1,721,004 research outputs found
Experimental Characterization of Discharge Coefficient and Tumble Motion from a Competition Engine Intake System
No full textIn the present work the discharge characteristics of a racing engine intake system are examined. Peculiar attention was paid to the evolution to the flows originated from the single valves and to their mutual influences, in order to estimate their potential effect in terms of global discharge coefficients. The analysis was also extended to the investigation of the tumble generation phenomena, while the steady tumble measurement techniques effectiveness were discussed
Sviluppo di un Apparato per la Misura della Portata Istantanea di Sistemi di Iniezione Diesel
No full textNel presente lavoro viene descritto lo sviluppo di un sistema di misura della portata istantanea d’iniezione basato sul concetto dell’iniezione in camera a volume costante (Metodo di Zeuch). In tale apparato, il fluido è iniettato all’interno di una camera indeformabile di ridotto volume riempita con lo stesso fluido di lavoro. L’introduzione del nuovo fluido causa un incremento della pressione in camera in misura proporzionale al volume iniettato. L’acquisizione della storia della pressione in camera e la sua derivazione consentono la determinazione, colpo per colpo, dell’injection rate effettivo con cui opera il sistema d’iniezione. Nel lavoro saranno presentati i risultati di una vasta campagna di qualificazione dello strumento sviluppato che ha mostrato un’apprezzabile precisione e ripetibilità
Numerical Analysis of a Fluid Flow in a Racing Motorcycle Intake System
No full textIn this study, the experimental results for discharge
coefficient in a 4-valves engine head are compared with
numerical results obtained by using the commercial CFD
program Star_Cd. Different lift valves and different
pressure drops have been considered. Goal of comparison
is validation of numerical results.
The computational model consists of around 600.000 cells
and completely reproduces the actual geometry (inlet
ducts, throttle valve in full load position, inlet manifold,
inlet valves, engine head and outlet ducts)
Modeling Diesel Engine Using KIVA II 3D-Code: Comparative Validation of a Global Combustion Model
No full textThe present work is a further validation and analysis of a global combustion model developed and integrated in the original version of the KIVA-II code. The results obtained from the simulations are discussed comparing them to the experimental data relevant to a DI unit of large size displacement: Caterpillar-3406 heavy-duty truck engine. Some fundamental combustion parameters are analysed and discussed in relation to their sensitivity to the engine size. In particular the results coming from the Caterpillar simulations are compared with ones obtained in the correlated work [1] on a small size engine: Ruggerini RP-170
Experimental Comparison Between Conventional and Bio-Derived Fuels Spray from a Common-Rail Injection System
No full textIn the present study, a commercial high pressure, common rail injection system for automotive DI diesel engines was fed with a conventional diesel fuel, a bio-derived fuel and a blend of them. The comparison of spray characteristics was carried out in terms of tip penetration and cone angles; the fuel spray, generated by rail pressures ranging from 60 MPa to 120 MPa, developed in an atmospheric chamber.
The experimental set-up is based on a laser sheet technique. The radiation scattered by the spray, generated by a Nd Yag pulsed laser, is collected by a CCD camera and fed to a frame grabber. A suitably set up automatic image analysis process allows not only to determine the spray average development in terms of its geometric characteristics, but also to analyse in detail its internal structure. In particular, a suitable elaboration allowed the evaluation of the probability of presence in space of spray liquid fractions
Un metodo non intrusivo per l'analisi di getti da iniettori
No full textNel presente lavoro é presentata un’attività sperimentale mirata alla determinazione, con modalità non intrusive, delle caratteristiche di spray di combustibile mediante visualizzazione del getto con piano di luce laser e analisi delle immagini. Sono descritte le caratteristiche fondamentali della linea sperimentale e, facendo uso di alcuni risultati ottenuti nello studio di sistemi di iniezione sia convenzionali sia ad alta pressione a controllo elettronico (Unijet), sono discusse le procedure di analisi sviluppate per la determinazione quantitativa dei principali parametri del getto
Experimental Comparison Between Conventional and Bio-Derived Fuels Sprays from a Common Rail Injection System
No full textIn the present study, a commercial high pressure, common rail injection system for automotive DI diesel engines was fed with a conventional diesel fuel, a bio-derived fuel and a blend of them. The comparison of spray characteristics was carried out in terms of tip penetration and cone angles; the fuel spray, generated by rail pressures ranging from 60 MPa to 120 MPa, developed in an atmospheric chamber.
