bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Natural Gas Composition on Low NOx Burners Operation in Heavy Duty Gas Turbine
Authors: Romano Serena , Cerutti Matteo , Riccio Giovanni , Andreini Antonio , Romano Christian 
Published: November 2019

Abstract
Development of lean-premixed combustion technology with low emissions and stable operation in an increasingly wide range of operating conditions requires a deep understanding of the mechanisms that affect the combustion performance or even the operability of the entire gas turbine.
Due to the relative wide range of natural gas composition supplies and the increased demand from Oil&Gas customers to burn unprocessed gas as well as LNG with notable higher hydrocarbons (C2+) content; the impact on gas turbine operability and combustion related aspects has been matter of several studies.
In this paper, results of experimental test campaign of an annular combustor for heavy-duty gas turbine are presented with focus on the effect of fuel composition on both emissions and flame stability.
Test campaign involved two different facilities, a full annular combustor rig and a full-scale prototype engine fed with different fuel mixtures of natural gas with small to moderate C2H6 content. Emissions trends and blowout for several operating conditions and burner configurations have been analyzed.
Modifications to the burner geometry and fuel injection optimization have shown to be able to reach a good trade-off while keeping low NOx emissions in stable operating conditions for varying fuel composition.
High Pressure Compressor Aerodynamic Performance at Uncertain Boundary Conditions
Authors: Magin Philip , Danner Florian , Voigt Matthias , Mailach Ronald 
Published: November 2019

Abstract
The intended operating point of turbomachinery is subject to numerous kinds of uncertainty. These range from varying ambient conditions, across geometric deviations in a component, to system related loading variability resulting in engine-to-engine variation in component matching. In order to guarantee safe operation at all conditions, it is essential to consider the above uncertainties when designing turbomachinery.
In the present work, a probabilistic assessment is performed of the influence of possible operational uncertainties on the aerodynamic performance metrics of an aero-engine multistage high pressure compressor (HPC). To propagate uncertainties, Monte Carlo simulations (MCS) with Latin Hypercube Sampling (LHS) were performed, with both correlated and uncorrelated inputs. Each sample consisted of a steady state computational fluid dynamics (CFD) evaluation of the compressor. The statistical input for the boundary conditions was acquired from a MCS of the engine cycle performance at cruise, accounting for flight-to-flight variations in ambient conditions and engine-to-engine variations in component properties.
With the chosen approach, it is possible to quantify the variability in aerodynamic performance of an HPC that is subject to uncertain operating conditions and thus shows the importance of input correlations. Results highlight that deterministically determined performance metrics can differ considerably from the statistical mean, revealing the benefits of a probabilistic assessment. In contrast to performing MCS on the cycle only, a CFD based assessment can also be used to draw conclusions on the aerodynamic mechanisms responsible for changes in efficiency or surge margin.
Effect of CO2 Dilution on the Laminar Burning Velocities of Premixed Methane/Air Flames at Elevated Temperature
Authors: Duva B. C. , Chance L. E. , Toulson E. 
Published: November 2019

Abstract
With increased interest in reducing emissions, the staged combustion concept for gas turbine combustors is gaining in popularity. For this work, the effect of CO2 dilution on laminar burning velocities of premixed methane/air flames was investigated at elevated temperature through both experiments and numerical simulations. Validation of the experimental setup and methodology was completed through experimental testing of methane/air mixtures at 1 bar and 298 K. Following validation, high temperature experiments were conducted in an optically accessible constant volume combustion chamber at 1 bar and 473 K. Laminar burning velocities of premixed methane/air flames with 0%, 5%, 10% and 15% CO2 dilution were determined using the constant pressure method enabled via schlieren visualization of the spherically propagating flame front. Results show that laminar burning velocities of methane/air mixtures at 1 bar increase by 106–145% with initial temperature increases from 298 K to 473 K. Additions of 5%, 10% and 15% CO2 dilution at 1 bar and 473 K cause a 30–35%, 51–54% and 66–68% decrease in the laminar burning velocity, respectively. Numerical results were obtained with CHEMKIN [1] using the GRI-Mech 3.0 [2] and the San Diego [3] mechanisms. Excellent agreement was observed between the GRI-Mech 3.0 [2] and experimental data at ϕ ≤ 1.2 for methane/air mixtures at 1 bar and 298 K. However, for mixtures at ϕ < 1.3, 1 bar and 473 K, mixtures at ϕ < 1.2 for 5% and 10% dilutions, and for mixtures at ϕ < 0.9 for 15% dilution, laminar burning velocities predicted by the GRI-Mech 3.0 mechanism [2] were slightly higher than experimental results. The San Diego mechanism [3] showed good agreement with experimental data at ϕ ≤ 0.9 for methane/air mixtures at 1 bar and 298 K. However, for mixtures at ϕ > 0.9, 1 bar and 298 K, mixtures at ϕ > 1.2, 1 bar and 473 K, and mixtures at ϕ > 1.1 with 5%, 10% and 15% dilution, the San Diego mechanism [3] predicted slower laminar flame speeds than the experimental results. On the other hand, the laminar burning velocities predicted by the San Diego mechanism [3] were slightly faster than the experimental results for leaner mixtures. Additionally, the dilution, thermal-diffusion, and chemical effects of CO2 on the laminar burning velocities of methane/air mixtures were investigated numerically by diluting the mixtures with both chemically active and inactive CO2 following the determination of the most important elementary reactions on the burning rate through sensitivity analysis. Lastly, it was shown that CO2 dilution suppresses the flame instabilities during combustion, which is attributable to the increase in the burned gas Markstein length (Lb) with the addition of diluent.
Analysis of Vortex Ingestion Impact on the Dynamic Response of the Fan in Resonance Condition
Authors: Berthelon Thomas , Dugeai Alain , Langridge Jonathan , Thouverez Fabrice 
Published: November 2019

