bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Parameter Augmentation Pretraining Neural Network Model of Aero-Engine Thrust Prediction
Authors: You Rui , Xiao Hong , Chen Guo , Liang Yufeng 
Published: August 2024

Abstract
Accurately predicting the thrust of aero-engine is important for engine health management and engine performance control. Thrust prediction neural network models have been widely applied in recent years. This paper proposes a parameter augmentation pretraining method and designs an aero-engine neural network model with physical significance. It is known that ground test system measures more engine parameters compared to onboard system. Due to the limitations of using onboard models, typically only the parameters measured by both systems are used as training parameters, which may lead to incomplete training. In this study, a 0-1 encoded vector is utilized to distinguish ground test system data and onboard system data. The model is first pretrained using the measurable parameters from the ground test system, following by retraining using parameters measured by both the ground test system and the onboard system. The parameter augmentation pretrain method allows the model to learn more mapping relationships of aero-engine and resolves the issue of parameter dimension matching. Furthermore, this study investigates the impact of the weight loss function on the prediction accuracy of the model. This research provides guidance for engine performance evaluation and further studies.
Evaluation of a Commercial 65 kW Recuperated Gas Turbine Engine Operated on Up to 30% Hydrogen Added to Natural Gas
Authors: Villatoro Walther , Navarro Aris , McDonell Vincent , Hu Ray 
Published: August 2024

Abstract
A commercial natural gas 65 kW microturbine generator produced by Capstone Green Energy Corporation is used to study the impact of hydrogen addition to natural gas. Hydrogen addition in natural gas turbines can reduce carbon dioxide and carbon monoxide emission as a step towards carbon neutrality. Exhaust emissions and power output are evaluated for increasing levels of hydrogen in the fuel mixture. Additionally, a chemical reactor network (CRN) is used in conjunction with injector mixing characterization to support the development. The CRN analysis predicts NOx using perfectly stirred reactors (PSR) therefore, a strategy to account for the measured fuel concentration at the injector exit was implemented to estimate NOx emissions for the actual fuel/air mixing. At full load, experimental NOx emissions remain almost unchanged as the %vol of hydrogen increases from 0 to 30%. CO and CO2 decrease with increasing vol% of hydrogen in the fuel as expected. The CRN captures the general emissions trends with hydrogen addition and illustrates sensitivity to the mechanism utilized. Visual inspection of the injectors following hydrogen addition tests indicated that flashback or combustion inside the injectors did not occur. Measured engine system efficiency was not impacted by the addition of hydrogen. Mixing performance tests for the injectors showed that the fuel and air were well mixed prior to combustion, consistent with the single digit NOx ppm levels measured. The study indicates that addition of hydrogen, up to 30% by volume, is possible without any modification to this gas turbine engine.
Benchmarking Gas Turbine Outages: Creating an Expectation Model of Performance Recovery
Authors: Perullo Christopher , Gerlings Andrew , Tomlinson Rick , Koskey Steven , Noble David 
Published: August 2024

Abstract
Gas turbines are the lynchpin of a stable and prospering U.S. power grid and economy. As more forward growth emphasizes renewables, maintaining the existing gas turbine fleet will become even more critical. Gas turbines undergo regular maintenance cycles that inspect, repair, and replace life limited parts. The complexity and invasiveness of maintenance often leads to variability in the resulting performance recovery. For example, parts may not be installed correctly or controls may not be adjusted after the outage as needed. While engineers have a personal ‘expectation model’, this often is incorrect and few organizations rigorously benchmark outage recovery to identify lost performance and incorrect repairs. This paper applies the EPRI Gas Turbine Digital Twin to a historical set of outages for B class gas turbines. A methodology is presented to track outage recovery by comparing model performance to site data pre and post outage and accounting for model and measurement uncertainty through the use of machine learning. This provides a probabilistic estimate of outage recovery which is used to create a fleet outage recovery expectation model. The intent is to use this model to benchmark and score future outages’ effectiveness. The resulting expectation model is also presented here for others to use in their own benchmarking efforts.
Transient Analysis of Flow Unsteadiness and Machine Instabilities in a Centrifugal Compressor at Surge and Second Quadrant Operation
Authors: Serena Alberto , Bakken Lars Eirik 
Published: August 2024

