1,720,958 research outputs found
Innovation, automation and optimization in the aero design for aeronautical turbines
No full textIn the framework of civil air transportation, the design of turbomachinery components for modern aeronautical engines involves many tough technical issues. In fact, the increasing request for performance, durability, reliability and safety, reducing at the same the production times and design costs, emissions and fuel consumption, is pushing the traditional Turbofan architecture towards its limit. Levering on past experience and legacy is not sufficient for the next generation of engines, therefore the study and introduction of innovative features and technologies is essential. Nevertheless, those innovations must be proven to be effective, initially by a numerical point of view, then experimentally and on-the-field, facing harsh engineering challenges. This Thesis activity, in collaboration with Avio Aero company, presents an innovative vision for the aerodynamic Design System (DS) of one of the most stressed components: the Low Pressure Turbine (LPT) module. The proposed DS shows highly multi-disciplinary interactions and a deep integration with the Computational Fluid Dynamic (CFD). Three key aspects characterize this vision: innovation, automation and optimization. Some innovative features are studied and implemented, especially during the first Concept Design (CD) phase at pitch-line level. In particular, a deep revision of the classic correlations for aerodynamic losses is addressed by a novel conception. This study led to two contributions in international conferences (EASN [Ampellio et al., 2012] and ASME [Ampellio et al., 2013b]). Basically, the formulation of such loss models and the relative coefficients are rearranged and tuned following a CFD-based approach, in order to better fit the fully integrated vision belonging to the proposed DS. The CFD integration is in fact merged at any level, from the concept to details, resulting in a successful strategy to move very quickly the LPT assessment from 1D to 3D. The reliability of the innovative DS as a whole is guaranteed by the development of a dedicated all-inclusive, user-friendly, error-proof, and, above all, highly automated platform, able to efficiently drive the design towards the specific pursued goals with simplicity. Besides, the optimization of turbine modules is a fundamental but difficult step, since it takes into account a huge number of variables, constraints, objectives and parameters. Different optimization methods are suited to the different problems faced during the aero design of a turbomachinery. As a consequence, many algorithms have to be embedded into the DS with cross-functional attitudes, in order to provide the best compromise solution in any situation. In general, the optimization environment for aeronautical turbines is complex and strongly based on time-consuming CFD runs, especially when it comes to Preliminary and Detailed Design (PD, DD). Then, efficient strategies specifically dedicated to expensive simulation-based problems must be adopted, with the aim at minimizing the number of analyses required to solve the problem. A discussion about applied and simulation-based numerical optimization was exposed in a Seminar held at Politecnico di Torino [Ampellio, 2013] and a large part of this dissertation will be focused on the same topic. In this scenario, an original and fast algorithm able to effectively cope with costly problems involving time-consuming analyses is developed. It is a metaheuristic based on swarm intelligence and hybridized with interpolation strategies, i.e., the Artificial super-Bee enhanced Colony (AsBeC) algorithm. Evidences for its numerical validation are discussed and it is compared on different analytical benchmarks and international competitions with other cutting-edge modern algorithms. A first version for the algorithm (ABC+) was applied to aeronautical LPTs for Single-Objective (SO) problems in an international conference proceeding (AIDAA [Ampellio et al., 2013a]), while another interesting Multi-Obj
A hybrid swarm-based algorithm for single-objective optimization problems involving high-cost analyses
Full text linkA hybrid ABC for expensive optimizations: CEC 2016 competition benchmark
No full textAn evolution of the Artificial Bee Colony (ABC) optimization algorithm, called the Artificial super-Bee enhanced Colony (AsBeC), is presented for leading to the best improvement with a low number of analyses. AsBeC is designed to provide fast convergence speed, high solution accuracy and robust performance over a wide range of problems. It implements enhancements of ABC structure and original hybridizations with interpolation strategies. The aforementioned techniques are tested on the expensive benchmark of the Special Session on RealParameter Single Objective Optimization at CEC 2016. In this specific case, the hybridization with a quadratic trust region approach assumes a major importance. Moreover, the AsBeC results are compared to the algorithms tested on the same benchmark at CEC 2015, showing remarkable competitiveness and robustnes
Multidiscipinary Optimization For Gas Turbines Design
Full text linkState-of-the-art aeronautic Low Pressure gas Turbines (LPTs) are already characterized by high quality standards, thus they offer very narrow margins of improvement. Typical design process starts with a Concept Design (CD) phase, defined using mean-line 1D and other low-order tools, and evolves through a Preliminary Design (PD) phase, which allows the geometric definition in details. In this framework, multidisciplinary optimization is the only way to properly handle the complicated peculiarities of the design. The authors present different strategies and algorithms that have been implemented exploiting the PD phase as a real-like design benchmark to illustrate results. The purpose of this work is to describe the optimization techniques, their settings and how to implement them effectively in a multidisciplinary environment. Starting from a basic gradient method and a semi-random second order method, the authors have introduced an Artificial Bee Colony-like optimizer, a multi-objective Genetic Diversity Evolutionary Algorithm [1] and a multi-objective response surface approach based on Artificial Neural Network, parallelizing and customizing them for the gas turbine study. Moreover, speedup and improvement arrangements are embedded in different hybrid strategies with the aim at finding the best solutions for different kind of problems that arise in this fiel
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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