565 research outputs found
Controllable pitch propeller actuating mechanism, modelling and simulation
No full textThis article focuses on the mathematical model of the pitch control mechanism for a marine controllable pitch propeller, with the aim of describing the dynamic behaviour of this kind of system and its influence on ship performance. Too great a load on the blades can result in high pressures in the actuating system, response delays and control system problems, which are ultimately responsible for most mechanism failures. The behaviour of the controllable pitch propeller actuating mechanism is considered in terms of blade position, oil pressures inside the controllable pitch propeller hub and magnitudes of the forces acting on the blades. In the proposed mathematical model, the forces acting on the propeller blade are evaluated taking into account the yaw motion of the ship, the propeller speed (including shaft accelerations and decelerations) and the turning of the blade during the pitch change. On the basis of the introduced procedure, a controllable pitch propeller numerical model as part of an overall propulsion and manoeuvrability simulator representing the dynamic behaviour of a twin-screw fast vessel is developed. The aim of this work is to represent the ship propulsion dynamics through time-domain simulation, based on which the designers can develop and test several design options, in order to avoid possible machinery overloads with their consequent failures and to obtain the best possible ship performances. In this aspect, the controllable pitch propeller model is an essential design tool
.EP2199258 - A process for producing optionally doped elemental boron
No full textEuropean Patent on nanostructured boro
Numerical modelling of propulsion, control and ship motions in 6 degrees of freedom
No full textThis work presents the main steps for the development of a multi-physic simulation platform, able to represent the dynamics of a twin screw ship in six degrees of freedom, taking into account the complete propulsion system including automation effects. The simulation platform has to be used in the preliminary design phase in order to study and design the propulsion plant and its control system. The ship motion model has been developed including roll motion, in order to capture the ship heel angles during tight turning circles, which may be significant for a fast naval vessel. Moreover, the simulation model includes a simplified representation of the asymmetric behaviour of the two propeller shafts during manoeuvres, which cannot be neglected when dealing with the propulsion plant behaviour. Several sub-models have been developed and calibrated by means of a set of experimental tests, in model and full scale. The sea trials campaign is finally used to validate and tune the developed simulator, thus the final version may be adopted as an optimization tool for other future designs (or sister ships) and for training purposes. Although the presented case study has been validated on a specific ship, most of the discussed models have a general application
Introduzione alle Logiche Modali
No full textLa logica modale è nata per studiare i ragionamenti su ciò che è possibile e ciò che è necessario. Negli ultimi decenni, a partire dal lavoro di logici e filosofi quali Rudolf Carnap, Saul Kripke e David Lewis, la sua applicazione è stata progressivamente estesa ad altri ambiti, quali il ragionamento sul tempo, sulla conoscenza e sui sistemi di norme. Queste ricerche hanno condotto a un complesso e intrigante dialogo con alcune fondamentali branche della filosofia: la metafisica, l’epistemologia, la filosofia del linguaggio. Lo scopo del volume è offrire una panoramica di questo dialogo al contempo accessibile e rigorosa, pensata sia per gli studenti di un corso universitario, sia per il lettore non specialista. Se da un lato tutte le necessarie nozioni tecniche sono rese accessibili ai non addetti ai lavori, dall'altro si restituisce un'immagine fedele delle sfide concettuali che la ricerca in questi settori è oggi chiamata ad affrontare
Comment on “Sound velocity and multibranch Bogoliubov spectrum of an elongated Fermi superfluid in the BEC-BCS crossover”
No full textFil: Capuzzi, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Vignolo, P.. No especifica;Fil: Federici, F.. No especifica;Fil: Tosi, M. P.. No especifica
A mathematical model of the propeller pitch change mechanism for the marine propulsion control design
No full textThe paper is mainly focused on the mathematical model of the control pitch mechanism for a marine controllable pitch propeller (CPP), able to perform the propeller blade position change and to give a proper information about the oil pressures, produced inside the CPP hub. In fact, too high pressures can be responsible for the mechanism failure, then they should be always under examination by the ship automation. With regard to the traditional representation of the few spindle torque data reported in literature, in the proposed mathematical model the transportation inertial forces and the Coriolis inertial forces acting on the propeller blade are evaluated taking into account the yaw motion of the ship, the propeller speed (including shaft accelerations and decelerations) and the blade turning during the pitch change. On the basis of the introduced procedure, it is developed the CPP model which is part of an overall propulsion simulator, representing the dynamic behaviour of a twin-screw fast vessel. The aim of the work is to represent the ship propulsion dynamics by time domain simulation, on the ground of which the automation designers can develop and test several propulsion control options. A brief description of the simulation approach adopted for the vessel crash stop is illustrated at the end of this paper. In particular, the propulsion control action is studied taking into account machinery performance and constraints, including also the control pitch mechanism feedback in terms of allowable forces and pressures
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