THE RELATIONSHIP BETWEEN GASOLINE COMPOSITION AND VEHICLE HYDROCARBONEMISSIONS - A REVIEW OF CURRENT STUDIES AND FUTURE-RESEARCH NEEDS

The purpose of this paper is to review current studies concerning the relationship of fuel composition to vehicle engine-out and tail-pipe e missions and to outline future research needed in this area. A number of recent combustion experiments and vehicle studies demonstrated that reformulated gasoline can reduce vehicle engine-out, tail-pipe, runni ng-loss, and evaporative emissions. Some of these studies were extende d to understand the fundamental relationships between fuel composition and emissions. To further establish these relationships, it was neces sary to develop advanced analytical methods for the qualitative and qu antitative analysis of hydrocarbons in fuels and vehicle emissions. Th e development of real-time techniques such as Fourier transform infrar ed spectroscopy, laser diode spectroscopy, and atmospheric pressure io nization mass spectrometry were useful in studying the transient behav ior of exhaust emissions under various engine operating conditions. la boratory studies using specific fuels and fuel blends were carried out using pulse flame combustors, single and multicylinder engines, and v ehicle fleets. Chemometric statistical methods were used to analyze th e large volumes of emissions data generated from these studies. Models were developed that were able to accurately predict tail-pipe emissio ns from fuel chemical and physical compositional data. Some of the pri mary fuel precursors for benzene, 1,3-butadiene, formaldehyde, acetald ehyde and C-2-C-4 alkene emissions are described. These studies demons trated that there is a strong relationship between gasoline compositio n and tail-pipe emissions.