653 research outputs found
Investigation on Pre-Ignition Combustion Events and Development of Diagnostic Solutions Based on Ion Current Signals
No full textPre-ignition combustions are extremely harmful and undesired, but the recent search for extremely efficient spark-ignition engines has implied a great increase of the in-cylinder pressure and temperature levels, forcing engine operation to conditions that may trigger this type of anomalous combustion much more frequently. For this reason, an accurate on-board diagnosis system is required to adopt protective measures, preventing engine damage. Ion current signal provides relevant information about the combustion process, and it results in a good compromise between cost, durability and information quality (signal to noise ratio levels). The GDI turbocharged engine used for this study was equipped with a production ion current sensing system, while in-cylinder pressure sensors were installed for research purposes, to better understand the pre-ignition phenomenon characteristics, and to support the development of an on-board diagnostic system solely based on ion current measurements. In this work, pre-ignition events induced by heavy knocking operation have been analysed. The focus was mainly on ion current signal real-time processing, and on the possibility to correctly and rapidly detect pre-ignition events. In a previous work, destructive effects of this kind of combustion on engine components had been described. As shown in the paper, the development and implementation of an ion current based detection algorithm results to be very effective in identifying pre-ignition combustions, and it could allow an extremely fast reaction of the engine controller that can prevent further anomalous combustions once the first event has occurred. Moreover, pre-ignition phase information extracted from the ion signal and characteristic combustion angles obtained from pressure signal analysis are well correlated, further confirming the ion signal robustness and accuracy
Turbocharger Control-Oriented Modeling: Twin-Entry Turbine Issues and Possible Solutions
No full textThe paper presents possible solutions for developing fast and reliable turbocharger models, to be used mainly for control applications. This issue is of particular interest today for SI engines since, due to the search for consistent CO2 reduction, extreme downsizing concepts require highly boosted air charge solutions to compensate for power and torque de-rating. For engines presenting at least four in-line cylinders, twin-entry turbines offer the ability of maximizing the overall energy conversion efficiency, and therefore such solutions are actually widely adopted. This work presents a critical review of the most promising (and recent) modeling approaches for automotive turbochargers, highlighting the main open issues especially in the field of turbine models, and proposing possible improvements. The main original contribution is then on solving specific issues related to the twin-entry turbine, to develop a control-oriented model able to predict the machine behavior under all possible admission conditions. The results of this study have been applied to a V8 high-performance GDI engine with twin-entry turbochargers. Experimental data are shown throughout the paper, to demonstrate the benefits of the proposed approach
Lucio Fauno: “Alli lettori”, in: Delle antichità della citta di Roma, raccolte e scritte da M. Lucio Fauno con somma brevità, et ordine, con quanto gli Antichi ò Moderni scritto ne hanno, Libri V. (Venezia 1548) (FONTES 13)
No full textAt the end of his book, 'Delle antichità della città di Roma' (Venezia 1548), the author, Lucio Fauno, appends a postscript in which he addresses his readers (“Alli Lettori”) concerning a then bitter controversy about the correct location of the Roman Forum. In contrast to a widely-held view that located the Forum between the Capitoline Hill and the Arch of Titus, Pirro Ligorio, and his friends, Gabriele Faerno and Benedetto Egio, advocated a position that relocated the Forum between the Capitoline Hill and the Palatine. This contradicted the prevailing consensus, as it was established in the Topographia Antiquae Romae (1534) of Bartolomeo Marliani. Fauno’s arguments refute the Ligorian postion, in defence of his own description of Roman topography provided in his book of the Antichità di Roma. In the course of time Ligorio’s relocation of the Forum proved to be wrong. In the discussion of ‘Lucio Fauno’, it is shown that this name is a pseudonym for the writer and antiquarian, Giovanni Tarcagnota of Gaeta (d. 1566)
Five Easy Pieces dedicated to Ludovico Quaroni
No full textThe first edition of this book was published in Italian in 1989, about two years after the death of Ludovico Quaroni; this edition in English is addressed mainly to non-Italian scholars with an interest in modern architecture in Italy. Given the imperfect parallel between musical and literary composition, therefore, in this book an intimate intellectual atmosphere prevails, which reveals the author’s skill in creating a narrative and also in engaging in a type of critical writing that is rarely undertaken by architect-intellectuals. The five episodes in the book cover almost thirty years, from 1958 to 1987, which were years that remained deeply preserved in the author’s memory. The literary form of the pieces gives all of them a common structure: they are dialogues; usually consisting of brief exchanges of few words, spoken or written, between the author (Lucio Barbera) and Quaroni. In one of them – Charisma – the dialogue takes place between Quaroni and a larger chorus. In another – Elective Misunderstanding – we have a double dialogue at a distance, a trio, if we return to the musical metaphor, between Quaroni, Lodovico Barbiano di Belgiojoso and Barbera. The last piece is a longer conversation by Quaroni on himself; a taking stock and a valediction. On the frontispiece, Barbera gives a clear indication of his intentions: “For students of Architecture who are well-educated and for architects interested in getting to know better a Master of their trade”
