bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of Loss Development in a Low-Pressure Turbine Cascade With Unsteady Inflow and Varying Inlet Endwall Boundary Layer
Authors: Schubert Tobias , Niehuis Reinhard 
Published: September 2021

Abstract
An investigation of endwall loss development is conducted using the T106A low-pressure turbine cascade. (U)RANS simulations are complemented by measurements under engine relevant flow conditions (M2th = 0.59, Re2th = 2·105). The effects of unsteady inflow conditions and varying inlet endwall boundary layer are compared in terms of secondary flow attenuation downstream of the blade passage, analyzing steady, time-averaged, and time-resolved flow fields. While both measures show similar effects in the turbine exit plane, the upstream loss development throughout the blade passage is quite different. A variation of the endwall boundary layer alters the slope of the axial loss generation beginning around the midpoint of the blade passage. Periodically incoming wakes, however, cause a spatial redistribution of the loss generation with a premature loss increase due to wake interaction in the front part of the passage followed by an attenuation of the profile- and secondary loss generation in the aft section of the blade passage. Ultimately, this leads to a convergence of the downstream loss values in the steady and unsteady inflow cases.
Experimental and Analytical Investigation of Cyclic Crack Initiation in Nickel Based Super Alloy With Stress Concentration Features
Authors: Torkaman Alex , Fiebiger Steve , O’Nora Nathan , O’Neal Devin , Gordon Ali 
Published: September 2021

Abstract
Accurate prediction of cycles to crack initiation in critical turbine components is a major issue in turbomachinery design, especially in components with highly concentrated stress such as turbine blades with cooling holes. Several viscoplastic and lifing methods have been used successfully to predict shakedown and cycles to failure, however complicating factors still exist that produce challenges for traditional methods. Therefore newer methods utilizing constitutive modeling with consideration for isotropic and polytropic hardening have been developed to better capture evolution of cyclic behavior of the material. Presence of mean stress and stress concentration factors are some of the complications that can be better accounted for using constitutive models. The present paper evaluates experimental and theoretical life of specimen made from nickel based super alloy with high stress concentration features under cyclic conditions with mean stress. The specimen geometry and loading were designed to mimic trailing edge holes in an F class IGT turbine blade. Experiments were conducted at an elevated temperature at two peak stress values to determine sensitivity to applied load at operating temperature similar to engine. Cycles to crack initiation are analytically evaluated using the well-known Manson-Coffin method with Morrow mean stress correction and two distinct methods for strain range evaluation. First method is the traditional Ramberg Osgood shakedown that has been extensively used in the industry. Second method is constitutive Chaboche based model run with linearized FEM results. Constants for Chaboche model are determined from Ramberg-Osgood constants with a method that takes into account yield surface evolution and hardening constants, in addition to rate dependent stress relaxation factor that can be used to model dwell time effects. Methods to decrease computational time with constitutive model are discussed. Analytical results are compared with the experimental data, and advantages and disadvantages of both methods including computational times are discussed.
The Development and Verification of a Fully Turbulent Discrete Adjoint Solver Using Algorithmic Differentiation
Authors: Wu Hangkong , Xu Shenren , Huang Xiuquan , Wang Dingxi 
Published: September 2021

Abstract
This paper presents the development and verification of a discrete adjoint solver using algorithmic differentiation (AD). The computational cost of sensitivity evaluation using the adjoint method is largely independent of the number of design variables, making it attractive for optimization applications where the design variables are far more than objectives and constraints. To obtain the gradients of a single objective function or constraint with respect to many design variables, the nonlinear flow and the adjoint equations need to be solved once at every design cycle. This paper makes a detailed presentation of how AD is used to develop a discrete adjoint solver. The data flow diagrams of the nonlinear flow, linear and adjoint solvers are compared. Moreover, a comparison of convergence history of sensitivity, asymptotic rate of residual convergence and computational cost between the linear and adjoint solvers is also made. Two cases — the subsonic Durham turbine and transonic NASA Rotor 67 are studied in this paper. The results show that the adjoint solver has the same asymptotic rate of residual convergence and produces consistent convergence history of sensitivity as the linear solver, but the adjoint solver consumes more time and memory.
Aerodynamic Design Optimization of a Variable Geometry Nozzle Vane For Automotive Turbochargers
Authors: Galloway Lee , Kim Sung in , Park Jongyoon , Kwon Seong , Yoo Sejong 
Published: September 2021

