1,720,982 research outputs found
Experimental tests of inhomogeneous hydrogen deflagrations in the presence of obstacles
No full textExplosion venting is a frequently used measure to mitigate the outcome of deflagration in closed environments. Despite the effort to improve engineering formulas and CFD tools used to predict the vent area needed to meet the desired enclosure protection, work has still to be done to reliably predict the outcome of a vented gas explosion. Blind-prediction exercises recently published by the HYSEA project show a large spread in the predictions by engineering models, including semi-empirical correlations and computational fluid dynamics (CFD) tools. University of Pisa performed experimental tests in a 25 m3 facility in inhomogeneous conditions and with the presence of simple obstacles constituted by plates bolted to HEB beams. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated with different blockage ratio and repeated obstacles rows. Description of the experimental setup includes all the details deemed necessary to reproduce the phenomenon with a CFD tool
The effect of venting process on the progress of a vented deflagration
No full textVented deflagrations are one of the most challenging phenomenon to be replicated numerically in order to predict its resulting pressure time history. As a matter of fact a number of different phenomena can contribute to modify the burning velocity of a gas mixture undergoing a deflagration, especially when the flame velocity is considerably lower than the speed of sound. In these conditions acceleration generated by both the flow field induced by the expanding flame and from discontinuities, as the vent opening and the venting of the combustion products, affect the burning velocity and the burning behavior of the flame. In particular the phenomena affecting the pressure time history of a deflagration after the flame front reaches the vent area, such as flame acoustic interaction and local pressure peaks, seem to be closely related to a change in the burning behavior induced by the venting process. Flame acoustic interaction and local pressure peaks arise as a consequence of the change in the burning behavior of the flame. This paper discuss the analysis of the video recording of the flame front produced during the TP experimental campaign, performed by UNIPI in the project HySEA, to describe qualitatively the contribution of the generated flow field in a vented deflagration and its influence in the peaks of the pressure-time history
Hydrogen release and atmospheric dispersion: experimental studies and comparison with parametric simulations
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Homogeneous hydrogen deflagrations in small scale enclosure. Experimental results.
Full text linkUniversity of Pisa performed experimental tests in a 1m3 facility, which shape and dimensions resemble a gas
cabinet, for the HySEA project, founded by the Fuel Cells and Hydrogen 2 Joint Undertaking with the aim to
conduct pre-normative research on vented deflagrations in real-life enclosures and containers used for hydrogen
energy applications, in order to generate experimental data of high quality. The test facility, named Small Scale
Enclosure (SSE), had a vent area of 0,42m2 which location could be varied, namely on the top or in front of the
facility, while different types of vent were investigated. Three different ignition location were investigated as
well, and the range of Hydrogen concentration ranged between 10 and 18% vol. This paper is aimed to
summarize the main characteristics of the experimental campaign as well as to present its results
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Small scale experiments and Fe model validation of structural response during hydrogen vented deflagrations
No full textUniversity of Pisa (UNIPI) conducted a series of vented deflagration tests at B. Guerrini Laboratory. The tests were part of the experimental campaign performed by UNIPI for the European HySEA project (Hydrogen Safety for Energy Applications). Experiments included homogeneous hydrogen-air mixture contained in an about 1 m 3 enclosure, called SSE (Small Scale Enclosure). The mixture concentration was variable between 10% and 18% vol. During the deflagrations, structural response was investigated by measuring the displacement of a test plate. The collected data were used to validate the FE model developed by IMPETUS Afea. In this paper experimental facility, displacement measurement system and FE model are briefly described, then comparison between experimental data and simulation results is discussed
Small scale experiments and Fe model validation of structural response during hydrogen vented deflagrations
No full textUniversity of Pisa (UNIPI) conducted a series of vented deflagration tests at B. Guerrini Laboratory. The tests were part of the experimental campaign performed by UNIPI for the European HySEA project (Hydrogen Safety for Energy Applications). Experiments included homogeneous hydrogen-air mixture contained in an about 1 m3 enclosure, called SSE (Small Scale Enclosure). The mixture concentration was variable between 10% and 18% vol. During the deflagrations, structural response was investigated by measuring the displacement of a test plate. The collected data were used to validate the FE model developed by IMPETUS Afea. In this paper experimental facility, displacement measurement system and FE model are briefly described, then comparison between experimental data and simulation results is discussed
- …
