bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advanced Design of a Transition Duct for Supersonic Inlet Turbines in Rotating Detonation Engines
Authors: Mushtaq Noraiz , Pini Matteo , Gaetani Paolo 
Published: August 2024

Abstract
A supersonic inlet turbine can extract substantial energy from the highly fluctuating and transonic flow delivered by a rotating detonation combustor (RDC). However, a transition duct is necessary to achieve the supersonic inlet conditions required by the turbine. In this work, the supersonic transition duct is designed with the method of characteristics (MOC). A generalized implementation of the MOC is proposed for the generation of annular ducts with asymmetric and rotated hub and shroud walls. The model is extended to deal with ideal and non-ideal flows, namely flows characterized by non-ideal thermodynamic effects, and its accuracy has been verified through comparison with results obtained with computational fluid dynamic (CFD) simulations. In addition, boundary layer flow equations are combined with the MOC to predict viscous losses on the endwalls and to adjust duct geometry by accounting for the boundary layer thickness. Furthermore, it is essential to predict the effects of the large unsteadiness generated by the detonation combustor for an efficient operation of the turbine. The maximum incidence angle at the turbine inlet is predicted with a one-dimensional annular duct model. Supersonic duct flow behavior to unsteady inlet conditions is characterized through two-dimensional inviscid axisymmetric unsteady CFD simulations. The accuracy of the reduced order models is finally verified with a three-dimensional unsteady viscous simulation assuming inlet flow conditions representative of RDC operation.
Numerical Simulation and Prediction Using Neural Network for Internal Flow Field and Outlet Distortion Contour of S-Shape Inlet Ducts
Authors: Wang ShiXuan , Zhang Min , Du Juan , Ba Dun , Nie ChaoQun , Wang YangYang 
Published: August 2024

Abstract
S-shape inlet (or S-intake) has been widely employed to satisfy the demand of stealth and compactness for modern aircraft. However, the large curvature of the S-intakes triggers boundary layer separation, generating severe flow separation that further lead to total pressure and swirl distortion at the S-intake outlet. The flow distortion can significantly deteriorate the efficiency of downstream compressor. Therefore, studying the internal flow dynamics within the S-intake and the distortion at the S-intake’s exit is an important work. Due to this, this paper investigated a S-intake in the open literature. First, the S-intake is parameterized. Then, a design of experiment study based on numerical simulations is conducted. The influences of key geometric parameters on the performance of the intake are analyzed. Using those numerical simulation data, back propagation (BP) neural networks are trained. They are intended to realize a quick evaluation of the total pressure recovery coefficient and total pressure distortion index (DC120) of the outlet for the S-intakes with varying geometric parameters under difference flight Mach number conditions. Also, other neural networks are established for predicting total pressure and velocity fields on the S-intake outlet section. Results demonstrate that the BP neural network has an impressive accuracy in predicting the total-pressure recovery coefficient, with a mean square error of approximately 0.049%. However, the predictive capability for the DC120 model is relatively modest, with a mean square error of approximately 7%. In addition, the average predicting error in flow field on the S-intake outlet is about 3.9 % when compacted to numerical simulation results.
Impact of Manufacturing Variability From Different Compressor Stages on Aerodynamic Uncertainty: An Interchangeability Study
Authors: Li Mingzhi , Yu Xianjun , Meng Dejun , An Guangfeng , Liu Baojie 
Published: August 2024

Abstract
Aerodynamic uncertainties in compressors introduced by manufacturing variability have garnered increasing attention in recent years. Accurately assessing the impact of manufacturing variations on newly designed blades is essential for facilitating robust design. However, the assessment of performance uncertainty of designed blades is significantly influenced by the method employed to introduce geometric uncertainty. This paper investigates the appropriate approach for superimposing manufacturing variations onto new blade profiles to obtain accurate insights into aerodynamic uncertainties. The first part of the paper thoroughly analyzes manufacturing variations in over 1400 newly manufactured rotor blades from different compressor stages, which were measured using a coordinate measurement machine. The statistical characteristics of geometric variations in distinct directions are captured. In the second part, by calculating the aerodynamic performance of numerous compressor blade profiles with manufacturing variability, we investigate the interchangeability of manufacturing variations from different compressor stages for accurately assessing the aerodynamic uncertainties of new designs. The results demonstrate that manufacturing variations among different stages exhibit some similar geometric characteristics and are easily interchangeable when evaluating mean performance. When assessing the standard deviation of aerodynamic performance, the statistical results corresponding to the manufacturing variations from different stages exhibit a consistent trend, with some discrepancies emerging under different operating conditions.
CFD Study for Mitigation of H2 Explosion Inside Gas Turbine Enclosure
Authors: De Leo Elena , Quartieri Eugenio , Minotti Stefano , Rossin Stefano 
Published: August 2024

