1,720,984 research outputs found
Analisi dell'influenza della geometria della camera di combustione di un motore diesel a precamera sul rumore di combustione
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Riduzione delle oscillazioni di pressione e del rumore in una pompa ad ingranaggi
No full textAl fine di ridurre le oscillazioni di pressione alla mandata di una pompa ad ingranaggi ed il rumore, si è realizzato uno studio sperimentale per poter valutare il comportamento della pompa stessa dopo la applicazione di un risonatore di Helmholtz. Sono State provate tre diverse configurazioni di risonatore: due realizzate a puro scopo di indagine di laboratorio; ed una che risulta assemblata al corpo stesso della pompa, ed è, quindi, adatta alla produzione in serie
Numerical study on the combustion chamber shape for Common Rail HSDI Diesel engines
No full textThe Common-rail injection system has allowed achieving a more flexible fuel injection control in DI-diesel engines by permitting a free mapping of the start of injection, injection pressure, rate of injection. All these benefits have been gained by installing this device in combustion chambers born to work with the conventional distributor and in-line-pump injection systems. Their design was aimed to improve air-fuel mixing and therefore they were characterized by the adoption of high-swirl ports and re-entrant bowls. Experiments have shown that the high injection velocities induced by common rail systems determine an enhancement of the air fuel mixing. By contrast, they cause a strong wall impingement too. The present paper aims to exploit a new configuration of the combustion chamber more suited to CR injection systems and characterized by low-swirl ports and larger bowl diameter in order to reduce the wall impingement. The goal is to achieve a higher air flow rate during induction as well as to reduce the fuel vapor wall impingement without compromising air-fuel mixing efficiency. This new combustion chamber configuration has been tested numerically and its performances have been compared to those of a H.S.D.I four valve diesel engine conventional combustion chamber. The analysis has been carried out by using a customized version of the CFD code KIVA3. Experimental results of the conventional combustion chamber have been used to validate the numerical models. The influence of the injection system configuration (i.e, hole numbers, inclination of the spray axis with respect cylinder head) on pressure cycle and NO x and soot engine-out emissions has been analyzed too. Computational results seem to indicate that the new combustion system concept may provide relevant benefits with respect to engine-out emissions without reducing engine performance
Coupling Between 1D-3D Simulation Results to Predict Cavitation in Motorcycle Forks
No full textFork system is a primary component for motorcycles because it assures the contact between tires and road, therefore the safety and the driving feeling. Usually fork optimization and tuning are experimentally made involving the generation of a high large number of prototypes and an expensive experimental campaign. To reduce the design and the tuning phases of a generic damper system, the numerical simulation should be considered.
In this paper, a one-dimensional (1D) model of fore-carriage forks for road applications is presented. The model was built-up in AMESim code. In particular, the authors’ attention was focused on the detection and analysis of cavitation phenomenon inside the fork. As well known, the cavitation is a complex three-dimensional (3D) phenomenon that implies the phase transition. Cavitation development and prediction are beyond 1D model capabilities, therefore the 1D fork model was improved by 3D Computational Fluid Dynamic (CFD) multiphase simulations performed by using Fluent v12 (beta version). 3D numerical results were integrated into the 1D model to define a new numerical test methodology able to reproduce the overall fork behaviour.
All 1D numerical results were compared to experimental damping force traces obtained for different fork rod axial velocities
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
Optimization of the Solenoid Valve Behavior in Common-Rail Injection Systems
No full textInjection rate profile is a powerful tool to control engine performance and emission levels. In particular, the Common Rail (C.R.) injection system has allowed flexible fuel injection in DI-diesel engines by permitting a free mapping of the start of injection, injection pressure, rate of injection and, in the near future, multiple injections,. This paper deals with improvements of stable operating condition limits of the Common Rail injector for multiple injection purposes. The focus was to optimize the behavior of the solenoid valve in order to reduce the minimum time interval between two consecutive injections required for system stability. An extensive experimental characterization of the valve has been performed in order to measure the main mechanical and electrical parameters of the assembly components. The experimental and the numerical studies have allowed optimizing the current profile and consequently the design of the anchor pin-ring assembly of the solenoid valve. A new sole..
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