The experimental set-up is based on a laser sheet technique. The radiation scattered by the spray, generated by a Nd Yag pulsed laser, is collected by a CCD camera and fed to a frame grabber. A suitably set up automatic image analysis process allows not only to determine the spray average development in terms of its geometric characteristics, but also to analyse in detail its internal structure. In particular, a suitable elaboration allowed the evaluation of the probability of presence in space of spray liquid fractions
Realizzazione e messa a punto di una linea sperimentale per l'analisi di flussi mono- e bi-fase in condotti di aspirazione di motori a combustione interna
No full textNel presente lavoro sono discusse le caratteristiche e le modalità di impiego delle attrezzature sperimentali utilizzate presso l’Università di Perugia per la conduzione dell’attività di ricerca relativa all’ottimizzazione dei sistemi di aspirazione e scarico dei motori a combustione interna. A tale scopo sono impiegati un banco di flussaggio stazionario con misuratore di swirl/tumble, un banco di flussaggio dinamico e un sistema di analisi degli spray nei condotti di aspirazione. I risultati della sperimentazione sono utilizzati sia per la conduzione di verifiche e confronti diretti fra le varie configurazioni oggetto di prova, sia per lo sviluppo e la messa a punto di strumenti di indagine numerica (codici mono- e tri-dimensionali). Nel lavoro, sono riportati alcuni esempi di risultati ottenibili mediante i differenti apparati sperimentali
Analisi numerica del campo di moto interno cilindro di un motore ad accensione per compressione
No full textViene condotta un'analisi dell'evoluzione, durante la fase di compressione, del campo di moto all'interno del cilindro di un motore Diesel sovralimentato ad iniezione diretta per impiego automobilistico. Lo strumento utilizzato è una versione migliorata del codice tridimensionale KIVA-II. L'attenzione è posta essenzialmente sullo sviluppo dei moti di squish e di swirl, sulle loro interazioni e sull'influenza su di essi esercitata da alcuni parametri motoristici
Experimental and Numerical Momentum Flux Evaluation of High Pressure Diesel Spray
No full textIn the present work, an experimental and numerical analysis of high pressure Diesel spray evolution is carried out in terms of spray momentum flux time history and instantaneous injection rate. The final goal of spray momentum and of injection rate analyses is the evaluation of the nozzle outlet flow characteristics and of the nozzle internal geometry possible influences on cavitation phenomena, which are of primary importance for the spray evolution. Further, the evaluation of the flow characteristics at the nozzle exit is fundamental in order to obtain reliable boundary conditions for injection process 3D simulation. In this paper, spray momentum data obtained in ambient temperature, high counter-pressure conditions at the Perugia University Spray Laboratory are presented and compared with the results of 3D simulations of the momentum rig itself. The experimental tests, performed using a commercial common-rail injector, include high speed imaging of the spray during momentum tests and the measurement of instantaneous injection rate for a more detailed comparison with the numerical analysis. Numerical 3D simulations allowed to evaluate the actual contribution to global spray momentum given by the liquid phase and by the gaseous phase, as a function of time, nozzle-target distance and target-diameter. This analysis allowed to explain the observed influences of the measurement procedure on the spray momentum flux experimental data. In particular, the present CFD analysis highlighted a significant contribution to the jet momentum flux provided by gaseous phase, which tends to become predominant with growing distances from the nozzle. The findings suggested that the target design and position can affect significantly the spray momentum flux measurement. In some operating conditions, unexpected trends of the spray momentum time integral as a function of the target distance and target-diameter were obtained, suggesting that main hypotheses on which spray momentum measurement devices are based – i.e. orthogonal flow deviation – may not hold true for some system configurations. A numerical analysis of the spray impact force was developed to evaluate the target intrusiveness, pointing out the irrelevance of the target when present into the simulated domain. A practical policy to define the optimal combination of target-diameter and nozzle-target distance, for each set of operating conditions, as a compromise between the extreme configurations of the involved parameters, is explained
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