1,720,978 research outputs found
Conceptual Design of a Hydrogen-Propelled Aircraft with Distributed Electric Propulsion
No full textThe growing interest in environmental sustainability motivates the search for disruptive technologies and concepts. However, the lack of conceptual design methods capable of capturing the effects of new propulsive technologies is the main obstacle, often due to the absence of industrial data to support research. In this context, the Clean Sky 2 ELICA (ELectric Innovative Commuter Aircraft) project aims to fill this gap, supporting research with industrial expertise and exploiting a 19-seat commuter aircraft as a technological test bed. This paper aims to present the main results obtained in the investigation of the potential of a full-electric propulsion entirely based on fuel cell systems. After an overview of the main propulsion system modeling techniques used to pursue the objective, three different configurations will be compared, each with a different powerplant, aerodynamic characteristics and weights. The comparison will allow to highlight the real benefits of the aero-propulsive interaction, including effects impossible to quantify except with an approach based on flight mission simulation
Conceptual design of commuter aircraft including distributed electric propulsion
No full textA comprehensive developed conceptual design and analysis tool is here employed in the design of hybrid electric 19 passenger’s commuter aircraft. Particular attention is payed to the regulation under which aircraft must be certified. The sizing activity accounts for the aero-propulsive interactions when distributed electric propulsion is present. Output of this activity are the energetic requirements and the mass breakdown, by combining the free choice of the designer with aviation regulations and requirements. The application here presented provides parametric studies based on different operating combinations of distributed electric propulsion and e-storage. The aim of the present work is the identification of a design range which would make the choice of the new technologies profitable. The most promising result is a full-electric concept having 16 distributed propellers and designed for a flight mission of 200 nmi certifiable under FAR-23 (or CS-23) regulation
TECHNOLOGY ROADMAP AND CONCEPTUAL DESIGN OF HYBRID AND ELECTRIC CONFIGURATIONS IN THE COMMUTER CLASS
Full text linkThe growing sensitivity to the problem of sustainability requires a rethinking of how aviation is typically conceived by modern society. The aim of the research today must be to analyze the feasibility of disruptive solutions, which drastically reduce consumption and make it possible to meet the growing demand in the commercial aviation sector. The current level of technological maturity does not allow direct implementation on large commercial aircraft, which are responsible for most of the emissions from aviation. In this context, the Clean Sky 2 ELICA project aims to trace a technological roadmap towards green aviation, using the Small Air Transport as a test bed. Two different 19-seat commuter aircraft are presented in this work. The first one, with entry into service in 2025, presents a hybrid-electric architecture with batteries. The second configuration, with entry into service in 2035, is entirely propelled with hydrogen fuel cells, allowing the direct emissions of carbon and nitrogen oxides to be totally eliminated. Both configurations benefit from distributed electric propulsio
Performance calculation for hybrid-electric aircraft integrating aero-propulsive interactions
No full textThe potential benefits of hybrid-electric or full-electric propulsion have led to an increased interest in this topic over the past decade. Hence the need to develop modern and innovative methods to analyze the performance of aircraft with unconventional propulsion systems. The purpose of this paper is to describe and apply a simulation-based algorithm integrating aeropropulsive effects for the mission analysis of conventional, hybrid-electric, and full-electric aircraft. The method composes the analysis toolbox of the aforementioned software, HEAD (Hybrid-Electric Aircraft Designer), developed by the DAF Research Group. Analysis toolbox has to perform a detailed mission simulation of a generic airplane. The proposed application deals with the evaluation of the effects on performance that wingtip-mounted propellers and distributed electric propulsion on regional turboprop category. The reference aircraft is similar to an ATR-42
Powertrain Model Improvement for Hybrid-Electric Regional Aircraft
No full textThis paper deals with the definition of an improved powertrain model for hybrid-electric aircraft. It is well known that powertrain equations are one of the most convenient tools for modelling the propulsion system at aircraft level, when it comes to hybrid architectures characterized by more than a single propulsive source. However, for a reliable implementation of a robust optimization algorithm for the hybridization parameters, the designer should consider some singularity points related to certain non-physical configurations depending on the operating mode. In this work, singularities are firstly identified by analyzing the operating modes, then a solving strategy is reported. Another crucial aspect is the correct design and simulation of battery behavior. In a broader perspective, the high-level objective of the activities related to powertrain model is to assess a possible fuel saving for regional turboprops using e-storage units as secondary power source. In this respect, preliminary results in terms of flight performance referred to a regional aircraft similar to ATR42 are presented and discussed. The authors conclude that a block fuel saving up to 51% for the typical mission is possible with a battery specific energy of 500 Wh/kg and when the benefits of aero-propulsive interaction are fully exploited
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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