bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retrofittable Solutions to Keep Existing Gas Turbine Power Plants Viable and Profitable in an Increasingly Dynamic Power Generation Market: Validation of Low Pressure Drop FlameSheet™ Combustor
Authors: Hernandez Fred , Rizkalla Hany 
Published: November 2019

Abstract
As renewable energy sources continue their global energy market penetration, new natural gas fired power plant installations have decreased significantly. The reduction in new installed capacity has increased pressure on operators to profitably maintain and expand their existing fleet capability. Retrofitting existing gas turbines to increase baseload power output, expand fuel flexibility and provide a wider operating load range are key natural gas fired power plant market demands. The FlameSheet™ combustor system addresses these considerations with a novel “dual-zone burn system” design that reduces emissions, increases fuel flexibility and reduces pressure losses to improve thermal cycle efficiency. The present work presents the results of FlameSheet™ installations into GE 7F.03 heavy duty gas turbines at two commercial sites. The first installation combined FlameSheet™ with PSM’s Gas Turbine Optimization Package (GTOP) to provide higher output through a combination of lower combustor pressure drop, higher mass flows and an increase in firing temperature, while maintaining sub-9ppm NOx emissions across the expanded operating range. Results are also presented for a second site on a unit that operates with up to 5% hydrogen blend into the baseline natural gas, where a reduction in NOx to sub-4 ppm levels at a typical 7F.03 baseload point has been safely and reliably achieved. Both results continue to demonstrate that fuel flexibility and expanded operational windows are possible to “future proof” existing gas turbine installations at a fraction of the cost of a new unit installation.
Evaluating the Effects of Transient Purge Flow on Stator-Rotor Seal Performance
Authors: Berdanier Reid A. , DeShong Eric T. , Thole Karen A. 
Published: November 2019

Abstract
As modern engine designs target higher efficiencies through increased turbine inlet temperatures, critical turbine components are at increased risk of damage from conditions exceeding material melting temperatures. In particular, improperly designed underplatform hardware components are susceptible to damage when hot main gas path flow is ingested into the stator-rotor cavity. While all turbines inherently experience transients during operation, a majority of turbine tests have been executed using steady operating conditions, and routine transient events are not well understood. To address this need, the present study utilizes a continuous-duration, one-stage test turbine operating with true-scale engine hardware and seal geometries at engine-representative flow conditions. The nature of the continuous-duration facility uniquely supports direct assessment of transient events through its ability to transition between steady-state operating conditions. Specifically, the effects of a transient purge flow were investigated in this study to identify general trends for transient events in a full-scale engine. Results from multiple measurement techniques in the wheelspace region show an interdependence of transient purge flow with a thermal lag of the underplatform hardware. Through experiments conducted at different coolant-to-main gas path temperature ratios, the use of pressure measurements as an indicator of fully-purged behavior was introduced, and a thermally-driven influence on rim seal performance was quantified.
Efficient Passage-Spectral Method for Unsteady Flows Under Stall Conditions
Authors: Romera David , Corral Roque 
Published: November 2019

Abstract
This paper presents an efficient method of approximating unsteady flows using a blockwise discrete spatial Fourier series for the modeling of three-dimensional non-axisymmetric flows without making any hypothesis about its temporal periodicity. The method aims at capturing the long wavelength flow patterns which are present in many unsteady problems of industrial interest, such as compressor stability, with a drastic reduction in computational resources. The method is intended to be used to compute flows exhibiting large-scale instabilities and where the fundamental frequency of the problem is not known beforehand. The approach discretizes the domain using a finite number of blocks or passages, where the flow variables at the supposedly periodic boundaries are continuously updated using the spatial Fourier coefficients of a uniformly spaced set of reduced-passage domains. The NASA rotor 67 under stall conditions has been used as verification validation case to demonstrate the effectiveness and viability of the proposed modeling strategy. The comparison between the solutions obtained with the discrete Fourier series and the full-annulus solution shows that accurate solutions can be obtained with a low number of harmonics. The new method has been applied to investigate the rotating stall inception of the NASA rotor 67 for clean and distorted inlet flow near stall operating conditions. The method is shown to accurately reproduce the full-annulus solution with a few spatial harmonics, capturing the characteristic features of the complex flow induced by the tip leakage vortex breakdown. The computational cost in this application has been reduced by a factor of between three and seven, although this number heavily depends on the ratio between the number of retained harmonics and the number of blades.
Validation of CFD Analyses Results With Instrumented Ground and Flight Tests Measurements of an Aerobatic Turboprop Aircraft Inlet
Authors: Pitel Welnitz Daniela , Vlach Tomas , Lombardi Luca , Faltot Pierre-Jean , Vertenoeuil Philippe , D’Ercole Michele 
Published: November 2019

