Search Results

MAN and Shell have jointly investigated the effect of fuel properties on exhaust emissions from advanced engine technologies. MAN Nutzfahrzeuge AG, the Austrian subsidiary Steyr Nutzfahrzeuge AG and Deutsche Shell AG started this bilateral cooperation in 1990 with the objective of identifying key fuel properties that influence emissions from a MAN heavy-duty engine meeting the EURO-I legislation. The intention of that investigation was to determine the effect of cetane number, total and poly-aromatics content and backend distillation [T90] on particulates and gaseous emissions. In parallel both companies participated in the EPEFE (European Program on Emissions, Fuels and Engine Technologies) program which provided a broader understanding of fuel effects on emissions with different engine technologies under European test conditions.

The EPEFE study (European Programme on Emissions, Fuels and Engine Technologies), /1/ and other programmes have identified an increase in tailpipe NOx emissions with reduced gasoline aromatics content for modern 3-way controlled catalyst vehicles. This effect occurs with fully warmed-up catalyst under closed-loop operation. In order to understand the reasons for this effect VW and Shell have mechanistically investigated the effects of fuel properties on EMS (engine management system) and catalyst performance. Fuels with independent variation of oxygen, aromatics and mid-range volatility were tested in different VW engines. λ was monitored using sensors located both pre and post catalyst. The results confirmed that reducing gasoline aromatics content reduced engine-out emissions but increased tailpipe NOx emissions. It could be shown that differences in H/C ratio led to differences in the hydrogen content of engine-out emissions which affected the reading of the λ sensor.

As a result of increasing concerns over air quality, environmental legislation has led to more stringent emissions limits for diesel engines and vehicles. This has affected both engine manufactures and fuel suppliers. Whereas in the US, only the fuel requirements for heavy-duty diesel engines are of key interest, in Europe light-duty diesel applications are also important since diesel-powered passenger vehicles are accepted by customers and their market penetration has increased rapidly. This paper gives an update of Shell's ongoing research on correlations between diesel fuel quality and particulate emissions in both heavy- and light-duty applications. In heavy-duty testing (both steady-state and transient), sulphur is the dominant fuel property affecting particulate emissions. After sulphur correction, fuel effects are small and can best be described by a combination of cetane number and density.

In a cooperative programme between BMW and Shell, the effects of gasoline properties and composition on regulated emissions (HC, CO, NOx), CO2, fuel consumption and catalyst performance have been studied. The objective of the test programme was to investigate the effect of different hydrocarbon groups from typical refinery streams on exhaust emissions with a detailed analysis not only of the tailpipe emissions but also engine out emissions and catalyst performance. In total thirteen fuels with widely varying physical properties and chemical composition were evaluated in a 1991 series production BMW 525i, and a subset of three of these fuels in two other BMW models to verify their sensitivity to fuel quality. The results for the BMW 525i showed that significant reductions in HC, CO and NOx emissions were seen for fuels containing splashblended oxygenates and with aromatics replaced by isoparaffins.

Shell companies* and Mercedes-Benz have investigated the effect of diesel fuel properties on exhaust emissions in an advanced European IDI passenger car and a modern commercial vehicle DI engine. The experimental programme identified the key fuel properties that influence diesel engine emissions with specific emphasis on NOX and particulates emissions. The fuel properties investigated were density, sulphur, distillation range, cetane number, mono aromatics and polyaromatics content. With regards to the polyaromatics content, the fuels were not designed to differentiate between the effect of di- and tri+ -aromatics. It is concluded that the fuel properties which account for the observed fuel effects on particulates emissions are sulphur, density and polyaromatics content. Monoaromatics content, cetane number and the distillation, as described by T10E, T50E and T90E, were found to have no effect on particulates emissions.

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.