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research-article  
Luis San Andrés, Jing Yang and Xueliang Lu
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040766
Subsea pumps and compressors must withstand multi-phase flows whose gas volume fraction (GVF) or liquid volume fraction (LVF) varies over a wide range. Gas or liquid content in the primary stream affects the leakage and rotordynamic performance of secondary flow components, namely seals, thus affecting the process efficiency and mechanical reliability of pumping/compressing systems. This paper, complementing a parallel experimental program, presents a computational fluid dynamics (CFD) analysis to predict the leakage, drag power and rotordynamic coefficients of a smooth annular seal supplied with an air in oil mixture. The CFD seal leakage and drag power decrease steadily as the GVF increases. A multiple-frequency whirl orbit method aids in the calculation of seal rotordynamic coefficients. The injection of air in the oil immediately produces frequency dependent force coefficients; in particular the direct stiffness which hardens with frequency. The effect is most remarkable for small GVFs, as low as 0.2. The predictions of CFD and bulk-flow model (BFM), reproduce the test force coefficients with great fidelity. Incidentally, early engineering practice points out to air injection as a remedy to cure persistent vibration in vertical pumps, submersible and large size hydraulic. Presently, the model predictions, supported by the test data, demonstrate even a small content of gas in the liquid stream significantly raises the seal direct stiffness, thus displacing the system critical speed to safety. The CFD model and a dedicated test rig, predictions and test data complementing each other, enable engineered seals for extreme applications.
TOPICS: Torque, Computational fluid dynamics, Leakage, Pumps, Stiffness, Flow (Dynamics), Drag (Fluid dynamics), Reliability, Multiphase flow, Ocean engineering, Safety, Compressors, Submersibles, Whirls, Vibration
research-article  
Alessandro Orchini, Georg A. Mensah and Jonas P. Moeck
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040768
In this theoretical and numerical analysis, a low-order network model is used to investigate a thermoacoustic system with discrete rotational symmetry. Its geometry resembles that of the MICCA combustor; the FDF employed in the analysis is that of a single-burner configuration, and is taken from experimental data reported in the literature. We show how most of the dynamical features observed in the MICCA experiment, including the so-called slanted mode, can be predicted within this framework, when the interaction between a longitudinal and an azimuthal thermoacoustic mode is considered. We show how these solutions relate to the symmetries contained in the equations that model the system. We also discuss how considering situations in which two modes are linearly unstable compromises the applicability of stability criteria available in the literature.
TOPICS: Stability, Combustion chambers, Numerical analysis, Geometry, Network models
research-article  
S. Reitenbach, A. Krumme, T. Behrendt, M. Schnös, T. Schmidt, S. Hönig, R. Mischke and E. Moerland
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040750
The purpose of this paper is to present a multi-disciplinary pre-design process and its application to three aero engine models. First, a twin spool mixed flow turbofan engine model is created for validation purposes. The second and third engine models investigated comprise future engine concepts: a Counter Rotating Open Rotor and an Ultra High Bypass Turbofan. The turbofan used for validation is based on publicly available reference data from manufacturing and emission certification. At first the identified interfaces and constraints of the entire pre-design process are presented. An important factor of complexity in this highly iterative procedure is the intricate data flow, as well as the extensive amount of data transferred between all involved disciplines and among different fidelity levels applied within the design phases. To cope with the inherent complexity data modeling techniques have been applied to explicitly determine required data structures of those complex systems. The resulting data model characterizing the components of a gas turbine and their relationships in the design process is presented in detail. Based on the data model the entire engine pre-design process is presented. Starting with the definition of a flight mission scenario and resulting top level engine requirements thermodynamic engine performance models are developed. By means of these thermodynamic models, a detailed engine component pre-design is conducted. The aerodynamic and structural design of the engine components are executed using a stepwise increase in level of detail and are continuously evaluated in context of the overall engine system.