Abstract
With the onset of affordable high-performance computing and cloud computing technologies, numerical methods like computational fluid dynamics and the finite element method are spreading to all the branches of industry. The ability to perform such analyses allows engineers to speed up development and refine designs even in early stages of development without the need for expensive experimental setups. However, it is desirable to build up confidence in these results by experimental validation. GE Aviation Czech has been extensively using a variety of CFD tools to predict flow behavior in the field of internal aerodynamics — especially for design of compressor and turbine stages, combustion chambers, inlet and exhaust systems. Development of a new aerobatic engine prototype and its installation is currently under way. A series of back-to-back analyses conducted to verify performance of the aerobatic inlet and compare it with a reference commuter engine installation. The results were presented in article “GT2018-76398 Analysis and Testing of an Aerobatic Turboprop Aircraft Inlet”. A variety of critical parameters such as ram factor, pressure losses, inlet heating, and engine inlet pressure and temperature distortions were investigated. These parameters affect engine performance, operability, and compressor stability. Afterward, a unique instrumentation, data acquisition chain, and test program was developed in cooperation with the airframer. This made it possible to record all of the required parameters during ground and flight tests, including basic aerobatic maneuvers. The recorded data was then used for validation of performed CFD analyses with boundary conditions matching the conditions of ground and flight tests. Confidence in CFD results backed up by well-matched test data allows to conduct future design changes without the need to perform additional expensive experimental trials.
A New Mistuning Identification Method Based on the Subset of Nominal System Modes Method
Authors: Waldherr Christian U. , Buchwald Patrick , Vogt Damian M. 
Published: November 2019

Abstract
The mistuning problem of quasi periodic structures is subject of numerous scientific investigations for more than 50 years. Researchers developed reduced order models to reduce the computational costs of mistuning investigations including finite element models. One question which has also high practical relevance is the identification of mistuning based on modal properties. In the present work, a new identification method based on the Subset of Nominal System Modes method (SNM) is presented. The input data for the identification procedure consists solely of the mistuned natural frequencies of the investigated mode family as well as of the corresponding mistuned mode shapes in the form of one degree of freedom per sector. The reduction basis consists of the tuned mode shapes of the investigated mode family. Furthermore, the proposed identification method allows for the inclusion of centrifugal effects like stress stiffening and spin softening without additional computational effort. From this point of view the presented method is also appropriate to handle centrifugal effects in reduced order models using a minimum set of input data compared to existing methods. The powerfulness of the new identification method is demonstrated on the example of an axial compressor blisk. Finite element calculations including geometrical mistuning provide the data base for the identification procedure. The correct functioning of the identification method including measurement noise is also validated to show the applicability to a case of application where real measurement data is available.
Development and Analysis of an Integrated Mild-Partial Gasification Combined (IMPGC) Cycle: Part 2 — Comparison With Other Power Generation Systems
Authors: Long Henry A. , Wang Ting 
Published: November 2019

Abstract
The baseline Integrated Mild-Partial Gasification Combined (IMPGC) Cycle model developed in Part 1 is compared with other established power system designs, including the likes of subcritical and ultra-supercritical (USC) Rankine cycle systems, Natural Gas Combined Cycle (NGCC) systems, and Integrated Gasification Combined Cycle (IGCC) systems. A comprehensive comparison and analysis of the pros and cons, the thermodynamic performance, and environmental impact of each system are performed. The results show that, with a very conservative approach, IMPGC consistently outperforms all other forms of coal-based power, being outclassed only (expectedly) by NGCC. IMPGC is more efficient than the standard subcritical Rankine cycle by nine percentage points, more than a USC Rankine cycle by nearly four points, and more than IGCC by seven points.
Modeling Thermally Grown Oxides in Thermal Barrier Coatings Using Koch Fractal
Authors: Warren Peter , Haldar Sandip , Raghavan Seetha , Ghosh Ranajay 
Published: November 2019

Abstract
Growth of the Thermally Grown Oxide (TGO) between the bond coat and thermal barrier coating (TBC) during service is one of the most common causes of failure within thermal barrier coating (TBC) systems. Initially this oxide will provide protection from oxidation for the substrate, but stress build up will contribute to delamination of the topcoat. Research has been carried out over the stresses caused by this TGO growth, and how to best mitigate these induced stresses. The interface topography plays a critical role for air plasma sprayed (APS) TBCs in development of stress profiles across the TGO/TBC interface [1, 2]. The APS TBCs fail by cracking in the TBC close to the TGO-TBC interface. Most models treat TGO as a sinusoidal wavelength interface. However, most TGO surfaces have been experimentally observed to have fractal like patterns at the interfacial region of the bondcoat and topcoat. Fractals provide us a better understanding of interactions at rough interfaces between two materials adhered to one another. In this work, we model the topography of the TGO using a Koch fractal. We find the geometry selected to model the TGO layer has a direct effect on the stress generation and creep strain during simulation.
A Comparison of Tip Gap Loss Sensitivity for Shrouded vs. Unshrouded Turbine Rotors
Authors: Banks William V. , Ameri Ali A. , Boyle Robert J. , Bons Jeffrey P. 
Published: November 2019