Abstract
An aerodynamic design optimization study of the nozzle vane of a variable geometry turbine (VGT) turbocharger for a diesel engine application was conducted using the commercial software, ANSYS CFX and DesignXplorer. The nozzle design was optimized at three critical engine operating points. The nozzle shape was parameterized using key design parameters including theta angle, thickness value and opening angle. For a good balance of computational time and accuracy, the optimization approach adopted meta-models and response surfaces to represent the training data and reduce the number of simulations required to reach an optimal design.
Finally, more than 300 optimized designs were simulated to assess the performance and characteristics of each design. The final optimized nozzle design met all the design constraints and showed an improvement of up to 2% efficiency and reduced the maximum torque by 20% compared to the baseline nozzle.
Educational Effectiveness of Brayton Cycle Compare and Solve Interactive Gas Turbine Simulator
Authors: Christensen Louis , Mathison Randall 
Published: September 2021

Abstract
The air-breathing Brayton cycle is widespread throughout power generation and propulsion systems, making it a staple in every mechanical or aerospace engineering student’s repertoire. Students are typically introduced to cycle analysis in a thermodynamics course and may see more in-depth coverage of gas turbines in advanced technical elective courses. In the Air-Breathing Propulsion course at The Ohio State University, students perform thermodynamic analysis on Brayton cycle engines among other topics. Pedagogy research has shown active learning to be a potent tool for enhancing student learning, and it was decided to incorporate a new active learning module into the existing course. For the module to be successful, students must achieve the learning objectives, positively accept the experience, and the module must have a minimal impact on the course structure. One lecture and one homework assignment were devoted to the use of this tool to allow students to explore gas turbine cycle analysis. A new tool, Brayton Cycle Compare & Solve, has been developed for this module. The tool can accurately perform thermodynamic design point analysis of three types of Brayton cycle engines and allow users to graphically compare the results of their analyses.
This study is done to present the tool and active learning experience to educators, capture the effectiveness of the tool in an educational setting, and determine whether students enjoy the new tool. The program is evaluated through an Institutional Review Board approved study consisting of two parts. First, students participate in a survey based on the Student Response to Instruction Practices tool to determine how the students react to and accept the active learning experience. Second, a detailed analysis of their homework responses is conducted to determine the extent to which they satisfied the learning objectives. Students unanimously felt that the learning experience with Brayton Cycle Compare & Solve is a valuable addition to the course, and homework analysis shows that their understanding of Brayton cycle analysis improved.
Flow Check and Adiabatic Effectiveness Measurements on Traditionally Versus Additively Manufactured Film-Cooling Holes
Authors: Cubeda S. , Andrei L. , Innocenti L. , Paone F. , Cocchi L. , Picchi A. , Facchini B. 
Published: September 2021

Abstract
In the recent years Additive Manufacturing (AM) methods, such as the Direct Metal Laser Melting (DMLM) technology, are getting more and more attractive and feasible for the realization of components and subcomponents of gas turbines. In particular, they are receiving much attention since, on one hand, the manufacturing of complex 3D geometries is allowed and, on the other, manufacturing and delivery times can be cut down. At the current state of the art, although AM is entering and spreading within modern gas turbines at fast pace, to the authors’ knowledge only few applications have yet been commercialized relatively to cooling holes, due to the intrinsic difficulties associated with such a critical feature.
Lately, Baker Hughes is studying the possibility to manufacture film-cooling holes via the DMLM technology in order to exploit the flexibility of such innovative manufacturing method and hence eliminate additional processes and lead time. From the open literature it is known that additively manufactured holes can have a more irregular shape and higher roughness than traditional ones, which may lead not only to a reduction in coolant flow but more importantly to a decay of the film-cooling adiabatic effectiveness. For this reason, a test campaign has been conducted in collaboration with the University of Florence (Italy) with the objective of characterizing the performance (minimum passage diameter, flow check and adiabatic effectiveness) of AM vs traditional cylindrical holes on simple-geometry coupons built upon different construction angles.
Results were then analyzed in order to fully compare the performance of AM vs traditional film-cooling holes at different operating regimes. In addition, selected holes were inspected through tomography in order to reveal the microscopic characteristics of lateral and outlet surfaces and get a further appreciation of the two different technologies. Ultimately the dependency of AM holes performance on print angles is sought with the purpose of characterizing the impact of such manufacturing technology on film-cooling holes design.
Computational Model of Mechano-Electrochemical Effect of Aluminum Alloys Corrosion
Authors: Ali Hessein , Stein Zachary , Fouliard Quentin , Ebrahimi Hossein , Warren Peter , Raghavan Seetha , Ghosh Ranajay 
Published: September 2021