TOPICS: Design, Engines, Turbofans, Flow (Dynamics), Structural design, Manufacturing, Aircraft engines, Complex systems, Emissions, Engineering disciplines, Gas turbines, Modeling, Rotors, Flight
research-article  
Alessandro Bo, Eugenio Giacomazzi, Giuseppe Messina and Antonio Di Nardo
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040737
The work in this paper investigates on how a fuel flexible micro gas turbine (MGT) combustion chamber, developed by ANSALDO ENERGIA and installed in a Turbec T100 P MGT, can operate when transferring from natural gas to a hydrogen-rich syngas. A syngas composition which satisfies the fuel supply system specifications is identified. Such syngas contains (by volume) 45% of hydrogen, 50% of carbon dioxide and 5% of methane. The switch procedure from natural gas to syngas is defined and modelled. A series of non-reactive and reactive RANS simulations on a full-scale 3D model of the combustion chamber is then performed. The thermo-fluid dynamics inside its casing, the combustion regimes, the heat transfer across the liner walls as well as NOx emissions are evaluated. Results provide useful information on the operational problems associated to the fuel change and on how to define a successful fuel transfer procedure.
TOPICS: Fuels, Computer simulation, Combustion chambers, Syngas, Hydrogen, Natural gas, Methane, Reynolds-averaged Navier–Stokes equations, Switches, Thermofluids, Nitrogen oxides, Three-dimensional models, Emissions, Micro gas turbines, Carbon dioxide, Engineering simulation, Simulation, Dynamics (Mechanics), Heat transfer, Combustion
research-article  
Nicolo' Gatta, Mauro Venturini, Lucrezia Manservigi, Giuseppe Fabio Ceschini and Giovanni Bechini
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040736
This paper addresses the challenge of forecasting the future values of gas turbine measureable quantities. The final aim is the simulation of "virtual sensors" capable of producing statistically coherent measurements aimed at replacing anomalous observations discarded from the time series. Among the different available approaches, the Bayesian Forecasting Method (BFM) adopted in this paper uses the information held by a pool of observations as knowledge base to forecast the values at a future state. The BFM algorithm is applied in this paper to Siemens field data to assess its prediction capability, by considering two different approaches, i.e. single-step prediction (SSP) and multi-step prediction (MSP). While SSP predicts the next observation by using true data as base of knowledge, MSP uses previously predicted data as base of knowledge to perform the prediction of future time steps. The results show that BFM single-step average prediction error can be very low, when filtered field data are analyzed. On the contrary, the average prediction error achieved in case of BFM multi-step prediction is remarkably higher. To overcome this issue, the BFM single-step prediction scheme is also applied to clusters of time-wise averaged data. In this manner, an acceptable average prediction error can be achieved by considering clusters composed of 60 observations.
TOPICS: Time series, Errors, Sensors, Simulation, Algorithms, Gas turbines
research-article  
Xiao Han, Davide Laera, Aimee S. Morgans, Yuzhen Lin and Chih-Jen Sung
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040735
The present article reports experimental and numerical analyses of the macrostructures featured by a stratified swirling flame for varying stratification ratio (SR). The studies are performed with the Beihang Axial Swirler Independently-Stratified (BASIS) burner, a novel double-swirled full-scale burner developed at Beihang University. Experimentally, it is found that depending on the ratio between the equivalence ratios of the methane-air mixtures from the two swirlers, the flame stabilizes with three different shapes: attached V--flame, attached stratified flame and lifted flame. In order to better understand the mechanisms leading to the three macrostructures, Large Eddy Simulations (LES) are performed via the open source Computational Fluid Dynamics (CFD) software OpenFOAM using the incompressible solver ReactingFoam. Changing the SR, simulation results show good agreement with experimentally observed time-averaged flame shapes, demonstrating that the incompressible LES are able to fully characterize the different flame behaviours observed in stratified burners. When the LES account for heat loss from walls, they better capture the experimentally observed flame quenching in the outer shear layer. Finally, insights into the flame dynamics are provided by analysing probes located near the two separate streams.
