1,731 research outputs found
Evaluation of NOx Emissions Associated to Non-Premixed Combustion of H2/Natural Gas Blends in a 40MW Heavy-Duty Gas Turbine
No full textThe tightening in the international regulations is leading the energy production sector towards the usage of hydrogen, which is a zero-carbon energy carrier. In the field of gas turbine lifetime extension, a non-premixed approach including hydrogen blending with conventional fuels is the most promising. However, high-temperature spots might occur, thus increasing thermo-mechanical stresses and NOx emissions. Therefore, a reliable evaluation of the impact of hydrogen blends in combustors characterized by non-premixed flames is necessary. In the present work, a 40MW heavy-duty multi-can combustor belonging to EthosEnergy is investigated by means of steady, reactive simulations by using the ANSYS® FLUENT® solver. The combustor geometry is simplified by removing the casing volume, being the flow split among the holes already available. Such simplification allows for paying major attention to the chemical kinetics thanks to the use of the extended reaction mechanism for natural gas developed by NUI Galway. Simulations include the assessment of the natural gas base load configuration together with hydrogen blends up to 50% in volume, while maintaining unaltered the turbine inlet temperature. The obtained data provide some retrofitting guidelines in the field of hydrogen usage in non-premixed combustion and prove for a modified temperature field in the combustor core and close to the basket. A linear increase in NOx emission is also associated to hydrogen addition, thus suggesting the need for NOx abatement technologies (e.g., water injection)
Evaluation of Nox Emissions Associated to Non-Premixed Combustion of H2/Natural Gas Blends in a 40 MW Heavy-Duty Gas Turbine
No full textThe tightening in the international regulations is leading the energy production sector toward the usage of hydrogen, which is a zero-carbon energy carrier. In the field of gas turbine lifetime extension, a nonpremixed approach including hydrogen blending with conventional fuels is the most promising. However, high-temperature spots might occur, thus increasing thermo-mechanical stresses and NOx emissions. Therefore, a reliable evaluation of the impact of hydrogen blends in combustors characterized by nonpremixed flames is necessary. In the present work, a 40 MW heavy-duty multican combustor belonging to EthosEnergy is investigated by means of steady, reactive simulations by using the ANSYS® FLUENT® solver. The combustor geometry is simplified by removing the casing volume, being the flow split among the holes already available. Such simplification allows for paying major attention to the chemical kinetics thanks to the use of the extended reaction mechanism for natural gas developed by National University of Ireland Galway. Simulations include the assessment of the natural gas base load configuration together with hydrogen blends up to 50% in volume, while maintaining unaltered the turbine inlet temperature (TIT). The obtained data provide some retrofitting guidelines in the field of hydrogen usage in nonpremixed combustion and prove for a modified temperature field in the combustor core and close to the basket. A linear increase in NOx emission is also associated with hydrogen addition, thus suggesting the need for NOx abatement technologies (e.g., water injection)
Recuerdos de Massimo.
