bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Possibilities for Analyzing Complex Asynchronous Blade Vibrations From Tip-Timing Data Using a Sparse Spectral Analysis Method
Authors: Bouchain Antoine , Picheral José , Lahalle Elisabeth , Vercoutter Agathe , Burgardt Bertrand , Talon Arnaud 
Published: November 2019

Abstract
Measurements in engine operation provide key information for understanding the blades vibrating behaviors, especially while observing complex asynchronous vibrations, such as flutter. The studied vibration is performed by the spectral analysis of the measured vibrating mechanical responses. In this context, tip-timing measurement technology enables to get a large amount of information as it monitors all the blades. However, tip-timing technology generates sub-sampled and non-uniform sampled signals. Thus, conventional spectral estimation methods lead to aliased frequency components on the spectrum. Therefore, specific estimation methods have been developed to overcome this issue.
This paper presents the tip-timing measurements analysis of a non synchronous vibration test case. It uses a new sparse method with block-OMP algorithm in order to estimate time-frequency diagrams of each blade separately. The results are compared to the results of the well-known asynchronous tip-timing method, called All Blade Spectrum. This real test case highlights the limitations of the latter method, as it involves too much uncertainty, while the sparse method with block-OMP enables to characterize these complex asynchronous blade vibrations.
Evaluating the Effect of Vane Trailing Edge Flow on Turbine Rim Sealing
Authors: Monge-Concepción Iván , Berdanier Reid A. , Barringer Michael D. , Thole Karen A. 
Published: November 2019

Abstract
Modern gas turbine development continues to move toward increased overall efficiency, driven in part by higher firing temperatures that point to a need for more cooling air to prevent catastrophic component failure. However, using additional cooling flow bled from the upstream compressor causes a corresponding detriment to overall efficiency. A primary candidate for cooling flow optimization is purge flow, which contributes to sealing the stator-rotor cavity and prevents ingestion of hot main gas path flow into the wheelspace. Previous research has identified that the external main gas path flow physics play a significant role in driving rim seal ingestion. However, the potential impact of other cooling flow features on ingestion behavior, such as vane trailing edge (VTE) flow, is absent in the open literature. This paper presents experimental measurements of rim cavity cooling effectiveness collected from a one-stage turbine operating at engine-representative Reynolds and Mach numbers. Carbon dioxide (CO2) was used as a tracer gas in both the purge flow and vane trailing edge flow to investigate flow migration into and out of the wheelspace. Results show that the vane trailing edge flow does in fact migrate into the rim seal and that there is a superposition relationship between individual cooling flow contributions. Radial and circumferential traverse surveys were performed to quantify cooling flow radial migration through the main gas path with and without vane trailing edge flow. The surveys confirmed that vane trailing edge flow is entrained into the wheelspace as purge flow is reduced. Local CO2 measurements also confirmed the presence of VTE flow deep in the wheelspace cavity.
Effect of a Premixed Pilot Flame on the Velocity-Forced Flame Response in a Lean-Premixed Swirl-Stabilized Combustor
Authors: Li Jihang , Peluso Stephen , Santavicca Domenic , Blust James 
Published: November 2019

Abstract
The effect of a fully-premixed pilot flame on the velocity-forced flame response of a fully premixed flame in a single-nozzle lean-premixed swirl combustor operating on natural gas fuel is investigated. Measurements of the flame transfer function show that as the percent pilot is increased there is a decrease in the flame transfer function gain at all frequencies, a decrease in the frequencies at which the gain minima and maxima occurred, and a decrease in the flame transfer function phase at high frequencies.
High-speed CH* chemiluminescence flame imaging is used to gain a better understanding of the mechanism(s) whereby the pilot flame affects flame dynamics and thereby the flame transfer function.
Time-averaged flame images show that the location of the maximum heat release rate does not change with forcing frequency or percent pilot, although the flame extends further upstream into the inner shear layer with increasing percent pilot.
Heat release rate fluctuation images show that significant heat release rate fluctuations occur in the inner shear layer, the outer recirculation zone, and the near wall region and that the primary effect of increasing the forcing frequency or the percent pilot is a shift of the heat release rate fluctuation from the near wall region to the inner shear layer. In addition, an increase in the percent pilot results in lengthening and narrowing of the inner shear layer and the near wall regions.
The phase images show that the phase is less uniform as the frequency or percent pilot increase, resulting in greater interference between in phase and out of phase fluctuations which reduces the FTF gain. The phase images also show that the wavelength of the heat release rate perturbation travelling through the inner shear layer decreases with increasing frequency and percent pilot which suggests that the pilot flame alters the recirculation flow field.
Flame transfer functions calculated for the heat release rate fluctuations in the inner shear layer, the near wall region and the outer recirculation zone show that the inner shear layer is the largest contributor to the global heat release rate fluctuation in the unpiloted flame and that the primary effect of the pilot flame on the reduction of the global FTF gain is a result of the pilot flame’s effect on the inner shear layer.
Thermal-Fluid and Mechanical Investigations of Additively Manufactured Geometries for Transpiration Cooling
Authors: Min Zheng , Parbat Sarwesh Narayan , Yang Li , Chyu Minking K. 
Published: November 2019