Abstract
Instabilities in turbomachinery operation originate from intrinsic flow unsteadiness, sudden variations of operating conditions, and interactions with the surrounding system, affecting both system stability and machine reliability. The flow unsteadiness, presenting a characteristic behaviour, requires a deep understanding of the underlying flow fundamentals, a careful analysis using advanced experimental methods and a clear distinction on how the system might lead to instabilities.
The identified approach addresses deep surge and second quadrant characterization. A non adequate test procedure might strongly affect the overall behaviour and transient evolution. The analysis presented here benefits from the responsiveness and flexibility of the experimental test rig, fine tuning of the system layout, the instrumentation installation, and the transient tests procedure. The main focus area is the time-frequency analysis of flow and pressure signals at transients, thus providing a proper reconstruction of flow mechanisms and instability evolution. Valuable techniques include: short-time fast Fourier transform, wavelet analysis, and Wigner-Ville distribution; coherence between flow and pressure, to trace waves propagation, is considered too. These, presented outlining their strengths and weaknesses, are evaluated considering real time field applicability with regards to computational resources too.
The experimental campaigns and data processing are presented, with a test matrix covering a wide range of parameters, including system layout and surge volume size, rotational speeds, flow rates ranging from nominal point to full second quadrant operation. These data are vital for system modeling validation for a full compressor-system digital twin.
Results indicate the importance of ensuring reliable data acquisition and analysis, with adequate instrumentation range, accuracy, synchronization, responsiveness and positioning.
Investigation of the Effects of Geometry Variations on the Performance of an Adjoint Optimized Film Cooling Hole
Authors: Ellinger Molly E. , Flachs Elise M. , Bogard David G. 
Published: August 2024

Abstract
In recent studies, a turbine film cooling shaped hole designed by adjoint optimization techniques (X-AOpt) was found to substantially increase film cooling performance with 90% greater adiabatic effectiveness than a reference 7-7-7 shaped hole. Two aspects of the geometry contribute to the high adiabatic effectiveness levels achieved by the X-AOpt holes: the shape of the internal geometry which improves the diffuser performance, and the external protrusions that generate counter-rotating vortices that push the core of the coolant jets towards the wall and spread the coolant laterally. In this study, insight into the relative importance of these two factors was obtained by testing the performance of a row of X-AOpt holes with the protrusions removed from the external surface. Experiments were also performed with varying pitch between X-AOpt holes to determine how the hole spacing affects film cooling effectiveness. Results from the tests of X-AOpt holes without external protrusions showed a 9% increase in adiabatic effectiveness compared to the baseline 15-15-1 holes, while the X-AOpt holes had a 45% higher adiabatic effectiveness than this standard. Experiments were also conducted using X-AOpt holes with varying pitch between holes of P/D = 4.0, 5.45, and 7.0. Results from these experiments showed that a decrease in pitch to P/D = 4.0 provided only a slightly increased adiabatic effectiveness compared to standard P/D = 5.45. However, increasing the pitch to P/D = 7.0 caused a 33% decrease in adiabatic effectiveness compared to the standard spacing. Superposition was found to significantly under predict adiabatic effectiveness for P/D = 4.0 and 7.0, indicating there is a dependence on lateral spacing for the X-AOpt geometry due to vortex interaction.
Validation of a Numerical Model Based on an Optical Surface Scan and Experimental Modal Analyses Under Vacuum Conditions
Authors: Langheinrich Denny , Beirow Bernd , Elmasry Seif 
Published: August 2024

Abstract
A safe operation of compressors requires a profound understanding of the vibrational behaviour of their components. The focus of this work is on the identification of the modal quantities of an impeller of a radial compressor. The prediction of the mistuned mode shapes and eigenfrequencies is carried out by a finite element model which is adapted to surface scan data via mesh morphing to capture geometrical deviations from CAD. A validation of this model is given by an experimental modal analysis, which is conducted under vacuum conditions to eliminate the damping and coupling influence of the surrounding medium. In consequence, the better separation of peaks in the frequency response function (FRF) enables the identification of all modes. The modal parameters as eigenfrequencies, damping ratios and modal constants are extracted from the measurement data by an improved multi-degree-of-freedom-fit algorithm which is capable to process the entire frequency band of a measured FRF. This is necessary due to a high density of modes preventing the separate assessment of certain frequency ranges without errors at the edges of the frequency band. In addition, a laser scan is carried out to support the assignment of measurement data to results from the numerical model based on vibration modes. It can be shown that a majority of the roughly 600 modes in the range of interest can be assigned to measurement data in terms of eigenfrequencies, modified cyclic symmetry mode shapes and blade mode shapes.
Multi-Aeroelastic Phenomena Modelling Part II: Application for the Evaluation of Fan OGV Cyclic Pattern Designs
Authors: Kulkarni Davendu Y. , di Mare Luca 
Published: August 2024

