteristics of the equipment and some initial results demonstrating the effectiveness of the new testing facility.
NASA HECC Geometry and Performance Review Part 1: Validation of a Computational Model for the Vaneless Diffuser Configuration With As-Manufactured Impeller Geometry
Authors: Robles Vega Gregorio , Bosshart Alec J. , Ni Michael , Ni Ron-Ho , Harrison Herbert M. , Nguyen-Huynh Tammy 
Published: August 2024

Abstract
An investigation of the NASA High Efficiency Centrifugal Compressor (HECC) vaneless diffuser configuration was performed. This multipart investigation presents an extensive validation of the computational model against experimental data. The validated model was then used to explore the effects of geometric differences between the as-manufactured and design-intent impellers. Lastly, the validated model was used for comparison against an experimental tip clearance study.
Part I of the investigation focused on describing the HECC vaneless computational model and its validation against the experimental data published in GT2023-103128. To generate the model, a verification of the manufactured impeller was performed and was confirmed to match the impeller CAD. Section data from the impeller CAD, referred to as the As-Manufactured geometry, were used for development of the computational model. Steady RANS simulations utilizing the Wilcox K-Omega 98 turbulence model and a multiblock structured mesh were used to conduct a mesh convergence study. The resultant mesh was then used for simulations at both designspeed and off-design speed conditions. Due to the challenges and uncertainties regarding the HECC performance and geometry, the model was extensively validated for use in Parts 2 and 3 of the paper The simulations compared well to data in both 1D and 2D terms for the major performance metrics of efficiency, total pressure rise, and total temperature rise. Based on the observed results the model was deemed validated and was used in the latter two parts of the multipart investigation.
Impact of Turbine-Strut Clocking and Turbine Outlet Swirl on the Heat Transfer and Film Cooling in an Aggressive Turbine Center Frame
Authors: Jagerhofer Patrick R. , Glasenapp Tobias , Patzer Bastian , Göttlich Emil 
Published: August 2024

Abstract
This study focuses on the thermal impact of the clocking position of the high-pressure turbine (HPT) vanes with respect to the turbine center frame (TCF) struts and the thermal impact of the HPT outlet swirl. The TCF is a stationary duct equipped with non-turning airfoils (struts), and it connects the HPT to the low-pressure turbine (LPT). The heat transfer coefficient and the purge film cooling effectiveness are measured in an aggressive TCF for two turbine-strut clocking positions and two HPT outlet swirl levels. The measurements are carried out in a product-representative 1.5-stage HPT-TCF-LPT vane configuration under Mach-similarity. The unshrouded HPT is fully purged with four individually adjustable purge flows, and the film cooling effectiveness of these purge flows in the downstream TCF is investigated.
The biggest influence of turbine-strut clocking was found for the heat transfer coefficient on the struts. By clocking the HPT vanes by half a vane pitch from the thermally least to the most favourable position, a significant heat transfer reduction was achieved for both, the nominal and the increased HPT outlet swirl. Increasing the HPT outlet swirl increased the flow incidence of the TCF struts and affected the heat transfer along the struts significantly. On the TCF hub, the averaged heat transfer coefficient and the averaged purge film cooling effectiveness responded relatively robustly to all imposed operating point deviations with differences of less than 2%. However, the effects on the local heat transfer and film cooling distributions on the hub were more significant.
Design of a Multi-Purpose High-Speed Rotating Rig, for the Rapid Testing of Compressor, Turbine and Fan Single Stages
Authors: Harman Leon , Mahon Kristian , Lock Richard , Bradwell Thomas , Atkins Nick , Yasa Tolga , Taylor James 
Published: August 2024