TOPICS: Flames, Computational fluid dynamics, Shapes, Simulation results, Swirling flow, Large eddy simulation, Numerical analysis, Computer software, Dynamics (Mechanics), Shear (Mechanics), Quenching (Metalworking), Heat losses, Methane, Probes
research-article  
Berend Denkena, Arne Mücke, Tim Schumacher, Demian Langen and Thomas Hassel
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040738
The widespread adoption of blade integrated disks (blisks) made of titanium demands tailored re-generation processes to increase sustainability and economic efficiency. High standards regarding geometrical accuracy and functional properties as well as the unique characteristics of each type of damage complicate the repair. Thus, flexible and well-designed processes are necessary. Typically, material deposit is followed by a milling or grinding process to restore the original shape. Here, not only the individual repair processes have to be controlled, but also their interaction. For example, depending on the resulting microstructure of the welded seam, the re-contouring process needs to be adapted to minimize tool wear as well as shape deviations of the complex blade geometries. In this paper, the process chain for a patch repair is examined, consisting of a TIG welding process followed by 5-axis ball nose end milling. Conventional TIG as well as a modified TIG process producing a finer grain structure and enhanced mechanical properties of deposited material were investigated. Grain refinement was achieved by SiC particles added to the weld pool. Based on the characteristics of the fusion material and static stiffness of the component, a methodology is introduced to minimize shape deviation induced by the subsequent milling process. Special attention is given to tool orientation, which has a significant impact on the kinematics and resulting process forces during milling. An electromagnetic guided machine tool is used for compensation of workpiece deflection.
TOPICS: Maintenance, Disks, Blades, Milling, Shapes, Stiffness, Titanium, Damage, Deflection, Kinematics, Wear, Machine tools, Particulate matter, Grinding, Gas tungsten arc welding, Mechanical properties, Chain, Sustainability
research-article  
Alwin Förster, Lars Panning-von Scheidt and Jörg Wallaschek
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040740
Bladed Disks are subjected to different types of excitations, which cannot in any case be described in a deterministic manner. Fuzzy factors, such as slightly varying airflow or density fluctuation, can lead to an uncertain excitation in terms of amplitude and frequency, which has to be described by random variables. The computation of frictionally damped blades under random excitation becomes highly complex due to the presence of nonlinearities. Only a few publications are dedicated to this particular problem. Most of these deal with systems of only one or two degrees of freedom and use computational expensive methods, like finite element method (FEM) or finite differences method (FDM), to solve the determining differential equation. The stochastic stationary response of a mechanical system is characterized by the joint probability density function (JPDF), which is driven by the Fokker-Planck equation (FPE). Exact stationary solutions of the FPE only exist for a few classes of mechanical systems. This paper presents the application of a semi-analytical Galerkin-type method to a frictionally damped bladed disk under influence of gaussian white noise (GWN) excitation in order to calculate its stationary response. One of the main difficulties is the selection of a proper initial approximate solution, which is applicable as a weighting function. Comparing the presented results with those from the FDM, Monte-Carlo Simulation (MCS) as well as analytical solutions proves the applicability of the methodology.
TOPICS: Disks, Fokker-Planck equation, Random excitation, Excitation, Density, Finite element methods, Degrees of freedom, Differential equations, Air flow, Simulation, Probability, Blades, Computation, White noise
research-article  
Malte Merk, Camilo Silva, Wolfgang Polifke, Renaud Gaudron, Marco Gatti, Clement Mirat and Thierry Schuller
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040731
This study assesses and compares two alternative approaches to determine the acoustic scattering matrix of a premixed turbulent swirl combustor: 1) The acoustic scattering matrix coefficients are obtained directly from a compressible Large Eddy Simulation (LES). Specifically, the incoming and outgoing characteristic waves f and g extracted from the LES are used to determine the respective transmission and reflection coefficients via System Identification techniques. 2) The flame transfer function (FTF) is identified from LES time series data of upstream velocity and heat release rate. The transfer matrix of the reactive combustor is then derived by combining the FTF with the Rankine-Hugoniot relations across a compact heat source and a transfer matrix of the cold combustor, which is deduced from a linear network model. Linear algebraic transformation of the transfer matrix consequently yields the combustor scattering matrix. A cross-comparison study that includes comprehensive experimental data shows that both approaches successfully predict the scattering matrix of the reactive turbulent swirl combustor.
