The Effect of Fuel and Vehicle Variables on Polynuclear Aromatic Hydrocarbon and Phenol Emissions 720210
Exhaust emission of polynuclear aromatic hydrocarbons (PNA) and of phenols has been studied with a variety of test fuels, using cyclic tests in five vehicles-including one without emission control (NC), two with engine modification (EM) control, and two with experimental very low emission systems.
The experimental systems both reduced phenol emission to less than 0.5% and PNA emission to about 1% of the levels observed in the NC vehicle. Phenols were reduced 30% by one EM vehicle, but not by the other; while PNA emissions were reduced by 70% in both EM vehicles.
Fuel composition influenced emissions both directly and through engine deposits. Direct effects included increased phenol emission from increased fuel aromatics and, generally, increased PNA emission from increased fuel aromatics, from increased fuel PNA, and from the presence of a high-boiling naphtha. However, these direct effects of fuel composition on emissions generally decreased, in both relative and absolute terms, in the emission-controlled vehicles.
The PNA emissions from several test fuels differed by a factor of two between engine deposits formed from two different commercial premium gasolines. High PNA emissions occurred with deposits from a fuel containing lead and phosphorus; an unleaded fuel, of different hydrocarbon composition and without phosphorus, gave low emission deposits, but this same fuel, with lead added at 0.5 g/gal, still gave low emission. The exact fuel factors are not clear at this time.