Abstract
The cyclic pattern design of fan outlet guide vanes (OGVs) is key to achieving the fan stage performance and to set the aeromechanical behaviour of low-pressure compressor (LPC). Current trend of compact engine architectures leads to the stronger interaction between LPC components, which in turn results in larger modifications in OGV pattern geometry. A thorough verification of OGV patterns is necessary to avoid the risks associated to LPC performance.
This paper describes the application of high-fidelity aeroelastic model for evaluating OGV cyclic patterns that are commonly designed using low-fidelity design-optimisation methods. The whole fan system model, described in the first part of this paper, is used to conduct time-accurate unsteady CFD simulations to perform various low-harmonic aeroelastic phenomena investigations simultaneously. The simulation results are post-processed to extract 1EO fan forced response, a measure of OGV buffet and the fan efficiency at multiple flight conditions. Multiple OGV patterns are assessed using this approach to explore the OGV pattern design space.
Further, these simulation results are used to produce a Pareto front, which effectively demonstrates the OGV pattern design robustness. This methodology allows comparing various OGV pattern designs against a common set of criteria, to perform design trade-off studies and to identify a right-first-time OGV cyclic pattern design within design timescales.
In-Situ Species Concentration Measurements in Ammonia-Mix Flames Using FTIR Spectroscopy
Authors: Bedick Clinton , Tulgestke Andrew , Boyette Wesley 
Published: August 2024

Abstract
Hydrogen and ammonia represent two carbon-free fuel sources that could be used in place of current fossil energy sources in combustion systems. To develop optimized ammonia combustion systems, validated modeling tools are needed. In the open literature, it has been shown that the complex chemistry associated with fuel-bound nitrogen contained in ammonia differs greatly from natural gas or hydrogen combustion. As a result, several new chemical kinetic mechanisms have been developed. Many of these mechanisms have been validated experimentally, however this has primarily focused on bulk parameters such as laminar flame speed and ignition delay time. Critically, high quality measurements of species concentrations are needed under controlled conditions which are easily represented by simple models. In this paper, direct, in-situ measurements of species concentrations and gas temperature are performed in a laminar flat-flame burner. This arrangement enables comparison with 1D model predictions, better isolating chemical kinetics from the fluid dynamics. Quantitative species concentrations are determined by absorption spectroscopy using an FTIR spectrometer. Fuel compositions representative of cracked ammonia (NH3/H2) and ammonia-natural gas (NH3/CH4) are considered for rich and lean equivalence ratios. A major focus of the paper is on the selection of spectral features for nitric oxide and ammonia and correcting for large amounts of baseline H2O absorption.
Experimental Study of High-Diodicity Inlet Effects on Rotating Detonation Combustor Performance and Operability
Authors: Barnouin Provence , Bach Eric , Paschereit Christian Oliver , Bohon Myles D. 
Published: August 2024

Abstract
Implementing high-diodicity inlets is critical to reduce back-flow and mitigate the pressure loss across the injector in RDCs. Experiments on air injection diodicity were conducted in a non-premixed RDC for both cold-flow and reacting conditions. The introduction of a Tesla-like diode impacted operating modes and injector dynamics, but the extent of that effect depended on the throat-to-combustor area ratio. A smaller ratio mitigated the impact of the diode on detonation characteristics, while a larger ratio extended the operating range of stronger wave modes. The diode stabilized RDC operation through an increased static pressure drop, but limited performance most likely due to poor reactant mixing and local equivalence ratio distribution. Cold-flow tests showed a higher diodicity for the diode, which may contribute to higher pressure gain in reacting experiments. A modified diodicity formulation based on reacting flow measurements was introduced, suggesting that a multi-metric approach can be useful to assess injector performance. High-diodicity air inlets could be useful tools for reducing total pressure loss and controlling operating modes, but careful consideration is required to limit adverse effects on processes like reactant mixing.
Multi-Aeroelastic Phenomena Modelling Part I: the Development of Whole LPC Model for Civil Turbofan Engine
Authors: Kulkarni Davendu Y. , Lad Bharat , di Mare Luca 
Published: August 2024