Abstract
Transpiration cooling has always been the dream of gas turbine high temperature component design. The uniform coolant coverage and enhanced heat transfer in porous wall provided by this cooling technique can significantly reduce the base metal temperature which is essential for improving working efficiencies and operation life of gas turbine. Recently, with the capability of the innovative powder bed direct metal laser sintering (DMLS) additive manufacturing technology, the complex geometries of transpiration cooling part could be precisely fabricated and endued with improved mechanical strength. In the present study, five different schemes of transpiration cooling including (1) round holes with 1.5d in-line pitch, (2) round holes with 2d in-line pitch, (3) round holes with 3d in-line pitch, (4) round holes with 2d staggered pitch, (5) inclined holes (20° inclination towards the main stream direction) with 2d in-line pitch in In718 superalloy plates were fabricated by direct metal laser sintering (DMLS) printer. Temperature measurements of the hot side surfaces with coolant coverage were conducted to evaluate the cooling performances of those structures. Tensile bars containing the same designed structure as the heat transfer test coupons in the gauge part were printed as well for the evaluation of the ultimate tensile strength. The test results showed that the coupons with smaller pore size had higher cooling effectiveness but lower tensile strength. The smaller pitch value (P = 1.5D) and the staggered pattern could enhance the cooling performance but decrease the mechanical strength as well. Taking both cooling efficiency and mechanical strength into consideration, the 0.3mm pore size coupon with 3d in-line pitch round holes is considered to be the optimal design with cooling effectiveness of 0.48 at the injection ratio of 2.5% and ultimate tensile strength of 775.9MPa. The present research work demonstrated the potential of additive manufacturing to design and fabricate the transpiration cooling structure with high cooling efficiencies and desired tensile strength.
A Multi-Dimensional Extension of Balje Chart for Axial Flow Turbomachinery Using Artificial Intelligence Based Meta-Models
Authors: Angelini Gino , Corsini Alessandro , Delibra Giovanni , Tieghi Lorenzo 
Published: November 2019

Abstract
The main intent of this work is the exploration of the rotor-only fan design-space to identify correlations between fan performance and enriched geometric and kinematic parameters. In particular, the aim is to derive a multidimensional “Balje chart”, where the main geometric and operational parameters are taken into account in addition to the specific speed and diameter, to guide a fan designer towards the correct choice of parameters such as hub solidity, blade number, hub-to-tip ratio. This multidimensional chart was built using performance data derived from a quasi-3D in-house software for axisymmetric blade analysis and then explored by means of machine learning techniques suitable for big data analysis. Principal Component Analysis (PCA) and Projection to Latent Structure (PLS) allowed finding optimal values of the main geometric parameters required by each specific speed/specific diameter pair.
Towards Large Eddy Simulation of Rotating Turbomachinery for Variable Speed Gas Turbine Engine Operation
Authors: Jain Nishan , Bravo Luis , Kim Dokyun , Murugan Muthuvel , Ghoshal Anindya , Ham Frank , Flatau Alison 
Published: November 2019

Abstract
In this work, massively parallel wall-modeled Large Eddy Simulations (LES) are conducted to simulate flow through a single stage power turbine sector of a gas-turbine engine under realistic operating conditions. The numerical framework in the current work uses finite volume based compressible CharLES solver that utilizes a moving Voronoi diagram based grid generation. To test grid sensitivity and evaluate the capability of the solver in predicting turbomachinery flows, three grids of varying resolution are used to simulate flow through the baseline gas-turbine under design operating conditions. After assessing the flow solution quality and establishing simulation parameters, LES simulations are conducted to investigate the performance of gas-turbine at off-design conditions. The conditions include the rotor design point at 100% speed, and off-design points at 75%, and 50% speeds subject to high temperatures from the combustor exit flow. The results showed that the internal flow becomes highly unsteady as the rotational speed of rotor deviates from the design point leading to reduced aerodynamic performance. This study demonstrates that the current framework is able to robustly simulate the unsteady flow in a three-dimensional moving rotor environment towards the design of variable speed gas-turbine engines for US Army Future Vertical Lift program.
Commercialization and Fleet Experience of the 7/9HA Gas Turbine Combined Cycle
Authors: Vandervort Christian , Leach David , Walker David , Sasser Jerry 
Published: November 2019

