1,721,018 research outputs found
Research on the Automobile Aerodynamic Field at the Politecnico di Torino in the Second Half of the Twentieth Century
Full text linkWith this paper the author first of all wants to honor the memory of Professor Alberto Morelli with whom he had the privilege of working for many years at the Politecnico di Torino. Morelli radically changed the way of designing car body shapes, while bringing the aspect of reducing the aerodynamic resistance of a vehicle to the attention of car designers. Morelli’s research activity began in the early 1950s and, between the 1950s and 1960s, he designed and built a number of car prototypes, whose coefficient of aerodynamic resistance was substantially reduced compared to that of the cars of that time, sometimes resorting to revolutionary architectures such as a “diamond” arrangement of the wheels. A fundamental step of Morelli's research in the field of vehicle aerodynamics was the Pininfarina full-scale wind tunnel project, which was set up between the end of the 1960s and the beginning of the 1970s, and was inaugurated in 1972: fifty years have therefore passed since that occasion. An impressive result, obtained in the second half of the 1970s, was the maquette of the Pininfarina-CNR car, which had front air intakes, internal flows as well as other external details, such as rear-view mirrors: in this case, the Cx value was 0.20. His activity continued with significant results in the field of car aerodynamics, in particular concerning the interaction between the wakes of the car and of the wheels
Determinazione del consumo di carburante in motori alternativi per impiego aeronautico
No full textÈ stato realizzato uno strumento di concezione originale per la determinazione in maniera semplice del consumo di carburante in motori alternativi per impiego aeronautico. Il principio di funzionamento di questo strumento è basato sul rilievo di due parametri, quali pressione nel collettore di aspirazione e il numero di giri del motore. Lo scopo dello strumento è quello di fornire un "indice di consumo" da utilizzarsi nelle competizioni di tipo "Economy Race" o al'ottimizzazione del volo in crociera, ma non di sostituire comunque i normali dispositivi per la determinazione della quantità di carburante installati a bordo dei velivoli. Sono quindi ripresentati prima i risultati già ottenuti nell'applicazione dello strumento al banco prova su di un motore di tipo aeronautico, poi quelli ricavati con la simulazione di alcune missioni di volo per due velivoli con potenze installate molto differenti e, infine, la prima applicazione su di un aereo provvisto di un motore di piccola potenza (66 kW) con il quale saranno effettuate le prime prove sperimental
Future perspectives of the two-stroke spark ignition engine
No full textAs more stringent emission limits and low consumption requirements necessary for all current vehicle propulsion systems also apply to s.i. 2-stroke engines, one of the most important design modifications that can cope with these constraints involves performing the scavenging process using pure air, which means not only fuel-free air but also oil-free air.
Current two stroke s.i. engines are therefore equipped with a gasoline direct injection systems (GDI) and are the lubrication apparatus has also been modified in order to reduce both pollutant emissions and oil consumption.
After a short introduction on the two stroke s.i. engine, some examples of this kind of engine that apply these new technical solutions are presented and analyzed.
The second part of the paper instead presents the research activities conducted at the Energy Department Politecnico di Torino on two stroke s.i. engine over the last two decades.
After presenting the first experience gained a two stroke prototype engine, the first experimental results obtained on two mass-produced crankcase scavenged 2-stroke engines, the Benelli FB-1226 and the Husqvarna WR 250, provided with gasoline direct injection, are presented. These experimental results refer to a comparison between a carburettor or gasoline indirect injection fuel feeding system with a direct fuel injection system, as far as fuel consumption and pollutant emissions are concerned.