No full textEl presente ensayo recuerda la rica relación personal e intelectual entre Massimo Pavarini e Iñaki Rivera Beiras desde que el segundo conoció siendo muy joven a Pavarini. En ese sentido, el trabajo recuerda los inicios de su fecunda relación en la ciudad de Bologna cuando Iñaki Rivera acudía a presentar a Massimo Pavarini los desarrollos de lo que sería su tesis doctoral. Las contribuciones de Pavarini al proceso de aprendizaje de Rivera, en el terreno de una epistemología crítica en la penología contemporánea, son analizados como un homenaje a la memoria y a la obra del autor italiano, tras su fallecimiento en septiembre de 2015.This paper recalls the rich personal and intellectual relationship between Massimo Pavarini and Iñaki Rivera Beiras. In that sense , the work recalls the beginning of his fruitful relationship in the city of Bologna when Iñaki Rivera came to present Massimo Pavarini’ developments in what would be his PhD thesis. Pavarini contributions to the learning process of Rivera, on the ground of a critical epistemology in contemporary penology , are analyzed as a tribute to the memory and to the work of Italian author, after his death in September 2015 .El presente ensayo recuerda la rica relación personal e intelectual entre Massimo Pavarini e Iñaki Rivera Beiras desde que el segundo conoció siendo muy joven a Pavarini. En ese sentido, el trabajo recuerda los inicios de su fecunda relación en la ciudad de Bologna cuando Iñaki Rivera acudía a presentar a Massimo Pavarini los desarrollos de lo que sería su tesis doctoral. Las contribuciones de Pavarini al proceso de aprendizaje de Rivera, en el terreno de una epistemología crítica en la penología contemporánea, son analizados como un homenaje a la memoria y a la obra del autor italiano, tras su fallecimiento en septiembre de 2015
Conjugate Heat Transfer Analysis of the Aero-Thermal Impact of Different Feeding Geometries for Internal Cooling in Lifetime Extension Processes for Heavy-Duty Gas Turbines
No full textRegulations from the European Union move towards a constant reduction of pollutant emissions to match the single-digit goal by 2050. Original equipment manufacturers propose newly designed components for the lifetime extension ofgGas turbines that both reduce emissions and allow for increasing thermodynamic performance by redesigning turbine cooling geometries and optimizing secondary air systems. The optimal design of internal cooling geometries allows for reducing both blade metal temperature and coolant mass-flow rates. In the present study, four different geometries of the region upstream from the blade’s internal cooling channels are investigated by using computational fluid dynamics with a conjugate heat transfer approach. The baseline configuration is compared to solutions that include turbulators, vanes, and a diffuser-like shapes. The impact of each solution on the blade metal temperature is thoroughly analysed. The diffuser-like solution allows for a more uniform distribution of the coolant and may reduce the metal temperature by 30% in the central part of the blade. There are also regions where the metal temperature increases up to 15%, thus requiring a specific thermal fatigue analysis. Eventually, the non-negligible impact of the coolant flow purged in the tip clearance region on the generation of the tip leakage vortex is described
Combustion Characterization in a Diffusive Gas Turbine Burner for Hydrogen-Compliant Applications
No full textThe target of net-zero emissions set by the 2015 Paris Agreement has strongly commissioned the energy production sector to promote decarbonization, renewable sources exploitation, and systems efficiency. In this framework, the utilization of hydrogen as a long-term energy carrier has great potential. This paper is concerned with the combustion characterization in a non-premixed gas turbine burner, originally designed for natural gas, when it is fed with NG-H2 blends featuring hydrogen content from 0 to 50% in volume. The final aim is to retrofit a 40 MW gas turbine. Starting from the operational data of the engine, a CFD model of the steady-state combustion process has been developed, with reference to the base load NG conditions, by reducing the fuel mass-flow rate by up to 17% to target the baseline turbine inlet temperature. When the fuel is blended with hydrogen, for a given temperature at turbine inlet, an increase in the peak temperature up to 800 K is obtained, if no countermeasures are taken. Furthermore, the flame results are more intense and closer to the injector in the case of hydrogen blending. The results of this work hint at the necessity of carefully analyzing the possible NOx compensation strategies, as well as the increased thermal stresses on the injector
Predoni a casa nostra e il geografo solidale: Massimo Quaini tra terra e acqua
No full textIn accordance with the main goals of this collection of essays in honour of Massimo Quaini, the text focuses on a peculiar character of the Ligurian geographer’s sensibility, his attention to landscape protectionresearch activity developed in the context of the humanistic geography. Starting from a personal narrative based on his own reminiscences and neglected memories, the author tries to shed light on the relationships between civil commitment and cultural reflection which characterize environmental sensitivity, bringing together his interests with Quaini’s emotional geographies. Finally, some of Quaini’s everyday practicalities are highlighted as the easiest doorway to improve the cognitive procedures of cultural geography
