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A methodology has been developed to enable a single, gaseous sample to be collected from the diluted exhaust stream of heavy duty diesel engines operating over the European 13 mode ECE R49 emission cycle. The sample consists of timed contributions of dilute exhaust gas from each mode (weighted appropriately) to provide a gas sample that is representative of the complete cycle. The sample is collected in a Tedlar bag prior to GC analysis for individual hydrocarbon speciation. This methodology has also been extended to allow for the collection of a representative carbonyl sample using 2,4-dinitrophenyl-hydrazine (2,4-DNPH) impregnated cartridges. Results obtained from these systems are reported and compared to results obtained from light duty (diesel and gasoline) investigations.

The schlieren method is a powerful and widely used technique for studying ignition and combustion. Jointly with high-speed photography, this method is often used in both SI- and CI-engines and combustion bombs, including rapid compression machines (rcm). This paper describes tests carried out on a new hydraulically actuated dynamic combustion rig, using schlieren visualisation in two orthogonal directions. The working principle of the rig is briefly described. Results are presented on ignition properties of low quality gas blends using spark ignition and pilot flame. Methane, ethane and nitrogen were blended at different air-fuel ratios and tested as to ignition and early flame development. For spark ignition tests, the pair of images from the two orthogonal directions enables the use of digital image processing to calculate the flame speed, and to compose a three-dimensional volumetric image of the flame front shape.

The effect of diesel fuel properties and composition on regulated emissions has been investigated in an IDI naturally aspirated passenger car equipped with an oxidation catalyst. The influence of diesel fuel changes on emissions from this same vehicle without the catalyst have been reported in a previous SAE paper (1).* The addition of the catalyst to this ‘clean’ car further reduced emissions, especially those of hydrocarbons and carbon monoxide. Particulate emissions were reduced to below the proposed 1996 European limit of 0.08 g/km. The catalyst was especially effective in reducing particulates from the higher density fuels, but had no influence on NOx. The catalyst was ‘sulphur tolerant’; changes in fuel sulphur content between 0.01 and 0.2% wt sulphur had a an insignificant effect on particulate emissions. Variations in fuel properties produced a significant influence on emissions, although the effect was less in this car, with a catalyst, than in the non-catalyst version.

The influence on regulated emissions of diesel fuel properties and composition has been investigated in an IDI passenger car fitted with EGR. The key findings were confirmed in limited tests on two other advanced technology European diesel passenger cars. This work is part of an on-going joint cooperative project involving Esso and Statoil. Tests on 37 fuels enabled the individual influence on emissions to be determined of fuel aromatics content, cetane quality, back end volatility (T95), density and sulphur content. This study reveals that the key fuel parameter influencing particulates in European diesel cars is density. In the typical European range of fuel densities (below 0.86 kg/l) there is a linear relationship between density and particulates. In this region T95 is also influential but increasing cetane number above 48 has negligible effect. Aromatics content is decisively shown to have no significant influence on particulates.