1,721,098 research outputs found
MOTORI E SISTEMI PROPULSIVI PER AUTOVEICOLI
No full textLa conoscenza dei motori a combustione interna costituisce una delle principali basi formative che devono caratterizzare la figura dell’Ingegnere Meccanico, in particolar modo dell’Ingegnere del Veicolo. Questo testo si propone di presentarne le principali tipologie e di descriverne i principi di funzionamento, ed è indirizzato a tutti coloro che affrontano per la prima volta, a livello universitario, lo studio di queste macchine complesse. In questa nuova edizione sono state aggiunte alcune sezioni che riflettono l’evoluzione dei motori a combustione interna nell’ultimo decennio, con particolare riferimento alle emissioni inquinanti e al loro trattamento e controllo, così come alle più promettenti frontiere di ricerca sul tema delle combustioni innovative. Inoltre, l’integrazione dei motori a combustione interna in più complessi “sistemi propulsivi” ha motivato la stesura di capitoli riguardanti la descrizione delle più comuni architetture di veicoli ibridi a batteria, corredati da una presentazione dei principi di funzionamento delle pile a combustibile (o “fuel cells”) per uso automobilistico. Si auspica che questo testo possa costituire una solida base di conoscenze, a partire dalle quali lo studente interessato ed appassionato potrà sviluppare i numerosi approfondimenti richiesti dallo studio di questa complessa ed affascinante materia
Intake manifold primary trumpet tuning options for fuel flow limited high Performance I.C.E
No full textThe 2014 change in Formula One regulations, from naturally aspirated to highly-downsized and heavily-boosted hybridized power units, led to a relevant increase of the internal combustion engine brake specific power output in comparison with former V-8 units. The newly designed “downsized” engines are characterized by a fuel flow limitation and a relevant increase in the thermal loads acting on the engine components, in particular on those facing the combustion chamber. Furthermore, efficiency becomes an equivalent paradigm as performance. In the power unit layout, the air path is defined by the compressor, the intercooler and the piping from the intake plenum to the cylinder. Intake duct length is defined from intake plenum to valve seat and it is a key parameter for engine performance. In order to find the optimum length different design criteria can be applied: the so called “tuning”, the “un-tuning” or the “anti-tuning” are all valid possibilities, showing pros and cons. The scope of the paper is to study and present the possible different tuning options for the internal combustion engine (ICE) part of a hybrid F1 powertrain. From 2015, variable trumpet can be used: the continuous variable length may be used to optimize volumetric efficiency and furthermore to reduce knocking and improve combustion accordingly. The scope of the paper is to show and qualitatively compare all the different options for a hybrid powertrain with fuel flow limited combustion unit
On the resistance offered to compressible flow by obstructions in series
No full textA method is proposed for the determination of the flow characteristic of two flow restrictions in series, where an eliptical curve represents the relationship between the expansion coefficient (ratio of upstream and downstream pressures) and the reduced flow rate' for each individual obstruction. Elipse parameters are calculated for choking flow conditions of the combined system and the accuracy of the method is considered in the light of the assumptions made. (C.C.B.
Spontaneous occlusion of a supraclinoid aneurysm after extra-intracranial by-pass using a long graft: report 2 cases
No full textPressure balancing in external gear pumps and motors
No full textThe paper relates on a numerical method for designing balancing bearing block areas for external gear pumps and motors. At first, a way is presented for obtaining pressure distribution inside spaces between teeth, bearing blocks and casing; the procedure, based on integration of the continuity equation for sealed spaces, permits also the evaluation of some interesting aspects dealing with the influence of rotational speed, dynamic viscosity and gears eccentricity. Then, a method is presented for calculating pressure distribution in the layer bounded by gears sides and bearing blocks. The method, starting from pressure distribution in spaces, is based on the integration of the laspace equation over the whole layer. Axial thrust on bearing blocks and its point of application are then calculated. Finally, the same problem is analysed with a simplified numerical approach, as well based on the integration of the laplace equation, but on the small portion of the layer corresponding to one tooth, with only one boundary condition. At the end, calculations are made for a commercial pump, obtaining balancing aeras very close to the ones designed by the manufacturer
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