TOPICS: Turbulence, Acoustics, S-matrix theory, Combustion chambers, Analytical methods, Large eddy simulation, Heat, Algebra, Flames, Network models, Time series, Transfer functions, Reflectance, Waves
research-article  
Giulio Ghirardo, Carlo Di Giovine, Jonas P. Moeck and Mirko R. Bothien
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040743
Can-annular combustors consist of a set of independent cans, connected on the upstream side to the combustor plenum, and on the downstream side to the turbine inlet, where a transition duct links the round geometry of each can with the annular segment of the turbine inlet. Each transition duct is open on the sides towards the adjacent transition ducts, so that neighbouring cans are acoustically connected through a so called cross-talk open area. This theoretical, numerical and experimental work discusses the effect that this communication has on the thermoacoustic frequencies of the combustor. We show how this communication gives rise to axial and azimuthal modes, and that these correspond to particularly synchronised states of axial thermoacoustic oscillations in each individual can. We show that these combustors typically show clusters of thermoacoustic modes with very close frequencies and that a slight loss of rotational symmetry, e.g. a different acoustic response of certain cans, can lead to mode localization. We corroborate the predictions of azimuthal modes, clusters of eigenmodes and mode localization with experimental evidence.
TOPICS: Combustion chambers, Thermoacoustics, Ducts, Turbines, Acoustics, Oscillations, Geometry
research-article  
Matthias Huels, Lars Panning-von Scheidt and Jörg Wallaschek
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040732
Among the major concerns for high aspect-ratio turbine blades are forced and self-excited (flutter) vibrations which can cause failure by high-cycle fatigue. The introduction of friction damping in turbine blades, such as by coupling of adjacent blades via under platform dampers, can lead to a significant reduction of resonance amplitudes at critical operational conditions. In this paper, the influence of basic geometric blade design parameters onto the damped system response will be investigated to link design parameters with functional parameters like damper normal load, frequently used in nonlinear dynamic analysis. The shape of a simplified turbine blade is parameterized along with the under platform damper configuration. The airfoil is explicitly included into the parameterization in order to account for changes in blade mode shapes. For evaluation of the damped system response a reduced order model for non-linear friction damping is included into an automated 3D FEA tool-chain. Based on a design of experiments approach, the design space will be sampled and surrogate models are trained on the received dataset. Subsequently, the mean and interaction effects of the geometric design parameters onto the resonance amplitude and safety against high-cycle fatigue will be outlined. The HCF safety is found to be affected by strong secondary effects onto static and resonant vibratory stress levels. Applying an evolutionary optimization algorithm, it is shown that the optimum blade design with respect to minimum vibratory response can differ significantly from a blade designed toward maximum HCF safety.
TOPICS: Friction, Safety, Turbine blades, Design, Dampers, High cycle fatigue, Blades, Resonance, Damping, Stress, Flutter (Aerodynamics), Chain, Dynamic analysis, Finite element analysis, Vibration, Experimental design, Failure, Optimization algorithms, Shapes, Airfoils, Mode shapes
research-article  
Michael Palman, Boris Leizeronok and Dr. Beni Cukurel
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040734
The current work focuses on mission based evaluation of a novel engine architecture arising from the conversion of a micro turbojet to a micro turbofan via introduction of a variable speed fan and bypass nozzle. The solution significantly improves maximum thrust by 260%, reduces fuel consumption by as much as 60% through maintaining the core independently running at its optimum, and enables a wider operational range, all the meanwhile preserving a simple single spool configuration. Particularly, the introduction of a variable speed fan, enables real-time optimization for both high speed cruise and low speed loitering. In order to characterize the performance of the adaptive cycle engine with increased number of controls (engine speed, gear ratio, bypass opening), a component map based thermodynamic study is used to contrast it against other similar propulsion systems with incrementally reduced input variables. In following, a shortest path based optimization is conducted over the locally minimum fuel consumption operating points, based on a set of gradient driven connectivity constraints for changes in gear ratio and bypass nozzle area. The resultant state transition graphs provide global optimum for fuel consumption at a thrust range in a given altitude and Mach flight envelope. Then, the engine model is coupled to a flight mechanics solver supplied with a conceptual design for a representative multi-purpose UAV. Lastly, the associated mission benefits are demonstrated in surveillance and firefighting scenarios.