Investigation of Knock Damage Mechanisms on a GDI TC Engine
No full textThe recent search for extremely efficient spark-ignition engines has implied a great increase of in-cylinder pressure and temperature levels, and knocking combustion mode has become one of the most relevant limiting factors. This paper reports the main results of a specific project carried out as part of a wider research activity, aimed at modelling and real-time controlling knock-induced damage on aluminum forged pistons. The paper shows how the main damage mechanisms (erosion, plastic deformation, surface roughness, hardness reduction) have been identified and isolated, and how the corresponding symptoms may be measured and quantified. The second part of the work then concentrates on understanding how knocking combustion characteristics affect the level of induced damage, and which parameters are mainly responsible for piston failure. For this purpose, steady-state tests have been conducted controlling different and constant levels of knock intensity (i.e., pressure waves oscillation amplitude) and thermal load (i.e., average temperature and pressure levels inside the combustion chamber). Since these parameters are strictly interrelated for a given engine operating condition and for a given fuel, fuels with different knock resistance (i.e., RON number) have been employed, to allow a clearer understanding of the damage distribution in the knock intensity-thermal load domain
Toward a new paradigm in open economy modeling: where do we stand?
No full textThis paper provides a selective, up-to-date survey of the recent, fast-growing literature on new open economy macroeconomics. Lucio Sarno begins with a review of the seminal paper in this literature, describing the baseline model proposed therein. He then covers a number of variants and generalizations of the baseline model involving the allowance for nominal rigidities, pricing to market, alternative preference specifications, and alternative financial markets structures. The author also discusses the recent stochastic extensions of these models, especially focusing on their implications for the link between risk and exchange rates and on new directions for the relevant literature.Econometric models ; Macroeconomics
Experimental observations of engine piston damage induced by knocking combustion
No full textAbnormal combustion leads to a significant increase in combustion speed, pressure and temperature at the surfaces enclosing the combustion chamber. Severe and lasting knock or pre-ignition can permanently damage and, in many cases, destroy engine pistons, due to very high and localised thermomechanical stresses. The deleterious effects of abnormal combustions have led car manufacturers to set extremely precautionary thresholds in spark advance calibration (in terms of temperatures and pressures) of turbocharged spark ignition direct injection engines, often limiting engine performance and efficiency. Since the mechanisms of piston damage due to abnormal combustion are not currently fully understood, the aim of this study was to characterise its effects on Al forged pistons. The more suitable characterisation techniques were evaluated. The results highlighted that roughness measurements, as well as visual, optical and scanning microscopy analyses on specific zones of the top land and piston crown are useful techniques to qualitatively relate piston damage to combustion regime. Moreover, a significant quantitative relationship was observed between the MAPO (Maximum Amplitude Pressure Oscillations) index and residual piston hardness
Per una rilettura del prologo di Marziano Capella
No full textIl "De nuptiis Philologiae et Mercurii" di Marziano Capella si apre con un doppio prologo in versi e in prosa. Nella prosa l’autore è interrogato dal figlio sul significato dell’inno che ha appena recitato e che il giovane attribuisce a esercizio di un perdigiorno. Il verbo con cui questa attività viene bollata è, nella tradizione manoscritta, il neologismo greco γυμνολογίζεις che potrebbe essere interpretato sulla base di un altro neologismo, γυμνολογία, termine che compare nelle dispute teologiche sulla natura umana e/o divina del Cristo.Martianus Capella’s "De nuptiis Philologiae et Mercurii" opens with a double prologue, written in verse and in prose. In the prose section, the author is questioned by his son about the meaning of the hymn he has just recited and which the young man considers to be the creation of an idler. The verb with which this kind of activity is defined is, in the manuscript tradition, the Greek neologism γυμνολογίζεις, which could be interpreted on the basis of another neologism, γυμνολογία, a term which appears in the theological disputes on the human and/or divine nature of Jesus
Metastasio sul letto di Procuste. A proposito di due sonetti per nozze
No full textMetastasio wrote a limited number of sonnets, and in various letters expressed deep perplexities about the value and the efficacy of this poetic form. A recent edition of his “Poesie”, edited by Rosa Necchi in 2009, offers the twenty-nine texts approved by the author as well as six more ones discovered from the end of the Eighteenth Century up to recent times. The article adds to this corpus two forgotten sonnets included in epithalamic anthologies printed in Naples in 1717 and in Rome in 1722 respectively, and illustrates their unexpected subsequent re-uses
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