bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement of Silicon Nitride Turbine Blade Impact Resistance Under Uniaxial Compression Loading
Authors: Beauchamp F. , Dubois P. K. , Plante J.-S. , Picard M. 
Published: October 2022

Abstract
The inside-out ceramic turbine (ICT), a novel microturbine rotor architecture, uses monolithic ceramic turbine blades held in compression by a rotating structural shroud instead of traditional superalloy turbine blades in order to increase its maximum turbine inlet temperature (TIT) and cycle efficiency. Previous work has shown that this microturbine architecture has potential to be viable for long-term operation in normal operating conditions. However, foreign object damage (FOD) has been a major concern for ceramic turbine rotor past development efforts, and its effects on the ICT ceramic turbine blades lifespan have not been studied thus far.
An experimental approach was used to characterize the effect of the ICT configuration on ceramic turbine blade impact resistance: spherical steel impactors were fired towards silicon nitride specimens simulating blade boundary conditions for both traditional and inside-out turbine layouts. Preload levels ranging from 100 MPa to 400 MPa were applied on the inside-out layout specimens to determine its effect on impact resistance.
Results indicate that the inside-out turbine configuration increases the resistance to FOD over a traditional turbine configuration. For the specific conditions of this study, the specimens resisted to over five times the impactor energy when fixed at both ends. Also, results show that applying a higher compression preload on the specimens helps to resist higher energy impacts by about 50% when far from the buckling limit.
A Study of Onshore Wind Turbine Property Damage
Authors: Jou Bin 
Published: October 2022

Abstract
As new capacity enters the wind energy market, property damage and forced outage losses of wind turbines are becoming more frequent. Risk assessment and property loss prevention for wind turbines are common goals for owners, operators, manufacturers, and insurers. In this work, wind turbine failures or damage from industry experience and literatures are reviewed and analyzed along with turbine property loss events at FM Global clients’ insured wind farms, with a focus on understanding the external and internal factors that drive the turbine damage through various failure modes, and for different modules or components. The types of property damage considered include breakdowns due to windstorms, lightning strikes, fires, as well as other mechanical and electrical breakdowns. The damage events are also analyzed from a component perspective including major items such as turbine blades, generators, gearboxes, other electrical and mechanical components etc. The risk of wind turbine property losses is discussed in terms of both frequency and severity of the events. The study reveals important trends of wind turbine property losses and indicates potential paths to effective loss prevention for various stakeholders in the wind energy industry.
Parametric Modeling and Economic Analysis of a 2MWth 3-Stream sCO2 Heat Exchanger
Authors: Neveu Joshua , Pryor Owen , Cich Stefan , Stechel Ellen 
Published: October 2022

Abstract
This paper presents the design and cost optimization of a novel 2MWth 3-stream sCO2 plate-fin heat exchanger. This heat exchanger design is unique in that it uses reduced metal oxide particle-to-sCO2 heat exchanger for cost-effective energy storage applications. The design uses low velocity, laminar air as the re-oxidizing reactant to transfer the heat of the re-oxidizing reaction to a sCO2 power loop. The design of the heat exchanger is based on a 2-D, 3-fluid plate/fin heat transfer model. The model parameterizes the size, shape, and number of passages of the heat exchanger to calculate the temperature profile, pressure drop, and fluid velocities of all three fluids. Global heat exchanger parameters such as the effectiveness and total heat transferred to the sCO2 are then calculated for overall performance. Due to the value and increased use of sCO2 heat exchangers in power cycles, a cost model of the system based on the unique high temperature/high pressure operating conditions was created using quotes from reference projects and market analysis. These quoted air-to-sCO2 heat exchangers are then processed using multiple weighting factors pertinent to heat exchanger design, including heat exchanger type, maximum temperature, differential pressures, fluids, duty, and more. These factors are then used in an exponential function in order to generate a parameterized cost curve. The design and cost of the heat exchanger are then optimized using the SMPSO genetic algorithm in Python. The optimization objectives for the system are to maximize the overall system effectiveness, including an air recuperator for preheating, and to minimize unit costs. Additional constraints are added to the system for the sCO2 and air pressure drops, air velocity to reduce particle entrainment, and the length and volume of the heat exchanger.
A Framework for Estimating Effects of Combustor Turbulence on Turbine Profile Loss Generation
Authors: Gakhar Kanika , Folk Masha , Greitzer Edward M. , Tan Choon S. 
Published: October 2022