Is Felix Salten the author of the Mutzenbacher novel (1906)? Yes and no
No full textJosefine Mutzenbacher oder die Geschichte einer Wienerischen Dirne von ihr selbst erzählt, published in Vienna in 1906, represents one of the most fascinating cases of attribution of authorship in German literature. Although Josefine Mutzenbacher is usually attributed to Felix Salten, the author of the world-famous Bambi (1923), the novel’s authorship has never been confirmed, and many other candidates have been named as potential authors. Among them is Arthur Schnitzler, who published Reigen, a cycle of amorous adventures in Viennese society, in 1903. Some scholars, instead, have attributed the novel to such lesser-known writers as Ernst Klein and Willi Handl. The controversy surrounding the authorship of Josefine Mutzenbacher was the starting point for our stylometric analyses, and our results help to answer some unresolved questions in a debate that has lasted for more than 100 years. The analyses were performed using the R package Stylo, which enables an efficient application of Burrows’ Delta and its variants. Focusing on both the entire text and on the final pages, two different types of analysis were carried out: one combines 1200 different stylometric methods to compare the candidate authors Salten, Schnitzler, Bahr, Altenberg, Hofmannsthal, Klein and Handl; the other verifies the attribution using the ‘impostors’ method. The results show that the most probable author is Felix Salten, while none of the candidates could be identified as the author of the final pages, confirming the hypothesis that the text was left unfinished by Salten and completed by an as-yet-unidentified ghost-writer
Plastid Genotyping Reveals the Uniformity of Cytoplasmic Male Sterile-T Maize Cytoplasms
No full textCytoplasmic male-sterile (CMS) lines in maize (Zea mays) have been classified by their response to specific restorer genes into three categories: cms-C, cms-S, and cms-T. A mitochondrial genome representing each of the CMS cytotypes has been sequenced, and male sterility in the cms-S and cms-T cytotypes is linked to chimeric mitochondrial genes. To identify markers for plastid genotyping, we sequenced the plastid genomes of three fertile maize lines (B37, B73, and A188) and the B37 cms-C, cms-S, and cms-T cytoplasmic substitution lines. We found that the plastid genomes of B37 and B73 lines are identical. Furthermore, the fertile and CMS plastid genomes are conserved, differing only by zero to three single-nucleotide polymorphisms (SNPs) in coding regions and by eight to 22 SNPs and 10 to 21 short insertions/deletions in noncoding regions. To gain insight into the origin and transmission of the cms-T trait, we identified three SNPs unique to the cms-T plastids and tested the three diagnostic SNPs in 27 cms-T lines, representing the HA, I, Q, RS, and T male-sterile cytoplasms. We report that each of the tested 27 cms-T group accessions have the same three diagnostic plastid SNPs, indicating a single origin and maternal cotransmission of the cms-T mitochondria and plastids to the seed progeny. Our data exclude exceptional pollen transmission of organelles or multiple horizontal gene transfer events as the source of the mitochondrial urf13-T (unidentified reading frame encoding 13-kD cms-T protein) gene in the cms-T cytoplasms. Plastid genotyping enables a reassessment of the evolutionary relationships of cytoplasms in cultivated maize.Peer reviewe
A cidade, de Massimo Cacciari
No full textThis review presents a summary of the series of seminars presented by Massimo Cacciari at the Centro Sant´Apollinare de Fiesole, transcribed and edited by Tonino Rasuto. The work, entitled The city, brings reflections on what the author understands as the origin of urban configurations, more precisely what he classifies as the post-metropolis, the city-territory, which has its formation linked to the principles of Greek polis and of the Roman civitas. Finally, the author defines the potential of place and the geography of events, based on a methodological path of understanding the phenomena that were able to reframe the meaning of the city for the human being.Apresenta-se nesta resenha, uma síntese da série de seminários apresentados por Massimo Cacciari no Centro Sant´Apollinare de Fiesole, transcrita e editada por Tonino Rasuto. A obra, de título A cidade, traz reflexões acerca do que o autor entende como a origem das configurações urbanas, mais precisamente o que classifica como a pós-metrópole, a cidade-território, que tem sua formação ligada aos princípios da pólis grega e da civitas romana. Por fim, o autor define o potencial de lugar e da geografia de acontecimentos, a partir de um caminho metodológico de entendimentos dos fenômenos que foram capazes de ressignificar o sentido de cidade para o ser humano
Calcolo di stabilità della cupola del Teatro massimo di Palermo /
No full textMode of access: Internet.Bound in original printed wrappers; inscribed to G. Pini by the author on front wrapper
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