Abstract
The power generation industry is facing unprecedented challenges. High fuel costs and increased penetration of renewable power have resulted in greater demand for high efficiency and operational flexibility. Imperatives to reduce carbon footprint place an even higher premium on efficiency. Power producers are seeking highly efficient, reliable, and operationally flexible solutions that provide long-term profitability in a volatile environment. New generation must also be cost-effective to ensure affordability for both domestic and industrial consumers.
Gas turbine combined cycle power plants meet these requirements by providing reliable, dispatchable generation with a low cost of electricity, reduced environmental impact, and broad operational flexibility. Start times for large, industrial gas turbine combined cycles are less than 30 minutes from turning gear to full load, with ramp rates from 60 to 88 MW/minute.
GE introduced the 7/9HA industrial gas turbine product portfolio in 2014 in response to these demands. These air-cooled, H-class gas turbines (7/9HA) are engineered to achieve greater than 63% net combined cycle efficiency while delivering operational flexibility through deep, emission-compliant turndown and high ramp rates. The largest of these gas turbines, the 9HA.02, is designed to exceed 64% combined cycle efficiency (net, ISO) in a 1×1, single-shaft (SS) configuration.
As of December 2018, a total of 32 7/9HA power plants have achieved COD (Commercial Operation Date) while accumulating over 220,000 hours of operation. These plants operate across a variety of demand profiles including base load and load following (intermediate) service. Fleet leaders for both the 7HA and 9HA have exceeded 12,000 hours of operation, with multiple units over 8,000 hours.
This paper will address four topics relating to the HA platform: 1) gas turbine product technology, 2) gas turbine validation, 3) integrated power plant commissioning and operating experience, and 4) lessons learned and fleet reliability.
Modelica and Functional Mock-Up Interface: Open Standards for Gas Turbine Simulation
Authors: Sielemann Michael , Thorade Matthis , Claesson Jim , Nguyen Anh , Zhao Xin , Sahoo Smruti , Kyprianidis Konstantinos 
Published: November 2019

Abstract
This paper introduces two physical modeling standards in the gas turbine and cycle analysis context. Modelica is the defacto standard for physical system modeling and simulation. The Functional Mock-Up Interface is a domain-independent standard for model exchange (“engine decks”). The paper summarizes key language concepts and discusses important design patterns in the application of gas turbine simulation concepts to the acausal modeling language. To substantiate how open standards are applicable to gas turbine simulation, the paper closes with two application examples, a conventional unmixed turbofan thermodynamic cycle and weight analysis as well as an electrically boosted geared turbofan.
Adjoint Based Aerodynamic Optimization of a Multi-Splitter Turbine Vane Frame
Authors: Russo Vincenzo , Orsenigo Simone , Mueller Lasse , Verstraete Tom , Lavagnoli Sergio 
Published: November 2019

Abstract
This work presents a 2D optimization of a multi-body turbine vane frame (TVF), a particular configuration that can lead to considerable shortening of the aero-engine shaft as well as weight reduction. Traditionally, the turbine vane frame is used to guide the flow from the high pressure (HP) turbine to the low pressure (LP) turbine. Current designs have a mid turbine frame equipped with non lifting bodies that have structural and servicing functions, while multi-body configurations are characterized by the fact that, in order to shorten the duct length, the mid turbine struts are merged with the LP stator vanes, traditionally located downstream. This design architecture consists therefore of a multi-body vane row, where lifting long-chord struts replace some of the low pressure vane airfoils. However, the bulky struts cause significant aerodynamics losses and penalize the aerodynamics of the small vanes. The objective of the present work is to numerically optimize a TVF geometry with multi-body architecture using a gradient based algorithm coupled with the adjoint approach, enabling the use of a rich design space. Steady-state CFD simulations have been used to this end. The aim of this study is to reduce the total pressure losses of the TVF, while imposing several aerodynamic and structural constraints. The parametrization of the TVF geometry represents the airfoil shapes and their relative pitch-wise positions. The outcome of the optimization is to evaluate the potential improvements introduced by the optimized TVF geometry and to quantify the influence of the different design parameters on the total pressure losses.
Development and Commissioning of a Blowdown Facility for Dense Gas Vapours
Authors: Robertson Miles C. , Newton Peter J. , Chen Tao , Martinez-Botas Ricardo F. 
Published: November 2019