Abstract
This paper describes a framework to quantify the effect of freestream turbulence, generated by mixing processes in a combustor, on turbulent boundary layer loss generation in the high pressure turbine downstream of the combustor. The regime of freestream turbulence common to gas turbine aero engines is identified and it is shown that the dissipation loss coefficient in this regime can be determined using existing measurements of the effect of freestream turbulence on skin friction. The paper shows that combustor-generated freestream turbulence can increase the profile loss coefficient of a typical high pressure turbine blade by as much as 28%. A relation has been derived between a non-dimensional turbulence parameter, which characterizes the freestream turbulence, and the increase in turbine boundary layer dissipation, which quantifies the decrease in turbine efficiency. The relation provides guidelines for combustor turbulence modifications that lead to turbine performance benefits. The framework has been applied in example trade studies which show that increasing the size of dilution ports and increasing the length of the combustor can decrease high pressure turbine profile loss generation to potentially increase stage efficiency up to 0.5%.
Vortex-Generators Reduce the Dynamic Axial Forces in the Model of a Steam Turbine Control Valve
Authors: Wallat Stefan , Musch Christian , Brillert Dieter 
Published: October 2022

Abstract
Control valves of steam turbines are exposed to large static and dynamic forces caused by pressure fluctuations, turbulence and other influences, especially in part-load operation. Excitation of acoustic modes in cavities is one of these causes that leads to fluctuating forces on parts of the valve especially the valve plug. In control valves, the acoustic mode can be excited by unstable periodic behaviour such as shear layer flow. This shear layer flow occurs behind the valve seat in the diffuser between the wall jet and a backflow region in the core of the diffuser.
This paper describes the occurrence of increased fluctuating axial forces on the valve plug in a control valve for steam turbines due to the excitation of an acoustic mode in the rear cavity between the valve plug and the valve cover. In the first step, an initial geometry is investigated in a test rig. The occurrence of an acoustic mode and the effects on the valve plug were measured using force, pressure and displacement sensors. The results are presented in this paper and compared to numerical results from previous studies.
In the second step, vortex-generators are installed in the same model valve and their effects on the excitation of the acoustic mode in the rear cavity are investigated. It is shown that the vortex-generators upstream of the valve seat effectively create vortices that affect the flow topology downstream of the valve seat. This weakens the excitation of the acoustic mode and reduces the axial forces.
Efficient Modelling of Blade Film Cooling in Gas Turbines
Authors: Penrose Justin , Zori Laith , Morales Juan Carlos , Patil Sunil , Pons David , Rida Samir 
Published: October 2022

Abstract
One of the most effective ways to mitigate thermal fatigue in a high-pressure turbine’s blades is by cooling the blade from inside and outside via an intricate cooling system. The cooling flow passes from the blade interior through many small holes to form a cooling film on the blade surface. In the early blade design phases, the designers must accurately determine the location, the pattern, the distribution density, the shape, and the size of cooling holes to maximize the blade film cooling whilst maintaining the external aerodynamics. Hundreds of simulation cycles may be needed to reach an optimal design.
In this work, a film-cooling model and associated workflow are proposed. The model implementation within Ansys-Fluent uses a virtual-boundary concept which does not require the explicit resolution of the holes. The benefit of this is its compatibility with existing turbomachinery solution methods, and the consistency with subsequent mesh refinement toward resolved hole geometry. The workflow will allow designers to dissociate the uncooled aerodynamic geometry and mesh from the hole/film-cooling design, during the early design iterations.
For verification of this approach, results for a simplified single hole-setup on a flat plate are first presented. A typical gas turbine vane configuration is then used to demonstrate industrial application. The results from an aerodynamic mesh refinement study show good agreement with the resolved model. Flexibility within the workflow for changing the location, shape and properties of the holes is also demonstrated. This approach, therefore, represents a useful design tool where multiple hole pattern configurations could be quickly assessed.
Explainable and Interpretable AI-Assisted Remaining Useful Life Estimation for Aeroengines
Authors: Protopapadakis Georgios , Apostolidis Asteris , Kalfas Anestis I. 
Published: October 2022