Abstract
A numerical study was conducted to evaluate the loss sensitivity of shrouded vs. unshrouded turbine rotor blades. Accuracy is demonstrated with a series of grid independence studies. Application of the methods is performed through various studies related to the effects of shrouding a High-Pressure Turbine (HPT) rotor blade for a NASA-specified N+3 timeframe single-aisle aircraft engine at takeoff conditions. Flat, Recessed, and Shrouded rotor configurations are evaluated at tip clearances from 0.25% to 4% of blade span. Mach # distributions, near-tip blade loading, and other flow characteristics are examined. Plots of stage efficiency vs. tip clearance are presented, with trends compared to available experimental data. It is shown that for the imposed boundary conditions, the addition of a shroud improves stage efficiency and significantly reduces sensitivity to tip clearance at higher clearance fractions. A casing recess is also shown to slightly increase sensitivity to tip clearance for tip clearances greater than 0.5%. Total pressure loss profiles vs. blade span are also compared, providing insight into the mechanisms behind the performance of the three configurations.
Design, Optimization and Analysis of Supersonic Radial Turbines
Authors: Inhestern Lukas Benjamin , Braun James , Paniagua Guillermo , Serrano Cruz José Ramón 
Published: November 2019

Abstract
New compact engine architectures such as pressure gain combustion require ad-hoc turbomachinery to ensure an adequate range of operation with high performance. A critical factor for supersonic turbines is to ensure the starting of the flow passages, which limits the flow turning and airfoil thickness. Radial outflow turbines inherently increase the cross section along the flow path, which holds great potential for high turning of supersonic flow with a low stage number and guarantees a compact design. First the preliminary design space is described. Afterwards a differential evolution multi-objective optimization with 12 geometrical design parameters is deducted. With the design tool AutoBlade 10.1, 768 geometries were generated and hub, shroud, and blade camber line were designed by means of Bezier curves. Outlet radius, passage height, and axial location of the outlet were design variables as well. Structured meshes with around 3.7 million cells per passage were generated. Steady three dimensional Reynolds averaged Navier Stokes (RANS) simulations, enclosed by the k-omega SST turbulence model were solved by the commercial solver CFD++. The geometry was optimized towards low entropy and high power output. To prove the functionality of the new turbine concept and optimization, a full wheel unsteady RANS simulation of the optimized geometry exposed to a nozzled rotating detonation combustor (RDC) has been performed and the advantageous flow patterns of the optimization were also observed during transient operation.
Time-Accurate Evaluation of Film Cooling Jet Characteristics for Plenum and Crossflow Coolant Supplies
Authors: Sperling Spencer J. , Mathison Randall M. 
Published: November 2019

Abstract
Gas turbine film cooling creates complicated and highly unsteady flow structures. This study seeks to examine the unsteady characteristics created by different film hole inlet geometries using a fast-response pressure sensitive paint (PSP) technique able to capture time-accurate measurements at 2000 frames per second, resolving frequencies up to 1000 Hz. Time accurate and time-averaged measurements are used to evaluate the performance of a plenum-style inlet and a crossflow-style inlet in varying turbulence environments over a flat plate. The results of this study are intended to begin the process of breaking down widely accepted time-averaged film effectiveness contours into the cumulative effects of smaller oscillating cooling jets. Jet behaviors observed in this study include a sweeping oscillation, unsteady attachment and separation from the plate, and time accurate and time average flow bias.
The behavior and performance of higher blowing ratio, separated film cooling jets depend heavily on the momentum flux ratio. Crossflow fed cooling holes show bias to the upstream side of the cooling hole with respect to the internal crossflow direction. Plenum fed cooling holes outperform crossflow fed cooling holes, and the difference increases with increasing momentum flux ratio. Cooling hole inlet geometry and momentum flux ratio affect the core of the jet, and freestream turbulence affects the periphery of the jet. Fluctuating frequencies of plenum fed and crossflow fed cooling holes were seen to be influenced by the turbulent velocity fluctuation frequency. The resulting mode shapes showed dominant side-to-side fluctuations for higher turbulence environments and a separation and reattachment motion for lower turbulence environments.
Carbon Monoxide Emission Measurements From a Supercritical CO2 Combustor Rig Using a Mid-Infrared Laser Absorption Diagnostic
Authors: Anderson James P. , Camou Alejandro , Petersen Eric L. , Harris Mark , Cusano David M. 
Published: November 2019