Abstract
Ultra high by-pass ratio (UHBR) turbofan configurations are promising concepts to address the issue of aircraft fuel burn reduction. The large fan diameter and the small ground clearance of these configurations can lead to ingestion of ground vortex during take-off phases. This vortex can be responsible of high level of vibrations and possible failure due to high cycle fatigue. The objective of the work described in this paper is to investigate the forced response due to ground vortex ingestion of a large civil fan in resonance condition. This paper is separated in three sections. The first one consists of characterizing the flow distortion induced by a ground vortex. The second part consists of evaluating the blade vibrations induced by this vortex with decoupled aeromechanical method. The numerical predictions are then compared to experimental results. And finally, the last part consists of proposing a low fidelity model based on swirl distortion in order to estimate modal aerodynamic forces in ground vortex ingestion case.
Assessing Manufacturing Repeatability of Inherently Damped Nickel Alloy Components via Forced-Response Testing
Authors: Scott-Emuakpor Onome , George Tommy , Runyon Brian , Sheridan Luke , Holycross Casey , O’Hara Ryan 
Published: November 2019

Abstract
The ability to repeat an additive manufacturing (AM) process that fabricates a unique specimen with inherent damping capability is explored. Using the Laser Powder Bed Fusion (LPBF) AM process, four Inconel 718 components with the same internal and external geometries are manufactured. The damping performance of the four specimens are determined to make comparisons against each other, previously studied inherently damped specimens, and fully-fused components of the same material and external geometry. Results of the study demonstrate similarities in the damping performance of each beam despite the specimens being made with three different fabrication parameters, two different LPBF scan strategies, and two different build sequences. Moreover, the measured inherent damping in the four beams is significantly higher (9–16 times) compared to the damping of a fully-fused beam. The results of the inherently damped beams in this study is also compared to previous specimens of different geometries using a shear-displacement criterion that determines the effectiveness of damping. The results show an 85% correlation between damping performance and calculated shear-displacement value. Therefore, despite three sets of fabrication parameters, two scan strategies, and two build sequences for the same geometry/dimensioned specimen, the results firmly demonstrate inherent damping repeatability is strongly driven by the unique geometry of the component, which ensures repeatability with minimal sensitivity in the manufacturing process.
Laser Additive Manufacturing of Titanium Aluminides for Turbomachinery Applications
Authors: Vogelpoth Andreas , Schleifenbaum Johannes Henrich , Rittinghaus Silja 
Published: November 2019

Abstract
The defect-free processing of TiAl alloy TNM™-B1 by means of Laser Powder Bed Fusion (LPBF) is demonstrated by manufacturing of an automobile turbocharger wheel. Similar precision cast material was used as reference. TNM™-B1 was manufactured crack free with a density > 99.5% using elevated process temperatures above the brittle-to-ductile transient temperature (BDTT). The preheating temperature was provided by an induction preheating system. To minimize oxygen pick up during the LPBF process, the process atmosphere was actively cleaned using a gas-purification system.
Produced test samples were analyzed in as-built and heat-treated condition regarding density, micro structure and phases by means of a Light Optical Microscope (LOM) and Scanning Electron Microscopy (SEM). Micro hardness was measured according to Vickers. Oxidation measurements were performed by means of carrier-gas hot extraction. Mechanical properties were determined using room temperature tensile tests. The final automobile turbocharger wheel was analyzed for defects using a Micro-Computer Tomography scanner (MCT).
Besides bulk test samples, thin-walled specimens can be manufactured with sufficient density. Depending on the process parameters, an oxygen content < 1000 ppm could be reached. The as-built microstructure consists of lamellar (α2+γ) colonies and nearly globular γ as well as β/β0 at the grain boundaries. High cooling rates in the magnitude of 105 to 106 K/s provide small grain sizes of 1–7 μm. Hardness measurements reveal an increased hardness (515-560HV0.3) compared to cast material (390HV0.3). Samples for tensile tests show tensile strength around 840 MPa and a total elongation of 1.1% for LPBF-manufactured and hot isostatic pressed (HIP) samples. The CT analysis of the turbocharger wheel confirms that complex geometries made of TiAl can be additively manufactured free of cracks.
Additive Manufacture of Prototype Turbine Blades for Hot-Fired Engine Performance Validation Trials
Authors: Adair David , Kirka Michael , Ryan Daniel 
Published: November 2019