Abstract
Stress corrosion is a critical issue that leads to high costs in lost equipment and maintenance, affecting the operation and safety of aircraft platforms. Most aerospace structural components use the aluminum alloys 7xxx series, which contain Al, Cu, Zn, and Mg, due to the combined advantage of its high-strength and lightweight. However, such alloys, specifically AA7075-T4 and AA7075-T651, are susceptible to stress corrosion cracking (SCC) when exposed to both mechanical stresses and corrosive environments. SCC gives rise to a major technological challenge affecting aerospace systems as it leads to the degradation of mechanical properties. In addition, such corrosion presents an important yet complex modeling challenge due to the synergistic action of sustained tensile stresses and an aggressive environment. In light of this, we develop a finite element (FE) multiphysics model to investigate the interplay of mechanical loading and electrochemistry on the stress corrosion of aluminum alloys. The model includes a multiphysics coupling technique through which the kinetics of corrosion can be predicted in the presence of elastic and plastic deformation modes. The presented model provides useful information towards the kinetics of corrosion via tracking localized corrosion and stress distribution. Although the model is general, it has been made considering the characteristics of AA7xxx series, more specifically, taking AA7075.
Decarbonizing Materials and Machining for the Gas Turbines Sector Through Life Cycle Assessment
Authors: Musacchio Alessandro , Serra Angela , Cencioni Luca , Colantoni Simone , Bartocci Pietro , Fantozzi Francesco 
Published: September 2021

Abstract
Nowadays the Energy Industry and Industrial Power Plants are committed to support sustainable development balancing environmental, social and economic benefits. Turbomachinery products, in particular gas turbines design, have to overcome the barriers imposed by: performance, lifetime and costs requirements. A new approach based on Life Cycle Assessment (LCA) is needed to define the correlation between carbon footprint and costs for different materials, manufacturing processes and production regions. To develop a decision-making tool to design sustainable products in the gas turbine sector high quality data are needed to model what is the impact of: materials and operations. Manufacturing operations (like forging and casting) and machining operations (like drilling, milling, turning, together with coating operations) are taken into account in this study. These processes have been customized to model the processes of the real supply chains used in Baker Hughes to build up a database, which is more focused on gas turbines, respect to the ones which can be found in the commercial LCA databases.
Design and Performance Analysis of a Supercritical CO2 Centrifugal Compressor With Variable Geometry
Authors: Fan Gang , Chen Kang , Zheng Shaoxiong , Du Yang , Dai Yiping , Wang Jiangfeng , Zhao Pan 
Published: September 2021

Abstract
The supercritical carbon dioxide (SCO2) Brayton cycle is one of the most promising power cycles due to its high efficiency, compactness and environmentally friendliness. The centrifugal compressor is a key component of small and medium SCO2 Brayton cycles, and its efficiency has a significant impact on the cycle efficiency. Since the required electric load of power cycles always fluctuates over the year, the SCO2 compressor will operate away from its design point and the narrow stable operating range of a compressor is always a restriction. In this paper, the variable-geometry method, which refers to the combination of a variable inlet-guide-vanes and variable diffuser vanes is proposed for the operating range extension of SCO2 compressors. A set of one-dimensional (1D) loss correlations has been found to accurately predict various losses of the SCO2 compressor components. Based on the 1D thermodynamic model, two programs with internal MATLAB codes coupled with the NIST REFPROP database have been developed for preliminary optimization design and off-design performance predictions of the variable geometry SCO2 compressor. The contributions from the variable-inlet prewhirl and variable diffuser vanes to the shifts of the surge line and choke line are discussed in this paper. The results show the variable-geometry SCO2 compressor has a superior performance at off-design conditions and a wider operating range.
Developing an Implicit Creep Model From Open Literature Data
Authors: Day William David 
Published: September 2021