Abstract
Remaining Useful Life (RUL) estimation is directly related with the application of predictive maintenance. When RUL estimation is performed via data-driven methods and Artificial Intelligence algorithms, explainability and interpretability of the model are necessary for trusted predictions. This is especially important when predictive maintenance is applied to gas turbines or aeroengines, as they have high operational and maintenance costs, while their safety standards are strict and highly regulated. The objective of this work is to study the explainability of a Deep Neural Network (DNN) RUL prediction model. An open-source database is used, which is composed by computed measurements through a thermodynamic model for a given turbofan engine, considering non-linear degradation and data points for every second of a full flight cycle. First, the necessary data pre-processing is performed, and a DNN is used for the regression model. The selection of its hyper-parameters is done using random search and Bayesian optimisation. Tests considering the feature selection and the requirements of additional virtual sensors are discussed. The generalisability of the model is performed, showing that the type of faults as well as the dominant degradation has an important effect on the overall accuracy of the model. The explainability and interpretability aspects are studied, following the Local Interpretable Model-agnostic Explanations (LIME) method. The outcomes are showing that for simple data sets, the model can better understand physics, and LIME can give a good explanation. However, as the complexity of the data increases, both the accuracy of the model drops but also LIME seems to have difficulties in giving satisfactory explanations.
The Pore Size Dependence of the Radiative Scattering Coefficient in Yttria-Stabilized Zirconia Films
Authors: Wang Yao , Hsu Pei-feng , McCay Mary Helen 
Published: October 2022

Abstract
The yttria-stabilized zirconia (YSZ) top coat provides a thermal resistance function in the thermal barrier coatings used in gas turbines and Diesel engines. Besides the thermal conductivity, the thermal radiative properties, especially their dependence on the coating microstructure, under the high temperature combustion temperature are critically needed to the design and operation of the thermal barrier coating (TBC) systems. In this study ceramic oxide films made of thermally sprayed YSZ powder are prepared with three average porosities 5.9%, 14.5%, and 23.3% at film thickness from 283 to 955 μm. These films are fabricated with the air plasma spray (APS) deposition on the aluminum surface. The porosity changes are accomplished by varying the spraying parameters or ceramic oxide powder particle size. The room-temperature, spectral directional-hemispherical transmittance and reflectance are measured over the wavelength range from 1.35 to 2.5 μm. The radiative properties of absorption and scattering coefficients are reduced by using a hybrid method of the discrete ordinate method and the Kubelka-Munk four-flux method, depending on the film’s optical thickness. The films are then mounted, sectioned, and polished for SEM imaging. Using the image processing tools developed in-house, the porosity and pore size distribution (PSD) are obtained for each film. A numerical algorithm is used to convert the two-dimensional PSD into a three-dimensional PSD assuming all pores are spheriod. The absorption and scattering coefficients can be computed directly by the Mie theory based on the electromagnetic wave scattering from a distribution of sphere sizes. The new approach provides a predictive model of radiative properties based on the pore size distribution and pore number density, which are dependent on the APS spraying parameters, powder size and morphology. Comparison of radiative properties obtain by direct Mie theory computation and those obtained by reduction from spectral measurement is made and discrepancy is discussed.
An Experimental Study of Supercritical Methane Injection Characteristics in a CO2 Environment
Authors: Ghorpade Ritesh , Kim Gihun , Manikantachari (Raghu) K. R. V. , Weiner Joshua , Banuti Daniel T. , Vasu Subith 
Published: October 2022

Abstract
Clean energy generation is gaining significant attention from industries, academia, and governments across the globe. The Allam cycle is one such technology that has been under focus due to its efficiency, environmental friendliness, and economics. This is a direct-fired cycle operating at supercritical conditions using carbon dioxide as a working fluid. Fuel or oxidizer jet mixing with CO2 is a vital phenomenon that governs combustion efficiency, and it is not well understood for the Allam cycle conditions. This paper experimentally and computationally investigated the jet characteristics of a methane jet injected into a subcritical to supercritical carbon dioxide environment. A wide range of injection pressures and temperatures were targeted between subcritical to supercritical conditions. Unlike previous studies, the current work focused on injecting lower-density (methane) jets into higher-density (carbon dioxide) environments. Schlieren imaging and methane absorption measurements were simultaneously performed with a CMOS high-speed camera and a 3.39 μm infrared laser. Specifically, we looked at the classical injection parameter of jet spreading angle, which was classically established to be mainly a density ratio function. Here, the jet cone angle was obtained from the post-processed schlieren videos. The jet cone angle is a critical characteristic parameter that describes the entrainment rate in a jet; thus, it is a crucial parameter in understanding the nature of the jet. The laser measurements were only used as an additional check to confirm the entry time of methane into the chamber filled with carbon dioxide. Notably, this paper makes a detailed comparison between the jet cone angles of jets with a density ratio. The result showed that the classical correlations, such as Abramovich’s theory applied to submerged turbulent gas jets developed for low-density ratio jets, were unsuitable for higher-density ratio jets. It was also observed that the divergence angles were dependent not only on density ratio but also on other parameters such as pressure ratios and reduced pressures.
CAD Integrated Gradient-Based Aero Optimization of the NASA Rotor 37
Authors: Tran Thanh-Son , De Bruyn Tom , Verstraete Tom 
Published: October 2022