TOPICS: Engines, Cycles, Surveillance, Optimization, Turbofans, Fuel consumption, Flight, Thrust, Gears, Nozzles, Unmanned aerial vehicles, Conceptual design, Turbojets, Propulsion systems
research-article  
Andrew J. Provenza, Kirsten P. Duffy and Milind Bakhle
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040739
Boundary Layer Ingestion (BLI) is a propulsion technology being investigated at NASA by the Advanced Aircraft Transportation Technology (AATT) Program to facilitate a substantial reduction in aircraft fuel burn. In an attempt to experimentally demonstrate an increase in propulsive efficiency of a BLI engine, a first-of-its-kind sub-scale high-bypass ratio 22" titanium fan, designed to structurally withstand significant unsteady pressure loading caused by a heavily distorted axial air inflow, was built and then tested in the transonic section of the GRC 8'x6' Supersonic Wind Tunnel. The vibratory responses of a subset of fan blades were measured using strain gages placed in four different blade pressure side surface locations. Response highlights include a significant response of the blade's first resonance to engine order excitation below idle as the fan was spooled up and down. The fan fluttered at the design speed under off operating line, low flow conditions. This paper presents the blade vibration response characteristics over the operating range of the fan and compares them to predicted behaviors. It also provides an assessment of this distortion tolerant fan's (DTF) ability to withstand the harsh dynamic BLI environment over an entire design life of billions of load cycles at design speed.
TOPICS: Boundary layers, Design, Blades, Pressure, Engines, Aircraft, Resonance, Stress, Propulsion, Flow (Dynamics), Fuels, Transportation systems, Vibration, Cycles, Strain gages, Titanium, Wind tunnels, Inflow, NASA, Excitation
research-article  
Christian Kontermann, Henning Almstedt, Falk Mueller and Matthias Oechsner
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040733
Changes within the global energy market and a demand for a more flexible operation of gas- and steam-turbines lead to higher utilization of main components and raise the question how to deal with this challenge. One strategy to encounter this is to increase the accuracy of the lifetime assessment by quantifying and reducing conservatisms. At first the impact of considering a fracture mechanical notch support under creep-fatigue loading is studied by discussing the results of an extensive experimental program performed on notched round-bars under global strain control. A proposal how to consider this fracture mechanical notch support within a lifetime assessment is part of the discussion of the second part. Here, a theoretical FEM-based concept is introduced and validated by comparing the theoretical prediction with the results of the previously mentioned experimental study. Finally, the applicability of the developed and validated FEM-based procedure is demonstrated.
TOPICS: Fracture (Materials), Fracture (Process), Creep, Fatigue, Finite element methods, Finite element model, Steam turbines
research-article  
Carlos Xisto, Olivier Petit, Tomas Gronstedt and Anders Lundbladh
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040741
In the present paper, the synergistic combination of intercooling with pulsed detonation combustion is analyzed concerning its contribution to NOx and CO2 emissions. CO2 is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption and reducing engine weight and nacelle drag. A model predicting NOx generation per unit of fuel for pulsed detonation combustors, operating with jet-A fuel, is developed and integrated within Chalmers University's gas turbine simulation tool GESTPAN. The model is constructed using CFD data obtained for different combustor inlet pressure, temperature and equivalence ratio levels. The NOx model supports the quantification of the trade-off between CO2 and NOx emissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications.