Abstract
This paper summaries the design and analysis activities completed in the development of the new high-speed rotating rig for the National Centre for Propulsion and Power (NCPP) located at the Whittle Laboratory, University of Cambridge, UK. The test rig is intended to provide flexibility to work in multiple modes to test axial compressors, turbines, or fans. To facilitate this functionality, the rotating rig must be able to drive the test article via an electric motor or be driven by the oncoming airflow, with the motor acting as a generator. The primary objective of the test rig is to enable rapid testing of single stages over a range of test conditions, from a blade relative Mach number 0.5 up to 1.3 and from a Reynolds number based on chord from 80,000 up to 2,000,000.
This paper details five of the main design considerations which were pivotal in enabling the ability to test any configuration rapidly and at full engine conditions. First, the choice of the overall architecture to facilitate rapid access and strip down. Second, the design methodology for ensuring uniformity of flow distribution at the inlet to the test articles. Third, design of the rotatives and driveline so that it can withstand axial loading in both directions whilst remaining adequately sealed. Fourth, the detailed rotordynamic design which ensures the test articles can be operated over a wide range of speeds and sizes. Finally, a rapidly removeable containment solution to mitigate against blade-off or disc-burst failure modes.
A Surrogate Model Approach to Predict O&M Cost for Combined Cycle Power Plant
Authors: Choi Woosung , Webb Bobby M. , Noble David R. 
Published: August 2024

Abstract
For carbon-neutral 2050, the proportion of renewable energy is increasing, and the problem of power grid instability is emerging due to the load variability of renewable energy. For grid stabilization, the need for flexible operation of gas turbine combined cycle (GTCC) power plants that can handle peak loads are increasing. In GTCC power generation, O&M (Operation and Maintenance) cost is the next most important after fuel and initial investment cost, and it is necessary to predict O&M cost according to changes in the operating environment for efficient and stable operation of GTCC power plant. However, various uncertainties exist when estimating O&M costs because actual design information is limitedly disclosed due to maintenance contracts between operators and manufacturers, and it is difficult to obtain accurate variables according to the operating condition.
In this paper, the correlation was analyzed considering the uncertainty of the factors affecting the O&M cost of the GTCC power plant through sensitivity analysis, and the main factors were defined. In addition, a surrogate model was used that can quickly calculate fixed and variable costs according to changing operating scenarios such as shortening start-up time, enhancing ramp rate, or lower minimum load. Through the case study, short-term and long-term O&M costs can be estimated due to changes in the operating environment of the GTCC power plant currently being operated. In addition, long-term O&M costs for new power generation facilities such as hybrid GTCC (GT+ESS) can be estimated relatively easily and quickly, which can help establish long-term investment plans.
Development of a Modular Engine Performance Calculation Tool for Prediction of Conventional and Hybrid-Electric Aircraft Engines
Authors: Wiegand Marcus , Schuchard Lukas , Krüger Tony , Mailach Ronald 
Published: August 2024

Abstract
Reducing climate-damaging emissions is a key objective of today’s aviation industry. Suitable approaches include emission-optimized flight profiles and the use of hybrid-electric propulsion technologies. In order to quickly identify and quantify their potential, powerful 0D engine models are needed to calculate the performance of conventional thermal and hybrid-electric propulsion systems at the design point and in off-design conditions.
This paper presents the model Maple (“Modular Aircraft Engine Performance for Sustainable Aviation”) for such performance calculation, emission and mass estimation. Special emphasis is laid on a flexible, modular design, so that the framework can be extended by new configurations and additional components, e.g. electric subsystems or heat exchangers. Established turbojet, turbofan, and turboprop configurations as well as various (hybrid-)electric configurations are implemented. Validation against an established commercial reference shows deviations well below one percent. For the analysis along entire flight missions, off-design operating points are computed quasi-steadily depending on atmospheric boundary conditions and thrust requirements. The latter are determined using the open source tool OpenAP. Thereby, the influence of additional mass due to more sophisticated engine configurations is taken into account.
To illustrate the capabilities of the performance tool, it is used to compare and discuss the performance of a conventional turbofan engine and a parallel hybrid-electric engine by calculating two exemplary flight missions with two battery technology assumptions. The benefits and challenges of using hybrid-electric engines are highlighted. These include the need for careful matching of conventional and electric components, gas turbine retrofit, and advanced thermal management.
Overall, the strengths of the developed tool are demonstrated. The modular structure and easy adaptability are ideal for the efficient design and calculation of state-of-the-art and future aircraft engines. The tool allows estimating their impact on flight mission fuel consumption and emissions, and thus on the climate.
Design Strategy of Thrust Gas Bearings for Refrigerant Compressors Considering Effects of Centrifugal Force and Convective Inertia
Authors: Prabhakar Arvind , Kim Daejong 
Published: August 2024