Abstract
There are several potential sources of risk in the design of a gas turbine burning 100% hydrogen.
Risks arise from the criticality of hydrogen characteristics: low ignition energy, wide flammability range, high burning velocity. During the design process, it is required to focus on safety aspects. All credible hazard scenarios in terms of occurrence probability shall be considered to avoid undesired catastrophic consequences. Looking to auxiliary systems, the main source of hazard can be considered the fuel gas supply system that is installed close to the gas turbine inside an enclosed space.
Although fuel gas line is properly designed to avoid the possibility of hydrogen leaks inside the enclosure, the occurrence probability of a sudden leakage of tubing rupture is not impossible.
The potential consequence of such remote event, combined with the higher flammability range of hydrogen, could lead to an undesired delayed ignition. Depending on several factors such as dispersed flammable mass and presence of obstacles in confined volume, an explosion could follow the ignition.
In order to assess the impact of this scenario, a numerical simulation campaign for a LT16 100% H2 gas turbine enclosure was carried out with commercial code FLACS, which is a tool able to simulate a complex phenomenon like an explosion. Different gas dispersion and delayed ignition cases were analyzed to predict the consequences in terms of overpressure inside the enclosure without carrying out complex experimental tests. The present work also investigated the use of relief panels as a mitigation method to reduce the overpressure inside the enclosure. The position, shape and venting area of the panels were evaluated in terms of their effectiveness.
CFD Speedline Simulations of High-Work Radial Compressor Stages
Authors: Hansen Thorsten , Munktell Erik , Scheuerer Georg , Zhuang Qingyuan , Zwiener Kim 
Published: August 2024

Abstract
Consistent simulations of compressor speedlines from choke to surge are challenging for CFD codes. Changing the outlet boundary condition along the speedline is often necessary to obtain physically plausible and numerically robust results. The root of the problem is the compressor characteristic: Close to choke, a mass flow rate as outlet boundary condition can produce ambiguous values and close to surge, a pressure boundary condition can yield multi-valued results. The paper discusses an outlet boundary condition based on a reduced outlet mass flow rate to overcome this problem. The boundary condition behaves like a pressure boundary condition close to choking and like a boundary condition for the mass flow rate close to surge, allowing for consistent simulations of whole speedlines. The paper explains the mechanics and advantages of this boundary condition in detail.
The authors applied outlet boundary conditions for static pressure, mass flow rate, and reduced mass flow rate to the High-Efficiency Centrifugal Compressor (HECC) experimentally investigated at the NASA Glenn Research Centre. The HECC has an impeller with 15 blade-splitter pairs, a diffusor with 20 blade-splitter pairs and 60 exit guide vanes. It is representative of the final stage of a compressor for rotorcraft applications. The HECC is a challenging test case for every CFD method because of its small diameter, the total pressure ratio of 4.7, the high work factor of 0.81, and the complex shock structures in the flow close to the choke condition.
In the paper’s results section, the authors discuss the pros and cons of static pressure, mass flow rate and reduced mass flow rate as boundary conditions regarding numerical accuracy and robustness. The simulations are conducted on a sequence of three homogeneously refined meshes with an effective refinement factor of 1.6 between the meshes. For three-dimensional problems, an effective refinement factor of 1.6 increases the number of cells by four. The solutions on the three meshes serve to quantify the numerical accuracy using Richardson extrapolation.
The mathematical model for the simulations consists of the steady-state averaged conservation equations for mass, momentum, and total enthalpy, complemented by two-equation eddy-viscosity turbulence models, namely the SST and BSL two-equation eddy-viscosity models and an eddy-diffusivity model for the turbulent heat fluxes. The rotor-stator interaction is modelled with a steady-state mixing plane algorithm using single-blade passages.
The Effect of Additive ‘Depositional’ Reprofiling of Compressor Blade Leading Edges on Engine Performance
Authors: Mullaney Drew , Jones Merren , Bojdo Nicholas , Covey-Crump Stephen , Pawley Alison 
Published: August 2024

Abstract
A common problem for gas turbine engines after ingesting atmospheric dust is compressor fouling, where small particles adhere to component surfaces. By sampling components from both a test engine and a service engine, deposits that are hard and sintered were observed to have formed on the leading edges of compressor blades and stators reprofiling their leading-edge geometry. Sectioning of the components showed that the deposits consist of layers of different chemical compositions and that new minerals have crystallized within the deposits. The change in geometry caused by the deposits suggests that they negatively affect the operating incidence range, surface pressure distribution and profile losses from the design intent of the original component, changing the compressor working line and reducing surge margin, efficiency and pressure ratio.
Study on an Automatic FMECA Analysis for Gas Turbine Systems Using Model-Based Systems Engineering Method
Authors: Chen Jinwei , Hu Zhenchao , Zhang Huisheng 
Published: August 2024