Abstract
A rugged, mid-infrared (IR) CO laser absorption diagnostic has been developed to monitor the amount of CO produced by a high-pressure CH4-O2 combustor test rig operating at supercritical CO2 conditions (30 MPa and 1150°C). The laser system operates at the fundamental absorption band, ν″ = 0, R(12), of CO near 4.5 μm. The mid-IR diagnostic was constructed from a tunable quantum cascade laser (QCL), an absorption cell with two window ports for monitoring CO exhaust concentration, and two IR photodetectors. Temperature and pressure sensors were mounted near the absorption cell to monitor exhaust flow conditions, and the operational wavelength of the laser was determined by a calibration process using a known mixture of CO and N2. Environmental conditions at the remote outdoor test facility posed significant difficulties in the data acquisition process for the IR diagnostic. Fluctuating environmental temperatures proved to be problematic when operating cryogenic photodetectors and stabilizing a QCL designed to operate with an internal temperature of −15°C. Improvements to the IR system included elimination of problematic stagnation regions via a new absorption cell design and an increase in the CO detection limit. During steady state conditions, the mid-IR diagnostic measured the CO concentration to within ± 80.6 ppm. The IR diagnostic was shown to have superior CO detection response time and the ability to resolve features not detected by other CO detector counterparts.
Pre-Test Evaluation of Probe Configuration Errors
Authors: Gillespie John , Frohnapfel Dustin , O’Brien Walter 
Published: November 2019

Abstract
Rake probes are commonly used in turbomachinery applications to measure distorted inlet flows, including both pressure and swirl distortions. An especially common configuration is the 40 probe rake array, consisting of eight identical arms equally spaced circumferentially around the inlet, each arm having five sensing locations spaced along centers of equal area. By measuring many locations simultaneously, rake probes have the advantage of expedited data collection when compared to traversing probes. However, this reduction in test time comes at the cost of rigid geometry with limited measurement locations. As a result, it is possible for rake probes to miss or exaggerate significant areas of the flow profile, such as large gradients or small features, based on the fixed location of the probe and the particular details of the distortion. The purpose of this paper is to demonstrate a procedure that can be used to evaluate the ability of any desired probe configuration (40 probe rake or otherwise) to sufficiently and accurately measure a non-uniform flow profile. Results of this procedure for a range of profiles and probe configurations are also presented.
In order to accurately determine the impact of discrete sampling on the results, two broad sets of data were generated numerically and analyzed. The first set consists of four fundamental total pressure distortions: once-per-rev circumferential, twice-per-rev circumferential, hub radial, and tip radial. The second set consists of three realistic turbofan distortion patterns: two analytic (though not fundamental) profiles, and one generated from S-duct computational results.
For all investigated patterns, Radial Distortion Intensity and Circumferential Distortion Intensity are calculated in the manner described by ARP 1420, a guideline issued by the S-16 Turbine Engine Inlet Flow Distortion Committee for measuring total pressure distortions in turbomachinery. Additionally, interpolated total pressure contours are generated for each measurement configuration. These were then used to make point-to-point comparisons between the actual and estimated data. While total pressure distortion was used as the variable of interest for the majority of this paper, the conclusions may be applied to swirl, temperature, or any other flow property measured using a probe rake or traversing probe.
Multi Objective Optimization of Flexible Supercritical CO2 Coal-Fired Power Plants
Authors: Alfani Dario , Astolfi Marco , Binotti Marco , Campanari Stefano , Casella Francesco , Silva Paolo 
Published: November 2019

Abstract
Coal-fired power plants play a major role in large scale power generation by producing about 41% and 25% of the electricity in the world and in the EU, respectively. In the context of EU’s climate and energy policy (EU Reference Scenario 2016) and with a view to decarbonizing the electricity sector, the share of non-programmable renewable energies will soar in future years both in and outside the EU. As result, the role of fossil-fuel plants including coal-fired plants is expected to evolve, leading to a paradigm shift for their design and operation, which will move from constant base-load operation to increasingly variable power production for the integration of intermittent renewable energy sources. In the present work, developed within the EU project sCO2-Flex, the design and analysis of a coal-fired plant implementing a 100 MWel recompressed sCO2 power cycle is assessed, with particular focus on the trade-off between system performance and flexibility. The effects of the different design assumptions on the overall components’ sizing and system performance are investigated and a methodology to quantify the thermal inertia and the system flexibility based on the calculation of heat exchangers surfaces, volumes and masses (boiler tube walls and convective pass, recuperators and gas cooler heat rejection unit) is then presented. Finally, the cycle optimization is repeated with the aim to find the optimal trade-off between plant efficiency and thermal inertia, eventually providing a number of promising designs for next generation sCO2 fossil fuel power plants.