Abstract
This paper studies and compares 3D thermo-hydrodynamic (THD) performance of rigid thrust gas bearings lubricated with R1234ze gas using Reynolds Equation and commercial computational fluid dynamics (CFD) software. The gas bearing consists of six pads operated in both hydrodynamic and hybrid modes at high ambient pressures typical to the bearing compartment of refrigerant compressors. The CFD simulations adopted an advanced turbulence model and Peng-Robinson real gas equation of state while the Reynolds Equation-based THD model adopted NIST Refprop for real gas model. Results from the two models are compared, and detailed observations on gas bearing performance are presented including load capacity, pressure profiles, streamlines, effect of convective inertia and Mach number, etc. Further, the effects of inlet dead volume (IDV) region in such modeling are included to capture complete detailed flow behaviors for the presented high-density refrigerant gas flows within such bearings.
The CFD results demonstrate that convective inertia increases load capacity significantly for refrigerant gases. Both models capture temperature drops around the orifice curtain area from isentropic expansion, but CFD predicts more accurate isentropic expansion not only in temperature drop but also in pressure drop. Furthermore, convective inertia effects are not substantial for air bearings at lower ambient boundary pressures but are still significant for refrigerants at low ambient boundary pressures. Another important feature captured from CFD is the possibility of sub-ambient pressure at certain inner and outer boundaries of the bearing due to high Mach numbers of the leakage flows, and resultant sub-ambient static pressures and lower load capacity when ambient pressure is too low. However, such sub-ambient pressure is not prominent in typical operating conditions of refrigerant gases.
Research on Film Cooling Characteristics and Mechanism of Longitudinal Corrugated Heat Shield in Afterburner
Authors: Fu Song , Liu Hai-yong , Wang Zi-wen , Bai Xiao-hui , Liu Cun-liang 
Published: August 2024

Abstract
Taking into consideration both the cooling performance of the afterburner and its effect on suppressing combustion oscillations, the longitudinally corrugated heat shield has found widespread application in the afterburner. This paper employs computational fluid dynamics (CFD) and experimental methods to elucidate the influence mechanisms of key parameters such as momentum ratio, open area, and non-dimensional amplitude on the film cooling effectiveness characteristics of the corrugated plate thermal insulation structure. The results indicate that with an increase in the momentum ratio, the effectiveness of gas film cooling rises, and downstream stabilization occurs with the accumulation of the gas film. However, when the momentum ratio exceeds a certain threshold and continues to increase, excessive local momentum downstream results in a decline in gas film cooling efficiency. Additionally, as the non-dimensional amplitude increases, there is a decrease in gas film cooling efficiency, exacerbated by the increasing oscillations of corrugation. Furthermore, at a constant unit area cold air flow rate, the efficiency of gas film cooling increases with an increase in porosity.
A Wind Turbine Power Forecasting Method Based on MTGP Transfer Learning
Authors: Hui Huaiyu , Jiang Xiaomo , Chen Huize , Zhang Kexin 
Published: August 2024