Abstract
As pressure ratios and firing temperatures continue to rise, creep becomes of greater concern everywhere within a gas turbine engine. As a rule of thumb, just a 14°C increase in metal temperature can halve the expected rupture life of a part. In the past, companies might be satisfied with conservative creep estimates based on Larson-Miller-Parameter curves and 1D calculations. Now companies need functional implicit-creep models with finite element analysis for an ever-increasing number of materials. Obtaining adequate test data to create a good creep prediction model is an expensive and time-consuming proposition. Test costs depend on temperature, material, and location, but a single, 10,000hr, rupture test may reasonably be expected to cost &gt; $20,000. Other than large OEMs, small companies and individuals lack the resources to create creep models from their own data. This paper will lead the reader through the creation of a modified theta projection creep model of Haynes 282, a high-temperature, combustion alloy, using only literature data. First, literature data is collected and reviewed. Data consists of very few complete curves, estimated stresses for rupture and 1% strain, and discrete times to individual strains for individual tests. When adequate data exists, individual tests are fit to theta projection model curves. These “local” theta fits of different test conditions are used as input for the global model. Global fits of theta parameters, as a function of stress and temperature, are made from the full data set. As the global creep model is improved, correction factors introduced to account for true stress and strain effects. A statistical analysis is made of actual rupture time versus predicted onset of failure time, theta5=1. A time-based scatter factor is determined to evaluate temperature margin required to ensure reliability. After the creep model was completed, Haynes International, the material inventor, provided specific test conditions (stress and temperature) of 5 tests that had already been run. Creep predictions were generated for these test conditions, before viewing the actual results. The creep model predicted strain curves matched actual tests very well, both in shape and time to rupture. Continued refinement is possible as more data is acquired.
Associated Gas Utilization Using a Reheat Gas Turbine – Part 1: The Impact of Engine Degradation on the Optimized Power, Energy, and Revenue From Sold Electricity
Authors: Obhuo Mafel , Aziaka Duabari S. , Igbong Dodeye I. , Obhuo Ibirabo M. 
Published: September 2021

Abstract
This study presents a methodology for optimizing the power from a fleet of engines that use associated gas as fuel. The effects of engine degradation on optimized power, energy, and electricity revenue have been evaluated.
The Cranfield University TURBOMATCH has been used to simulate a 296MW reheat gas turbine. Four scenarios were considered — clean, optimistic, medium, and pessimistic. Genetic algorithm was used in optimizing the power generated from the fleets.
In the sequence of clean, optimistic, medium, and pessimistic fleets, the optimization results show that the total optimized power values are 7324.6, 7245.1, 7164.0, and 7074.4MW respectively. In the same sequence, the total energy generated is 64.2, 63.5, 62.8, and 61.9 billion kWh. In a similar sequence still, the electricity revenue is 8.487, 8.390, 8.298, and 8.192 billion US dollars respectively. In comparison with the clean, engine degradation resulted in a 1.09%, 2.19%, and 3.42% decrease in energy for the optimistic, medium, and pessimistic degraded fleets respectively. In the same sequence as the decrease in energy, degradation resulted in a 1.15%, 2.23%, and 3.48% decrease in electricity revenue.
The methodology and results presented in this paper would serve as a guide for associated gas investors in the economic utilization of this fuel resource. This is innovative; it has not been done with the Alstom GT-26 engine.
CFD Evaluation of Internal Flow Effects on Turbine Blade Leading-Edge Film Cooling With Shaped Hole Geometries
Authors: Easterby Christopher C. , Moore Jacob D. , Bogard David G. 
Published: September 2021

Abstract
In gas turbine engines, the highest heat loads occur at the leading-edge areas of turbine blades and vanes. To protect the blades and vanes, a “showerhead” configuration of film cooling holes is often used for this location, in which several rows of holes are configured closely together to maximize film coverage. Typically, these film cooling holes are fed by impingement cooling jets, helping to cool the leading edge internally, but also changing the internal flow field. The effects of these internal flow fields on film cooling are not well known, and experimental research is very limited in its ability to analyze them. Because of this, computational fluid dynamic (CFD) simulations using RANS were used as a way to analyze these internal flow fields. To isolate the effects of the impingement jet, results were compared to a pseudo-plenum internal feed, and rotation in the hole was found to be a key factor in performance. Computational results from both coolant feed configurations were compared to experimental results for the same configurations. The CFD RANS results were found to follow the same trends as the experimental results for both the impingement-fed and plenum-fed cases, suggesting that RANS is able to accurately model some of the important physics associated with leading-edge film cooling.