TOPICS: Explosions, Engines, Carbon dioxide, Nitrogen oxides, Turbofans, Emissions, Fuels, Temperature, Combustion, Combustion chambers, Gas turbines, Computational fluid dynamics, Tradeoffs, Fuel consumption, Aircraft engines, Weight (Mass), Pressure, Drag (Fluid dynamics), Simulation
research-article  
Jing Yang and Luis San Andres
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040742
Most seal designs regard the inlet as a sharp edge. In actuality, a customary manufacturing process could produce a rounded inlet corner. Furthermore, after a period of operation, a sharp corner may wear out into a round section. To this date, bulk flow model (BFM) analyses rely on an unknown entrance pressure coefficient to deliver predictions for seals. This paper quantifies the influence of an inlet corner on the performance of a water lubricated smooth seal. Computational fluid dynamics (CFD) simulations apply to a seal with either a sharp edge or an inlet section with curvature radius rc varying from ¼Cr to 5Cr. Going from a sharp inlet to one with a small curvature rc = ¼Cr produces a ~20% decrease on the entrance pressure loss coefficient. Further CFD simulations show that rotor speed and pressure drop do not affect the entrance loss coefficient, while the inlet circumferential velocity does. In addition, CFD results for a shorter (half) length seal produce a very similar entrance loss coefficient. For the seal with a rounded edge (rc = 5Cr), both direct stiffness K and direct damping C decrease about 10% compared against the coefficients for the seal with a sharp edge. A BFM incorporates the CFD derived entrance loss coefficients and produces rotordynamic coefficients for the same operating conditions. The CFD and BFM predictions are in good agreement. In the end, the CFD analysis quantifies the entrance loss coefficient as a function of the inlet geometry for ready use in engineering BFM tools.
TOPICS: Pressure, Flow (Dynamics), Wear, Manufacturing, Simulation, Corners (Structural elements), Clearances (Engineering), Computational fluid dynamics, Damping, Engineering simulation, Pumps, Rotors, Geometry, Pressure drop, Stiffness, Water
research-article  
Scott Leask, Vincent McDonell and G. Scott Samuelsen
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040744
This work presents the atomization characteristics and dynamics of water-in-heptane (W/H) emulsions injected into a gaseous crossflow. W/H mixtures were tested while varying momentum flux ratios and aerodynamic Weber numbers. Different injector orifice diameters and orifice length-to-diameter ratios were used to test the generality of the results. The atomization properties of W/H mixtures were compared with properties of neat water and neat heptane to evaluate the effect of an emulsion on droplet sizing, cross-sectional stability and dispersion, and jet penetration depth. Liquid dynamics were extracted through analyzing instantaneous spray measurements and dynamic mode decomposition (DMD) on high-speed video recordings of the atomization processes. Correlations were proposed to establish preliminary relationships between fundamental spray processes and test conditions. These correlations allowed for emulsion behavior to be compared with neat liquid behavior. The use of emulsions induces greater spray instability than through using neat liquids, likely due to the difficulty in injecting a stable emulsion. Neat liquid correlations were produced and successfully predicted various spray measurements. These correlations, however, indicate that injector geometry has an effect on spray properties which need to be addressed independently. The emulsions are unable to adhere to the neat liquid correlations suggesting that an increased number of correlation terms are required to adequately predict emulsion behavior.
TOPICS: Dynamics (Mechanics), Emulsions, Sprays, Ejectors, Water, Heptane, Geometry, Momentum, Stability, Drops
research-article  
Alexander Avdonin and Wolfgang Polifke
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040745
Non-intrusive polynomial chaos expansion (NIPCE) is used to quantify the impact of uncertainties in operating conditions on the flame transfer function of a premixed laminar flame. NIPCE requires only a small number of system evaluations, so it can be applied in cases where a Monte Carlo simulation is unfeasible. We consider three uncertain operating parameters: inlet velocity, burner plate temperature, and equivalence ratio. The flame transfer function (FTF) is identified in terms of the finite impulse response from CFD simulations with broadband velocity excitation. NIPCE yields uncertainties in the FTF due to the uncertain operating conditions. For the chosen uncertain operating bounds, a second-order expansion is found to be sufficient to represent the resulting uncertainties in the FTF with good accuracy. The effect of each operating parameter on the FTF is studied using Sobol indices, i.e. a variance-based measure of sensitivity, which are computed from the NIPCE. It is observed that in the present case uncertainties in the finite impulse response as well as in the phase of the FTF are dominated by the equivalence-ratio uncertainty. For frequencies below 150 Hz, the uncertainty in the gain of the FTF is also attributable to the uncertainty in equivalence-ratio, but for higher frequencies the uncertainties in velocity and temperature dominate. At last, we adopt the polynomial approximation of the output quantity, provided by the NIPCE method, for further UQ studies with modified input uncertainties.