Abstract
The present paper aims to optimize one of the highly loaded, compact, axial compressors investigated by NASA, using modern RANS-based optimization techniques. The NASA rotor 37 blade is used as a starting point and has been approximated by a CAD-based parametrization. Predictions by the RANS solver are compared with experimental and numerical data to validate the models. A gradient-based aero-optimization is performed to improve the performance on a single operating point while maintaining the same mass flow. The gradients are obtained through an adjoint approach where the cost is nearly independent of the number design variables. Particular attention is given to the quality of the computed sensitivities to reach a better convergence. A total of 53 design variables from the blade, hub, and shroud geometry are used to define the design space of the compressor. A 5.5% relative improvement in total-to-total efficiency is achieved by a Sequential Quadratic Programming optimization algorithm. While the efficiency is improved at a single operating point, the full operating map shows a narrow efficiency peak with a wider operating range toward the stall condition. Nonetheless, the overall performance of the optimized design is significantly improved compared to the baseline performance, with a limited computational effort.
Effect of the Axial Compressor Tip Clearance Size: Performance and Transition to Rotating Stall
Authors: Rannou Clémence , Dazin Antoine , Marty Julien , Tanguy Geoffrey , Castillon Lionel , Moubogha Joseph 
Published: October 2022

Abstract
The leakage flow that is developed between the rotor and the casing of an axial compressor is usually associated with losses and can promote the arising of rotating stall. During its life, an axial compressor can be subject to a variation of the tip clearance due to the aging of the machine, which can modify the leakage flow and affect its performance. The prediction of the tip leakage flow and of its evolution with gap size is thus essential to estimate correctly the performance and operability of a compressor stage. The support of this study is a single stage compressor for which three different gap size ratios R=τc=3.4%, defined by the tip gap size τ over the axial chord c) are considered (R = 0.6 %, 1.2 %, 2.4 %). Reynolds Averaged Navier-Stokes (RANS) simulations are performed on the three configurations. The analysis is performed with two types of computational domains (a single blade-channel and one tenth of the full annulus geometry). The aim is to identify the configuration which provides reliable results at the most reasonable computational cost. Then, a numerical study on the effect of the tip gap size on the performance and flow topology of the compressor is conducted, especially at near stall operating conditions.
Mission Severity Assessment Based on 1Hz Engine Data
Authors: Scarso Stefano , Staudacher Stephan , Keller Christian , Mathes Jürgen 
Published: October 2022

Abstract
The severity of a flight mission depends on a wide range of operating conditions caused by aircraft, pilot and engine control system interaction. However, today’s availability of continuously sampled data offers the chance to relate the severity of a mission to the details of operation. In this work, 1 Hz measurements are taken from the DASHlink dataset of NASA. Other measurements not directly available in the dataset are synthesized through an engine model. Those are then used to calculate a severity parameter and a set of non-dimensional groups which are averaged for each flight. Based on those, a severity classification is performed on a sample of flight missions. The severity classification algorithm consists of a principal component analysis and a support-vector machine model. The accuracy and the robustness of the severity classification algorithm are evaluated for several flight missions. The contribution of each flight segment to the severity of the entire flight mission is discussed. The mean flight mission severity for the engine of highest and lowest operating time on a particular aircraft are compared and results are discussed. Finally, the ability to identify more than two severity groups is discussed.
Large Eddy Simulation of Energy Transport in Highly Compressible Transverse Jets
Authors: Guo Hao , Jiang Peixue , Zhu Yinhai 
Published: October 2022

Abstract
Large eddy simulation is performed to study the thermal energy transport and mixing process of a round laminar jet in a fully-turbulent high-Mach-number crossflow. In this study, the energy equation of highly compressible fluid is systematically analyzed and the contributions of each term in the equation are compared quantitatively. Turbulent enthalpy transport is found to be in the same order of magnitude as the advection term associated with mean motion and thus is not negligible when considering the convective heat transfer problem of film cooling, which differs from the conclusion drawn from the incompressible-jets-in-crossflow studies. The inaccuracy of RANS turbulent modeling caused by counter-gradient transport of enthalpy is explained in detail and a more reasonable three-dimensional analysis method is proposed for in-depth mechanism analysis and turbulent model improvement. The numerical results also show that the contribution of mean motion to the overall kinetic energy dissipation in thermal energy transport is dominant in the near-field region where jets and crossflow interact and mix intensively while the turbulent kinetic energy dissipation term predominates in most other regions. Moreover, the irreversible increase in entropy caused by dissipation and heat transfer in the flow field is compared. The results show that the entropy production due to the latter one cannot be ignored when dealing with large temperature difference film cooling which is common in high-pressure turbines.