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A 2.0 liter displacement gasoline fueled car, with closed-loop control and 3-way catalyst, was adapted to operate on CNG (Compressed Natural Gas). A system allowing the detection and measurement of aldehydes, ketones, polycyclic aromatic hydrocarbons (PAH) and speciated organic materials was set up. Running on different fuels, such as CNG, gasoline and gasoline/oxygenates blends, tests were carried out according to US (FTP '75) and European (ECE+EUDC) procedures with and without the original 3-way catalytic converter. Apart from the absence of evaporative emissions because of the required closed delivery system, test results pointed out that CNG use yields substantial air toxics benefits in terms of regulated and, above all, unregulated emissions.

From september 1988 a fleet test started in Italy on urban buses equipped with a single ceramic monolith filter plus a by-pass and Diesel fuel burners for regeneration. The operation of the particulate trap, during the normal bus running in the city, has been assessed in three different ways: 1. Continuous control, by means of a data acquisition system purposely designed, of the main parameters affecting regeneration (i.e. time between consecutive regenerations, temperature in three selected zones in the filter during regeneration,filter loading); 2. Periodic control of smoke opacity of the bus measured, with and without the filter, under free acceleration and when bus is accelerating from 50 to 65 km/h on proving ground; 3. Particulate collection efficiency of the trap by using a dilution tunnel with the engine operated at the test bench. Information carried out from the fleet tests and additional information deriving from laboratory results were used for the system improvement.

The main parameters affecting combustion of heavy-duty D.I. Diesel engines were studied by the utilization of a two-dimensional axisymmetric code taking into account air motion, spray formation and combustion. Model predictions are integrated with the analysis of the main combustion quantities coming from the recorded in-cylinder pressure, injection pressure and needle lift. The trend of the total air momentum and spray formation obtained by changing the swirl level, the combustion chamber shape, the in-cylinder air mass and the fuel jet distribution were compared with the trends of the smoke, fuel consumption, gaseous emissions and heat release rate. Experimental data and model predictions indicate that very different combustion chamber geometries can be adopted in medium and small bore engines. The ratio between the in-cylinder air mass and injected fuel momenta can be useful in defining the optimum air motion and spray formation of a given combustion system.

In direct injection Diesel engines having a unit displacement less than 1 liter, the use of high compression ratios (19\20 instead of 16\17) is mandatory for solving cold smoke problems and reducing HC\NOx emissions. The increase of compression ratio however is associated to the increase of black smoke and specific fuel consumption. On the basis of systematic measurements of the main combustion quantities and 2-D computations of the air motion and spray development inside the cylinder, a re-entrant high compression ratio chamber was defined. Experimental results in terms of fuel consumption, black smoke and gaseous emissions are presented. The optimum squish-to-swirl ratio is discussed.

A light weight diesel engine family having high specific power output (up to 21 KW/1) has been developed for medium trucks (7/13 ton) starting from existing 6-cyl in-line N/A and T/C DI engines with a single displacement equal to 0.915 liters. To meet future U.S. federal and California emission standards changes in combustion chamber shape, swirl level, injection system and turbocarger matching have been introduced. Projections of fuel economy according to the new transient procedure proposed by EPA have been carried out. These have been compared with the projections of a conventional gasoline engine referred to the same vehicles. Finally the main relationships among the combustion parameters, fuel consumption and emissions have been explored.

The impact of turbocharging on Diesel exhaust emissions has been investigated by studying, on a 4-cyl IDI Fiat engine different configurations including fuel injection optimization, exhaust gas recirculation and oxidant catalysts. The experimental results obtained during bench and chassis dynamometer tests were compared with the same tests performed on the naturally aspirated 4-cyl engine. Mathematical models were used in order to identify the regions giving the maximum contribution to regulated emissions. Particulate and organic adsorbed compounds were also measured. It appears that turbocharging can represent a reasonably good approach in order to achieve low levels of regulated emissions and particulates associated with high fuel economy.

High speed knock is one of the major obstacles to higher compression ratios and, consequently, lower fuel consumption. The relationship between engine failure and knock intensity was studied by testing a European engine at 4,000 and 5,000 rpm, on full throttle. Endurance test results show that the knock intensity which causes damage decreases as speed or combustion chamber temperature is increased. Other information obtained through analysis of the type of engine failure has suggested a way to increase compression ratio without changing octane requirement.

The importance of minimizing fuel consumption has necessitated the study of knock which drastically limits the attainment of high combustion efficiency in current s.i. engines. In the present work, four aspects of this phenomenon have been examined: 1. Knock intensity levels encountered during actual service operation of European cars. 2. Knock intensity levels that do not cause engine damage in endurance tests. 3. Factors affecting the knocking behavior of a fuel. 4. The meaning of the knock rating characteristics of a gasoline using the research and motor methods. It was found that the most severe knocking conditions were those met with by small displacement engines at a sufficiently high constant speed (4000-5000 rpm) and wide-open throttle. In these conditions, high knock intensities, much greater than the trace level, are needed to cause engine damage.

Carbonaceous material associated with potent carcinogens such as 3-4 benz(a)pyrene (BaP) and other polynuclear aromatic (PNA) hydrocarbons constitutes by far the greatest part of the particulate found in the exhaust gases of an internal combustion engine. The probable precursors of carbon particles are radicals formed in the incomplete combustion zone while their nucleation is made possible by ions originating in the flame. Ion current instantaneous values were measured by means of a modified Langmuir's probe, thus calculating thickness and speed of the flame in an engine cylinder. Relations between ion current and collected soot weight were examined. Fuel quality and additive influences over carbon and PNA formation were obtained.

Two main properties distinguish the structure of a turbulent flame from that of a laminar flame: ionization current of high intensity and high burning velocity. The first of these two quantities was directly measured in the combustion chamber of a typical European spark ignition engine by means of a Langmuir's probe, while the second was calculated starting from the pressure-time history measured with a piezoelectric transducer. The experimental results show the strong influence of the initial flame propagation on the type of the subsequent combustion during the rest of the cycle. The mathematical elaboration of the experimental data showed that the flame propagation mechanism is consistent with the hypothesis that turbulent combustion is caused by successive self-ignitions, as suggested by Russian authors.

The detection of cyclic dispersion, knocking, preignition, misfiring and other phenomena related with abnormal combustion in spark ignition engines has been extensively studied in the past. The transducers most commonly used detect pressure and/or ionization in the combustion chamber. By employing transducers that detect engine head movement it has been possible to examine these phenomena without particular engine modifications, thus enabling measurements to be made in commercial cars. These transducers are used in conjunction with electronic apparatus that gives quantitative measurements of the extent of the abnormal combustion. Results obtained by these means are reported with particular emphasis on high speed knock (a problem presently encountered with European cars), preignition and misfiring. On the basis of the test results a technique is developed utilizing the electron scanning microscope to recognize a posteriori if the piston failure is due to knock or preignition.