•Numerical investigation of an industrial gas turbine lean premixed burner through a high-fidelity CFD approach.•Validation of the numerical setup through a direct comparison with experimental ...data.•Assessment of the flame shape prediction of two enhanced versions of the FGM and ATF combustion models.•Remarkable accuracy in predicting the flame topology exhibited by both models.•Assessment of both turbulent combustion models in supporting burner design phase.
In the pursuit of decarbonization, the reduction of greenhouse gas emissions from power generation through gas turbine (GT) engines plays a crucial role in the whole industrial sector. As industries strive to transition towards cleaner energy sources, the design and optimization of novel GT burners require a deep comprehension of the complex interaction between fluid dynamics and combustion processes embedded within the system. Computational Fluid Dynamics (CFD) plays a pivotal role in these processes by providing valuable insights into the complex flow patterns, flame topology, and stability limits within the combustor. Concurrently, the burner design phase necessitates a considerable number of simulations to ascertain flame stability limits under various burner designs and operating conditions. Therefore, it is imperative to control computational costs while ensuring a high level of accuracy. The present work is focused on a comprehensive comparative analysis of two widely employed turbulent combustion closure models: the Flamelet Generated Manifold (FGM) and the Artificially Thickened Flame (ATF). Both models utilize extended versions with specific modifications aimed at effectively addressing their respective limitations. The investigation is performed through a Large Eddy Simulation (LES) based CFD analysis within the context of a lean premixed burner designed by Baker Hughes and operated with methane at atmospheric pressure. The primary benchmark for numerical validation will be provided by detailed chemiluminescence images from a test campaign conducted by the University of Florence, thereby yielding valuable insights into flame topology and positioning. Furthermore, potential disparities in the flow field and fuel concentration at the burner exit between the two models will be revealed.
A study of benthic foraminifera was carried out in sediment samples collected from the central Adriatic coast of Italy, near the Ancona harbour and the Falconara Marittima oil refinery, in order to ...validate and support their use as bioindicators of ecosystem quality. On the basis of a principal component analysis (PCA), three biotopes (following the bathymetric gradient) have been documented, showing that the distribution pattern of benthic foraminifera is principally related to riverine inputs, organic matter contents at the seafloor, and sediment grain size. We observed higher abundances of opportunistic, low-oxygen tolerant taxa along the coastline, thus being representative of polluted environmental conditions. Near the Falconara Marittima oil refinery, the microfaunal assemblages is characterized by the absence of living specimens and by a low diversity associated with the dominance of opportunistic species. At this site, aberrant tests were also found. The data point out that Ammonia parkinsoniana and Quinqueloculina seem to be the most sensitive taxa and can be considered as good bioindicators of environmental stress in this area. This study confirms that faunal composition and morphology of benthic foraminifera respond to human-induced environmental perturbations, making their study potentially useful for biomonitoring in coastal-marine areas.
The mid-Cenomanian Event: prelude to OAE 2 Coccioni, R.; Galeotti, S.
Palaeogeography, palaeoclimatology, palaeoecology,
01/2003, Letnik:
190, Številka:
C
Journal Article
Recenzirano
A detailed synthesis of litho- and biostratigraphic investigations of the Cenomanian pelagic limestones of the Scaglia Bianca Formation in the Umbria–Marche Basin shows that the Bonarelli Level, ...which is the regional sedimentary expression of the OAE 2, represents the climax of a ∼2 Myr-long cycle of black shale deposition that began in the mid-Cenomanian planktonic foraminiferal
Rotalipora cushmani Zone. This long-term cycle began with a prominent short-term event, named mid-Cenomanian Event (MCE), which is associated with several changes in the biotic and abiotic records. In particular, a comparison of the available litho-, bio-, and chemostratigraphic data from the Umbria–Marche Basin allows recognition of the MCE based on: (a) a significant change in the sedimentary and tectonic regimes; (b) a reorganisation of planktonic foraminiferal assemblages; (c) a major change in benthic foraminifera; (d) a major turnover in the radiolarian assemblages; (e) a 0.7‰ positive shift in the carbon isotope values; and (f) a positive shift of carbonate Sr/Ca ratio. Moreover, the MCE is preceded (∼400 kyr) by a short-term 0.5‰ negative excursion in the oxygen isotope record. The above mentioned changes in carbon and oxygen isotope values can be confidently correlated over different basins and oceans and seem to occur in correspondence with a major sea-level fall. These lines of evidence define the MCE as an outstanding event associated with large-scale changes in the oceanic structure and palaeoclimate. The MCE and the subsequent cyclical deposition of organic-rich beds serve as a case study to better understand differences and similarities between Mesozoic black shales and Cenozoic sapropels and related palaeoceanographic changes controlled by orbital climate cycles.
Pion–Muon separation with a RICH prototype for the NA62 experiment Angelucci, B.; Anzivino, G.; Avanzini, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2010, Letnik:
621, Številka:
1
Journal Article
Recenzirano
The NA62 experiment at CERN, aimed to measure
K
+
→
π
+
ν
ν
¯
branching fraction (O(10
−10)), relies on a Neon based RICH detector for
π
/
μ
separation, time measurement and level 0 trigger. The ...experimental requirements for this detector are: a muon contamination in pion samples lower than 5×10
−3 in the momentum range 15–35
GeV/
c and a time resolution on the charged track better than 100
ps. A prototype of such a detector was built and tested in 2009; it consists of a full length (
≈
18
m
) Ne filled vessel equipped with a spherical mirror and 414 PMs on its focal plane, located about 17
m upstream of the mirror. This prototype was tested at CERN SPS on a positive hadron beam, in the required momentum range, to measure the
π
/
μ
separation and to confirm the time resolution obtained with a previous prototype; the
μ
misidentification probability is about 0.7% and the time resolution is better than 100
ps in the whole momentum range.