TOPICS: Transfer functions, Polynomials, Uncertainty, Chaos, Flames, Impulse (Physics), Temperature, Simulation, Computational fluid dynamics, Uncertainty quantification, Excitation, Polynomial approximation
research-article  
Tommaso Bacci, Tommaso Lenzi, Alessio Picchi, Lorenzo Mazzei and Dr. Bruno Facchini
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040714
Modern lean burn aero-engine combustors outflows are characterized by aggressive swirl fields, high turbulence intensities and strong hot streaks. In order to understand combustor-turbine interactions, it is mandatory to collect reliable experimental data at representative flow conditions. While the separated effects of temperature, swirl and turbulence on the first turbine stage have been widely investigated, reduced experimental data is available when it comes to consider all these factors together. An annular three-sector combustor simulator with fully cooled high pressure vanes has been installed at the THT Lab of University of Florence. The rig is equipped with three axial swirlers, effusion cooled liners and six film cooled high pressure vanes passages. In order to generate representative conditions, a heated mainstream passes though the axial swirlers of the combustor simulator, while the effusion cooled liners are fed by air at ambient temperature. The resulting flow field exiting from the combustor simulator and approaching the cooled vane can be considered representative of a modern Lean Burn aero engine combustor with swirl angles above ±50°, turbulence intensities up to about 28% and maximum-to-minimum temperature ratio of about 1.25. With the aim of investigating the hot streaks evolution through the cooled high pressure vane, the aerothermal field has been evaluated by means of a five hole probe equipped with a thermocouple and traversed upstream and downstream of the cascade.
TOPICS: Flow (Dynamics), High pressure (Physics), Combustion chambers, Outflow, Turbulence, Temperature, Turbines, Aircraft engines, Probes, Thermocouples, Temperature effects, Cascades (Fluid dynamics)
research-article  
Philippe Dagaut, Yuri Bedjanian, Guillaume Dayma, Fabrice Foucher, Benoit Grosselin, Emmanouil Romanias and Roya Shahla
J. Eng. Gas Turbines Power   doi: 10.1115/1.4040712
The combustion of conventional fuels (Diesel and Jet A-1) with 10-20% vol. oxygenated biofuels (ethanol, 1-butanol, methyl octanoate, rapeseed oil methyl ester, diethyl carbonate, tri(propylene glycol)methyl ether, i.e., CH3(OC3H6)3OH, and 2,5-dimethylfuran) and a synthetic paraffinic kerosene was studied. The experiments were performed using an atmospheric pressure laboratory premixed flame and a four-cylinder four-stroke Diesel engine operating at 1500 rpm. Soot samples from kerosene blends were collected above a premixed flame for analysis. Polyaromatic hydrocarbons (PAHs) were extracted from the soot samples. After fractioning, they were analyzed by high-pressure liquid chromatography (HPLC) with UV and fluorescence detectors. C1 to C8 carbonyl compounds were collected at the Diesel engine exhaust on 2,4-dinitrophenylhydrazine coated cartridges (DNPH) and analyzed by HPLC with UV detection. The data indicated that blending conventional fuels with biofuels has a significant impact on the emission of both carbonyl compounds and PAHs adsorbed on soot. The global concentration of 18 PAHs (1-methyl-naphthalene, 2-methyl-naphthalene, and the 16 US priority EPA PAHs) on soot was considerably lowered using oxygenated fuels, except 2,5-dimethylfuran. Conversely, the total carbonyl emission increased by oxygenated biofuels blending. Among them, ethanol and 1-butanol were found to increase considerably the emissions of carbonyl compounds.
TOPICS: Combustion, Fuels, Biofuel, Pollution, Emissions, Soot, Flames, Ethanol, Diesel engines, Ultraviolet radiation, Fluorescence, High pressure (Physics), Ethers (Class of compounds), Atmospheric pressure, Sensors, Ester, Cylinders, Diesel, Exhaust systems

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