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Particulate matter in the air has become the focus of increased attention due to the concern of potential health effects. Among other sources, automotive vehicles are seen as a major contributor of fine particles. At present there is limited information available relating either to the number or size distribution of automotive particle emissions and detailed evidence has still to be established. To develop an understanding in the area of automotive particulate emissions a programme was carried out concentrating on tailpipe emissions as measured at the regulated particulate sampling point in a dilution tunnel. A previous literature study by CONCAWE had identified analytical techniques considered to be suitable for this application and which are capable of measuring both mass and number size distributions. Several variations of these techniques are available in the research field and the programme aimed to assess and compare their operation and performance.

While oxygen sensors provide the means by which changes in exhaust gas AFR (air-to-fuel ratio) are monitored and controlled in three-way catalyst systems, the chemistry of the exhaust gas in contact with this solid state electrochemical sensor can exert a substantial influence on its AFR control performance. Such interactions have been examined in a fundamental study on commercial oxygen sensors (unheated and heated), firstly using simple gas mixtures, and then simulated exhaust gas mixtures of progressively increasing complexity. The work confirms that diffusion effects at the sensor surface are centrally important in determining sensor response, but indicate that the effects of H2 (the smallest species present) do not necessarily dominate the observed behaviour. The results allow the development of a relationship that can be used to estimate the extent of the expected overall lean or rich shift for the sensor as a function of the exhaust gas composition.

A fuels matrix with aromatics and mid-range volatility (T50) independently varied was applied to 2 fleets (catalyst and non-catalyst) consisting of vehicles currently driven in Europe. For the catalyst fleet, reducing aromatics or T50 gave lower HC/CO. After catalyst light-off, decreasing aromatics gave more NOx sufficient to determine the direction of the composite cycle response. This is fully consistent with recent EPEFE results (future technology vehicles), confirming the general applicability of the EPEFE conclusions. Mostly, HC/CO responses from the non-catalyst fleet were directionally similar, though statistically less robust. However, at high volatility, reducing aromatics increased HC/CO. NOx was reduced by lowering aromatics and, to a lesser extent, mid-range volatility.

An acknowledged consequence of utilising oxygenates such as MTBE as a gasoline component is known to be a lowering of CO exhaust emissions from mature technology vehicles due to the “natural” leaning effect that the inclusion of MTBE can provide. A small decrease in THC is also commonly seen in these circumstances, while the effect of MTBE on NOx emissions is more variable and not usually beneficial. The present paper describes the results of recent studies in the European arena, covering the effects of fuel oxygenates (notably MTBE) on regulated emissions for non-catalyst and catalyst car fleets examined in in-house programmes. It looks at emissions effects according to the broad classification of the onboard vehicle technology employed. It further cites experimental work that has featured MTBE replacement in gasolines by a single saturated hydrocarbon (2,3-dimethyl butane) that is isoelectronic with MTBE. Some related work conducted concurrently on splashblending is also described.

This paper describes how the analytical methodology for fuels and exhaust gases was selected and developed for the experimental sectors of the EPEFE study. It covers the selection of standard test methods for fuels analysis and addresses how round-robin exercises in non-standard areas of fuels analysis were designed, organised, monitored and reviewed, and then used to define the approach to (and the scope of) the speciated fuel analyses. The paper also addresses how the exhaust gas analysis was designed in relation to emissions testing methodology. The means used to evaluate and, where necessary, optimise the exhaust gas speciation capabilities of participating laboratories, and in which round-robin activities were a key element, are also explained.

Following a small scouting programme to examine the scale of emissions benefits achievable by different degrees of gasoline base fuel redesign (SAE 930372), a larger programme has been initiated to investigate more systematically the influence of individual fuel parameters on tailpipe emissions. This coordinated study has been spread across five participating Shell Group laboratories, using a set of common fuels specifically designed and centrally blended for this purpose. Additionally, subsets of these fuels have been used for detailed systematic examination of selected topics within the overall programme scope. This paper summarises the plan for the integrated study. It describes the composition and properties of the fuels and their blending. The results covered here are those of chassis dynamometer-based regulated emissions studies conducted on a composite fleet designed to represent a range of vehicle technologies, using a variety of regulatory driving cycles.

As a first attempt to assess the scope for reducing the emissions from gasoline fuelled vehicles in the European market via fuel changes, an experimental scouting programme has been conducted to examine the effects of fuel composition and properties on both regulated emissions and detailed exhaust gas composition. This 4 fuels/4 vehicles programme involved exhaust emission tests on a chassis dynamometer, and was carried out mainly on non-catalyst vehicles, using two commercial gasolines and two (“reformulated”) test gasolines representing “intermediate” and “extreme” changes of the base gasoline design. The fuel characterization includes analysis by hydrocarbon type and carbon number; the exhaust analysis comprises both regulated emissions and hydrocarbon speciation measurements. In the case of regulated emissions, the fuel effects are, as expected, relatively small in comparison with the effect of installing exhaust catalysts.