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The effect of different fuel parameters on emissions is difficult to understand, the response depending upon different engine technologies. In addition the isolation of some of the fuel variables is often very hard. The present paper discusses the main results obtained testing a matrix of 14 fuels designed for obtain large variations of cetane number, sulphur and aromatic contents of Diesel oil. The aromatic structure of fuels and its effect on particulate emissions was also investigated. A linear regression analysis was performed in order to isolate the main controlling factors on particulate emissions. Finally the influence of aromatic contents of fuel on unregulated emissions was also assessed.

Unregulated emissions of polycyclic aromatic hydrocarbons (PAHs), carbonylic compounds, benzene and particulate matter (PM) were quantified in exhausts of a vehicle fleet representative of in use gasoline cars. Emission factors were obtained during both cold and hot start driving cycles (from urban to motorway driving conditions). Carbonylic compounds were sampled by DNPH cartridges and analyzed by HPLC. Benzene and other light hydrocarbons were collected in bags and then analyzed by GC-FID. PAHs were trapped in XAD-2 cartridges and then analyzed by GC-MS. PM was sampled by using the gravimetric procedure required for diesel cars. The effect of technology is significant with respect to regulated and unregulated emissions but different emissive behavior was found by varying the driving cycles. Cold start has a major influence on hydrocarbon emissions (included unregulated ones). This experimental work was carried out within the framework of the EU Artemis project.

The 1997 Kyoto International Conference Protocol committed industrialized countries to reduce their global emissions of greenhouse gases within the period 2008 2012 by at least 5% with respect to 1990. In view of this and following the European Community directives, the Italian government approved a three-year pilot project to promote the experimental employment of biodiesel. The methyl esters of vegetable oils, known as biodiesel are receiving increasing interest because of their low environmental impact and their potential as an alternative fuel for diesel engines as they would not require any significant modification of existing engines. Consequently, an experimental research program has been developed to evaluate performance and emissions of a Diesel engine fueled with a methyl ester derived from rape seed (Rapeseed Methyl Ester or RME) by changing the composition of the diesel fuel-RME mixture. This program aims to analyze the performance and emissions of a turbocharged D.I.

The attention on emissions of two-wheelers has been poor in the past, but today in countries with a large two-wheeler population it gives a significant contribution to aggregate emissions. In this paper the results obtained on a fleet composed by 22 two-stroke motorcycles (including mopeds) are presented. Sixteen in-use mopeds and six 125 cm3 motorcycles have been tested over ECE 47 and ECE 40 driving cycles respectively. Regulated emissions (CO, HC, NOx), carbon dioxide, benzene and fuel consumption have been evaluated by fueling motorcycles with two different gasoline formulations. One gasoline was a commercial Italian leaded gasoline with 1% benzene content; the other was a lower benzene and aromatics content gasoline. Benzene emissions decreased according to benzene content of gasoline.

The contribution to environmental pollution due to mopeds and motorcycles equipped with 2-stroke engines is very high. Then European regulations will impose in the next future severe limits on pollutant emissions of such vehicles. Up to 40% of the charge at high load and low speed can be lost during scavenging, therefore exhaust hydrocarbon speciation is similar to fuel composition, i.e. with a comparable content of benzene. The use of rich air-fuel mixtures, necessary to reduce cyclic variations and improve driveability during transients, determines also high carbon monoxide emissions. On the other hand NOx emissions are very low in all operating conditions, due to the rich mixtures and the high residual gas fraction. An effective solution to reduce emissions from current two-stroke engines for two wheelers in a short time could be retrofitting circulating vehicles with a catalyst for exhaust after-treatment.