Abstract
Wind turbine power forecasting plays an increasingly important role in the safety, reliability, and stability of both the power grid and the electricity market. Owing to the fluctuating and intermittent nature of the wind resource, it is very challenging to accurately forecast the wind power for either a newly constructed or existing farm. Most existing related research has not considered the data uncertainty and insufficiency in wind power forecasting so that the yielded model cannot produce the desirable result in practice. This paper presents a BDWPT-MTGP hybrid approach to accurately forecast the wind power in the scenario of data insufficiency. The Bayesian Discrete Wavelet Packet Transform (BDWPT) denoising approach is employed to improve wind power forecasting accuracy with data imperfection. A multi-task Gaussian process (MTGP) transfer learning model is developed for power forecasting of wind turbines based on limited operating data, thus addressing the data insufficiency issue. A MTGP model is constructed by leveraging available wind farm data alongside limited power data. The proposed BDWPT-MTGP hybrid method is validated by using the operating data acquired from real-world wind turbines. Numerical results demonstrate that the proposed methodology provides a promising tool for accurately forecasting wind power with data uncertainty and insufficiency.
Extension of the MULTALL Open Source Throughflow Code for the Improved Off – Design Calculations
Authors: Bilgiç Mustafa , Baran Özgür Uğraş , Aksel Mehmet Halûk 
Published: August 2024

Abstract
Throughflow calculations play an important role in the design stages of a turbomachinery. After the one-dimensional mean line calculations have been completed, the throughflow solver used in the design mode to perform the blade hub to shroud analysis can also be activated in the analysis mode to perform the off-design analysis. The original MULTALL code applies a uniform friction coefficient (Cf) to all wet surfaces in the turbomachinery passage and uses this Cf to calculate wall friction and hence loss. Although this approach is more physical than the source term approach, it does not capture certain physical phenomena in the turbomachinery passage. In the previous step of this study, the MULTALL code is modified to give a more realistic end wall loss distribution [18]. In this study, the code is further modified to perform off-design analysis and is given the capability to perform off-design analysis. Just as the constant Cf imposed in the design condition gives an unphysical loss distribution along the blade, it also gives inaccurate results for off-design. Since different angles of incidence and mass flows in off-design conditions will result in different loss distributions, the constant Cf must be adjusted according to the changing conditions. Considering a classical compressor or turbine performance curve, the angles of incidence change as the mass flow changes, and the losses increase according to the design condition. In addition, the shock losses also increase at high mass flow rates (“choked region” on the performance map). Therefore, to calculate an accurate loss prediction in off-design conditions, the Cf distribution used in the design condition should be modified due to diffusion effect, incidence and shock losses. In this paper we present parts of the MULTALL solver modified for off-design analysis and validate the results obtained with two compressor test cases. The results show the absolute improvement, especially towards the stall point.
Mass and Heat Exchange in Rotating Compressor Cavities With Variable Cob Separation
Authors: Nicholas Tom E. W. , Pernak Mikolaj J. , Lock Gary D. , Scobie James A. , Tang Hui 
Published: August 2024

Abstract
Next generation aeroengines will operate at ever-increasing pressure ratios with smaller cores, where the control of blade-tip clearances across the flight cycle is an emerging design challenge. Such clearances are affected by the thermal expansion of the compressor discs that hold the blades, where acute thermal stresses govern operating life. The cavities formed by co-rotating discs feature a heated shroud at high radius and cooler cobs at low radius. A three-dimensional, unsteady and unstable flow structure is induced by destabilising buoyancy forces. The radial distribution of disc temperature is driven by a conjugate heat transfer at Grashof numbers of order 1013. Such flows are further influenced by the heat and mass exchange with an axial through-flow of cooling air at low radius, where the interaction depends on the Rossby number and separation of the disc cobs.
This paper is the first to study the effect of cob separation ratio on mass and heat exchange for compressor cavities. A model is developed to predict the cavity-throughflow interaction, and disc and fluid-core temperatures. The judicious use of a physics-based methodology provides reliable, reduced-order solutions to the complex conjugate problem, thereby making it appropriate for practical engine thermo-mechanical design. The model is validated by detailed experimental measurements using the Bath Compressor Cavity Rig, where variable disc cob spacings were investigated over a range of engine-representative conditions. The unsteady pressure measurements collected in the frame of reference of the rotating discs reveal new insight into the fundamentally aperiodic nature of the flow structure. This new understanding of heat transfer informs an expedient reduced-order model and enables more efficient design of future high pressure-ratio aeroengines.