As satisfactory results were obtained, the direct injection apparatus was mounted onto a new prototype engine and the first experimental tests once more showed encouraging results, as far as fuel consumption and pollutant emissions are concerned
Variable valve timing as a means to control Otto engine load
No full textThis work is the prosecution of a theoretical research which proposed a method to control the Otto engine load by means of a variable valve timing. As can be predicted, the early closing of the inlet valve allows to lower the engine load with reduced air-throttling, so that a fuel economy can be obtained. A hydraulic system was designed to perform the variable valve timing as follows. A rotating distributor, controlled by the camshaft, empties a capacity in the timing system, so the free closing stroke of the valve is determined by its spring. A particular device virtually eliminates the valve impact against its seat. The hydraulic system was applied to a single cylinder engine and bench tests were carried out so as to allow a comparison between the engine performances obtained by air-throttling and those obtained by variable valve timing. Preliminary experimental results are reported and discusse
Main static aeroelastic effects on sailplane longitudinal stability and control
No full textIn the paper the effects of the wing torsional deformation and of the fuselage bending deformation are considered, as being probabily the most important ones. The classical theoretical expressions for equilibrium and stability are therefore modified, in order to take into account these aeroelastic effects, and discussed. A comparison with experimental data registered in flight on a two-seater wooden sailplane allows an appreciation of the better approximation obtained
Contribution to the development of a methodology for misfunctioning detection in SI engines
No full textOn the directional stability of motor cars when approaching and exceeding the adhesion limits between tire and ground
No full textThis paper is concerned with the investigation of the directional phenomena occurring when the limit of adhesion of tires to the ground is reached or overcome. To this purpose, an original mathematical model assuming the car as a system with six degrees of freedom was first developed. The mathematical model includes a model simulating the tire-ground mechanism through which the tangential forces are developed also when the limit of adhesion is exceeded. In the mean time, an original test car was designed and built in order to compare the actual behavior of the car on the road with that of the model. Much of the research time was devoted to checking and setting up the mathematical model for a correct simulation of the behavior of the car on the road. Thereafter, the mathematical model was used alone to determine time histories of important variable of the motion and parameters as lateral attitude, ground-wheel forces, over-steer-under-steer degree etc., describing the directional behavior of the car during exceptional situation as, for instance, the “tête à queue”
A new instrument for fuel consumption measurement in light aircraft and motorgliders
No full textAn original instrument for fuel consumption measurement in reciprocating internal combustion s.i. engines for light aircraft and motorgliders has been developed and built. It based on the detection of two parameters: the engine rotational speed and the manifold pressure. The aim of the instrument is to provide a “fuel consumption index” which can be utilized both in “Economy Air Race” competitions and during the cruising flight. The instrument is not to intended to replace the usual onboard fuel level gauge, but could be used to integrate the flight information with the instantaneous fuel consumption or even with the cruising range indications. Some results of fuel consumption measurements, from both computer simulation and experimental tests, are first presented and then discussed. These were obtained with the instrument installed on the engine during bench tests. Some flight tests were the carried out with the instrument installed on a light aircraft in order to evaluate the instrument response under real operating conditions. The first results thus obtained encourage further development of the instrument
Education and research on automotive engineering at the Turin Institute of Technology
No full textThis paper refers to a previous report presented at th FISITA Congress in Dearborn (USA) dealing with Educational and Training on Automotive Engineering at the Turin Institute of Technology (Politecnico di Torino). This paper is more specifically intended as a description of the research work carried out by both students and young graduates during the concluding period of graduate and post-graduate studies, under their teacher’s guidance. Some examples of research programmes following the direct experience of the authors, including those starting from thesis or dissertations, which contribute success of the programmes themselves, are described. Among these the following are cited and briefly examined: Full scale automotive wind tunnel, Variable valve-timing system for s.i. engine, Indoor tire testing-facility and fallouts. Finally, the way different contributions which come from University, Industry and independent Research Centres should be managed and connected, is considered and discusse
Variable mass crankshaft for general car performance improvement: acceleration, fuel economy and emissions
No full textA passenger car variable mass crankshaft is here reported. This particular device consists of an auxiliary flywheel with a high moment of inertia. It spins freely at above 1500 rpm, thanks to centrifugal masses which disengaged it from the crankshaft. The flywheel is connected once again to the crankshaft, when the engine speed reduces to under 1400 rpm. In this way, the mass of the crankshaft is increase at low engine speed (e.g. idle condition) and the magnitude of rotational fluctuations are consequently lowered. On the contrary, the extra mass is unnecessary and undesirable above certain engine speed and is therefore reduced, so improving both the vehicle acceleration, engine braking performance and fuel economy. He variable mass crankshaft device has been mounted onto a passenger car, in order to determine fuel consumption and acceleration performance, both though theoretical investigations and by means of experimental tests on roller-type bench
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