Abstract
Aeroelastic phenomena in the low-pressure compression (LPC) system of civil turbofan engines can cause a significant high-cycle fatigue (HCF) risk to the LPC components. Currently, the mechanical integrity risk to the LPC components is assessed by performing multiple, discrete aeromechanical simulations, which require large resources and incur high time-cost. Therefore, the development of a comprehensive modellingsimulation approach is necessary to assess multiple phenomena and components simultaneously that can provide accurate results within design timescales.
This paper presents the methodology for generating a common, system-level model for investigating multiple aeroelastic phenomena in fan and outlet guide vanes (OGVs). The development of a high fidelity, full-annulus CFD model of the whole low-pressure compression system is described. Time accurate unsteady CFD simulations are then conducted at multiple flight conditions. These information-rich simulations are interrogated to extract various parameters of interest to assess multiple aeroelastic phenomena.
The aeroelastic parameters are used to investigate 1EO fan forced response, fan alternating passage divergence (APD) response, OGV buffet, and OGV resonant forced response etc. In the second part of this paper, the application of this modelling methodology is demonstrated to evaluate and to better understand the efficacy of OGV asymmetric cyclic patterns.
The Unsteady Shock-Boundary Layer Interaction in a Compressor Cascade – Part 3: Mechanisms of Shock Oscillation
Authors: Munoz Lopez Edwin Joseph , Hergt Alexander , Klinner Joachim , Klose Bjoern F. , Willert Chris , Gümmer Volker 
Published: August 2024

Abstract
The shock-boundary layer interaction in transonic flows is known to cause strong unsteady flow effects that negatively affect the performance and operability of blade and cascade designs. Despite decades of research on the subject, little is still known about the physical mechanisms that drive the different oscillation frequencies observed with different designs. In the conclusion of this three-part series, the experimental and numerical data obtained with the Transonic Cascade TEAMAero are analyzed together in detail in order to test the main theories of continuous shock oscillation. This analysis exposes a main mechanism of shock oscillation, where pressure waves generated inside the passage of the cascade propagate upstream and interact strongly with the main shock when the latter is also in the passage. The interaction of these features causes a breakdown of the flow that is shown to propagate upstream, inevitably causing strong variations in the inflow angle and therefore on the operating conditions of the cascade. The high frequency content of these pressure waves is also shown to be responsible for weaker high-frequency variations of the shock movement throughout the cycle. Parallels are also drawn with previous experimental campaigns in order to search for a global understanding of the different observations made. Although various parts of the described interaction are not fully understood yet, and the dataset of experimental measurements compiled is still rather small, a good basis is provided on which to further study the underlying mechanisms of unsteady flows in transonic cascades.
Experimental Characterization of Darcy Friction Factors of Bump Channel Flows and Application to Cooling Flow Path Design
Authors: Kim Daejong 
Published: August 2024

Abstract
Foil bearings are considered the most promising oil-free bearing technology for small high-speed turbomachines. Among many different underlying supporting structures, corrugated bump foils are the most popular. Due to the geometry of corrugation, the bump foils have gas flow passages through the bump channels, and cooling gas is introduced through these bump channels. The flow resistance through these bump channels is a function of bump geometry, ambient conditions, and type of gases. When multiple foil bearings are installed within a system, cooling gas flow passage design through the bearings requires proper understanding of bump channel flow resistances. Inadequate cavity pressures arising from the cooling gas flow passage design can create undesirable axial force to the thrust bearings. This paper presents experimentally measured Darcy friction factors of typical bump channels in both laminar and turbulent flow conditions, as a function of flow Reynolds number and hydraulic diameter determined from the bump channel geometry. This paper also presents experimentally measured flow characteristics of radial and thrust foil bearings, and measured results are compared with the prediction using the experimentally extracted Darcy friction factors.
Design of a Scroll-Centrifugal Compressor for Supercritical Carbon Dioxide Power Cycles
Authors: Yang Zimu , Lu Zhenbo , Jiang Hongsheng , Zhuge Weilin , Song Panpan , Qian Yuping , Zhang Yangjun 
Published: August 2024

Abstract
Supercritical carbon dioxide (S-CO2) Brayton cycle is a promising power cycle in the field of energy conversion applications. When the cycle is applied for waste heat recovery of gas turbine power system, the operating state will change more drastically compared to other power generation applications, and it is more likely to operate near the critical point, where the thermophysical properties of CO2 vary largely.
To meet the requirements of S-CO2 Brayton power cycle for gas turbine power system, a new type of S-CO2 compressor, named scroll-centrifugal compressor, was proposed in this paper. This new compressor consists of two stages. The low pressure stage is scroll compression and the high pressure stage is centrifugal compression. It can operate at two modes, scroll compression mode and scroll-centrifugal compression mode, to adapt the drastic operating state change of the cycle.
In this paper, the preliminary design considerations of this new compressor were introduced. The design progress of the scroll stage and centrifugal stage was illustrated, respectively. The computational fluid dynamics (CFD) simulation was carried out to analysis the aerodynamic performance of this new compressor. The simulation results shows that this new type compressor can achieve the pressure ratio 1.97 as the inlet state near the critical point.