Abstract
Additive manufacturing (AM), also known as 3D printing, is a rapidly developing technology with tremendous potential in both developmental and production applications. Solar Turbines Incorporated is committed to AM technology for gas turbine applications. The ability to metal 3D print novel designs of turbine blades capable of actual turbine engine operation would effectively reduce design validation cycle time, and allow acquisition of key performance data early in a design campaign. In support of Solar’s advanced manufacturing development and ongoing engine efficiency improvement goals, Solar initiated a project to print a full set of Mercury™ 50 stage 2 turbine blades to be run in a development engine.
Solar leveraged years of experience with design and serial production of AM components in support of this project. A significant challenge faced when printing turbine blades is producing metal with mechanical properties sufficient to withstand the rigors of engine operation. As a rotating component within the hot section of the engine, turbine blades experience high centrifugal and pressure loads at elevated temperatures. After investigation of possible alloys capable of meeting the requirements of the Mercury™ 50 design envelope, the gamma prime (γ’) strengthened nickel superalloy Inconel™ 738LC was selected to provide the best opportunity for successful development engine testing.
Solar partnered with Oak Ridge National Laboratory (ORNL) to produce the Inconel™ 738LC blades with Electron Beam Melting (EBM) powder bed fusion process. Once a rough blade shape was printed, the fir-tree attachment, blade tip shroud, and air flow path surfaces were finished using both conventional and non-conventional machining processes. In-process monitoring, metallurgical evaluations, mechanical testing, and non-destructive inspection techniques were used to validate the printed blade material integrity and conformance to geometric design intent. Planned future activities include assembly of the AM blades onto a disk for spin pit testing to validate the mechanical integrity and design margin of the blades. The final phase of the project will be to install the bladed disk assembly into a Mercury™ 50 engine at Solar Turbines to conduct a series of hot-fired engine performance tests.
Pressure Profile Measurements Within the Gas Film of Journal Foil Bearings Using an Instrumented Rotor With Telemetry
Authors: Shalash K. , Schiffmann J. 
Published: November 2019

Abstract
Foil bearings are strong candidates to support oil-free turbomachinery. Although foil bearings are a widely used technology, models describing their behavior are not validated using the film pressure, which is the fundamental variable of any fluid film bearing. This paper presents pressure profiles measured within the gas film of a journal foil bearing. The pressure is measured using an instrumented rotor with embedded pressure probes and wireless telemetry. The measurements yield the simultaneous circumferential pressure profiles at two axial positions inside the bearing. Proximity probes on the bearing allowed the measurement of the corresponding rotor orbits. The bearing under investigation is a bump type compliant journal bearing, with a nominal diameter of 40mm, an L/D = 1, and was tested up to 37.5 krpm. Load-displacement and break-away tests were performed on the test bearing in order to identify bearing parameters necessary for reproducibility. The pressure profiles are compared to a frequency domain foil bearing model. This paper is a step towards further fundamental understanding of the foil bearing behavior, and the validation of the rich modelling literature.
An Assessment of Machine Learning Techniques for Predicting Turbine Airfoil Component Temperatures, Using FEA Simulations for Training Data
Authors: Tallman James A. , Osusky Michal , Magina Nick , Sewall Evan 
Published: November 2019

Abstract
This paper provides an assessment of three different machine learning techniques for accurately reproducing a distributed temperature prediction of a high-pressure turbine airfoil. A three-dimensional Finite Element Analysis thermal model of a cooled turbine airfoil was solved repeatedly (200 instances) for various operating point settings of the corresponding gas turbine engine. The response surface created by the repeated solutions was fed into three machine learning algorithms and surrogate model representations of the FEA model’s response were generated. The machine learning algorithms investigated were a Gaussian Process, a Boosted Decision Tree, and an Artificial Neural Network. Additionally, a simple Linear Regression surrogate model was created for comparative purposes. The Artificial Neural Network model proved to be the most successful at reproducing the FEA model over the range of operating points. The mean and standard deviation differences between the FEA and the Neural Network models were 15% and 14% of a desired accuracy threshold, respectively. The Digital Thread for Design (DT4D) was used to expedite all model execution and machine learning training. A description of DT4D is also provided.
Transient Performance of Separated Flows: Experimental Characterization of Flow Detachment Dynamics
Authors: Saavedra J. , Paniagua G. 
Published: November 2019

