Patrizio Nuccio

Automobile Aerodynamic Drag on the Road Compared With Wind Tunnel Tests

This investigation was performed with the purpose of comparing the arodynamic drag of an automobile as measured in a full-scale wind tunnel with the drag as measured on the road. A definition of the drag coefficient as measured both on the road and in the wind tunnel is given in advance in order to allow a comparison to be made between the two operating conditions. Three medium size european cars were selected, one notch-back type and two hatch-back types. Road testing was mainly based on the coast-down method. The total resistance was determined by statistical analysis of the experimental results. The theoretical basis and the specifications of the procedure are investigated and justified. Additional outdoor and indoor tests were carried out in order to isolate the aerodynamic drag. The wind tunnel tests were conducted on the same cars fully equipped as tested on the road and in the same speed range. The wind tunnel tests being executed at steady speeds, however, supplementary road tests were performed in order to determine the effect of the deceleration on the aerodynamic drag. The final results show only small differences between the aerodynamic drag coefficients as measured in the wind tunnel and on the road with the procedure here described

Knock-Limit Measurement in High-Speed S.I. Engines

A measurement method to detect the knock-resistance and, especially, the knock-limited conditions of high-speed s.i. engines is described. Two instruments are used in conjunction: the first instrument measures a knock intensity index I.D. related to knock-typical pressure oscillations in the combustion chamber; the second instrument detects the knock-limited conditions in real time, by means of I.D. This latter instrument, which can be properly used as a knock-limit detector in operating-parameter control systems for automotive engines, is analyzed in detail. Its operating principles, based on statistical criteria, are described and verified by means of experimental tests. The checking tests carried out at high speed, both on a mass-produced automotive engine and on a prototype, are described. The knock resistance of the prototype, in its whole working range, is then analyzed.

Establishment of a Model for a Combined Heat and Power Plant with ThermosysPro Library

Abstract The Simulation and Information Technologies for Power Generation System Department (STEP) has developed a methodology, as part of the framework of an EDF R&D project, to model and optimize energy systems for the associated companies with the aim of highlighting the possibility of using modelling tools to optimize energy systems. Dymola software, a commercial implementation of Modelica, which was developed by Dassault Systemes has been employed. A library, called ThermosysPro and developed by EDF R&D, has in particular been used. The energy system presented in the paper is a Combined Heat and Power plant (CHP), managed by Fenice SpA, which has been designed to supply electric and thermal energy to a food factory near Parma (Italy). This kind of system can be regulated over a large power range and, as a consequence, the CHP plant can supply the total amount of thermal energy required by the user. From a comparison of the experimental data and the simulation results, it can be seen that the behaviour of the turbo gas and the steam turbine approximately follows the results of the performance test at full load over a wide temperature range. As far as the performance at partial load, the gas turbine Heat Rate and the heat recovery steam generator (HRSG) performance are concerned, the simulation results and the actual CHP plant behaviour again appear to be in good agreement.

A New GDI 2-Stroke Engine to Meet Future Emission Limits: The Design and Prototype Architecture

As more stringent emission limits and low consumption requirements also involve s.i. 2-stroke engines, one of the most important design modifications that can cope with these constraints is to perform the scavenging process using pure air, which means not only fuel-free air but also oil-free air. A new single-cylinder prototype engine, equipped with a gasoline direct injection (GDI) apparatus has therefore been designed and built. In order to reduce manufacturing costs, this prototype was obtained by modifying a mass-produced 4-stroke 4-cylinder automotive engine. Apart from the replacement of the original indirect fuel feeding system with GDI, two more remarkable features should be pointed out: the use of a force-fed lubrication system, like those used in current 4-stroke engines and, as a consequence, the use of an external scavenging pump. Before using an electronically controlled direct injection system on the new prototype engine, the whole apparatus was tested on a mass-produced crankcase scavenged 2-stroke engine (Husqvarna WR 250) in order to evaluate the magnitude of the improvements. A comparison of a carburettor fuel feeding system with a direct fuel injection system was carried out, under cubic power requirements, to check whether the GDI strategies were advantageous. As satisfying results were obtained, the direct injection apparatus was mounted onto the prototype engine for the first experimental tests.

Optimization of a Light Aircraft Spark-Ignition Engine

The aim of this study was to find a convenient set-up for an innovative engine dedicated to light aircraft through a numerical one-dimensional simulation. Six different engine layouts were analyzed in order to find the highest power/weight ratio and the least voluminous configuration. The first was a four cylinder, four stroke, horizontally opposed, naturally aspirated, water cooled engine with 16 valves that delivered 75 kW (~100 bhp) at 2400 rpm for an estimated weight of 65 kg. A gearbox was also used in the naturally aspirated model to decrease the displacement, the weight and the overall dimensions. The other solutions involved these two engines in a turbocharged layout in order to gain a further downsizing. The supercharging was obtained through a centrifugal compressor driven by an exhaust gas driven turbine, which also allows the power to be restored at cruising altitude. The other engines were two stroke turbocharged engines (compressor driven by gas turbine) with and without a gearbox. The most important innovations of the two-stroke engines concern the turbocharge group, an unidirectional-flow scavenging scheme with four all-acting exhaust valves, a forced-fed lubricating system and a direct fuel injection in order to reduce fuel consumption and pollution. The results have shown that the four and the two-stroke turbocharged engines are the most promising as far as the power/weight ratio and dimension reduction are concerned.

Experimental Analysis of the Combustion Process of Commercial and Reference Fuels on the CFR Laboratory Engine

As in the standard American Society for Testing and Materials (ASTM) procedure which is used to evaluate the fuel Octane Number (ON), some signal properties are considered, while others are neglected, it happens that different pressure signals of the sensor, obtained from different fuels and operating conditions, can lead to the same Knock Intensity index (KI) value, even though the knock behavior is not the same. Therefore the aim of this work was to analyze the standard signal processing chain of the Cooperative Fuel Research engine (CFR) (from the pressure sensor to the knock-meter display) and its effects on the value of the KI, for different fuels and operating conditions.

A Contribution to the Improvement of an Open-Chamber Stratified-Charge Engine

The developments of an open-chamber stratified-charge engine are herein described; the aim of this engine is to work at part-loads with low fuel consumption while remaining, however, under acceptable exhaust emissions.The essential purpose of this research has been to markedly amplify the overall air-fuel ratio field in which the engine working is regular. This also serves to modify the engine load by varying the air-fuel ratio instead of air throttling so that the corresponding losses can be avoided.By studying and setting up a proper injector, the fuel injection system has been considerably improved. In fact this injector gives a suitable spray geometry, with particular regard to the spray penetration, the spray angle and the droplet size. Injection pressure and timing have also been investigated in order to optimize engine performance.At present, under wide open throttle conditions, the engine already works with overall air-fuel ratio variable up to four times the stoichiometric value.