Abstract
The Organic Rankine Cycle is a candidate technology for low grade heat recovery, from sources as diverse as geothermal, solar and industrial/vehicle waste heat. The organic working fluids used within these systems often display significant real-gas effects, especially in proximity of the thermodynamic critical point. Significant research has therefore been performed on the design of real-gas expansion devices, including both positive displacement and rotordynamic machinery. 3D Computational Fluid Dynamics (CFD) is commonly used for performance prediction and flow field analysis within expanders, and experimental validation of these simulations within a real-gas environment are scarce within the literature. This paper therefore presents a dense-gas blowdown facility constructed at Imperial College London, for the purpose of experimentally validating numerical simulations of these fluids.
The system-level design process for the blowdown rig is detailed within this paper, including the sizing and specification of major components. A hemispherically-ended 3.785 L cylinder was selected as the main blowdown vessel, allowing a designpoint pressure and temperature of 3751 kPa and 477 K, respectively. Regulating valves were placed either side of the test section, allowing a Pressure Ratio to be fixed across the measurement section.
The primary design focus of this paper is that of the test section — a converging-diverging nozzle producing an expansion of Mach 2 at the nozzle exit plane. The nozzle profile is generated by Method of Characteristics (MoC) modified to account for real-gas effects. Both mechanical and fluid dynamic design are discussed, along with location and thermal management of the nine pressure transducers, located along the nozzle centreline.
A series of blowdown tests are conducted, firstly for a fluid conforming closely to the ideal gas Equation of State - Nitrogen (N2) at room temperature. A comparison between the experimental measurements and a CFD analysis of these results is taken as a benchmarking example. A second set of tests with refrigerant R1233zd(E) are run, across multiple inlet pressures - CFD simulations are subsequently performed, with the refrigerant modeled by Ideal Gas, Peng-Robinson, and Helmholtz energy (via REF-PROP) Equations of State. An error analysis is conducted for each, identifying that an increase in fluid model fidelity leads to reduced deviation between simulation and experiment. An average discrepancy of 11.1% in nozzle Pressure Ratio with the Helmholtz energy EoS indicates an over-prediction of expander power output within the CFD simulation.
Analysis of Operational Effects on Cooled H-Class Gas Turbines
Authors: Uysal Selcuk Can , Black James B. 
Published: November 2019

Abstract
During the operation of an industrial gas turbine, the engine deviates from its new condition performance because of several effects including dirt build-up, compressor fouling, material erosion, oxidation, corrosion, turbine blade burning or warping, thermal barrier coating (TBC) degradation, and turbine blade cooling channel clogging. Once these problems cause a significant impact on engine performance, maintenance actions are taken by the operators to restore the engine to new performance levels.
It is important to quantify the impacts of these operational effects on the key engine performance parameters such as power output, heat rate and thermal efficiency for industrial gas turbines during the design phase. This information can be used to determine an engine maintenance schedule, which is directly related to maintenance costs during the anticipated operational time. A cooled gas turbine performance analysis model is used in this study to determine the impacts of the TBC degradation and compressor fouling on the engine performance by using three different H-Class gas turbine scenarios. The analytical tool that is used in this analysis is the Cooled Gas Turbine Model (CGTM) that was previously developed in MATLAB Simulink®. The CGTM evaluates the engine performance using operating conditions, polytropic efficiencies, material properties and cooling system information.
To investigate the negative impacts on engine performance due to structural changes in TBC material, compressor fouling, and their combined effect, CGTM is used in this study for three different H-Class engine scenarios that have various compressor pressure ratios, turbine inlet temperatures, and power and thermal efficiency outputs; each determined to represent different classes of recent H-Class gas turbines. Experimental data on the changes in TBC performance are used as an input to the CGTM as a change in the TBC Biot number to observe the impacts on engine performance. The effect of compressor fouling is studied by changing the compressor discharge pressures and polytropic compressor efficiencies within the expected reduction ranges. The individual and combined effects of compressor fouling and TBC degradation are presented for the shaft power output, thermal efficiency and heat rate performance parameters. Possible improvements for the designers to reduce these impacts, and comparison of the reductions in engine performance parameters of the studied H-Class engine scenarios are also provided.
Point Cloud to Parameter: An Inverse Geometric Approach to Probabilistic Design
Authors: Meckstroth Christopher , Brown Jeffrey 
Published: November 2019

Abstract
A method is presented to enable probabilistic design based on manufacturing blade variation. The goal of Point Cloud to Parameter (P2P) process is to autonomously extract design parameters from measured, three-dimensional scans of turbine engine blade profiles. Rather than simply determining statistical field variation in the blade surface, these extracted design parameters relate back to the creation of the original blade geometry, such that they could be utilized to recreate the blade in a CAD program. Designers can then use these results to compare and quantify design intent dimensions with manufacturing dimensions, and similarly, the intended performance of the blade. Results are presented of initial tests performed on a measured point cloud of blisk geometry with 18 blades. The parameters extracted using the P2P algorithm are compared to the results of a mesh deformation effort performed on the same geometry and it is shown that the P2P parameters correlate well with FEA computed frequencies.