Abstract
The operation of compact power units at low Reynolds environments is constrained by the boundary layer detachment in the low pressure turbines stages. Flow separation is prompt by the lack of momentum on the near wall region when exposed to adverse pressure gradients. Transient flow conditions or periodic flow perturbations induced to the near wall flow may delay or prevent the flow detachment. The present investigation experimentally analyzes the behavior of separated flows based on ad-hoc wall mounted hump. The test article mimics the performance of the aft portion of the suction side of a low pressure turbine where flow separation occurs at low Reynolds and fully attached flow takes place at high Reynolds. The inception of separated flow under sudden flow release was investigated in a linear wind tunnel. The extension of the separated region and its transient development was monitored through surface pressure and temperature measurements and hotwire traverses. The inlet flow conditions to the test article were interrogated with total pressure, total temperature and hotwire traverses. A fast opening valve upstream of the settling chamber was sequentially actuated at low frequency to study the behavior of the recirculation bubble under sudden flow acceleration. Due to the sudden flow release, the near wall region overcomes the adverse pressure gradient. As the flow acceleration dilutes the boundary layer detaches and the separated flow region grows in the stream-wise direction. The comparison of the experimental results with 2D and 3D transient Computational Fluid Dynamic simulations demonstrates the ability of Unsteady Reynolds Average Navier-Stokes models to predict the dynamics of this phenomenon. However, CFD over-predicts the extension of the recirculated flow region. The integration of this research towards future control strategies will enable efficient operation of turbine-hybrid systems operating at high power.
Design Tools to the Best Coupling of Dry-Friction Solid Underplatform Dampers to Turbine Blades
Authors: Gastaldi Chiara , Gola Muzio M. 
Published: November 2019

Abstract
This work completes the recent authors efforts in the frame of solid dampers optimization, whose goal are to develop systematic design tools to identify the best choice of an underplatform damper (shape, size) matching with a blade (size, modal features) in a turbomachine.
Step 1 was to filter out all those geometries that would lead to undesirable kinematics and contact forces. Step 2 was to identify those ranges of parameters that are better in terms of added stiffness and damping.
The purpose of this third and final step is to complete the picture by exploring how the basic geometrical design parameters of blades interact with the damper parameters and where (i.e., for which parameters combination) a designer may find the best match in view of the vibratory response under resonant excitation. The main focus is on the blades HCF safety. While steps 1 and 2 are based on simple geometrical considerations, this step 3 requires a non-linear coupled dynamic analysis of the system. It is demonstrated how the variation of crucial parameters (e.g. neck thickness, damper geometry, centrifugal force) affects the performance of a real damper coupled to a realistic blade. The method, based on reasonable simplifications, is illustrated and proposed as a tool to make the analysis attractive to designers in the early design stage by guiding their initial choice of an optimal dry friction damper.
A Statistical Characterization of the Effects and Interactions of Small and Large Mistuning on Multistage Bladed Disks
Authors: Kurstak Eric , D’Souza Kiran 
Published: November 2019

Abstract
As turbomachinery systems continue to push the limits of modern technology, the modeling techniques being developed also continue to push modern computational limits. While modeling the pristine system during the design process is important, it is equally important to model behavior of mistuned systems, due to wear or manufacturing processes. This work carries out a statistical analysis on a two-stage system consisting of integrally bladed rotors. Various forms of large geometric mistuning, such as missing mass, bends, and dents, are considered. These forms of large mistuning are based on previously reported damage seen in actual engines that have ingested volcanic ash. This work also aims to investigate the interaction of these large mistuned systems with various levels of small mistuning to further understand this complex interaction. For every case studied, a reduced order model will be constructed that includes the effects of small and large mistuning. Large mistuning will only be applied to a single sector of a single stage. Random patterns of small mistuning will be applied to each case of large mistuning after which a modal analysis and a forced response analysis are run. By observing the energy distribution of each mode for the mistuned system, a qualitative trend can be created between various types and levels of large mistuning and the impact they have on changing the dynamics of the multistage system. The amplification factors from the forced response analyses help in understanding the impact small mistuning has when coupled with large mistuning and when the effects of small mistuning dominate over the large mistuning effects.