Abstract
Gas turbine systems operate in high temperature and high pressure conditions, which easily lead to performance degradation or various serious failures. The reliability is one of the most important attributes to monitor the gas turbine safety. Failure Mode, Effects, and Criticality Analysis (FMECA) is a well-known approach to systematically analyze the gas turbine reliability. However, traditional document-centric implementation of FMECA requires manual recording of fault related information. Such implementation approach is prone to human error and tedious. As an evolving approach, Model-based Systems Engineering (MBSE) has been applied in many industries to support system design, analysis and management. In this study, an automatic FMECA analysis approach for gas turbine systems is proposed based on MBSE. The FMECA architecture model is established according to the SysML diagrams of internal block diagram and block definition diagram. The topology between FMECA related concepts is characterized through the constructed architecture model. Then, the Design Structure Matrices is used to realize the risk analysis automatically. A case study of a real gas turbine is conducted to demonstrate the effectiveness of the proposed approach. The case results suggest that proposed approach can significantly enhance the efficiency of FMECA analysis.
A Digital Engineering Analysis of an Additively Manufactured Turbine Vane
Authors: Berdanier Reid A. , Tien Leland , Thole Karen A. 
Published: August 2024

Abstract
Additive manufacturing (AM) has transformed the ability to accelerate gas turbine component research and development at a fraction of the cost and time associated with conventional manufacturing. However, whereas prior works have assessed manufacturing variability in cast turbine airfoils, limited data are available to understand the impact of as-built deviations in AM turbine parts. As metal additive airfoils are becoming more prevalent in research turbine architectures, it is increasingly important to understand the effects of potential hardware deviations specific to additively manufactured parts. With this goal in mind, the current study utilizes a digital engineering approach to evaluate the aerodynamic impact of surface deviations on a high-pressure turbine vane design created for research purposes. RANS-based CFD studies derived from structured light scans of as-built turbine vanes are used to quantify performance relative to design intent geometries. Further computational analyses compare results from individual serialized parts with an average vane doublet geometry serving as a surrogate for the entire wheel. Particular emphasis in the study focuses on external surface defects caused by internal cooling features that are inherent through additive manufacturing and how these features can impact the vane performance. Ultimately, this study identifies specific regions of the vane that are subject to increased sensitivity, which benefits future designers intending to use AM as a tool for turbine research and development.
Complete Dynamics From Ignition to Stabilization of a Lean Hydrogen Flame With Thickened Flame Model
Authors: Amerighi Matteo , Senatori Giada , Yahou Tarik , Schuller Thierry , Dawson James R. , Andreini Antonio 
Published: August 2024

Abstract
In recent years, attention has been paid to hydrogen thanks to its carbon-free nature and its interesting characteristics as an energy vector. Despite the large number of numerical analyses regarding hydrocarbon combustion in all the steady and unsteady processes, few papers that cover all those aspects are available in the literature for hydrogen flames. Therefore, a numerical methodology to explore the complete ignition sequence from the spark release to the flame stabilization is validated on a single-sector hydrogen burner. In this context, a preliminary DNS investigation of laminar spherical expanding flames is performed using different diffusive transport models to isolate their impact.
The present work, carried out within the European project HESTIA, investigates the atmospheric test rig installed at the Norwegian University of Science and Technology operating with a lean, perfectly premixed, hydrogen-air flame stabilized on a conical bluffbody. Four simulations are performed adopting the Thickened Flame Model with an energy deposition strategy to assess the impact of preferential and thermal diffusion, as well as grid resolution, on flame dynamics.
3D flame structure visualization coupled with detailed PIV/OH-PLIF measurements allows the investigation of the key mechanisms involved during the ignition. The dynamic response of the flame through axial fluctuations once the ignition transient is concluded, is reconstructed by the numerical strategy employed. Although the overall behavior is almost unchanged by including or not thermal diffusion effects, their local impact on the flame is evident leading to a better agreement with experimental data.
A Bladed Disk Reduction Technique That Captures Variation in Blade Stiffness and Blade Root Joint Contacts
Authors: Krizak Troy , Firrone Christian Maria , Battiato Giuseppe , D’Souza Kiran 
Published: August 2024