The CDF Silicon Vertex Trigger Ashmanskas, Bill; Barchiesi, A.; Bardi, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2004, Letnik:
518, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The Collider Detector at Fermilab (CDF) experiment's Silicon Vertex Trigger (SVT) is a system of 150 custom 9U VME boards that reconstructs axial tracks in the CDF silicon strip detector in a
15
μs
...pipeline. SVT's
35
μm
impact parameter resolution enables CDF's Level 2 trigger to distinguish primary and secondary particles, and hence to collect large samples of hadronic bottom and charm decays. We review some of SVT's key design features. Speed is achieved with custom VLSI pattern recognition, linearized track fitting, pipelining, and parallel processing. Testing and reliability are aided by built-in logic state analysis and test-data sourcing at each board's input and output, a common interboard data link, and a universal “Merger” board for data fan-in/fan-out. Speed and adaptability are enhanced by use of modern FPGAs.
The trigger and DAQ system for the NA62 experiment Avanzini, C.; Collazuol, G.; Galeotti, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2010, Letnik:
623, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The main goal of the NA62 experiment is to measure the branching ratio of the K+→π+νν¯ decay, collecting O(100) events in two years of data taking. Efficient online selection of interesting events ...and loss-less readout at high rate will be key issues for such experiment. An integrated trigger and data acquisition system has been designed. Only the very first trigger stage will be implemented in hardware, in order to reduce the total rate for the software levels on PC farms. Readout uniformity among different subdetectors and scalability were taken into account in the architecture design.
The implementation of Exhaust Gas Recirculation (EGR) in gas turbines can become an interesting opportunity to enhance the coupling between natural gas fueled GT power plants and Carbon Capture and ...Storage (CCS) systems. In fact, as the CO2 content of the incoming flow increases, performance of CCS units improves in terms of efficiency and compactness. As a drawback, the oxygen content available for the combustion reaction decreases, making the combustion process challenging in terms of flame stability and therefore engine operability. This work presents the results of an experimental campaign investigating the behavior of an industrial burner operated with simulated EGR. For the investigation EGR is recreated by diluting standard air with CO2. The burner is operated at ambient pressure in a single sector optical test rig with tubular quartz liner, using natural gas as fuel. The effect of fuel split between premix and pilot line was investigated along with the lack of oxygen caused by EGR. OH* chemiluminescence imaging was employed to study flame topology, and exhaust gas analysis was performed. Emission measurements showed significant NOx reduction, but at the same time as expected CO levels increased remarkably under EGR-like conditions. Additionally, CO2 addition is found to trigger thermoacoustic instabilities in certain conditions, limiting the EGR operability window.
•Industrial GT burner was studied experimentally at ambient pressure under simulated EGR conditions.•With simulated EGR the reaction zone becomes widespread and flame length significantly increases especially for higher premixed cases.•Emission measurements revealed very high and progressively increasing CO levels under EGR-like conditions.•NOx emissions benefit from the lower oxygen content, and the dependency on fuel split becomes marginal.•Simulated EGR alters the flame dynamic behavior, with the onset of thermoacoustic instabilities up to a certain threshold level.
We report evidence for Milankovitch cycles discovered in Middle Permian strata of the fluvial Abrahamskraal formation, lower Beaufort Group, in Karoo Basin of the Northern Cape Province, South ...Africa. Statistical analyses of ranked lithologies and of major element oxides have been used to obtain clusters of elements that capture lithological variations and reflect changes of the sedimentary environment through time. Spectral analysis of these elemental statistical groups reveal significant meter-scale sedimentary cycles of 67 m, 17.5 m, 5.9 m and 3.5–2.8 m, which can be interpreted as the sedimentary expression of astronomical forcing, based on the available estimate of sedimentation rate. The identified periods of short-eccentricity, precession and obliquity show a good match with those predicted for Middle Permian times, providing a data-based validation of the astronomical theory. Cycle counting integrated with available UPb dating, provides a cyclochronological calibration for Wordian normal magnetozones and, combined with radiometric ages, indicates an age of 266.5 ± 0.26 Ma for the end of Kiaman superchron. Recognition of the orbitally driven sedimentation in Gondwana supercontinent suggest a global extension of astronomical influence of Permian climate and confirms empirical knowledge of Earth's astronomical parameters before 260 million years ago. The new data demonstrate a rare case of astronomically paced cyclicity in fluvial deposits and a unique cyclostratigraphic record of the Middle Permian Gondwana supercontinent whose sedimentation reflects orbitally-paced precipitation changes.
•First report of Milankovitch cycles in Middle Permian strata in the interior of Gondwana supercontinent.•Fluvial sedimentation controlled by orbitally-paced precipitation changes.•Validate empirical knowledge of Earth's astronomical parameters before 260 Ma.•Combined astronomical and radiometric age of the end of the Kiaman superchron.•Cyclostratigraphic calibration of the length of GU1n/r (Wordian) magnetochrons.
ANTARES: The first undersea neutrino telescope Ageron, M.; Anghinolfi, M.; Ardid, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2011, Letnik:
656, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The ANTARES Neutrino Telescope was completed in May 2008 and is the first operational Neutrino Telescope in the Mediterranean Sea. The main purpose of the detector is to perform neutrino astronomy ...and the apparatus also offers facilities for marine and Earth sciences. This paper describes the design, the construction and the installation of the telescope in the deep sea, offshore from Toulon in France. An illustration of the detector performance is given.
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