11,789,405 research outputs found
NONCOMPACTION OF THE LEFT VENTRICULAR MYOCARDIUM IN CHILDREN: CLINICAL AND PHYSIOPATHOLOGIC FEATURES
No full textFazio, G; Novo, S; Zito, R; Icona, MA; Marchì, S; Mongiovì, S; Gagliano, S; Pipitone,
A New Simple Friction Model for S. I. Engine
No full textInternal combustion engine modeling is nowadays a widely employed tool for modern engine development. Zero and mono dimensional models of the intake and exhaust systems, combined with multi-zone combustion models, proved to be reliable enough for the accurate evaluation of in-cylinder pressure, which in turn allow the estimation of the engine performance in terms of indicated mean effective pressure (IMEP). In order to evaluate the net engine output, both the torque dissipation due to friction and the energy drawn by accessories must be taken into consideration, hence a model for the friction mean effective pressure (FMEP) evaluation is needed. One of the most used models accounts for engine speed dependent friction by means of a quadratic law, while the effect of engine load (i.e. the thrust that the gas exercises on the piston surface) is considered by means of a linear dependence from the maximum in-cylinder pressure: hence the model requires the calibration of four constants by means of experimental data. The author, on the basis of data acquired during an extensive experimental campaign carried out on the engine test bed, found this model to give an unsatisfying prediction, above all for retarded pressure cycles (i.e. with peak pressure positions higher than 20 crank angle degrees after top dead centre): hence, by means of analysis performed using these experimental data, the author arrived at a new formulation of the friction model, which substantially take into account the effect of engine load by means of the Location of Pressure Peak (LPP). The new model, once calibrated, proved to be effectively more accurate in the prediction of the FMEP than the Chen-Flynn model
In ricordo di Vincenzo Pipitone
No full textIl professor Vincenzo Pipitone, Reumatologo del - l’Università di Bari, è deceduto nella notte di venerdì 14 novembre. Le sue condizioni di salute erano precarie da lungo tempo. Eppure, per quell’ingannarsi tipicamente umano di chi vuol bene, a noi allievi il Professore sembrava destinato a non andarsene mai..
Forum Civico della Città di Messina. Introduzione (A. Tulumello). Analisi socio-economica (R. Foderà, V. Pipitone, A. Tulumello)
No full text
A COMPARISON BETWEEN COMBUSTION PHASE INDICATORS FOR OPTIMAL SPARK TIMING
No full textThe closed-loop control of internal combustion engine spark timing may be accomplished by means of a combustion phase indicator i.e., a parameter derived from in-cylinder pressure analysis, whose variation is mainly referable to combustion phase shift and assumes a fixed reference value under optimal spark timing operation. The aim of the present work is a comparison between different combustion phase indicators, focusing on the performance attainable by a feedback spark timing control, which uses the indicator as pilot variable. An extensive experimental investigation has been carried out, verifying the relationship between indicators' optimal values and the main engine running parameters: engine speed, load, and mixture strength. Moreover assessment on the effect of the most common pressure measurement problems (which are mainly related to pressure referencing, sampling resolution, top dead center determination, and cycle-by-cycle variations) on the indicators' values and on the performance attainable by the spark timing control is included. The results of the comparison point out two indicators as the most suitable: the location of pressure peak and the location of maximum heat release rate. The latter, not available in literature, has been introduced by the author as an alternative to the 50% of mass fraction burned
Development of a low-cost piezo film-based knock sensor
No full textIt is well known that spark advance is a key parameter in spark ignition engine management. Increasing fuel cost and emission regulation strictness require a higher engine efficiency, which can be improved by an accurate regulation of the spark advance. Under high load conditions, an optimal spark advance choice leads the engine to run next to the knock limit, so the management and control system needs to be equipped with a knock sensor in order to preserve the engine from damage. The authors developed a low-cost knock sensor whose sensing element is a thin washer of polyvinylidine fluoride (PVDF), a fluoropolymer characterized by a great piezoelectric effect if polarized. The sensor has been tested on a spark ignition CFR engine (the standard single-cylinder test engine used by ASTM for octane number determination of spark ignition engine fuel) and compared with a commercial accelerometer and a pressure sensor, in terms of knocking detection capability, measured knock intensity (KI) and signal-to-noise ratio (SNR). Knocking tests have also been carried out on a Renault series production engine. The collected data show that PVDF ensures a reliable detection of knock, a precise measurement of knock energy and accurate information about the frequency content of the perceived vibration. The sensor worked for several hours without depolarizing and, above all, owing to the great piezoelectric effect of PVDF, the use of a charge amplifier was unnecessary. PVDF proved to have great potential as a knock detector in spark ignition engines at a very low cost
- …