Abstract
In practice, a bladed disk will always have variations, known as mistuning, which is a focus of a significant amount of research within the turbomachinery industry. When mistuning is present, the forced response of the system often shows localized amplification of the blade deflection amplitudes when compared to a tuned system. In order to quickly perform a significant number of simulations containing mistuning, reduced order models (ROMs) have been developed where the mistuning can be introduced efficiently in the reduced space. Previously, mistuning had been introduced to bladed disks in the form of natural frequency shifts in the blades, and separately from contact uncertainties in the blade root joint and also separately from the various forms of small and large geometric mistuning. This work introduces a method to efficiently model multiple types of mistuning sources so that any interactions that may result can be studied. This work focuses on cases with stiffness and contact mistuning which are due to design tolerances, manufacturing processes, assembly procedures, material variability, and wear. The technique in this work utilizes the Craig-Bampton component mode synthesis that is applied to the uncoupled blade and disk sector. Small stiffness mistuning is applied by directly adjusting the modulus of elasticity within the uncoupled blade portion of the ROM. The degrees of freedom at the contacts are reduced using a modal basis based on the Gram-Schmidt Interface technique. A numerical validation of the developed methods is performed for cases including small and large stiffness mistuning and contact mistuning using a finite element model of a simplified rotor.
Heat Transfer Coefficients in a Three-Passage Ribbed Channel Using a Transient Liquid Crystal Technique
Authors: Wright Lesley M. , Shiau Chao-Cheng , Han Je-Chin , Krewinkel Robert 
Published: August 2024

Abstract
One-dimensional (1D) transient heat conduction in a semi-infinite solid material with a convection boundary condition has been widely used for determining the surface convection heat transfer coefficient distributions. In this work, the full heat transfer characteristic maps of a turbine blade with a realistic, three-passage, ribbed channel are examined using the 1D transient heat conduction model with narrow-band liquid crystals. The tests were conducted at two different engine representative flow conditions. The time map for the blade’s internal surfaces to reach a target temperature was obtained from the liquid crystal using the maximum green intensity approach. The conventional hue value approach was also applied to obtain the surface time map for data comparison. Since the test channel is of high blockage, delayed flow history was observed and a time correction was needed to address the asynchronous behavior between the flow and heat transfer. In addition, the difficulty of accurately capturing the bulk mean flow temperature within the three-passage channel leads to additional uncertainty for heat transfer coefficient calculations. The effects of delayed flow, time correction, and using different reference fluid temperatures on the Nusselt number calculations are demonstrated and analyzed. Using the current blade as an example, this study compares two different temperature interpretation approaches (maximum green intensity and hue value). In addition, other factors that affect the measurement of detailed heat transfer coefficient distributions using 1D transient conduction model are presented and discussed.
Emissions and Flame Stability Assessment of Hydrogen Addition and Air Dilution in a Micro Gas Turbine Combustor Using 0D/1D Modeling by Chemical Reactor Network
Authors: Yousefzad Farrokhi Farshid , Piscopo Alessandro , Pappa Alessio , Parente Alessandro , De Paepe Ward 
Published: August 2024

Abstract
Hydrogen emerges as a promising fuel for clean and sustainable electricity production when utilized in micro gas turbines (mGTs). However, some challenges linked to hydrogen usage must be overcome as its high reactivity can lead to increased NOx emissions and flame instabilities. Literature suggests that combustion air humidification and/or exhaust gas recirculation (EGR) may be methods to reduce this reactivity. However, these measures are limited due to the small operating range of the mGT combustor.
In this context, a 20 kWth mGT combustor is investigated under various inlet conditions to assess the effect of EGR towards increased flame stability and emission control when operating under hydrogen-enriched methane firing, using a Chemical Reaction Network (CRN) model. The CRN modeling is a fast and low computational complexity tool to model combustion performance and emissions by representing complex reactive flow fields through idealized reactor models, leading to reduced computational costs. This study examines partial load conditions, fuel compositions, and the effect of combustion air dilution through EGR. The CRN model of the combustion process is designed based on combustion zones extracted from the main flow fields with similar thermo-chemical states from CFD, while emission predictions are experimentally validated for different operating points. Predicted NOx and CO emissions by the proposed CRN model show an acceptable agreement with the experimental data at high power loads. However, its accuracy diminishes for loads below 70% due to the variability in model tuning parameters across different loads, whereas the current model is optimized for 90% load conditions. At full load with the activation of EGR, these emissions are reduced by approximately 20%. CRN results predict that NOx emissions do not increase excessively by hydrogen addition due to the constant power operation of the mGT. Indeed, the higher reactivity of hydrogen leads to a lower fuel flow rate and, thus, leaner operating conditions. On the other hand, CO emissions decrease by 15 to 40% when adding hydrogen from 5 to 50% of the volume fraction to natural gas. Finally, air dilution by EGR positively affects flame temperature and NOx emissions. Tuning CRN models that are not dependent on specific load parameters to get a better agreement with experimental data, as well as EGR/humidified air dilution effects on partial loads and hydrogen added fuels, are subjects to future work.